cryptomelane a tool to determine the age and the physical chemical regime of a plio pleistocene weathering zone in a granitic terrain hagendorf se germany abstract cryptomelane a k mn bearing oxide is widespread in the lowermost part of the weathering supergene alteration zone of the hagendorf pegmatite se germany this supergene mn mineral has been used in the present study for k ar dating of weathering and paleohydraulic processes as young as plio pleistocene different cryptomelane age data found in the same weathering and paleohydraulic system resulted from continuous hydraulic processes in the weathering system rather than from a stepwise uplift that shaped the landscape in the granitic area of the ne bavarian basement an almost pure cryptomelane mineralization is indicative of the basal zone of supergene alteration because a complete separation of mn from fe can favorably be achieved only in the infiltration zone under slightly reducing conditions or in the percolation zone under slightly oxidizing conditions cryptomelane is precipitated under slightly oxidizing conditions from alkaline solutions in the percolation zone and cast as a marker for fluctuating paleo water levels manganese oxides uranyl phosphates and silicates were found at different depths in the weathering zone of this granitic terrain they were dated by different dating methods k ar and u pb and yielded the same age of formation consequently the 4 ma signal of both groups of supergene minerals has geomorphological and paleohydraulic connotation and is related to a unique geomorphological process the pliocene peneplanation gradual hydraulic adjustments gave rise to the younger pleistocene age found at shallow depth in the weathering zone

fibers and cylinders of cryptomelane hollandite in permian bedded salt palo duro basin texas selected core sections from the lower san andres units 3 4 5 upper san andres lower clear fork and the salado tansill formations fibers or cylinders found from only the lower san andres formation units 4 and 5 the upper san andres formation and the salado tansill salt the fibers are inorganic light to dark reddish brown pleochroic highly birefringent filamentary single crystals 5000 1 energy dispersive analyses sem and gandolfi x ray diffraction techniques have identified the fibers and cylinders as members of the cryptomelane hollandite series the fibers can be straight and or curved can bifurcate can form loops waves or spirals and can be isolated or in parallel groups detailed petrographic analyses show no evidence for recrystallization or deformation of the enclosing salt after fiber formation suggestion that the fibers grew in situ by a solid state diffusional process at low temperatures the cylinders are pleochroic highly birefringent light to dark reddish brown hollow thin walled open ended right cylinders having a 1 to 2 mu m wall thickness and variable lengths 2 to 434 mu m and diameters 6 to 55 mu m the cylinders found in the recrystallized salt are perhaps a residue from dissolved chevron salt the observation of cylinders partially or completely enclosed by salt stratigraphically above large fluid inclusions suggests that natural downward fluid inclusion migration has occurred in response to the geothermal gradient modified journal abstract

hematite and mn oxide u th he dates from the buckskin rawhide detachment system western arizona gaining insights into hematite u th he systematics

