a short lived 26al induced hydrothermal alteration event in the outer solar system constraints from mn cr ages of carbonates abstract a key process in the early solar system that significantly affects the further evolution and transport of highly volatile elements throughout the solar system hydrothermal parent body alteration to determine whether hydrothermal alteration in outer solar system parent bodies occurred more or less simultaneously or due to a sequence of multiple different events we investigated low temperature hydrothermally altered cm and ci chondrites along with volatile rich cm like clasts and c1 clasts with abundant mineral phases that contain volatiles in this respect c1 clasts are particularly important as they closely resemble the ci chondrites but originate from isotopically different parent bodies specifically we applied the sims based mn cr in situ dating technique to carbonates a common hydrothermally formed phase in low temperature hydrothermally altered meteorites the mn cr ages of dolomites in ci chondrites and c1 clasts as well as calcites in cm chondrites and cm like clasts reveal that nearly all carbonates in low temperature hydrothermally altered clasts and chondrites were formed within a brief period between 2 6 ma after cai formation given this sharp separation and that hardly any material contains carbonates formed later than 6 ma after cai formation hydrothermal alteration likely occurred near contemporaneously among different parent bodies in the outer solar system further the timing of hydrothermal alteration matches peak heating of 26al decay that ceased at 5 ma after cai formation hereby these results are consistent with a model in which the carbonates in low temperature hydrothermally altered parent bodies precipitated from the fluid produced by melting ice the results also show that other potential heating events e g impacts only negligibly contributed to creating environments where fluid mediated dissolution and precipitation of carbonates was possible additionally the isotopic h o cr and s differences between c1 clasts and ci chondrites are most likely not caused by differences in timing of hydrothermal aqueous alteration and thus are best explained by spatially different isotopic reservoirs

late triassic charcoal from petrified forest national park arizona usa fossil charcoal has been found in the late triassic chinle formation in petrified forest national park a location that is world famous for its silicified tree trunks the material consists of charcoalified secondary wood and has sufficiently well preserved plant anatomy to show it may be described as araucarian type although it does display some minor differences from the anatomies described for the silicified gymnosperm trunks in the park the presence of the charcoal proves that on occasion natural wildfires most probably ignited by lightning must have occurred in the chinle triassic palaeoenvironments with resulting impacts on the biota of those times it is currently impossible to estimate how often these fires occurred as the incidence of charcoal here and in the whole fossil record apart from the frequency of ancient fires also reflects the preservation and burial conditions of the material there is scant mention of triassic charcoal in the literature a notable absence given the abundance of charcoal that has been recorded in the carboniferous jurassic and cretaceous periods this lack of charcoal may support the theory that atmospheric oxygen levels were lower during the triassic than in the carboniferous

early solar system events and timescale some recent information on the mn cr and al mg systems is reviewed this information is used to derive constraints on the timing of processes and events which took place in the early solar system using reasonable assumptions a timeline is constructed where the estimated age of the solar system is 4571 ma this age is taken to mark the time when most calcium aluminum rich inclusions cais were starting to form a process that may have lasted for several 105 years almost contemporaneously small planetesimals have accreted that served to store these cais for later dispersal among larger planetesimals by the time large numbers of planetesimals of several tens of kilometers in size had formed the interior of these objects started to melt through the decay of 26al collisional disruption of these planetesimals allowed gases dust and melt to escape into the surrounding space the fine droplets of melt reacted with gas and dust to form chondrules which after rapid cooling were partially re accreted onto the residual rubble pile this process of primary chondrule formation in most cases involving several generations of planetesimals most plausibly lasted only for 2 ma towards the end of this period and during the following 3 to 4 ma planetary objects of several hundred kilometers in size were formed they still stored enough energy to continue melting from the inside to finally differentiate into chemically stratified layers with basaltic volcanism occurring within a few million years

mn cr relative sensitivity factors for secondary ion mass spectrometry analysis of mg fe ca olivine and implications for the mn cr chronology of meteorites abstract secondary ion mass spectrometry sims is used to date meteoritic olivine using the 53mn 53cr short lived decay scheme this involves simultaneously measuring the cr isotope composition and mn cr ratio of a sample but the relative sensitivity of sims to cr and mn over a compositionally varying olivine matrix is poorly understood we have synthesized a range of olivine samples in mg fe ca space suitable for investigating mn cr relative sensitivity with particular application to olivine in angrites and secondary fayalite in oxidised carbonaceous chondrites these were analysed by sims using sensitive high mass resolution ion micro probe reverse geometry shrimp rg and laser ablation inductively coupled plasma mass spectrometry la icp ms to determine the relative sensitivity factors rsf necessary to correct sims 55mn 52cr to atomic 55mn 52cr we have found that rsf changes systematically as a function of the olivine matrix by several tens of percent apparently being controlled by fe content additionally the rsf values found in this study are considerably different from most of those previously reported a review of the literature shows that rsf for the mg rich san carlos olivine differs widely between studies and is probably controlled by sims instrumental settings our results show that the 55mn 52cr of olivine in some sims mn cr studies has been accurately determined e g for pallasites and angrites but for secondary fayalite in carbonaceous chondrites it has probably been underestimated if the relationship observed for our sims instrument holds true for others then the initial 53mn 55mn of these materials the abundance of 53mn with respect to 55mn at the time of crystallisation isotopic closure should be lower by a factor of 1 6 and ages should be 2 6 ma younger this would imply that the initial 53mn 55mn for secondary fayalites in carbonaceous chondrites is in the range 0 7 1 7 10 6 equating to an age of 4555 2 4559 9 ma relative to the precisely dated d orbigny angrite

high spatial resolution ion microprobe measurements refine chronology of carbonate formation in orgueil aqueous activity on meteorite parent bodies is indicated by the presence of carbonates high spatial resolution ion microprobe analyses of nine individual carbonate grains four dolomites five breunnerites from the orgueil meteorite reveal linear correlations between 53cr excesses and mn cr ratios in all grains indicative of in situ decay of radioactive 53mn half life 3 7 million years the well defined isochrons appear to have chronological significance if this is the case then 53mn 55mn ratios between 2 1 and 4 7 x 10 6 are inferred for the time of carbonate formation and absolute ages of between 4561 and 4565 ma are calculated systematic uncertainty of 2 ma dolomites tend to have formed slightly earlier than the breunnerites our data imply extensive aqueous activity on the orgueil parent body over a period of several million years starting 3 4 myr after formation of the solar system that most likely was the result of impact heating and latent heat from the decay of radioactive 26al and 60fe

multidisciplinary study of holocene archaeological soils in an upland mediterranean site natural versus anthropogenic environmental changes at cecita lake calabria italy abstract this paper highlights results of a multidisciplinary and multi analytical study of holocene archaeological soils around cecita lake sila massif calabria southern italy which represents a typical upland mediterranean environment it is focused on assessment of climatic and environmental changes that took place since late neolithic to roman times trying to discriminate natural from anthropogenic signals based on an integration of archaeological geomorphological stratigraphic pedological volcanological and soil charcoal pedoanthracological data the following paleoclimatic environmental reconstruction is proposed a warm and humid seasonally contrasted climate with an overall geomorphological stability suited for soil development characterized the late prehistoric environment holocene climatic optimum dominated by a widespread oak forest the main pedogenetic processes consisted in organic matter accumulation clay illuviation phyllosilicate and short range order mineral neogenesis from weathering of granite and volcanic ash sourced from late pleistocene holocene eruptions of the aeolian islands one or more mid holocene episodes of climate deterioration towards drier conditions indicated by a decrease of clay translocation processes and possible irreversible dehydration of poorly crystalline aluminosilicates into phyllosilicate clay minerals promoted intense land degradation this was in turn enhanced by increasing human activities for settlement and resource exploitation among which deforestation and ploughing for agriculture which led to a shift of the vegetation cover towards a dominant pine forest between 3 ka bp and the roman epoch humid and possibly cooler climatic conditions during the late holocene are indicated by the decrease of clay illuviation coupled with short range order components prevailing over phyllosilicate clays during roman soil formation

factors controlling late cenozoic continental margin growth from the ebro delta to the western mediterranean deep sea abstract the ebro continental margin sedimentation system originated with a messinian fluvial system this system eroded both a major subaerial canyon cutting the margin southeastward from the present ebro delta and an axial valley that drained northeastward down valencia trough post messinian submergence of this topography and the pliocene regime of high sea levels resulted in a marine hemipelagic drape over the margin late pliocene to pleistocene glacial climatic cycles drainagebasin deforestation and sea level lowstands combined to increase sediment supply cause the margin to prograde and create a regime of lowstand sediment gravity flows in the deeper margin the depositional patterns of regressive transgressive and highstand sea level regimes suggest that location of the sediment source near the present ebro delta throughout the late cenozoic southward current advection of sediment and greater subsidence in the southern margin combined to cause generally asymmetric progradation of the margin to the southeast thicker less stable deposits filling the messinian subaerial canyon underwent multiple retrograde failures eroded wide gullied canyons and formed unchanneled base of slope sediment aprons in the central margin area other margin areas to the north and south developed a series of channel levee complexes on the basin floor the formation of valencia valley over the messinian subaerial valley and earlier faults led to draining of about 20 of the ebro pleistocene sediment from channel levee complexes through the valley to prograde valencia fan as much as 500 km northeast of the margin thus the ebro margin has two growth directions mainly southeastward during higher sea levels and eastward to northeastward during lower sea levels the northeastward draining of turbidity currents has produced unusually thin and widely dispersed turbidite systems compared to those on ponded basin floors during the past few centuries man s impact has exceeded natural controls on ebro margin growth deforestation of the drainage basin more than doubled the normal holocene sediment supply and construction of dams then reduced the supply by 95 this reduction of the past 50 years has caused erosion of the delta and contamination of bottom sediment because normal holocene sediment discharge is not available to prograde the delta or help dilute pollutants

