a spectrum of potentially diamondiferous lamproites and minettes from the jharia coalfield eastern india abstract abundant cretaceous 110 ma lamprophyric sills in the gondwana coalfields show a comagmatic continuum from olivine lamproites to lamproites and minettes four sills in the jharia coalfield have exotic mineralogy dominated by olivine fo 85 92 and phlogopite 5 10 tio 2 5 13 al 2 o 3 with subordinate potassium titanian richterite and or arfvedsonite and spectacularly zoned sr rich apatite up to 20 sro accessory to minor phases include clinopyroxene titanian diopside to aegirine augite k feldspar or 96 variable spinel up to 47 cr 2 o 3 perovskite niobian ilmenite niobian rutile sphene and ba poor priderite complex primary carbonate assemblages involve breunnerite ferroan dolomite witherite alstonite and strontianite the whole rocks show low al 2 o 3 5 7 combined with high k 2 o 4 5 mgo up to 30 and cr up to 1500 ppm plus extreme tio 2 up to 8 5 sr zr up to 6000 ppm each ba up to 8000 ppm and lree ce up to 3000 ppm in many rocks k al molecular 0 7 na k al 1 and k na k 0 6 radiogenic isotopes sr 7 to 21 and nd 1 5 to 3 1 imply derivation from a metasomatized lithosphere mantle source with time integrated rb sr and sm nd slightly higher than bulk earth intensive carbonation up to 14 co 2 in some rocks may reflect fluids derived from the magmas themselves from carbonatite like fluids and perhaps from coking of the invaded coal seams minor crystal fractionation within sills as little as 2 5 m thick has yielded complementary olivine lamproites and feldspathic lamproites the latter grade ultimately into minettes via increase of al 2 o 3 and decrease of mgo positive indicators of diamond potential in these rocks include their bulk compositional similarity to diamondiferous olivine lamproites elsewhere e g argyle their cr rich spinels and perhaps their tectonic position negative factors include their quiet emplacement the noted differentiation and the associated coking of the coal seams

age of emplacement of the schistes lustres nappe alpine corsica abstract structural studies in the schistes lustres nappe west of bastia corsica demonstrate the existence of a tectonic melange in which km scale blocks and smaller lozenges of basement granite gneiss thick layered marble and dismembered mesozoic ophiolite are enveloped in a matrix of calc schist and blueschist the main s1 foliation is developed in both block and matrix and is concordant with lithologie contacts blueschist facies metamorphism was syn kinematic with the main foliation the s1 in the schistes lustres was refolded about ene wsw trending tight similar and monoclinal fold axes f2 these second folds verge to the southeast and show km scale axial culminations and depressions that are reflected by topography and residual bouguer gravity anomalies parautochthonous hercynian basement tenda corte complex beneath the western edge of the schistes lustres nappe contains a mylonitic foliation which is concordant with the main foliation in the schistes lustres the intensity of deformation in the basement decreases away from this contact and undeformed granites are found 3 km to the west whole rock samples of the deformed basement immediately beneath the schistes lustres yield an rb sr isochron diagram n 4 which has an age of 105 8 ma 1 and initial 87 sr 86 sr ratio of 0 7228 0 0005 1 this result is more precise than our preliminary age and initial ratio estimate of 98 14 and 0 7296 0 0068 respectively cohen et al 1979 it is similar to a recently published mid cretaceous 90 ma 40ar 39ar age from glaucophane mineral separates we interpret this date as the age of a metamorphic overprint related to the emplacement of the schistes lustres nappe and associated ophiolites the formation of the main foliation and blueschist facies metamorphism these results indicate that the mid cretaceous blueschist facies metamorphism documented in the western alps formerly extended farther south of its present terminus the data are consistent with mid cretaceous obduction of tethyan oceanic crust onto the present day eastern continental margin of corsica we postulate that during eocene early oligocene time a polarity flip occurred outboard of the obducted crust and a new southfacing subduction zone developed this change in polarity was responsible for the development of southeast vergent second folds and for the resetting of 40ar 39ar and k ar geochronologic clocks described in the literature

a new detrital mica 40ar 39ar dating approach for provenance and exhumation of the eastern alps detrital thermochronology can be used as a tool to quantitatively constrain exhumation rates and its spatial variability from active mountain belts commonly used methods for this purpose assume a steady state relationship between tectonic uplift and erosion however this assumption does not account for the transitory response of a dynamic orogenic system to changes in the boundary conditions we propose a different approach that uses the observed detrital age distributions as markers of the past exhumation and of the present day erosion and mixing occurring in a river system in this paper we present new 40ar 39ar biotite and white mica age distributions for 19 modern river sands from the eastern alps north of the periadriatic line the results present three main clusters of ages at 0 5 50 60 120 and 250 350 ma that record the main orogenic phases in this sector of the alps we have applied two numerical methods to the cooling ages to a linearly compute the spatial variability of the relative present day erosion of a set of four detrital mineral samples from drainage basins along the inn river and b quantify the rates of the cooling and erosion in the tauern window during paleocene miocene time of the alpine orogeny our results suggest a 0 34 0 84 mm yr range of exhumation rates for the tauern window since the miocene our estimates of exhumation rates of the western tauern window are higher than those for the eastern tauern window which is consistent with the previous studies

geology mineralogy and chemistry of lateritic nickel cobalt deposits near kalgoorlie western australia in the kalgoorlie area of western australia significant deposits of ni co laterite are developed on large ultramafic complexes at siberia and bulong the ultramafic rocks form part of extensive archean greenstone belts in the granitoid terrain of the southeastern yilgarn block and were lateritized during late cretaceous to early tertiary times the laterite profile developed over serpentinized dunite and peridotite is divided into four zones on the basis of morphology mineralogy and chemical composition in the oxidized bedrock zone ni rich saprolitic serpentine and smectite are developed in joints and fractures in the bedrock the overlying saprolite zone consists predominantly of saprolitic serpentine and may retain bedrock structures and textures it is characterized by a decrease of mg and an increase in ni upward a well defined clay zone is commonly developed over the bulong saprolite zone the clay zone is composed essentially of nontronite and quartz and commonly contains ni values of 1 to 2 percent the limohire zone occurs at the top of the profile and may consist of an upper hematite rich section and a lower goethite rich section the limonite zone is rich in fe al and cr and is formed by residual concentration of stable oxides a concentration of mn oxides commonly containing high co and ni grades occurs at the base of the limonite zone where sufficiently thick co and ni rich mn concentrations have been mined for direct smelter feed to augment co and ni production from kambalda ni sulfides physical and chemical characteristics of the underlying bed rock are important controls on the distribution of ni and co accumulations the mode of occurrence of ni and the presence of co are significant factors in the economics of exploiting these deposits

geochemical investigation of soils developed in different lithologies in bhutan eastern himalayas within a project studying soil genesis on the southern slopes of the eastern himalayas a comprehensive set of major trace and rare earth element ree contents has been compiled for the first time six saprolites and their associated pedons were sampled on metamorphic migmatitic and leucogranitic parent materials at altitudes ranging from 1520 m to 3770 m metamorphic soils are largely illitic with si decreasing and al and fe increasing with decreasing degree of metamorphism the subsoil of a tourmaline bearing leucogranite is characterised by equally high si but higher contents of k and lower fe mg and ti a migmatitic profile in southern bhutan is dominated by hornblende and is quite distinct from the other lithologies with lower contents of si and k but higher fe mg ca and mn chondrite normalised ree patterns compare with post archaean materials with steep light rare earth lree and flat heavy rare earth hree patterns in comparison to generalised upper crustal composition ucc the bhutanese lithologies show a pronounced eu anomaly whereas the patterns appear rather homogenised in topsoils the influence of the parent materials causes deviations from the general trend with increasing depth the occurrence of marine tethyan sediments is confirmed by a strong positive ce anomaly in the central bhutanese phobjikha valley in the leucogranitic profile ree depletion is attributed to the presence of monazite as corroborated by trace element behaviour because of the hornblende ree patterns of the migmatitic profile are flat and without a eu anomaly chemical indices of alteration cia of between 71 and 92 indicate advanced weathering even at high altitudes correlation analyses show that ree are associated with the silt and clay fraction 63 m at elevations above approximately 3500 m physical weathering causes passive ree enrichment however no differentiation of ree concentrations or patterns within the profile is observed below 3500 m increased chemical weathering and leaching appears to be sufficient to release and translocate rees in this process hree are preferentially translocated whereas ce is more refractory than the other lanthanides this case study confirms that soil weathering and ree behaviour are closely related

the maritime alps arc in the ligurian and tyrrhenian systems abstract after late eocene meso alpine collision between the european and adria plates the maritime alps underwent further deformations linked to the apennine orogenesis and consistent with a stress field developed during anticlockwise rotation the western limit of the rotated sector is east of the argentera massif and to the southwest represents the northwestern margin of the post eocene ligurian sphenochasm the sinistral rotation of the maritime alps initially occurred contemporaneous with the opening of the ligurian basin about 30 19 ma and probably continued during the subsequent opening of the tyrrhenian basin about 10 0 ma the rotating block comprises the northwestern part of the adria indenter and a part of the paleo european plate namely the maritime alps corsica and sardinia if a convenient configuration is assumed for the moho of the adria margin and suitable poles are chosen for subsequent rotations then a simplified model of rigid body can explain the rotation structures in the maritime alps the apennines and po plain subsurface compressional arcs the late foreland directed transport of nappes in the western alps the presence of extensional and dextral transcurrent structures and the general uplift of the lithospheric mantle between the ligurian sea and the ivrea body as to the causes of rotation two alternatives subduction or asthenosphere uplift are discussed chronological and mechanical arguments seem to favour the latter