chronology of exotic mineralization at el salvador chile by 40ar 39ar dating of copper wad and supergene alunite exotic copper mineralization is a complex hydrochemical process linking supergene enrichment lateral copper transport and precipitation of copper oxide minerals in the drainage network of a porphyry copper deposit at the el salvador porphyry copper deposit in northern chile the majority of the exotic ore comprised a mixture of copper bearing manganese oxyhydrates termed copper wad x ray diffraction scanning electron microscopy and electron probe microanalysis show that the copper wad is composed of copper bearing cryptomelane k1 2 mn3 mn4 8o16 x h2o and birnessite k0 33 batchmode documentclass fleqn 10pt legalpaper article usepackage amssymb usepackage amsfonts usepackage amsmath pagestyle empty begin document mn 7 3 9 end document o14 7h2o structures these natural occurrences within the exotic ore provide the opportunity to directly date the formation of these deposits using recent advances in 40ar 39ar geochronology of supergene k mn oxides formed by weathering a suite of copper bearing cryptomelane and birnessite samples from exotic deposits within the el salvador district were characterized and dated by 40ar 39ar laser step heating supergene alunite kal3 so4 2 oh 6 found in paleospring feeder systems leading from the source zones of copper outward to the exotic mineralization was dated to independently constrain the age of exotic ore formation although the ar retentivity of the layered birnessite structure has been questioned by others the ar retentivity of these samples is thought to be a function of their natural preservation and limited postcrystallization ground water interaction in the hyperarid atacama desert the 40ar 39ar analytical results show that ar and or k losses after crystallization excess 40ar and 39ar recoil do not pose significant problems therefore in the context of exotic copper deposits within hyperarid environments this dating method is applicable to both cryptomelane and birnessite within copper wad the 40ar 39ar dating of exotic mineralization at el salvador indicates that supergene and exotic mineralization processes were active at 35 ma about 5 m y after the emplacement of hydrothermal mineralization and continued until the middle miocene the majority of exotic mineralization extends from the oligocene miocene 24 ma boundary through the middle miocene 11 ma and relates to supergene fluid emanating in multiple directions from the source of copper in indio muerto which represents a topographic high above the exotic deposits one reconnaissance date of exotic mineralization at the chuquicamata porphyry copper deposit yielded an age of 17 03 0 03 ma coincident with the known supergene alunite dates for this deposit reconnaissance dating at exotica mina sur and el abra proved problematic due to the presence of contaminant silicate minerals within the copper wad ages derived here for exotic mineralization are similar to the known supergene ages throughout northern chile the dates indicate that supergene exotic mineralization began at the eocene oligocene boundary and continued through the oligocene eventually ceasing in the middle miocene due to desiccation of the atacama desert a series of 10 cm thick supergene alunite veins were microsampled across their widths and dated to address the kinetics of alunite vein growth apparent growth rates of the veins vary from 71 to 100 mm m y in the horizontal direction to 24 mm m y in the vertical presumably caused by differences in pressure regimes due to their orientation

a geochronological 40ar 39ar and 87rb 87sr study of k mn oxides from the weathering sequence of azul brazil k mn oxides of hollandite group minerals such as cryptomelane k1 2 mn3 mn4 8o16nh2o are often precipitated authigenically in weathering profiles the presence of structural k allows these minerals to be dated by the k ar and 40ar 39ar methods making it possible to study the progression of oxidation fronts during weathering processes within the context of a recent 40ar 39ar study of cryptomelane from the azul mn deposit in the carajas region amazonia brazil vasconcelos et al 1994 defined three age clusters 65 69 51 56 and 40 43 ma and proposed that they correspond to the episodic precipitation of the three generations of mn oxide that have been identified in the deposit beauvais et al 1987 we performed a laser probe 40ar 39ar and 87rb 87sr study on new samples from the same mn deposit our 40ar 39ar data confirm that cryptomelane is a suitable mineral for 40ar 39ar dating although in some cases we clearly identify the existence of 39ar recoil effects although the corresponding age spectra are generally strongly disturbed our results also confirm that the earliest cryptomelane generation is of upper cretaceous paleocene age we obtained good plateau ages from veins and concretions of the second cryptomelane generation some of these results allow definition of a well constrained age cluster at 46 7 48 1 ma not observed by vasconcelos et al 1994 a petrographic study confirms that none of the samples analyzed in the present study contained material associated with the third generation of cryptomelane we propose that these new results support the idea of a more or less continuous crystallization of k mn oxides mainly constrained by local factors rather than the model advanced by vasconcelos et al 1994 which suggests that each cryptomelane generation corresponds to distinct weathering events related to global climatic changes 87sr 86sr data show large variations clearly inherited from the 2 1 ga parent rock of the mn protore the rb sr results demonstrate that minimum fractionation occurs during cryptomelane crystallization except for the latest generation which is depleted in sr this precludes use of the rb sr radiochronometer for dating secondary mn oxides in laterites

manganese ores in tunisia genetic constraints from trace element geochemistry and mineralogy abstract northern and central tunisia hosts few small scale stratiform and stratabound mn deposits low to medium in grade mn