beginnings of olive cultivation in eastern spain in relation to holocene bioclimatic changes morphometric analyses show quantitative differences in anatomical characters of wood and charcoal between wild and cultivated olive samples from modern olive wood in eastern spain levante provide five distinctive anatomical criteria growth width ring vessel surface number of vessels per group vessel density and vulnerability ratio multivariate analysis shows that growth ring width and number of vessels per group are both significant criteria for discriminating between wild and cultivated olive moreover bioclimatic environments of wild olive thermomediterranean and mesomediterranean stages are distinguished by vessel density ancient olive charcoal from archaeological sites at valencia and alicante implies increasing aridification from the cardial neolithic to the roman period this pattern may reflect the onset of a mediterranean climate and human deforestation charcoal from cultivated specimens of early neolithic age shows that the olive tree is the earliest cultivated temperate fruit

evidence for mesozoic shear along the western kunlun and altyn tagh fault northern tibet china the strike slip faults of north tibet accommodate part of the cenozoic convergence between india and asia along the karakax valley south of yecheng and near the xidatan trough south of golmud the active traces of the altyn tagh and kunlun faults follow narrow belts of metamorphic rocks the deformation recorded in those mylonites is sinistral strike slip rb sr and 40ar 39ar ages of deformation from syntectonic fabrics formed at 350 400 c 120 ma argon loss suggests that deformation was associated to a 250 300 c thermal pulse that lasted 5 20 ma after the onset of movement unroofing occurred much later around 25 ma when sudden cooling suggests a component of thrusting or more likely normal faulting the cretaceous shear may be related to collision between the qiantang and the lhasa blocks the karakax and xidatan shear zones may have formed a unique continuous boundary in the cretaceous which was later reused by the tertiary strike slip faults leading to potentially calculable offsets along the altyn tagh fault

age and isotopic relationships among the angrites lewis cliff 86010 and angra dos reis results of a wide ranging isotopic investigation of the unique antarctican angrite lew 86010 lew are presented together with a reassessment of the type angrite angra dos reis ador the principal objectives of this study are to obtain precise radiometric ages initial sr isotopic compositions and to search for the erstwhile presence of the short lived nuclei 146sm and 26al via their daughter products the isotopic compositions of sm u ca and ti were also measured this allows a detailed appraisal to be made of the relations between and the geneology of these two angrites lew proves to be severely contaminated with modern terrestrial pb which is shown to result from terrestrial weathering nevertheless concordant pb pb model ages of pyroxene separates were obtained 2 4 55784 52 ga for lew and 4 55780 42 ga for ador uranium isotopic compositions are normal within error the inferred initial pb isotopic composition is within error of primordial pb as defined by canon diablo troilite because of the extreme upb ratios of both angrites this places an upper limit of 2 ma on the time between volatile element loss of the angrite parent body or its precursor planetesimals and the final crystallization of the angrites as differentiates initial 87sr86sr ratios were found to be indistinguishable in lew ador and the cumulate eucrite moore county the derived initial 87sr86sr for all three meteorites is 0 698970 15 2 a 147sm 143nd isochron for lew was obtained yielding an age of 4 553 34 ga with an initial 143nd144nd of 0 506682 49 2 146sm142nd isotope systematics were also measured anomalies on 142nd arising from extinct 146sm were clearly resolved resulting in an initial 146sm144sm of 0 0071 17 with nd142 2 57 0 62 at the time of isotopic closure both of these sm nd methods imply derivation of lew from a reservoir with chondritic smnd ratio they are also quite consistent with the previously reported systematics for ador overall the age and isotopic similarities between lew and ador are striking it suggests almost simultaneous production on the same asteroid even though recent experimental studies imply that the two are not comagmatic calcium and titanium do not exhibit enrichments in the n rich isotopes in contrast to cais making it unlikely that the angrite parent body is inherently rich in early condensates from the solar nebula no evidence was found for live 26al in lew when combined with the pb pb age and initial 87sr86sr data this firmly excludes 26al being an important heat source in the early solar system heat supplied for for example 1 the differentiation of the angrite and eucrite parent bodies and 2 metamorphism of the chondrite parent bodies must come from some other source the debate over live vs extinct 26al in the earliest solar system remains unresolved by this new data from lew however both the angrite and eucrite parent bodies have extremely low rbsr and high upb ratios compared to the solar nebula therefore the common initial 87sr86sr of 0 698970 can be firmly associated with the u pb angrite age above and the formation of both bodies this enables an absolute chronology of the early solar system to be established based upon 87sr86sr differences the oldest cais are a minimum of 11 4 ma older than the angrites i e 4 569 5 ga the age and isotopic constraints are discussed with respect to current collapse condensation and accretion timescales calculated for the solar nebula

charcoal recognition taphonomy and uses in palaeoenvironmental analysis abstract charcoal predominantly the product of wildfires is abundant in many sedimentary rocks deposited in a wide range of environments from terrestrial to marine it also occurs in some volcanic rocks this paper outlines aspects of charcoal formation both natural and experimental and briefly considers the taphonomic processes leading to a final assemblage this is done using examples from recent fires and through experimentation the ways in which charcoal assemblages are recognized in the field and extraction in the laboratory are also considered methods of charcoal identification are presented the range of charcoalified plant organs that can be found is discussed and a wide range of study methods outlined including light microscopy dark field light microscopy reflectance microscopy scanning electron microscopy and synchrotron radiation x ray tomographic microscopy emphasis in this paper is on the study of macro and meso charcoal above180 m finally there is a consideration of the broad use of charcoal from plant evolution studies fire history studies vegetation studies anatomical studies climate and atmospheric studies and the wider importance of charcoal for the earth and biological sciences charcoal is information rich but yet is an under utilized resource

thermochronology constraints for the propagation sequence of the south pyrenean basement thrust system france spain 1 in this work we combined apatite fission track and biotite k feldspar 40ar 39ar ages with tectonic data in the west central part of the axial zone of the pyrenees we discuss the exhumation ages and rates of the neouvielle bordere louron and bielsa variscan granites and their relationships with the timing and sequence of south vergent basement thrusting within the pyrenean orogenic prism the 40ar 39ar ages on k feldspars from the neouvielle massif sample nv7 seem to indicate tectonic movements on the eaux chaudes thrust during the early middle eocene fission track results suggest that the exhumation of the neouvielle massif occurred around 35 ma and exhumation of the bordere louron massif around 32 ma in relation to thrusting on the gavarnie thrust the bielsa massif was exhumed from around 19 ma by out of sequence movements on the bielsa thrust we thus show that whereas most of the pyrenean basement thrust faults here the eaux chaudes gavarnie and guarga thrusts were active in sequence toward the southern foreland from the early eocene to the earliest miocene some of them here the bielsa thrust were activated out of sequence in the hinterland later than the generally accepted aquitanian age for the end of the pyrenean compression finally the apatite fission track modeling indicate a last cooling episode starting around 5 ma which is most certainly related to the pliocene reexcavation of the southern and northern flanks of the pyrenees

mn cr relative sensitivity factor in ferromagnesian olivines defined for sims measurements with a cameca ims 1280 ion microprobe implications for dating secondary fayalite abstract the short lived radionuclide 53mn which decays to 53cr with a half life of 3 7 myr is useful for sequencing objects that formed within the first 20 myr of solar system evolution 53mn 53cr relative chronology enables aqueously formed secondary minerals such as fayalite and various carbonates in ordinary and carbonaceous chondrites to be dated thereby providing chronological constraints on aqueous alteration processes in situ measurements of mn cr isotope systematics in fayalite by secondary ion mass spectrometry sims require consideration of the relative sensitivities of the 55mn and 52cr ions for which a relative sensitivity factor rsf 55mn 52cr sims 55mn 52cr true is defined using appropriate standards in the past san carlos olivine fa 10 was commonly used for this purpose but a growing body of evidence suggests that it is an unsuitable standard for meteoritic fayalite fa 90 natural fayalite also cannot be used as a standard because it contains only trace amounts of chromium which makes determining a true 55mn 52cr ratio and its degree of heterogeneity very difficult to investigate the dependence of the mn cr rsf on ferromagnesian olivine compositions we synthesized a suite of compositionally homogeneous mn cr bearing liquidus phase ferromagnesian olivines fa31 99 manganese chromium isotopic measurements of san carlos olivine and synthesized ferromagnesian olivines using the university of hawai i cameca ims 1280 sims show that the rsf for fa10 is 0 9 it increases rapidly between fa10 and fa31 and reaches a plateau value of 1 5 0 1 for fa 34 the rsf is time dependent it increases during the measurements of olivines with fayalite content 50 the rsf measured on ferroan olivine fa 90 is influenced by pit shape whereas the rsf measured on magnesian olivine fa10 is less sensitive to changes in pit shape for these reasons 53mn 53cr systematics of chondritic fayalite fa 90 should be determined using standards of similar composition that are measured under the same analytical conditions as the unknown the 53mn 53cr ages of secondary fayalites fa90 100 in the elephant moraine eet 90161 l3 05 vicencia ll3 2 asuka 881317 cv3 and macalpine hills mac 88107 c3 chondrites 2 4 1 3 1 8 4 0 1 1 1 4 4 2 0 7 0 8 and 5 1 0 4 0 5 myrs after cv cais respectively are 3 myr older when using an rsf measured on a matrix matched fa99 standard rather than on a san carlos olivine the inferred 53mn 53cr ages of fayalite formation are consistent with the ages reported for calcites in cm chondrites measured with similarly matrix matched standards suggesting an early onset of aqueous alteration on the ordinary and carbonaceous chondrite parent bodies heated by decay of 26al