the interpretation of 40ar 39ar apparent age spectra produced by mixing application of the method of asymptotes and limits abstract a method is presented for the analysis and interpretation of apparent age spectra produced during 40 ar 39 ar step heating experiments application of this method is particularly relevant to complex apparent age spectra produced from minerals taken from exhumed metamorphic tectonites particularly when these rocks once resided in an ancient argon partial retention zone such rocks may have been subject to localised deformation and or recrystallisation during orogenesis yet microstructures relict of earlier episodes of deformation and or metamorphism may retain relatively old apparent ages as a result complex apparent age spectra can be produced during a conventional step heating experiment and these age spectra often cannot be simply interpreted the recognition and the interpretation of a plateau in such spectra is sometimes uncertain and in any case the definition of a plateau is then a concept of limited theoretical validity to avoid these difficulties an alternative strategy is presented based on a theory of mixing gas from different microstructural microchemical reservoirs this method relies on the definition of asymptotes and limits in sequences of apparent ages in apparent age spectra obtained from step heating experiments frequently measured ages fmas in individual datasets can then be recognized using statistical analysis the significance of fmas must be independently assessed

the impact of redox conditions on the rare earth element signature of redoximorphic features in a soil sequence developed from limestone abstract redox processes which are widespread in soils need to be quantified for an improved comprehension of the dynamics of fe and mn oxides and their associated trace elements the classical methodology used to study these redox processes generally relies on the quantification of all mineral species in the various pedological features that can be related to different redox stages however this approach usually encounters the difficulty of precisely quantifying the different forms of poorly crystallised fe and mn oxides in this study we use the signature of rare earth elements rees to visualise and eventually quantify the importance of redox processes in soils our approach relies on that developed by laveuf et al 2008 and the idea that the relative contribution to the mobilisation of rees that is made by the primary minerals reactive to redox conditions depends on the following factors i their initial proportion in the different pedological features that can be related to various redox processes ii their relative mobilisation during the redox process in question and iii their initial ree signatures the catena studied is characterised by two stages of redox conditions the first is related to the formation and subsequent dissolution of fe mn concretions and the second is related to the bleaching of the soil matrix due to morphological degradation in this soil the main minerals reactive to redox conditions are mn oxides ferrihydrite goethite and fluor apatite the results indicate that the primary redox conditions can be characterised by a positive ce anomaly on the ree pattern which has been attributed to a preferential immobilisation of this element due to its association with mn oxides the results also indicate that the secondary redox conditions can be characterised by depletion in medium rees mrees in the ree pattern which has been attributed to a preferential release of these elements during the dissolution of fluor apatite and to a lesser extent of ferrihydrite these results emphasise the potential of ree signatures of the visualisation of the various redox processes that have been active in a soil additionally ree signatures are a proxy of the frequency and intensity of the redox conditions

rare earth elements and clay minerals of soils of the floodplains of three major rivers in bangladesh the rare earth elements ree particle size distribution and mineralogical composition in the 2 m clay fraction from the soils on the floodplains developed by the three major rivers of the brahmaputra meghna and ganges in bangladesh were analyzed ree as the chondrite normalized curve or the plot of ce eu against eu sm did not differentiate the soils according to the river floodplains whereas the clay mineralogy did particle size distribution varied between the soils and the soil horizons

trace and rare earth element content of white clay soils of the three river plain heilongjiang province p r china abstract three representative pedons of white clay soils in the three river plain heilongjiang province p r china were sampled to establish background levels of trace elements and rare earth elements ree and to evaluate pedogenic redistribution of these elements trace elements and ree in soil samples and clay separates were measured by instrumental neutron activation analysis new information was obtained for the background levels and pedogenic behavior of 20 trace elements and 10 ree cl br i and hg were enriched in the ah horizon elements having an adsorption affinity for mn and fe oxyhydroxides as co and mn were concentrated in the e horizon elements associated with clay minerals cr rb v and zn were elevated in soil samples from the illuvial horizon while elements present in resistant minerals sr ti hf and zr had relatively uniform profile distributions possible chemical causes of the trace element redistribution and partitioning are also discussed in the paper ree were enriched in clay fractions compared to whole soil ce positive anomalies seen in normalized curves of ree for the e horizon were attributed to precipitation and accumulation of the element in pedogenic fe mn nodules the gd break even odd and tetrad effects were present in normalized curves which indicates fractionation of ree during weathering the high ratio of light ree sum la to heavy ree sum lu for the soil can be attributed to a warm humid geochemical weathering environment in the past

sedimentation in the northern apennines corsica tectonic knot northern tyrrhenian sea central mediterranean offshore drilling data from the elba pianosa ridge the northern tyrrhenian sea is located on the collisional zone between the alpine corsica and the northern apennines and is a key area for gaining a better understanding of the complex relationships between these two systems the knowledge of the wide offshore part of this zone located between corsica france and mainland italy is based primarily on the analysis of several seismic profiles tied to the outcropping geology and unpublished preliminary reports of few offshore wells the here presented study of two offshore wells provides a revision of the sedimentology biostratigraphy and petrography of the thick mainly siliciclastic tertiary successions about 3 600 m composing the elba pianosa ridge epr a structural morphological high separating the tuscan shelf to the east from the corsica basin to the west a comparison with similar deposits cropping out in the surrounding onshore areas northern apennines corsica tuscan archipelago piedmont tertiary basin provides additional constraints for refinement of the complex geodynamic and regional setting in which the epr evolved

provenance of oligocene synorogenic sediments of the ligurian alps nw italy inferences on belt age and cooling history mineral chemistry 40ar 39ar geochronology on white micas and apatite fission track thermochronology aftt are applied here to study the provenance of the synorogenic molare formation lowermost unit of the tertiary piedmont basin clastic sequence the molare formation was deposited during transgression onto the ligurian alps nappe stack in the early oligocene depositional facies show that clastic distribution remained transversal with local sources located just landward from the coastline phengite mineral chemistry together with 40ar 39ar data clearly shows two distinctive source areas each one mirroring the composition of the basement directly beneath the clastic sequence amphibole mineral chemistry allows second order provenance distinctions within each sector reflecting heterogeneous metamorphic evolution of the bedrock complexes integrated 40ar 39ar dating and aftt suggest that following a fast cooling exhumation episode of the ligurian alps during the oligocene very little net uplift has since occurred this is due to a period of general subsidence from the oligocene late miocene followed by comparable uplift from late miocene pliocene to the present in general our data provide an image of the ligurian alps during the oligocene which is very similar to the present day one

an empirical evaluation of the argon diffusion geometry in muscovite the temperature time significance of 40ar 39ar muscovite ages is difficult to evaluate quantitatively because of ambiguities in the choice of an appropriate model diffusion geometry the effective diffusion dimension and large uncertainties in experimentally determined diffusion parameters laser 40ar 39ar studies of natural 40ar concentration gradients suggest that argon loss in muscovite occurs primarily via cylindrical volume diffusion commonly with an effective diffusion dimension equal to the crystal diameter the present study tests the cylinder model geometry and the control of physical grain size on the effective diffusion dimension by measuring the anisotropy of a natural40ar diffusion gradient parallel and perpendicular to 001 in a single euhedral muscovite phenocryst the new data combined with previous studies clearly indicate loss of 40ar via cylindrical volume diffusion and strongly suggest that loss of 40ar across the 001 sheets slab diffusion geometry is minimal in undeformed crystals

macrostructural and microstructural architecture of the karakoram fault relationship between magmatism and strike slip faulting a key factor in interpreting the significance of large scale strike slip faults in models of continental deformation is an understanding of the temporal relationship between faulting and magmatism knowledge of when a strike slip fault initiated is essential in order to determine its long term slip rate and its significance in accommodating strain we review key structural criteria that identify whether magmatism is prekinematic or synkinematic with faulting and apply these criteria to a major tibet bounding strike slip fault along the karakoram fault in western tibet opinion is divided between 1 those advocating that magmatism and shearing were coeval in which case the youngest u pb crystallization age provides a minimum age of shear and 2 those advocating that magmatism preceded strike slip shearing in which case the youngest u pb crystallization age provides a maximum age of shear fault zone rocks within the central segment of the fault are variably deformed displaying high to low temperature solid state fabrics mylonites indicate subsolidus noncoaxial deformation at temperatures that have not exceeded greenschist lower amphibolite facies there is no evidence for submagmatic deformation and there are no textural or structural indicators that suggest synkinematic magmatism consequently magmatism preceded shearing suggesting that the u pb age of proximal leucogranites sets a maximum age for shear coupled with a limited offset 150 km these data confirm a low long term slip rate for the karakoram fault 3 10 mm yr consequently the fault is unlikely to have played a significant role in accommodating strain during the indo asian collision and thus its role in suggested extrusion models of deformation is limited

and mg fe si al2 compositional control on argon behaviour in high pressure white micas a continuous laser probe study from the dora maira nappe of the internal western alps italy abstract high pressure white micas from a restricted area in the dora maira nappe of the western alps italy were analyzed by the conventional 40 ar 39 ar bulk sample step heating method and by the step heating and the spot fusion 40 ar 39 ar continuous laser probe techniques on single grains high si ferich phengites from fine grained gneisses display homogeneous 35 40 ma plateau and spot fusion ages consistent with the upper eocene 40 ar 39 ar phengite ages documented over the whole internal western alps in contrast phengite separates and single grains of high si and mg rich to intermediate composition selected from metapelitic and mg rich mica schist samples yield older discordant apparent ages even when sampled in the same outcrop as the fine grained gneisses these local age variations are interpreted to reflect primarily an increasing ar retentivity with increasing mg content in phengites in metapelite derived white micas the isotopic discordance is marked by 1 1 a characteristic bulk sample upward convex spectrum shape 2 2 single grain disturbed age spectra 3 3 a systematic radially outward decrease in spot ages across individual mica cleavage planes and 4 4 strong grain to grain spot age variations in rock sections 1 1 in mg rich mica schists the isotopic discordance is observed as a reproducible upward convex bulk sample age spectrum with high 140 ma intermediate apparent ages 2 2 upward convex single grain age spectra and 3 3 irregular intra and intergrain age gradients on geochemical grounds it is argued that the isotopic discordance occurring in the metapelites is mainly controlled by the compositional changes introduced by the mg fe si al2 celadonitic re equilibration of the high pressure phengites during greenschist overprinting in mg rich phengites this chemical re equilibration may induce ar loss below their presumed higher blocking temperature a model of ar behaviour in high pressure white micas is proposed which explains the age variations recorded throughout the different lithologies in terms of a simple interaction between the mg fe compositional control on ar retentivity and the mg fe si al2 modifications occurring in phengites during progressive overprinting