reduced antarctic meridional overturning circulation reaches the north atlantic ocean 1 we analyze abyssal temperature data in the western north atlantic ocean from the 1980s 2000s showing that reductions in antarctic bottom water aabw signatures have reached even that basin trans basin oceanographic sections occupied along 52 w from 1983 2003 and 66 w from 1985 2003 quantify abyssal warming resulting from deepening of the strong thermal boundary between aabw and north atlantic deep water nadw hence a local aabw volume reduction repeat section data taken from 1981 2004 along 24 n also show a reduced zonal gradient in abyssal temperatures consistent with decreased northward transport of aabw the reduction in the antarctic limb of the moc within the north atlantic highlights the global reach of climate variability originating around antarctica

the new nb p aplite at reinhardsrieth a keystone in the lateral and depth zonations of the hagendorf pleystein pegmatite field se germany abstract the hagendorf pleystein pegmatite field hppf is the largest pegmatite concentration in central europe which has been intensively studied for its mineralogy mainly at hagendorf south pegmatite stock it was not until recently that the lateral and depth zonations of the hppf could be clarified when the newly discovered tabular aplite at reinhardsrieth aplite has been found at transition into the so called barren zone devoid of rare metals thereby the theory of the derivation of the hppf felsic mobilizates as a result of a successive differentiation of a pegmatitic melt from the flossenburg granite has to be discarded from the structural and lithological point of view stock like well zoned pegmatites e g hagendorf south developed in the hinge zone whereas tabular aplites such as reinhardsrieth evolved along the limb zone of strongly folded basement rocks in the latter case the accommodation space was smaller and the cooling of the felsic mobilizates much faster giving rise to fine grained aplitic rather than coarse grained felsic mobilizates chilled margin effect during the incipient stages of the evolution in the hppf at reinhardsrieth a stronger impact of granitization can be determined than at the neighboring aplites and pegmatites based upon the ree fractionation a tripartite subdivision may be established for the various pegmatites and aplites in the hppf 1 barren zone minor amounts of lree in a system otherwise dominated by feldspar and quartz 2 marginal zone mainly fe al phosphates plus columbite fe 3 central zone fe zn li phosphates plus columbite fe the afore mentioned zonation shows an e w trend and a bilateral symmetric arrangement of the various areas there are significant indications of an oxidizing facies to substitute for a more reducing facies at the transition from the central into the marginal zone of the hppf the key mineral for the primary pegmatite mineralization in the marginal and central zones is columbite fe its mn fe ratios plotted vs the ta nb ratios allow for an assessment to what extent metamorphic and magmatic processes have contributed to the built up of the pegmatites and aplites in the hppf even the most primitive nigrine hosted columbites fit well into this pattern forming a lithochemical halo in the roof rocks of the pegmatites the heavy mineral aggregated of rutile ilmenite nigrine giving host to the columbite as armored relicts got released from the basement rock on top of the pegmatites into the stream sediments where they are operative as an ore guide the morphology of zircon in the stream sediments has been utilized as an economic ore indicator the zr silicate is also indicative of the temperature of formation and closely supports the tripartite zonation established above manganiferous apatite is a good depth of emplacement indicator for each aplite and pegmatite respectively the higher the feo mno content of apatite the shallower the depth of emplacement of its host pegmatite or aplite vivianite in turn marks the onset of the hydrothermal alteration of the pegmatites and aplites and its mn contents relate to the depth where alteration has taken place or emplacement of the secondary phosphates the higher the mn content the shallower the depth of alteration peculiar element ratios were selected to design some key diagrams so as to corroborate the field based mineralogical and geological results in terms of zonation of genetic economic geology as well as to cater for applied economic geology as proximity indicators and ore guides when exploring for rare element pegmatite