ca carbonate in the orgueil ci carbonaceous chondrite mineralogy microstructure and implications for parent body history the orgueil ci carbonaceous chondrite is a breccia and some of its constituent clasts contain ca carbonate grains whose mineralogy is undetermined but may yield new information on the history of its asteroidal or cometary parent body characterisation of one such clast shows that in addition to ca carbonate it contains magnetite olivine and orthopyroxene grains that are supported within a finely crystalline saponite serpentine ferrihydrite groundmass the ca carbonate grains are typically rounded less than 10 m in diameter and backscatter kikuchi patterns identify all those analysed as calcite electron backscatter diffraction orientation contrast maps show that most calcites have sub m sized e twins some of which are cut by corroded grain margins these microstructures demonstrate that the clast experienced very mild shock during aqueous alteration and probably accompanying impact gardening of the parent body regolith the sample studied hosts several other millimeter sized clasts and a fine grained clastic matrix that are free of ca carbonate olivine and orthopyroxene although can contain apatite dolomite and pyrrhotite within one of these clasts is a network of phyllosilicate magnetite veins that are inferred to have acted as fluid flow conduits during parent body aqueous alteration sulphur rich reaction rims within the same clast are likely to have formed during post fall remobilization and crystallization of pre terrestrial sulphates this study provides good evidence for alteration of the ci carbonaceous chondrites in a dynamic parent body regolith

nanosims isotopic investigation of xenolithic carbonaceous clasts from the kapoeta howardite abstract we report on the investigation of presolar grains and organic matter om in 14 xenolithic carbonaceous clasts c clasts identified in the kapoeta howardite based on high resolution nanosims hydrogen carbon nitrogen and oxygen isotopic imaging data the 14 c clasts are 50 200 m in size and consist of one cm like and 13 ci like clasts which are classified based on their mineralogies the clasts from this study are likely sourced from an ice bearing parent body either an icy asteroid or a comet originating from the outer solar system according to the following mineralogical observations 1 in two ci like clasts embayments of magnetite grains between the c clast and the host howardite point to aqueous alteration occurring on vesta as a result of melting the ice embedded in the c clasts 2 all of the c clasts especially the 13 ci like clasts likely originated from the same parent body because i the 14 c clasts are clustered in the thin section and ii the clasts show a much higher ratio of ci like to cm like clasts with respect to those reported in the literature four presolar silicon carbide sic and two presolar silicate grains were identified in the c clasts in addition all the c clasts contain moderate bulk d and 15n enrichments with the presence of sub micron to micron sized d and 15n hotspots indicating the presence of primitive organic material comparison of the abundances and isotopic compositions of presolar grains and om in these c clasts with literature data for different samples of primitive extraterrestrial material provides support for 1 the genetic linkage of xenolithic c clasts to highly aqueously altered but minimally heated carbonaceous chondritic materials and 2 a homogeneous distribution of circumstellar and interstellar materials in the protoplanetary disk the low amounts of heat experienced by the c clasts suggest that they arrived at vesta and or vestoids at low speeds after the late heavy bombardment in the inner solar system 3 5 4 0 gyr ago

carbonate compositions in cm and ci chondrites and implications for aqueous alteration abstract carbonate minerals in fourteen cm chondrites and two ci chondrites have been analyzed by electron microprobe to provide a better understanding of the aqueous processes that affected carbonaceous chondrite parent bodies calcites in cm chondrites and dolomites and magnesites in ci chondrites display the compositions expected of stable phases formed at low temperatures dolomites in cm chondrites identified here for the first time in five members of the group have small amounts of excess ca which may reflect metastable growth the distribution of fe between dolomite and coexisting serpentine differs in the two chondrite groups if the distributions reflect an approach to chemical equilibrium then the difference implies higher alteration temperatures for the ci group than the cm group in agreement with the results of previously published oxygen isotope thermometry and mineral solubility modeling of the alteration process dolomite fe contents are relatively uniform in the two chondrite groups dolomite mn contents by contrast vary widely the variations may reflect transport controlled coprecipitation of mn resulting from a heterogeneous distribution of the element in the anhydrous precursor material if this interpretation is correct then the altering fluids were essentially immobile while hydration reactions proceeded on the meteorite parent bodies the near closed system character of the alteration process long known from bulk chemical analyses of the meteorites is a direct consequence of the limited mobility of dissolved species

chondritic lithic clasts in the cb ch like meteorite isheyevo fragments of previously unsampled parent bodies the cb ch like chondrite isheyevo is characterized by the absence of fine grained interchondrule matrix material the only present fine grained material is found as chondritic lithic clasts in contrast to the pristine high temperature components of isheyevo these clasts experienced extensive aqueous alteration in an asteroidal setting hence the clasts are foreign objects that either accreted together with the high temperature components or were added later to the final isheyevo parent body during regolith gardening in order to constrain the origin and secondary alteration of the clasts in isheyevo we studied their mineralogy petrography structural order of the polyaromatic carbonaceous matter and oxygen isotopic compositions of carbonates three main groups of clasts were defined based on mineralogy and petrology group i clasts consist of phyllosilicates carbonates magnetite and lath shaped fe ni sulfides group ii clasts contain different abundances of anhydrous silicates embedded in a hydrated matrix sulfides magnetite and carbonates are rare with only a few exceptions groups i and ii clasts did not experienced significant thermal metamorphism group iii clasts are characterized by the absence of magnetite and the presence of fe ni metal in addition to aqueous alteration they experienced thermal metamorphism as reflected by the structure of their polyaromatic carbonaceous matter while there are some similarities between the isheyevo clasts ci chondrites and the matrices of cm and cr chondrites on the whole the characteristics of the clasts do not match those of any of these aqueously altered meteorite classes nor do they match those of similar material in various types of chondritic clasts present in other meteorite groups we conclude that the isheyevo clasts represent fragments of previously unsampled parent bodies

the organic geochemistry of coal from plant materials to coal coalification is a process that transforms plant remains under the influence of time temperature and possibly pressure to a black generally lustrous solid organic fossil fuel having a very complex chemistry although much has been learned in the past two centuries on coal chemistry we still have little knowledge of the way plant materials undergo these transformations the problem has been the existence of adequate characterization tools the advent of some new tools for structural elucidation of macromolecules has led to some revised thinking on coalification originally thought to be a process involving the full degradation of plant remains and subsequent reconstitution of these remains the general consensus today is that the process involves a selective preservation of certain resistant plant components followed by some minor reorganization of the biopolymers that survive the major components of plants do degrade and the resistant ones often constitute only a small fraction of the original mass of the plant materials this paper examines the most recent literature concerning coalification and focuses on the chemistry associated with coalification of certain recognizable plant remains that have been at the center of research activity for the past two decades thus we examine the recent knowledge of the chemistry of resistant biopolymers in extant and fossil wood cuticles resins spores and algae knowledge that has been assembled to establish the reaction pathways towards coal macromolecules

interdisciplinary interpretation of challenging archives charcoal assemblages in drina valley alluvial and colluvial sediments jagnilo bosnia and herzegovina in connection to an archaeological project in bosnia and herzegovina charcoal fragments from several geomorphological profiles were analysed due to the lack of other archives for palaeoenvironmental reconstruction the major aim of the presented study was to systematically test the suitability of the documented colluvial and alluvial layers for charcoal analysis the profiles uncover main phases of sedimentation of drina valley holocene alluvial sedimentation and for the first time provide anthracological data from the area giving initial insight into the vegetation of the catchment areas and into dynamics of the drina for the late holocene the presence of several genera in the catchment areas of the investigated profiles was documented the most important genera are quercus and ostrya carpinus type fagus acer and pinus are also present light demanding genera such as corylus and the maloideae group indicate human activities alluvial elements such as ulmus fraxinus and alnus are present a major advantage of this investigation is the distinction of catchment areas for alluvial and colluvial layers by the means of charcoal analysis this interdisciplinary cooperation of botanists geoscientists and archaeologists yields new information about a rarely investigated region of southeastern europe and thus improves understanding of natural processes and human impact