40ar 39ar dating of white micas from an alpine high pressure metamorphic belt on naxos greece the resetting of the argon isotopic system overprinting of white micas from high pressure low to medium temperature m1 metamorphic assemblages in pelitic schists on naxos during subsequent thermal dome m2 metamorphism ranges from minor in the southeast of the island to complete recrystallization in the amphibolite facies rocks near the migmatites in the centre of the dome the original m1 minerals are phengites si4 6 7 7 0 and the overprinting minerals are muscovites si4 6 0 6 45 40ar 39ar step heating analyses of white mica separates from rocks in the area where phengite and muscovite occur together yield complex age spectra characterized by low apparent ages in the first and the last stages of gas release and high apparent ages in between these upward convex age spectra are shown to be caused by mixing of two generations of micas each of which has a different age spectrum and argon release pattern seemingly good plateaus in some age spectra from white micas of the area must be interpreted as providing meaningless intermediate ages further the upward convex age spectra have been used to trace the isotopic signature of phengites toward increasing m2 metamorphic grade and suggest that as long as phengites can be observed in the rocks upward convex age spectra occur on naxos crystallization of muscovite at the expense of phengite appears to be the main mechanism of resetting argon isotopic ages in white micas however there is also good evidence for argon loss by volume diffusion from phengites simple diffusion calculations suggest that the m2 metamorphism was caused by a shortlived heat source

tracing exhumation and orogenic wedge dynamics in the european alps with detrital thermochronology detrital cooling ages from the pro foreland and retro foreland basins of the european alps record distinctive exhumation trends that correlate with orogenic wedge states inferred from thrust front propagation rates periods of rapid hinterland exhumation correlate with relatively slow propagation of deformation toward the foreland and are interpreted to represent subcritical wedge conditions whereas periods of slow hinterland exhumation correlate with rapid propagation of deformation toward the foreland and indicate supercritical wedge conditions similar lag time trends recorded in both the pro foreland and retro foreland thus mimic orogenic wedge behavior and suggest that local tectonics and or climate events do not overprint the regional signal

oligocene early miocene tectonic evolution of the northern apennines northwestern italy traced through provenance of piggy back basin fill successions

from source terrains of the eastern alps to the molasse basin detrital record of non steady state exhumation fission track cooling ages of detrital apatite aft in the east alpine molasse basin display age groups corresponding to geodynamic events in the orogen since jurassic times these age groups are typical of certain thermotectonic units which formed a patchwork in the swiss and eastern alps by a combination of petrographic and thermochronologic data progressive erosion of source terrains is monitored in different catchments since the oligocene the aft cooling ages show a decrease in lag time until when rapidly cooled debris derived from tectonically exhumed core complexes became exposed after termination of tectonic exhumation lag times of debris derived from the core complexes increased neither on the scale of the entire eastern alps or on the scale of individual catchments steady state exhumation is observed due to the highly dynamic changes of exhumation rates since late eocene collision d 2005 elsevier b v all rights reserved

excess argon in k ar and ar ar geochronology the k ar and ar ar dating techniques occasionally produce anomalously old ages attributed to excess argon and such data is often rejected as not offering any insight into the age thermal history or geochemistry of the rock however improvements in the quantification of argon geochemistry now provide a framework to model excess argon in both open and closed systems solubility data for argon in hydrous fluids melts and emerging data for minerals can be used to understand the behaviour of excess argon and provide valuable insights into the environment in which the samples cooled to their argon retention or closure temperature treating excess argon as a trace element also throws light on its behaviour in minerals above the closure temperature in deeply buried dry systems such as eclogites blueschists granulites and even in the lithospheric mantle extremely low partition coefficients between k feldspar and hydrous fluid phases predict lower excess argon susceptibility than micas and this is observed in fluid poor systems variation of partition coefficients can lead to excess argon in fluids being introduced into minerals or removed from minerals as grain boundary fluids change during flow through a rock however excess argon can also be introduced or removed from minerals by varying temperature without the need for fluid flow high mineral melt and mineral fluid partition coefficients are also the reason why excess argon is often concentrated in inclusions within minerals partition coefficients between minerals and hydrous fluids as low as 10 6 lead fluid inclusions to dominate the radiogenic argon budget particularly in low potassium minerals melt inclusions are less dominant but become critical in dating younger samples

middle eocene to early miocene sedimentary evolution of the western lombardian segment of the south alpine foredeep italy the main steps of the sedimentary evolution of the west lombardian south alpine foredeep between the eocene and the early miocene are described the oldest is a bartonian carbonate decrease in hemipelagic sediments linked with an increase in terrigenous input possibly related to a rainfall increase in the alps between the middle eocene and the early chattian a volcanoclastic input is associated with an extensional tectonic regime coeval with magma emplacement in the southern central alps and with volcanogenic deposits of the european foredeep and apennines suggesting a regional extensional tectonic phase leading to the ascent of magma during late eocene to early oligocene two periods of coarse clastic sedimentation occurred probably controlled by eustasy the first during late eocene fed by a local south alpine source the second earliest oligocene in age supplied by the central alps in the chattian a strong increase in coarse supply records the massive erosion of central alps coupled with a structures growth phase in the subsurface it was followed by an aquitanian rearrangement of the alpine drainage systems suggested by both petrography of clastic sediments and retreat of depositional systems while subsurface sheet like geometry of aquitanian turbidites marks a strong decrease in tectonic activity

major asian aeolian inputs indicated by the mineralogy of aerosols and sediments in the western north pacific recent atmospheric chemistry studies have shown that substantial quantities of soil material are being transported out of asia and across large regions of the north pacific1 2 in the central north pacific the estimated1 6 12 1012 g yr 1 and measured2 20 1012 g yr 1 deposition rate of mineral aerosols could account for a substantial fraction of the non biogenic portion of deep sea sediments in this region where sedimentologists have previously estimated that 75 95 3 4 of the surface sediment is derived from atmospheric dust fallout the quantitative importance of wind transported aeolian material to sedimentation in the north pacific would be more firmly established if it could be shown that the composition of the present day soil aerosol is similar to that of mineral particles in the underlying sediments which have been deposited over a period of thousands of years here we compare the compositions of soil aerosols and sediments collected from the western north pacific and find that their mineralogies are identical except for one mineral this supports the hypothesis that the sediments are heavily impacted by aeolian sources

pedogenic properties of white clay soils of the three river plain heilongj iang province p r china abstract white clay soils are widely distributed in the heilongjiang province p r china and are of agricultural importance in the province however there is only limited information available on the characteristics and pedogenesis of these soils three representative pedons of white clay soils in the three river plain heilongjiang province were selected to determine physical morphological chemical and mineralogical properties and to relate these properties to the genesis and classification of these soils sr ti and zr were determined by x ray fluorescence to establish parent material uniformity clay minerals were identified by x ray diffraction methods micromorphology of the soils was based on petrographic examination of thin sections lithologic discontinuities were not detected based on the coefficients of variability associated with ratios of zr sr and ti zr within pedons the profiles are characterized by a mollic epipedon an albic e horizon and a thick argillic horizon physical morphological chemical and mineralogical properties indicate that lessivage was a dominant pedogenic process pedogenic fe mn nodules occur in ah and e horizons maximum contents of pyrophosphate extractable fe and al and oxalate and dithionite extractable al occur in bt2 horizons the soils have relatively uniform ph values of about 4 5 5 0 soil vermiculite which had not previously been recognized is common in the clay fraction the clay mineral assemblage is qualitatively similar throughout profiles continuous addition of aerosolic dust rich in mica and lessivage contributed to the quantitative variation in clay minerals within the pedon the white clay soils are classified as mollic planosols in the fao unesco system and typic argialbolls in soil taxonomy

inherited argon in a pleistocene andesite lava 40ar 39ar incremental heating and laser fusion analyses of plagioclase by using 40 ar 39 ar incremental heating and laser fusion techniques xenocrystic plagioclase was discovered in a late pleistocene andesitic lava that erupted through the andean cordillera inherited argon in the xenocrysts is as much as 450 times older than the host lava the age of which is independently known and is an obstacle to dating the lava by using a whole rock sample the xenocrysts are impossible to identify from petrography or chemical parameters such as their k ca ratios holocrystalline groundmass carefully separated from plagioclase and other phenocrysts gives an accurate 40 ar 39 ar age for the lava the xenocrysts could not have been degassed for more than several days in the magma and probably were assimilated from paleozoic rocks buried under kilometers of mesozoic and tertiary arc rocks composing the cordillera in central chile the required magma ascent velocity on the order of kilometers day is extraordinarily high compared to the 10 4 km day minimum implied by the 226 ra excess in continental arc lavas these data permit magma migration and storage in the mantle and lower crust for as much as thousands of years followed abruptly by rapid ascent to the surface