an investigation of periglacial slope stability in relation to soil properties based on physical modelling in the geotechnical centrifuge results are presented from eight scaled centrifuge modelling experiments designed to investigate mass movement processes on thawing ice rich slopes four pairs of simple planar slope models were constructed one in each pair being of sufficient gradient to promote slope failure during soil thaw and the second having a gradient below the threshold for instability four frost susceptible soils were used three were normally consolidated and had different clay contents 2 12 and 20 and the fourth comprised the 20 clay soil but was over consolidated prior to model testing modelling protocols included freezing from the surface downwards under an open hydraulic system and thawing from the surface downwards under an enhanced gravitational field within the geotechnical centrifuge thereby utilising scaling laws to simulate correct prototype self weight stresses during thaw slopes below the stability threshold gradient were subjected to between 2 and 4 cycles of freezing and thawing simulating annual cycles those above the stability threshold were subjected to only one cycle since they failed during the first thaw phase thermal conditions pore water pressures surface movements and profiles of displacement are reported measured pore pressures are used in slope stability analyses based on a simple planar infinite slope model profiles of solifluction shear strain and mechanisms of slope failure are both shown to be sensitive to small changes in soil properties particularly clay content and stress history in all cases pore pressures rose rapidly immediately following thaw remained below the threshold for failure in low gradient models but exceeding the threshold to trigger landslides on steeper slopes upward seepage of melt water away from the thaw front contributed to loss of shear strength mechanisms of slope failure differed between test soils ranging from mudflow in non cohesive silt to active layer detachment sliding in over consolidated silt clay during solifluction shear strain was greatest at the surface in non cohesive silt and decreased rapidly with depth but in test soils containing clay the zone of maximum shear strain was located lower in the displacement profiles

estimated solubility products and fields of stability for cryptomelane nsutite birnessite and lithiophorite based on natural lateritic weathering sequences

manganese deposits in the global lithogenetic system quantitative approach abstract a computerized data base including 330 localities and believed to represent at least 95 of the presently recorded spot accumulations of ore grade mn on land is the basis for a quantitative analysis of terrestrial mn resources this file is reprinted in full appendix the present subaerially exposed global ore mn resources are calculated as 17 9 109 t mn 1 in this figure are included the actually mineable straight mn deposits 8 7 109 t mn potentially mineable land based mn accumulations 9 2 109 t mn and actual or potential mn that could be extracted as a byproduct of mining other metals 0 6 109 t mn this distribution is strongly influenced by giant accumulations where the single exceptional kalahari mn field contains over 50 of the presently economic mn ore reserves or 23 42 of the global land mn resources a set of attributes has been selected to treat the global ore mn population in terms of genesis geotectonic and environmental setting and lithologic associations in terms of genesis precipitation from aqueous solutions was responsible for at least 99 of the contemporaneous and probably also the past mn accumulations now exposed on land weathering of mn orebodies has left its mark on 93 of the mn localities and 24 are now represented entirely by supergene assemblages less than 0 01 of the ore mn resources however are formed by weathering related accumulation over silicate rocks ultramafics in terms of geotectonic environments the bulk of the land based mn deposits 97 formed in intraplate and stable continental margin settings 3 1 formed along pacific type and rift type continental margins and only 0 00045 of the deposits formed in an oceanic setting this is in contrast with the outstanding mn accumulating capacity of the present ocean and is a consequence of the low preservation potential of the oceanic domain in terms of lithologic associations 96 of the mn in land based deposits is present in marine sedimentary associations 70 of mn is in banded iron formations 14 4 is in detrital and 11 1 is in carbonate dominated associations chert and jasper limestone sandstone shale and banded iron formation are statistically the most common immediate hosts to mn ores with recorded hosting frequencies of 79 50 45 37 and 35 respectively in terms of geological history the lower proterozoic accounts for 58 9 of the prreserved ore mn on land followed by oligocene 17 2 jurassic 6 2 and middle proterozoic 4 5 in terms of the intensity of mn accumulation per one million years of geological time oligocene 110 106 t mn ma is two orders of magnitude greater than the nearest time periods jurassic 8 9 106 t mn ma and lower proterozoic 6 5 106 t mn ma the historical distribution pattern of the land based mn deposits seems to indicate that accumulation of the bulk of the present ore grade mn is the result of repeated recycling with a land ocean trend abruptly initiated at the time of early cratonization about 2 5 ga this has been supplemented by a substantially less significant but remarkably steady reverse trend of addition of juvenile mn released from the mantle into the crust mafics and particularly basalts are the most important intermediaries in the cumulative secular increase of liberated and accumulated mn in the crust direct to indirect proven to hypothetical spatial coincidence of basalts and mn ores can be demonstrated on at least 169 localities out of 330 51 evaluated