evolution of a turbiditic foreland basin and analogy with an accretionary prism example of the eocene south pyrenean basin the south pyrenean tertiary basin was an east west trending foreland trough which developed from early eocene to miocene times in a north south trending compressive regime a turbiditic series of lower and middle eocene age hecho group enables us to define the typical features of the tectono sedimentary evolution of the basin 1 slope and shelf derived carbonate turbidites and megaturbidites bear witness to the seismic activity of the basin borders 2 the southern basin border evidenced by the onlap of the turbidites onto slope and shelf deposits migrated progressively southwards in time and 3 the deformation pattern is characterized in the meso cenozoic sediments by a complex thrust fold system of thin skinned tectonics style its specific geometry and kinematics were influenced by the pre deformation geometry onlap this thrust fold system is related to south directed basement nappes and its front advanced progressively southwards in time from this data we infer an evolutionary model for this highly mobile basin it was a flexural basin linked to the northward bending of the lithosphere in the foreland of a south directed crustal accretionary prism as the nappes advanced the basin migrated progressively southwards in the foreland direction as for the actual basin evolution many analogies with accretionary prism trench systems of active margins exist

mn cr systematics in primitive meteorites insights from mineral separation and partial dissolution abstract cr isotopic compositions have been measured on carbonaceous chondrites cc tafassasset paris niger i nwa 5958 nwa 8157 and jbilet winselwan in bulk samples the 54 cr 52 cr ratios expressed as e 54 cr range from 0 93 to 1 58 e units these values are in agreement with values characteristic for distinct petrologic types despite this 54 cr heterogeneity the variability in the 53 cr 52 cr ratios expressed as e 53 cr of 0 2 e units and the mn cr ratios is consistent with the previous finding of an isochron in the mn cr evolution diagram the mn cr ratio in cc corresponds to variable abundances of high t condensate formed and separated at the beginning of the solar system thus the canonical 53 mn 55 mn ratio can be defined based on a consistent chronology for u pb and mn cr between the earliest objects formed in the solar nebula and the d orbigny angrite we define a canonical 53 mn 55 mn ratio and e 53 cr i of 6 8 10 6 and 0 177 respectively the internal mn cr systematics in tafassasset and paris were studied by two approaches leaching technique and mineral separation despite variable e 54 cr values up to 30 e linear co variations were found between e 53 cr and mn cr ratio the mineral separates as well as the leachates of tafassasset fall on a common isochron indicating that 1 cooling of the tafassasset s parent body occurred at 4563 5 0 25 ma and that 2 54 cr is decoupled from the other isotopes even though temperatures 900 c have been reached during metamorphism in the case of paris the leachates form an alignment with a 53 mn 55 mn ratio higher than the canonical value this alignment is not an isochron but rather a mixing line based on leachates from various cm and ci we propose the occurrence of three distinct cr reservoirs in meteoritic material pure54 high53 and low53 characterized by a e 53 cr and e 54 cr of 0 and 25 000 2 17 and 8 and 0 5 and 151 respectively pure54 has already been described and is carried by highly refractory nano spinel high53 is mn rich and most probably carried by sulfides in the matrix whereas low53 is characterized by low mn cr ratios and it is sensitive to metamorphism this component could correspond to mineral phases such as refractory oxides and carbide variable mixing proportions of high53 and low53 would explain the larger than expected uncertainty mswd of 5 5 on the cc bulk regression line a monte carlo simulation allows us to evaluate the impact of the dispersion of the initial cr isotopic ratios as a function of variable high53 the co variation of the mn cr ratio and the e 53 cr defined by the mineral separates from paris corresponds to an age of 4566 44 0 66 0 75 ma while their e 54 cr still differ by at least 0 42 e this age is likely to date the segregation of forsteritic olivines most probably from type i chondrules from fayalitic olivines from type ii chondrules and given the sampling procedure by handpicking of hundreds of grains corresponds to the average age of chondrule formation

ion microprobe analysis of trace elements in calcite with an application to the cathodoluminescence zonation of limestone cements from the lower carboniferous of south wales u k ion microprobe analysis offers high spatial resolution 10 m and low detection limits for many elements in calcite detection limits are likely to be instrument dependent the values given here are specific to the instrument used a modified aei im 20 and more recent instrument designs should give lower detection limits li na and k signals have been observed and detection limits are estimated to be 10 ppm the detection limit for pb is in the range 10 50 ppm zn and ba suffer from significant molecular interferences which impose higher detection limits mg fe mn and sr were standardised against three chemically analysed calcites detection limits in the range 1 5 ppm were obtained for mg mn and sr but fe is subject to interference by a hydride species so that the detection limit is determined by vacuum conditions calcite cements in sections cut from a lower carboniferous limestone from south wales can be divided texturally into four zones analyses were made for mg fe mn and sr only sr differs among the zones mn is the main activator of cathodoluminescence cl in these cements when the fe content is up to 1600 ppm there is a positive relationship between cl intensity and mn content fe acts as a suppressor of cl intensity for a given mn concentration the cl intensity decreases as the fe content increases for fe contents 1600 ppm the cl intensity may be negatively related to the mn concentration when the mn content is below 125 150 ppm the fe content has little discernible effect on the cl intensity in these cements non luminescence can only be predicted with confidence if the mn concentration is below 25 ppm there is no critical concentration of fe up to 7000 ppm or critical fe mn ratio in the range 0 26 which always causes mn bearing locations to become extinct with respect to cl the present data are compared with those from the literature and a diagram is constructed which represents the region of fe mn composition space where luminescence can occur conflicting evidence regarding the relative importance of fe mn ratio and absolute fe and mn concentrations can be reconciled both concentrations and fe mn ratio are involved in controlling luminescence

a detailed pyrolysis gc ms analysis of a black carbon rich acidic colluvial soil atlantic ranker from nw spain abstract despite the potentially large contribution of black carbon bc to the recalcitrant soil organic matter pool the molecular level composition of aged bc has hardly been investigated pyrolysis gc ms which provides structural information on complex mixtures of organic matter was applied to the naoh extractable organic matter of an acidic colluvial soil atlantic ranker sampled with high resolution 5 cm that harbours a fire record of at least 8 5 ka additionally 5 charcoal samples from selected soil layers were characterised using pyrolysis gc ms for comparison pyrolysis gc ms allowed distinguishing between bc and non charred organic matter it is argued that a large proportion of the polycyclic aromatic hydrocarbons pahs benzenes and benzonitrile in the pyrolysates of the extractable organic matter together accounting for 21 54 of total identified peak area derived from bc in charcoal samples these compounds accounted for 60 98 of the pyrolysis products the large quantity of bc in almost all samples suggested a key role of fire in holocene soil evolution the high c content of the soil up to 136 g c kg 1 soil may be attributed to the presence of recalcitrant organic c as bc in addition to the sorptive preservation processes traditionally held responsible for long term c storage in acid soils interactions between reactive al hydroxides and bc could explain the longevity of bc in the soil this work is the first thorough pyrolysis gc ms based study on ancient fire affected organic matter

reexamination of anomalous i xe ages orgueil and murchison magnetites and allegan feldspar abstract the extremely old i xe ages of orgueil and murchison magnetites difficult to integrate into conventional meteorite evolutionary models are not confirmed new measurements indicate that orgueil magnetite is 3 ma younger than the shallowater reference sample rather than 7 ma older as previously reported by lewis and anders 1975 if these differences are due to difficulties with the irradiation monitors in the earlier studies there are wider implications because the same ki monitor was used to establish the i xe age of murchison magnetite which is used in turn as a reference sample in many subsequent i xe studies confirmation of these new results and a careful review of existing i xe age data are therefore in order the old i xe age of allegan feldspar reported by brazzle et al 1999 may also be an artifact of shock disturbance

extended chronologies of aqueous alteration in the cm2 carbonaceous chondrites evidence from carbonates in queen alexandra range 93005 abstract the antarctic cm2 carbonaceous chondrite que 93005 contains four compositionally distinct carbonates namely breunnerite calcite dolomite and a ca poor dolomite these carbonates can form monomineralic grains or may be intergrown as bimineralic grains consisting of dolomite plus breunnerite and dolomite plus calcite or polymineralic grains containing an intergrowth of breunnerite ca poor dolomite and calcite carbonates in all grain types have inclusions of fe ni sulphides and or mg fe phyllosilicates in the bimineralic grains dolomite crystallised first to be overgrown by breunnerite or partially replaced by calcite polymineralic grains are concentrically layered with breunnerite crystallising first on pore margins to be later etched then overgrown and partially replaced by ca poor dolomite that was itself partly dissolved prior to being overgrown by calcite calcite and dolomite have also cemented fractures that cross cut the fine grained rims to aqueously altered chondrules and were formed by expansion of the chondrules during their hydration overall the sequence of mineralisation in que 93005 was 1 dolomite 2 breunnerite 3 ca poor dolomite then 4 calcite this secular change in carbonate composition and mineralogy reflects changing solution composition and probably also provenance mg fe phyllosilicates replaced dolomite breunnerite and ca poor dolomite prior to calcite crystallisation and most or all of the sulphides formed after both the phyllosilicates and calcite following sulphide crystallisation the edges of carbonate grains were abraded either by impact gardening or as a consequence of fluidisation of the matrix during rapid loss of gas or vapour determination of the crystallisation age of dolomite via the mn cr system indicates that aqueous alteration of que 93005 began on or before 3 93 0 23 ma after the formation of the oldest solar system solids overall the water rock ratio and fo2 during alteration of que 93005 was similar to that of the cm1s and cr1s but the lower degree of alteration of que 93005 overall suggests that alteration timescales were shorter possibly due to loss of intergranular liquid water during fluidisation