geochemical and mineralogical characteristics of ion adsorption type ree mineralization in phuket thailand geochemical and mineralogical studies were conducted on the 12 m thick weathering profile of the kata beach granite in phuket thailand in order to reveal the transport and adsorption of rare earth elements ree related to the ion adsorption type mineralization the parent rock is ilmenite series biotite granite with transitional characteristics from i type to s type abundant in ree 592 ppm ree are contained dominantly in fluorocarbonate as well as in allanite titanite apatite and zircon the chondrite normalized ree pattern of the parent granite indicates enrichment of lree relative to hree and no significant ce anomaly the upper part of the weathering profile from the surface to 4 5 m depth is mostly characterized by positive ce anomaly showing lower ree contents ranging from 174 to 548 ppm and lower percentages of adsorbed ree from 34 to 68 compared with the parent granite in contrast the lower part of the profile from 4 5 to 12 m depth is characterized by negative ce anomaly showing higher ree contents ranging from 578 to 1 084 ppm and higher percentages from 53 to 85 the negative ce anomaly and enrichment of ree in the lower part of the profile suggest that acidic soil water in an oxidizing condition in the upper part mostly immobilized ce4 as ceo2 and transported ree3 downward to the lower part of the profile the transported ree3 were adsorbed onto weathering products or distributed to secondary minerals such as rhabdophane the immobilization of ree results from the increase of ph due to the contact with higher ph groundwater since the majority of ree in the weathered granite are present in the ion adsorption fraction with negative ce anomaly the percentages of adsorbed ree are positively correlated with the whole rock negative ce anomaly the result of this study suggests that the ion adsorption type ree mineralization is identified by the occurrence of easily soluble ree fluorocarbonate and whole rock negative ce anomaly of weathered granite although fractionation of ree in weathered granite is controlled by the occurrence of ree bearing minerals and adsorption by weathering products the ion adsorption fraction tends to be enriched in lree relative to weathered granite

subduction polarity reversal at the junction between the western alps and the northern apennines italy abstract the controversial relationship between the orogenic segments of the western alps and the northern apennines is here explored integrating recently published 3d tomographic models of subduction with new and re interpreted geological observations from the eclogitic domain of the voltri massif ligurian alps italy where the two belts joint each other the voltri massif is here described as an extensional domain accommodating the opposing outward migration of the alpine and apennine thrust fronts since about 30 35 ma using tomographic images of the upper mantle and paleotectonic reconstructions we propose that this extensional setting represents the surface manifestation of an along strike change in polarity of the subducted oceanic slab whose polarity changed laterally in space and in time our tectonic model suggests that the westward shift of the alpine thrust front from the oligocene onward was the consequence of the toroidal asthenospheric flow induced by the retreat of the apenninic slab

the early stages of the alpine collision an image derived from the upper eocene lower oligocene record in the alps apennines junction area the upper eocene lower oligocene sediments deposited in the eastern part of the tertiary piedmont basin in northern italy provide a complete record of the unroofing of the alpine orogenic prism during the early stages of exhumation in the ligurian sector from late priabonian till late rupelian time the sediments in the study area were derived from two different sources one characterised by white micas with sib6 5 pfu and permian 40 ar 39 ar ages 270 ma and the other characterised by white micas with sin7 pfu and eocene oligocene 40 ar 39 ar ages 32 50 ma the first source is considered to be indicative of low pressure metamorphic rocks that covered the hp rocks of the ligurian alps and were completely eroded by chattian time from this time on the study area started to record the first input from western alpine sources characterised by a larger span of ages with a more frequent eoalpine signal thus sediments deposited in the eastern part of the tertiary piedmont basin contain the only available evidence of rocks belonging to high crustal levels in the alpine orogenic prism that were not affected by the alpine overprint these data also provide time constraints to the poorly dated first conglomerates deposited in this area 40 ar 39 ar geochronology reveals a minimum age of 33f1 4 ma for the pianfolco conglomerates in the type locality and of 31 4f3 5 ma for the borbera conglomerates d 2004 elsevier b v all rights reserved

formation mechanisms of secondary hydrocarbon pools in the triassic reservoirs in the northern tarim basin abstract the northern tarim basin tabei is a rich composite hydrocarbon accumulation region with multi layers of oil and gas reservoirs in the ordovician carboniferous and triassic strata in the triassic the tabei region was dominated by non marine sedimentation that developed deltaic sandstone reservoirs with favourable petrophysical properties for hydrocarbon accumulations hydrocarbons in the triassic hydrocarbon pools are dominated by oil and condensate gas analysis of the hydrocarbons in combination with well testing and drilling data reveals that oils in the triassic hydrocarbon pools are commonly biodegraded and originated mainly from the middle upper ordovician source rocks the predominant dry gases in the reservoirs are cracked from oils derived from the cambrian source rocks the origin of hydrocarbons in the triassic pools is similar to those in the underlying reservoirs fluid inclusions and k ar dating confirm that the hydrocarbons were accumulated during the himalayan orogenic movement because the middle upper ordovician source rocks already experienced peak hydrocarbon generation in the late hercynian orogeny late permian the triassic hydrocarbon pools are from secondary adjustment of earlier oil and gas pools from the underlying ordovician and carboniferous reservoirs due to the rapid subsidence of the kuqa foreland basin to the north of the tabei region since the beginning of the himalayan orogenic movement the triassic reservoir strata was changed from south dipping to north dipping resulting in the formation of plunging anticlines and hydrocarbon migration toward the south at the same time fault reactivation occurred in the area causing the hydrocarbons from the deeper reservoirs to migrate into the triassic structural traps through faults and unconformities and thus formed the widespread secondary hydrocarbon pools the structure inversion during the triassic and the formation of nose structures since the himalayan orogeny 250 290 ma permian controlled the secondary accumulation in the triassic reservoirs the reformation process of the hydrocarbon pools continued until the late himalayan orogeny when the gas was charged and developed condensate pools in the eastern area

the age of carbonatites kimberlites and lamprophyres from southern west greenland recurrent alkaline magmatism during 2500 million years abstract alkaline rocks were intruded into the precambrian basement in southern west greenland during at least five separate episodes the tupertalik carbonatite intrusion was emplaced around or before 2650 m y it is now metamorphosed in granulite facies but is recognisable by its trace element content lamprophyre dykes were intruded at ca 1800 m y and again at ca 1200 m y at ca 600 m y the sarfartoq carbonatite intrusion and extensive kimberlite dykes were emplaced in the holsteiborg stromfjord region at 225 115 m y the qaqarssuk carbonatite complex was emplaced in the sukkertoppen region and numerous lamprophyre and kimberlite dykes were emplaced between fishenasset and ivigtut all these episodes are correlatable with contemporaneous alkaline activity in canada and scandinavia and substantiate the periodicity of carbonatite emplacement the mesozoic suite of intrusions is related to rifting prior to continental break up and the formation of the north atlantic ocean the eocambrian suite of 600 m y is thought to have formed under similar conditions during continental break up and the formation of the iapetus ocean

some constraints on the kinematics of the tertiary piemonte basin northwest italy abstract an analysis of fault slip data in oligocene and miocene sediments of the piemonte basin northwest italy shows that a nearly continous sweep of shortening directions exists between the northern apennines and the maritime alps transport directions change from n s to nw se near the western termination of the northern apennines through w e in the ligurian alps to sw ne in the maritime alps n nw directed thrusting along the front of the monferrato culmination fits within this general kinematic framework in addition basement thrusts and transform faults were not sealed by an oligocene transgression but remained active throughout the oligocene and miocene these data provide a distinct constraint on the tertiary kinematics and dynamics of the alps apennine system

isotopic preservation of himalayan tibetan uplift denudation and climatic histories of two molasse deposits two distinctive molasse deposits within the indo asian collision zone have been investigated to help understand the post oligocene evolution of the himalaya and southern tibetan plateau the siwalik group predominantly fluvial sandstones and siltstones is widespread throughout the foothills of the himalaya from pakistan to eastern india paleomagnetic analysis of a measured section in the bakiya khola southeastern nepal constrains depositional ages t dep to between 10 8 and 4 9 ma the average accumulation rate during this interval was 0 4 0 5 mm yr 40 ar 39 ar dating of 126 detrital k feldspars from nine horizons in the bakiya khola section t dep 8 25 to 2 2 ma provide snapshots in time of the cooling ages exposed at the earth s surface in this drainage basin the minimum age in the spectra from seven of the nine horizons averages only 3 m y older than t dep indicating exceptionally rapid unroofing in the himalaya throughout that interval half of the grains fro

time calibration of a pt path from the western tauern window eastern alps the problem of closure temperatures new hornblende k ar and 39ar 40ar and mica rb sr and k ar ages are used to place specific timemarks on a well constrained pressure temperature path for the late alpine metamorphism in the western tauern window after identification of excess 40ar the closure behavior of ar in hornblende is compared with that of sr and ar in phengite and biotite samples were collected in three locations whose maximum temperatures were 570 c zemmgrund 550 c pfitscher joch and 500 540 c landshuter hutte