capturing digital data of rock magnetic gamma ray and ir spectrometry for in situ quality control and for the study of the physical chemical regime of residual kaolin deposits se germany abstract residual kaolin deposits are operated on a worldwide basis the majority of them is derived from chemical weathering of felsic rocks during the cenozoic this is true for the kaolin deposits on the western edge of the bohemian massif here this type of deposit provides industrial minerals for the ceramic industry in se germany this raw material formed under tropical climatic conditions during the miocene and pliocene across a vast peneplain only within the naab wondreb depression however were economic accumulations preserved from erosion here near tirschenreuth kaolin has been mined since its discovery in 1830 the semi consolidated regolith is composed of quartz and opaline material alkaline feldspar different types of kaolinite muscovite illite a variegated spectrum of 14 a phyllosilicates fe mn oxide hydroxides and minor heavy minerals mainly containing ti a precise determination of the mineralogical composition of the ceramic raw material has so far solely relied on laboratory techniques e g xrd xrf and spectroscopic methods to the contrary this study takes a different approach capturing digital data in the field to determine its mineralogical composition gamma spectrometry k u th measuring the susceptibility of and analyzing short wave infrared spectra allows for an in situ quality control of the run of mine raw material it further assists in mapping the monotonous lithology and enables the authors to constrain the physico chemical regime throughout formation of the kaolin deposit the benefit for technical mineralogy and applied economic geology and the strong points of capturing digital data in the field is the easy and cost efficient handling of the various methods methods that were applied in this way for the first time the in door calibration and test measurements as well as the data acquisition during the field survey are presented and the data are correlated with the enhancing or deteriorating impacts of the inferred minerals on the firing behavior of the ceramic product collecting digital data can also help constrain the physico chemical regime during formation of the argillaceous deposit and improve further exploration through fine tuning the genetic model of residual kaolin accumulation the late carboniferous granites around tirschenreuth underwent strong supergene alteration in the ph range of 2 5 7 at log a sio2 aq 2 5 to 3 5 which resulted in a thick kaolinitic regolith illite formed under slightly increased ph between 4 and 7 attests to a change from tropical to more temperate humid conditions in the area the chlorite group phyllosilicates and nontronitic members of the smectite group came into existence when the ph increased to a ph interval of 7 to 11 this considerable change in the ph of the meteoric solutions occurred at the end of the neogene between 4 55 ma and 3 99 ma the different field methods compensate for each others weak points neither method is successful on its own but the current configuration can easily be expanded to include additional methods as there are neutron and micro resistivity and air and space borne approaches to cover more swiftly a larger exploration or study area

late cenozoic deep weathering patterns on the fennoscandian shield in northern finland a window on ice sheet bed conditions at the onset of northern hemisphere glaciation abstract the nature of the regolith that existed on the shields of the northern hemisphere at the onset of ice sheet glaciation is poorly constrained in this paper we provide the first detailed account of an exceptionally preserved deeply weathered late neogene landscape in the ice sheet divide zone in northern finland we mine data sets of drilling and pitting records gathered by the geological survey of finland to reconstruct regional preglacial deep weathering patterns within a gis framework using a large geochemical data set we give standardised descriptions of saprolite geochemistry using a variant of the weathering index of parker wip as a proxy to assess the intensity of weathering we also focus on mineral prospects and mines with dense pit and borehole data coverage in order to identify links between geology topography and weathering geology is closely linked to topography on the preglacial shield landscape of northern finland and both factors influence weathering patterns upstanding resistant granulite granite gabbro metabasalt and quartzite rocks were associated with fresh rock outcrops including tors or with thin fines values above 3000 and 4000 beneath valley floors developed along mineralised shear and fracture zones weathering penetrated locally to depths of 50 m and included intensely weathered kaolinitic clays with wip fines values below 1000 late neogene weathering profiles were varied in character tripartite clay gruss saprock profiles occur only in limited areas bipartite gruss saprock profiles were widespread with saprock thicknesses of 10 m weathering profiles included two discontinuities in texture materials and resistance to erosion between saprolite and saprock and between saprock and rock limited core recovery when drilling below the soil base in mixed rocks of the tana belt indicates that weathering locally penetrated deep below upper fresh rock layers such deep seated weathered bands in rock represent a third set of discontinuities incipient weathering and supergene mineralisation also extended to depths of 100 m in mineralised fracture zones the thin weathering crusts found extensively beneath till may represent types of early or middle pleistocene palaeosols we confirm that glacial erosion has been very limited