the anso transect of the southern pyrenees basement and cover thrust geometries a balanced geological section through the western central pyrenees allows the alpine geometry of hercynian basement to be determined this shows marked differences with other transects of the southern part of the chain basement involved thrust sheets do not form an antiformal stack but are imbricated and define steps separated by frontal culmination limbs basement thrusts propagate upwards and have formed distinct thrust systems in the cover in this transect the north pyrenean zone is bounded to the south by gently dipping thrusts of large displacement and the axial zone massif at its western termination area is a flat topped culmination caused by a single thrust fault the gavarnie thrust this thrust emerges to the south in the interior of the syntectonic jaca basin the geometry of which is also controlled by underlying basement thrusts various generations of structures can be correlated with distinct episodes of syntectonic sedimentation a sequential restoration of the section illustrates how successive foreland sedimentary wedges were generated and progressively involved in deformation tectonic shortening is 48 km almost half of that estimated further to the east for the southern pyrenees the structure deduced at the ecors pyrenees seismic section cannot be translated to this transect

anthracology and taphonomy from wood gathering to charcoal analysis a review of the taphonomic processes modifying charcoal assemblages in archaeological contexts abstract a discussion on the representativeness of charcoal from archaeological contexts and their potential for palaeoecological reconstruction is presented the charcoal deposits studied are the result of human activities and natural processes difficult to separate on the basis of their effects only this is why taphonomy should not be limited to the study of charcoal after the extinction of fire as a result our questioning has been widened to include the entire succession of processes from past vegetation to the anthracological diagram we propose a review of the taphonomic processes affecting anthracological assemblages in archaeological contexts from wood gathering to the analysis of charcoal results human practices appear clearly as the first filter determining or conditioning the assemblage the combustion process can induce a double filter by limiting the taxonomic information and by falsifying the initial quantity of burned wood post depositional agents represent a third level of filters between the vegetation and the anthracological assemblage finally sampling and quantification methods can also induce a distortion of the assemblage the aim of this paper is to present the state of the discipline today the problems already solved and the questions that remain to be studied

characterization and palaeoecological significance of archaeological charcoal assemblages during late and post glacial phases in southern france abstract archaeological sites at abeurador and font juvenal have produced extensive charcoal rich horizons the results of the charcoal analysis based on the identification of woody species from anatomical features contribute to the elaboration of plain phases within the development of vegetation in southern france they are presented here in a new diagram and are interpreted as four major vegetation phases from 11 000 14 c yr b p to the recent past in order to interpret the palaeoecological significance of the charcoal assemblages we have used multivariate analysis the data base consists of 42 taxa and 48 archaeological levels the division into four vegetation phases based on analytical interpretation is complemented by the more synthetic interpretation based on correspondence factor analysis cfa the results reveal the patterns of the vegetation history over the last 11 millennia each being characterized by a key plant species

reconstruction of the palaeoenvironment and anthropogenic activity from the upper pleistocene holocene anthracological records of the ne iberian peninsula barcelona spain abstract this paper presents the results of anthracological analyses conducted to further the palaeoenvironmental reconstruction of ne iberia and to provide better insights into the impact of human activity on the landscape this study is based on the analysis of charred plant remains from five archaeological sites located 20 km to the southwest of the city of barcelona the site chronology spans from the upper pleistocene to the mid holocene the mis 5 stage is represented by the cova del rinoceront ca 74 175 ka which yielded scarce anthracological remains composed primarily of angiosperms mis 3 and the hs4 stadial are represented by the cova del coll verdaguer ca 33 4 55 ka and the terrasses de la riera dels canyars 39 6 ka cal bp respectively both pointing to the recurrent presence of pinus sylvestris type the holocene record is represented by the cova bonica ca 7200 4600 cal bp presenting a predominance of quercus pinus and a considerable variability of shrubs and small tree types finally cal maurici ca 6100 3700 cal bp constitutes a natural deposit in shallow marshes and presents charcoals washed down the river the sequence presented is completed and compared with other sequences located in ne iberia the assemblages allow us to evaluate the evolution and transformation of the forested landscapes originated by the climate variations that occurred during the upper pleistocene and holocene and to assess changes in the woody vegetation resulting from cultural or natural transformations these outcomes are discussed in terms of a comparison of natural vs anthropogenic anthracological records and the data are contextualized and examined in the broader context of the other assemblages recovered in the ne iberian peninsula

53mn 53cr dating of aqueously formed carbonates in the cm2 lithology of the sutter s mill carbonaceous chondrite radiometric dating of secondary minerals can be used to constrain the timing of aqueous alteration on meteoritic parent bodies dolomite is a well documented secondary mineral in cm chondrites and is thought to have formed by precipitation from an aqueous fluid on the cm parent body within several million years of accretion the petrographic context of crosscutting dolomite veins indicates that aqueous alteration occurred in situ rather than in the nebular setting here we present 53mn 53cr systematics for dolomite grains in sutter s mill section sm51 1 the mn cr isotope data show well resolved excesses of 53cr correlated with 55mn 52cr ratio which we interpret as evidence for the in situ decay of radioactive 53mn after correcting for the relative sensitivities of mn and cr using a synthetic mn and cr bearing calcite standard the data yield an isochron with slope corresponding to an initial 53mn 55mn ratio of 3 42 0 86 10 6 the reported error includes systematic uncertainty from the relative sensitivity factor when calculated relative to the u corrected pb pb absolute age of the d orbigny angrite sutter s mill dolomites give a formation age between 4564 8 and 4562 2 ma 2 4 5 0 myr after the birth of the solar system this age is contemporaneous with previously reported ages for secondary carbonates in cm and ci chondrites consistent carbonate precipitation ages between the carbonaceous chondrite groups suggest that aqueous alteration was a common process during the early stages of parent body formation probably occurring via heating from internal 26al decay the high precision isochron for sutter s mill dolomite indicates that late stage processing did not reach temperatures that were high enough to further disturb the mn cr isochron

wood charcoal analysis at riwi cave gooniyandi country western australia abstract wood charcoals excavated from archaeological sites provide a useful tool for palaeoenvironmental reconstruction particularly in arid and semi arid zones where suitable catchments for palynological archives are often limited preservation of organic material in northern australia is characteristically poor and wood charcoal analysis provides a viable alternative to understand shifts in woody vegetation in the past the analysis of charcoal from matrix contexts at riwi cave located in the southern kimberley region of northern western australia has allowed a reconstruction of the local woody vegetation during occupation over the last 45 000 years the wood charcoal assemblage from the holocene stratigraphic units reflects the composition of the modern vegetation and illustrates that people were occupying the site during periods of relative humidity the pleistocene stratigraphic units show a shift in vegetation composition from eucalyptus spp to corymbia sp dominated savanna with an understory of secondary shrub associated with a late mis 3 arid event observed in both terrestrial and marine archives suggesting that activities continued at riwi during this arid event further anthracological analysis of other sites in the kimberley will help to build a regional picture of woody vegetation change and will further disentangle local and regional climatic signals particularly in relation to phases of occupation

iodine xenon analysis of ordinary chondrite halide implications for early solar system water we report the results of iodine xenon analyses of irradiated halide grains extracted from the h chondrite monahans 1998 and compare them with those from zag whitby et al 2000 to address the timing of aqueous processing on the h chondrite parent body xe isotopic analyses were carried out using the relax mass spectrometer with laser stepped heating the initial 129i 127i ratio in the monahans halide was determined to be 9 37 0 06 10 5 with an iodine concentration of 400 ppb significant scatter especially in the zag data indicates that a simple interpretation as a formation age is unreliable instead we propose a model whereby halide minerals in both meteorites formed 5 ma after the enstatite achondrite shallowater at an absolute age of 4559 ma this age is in agreement with the timing of aqueous alteration on the carbonaceous chondrite parent bodies and ordinary chondrite metamorphism and is consistent with the decay of 26al as a heat source for heating and mobilisation of brines on the h chondrite parent body post accretion surface impact events may have also contributed to the heat source

mn cr ages of dolomites in ci chondrites and the tagish lake ungrouped carbonaceous chondrite abstract 53 mn 53 cr ages have been measured for dolomites in three ci chondrites and an ungrouped c2 chondrite tagish lake for an accurate age determination we utilized in contrast to previous works a matrix matched carbonate standard to appropriately correct the observed mn cr ratios the mn cr data of the dolomites most likely represent isochrons with chronological significances and the obtained ages are concentrated in 4563 8 4562 5 million years ago 4 4 5 7 million years after the birth of the solar system the ages of the ci and tagish lake dolomites are very similar to those of carbonates in cm chondrites although ci and cm chondrites are likely to have different alteration histories the similar carbonate ages in various carbonaceous chondrites suggest that the aqueous activities in hydrous asteroids initiated almost concurrently if this is the case the most plausible heat source for the aqueous alteration is the decay energy of short lived radionuclides especially 26 al we carried out a model calculation for the thermal history of the ci chondrite parent body assuming that 26 al is the dominant heat source by two different approaches to estimate the accretion time of the ci chondrite parent body we conclude that it accreted 3 0 3 9 million years after the birth of the solar system this is also likely to be the case for the cm chondrite and tagish lake parent bodies because the result of the calculation is not sensitive to the ice abundance therefore we stress that near the condensation front of water ice meteorite parent bodies with abundant ice accreted almost simultaneously at 3 4 million years after cai formation combining our mn cr ages of the dolomites with those of breunnerites reported previously the youngest one is 4554 6 million years ago we found that the aqueous alteration in the ci chondrite parent body lasted for at least 9 million years therefore the parent body should be large enough 50 km in radius so that the internal heat had been kept for 9 million years