40ar 39ar laserprobe direct dating of discrete deformational events a continuous record of early alpine tectonics in the pelagonian zone nw aegean area greece abstract the pelagonian zone of the hellenides which occurs in the northwestern aegean region of the eastern mediterranean contains remnants of a high pressure metamorphic belt which subsequently underwent localized reworking during low temperature deformational events formation of alpine deformational structures in the ossa massif northern pelagonian zone occurred at metamorphic temperatures which failed to reset most pre alpine 40ar 39ar cooling ages in muscovite porphyroclasts the low metamorphic temperatures at alpine times have preserved the argon isotopic signature in white mica bearing deformational structures which allows direct dating of these structures and refinement of the alpine tectonic history in the region after separation of carefully selected and characterized mica generations application of sensitive 40ar 39ar laserprobe dating has resulted in a continuous record of the early alpine tectonic history of the ossa massif from the early cretaceous well into the eocene the early alpine history of the ossa massif records cooling of basement thrust slices which are mostly hercynian granites and metamorphics below ca 350 c by 100 ma while lower tectonostratigraphic levels of the basement had already cooled below these temperatures at around ca 285 ma blueschist facies mylonite fabrics related to a top to ene direction of tectonic transport yield ages as old as 84 5 3 3 ma exhumation of the blueschist facies sequences was initiated at ca 54 ma and involved tectonic activity along blueschist facies and greenschist facies mylonites zones final wsw ward transport of the metamorphic sequence across the structurally lowest and supposed autochthonous series occurred at around 45 ma and resulted in termination of the ductile deformation history in the studied area this study confines the onset of high pressure metamorphism in the pelagonian zone to an interval between 100 ma and 85 ma and has shown that high pressure metamorphism had terminated by ca 54 ma the recognition of an early to middle alpine cycle lasting over 30 million years and involving crustal shortening high pressure metamorphism exhumation and subsequent crustal shortening is a key contribution to a better understanding of the early alpine tectonic history of the aegean region and eastern mediterranean

geochemistry mineralogy and petrology of a new find of ultramafic lamprophyres from bulljah pool nabberu basin yilgarn craton western australia abstract four variously pipe or sill like carboniferous 305 ma bodies have been located near the ne edge of the archaean yilgarn craton the rocks comprise ba ti bearing tetraferriphlogopite tetraferriannite low al ti diopside calcite perovskite and groundmass titanomagnetite chromite up to 41 3 cr2o3 with minor apatite mg mn ilmenite rare earth phosphate k ba feldspar up to 17 bao baryte and an unidentified ba zr silicate the last three reflect very high whole rock ba up to 5 652 ppm aegirine rich pyroxenes occur in fenitic alteration assemblages together with high si al and low mg ca whole rock geochemistry these features are diagnostic of ultramafic lamprophyres damkjernites and aillikites although the rocks also show some affinities with classical kimberlites mineral concentrates from loam samples yield an array of minerals of mantle origin including garnets dawson and stephens groups g1 3 5 9 and 10 chromian diopsides up to 6 2 cr2o3 magnesiochromites up to 20 mgo 70 cr2o3 and four compositional groups of ilmenites low mn picroilmenites mn rich mg poor and two moderate mn mg compositions actual spinel lherzolite nodules are common in one body and the presence of spinel and or garnet lherzolites can be inferred in the others from the concentrates the bulljah bodies are therefore of deep mantle origin as confirmed by the recovery of a single microdiamond they thus extend the field of potentially if not necessarily economically diamondiferous rocks beyond kimberlites and lamproites when added to other recent lamprophyre finds the bulljah discoveries suggest that the yilgarn craton could like many other ancient cratons be ringed and or dotted by a diverse array of alkaline and lamprophyric rocks of varying ages which remain to be discovered

reconstruction of tertiary palaeovalleys in the south alpine foreland basin of france eocene oligocene of the castellane arc abstract the dynamics of depositional environments and the spatial deformation of drainage networks in foreland basins reflect the tectonic and erosional dynamics associated with the development of mountain belts the spatial and temporal organization of the eocene oligocene 40 25 ma sedimentation in the external part of the south alpine foreland basin of france was reconstructed using an integrated cartographic sedimentological and petrographic analysis of the tertiary sedimentary successions the depositional geometries and variations in facies and thickness of the palaeogene nummulitic succession as well as the observed flow directions in various continental and marine sediments suggest that the barreme blieux and taulanne synclines were present as palaeovalleys since the eocene the sedimentological analysis of the nummulitic succession allows the identification of three depositional sequences separated by transgressive surfaces that are recognized in the barreme blieux and taulanne synclines correlation of these sequences between the three synclines suggests that these palaeovalleys were connected by a local valley network that recorded the same sea level fluctuations during the marine nummulitic sedimentation the palaeovalley network was structurally controlled by the east west axes of the blieux and taulanne synclines and the north south axis of the barreme syncline formed during the pyrenean provencal late cretaceous middle eocene shortening and the first stage of the alpine history middle eocene respectively later on the westward alpine compression since the early oligocene induced local depocenter migration and reversal in flow direction however compared to the modern river pattern the palaeovalley orientation highlights a geometrical stability since their formation about 40 ma suggesting a long term stability of the early structures in the foreland basin this constancy can be explained by the location of the study area in a piggy back basin transported at the top of the provencal thrust sheet that facilitated the preservation of the overall axis orientation of the palaeovalleys

two stage erosion and deposition in a continental margin setting an 40ar 39ar laserprobe study of offshore detrital white micas in the norwegian sea detrital white micas from a restricted region of the norwegian sea have been analysed by the 40ar 39ar laserprobe examining the ages of individual white mica grains from offshore triassic jurassic and cretaceous sandstones reveals a narrow range of detrital white mica ages 369 424 ma moreover there is an inverse relationship between sediment age and detrital white mica age with the triassic sands containing a larger proportion of younger white micas and the cretaceous sands containing the oldest white micas in addition residence times of the detritus which is the age of the sediment subtracted from the age of the detrital white mica range from c 150 to c 300 ma for the triassic and cretaceous sands respectively the inverse age relationships combined with the large residence times for these stratigraphic levels can best be explained by an erosion deposition model involving at least two stages taking into account previous provenance studies in the lofoten region of the norwegian sea these new data suggest that detritus shed initially from the exhuming caledonian nappes of nw norway in late silurian early devonian times was deposited in intramontane basins that were themselves subsequently unroofed and re eroded from permo triassic times this caused the recycling of the caledonian detritus from the devono carboniferous basins and led to the inverted detrital age distribution ovserved in the triassic cretaceous sediments examined in this study while sedimentary recycling is not a surprising feature for mesozoic basins in the north and norwegian seas this study documents a previously untapped method 40ar 39ar laserprobe provenance studies by which to identify its effect and extent

sedimentary cycles and volcanic ash beds in the lower pliocene lacustrine succession of ptolemais nw greece discrepancy between 40ar 39ar and astronomical ages a high resolution cyclostratigraphy for the rhythmically bedded lignite marl sequences of the lower pliocene ptolemais formation is combined with 40 ar 39 ar dating results of intercalated volcanic ash beds detailed field reconnaissance in three open pit lignite mines reveals three end member sediment types lignites composed primarily of organic material grey marls a mixture of carbonate and organic material and beige marls almost exclusively composed of carbonate these lithologies are arranged in two basic types of sedimentary cycles lignite grey marl and lignite beige marl cycles a cyclostratigraphic composite section comprising 56 lignite marl cycles is constructed which combines the consistent cycle patterns from three parallel sections the concordant positions of 20 volcanic ash beds in these sections confirm the cyclostratigraphic correlations and indicate that the lignite marl cycles result from regional basin wide forcing rather than lateral facies migrations 40 ar 39 ar ages on sanidine and biotite separates from nine volcanic ash beds were obtained by multiple total fusion and incremental heating experiments the 40 ar 39 ar ages range between 5 00 0 05 and 4 04 0 04 ma and are in general consistent with the stratigraphic order a least square linear regression using the measured 40 ar 39 ar ages gives an average duration of 21 8 0 8 kyr per lignite marl cycle evidently the lignite marl cycles in the ptolemais formation are linked to the precessional variation in the earth s orbit through its influence on mediterranean climate for the first time 40 ar 39 ar dating results totally independent from any other dating and or tuning technique confirm the astronomical theory of climate change the 40 ar 39 ar ages of the volcanic ash beds show a constant200 kyr 4 5 age discrepancy with the astronomical ages of the same ash beds this inconsistency remains difficult to explain the discrepancy is unlikely to have resulted from erroneous astronomical ages through incorrectness in the astronomical tuning inaccuracies of the magnetostratigraphic data or the orbital time series used and or errors in the apts the 40 ar 39 ar dating results neither give clear indications for a possible source of error from the excellent data set it is evident that neither loss of radiogenic 40 ar nor an underestimation of the contribution of ca and k derived ar isotopes could have caused the discrepancy moreover the discrepancy is also beyond the errors in the systematic variables like the decay constants of 40 k or the ages for the neutron fluence monitors 1999 elsevier science b v all rights reserved

precise tracing of exhumation and provenance using 40ar 39ar geochronology of detrital white mica the example of the central alps

magnesian ilmenitite xenoliths in a basanite from tahalra ahaggar southern algeria large magnesian ilmenite nodules occur in a quaternary basanitic volcano near silet in the tahalra volcanic area central ahaggar southern algeria their texture from foliated to polygonal is ascribed to solid state flow and dynamic recrystallization in upper mantle conditions