characteristics and palaeoenvironmental significance of relict sorted patterned ground drakensberg plateau southern africa abstract relict large sorted periglacial circles are described from the drakensberg plateau of southern africa morphological and sedimentological data for three populations of patterns occurring on high summit 3400 m a s l interfluves are presented the patterns range between 85 and 904 cm in diameter with centres encircled by primary and in some cases secondary borders patterns are sorted to maximum depths of 85 cm or more with borders occupying trough like depressions to a depth of 26 cm although it is found that contemporary freeze to 40 cm depth still permits some cryogenic activity within smaller patterns it is argued that the larger patterns are degrading owing to limited moisture and freeze duration and intensity the paper provides a literature summary of contemporary environmental parameters from 10 northern hemisphere localities where active relict large periglacial patterns occur findings suggest that patterns over 80 cm in diameter develop where the maat is 1 6 c or less it is demonstrated that the drakensberg palaeo maat reached such low temperatures during the lgm it is thus argued that the patterns developed during the lgm and that smaller varieties became reactivated during holocene cold phases the relict sorted circles provide confirmation for late quaternary permafrost above 3400 m a s l in southern africa the results further suggest pronounced palaeo climatic environmental variation over short spacial scales over southern africa s high plateau

k ar and 40ar 39ar geochronology of supergene processes in the atacama desert northern chile tectonic and climatic relations new k ar and 40 ar 39 ar data obtained for 29 samples of supergene alunite jarosite and hollandite group minerals from the central depression of northern chile document almost continuous supergene oxidation from 33 to 9 ma the downward migration of supergene oxidation zones is used to calculate maximum denudation rates of 16 35 m ma 1 these calculated rates are sensitive to pre existing topography and show that the present relief observed in the central depression represents a modified miocene landscape the results presented here are in good agreement with previously published geochronological data for the atacama desert the combination of all published data including the results presented here defines a continuous skewed distribution with a maximum between 21 and 14 ma the relative paucity of ages greater than 30 ma reflects the removal of supergene profiles by erosion during and immediately after the incaic compressive deformation from 29 to 9 ma supergene oxidation profiles were generated under semi arid conditions throughout the atacama region ages between 9 and 5 ma on the northern and southern margins of the desert mark the end of supergene oxidation processes consistent with a pliocene onset of present day hyperaridity

air temperature snow cover creep of frozen ground and the time of ice wedge cracking western arctic coast the time of ice wedge cracking is examined for several sites with young and old ice wedges along the western arctic coast the correlation between sharp air temperature drops and ice wedge cracking is highest where the snow cover is thin and least where the snow cover is thick the favoured duration and rate of a temperature drop that results in cracking is about 4 days at a rate of about 1 8 c d such temperature drops have a minimal effect in cooling the top of permafrost wherever there is an appreciable snow cover since short duration temperature drops often result in ice wedge cracking the thermal stresses that trigger cracking probably originate more within the frozen active layer than at greater depth in permafrost although most ice wedges tend to crack during periods of decreasing air temperatures about one third of those monitored have cracked during periods of increasing air temperatures long term measurements show that the active layer and top of permafrost move differentially all year in