53mn 53cr systematics of carbonates in cm chondrites implications for the timing and duration of aqueous alteration abstract cm chondrites contain carbonates and other secondary minerals such as phyllosilicates sulfides sulfates oxides and hydroxides that are believed to have formed by aqueous alteration reactions on their parent asteroid we report in situ mn cr isotope measurements in the highly aqueously altered cm2 1 chondrites que 93005 and alh 83100 using secondary ion mass spectrometry cameca ims 1270 ion microprobe the 53 cr excesses are correlated with the 53 mn 55 mn ratio and result from the in situ decay of 53 mn a short lived radioisotope with a half life of 3 7 ma if we assume that carbonate grains in samples que 93005 and alh 83100 are cogenetic then the excesses define initial 53 mn 55 mn ratios 53 mn 55 mn 0 of 4 1 1 2 10 6 and 5 1 1 7 10 6 respectively these values are comparable to those in carbonates from other cm chondrites as reported in the literature initial 53 mn 55 mn ratios for calculated model isochrones for individual carbonate grains range from 3 8 1 4 10 6 to 4 8 2 1 10 6 for que 93005 and from 3 1 1 6 10 6 to 1 3 0 5 10 5 for alh 83100 a possible interpretation for the ranges in 53 mn 55 mn 0 could be that alteration in individual cm chondrites was episodic and occurred over an extended period of time however isochrones based on the entire set of carbonate grains in each of the cm chondrites imply that the degree of aqueous alteration is roughly correlated with the age of carbonate formation in cm chondrites of different subtypes and that alteration on the cm parent asteroid started contemporaneously with or shortly after cai formation and lasted at least 4 ma

a review of charcoal analysis as a tool for assessing quaternary and tertiary environments achievements and limits abstract identification of charcoal fragments 2 mm using reflected light microscopy is routinely carried out to study former natural ecosystems assess changes in vegetation communities over time and identify the influence and patterns of behaviour of human populations on vegetation material studied comes either from archaeological horizons or soil profiles despite undeniable limits informative results have been obtained in the last 25 years mostly in southwestern europe where charcoal analysis has been widely applied in quaternary studies examples of these achievements are provided focusing on the major vegetation trends since the upper palaeolithic to the middle ages the techniques used for charcoal analysis in the reconstruction of quaternary vegetation are now being used to study tertiary charcoal and lignites the study of fossil charcoal can be a highly informative method for interpreting ancient ecosystems as species easily degraded may be preserved by charcoalification some results from the lower rhine embayment germany are presented here

the i xe chronometer and the early solar system we review the development of the i xe technique and how its data are interpreted and specify the best current practices individual mineral phases or components can yield interpretable trends in initial 129i 127i ratio whereas whole rock i xe ages are often hard to interpret because of the diversity of host phases many of which are secondary varying standardizations in early work require caution only samples calibrated against shallowater enstatite or bjurble can contribute reliably to the emerging i xe chronology of the early solar system although sparse data for which i xe and mn cr can be compared suggest that the two systems are concordant among ordinary chondrite samples we derive a new age for the closure of the shallowater enstatite standard of 4563 3 0 4 myr from the relationship between the i xe and pb pb systems this yields absolute i xe ages and allows data from this and other systems to be tested by attempting to construct a common chronology of events in the early solar system absolute i xe dates for aqueous and igneous processes are consistent with other systems consideration of the i xe host phases in cais and dark inclusions demonstrates that here the chronometer records aqueous alteration of pre existing material the ranges of chondrule ages deduced from the al mg and i xe systems in semarkona ll3 0 and chainpur ll3 4 are consistent chainpur i xe data exhibit a greater range of ages than semarkona possibly reflecting a greater degree of parent body processing however individual chondrules show little or no evidence of such processing determining the host phase s responsible for high temperature correlations may resolve the issue

woodland history in the upper harz mountains revealed by kiln site soil sediment and peat charcoal analyses charcoal is abundant in various soils and soil sediments and is basically the result of either natural wildfires or of anthropogenic ignition compositions of charcoal assemblages are the result of several taphonomical processes beside this little is known about the influence of charcoal from anthropogenic origin like charcoal production sites kiln sites on soil charcoal assemblages to elucidate how human charcoal production as well as erosion of the relicts of kiln sites influenced charcoal assemblages in soils and mires a multi proxy approach was applied at two transects on the renneckenberg a steep slope in the low mountain range harz germany on this slope three types of archives soil soil sediments kiln sites and peatland were investigated each with different methods on a local scale soil charcoal analyses kiln site charcoal analyses peat macro micro charcoal and pollen analysis the kiln site charcoal records are taxonomically richer in wood taxa than those from colluvial assemblages especially regarding deciduous tree species fagus sylvatica and acer sp are rare or absent in the colluvial charcoal assemblages which are dominated by picea charcoal at the bottom of the slope the soil charcoal concentration is very high and indicates strong erosion of charcoal from the upper part of the slope significant taxonomical discrepancies between the colluvial and the kiln site charcoal assemblages may be related to different fire intensity throughout the holocene and to human woodland usage additionally changes in the run off intensity and fire frequency are detected in the peat macro charcoal record reflecting vegetation change in the early holocene the micro charcoal content coincides with the main mining phases in the late holocene and the 9 2 k climatic anomaly

origin of the highly elevated pyrenean peneplain 1 peneplanation of mountain ranges is generally considered the result of long term erosional processes that smooth relief and lower elevation near sea level therefore peneplain remnants at high elevation in mountain ranges are used to infer posttectonic surface uplift such an interpretation has been proposed for the pyrenees where high elevation low relief erosional surfaces rose up to more than 2000 m because the pyrenean foreland basins are filled with very thick continental deposits which have buried the early jagged landscape we challenge this hypothesis by pointing out that relief applanation does not necessarily require elevation lowering we propose an alternative interpretation in which piedmont aggradation of detrital sediment that comes from erosion of the high chain induces the rise of the base level of the range therefore reducing strongly the erosive efficiency of the drainage system and resulting in the progressive smoothing of the relief such a process allows a high elevation low relief erosional surface to develop at the scale of the range in the pyrenees occurrence of high elevation low relief erosional surface remnants does not imply a posttectonic uplift but is instead due to the dissection of the initial miocene high elevation low relief surface by the recent drainage system the erosive activity of which has been enhanced by global climate change from the late pliocene onward

syntectonic burial and post tectonic exhumation of the southern pyrenees foreland fold thrust belt in the oligocene to earliest miocene the entire southern pyrenean foreland fold and thrust belt was backfilled and buried in up to 3 km of syntectonic continental conglomerates from the range9s own erosional debris then starting in the mid to late miocene the pyrenees were exhumed by erosional excavation to their present relief a model is proposed for this unusual development whereby late eocene oligocene tectonic uplift of the margins of the ebro basin raised local base level and blocked normal dispersal of erosional debris to adjacent oceans thus causing the basin to fill then backfill northwards across the entire southern flank of the pyrenees subsequent miocene rifting of the catalan mediterranean margin and the messinian salinity crisis lowered base level allowing the ebro river to cut headward capture the ebro basin and re excavate the pyrenees