comment on subduction polarity reversal at the junction between the western alps and the northern apennines italy by g vignaroli c faccenna l jolivet c piromallo f rossetti abstract we discuss the model for the reversal of the subduction polarity in the alps apennine system proposed by vignaroli et al vignaroli g faccenna c jolivet l piromallo c rossetti f 2008 subduction polarity reversal at the junction between the western alps and the northern apennines italy tectonophysics 450 34 50 this model integrates recently published tomographic data with a re interpretation of the surface geology of the voltri massif to suggest a tertiary extensional regime of nappe excision the structural reconstruction proposed by vignaroli et al vignaroli g faccenna c jolivet l piromallo c rossetti f 2008 subduction polarity reversal at the junction between the western alps and the northern apennines italy tectonophysics 450 34 50 individuates in the voltri massif two major tectonic complexes an eclogite facies unit the lower tectonic complex ltc underneath a low grade tectonic element the upper tectonic complex utc which attained significantly lower p t conditions the two complexes are separated by a major extensional contact most of the arguments exposed by vignaroli et al vignaroli g faccenna c jolivet l piromallo c rossetti f 2008 subduction polarity reversal at the junction between the western alps and the northern apennines italy tectonophysics 450 34 50 to substantiate such a nappe pile reconstruction and the proposed extensional regime do not properly consider the field data the datasets available in the literature and the published geological maps also the available p t data and metamorphic histories of rocks pertaining to the ltc and utc do not provide evidence for a significant pressure jump between the two complexes in addition the expected thermal effects achieved during metamorphism in a regime of crustal thinning and astenospheric uprise do not occur in the study area we conclude that the evidence supporting the geodynamic model proposed by vignaroli et al vignaroli g faccenna c jolivet l piromallo c rossetti f 2008 subduction polarity reversal at the junction between the western alps and the northern apennines italy tectonophysics 450 34 50 is poorly convincing and not supported by the field and petrologic observations both the re interpretation of the surface geology and the resulting crustal reconstruction have several major flaws

rare earth element and clay minerals of paddy soils from the central region of the mekong river laos abstract the rare earth elements ree content particle size distribution and clay mineralogical composition were analyzed for the paddy soils collected from the central region of the mekong river laos to study the origin and inherent potentiality of soils ree as the chondrite normalized curve of the plot of ce eu against eu sm were found to be useful for grouping soils according to their origins the soils in the upper area luang prabang province approximate elevation 300 400 m were estimated to originate from the composite materials of the sediment derived from local granite and limestone and the sediment transported by the mekong river the predominant clay mineral was mica and its weathering product or kaolins and the mineralogical composition varied from site to site the soils were generally characterized by high clay and silt contents inherent potentiality was evaluated to be of intermediate to high level the soils in the lower area vientiane prefecture and borikhamxay province approximate elevation 90 150 m were estimated to originate from sediment transported by the mekong river or from sediment derived from local sandstone the soils originating from the mekong river sediment were medium textured and mica dominated and were evaluated to be at the intermediate level of inherent potentiality the soil originating from the sediment of local sandstone was coarse textured and contained mica and kaolinite as the predominant clay minerals its inherent potentiality was evaluated to be poor

uplift history of thrust belts an approach based on fission track data and thermal modelization abstract a tentative method to reconstruct the uplift history in thrust belts from fission tracks ft data is proposed as it is well established that the thermal gradient varies considerably both with time and depth in the evolution of mountains a time dependent thermal model is used to infer the temperature time history of sampled rocks given parameters such as the thrust thickness 7 t and the erosion v t randomly chosen in an acceptable range among a great number of trials monte carlo simulation this technique is applied to the corsican island which is a good example of alpine thrust belt the most striking result is that a large range of different possible erosion histories can explain the same set of ft data and that further geological constraints are required to give reasonable bounds in the case of corsica information on the minimum eroded thickness and on the relative amplitude of erosion phases gives sufficient constraints on the erosion uplift history since thrusting

the carbonate fraction in carbonatitic italian lamprophyres abstract alkaline and ultramafic lamprophyres represent the majority of pre pleistocene alkaline mafic magmatic activity in italy and have been described from several localities the age of magmatism ranges from triassic to lower oligocene some contain appreciable amounts of carbonate the primary carbonate of the italian carbonatitic lamprophyres is mainly sr or mn rich calcite that occurs mostly as immiscible ocelli or as groundmass its textural occurrence composition and relationship with co precipitating silicate phases is taken as evidence of an igneous origin low bao and ree contents in the carbonate are explained by early crystallization of essential mica and subordinate apatite whole rock analyses and isotopic data rukhlov a s bell k vichi g stoppa f submitted for publication the heterogeneous deep mantle the sr pb and nd isotopic evidence from early cretaceous alkaline lamprophyres of southern tuscany italy lithos suggest a mantle origin for these rocks and rule out contamination in either high or low pressure regimes the bulk compositions of the carbonatitic lamprophyres have high hfse lile and lree hree ratios and although the abundances of these elements are generally lower than for carbonatites s s they are comparable with the abundances in other carbonate free italian lamprophyres and italian carbonatites suggesting similar mantle sources moreover the age of the italian lamprophyres ranging from middle triassic to lower oligocene is much greater than the pleistocene age of italian carbonatites and indicates that the source remained similar over a long time span

detrital zircon u pb ages and hf isotopic constraints on the terrigenous sediments of the western alps and their paleogeographic implications detrital zircons from cretaceous micaschist late eocene earliest oligocene sandstone and early oligocene siltstone of the western alps fall into three main separable age clusters at 610 540 ma 490 430 ma and 340 280 ma that correspond to the cadomian neoproterozoic ordovician and variscan carboniferous events widespread in western and central europe hf isotopic results indicate that these three magmatic and tectonic episodes did not give rise to significant production of juvenile crust a distinguishable group of triassic zircons around 250 200 ma which is considered to derive from the southern alps has been detected in the early oligocene schistes a blocs formation and the brianconnais flysch noir in contrast this age group is absent in late eocene earliest oligocene sandstones in agreement with sedimentological studies our results show that the main source areas of the eocene sandstone were probably located in the european continent the arrival of detritus from the internal zone occurred in early oligocene coeval with the tectonic rotation from northwestward to westward in the propagation of allochthonous units based on previous studies and our new data we argue that the the brianconnais zone was likely a paleorelief since the middle eocene that accounts for the lack of detritus from the adriatic units contemporary sediments were accumulated in the foredeep of the adriatic plate from oligocene time onwards the blockage was cut through after a regional uplifting and thus the internal zone started to provide detritus into the western flexural basins

40ar 39ar laser probe dating of detrital micas from the montgomery creek formation northern california clues to provenance tectonics and weathering processes generic provenance data from the montgomery creek formation northern california even in light of paleocurrent data and regional stratigraphic patterns do not uniquely establish its sediment source dating individual detrital mica grains mica with the sup 40 ar sup 39 ar laser probe shows that the source area for the upper montgomery creek included the idaho batholith unaltered muscovite grains yield data that provide limits on timing and rate of uplift of the batholith combined with paleocurrent data the inferred provenance constrains the timing of tectonic rotation in the southeastern klamath orogen dating variably altered biotite grains elucidates the age and environment of alteration and establishes a distinct source for some of the lower montgomery creek

testing models of orogen exhumation using zircon u th he thermochronology insight from the ligurian alps northern italy testing models of orogen exhumation requires precise constraint of the time temperature paths of the exhumed rocks the zircon u th he zhe thermochronometer has a closure temperature of 140 210 c and can provide temporal constraints on the exhumation history of rocks through a thermal range which crucially corresponds the onset of brittle behaviour of an exhuming orogen we performed zhe analyses to test the existing contradictory models for the exhumation of the ligurian alps the zhe ages indicate a very rapid 1 3 6 8 mm yr and southward migrating exhumation of the orogen between 32 and 25 ma these high exhumation rates are unique within the alpine belt and cannot be reconciled with existing geodynamic models of the evolution of the ligurian alps we propose a model of tectonic denudation via detachment accomplished in the shallowest crust 5 km as a result of the last orogenic phase of extension

criteria for the recognition of metamorphosed or altered lamprophyres a case study from the archaean of kambalda western australia abstract the ability to distinguish ancient lamprophyres from other mafic and ultramafic intrusive rock types has become increasingly important lamprophyres have been used as marker horizons in the mapping of several precambrian terranes they have been recognized for decades as possible indicators of gold mineralization and their presence has implications for the tectonic interpretation of ancient greenstone belts whilst fresh undeformed lamprophyres are readily recognized metamorphosed altered and or deformed examples are more problematical the intrusive ages of kambalda lamprophyres are constrained by available field and geochronological evidence including direct dating of one kersantite to the period 2684 2660 ma these rocks therefore belong to the world s oldest group of alkaline rocks and lamprophyres so far recognized which also includes contemporaneous examples from canada zimbabwe and probably tanzania despite their extreme age and low to medium grade regional metamorphic history these rocks still preserve characteristic lamprophyric textures chemistry and mineralogy only where metamorphism has been overprinted by gold related alteration and deformation do the lamprophyres cease to be recognizable petrographically however their unique chemistry persists and despite losses of the most mobile elements from presumed magmatic compositions altered and deformed specimens still retain far higher contents of sr k ba th nb p zr and ce than basalts of the local greenstone succession even lamprophyres which have been converted to biotite plagioclase carbonate pyrite schists retain this distinctive chemical signature during both alteration and metamorphism mobile elements k rb sr ba display far larger changes than archetypal immobile elements ce nb zr p ti clearly sanctioning traditional preference for the latter in assessing altered rocks however the surprising loss of nb during biotitization of hornblende indicates that negative nb anomalies conventionally regarded as indicators of subduction related magmatism can also be induced purely by alteration processes