direct dating of weathering phenomena by 40ar39ar and k ar analysis of supergene k mn oxides abstract potassium bearing manganese oxides cryptomelane k1 2 mn3 mn4 8 o16 xh2oand hollandite k ba 1 2 mn3 mn4 8 o16 xh2o are often authigenically precipitated in weathering profiles the presence of structural potassium in manganese oxides makes these minerals datable by the k ar and 40 ar 39 ar methods dating of these phases allows us to time the progression of oxidation fronts during weathering and pedogenic processes detailed age resolution of the weathering history allows us to use deep weathering profiles as land based stratigraphic records of past climatic and geomorphic events complementing evidence from the marine sedimentary and paleontological record potential problems in manganese oxide dating such as ar and or k losses excess argon 39ar loss by recoil during neutron irradiation contamination by primary minerals resistant to weathering the presence of multiple generations of manganese oxides and proportionately low radiogenic ar yield due to adsorbed atmospheric gases are addressed the k ar and 40 ar 39 ar analytical results indicate that ar and or k losses excess 40ar and 39ar recoil seem not to pose problems in manganese oxide dating this investigation suggests that fine scale laser probe 40 ar 39 ar technique is most appropriate for dating of weathering phenomena because this technique permits us to identify contaminating phases and the presence of multiple generations of weathering minerals in the inherently complex mineral assemblage characteristic of weathering profiles k ar and 40 ar 39 ar dating of supergene k bearing manganese oxides formed during lateritization of archean and proterozoic bedrocks in the caraj s region amazonia brazil indicates that weathering started before 72 6 ma petrographic electron microscope and electron microprobe investigation reveal multiple generations of manganese oxide precipitation k ar and 40 ar 39 ar laser probe step heating results independently confirm the presence of these various generations of manganese oxides age clusters at 65 69 51 56 40 43 33 35 20 24 12 17 ma and zero age 0 2 0 2 ma suggest episodic precipitation of k mn oxides resulting from changing weathering conditions in the amazon throughout the cenozoic k ar and 40 ar 39 ar dating of supergene cryptomelane from weathering profiles in eastern minas gerais southeastern brazil suggests continuous weathering from 10 to 5 6 ma ago possibly reflecting local climatic conditions due to the proximity with the atlantic ocean

permafrost thaw and destabilization of alpine rock walls in the hot summer of 2003 1 exceptional rockfall occurred throughout the alps during the unusually hot summer of 2003 it is likely related to the fast thermal reaction of the subsurface of steep rock slopes and a corresponding destabilization of ice filled discontinuities this suggests that rockfall may be a direct and unexpectedly fast impact of climate change based upon our measurements in alpine rock faces we present model simulations illustrating the distribution and degradation of permafrost where the summer of 2003 has resulted in extreme thaw we argue that hotter summers predicted by climate models for the coming decades will result in reduced stability of many alpine rock walls

luminescence dating applications in geomorphological research abstract chronological control remains critical to the interpretation of environmental change and to establishing long term rates of geomorphological processes radiocarbon dating will continue to be the central technique for age assessment of carbon bearing sediments deposited in the last ca 40 ka but alternative absolute dating strategies are required for older or non carbon bearing sediments they include uranium series dating of precipitated sediments k ar and ar ar dating of primary volcanic materials and cosmogenic isotopic dating of surface exposure ages an additional family of methods collectively termed luminescence techniques is increasingly providing a basis for the age assessment of detrital sedimentary deposits these methods directly date the deposition of detrital mineral grains typically quartz and feldspar and have been demonstrated to provide accurate deposition chronologies for up to 800 ka although 150 ka is more typical in the past decade a subset of luminescence techniques which employ optical sample stimulation methods called optical dating has made it possible to date samples from a much wider range of depositional systems given that the methods directly date sedimentation they allow direct assessment of depositional dynamism in numerous terrestrial and subaqueous including marine sedimentary systems and have demonstrated particular potential in the elucidation of chronologies from aeolian dune and loess fluvial colluvial coastal and volcaniclastic environments this paper provides a summary of the principles of the luminescence especially optical dating methods and shows how recent developments specifically single aliquot dating procedures have dramatically enhanced the scope and potential of the method the luminescence techniques are increasingly being incorporated into a wide range of geomorphological studies which seek to establish the nature of landscape changes over the past interglacial glacial cycle and beyond