53 mn 53 cr radiometric dating of secondary carbonates in cr chondrites timescales for parent body aqueous alteration abstract we present 53mn 53cr ages of secondary carbonates in renazzo like cr chondrites determined by secondary ion mass spectrometry the timing of aqueous alteration in cr chondrites has been unconstrained in the literature we measured 53mn 53cr isotope systematics in carbonates from three different cr chondrite lithologies calcite in the interchondrule matrix of renazzo calcite in the matrix of gro 95577 and dolomite in a dark inclusion of renazzo all show excesses in 53cr interpreted as the daughter product from the decay of 53mn the renazzo calcite yields an initial ratio of 53mn 55mn 0 3 6 2 7 10 6 and the renazzo dark inclusion dolomite ranges from 53mn 55mn 0 3 1 1 4 10 6 corrected to the rsf of a calcite standard to 3 7 1 7 10 6 corrected to an inferred dolomite rsf when anchored to the d orbigny angrite the renazzo carbonates yield ages between 4563 6 and 4562 6 ma or 4 3 5 3 myr after the formation of cv cais calcite measured in the heavily altered specimen gro 95577 yields a shallower slope of 53mn 55mn 0 7 9 2 8 10 7 corresponding to a much younger age of 4555 4 ma or 12 6 myr after cai formation the two renazzo ages are contemporaneous with mn cr ages of carbonates in tagish lake ci and cm chondrites but the gro 95577 age is uniquely young these findings suggest that early aqueous alteration on chondritic parent bodies was a common occurrence likely driven by internal heating from 26al decay after accretion the young carbonate ages of gro 95577 suggest that either the cr parent body was sufficiently large to sustain heating from 26al for 8 myr or that late stage impact events supplied heat to the region where gro 95577 originated

modal mineralogy of ci and ci like chondrites by x ray diffraction the ci chondrites are some of the most hydrated meteorites available to study making them ideal samples with which to investigate aqueous processes in the early solar system here we have used position sensitive detector x ray diffraction psd xrd to quantify the abundance of minerals in bulk samples of the ci chondrite falls alais orgueil and ivuna and the antarctic ci like chondrites y 82162 and y 980115 we find that alais orgueil and ivuna are dominated by a mixed serpentine saponite phyllosilicate 81 84 vol plus minor magnetite 6 10 sulphides 4 7 and carbonates 3 this reflects an extended period of aqueous alteration and the near complete transformation of anhydrous phases into a secondary mineral assemblage the similarity in total abundance of phyllosilicate suggests that the ci chondrites all experienced the same degree of aqueous alteration on the parent body in contrast y 82162 contains a highly disordered serpentine saponite phyllosilicate 68 vol sulphide 19 olivine 11 and magnetite 2 this mineralogy is distinct from that of the ci chondrites attesting to both a different starting mineralogy and alteration history the structure and relatively low abundance of the phyllosilicate and the high abundance of olivine are consistent with previous observations that y 82162 represents ci like material that following aqueous alteration suffered thermal metamorphism at temperatures 500 c similarly y 980115 contains disordered serpentine saponite 71 vol sulphide 19 olivine 8 and magnetite 2 confirming that it too is a thermally metamorphosed ci like chondrite we suggest that the ci like chondrites are derived from a different parent body than the ci chondrites which underwent short lived thermal metamorphism due to impacts and or solar radiation

history and evolution of mesolithic landscapes in the haut quercy lot france new charcoal data from archaeological contexts charred wood analyses have been performed on three mesolithic sites located on the causse de gramat a karstic plateau in southwestern france lot department les fieux les escabasses and le cuzoul de gramat the sites yielded occupations dating from the early to the late mesolithic 9th to the 6th millennia cal bc in the absence of palynological data charcoal analysis allowed us to characterise the woody environment exploited by mesolithic hunter gatherers our results point at the minor place of softwoods in the landscape and the local importance of rosaceae prunoideae marking an original type of pre forest vegetation in order to retrace the local vegetation dynamics these results are synthesized and discussed thanks to a correspondence analysis which includes previous anthracological data from azilian and middle mesolithic levels of two other sites of the causse the homogeneity of the results speaks in favour of the stability of the local environment and confirms the specific vegetation feat

three dimensional reconstruction of an in situ miocene peat forest from the lower rhine embayment northwestern germany new methods in palaeovegetation analysis palaeovegetation reconstructions particularly of fossil forests are generally restricted to scant information on the taxonomic composition relative abundance of individual taxa or on tree density we have developed new techniques for the analysis of stump horizons that result in a relatively detailed three dimensional reconstruction of ancient forests in addition a rough estimate of their above ground standing biomass can be calculated these techniques are applied to an in situ miocene peat forest preserved in the lower rhine embayment northwestern germany in a study area of 2500 m2 476 stumps were mapped and used in the forest reconstruction additionally pollen samples and leaf remains have been analysed the peat forest consists primarily of conifers in particular taxodiaceae and pinaceae with sciadopitys being the most common genus the only angiosperms in the wood flora were palms but in the pollen flora evidence for the myricaceae mastixiaceae ericaceae and a few other angiosperms is also present the forest was relatively dense with 1904 trees ha and a basal area of 164 m2 mean trunk diameter was 28 cm while mean tree height is calculated to have been 9 9 m height diameter and density distribution are illustrated using contour and three dimensional surface plots estimated above ground biomass is 750 t ha but this value also includes dead or partly dead trees this peat forest does not closely compare with previous reconstructions of miocene peat forests its three dimensional structure and biomass differ from those of modern bald cypress swamps

53mn 53cr ages of kaidun carbonates 53mn 53cr ages of kaidun carbonates abstract we report the 53mn 53cr systematics of three dolomite grains from two different ci1 clasts contained within the kaidun meteorite breccia three internal isochrones result in initial 53mn 55mn ratios of 4 2 0 4 10 6 4 6 1 3 10 6 and 5 2 1 1 10 6 these initial values are consistent with those measured for dolomite in the orgueil ci1 chondrite hoppe et al 2007 petitat et al 2009 but significantly lower than the initial ratio determined by hutcheon et al 1999 from a combination of different carbonate types within various lithologies of the kaidun meteorite we construct an accretion scenario for the kaidun breccia by comparing the mineralogy and formation time scales of carbonates in the kaidun ci1 lithologies to the analogous ones of the ci1 chondrite orgueil in orgueil dolomite precipitation precedes the formation of the first bruennerite grains by a few million years hoppe et al 2007 petitat et al 2009 as the ci1 clasts in kaidun lack breunnerite grains and considering that aqueous alteration occurred prior to reaccretion of the various clasts onto the kaidun parent body e g macpherson et al 2009 we hypothesize that after rapid accretion and early aqueous alteration occurring within the first approximately 4 myr after solar system formation impact disruption of several asteroids and their reassembly into the kaidun parent asteroid was complete within an additional approximately 2 myr this confirms that aqueous alteration impact and reaccretion of material in the asteroid belt were early processes that began contemporaneously with chondrule formation

carbonates in ci chondrites clues to parent body evolution all ci chondrites are regolith breccias consisting of various types of chemically and mineralogically distinct mineral and lithic fragments or units in the ci chondrite ivuna for example four different lithological units were identified and are referred to as lithology i ii iii and iv so far lithologies iii and iv have been identified in orgueil as well it appears that at least ivuna and orgueil consist of the same basic lithologies in different proportions carbonates in cis occur as individual grains within such lithic units or exist as large fragments between them carbonate fragments are remnants of former carbonate veins and in contrast to individual carbonate grains are not genetically linked to lithological units four different types of carbonates dolomite breunnerite calcite siderite occur in cis and they constitute on average 5 vol of each studied section in this study carbonates in the ci chondrites orgueil ivuna alais and tonk were studied petrographically mineralologically and chemically the results clearly indicate that in contrast to most previous studies compositional differences exist between dolomites within and among ci chondrites from these differences it can be derived that 1 several episodes of alteration occurred on the ci parent body 2 physicochemical conditions during carbonate formation must have been different among cis and 3 ci carbonates obviously were formed at low temperatures in equilibrium with surrounding fluid s while local compositional changes in fluid s on a micrometer to millimeter scale as reflected by dolomite compositions within ci chondrites were most likely controlled by the availability of ca2 mg2 fe2 and especially mn2 ions in the aqueous solutions more widespread compositional changes on a meter or even larger scale were controlled by variable ph eh co2 partial pressure and especially temperature conditions as reflected by the compositional variability of dolomites among cis

53mn 53cr dating of fayalite formation in the cv3 chondrite mokoia evidence for asteroidal alteration fayalite grains in chondrules in the oxidized aqueously altered cv3 chondrite mokoia have large excesses of radiogenic chromium 53 these excesses indicate the in situ decay of short lived manganese 53 half life 3 7 million years and define an initial53mn 55mn ratio of 2 32 0 18 10 6 this ratio is comparable to values for carbonates in ci and cm chondrites and for several classes of differentiated meteorites mokoia fayalites formed 7 to 16 million years after allende calcium aluminum rich inclusions during hydrothermal activity on a geologically active asteroid after chondritic components had ceased forming in the solar nebula