origin of mud in turbidites and hybrid event beds insight from ponded mudstone caps of the castagnola turbidite system north west italy the partitioning of different grain size classes in gravity flow deposits is one of the key characteristics used to infer depositional processes turbidites have relatively clean sandstones with most of their clay deposited as part of a mudstone cap or as a distal mudstone layer whereas sand bearing debrites commonly comprise mixtures of sand grains and interstitial clay hybrid event beds develop alternations of clean and dirty clay rich sandstones in varying proportions analysis of co genetic mudstone caps in terms of thickness and composition is a novel approach that can provide new insight into gravity flow depositional processes bed thickness data from the ponded castagnola system show that turbidites contain more clay overall than do hybrid event beds the castagnola system is characterized by deposits of two very different petrographic types thanks to this duality analyses of sandstone and mudstones composition allow inference of which proportion of the clay in each of the deposit types was acquired en route in combination with standard sedimentological observations the new data allow insight into the likely characteristics of their parent flows clean turbidites were deposited by lower concentration long duration erosive muddy turbidity currents which were more efficient at fractionating clay particles away from their basal layer hybrid event beds were deposited by shorter duration higher concentration less erosive sandier flows which were less efficient at clay fractionation the results are consistent with data from other turbidite systems for example marnoso arenacea the approach represents a new method to infer the controls on the degree of clay partitioning in gravity flow deposits

the rare earth element compositions of sediments from the loess tableland in the liyang plain southern china implications for provenance and weathering intensity to identify the weathering intensity and to deduce the provenance of sediments black brown soil and loess from the loess tableland in the liyang plain is of great importance for understanding the development and origin of civilization of this critical region in china the geochemical results show similar ree distribution patterns among sediments sampled from the yc profile in the liyang plain reticulated red soils from the dongting lake area xiashu loess in zhenjiang and loess from the loess plateau in china these similarities imply a single provenance from dust storms rees especially the lree hree ratio and eu anomaly can trace weathering intensity higher lree hree ratios and remarkably eu anomalies are present in the top loess l0 lower lree hree ratios and insignificant eu anomalies are present in black brown soil s0 from the liyang plain these demonstrate that the black brown soils have undergone a lower intensity of weathering than the loess of yc profile moreover cia values for sediments from the yc profile provide powerful evidence to support the above result comparisons of analyses of the ree contents of sediments from the yc profile of reticulated red soils from the dongting lake area xiashu loess from the yangtze river and loess from the loess plateau clearly show the weathering intensity decreases according to the following sequence reticulated red soil from the dongting lake area sediments of yc profile from the liyang plain which formed from dust storms xiashu loess from lower reach of the yangtze river loess from the loess plateau

excess40ar in metamorphic rocks from broken hill new south wales implications for40ar 39ar age spectra and the thermal history of the region 40ar 39ar age spectrum analyses of samples from broken hill new south wales indicate that the region has experienced a complex thermal history following high grade metamorphism 1660 ma ago the terrain cooled slowly 3 c ma 1 until about 1570 ma ago when the temperature fell below about 500 c following granitoid emplacement 1500 ma ago the region remained relatively cold until affected by a thermal pulse 520 40ma ago causing temperatures to rise to 350 c in some places during this event accumulated40ar was released from minerals causing a significant ar partial pressure to develop laboratory ar solubility data combined with the40ar 39ar age spectra gives a local estimate of this partial pressure of 10 4atm the region finally cooled below 100 c about 280 ma ago 40ar 39ar age spectrum analyses of hornblende plagioclase and clinopyroxene containing excess40ar are characterized by saddle shaped age spectra detailed analysis of plagioclase samples reveals a complex diffusion behaviour which is controlled by exsolution structures this effect in conjunction with the presumed different lattice occupancy of excess40ar with respect to radiogenic40ar appears to be responsible for the saddle shaped age spectra

a 40ar 39ar laser probe study of micas from the sesia zone italian alps implications for metamorphic and deformation histories two samples from the eclogite micaschist complex emc and the seconda zona diorito kinzigitica iidk of the sesia zone have been studied using a high spatial resolution laser probe 40ar 39ar technique with the aim of investigating the complexities of argon behaviour in metamorphic rocks and comparing their thermal histories data from a single large phengite grain from the emc show a range of ages from mid jurassic to upper cretaceous these apparent age variations are spatially related to both location within the grain and to intragrain microstructure modelling of the data shows that the profile formed by the diffusion of an excess argon component into the grain parallel to the mica cleavage profile asymmetry is explained by temporal variations in microstructural development enabling excess argon to enter the grain at different times in different places the temperatures of the initiation of deformation and the possible time scales for the deformation can be calculated as a function of cooling rate all estimates suggest deformation at greenschist facies in accord with the observed retrograde mineral assemblage absolute temperature estimates for deformation vary by less than 22 c for different cooling rates of 10 and 30 c ma 1 but vary by 80 c with different estimates of diffusion parameters the duration of deformation was for at least 2 ma at 10 c ma 1 or 0 7 ma at 30 c ma 1 biotites from the iidk sample record a permian to upper cretaceous age range that correlates with grain size the smallest grain sizes yielding the youngest ages this relationship is best explained by a partial resetting of biotites during an alpine thermal event initiated not more than 70 ma ago modelling of these data suggest that the sample never exceeded 300 c during the alpine the profoundly different thermal histories of the two units the emc recrystallized at 550 c whilst the iidk remained below 300 c suggests that they may not have been juxtaposed until much later than the eclogite facies metamorphism

provenance of cretaceous synorogenic sandstones in the eastern alps constraints from framework petrography heavy mineral analysis and mineral chemistry abstract the detrital components of cretaceous sedimentary rocks in the northern calcareous alps reflect the early alpine geodynamic evolution of the austroalpine microplate two contrasting source areas are distinguished on the base of light and heavy mineral analysis the first source area is located at the southeastern margin of the austroalpine and is composed of palaeozoic sediments and metamorphic rocks mesozoic carbonate rocks and ultrabasic rocks derived from the suture zone of the vardar meliata ocean the second source area is located in the northwest in a lower austroalpine position near the transpressive plate margin that juxtaposes austroalpine and penninic units this source area comprises palaeozoic low grade metamorphic rocks including high pressure hp rocks late palaeozoic meta sediments mesozoic carbonate rocks and ultrabasic rocks from obducted slices of penninic oceanic crust chemical analyses of detrital white mica amphibole and garnet support the discrimination between the two source areas tourmaline chemistry calls for a significant amount of metasedimentary rocks in the source area granitoid rocks and high grade metamorphic rocks are rare blue amphibole phengite and chloritoid composition suggest the erosion of lower blueschist facies rocks in the northwestern source area we suggest a modified model of austroalpine valanginian to coniacian tectono sedimentary evolution which is based on 1 an onset of subduction of the penninic ocean no earlier than late cretaceous 2 deposition of the analyzed sedimentary rocks in piggyback basins and 3 a reconstruction of provenance as proposed in this study

laser 40ar 39ar dating of single detrital muscovite grains from early foreland basin sedimentary deposits in india implications for early himalayan evolution in india the dagshai and overlying kasauli formations represent the oldest exposed continental foredeep sediments eroded from the himalayan orogen 40ar 39ar dating of individual detrital white micas from these sedimentary units has provided maximum depositional ages of 28 ma for the dagshai formation at one locality and 25 ma at a second locality whereas deposition of the kasauli formation occurred after 28 ma at two localities and after 22 ma at a third locality this timing suggests that in india the start of substantial exhumation and erosion from the rising himalayan orogen was delayed until 28 ma

a review on the potentiality of rare earth elements to trace pedogenetic processes abstract this review aims at considering the use of rees to trace pedogenetic processes in order to quantify the respective contribution of the successive processes on pedogenesis we first consider the origins and contents of rees in soils to assess their natural occurrence and tackle the common data treatment used to interpret their concentrations we review subsequently the impact of the different pedogenetic processes on the fate of rees in soils from their release into a soil solution by primary mineral heavy minerals phosphates silicates and carbonates dissolution during weathering to their fixation on or into main ree bearing secondary minerals clay minerals fe mn oxides and carbonates then their mobilization by plant recycling and organic matter and finally the impact of argilluviation and redox processes on their fractionation we conclude that rees much more than other trace elements can interestingly trace the considered processes that are encountered in a large diversity of non polluted soils arising from diverse parent materials weathering generally fractionates rees and accounts for a significant part of the variation in the initial ree stock of the soils plant recycling induces a weak mobilization of rees and their accumulation in topsoil argilluviation can be traced using the mree enrichment and the eu anomaly of the clay minerals redox processes can be traced by the ce anomaly caused by the precipitation of cerium on mn oxides to use rees as tracers of pedogenetic processes we recommend to i precisely characterize the ree bearing minerals ii adapt the choice of reference s for normalization and iii perform mass balance calculations

retrogressive fabric development during exhumation of the voltri massif ligurian alps italy arguments for an extensional origin and implications for the alps apennines linkage geological mapping coupled with structural investigations carried out in the voltri massif eastern ligurian alps italy provide new data for the interpretation of the tectonic context controlling main fabric development during exhumation of its high pressure core the voltri massif is here interpreted as a c 30 km long eclogite bearing asymmetric dome formed by the progressive verticalisation of the regional second phase mylonitic foliation developed during retrogressive greenschist metamorphic conditions in this light the exhumation history is driven by a ductile to brittle extensional process operating through low angle top to the w multiple detachment systems a late eocene early oligocene age for this extensional episode is proposed on the basis of structural correlations stratigraphic and radiometric constraints in this scenario the voltri massif is interpreted as an extensional domain developed to accommodate the late eocene early oligocene arching of the western alps northern apennines orogenic system