climate and material controls on periglacial soil processes toward improving periglacial climate indicators one of the distinguished efforts of a l washburn was to reconstruct mean annual air temperature using periglacial features as climate indicators this paper reviews existing periglacial indicators and proposes a strategy to improve their thermal resolution based on recent periglacial process studies with a focus on solifluction and thermal contraction cracking and associated landforms structures landforms resulting from solifluction reflect both the depth subjected to freeze thaw and the thickness of frost susceptible soils the thickness of a solifluction structure can be used to infer the dominant freeze thaw regime and minimum seasonal frost depth ice wedge pseudomorphs have limited potential as a climate indicator because 1 they mainly reflect extreme winter temperatures 2 their thermal thresholds depend on the host material and 3 they need to be distinguished from frost wedges of other origin produced under different thermal and or material conditions monitoring studies of currently active ice wedges suggest that ice wedge cracking requires a combination of low temperature and large temperature gradients in the frozen active layer further field monitoring of periglacial processes and their controlling factors under various climate conditions and in various materials are needed however to improve the resolution of periglacial paleoclimate indicators

kaolinization a tool to unravel the formation and unroofing of the pleystein pegmatite aplite system se germany abstract the hagendorf pleystein pegmatite province se germany is known for the largest feldspar quartz pegmatite in central europe and renowned for its rare elements e g li nb and ta giving rise to a spate of exotic minerals mainly phosphates argillaceous rocks are scarce and eclipsed by the numerous mineralogical investigations on rare phosphates these phosphate pegmatites are for the first time subjected to a clay mineralogical study rendered possible by the newly discovered strongly kaolinized aplite near the kreuzberg quartz pegmatite at pleystein the supergene kaolin akin to the residual kaolin deposit at tirschenreuth se germany was analyzed for its major and minor elements by xrf and micro chemically by empa mineralogical investigations involved xrd ir spectroscopy thermoanalytical studies cec analyses and sem edx supergene kaolinization forms a repository for heavy minerals critical for the interpretation of the emplacement of the late paleozoic pegmatites as well as a matrix for pegmatite related trace elements and thereby may be used as an ore guide during exploration of these rare metal pegmatites the resultant kaolin is also the protagonist in the story of exhumation and destruction of a pegmatite by weathering and erosion irrespective of the strength of kaolinization nb ta ti heavy minerals can be identified in the regolith atop the host pegmatite or aplite and used for genetic interpretation of the primary mineralization and the origin of the felsic intrusive nb ta solid solution series s s s have to be treated cautiously because of the disposition of ta enriched nb ta oxide s s s to undergo corrosion in their tantalite lamellae more easily than in their niobium enriched zones kaolinization may alter the primary nb ta ratio but not to the extent that ta is released completely the most strongly kaolinized new aplite is the youngest member of a series of felsic intrusive rocks in the pleystein pegmatite aplite system the supergene kaolinization extending from the miocene through the pliocene can easily be correlated by minero stratigraphy with the larger tirschenreuth kaolin deposit the four stages established in the area furnish evidence of gradual alkalinization of the meteoric pore fluids throughout the neogene and the quaternary youngest stages are found at tirschenreuth the oldest regolith stage is present at pleystein

luminescence dating of quaternary sediments recent advances duller geoffrey 2004 luminescence dating of quaternary sediments recent advances journal of quaternary science 19 2 pp 183 192 rae2008

luminescence dating of loessic sediments from the loess plateau china loess palaeosol sequences from the loess plateau in china were investigated by combined infrared optically stimulated luminescence irsl and thermoluminescence tl dating techniques in order to study the luminescence properties of the loessic sediments and to provide a direct chronological link for correlation and position of the last interglacial soil in central asia and the loess plateau in china sensitivity changes were found for all samples through artificial bleaching of the samples the greatest sensitivity changes of up to 50 were found for very old loess samples designated to be older than the matu yama brunhes magnetic boundary and hence older than 788 000 1 800 years the upper dating limit as investigated by the very old loess samples ranges from 250 000 to 300 000 years if the tl additive dose method is applied the chronological position of the last interglacial soil s1 at the section near lanzhou indicates luminescence age estimates ranging from 82 000 to 75 000 years for the marine isotope stage 5 to 4 transition however the loess from below s1 yielded luminescence age estimates between 153 200 14 200 and 110 100 20 100 years for tl and irsl additive dose methods respectively thus a direct correlation between the s1 and the first intercalated pedocomplex pc1 in central asia is most likely