interplay between tectonics climate and fluvial transport during the cenozoic evolution of the ebro basin ne iberia 1 three dimensional modeling that integrates fluvial sediment transport crustal scale tectonic deformation and lithospheric flexural subsidence is carried out to simulate the landscape and drainage evolution of the ebro sedimentary basin ne iberia the ebro basin underwent a long period of closed intramountain drainage as a result of tectonic topography generation at the pyrenees the iberian range and the catalan coastal range in the late oligocene the catalan coastal range underwent extension leading to the formation of the valencia trough nw mediterranean but the ebro basin remained closed for nearly 15 myr more before the ebro river cut through the remnants of the topographic barrier this drainage opening caused widespread basin incision that shaped spectacular outcrops of the syntectonic and posttectonic infill here we investigate the processes controlling these major drainage changes the modeling results constrained by a large data set on the tectonic and transport evolution of the area predict a closed phase characterized by a large lake in the central eastern ebro basin dry climatic conditions probably lowered the lake level and contributed together with rift flank uplift to prolong this endorheic basin stage the age and amount of reworked sediment after the opening are consistent with an onset of basin incision between 13 and 8 5 ma as a result of lake capture by escarpment erosion and lake level rise associated with sediment accumulation and wetter climatic conditions sea level changes in the mediterranean had no major impact in the large scale drainage evolution of the ebro basin index terms 1625 global change geomorphology and weathering 1824 1886 1815 hydrology erosion and sedimentation 3210 mathematical geophysics modeling 3344 meteorology and atmospheric dynamics paleoclimatology 8102 tectonophysics continental contractional orogenic belts keywords pyrenees drainage evolution lake sediment budget erosion flexure

charcoal taphonomy and significance in geology botany and archaeology abstract charcoal occurs in the natural environment as either a result of wildfire or volcanic processes in addition people may make charcoal either for domestic or industrial use charcoal may be used as a fuel for domestic heating and cooking through a range of industrial uses such as iron smelting more recently the charcoalification process has been used to make biochar that is relatively inert and promotes atmospheric co 2 reduction with such a wide range of uses research has been published in a broad range of journals and often whole areas of study are unfamiliar to other charcoal researchers here we review a range of charcoal studies and their inter relationships we present some of the results of a major international meeting on charcoal brussels september 2008 highlighting the potential of charcoal studies as part of palaeoenvironmental investigations both in a geological and archaeological context

asymmetric growth of the pyrenees revealed through measurement and modeling of orogenic fluxes orogenic asymmetry is ubiquitous in terms of topography structure and metamorphism but the relative influences of climate and tectonics in determining such asymmetry remain contentious this study demonstrates that for the case of the european pyrenees orogenic asymmetry is not defined by inherited structural asymmetry nor by orographic asymmetry of precipitation but is the simple consequence of the inherent tectonic growth of a doubly vergent orogen the pyrenees record approximately 60 myr of upper crustal accretion erosion and sedimentation that developed from late cretaceous to early miocene times approximately 165 km of plate convergence was accommodated by four phases of orogenic growth that can be summarized in terms of their generic orogenic development as follows 1 early inversion of passive margin extensional faults initiating the pro wedge 2 growth by a combination of frontal accretion and underplating to the pro wedge symmetrical and steady record of erosion and foreland basin sedimentation 3 cessation of pro wedge frontal accretion with propagation of the retro wedge deformation front 4 accelerated growth of pro wedge antiformal stack induced by underplating accelerated erosion over antiformal stack and increase in sediment discharge to pro foreland basin stabilization of outer pro wedge by sediment blanketing discrete element model experiments are used to explore the natural tendency of the system towards asymmetry model output demonstrates that during active frontal accretion to the pro wedge of an orogen the maxima in erosional denudation is offset towards the pro wedge relative to the maximum depths of exhumation this asymmetry is fundamentally driven by the progressive reduction in advection velocities of material within the orogen from the pro wedge into the retro wedge hence for an efficient erosional regime a dynamic coupling between erosion and structural uplift of the pro wedge will reduce activity of the retro wedge and hence drive asymmetry in terms of low temperature thermochronometry erosion and sedimentation the models also demonstrate the tendency for pro wedge growth through frontal accretion to slow however the cessation of frontal accretion as recorded by the south pyrenean thrust belt phases 3 and 4 requires additional forcing it is proposed that the thick wedge top sedimentation recorded at this time increased taper angles and hence stabilized the wedge accretionary influx into the orogen at this time was accomplished through underplating these processes governing asymmetry do not require a spatially variable climate or a laterally heterogeneous underthrust plate

bright carbonate veins on asteroid 101955 bennu implications for aqueous alteration history introduction carbonaceous asteroids formed early in solar system history and experienced varying degrees of aqueous water rock and thermal alteration most models of the evolution of these asteroids suggest that aqueous alteration was driven by hydrothermal convection however it is debated whether this alteration occurred in a chemically closed or open system the bulk chemical compositions of the carbonaceous chondrite meteorites imply that the system was closed models predict that large scale fluid flow in an open system took place on at least some asteroids in this scenario fluids would have flowed through fractures from the interior and minerals would have precipitated into these fractures forming veins rationale global spectral observations by the osiris rex origins spectral interpretation resource identification and security regolith explorer spacecraft have shown that carbon bearing materials including organics and or carbonates are widespread on the surface of near earth asteroid 101955 bennu to understand the composition of these carbon bearing materials and their implications for bennu s aqueous alteration history we examined visible near infrared spectra obtained at resolutions of 4 m in the region around the mission s primary sampling site nightingale we compared these spectra with laboratory spectra of organics and carbonates broadband panchromatic images of the nightingale region at pixel scales of 1 4 cm allowed us to search for surface features that could contextualize the spectral data results on the basis of the wavelength position and shape of spectral absorption features the closest matches to a subset 15 of spectra collected in the nightingale region are the carbonate minerals calcite dolomite and magnesite with calcite being the most prevalent these minerals are found in the highly aqueously altered cm and ci group carbonaceous chondrites proposed meteorite analogs of bennu bright centimeters thick roughly meter long veins are apparent in images of some boulders near the nightingale site the veins have albedos of 10 to at least 19 much brighter than bennu s average of 4 4 these albedos are consistent with the veins being filled by carbonates with minor abundances of opaque materials such as magnetite and organics the albedos are too high for the veins to be dominantly composed of organics or any other material that has been identified on bennu except carbonates there are only a few bright vein filling materials found in meteorites and carbonate is the only one of these that is plausibly present on bennu linear mixture modeling suggests that only a small fraction of a spectrometer field of view conclusion the observed bright veins on bennu are most likely dominantly composed of carbonates the detection of these meter sized putative carbonate veins indicates that extensive water flow occurred in a chemically open hydrothermal system on the larger parent asteroid of bennu before the catastrophic disruption of the parent asteroid led to bennu s reaccumulation as a rubble pile kinetic modeling assuming a calcite vein composition shows that a hydrothermal system kilometers in size with alteration likely taking place over thousands to millions of years would have been needed to create veins of the dimensions preserved in the constituent boulders of bennu some cm and ci group meteorites have very small micrometers to millimeters carbonate veins or presumed vein fragments veins on the scale that we observe on bennu are not present in meteorites it is possible that such veins are present on other carbonaceous asteroids that have not been observed by spacecraft we predict that the sample of bennu s surface material that is planned to be returned to earth by the osiris rex spacecraft will contain carbonates and that they will be distributed with a structure and scale distinct from those that occur in meteorites

holocene vegetation changes in nw iberia revealed by anthracological and palynological records from a colluvial soil macroscopic charcoal pollen and non pollen palynomorphs were isolated from a colluvial soil located on a small hill in campo lameiro nw spain in order to elucidate the vegetation history of the area and its relation to fire and human activities the presence of macroscopic charcoal throughout the 2 10 m thick soil 42 samples is evidence of frequent fires during the last c 6300 years the charcoal record was dominated by quercus probably q robur ericaceae probably arbutus unedo and erica arborea and fabaceae mainly genista type abrupt changes in the charcoal assemblage are less explicit in the pollen sequence probably as a result of pollen inflow from the downhill surroundings of the study site combined results indicated that the original oak woodland was gradually replaced by pyrophytic shrubs ericaceae and fabaceae as a result of fire recurrence non pollen palynomorphs strongly suggested that vegetation was deliberately ignited by past human societies to facilitate grazing no evidence of local agricultural practices was found episodes of accel erated shrubland expansion occurred c 6000 5500 cal bp c 4000 3500 cal bp and c 1700 cal bp the latter of which caused the definitive settlement of shrublands dominated by ericaceae and fabaceae which are nowadays widespread in nw iberia

crustal structure and orogenic material budget in the west central pyrenees surface and subsurface data are combined to construct a crustal scale cross section of the western central pyrenees france and spain at the boundary between the european and iberian plates the position of moho reflections in the ecors arzacq reflection profile suggests a tectonic wedge of european crust and upper mantle had indented the iberian plate at lower crustal levels the european wedge is overlain by an upper iberian wedge thus constituting a double stacked wedge geometry the upper wedge was delaminated and deformed giving rise to the pyrenean orogenic prism manifested as a bivergent fan in upper crustal levels the underthrust lower iberian plate has been imaged to depths of 55 60 km but crustal budget considerations based on a palinspastic reconstruction require that this continental root subducted to depths up to 90 km total orogenic contraction calculated from surface structures is about 75 80 km which was accomplished between the latest cretaceous and the early miocene at an averaged rate of 1 2 mm yr consistent with these moderate values exhumation of the orogen is much less than in the more shortened eastern parts of the range paleozoic basement and preorogenic mesozoic rocks are little eroded and much of the exhumation involved cannibalization of early foreland basins which once covered the entire poorly emergent orogen at this transect this resulted in a continuous process of sediment recycling and coupled with a considerable lateral arrival of material a bulk negative erosion sedimentation budget