the formation of representative lateritic weathering covers in south central guangxi southern china the mineralogy and geochemistry have been studied in three representative lateritic weathering covers close to the tropic of cancer guangxi south china with the purpose of studying formation and evolution processes of lateritic covers in this region the x ray diffraction and scanning electron microscope analysis results indicate that the contents particle sizes shapes and structures of secondary minerals such as iron and clay minerals are distinctly different in ferruginous nodular horizon and mottled clay layer of lateritic profiles the ferruginous nodules are characterized by high concentrations of iron and aluminum and low contents of silicon the energy analysis suggests that there are element exchanges between hematite crystal and clay minerals the mass balance calculation results show that there is exogenetic input of iron into lateritic covers especially within the ferruginous nodular horizon compared to the bottom layer of the profile the scanning electron microscope images also confirm that voids and fractures in ferruginous nodules were filled with ferruginous material derived from soil solution this could be a significant interpretation for the negative correlations between fe2o3 and al2o3 the iron and manganese oxides in ferruginous nodular horizon have an apparent effect on the adsorption and precipitation of cerium strontium compared to other alkali metal and alkali earth metal elements concentrates in mottled clay layer variation in the he gt ratio reflected by the o fe ratio in a small ferruginous concretion indicates that climate changes altered aqueous activity of the soil environment finally a model for the formation and evolution of typical lateritic weathering covers in south central guangxi supported by all the data was proposed

rare earth elements in fine grained sediments of major rivers from the high standing island of taiwan thirty eight sediment samples from 15 primary rivers on taiwan were retrieved to characterize the rare earth element ree signature of fluvial fine sediment sources compared to the three large rivers on the chinese mainland distinct differences were observed in the ree contents upper continental crust normalized patterns and fractionation factors of the sediment samples the average ree concentrations of the taiwanese river sediments are higher than those of the changjiang and huanghe but lower than the zhujiang light rare earth elements lrees are enriched relative to heavy rare earth elements hrees with ratios from 7 48 to 13 03 we found that the variations in la lu ucc gd lu ucc and la yb ucc gd yb ucc are good proxies for tracing the source sediments of taiwanese and chinese rivers due to their distinguishable values our analyses indicate that the ree compositions of taiwanese river sediments were primarily determined by the properties of the bedrock and the intensity of chemical weathering in the drainage areas the relatively high relief and heavy rainfall also have caused the rees in the fluvial sediments from taiwan to be transported to the estuaries down rivers from the mountains and in turn delivered nearly coincidently to the adjacent seas by currents and waves our studies suggest that the ree patterns of the river sediments from taiwan are distinguishable from those from the other sources of sediments transported into the adjacent seas and therefore are useful proxies for tracing the provenances and dispersal patterns of sediments as well as paleoenvironmental changes in the marginal seas

staircase 40 ar39ar spectra of fine grained white mica timing and duration of deformation and empirical constraints on argon diffusion staircase 40 ar 39 ar spectra of 2 to 6 m white micas in ductile carbonate mylonites morcles doldenhorn nappe switzerland record ages between 32 and 13 ma these ages are within independent geochronologic and biostratigraphic time limits for the beginning and ending of deformation of this fold thrust nappe we interpret these data to record protracted white mica neocrystallization and growth during low temperature ductile deformation such that the differences between the maximum and minimum ages in the 40 ar 39 ar spectra record the time span over which mica formed and grew we have modeled the argon concentrations in these micas taking into account the thermal history of the nappe mica growth and diffusional loss of argon our results indicate that available experimental data underestimate the activation energy for argon diffusion in muscovite and that the retentivity of argon in white mica is greater than generally thought

rapid exhumation and mountain building in the western alps petrology and 40ar 39ar geochronology of detritus from tertiary basins of southeastern france 1 tertiary convergence high pressure low temperature hp lt metamorphism and subsequent exhumation in the internal western alps were concurrent with detrital deposition in foreland basins at the external periphery of the orogen in the present work we have probed the geochronology and chemistry of white mica grains and metamorphic pebbles from the foreland basins of se france in order to gain additional perspective on exhumation rates and mountain building processes in the internal domain of the tertiary orogen our data indicate that throughout the tertiary these basins were mainly fed from a relatively low pressure source dominated by si poor micas yielding pre alpine 40ar 39ar ages small amounts of detritus composed of high pressure minerals and pebbles are first detected in early oligocene 30 32 ma strata of the barreme basin the 40ar 39ar geochronology of phengites from garnet blueschist pebbles from these strata yielded 34 3 ma ages indicating rapid ascent and exposure of hp lt rocks in the internal part of the orogen shortly after metamorphism to explain the preponderance of pre alpine micas alongside the rare presence of alpine hp lt detritus we suggest that the general architecture of the western alps whereby inner hp lt metamorphic units are cut off from the se france basins by a low grade lid of brianconnais back thrusts was rapidly built in the early oligocene and did not change significantly since then

episodic rapid uplift in the himalaya revealed by 40ar 39ar analysis of detrital k feldspar and muscovite bengal fan detrital k feldspar and muscovite samples from ocean drilling program leg 116 cores have been dated by the sup 40 ar sup 39 ar technique and have depositional ages from 0 to 18 ma from 4 to 13 individual k feldspars and 1 to 12 individual muscovites have been dated from 7 stratigraphic levels in every level at least one k feldspar and one muscovite yielded a minimum age identical within uncertainty to the age of deposition these results indicate that a significant portion of the material in the bengal fan is first cycle detritus derived from the himalaya therefore the substantial amount of sediment deposited in the distal fan in early to middle miocene time can be ascribed to a significant pulse of uplift and erosion in the collision zone at this time moreover these data indicate that throughout the neogene some part of the himalayan orogen was undergoing rapid erosion 1 to 10 mm yr this erosion must have been less than or equal to uplift relative to sea level the lack of granulite facies rocks in the eastern himalaya and tibetan plateau suggests to us that very rapid uplift must have been distributed in brief pulses over different parts of the mountain belt these datamore are incompatible with tectonic models in which the himalaya and tibetan plateau are uplifted either uniformly over the past 40 m y or mostly within the past 2 to 5 m y less

episodic exhumation in the western alps oligocene to miocene clastic sediments of the tertiary piedmont basin northwest italy were derived from erosion of western alps source rocks detrital white micas from dif ferent stratigraphic units and from sands of three present day rivers draining the internal western alps have been analyzed by 40 ar 39 ar geochronology our data suggest a wide spread fast cooling and exhumation event prior to ca 38 ma followed by a 30 m y period of slower cooling and exhumation combined with erosion of crustal rocks with uniform 40 ar 39 ar signatures these processes have resulted in a pattern of regularly increasing lag time up section

constraints on the exhumation and erosion of the high himalayan slab nw india from foreland basin deposits petrography sr nd isotope compositions and single grain laser 40ar 39ar ages of detrital white mica from early middle miocene molasse of the dharamsala and lower siwalik formations of northern india dated by magnetostratigraphy determine the sediment sources their metamorphic grade and exhumation rates in the himalayan palaeo hinterland deposition of the lower dharamsala member 21 17 ma occurred during the period of rapid isothermal decompression and crustal anatexis 24 18 ma of the metamorphic core this episode of decompression is thought to be coeval with thrusting on the main central thrust and normal faulting on the south tibetan detachment system the sediment composition and detrital mica ages indicate erosion from the rapidly exhumed metamorphic slab of the high himalayan crystalline series deposition of the upper dharamsala member 17 13 ma and basal siwalik group 13 12 5 ma spanned the period in which thrusting transferred south from the main central thrust the sediment composition and detrital mica ages contrast strongly with those of the lower dharamsala indicating erosion from sedimentary and low grade rocks the isotopic composition indicates that these rocks were part of the high himalayan series unaffected by tertiary metamorphism i e from upper structural levels of the high himalayan slab this suggests that a major reorganisation of the orogenic wedge occurred at 17 ma involving forward propagation of the mct and cessation of rapid exhumation of the metamorphic slab

genesis of two planosols in the massif central france abstract two planosols developed on gravelly quaternary sediments of the river allier in the limagne rift valley massif central france were studied parent material contained in addition to a granitic component large amounts of volcanic particles morphological chemical mineralogical and physical properties of both profiles were investigated to indicate some of the changes which have taken place during pedogenesis both profiles were characterized by pronounced textural contrasts between sandy a and e horizons and clayey b horizons soil formation rather than a transient depositional environment is thought to be responsible for this marked textural change clear dissolution features of all mineral grains except quartz and increasing amounts of volcanic fragments with depth suggested weathering increasing ratios of mobile basic cations to tio 2 with increasing depth corroborated this observation the presence of non laminated isotropic and anisotropic limpid clay coatings were also evidence of in situ mineral weathering in both profiles kaolinite predominated as clay mineral and increased towards the surface micromorphological observations of microlaminated dusty and impure clay coatings in b horizons of both profiles were clear signs of clay illuviation bulk densities were high in lower e horizons and upper b horizons field observations and micromorphological data showed clear signs of periglacial features the combination of pedogenic and periglacial processes has apparently lead to a considerable compaction abundant cemented iron and manganese features predominantly occurring in e horizons suggested surface water gleying micromorphological observations of illuviation coatings in b horizons and of fine material in a and e horizons demonstrated grainy aspects suggesting ferrolysis