mid late holocene vegetation response to climatic drivers and biotic disturbances in the banni grasslands of western india abstract tropical grasslands and savannas are globally extensive and are of significant environmental economic and ecological importance these ecosystems are anticipated to be particularly sensitive to future changes in climate and understanding how these systems have responded to climatic changes in the past can provide us with insights into their potential responses to future global change in this study the temporal dynamics of c 3 c 4 vegetation changes in response to changes in moisture availability local fire events and changing levels of herbivory in a summer rainfall region of western india are reconstructed for the past 4600 cal yr bp paleodata such as stable carbon isotope of bulk organic matter 13 c org oxygen isotope from carbonate shells 18 o shell macro charcoal and herbivore dung fungal spores are reported from the retrieved cores of two wetland sites located in the banni grasslands of western india results show that vegetation in the banni was composed mostly of c 3 vegetation from 4600 to 2500 cal yr bp after which there was a decline in c 3 vegetation from the late holocene to the present there was a mix of both c 3 and c 4 vegetation with c 4 grasses being more abundant in the ecosystem these shifts were coincident with rainfall changes from more mesic conditions during 4600 to 2500 cal yr bp to more arid conditions towards the present as indicated by 18 o shell isotope data the period of increase in c 4 vegetation also coincides with a period of increased biotic disturbances in the ecosystem particularly fire given the current scenarios of global warming recurrent drought events and increased anthropogenic use of similar ecosystems such studies can provide us insights into potential future trajectories of these ecosystems

methodology of the last climatic cycle reconstruction in france from pollen data abstract a numerical method has been devised to reconstruct the climate of the last climatic cycle from pollen data reliable annual reconstructions have been published recently for the two french long sequences of la grande pile and les echets covering the last 140 millennia this paper gives more details on the method used it proposes new reconstructions based on an extended modern pollen data base these reconstructions are consistent with the previous ones especially detailed information is obtained on the seasonal characteristics of climate computations of gcm on the climate variations from 125 kyr to 115 kyr b p are confirmed for western europe the insolation variations have induced at that time a decrease of seasonality accompanied by an increased cyclonic activity in winter this has been the beginning of the first ice growth after the last interglacial other glacier growth phases are detected at the end of substage 5c and particularly at the end of substage 5a

the holocene paleoenvironmental history of central european russia reconstructed from pollen plant macrofossil and testate amoeba analyses of the klukva peatland tula region holocene climatic variability and human impact on vegetation are reconstructed from a region in central european russia which lies at an important ecotone between broadleaf forest and steppe for the first time in this region we adopt a multi proxy approach that combines analysis of local mire conditions from plant macrofossil and testate amoeba analyses with pollen based quantitative climate reconstruction the proxies indicate a long term warming trend from 9700 to 7500 cal yr bp interrupted by a series of short term cold events from 7500 to 5000 cal yr bp the results imply a relatively stable climate warmer and drier than present spanning the holocene thermal maximum since 5000 cal yr bp the data suggest a change to cooler climate but with centennial scale variability this shift at around 5000 cal yr bp is supported by extensive evidence from other sites in the early holocene the region was occupied mainly by pine and birch forests broad leafed forests of oak lime and elm expanded after 7800 cal yr bp and remained dominant until the last few centuries during the historical period vegetation changes have been driven mainly by human activities

palaeohydrology fires and vegetation succession in the southern baltic during the last 7500 years reconstructed from a raised bog based on multi proxy data we present the first 7500 yr long multi proxy record from a raised bog located at the southern baltic coast poland testate amoebae plant macrofossils pollen and microscopic charcoal were used to reconstruct environmental changes in pomerania northern poland kaszuby lakeland from a 7 m thick peat archive of st zki bog dated 5500 bc ad 1250 we obtained a record of proxies representing different spatial scales regional vegetation changed simultaneously with local vegetation and testate amoebae showed a pattern of change similar to that of pollen and plant macrofossils on the basis of the combined proxies we distinguished three hydroclimatic stages moist conditions 5500 3450 bc drier conditions with regionally increased fires up to 600 bc and again moist conditions from 600 bc onward during the drier interval a first climatic shift to wetter conditions at 1700 bc is indicated by regional pollen as the replacement of corylus by carpinus and locally by e g the increase of hyalosphenia elegans and mire plants such as sphagnum sec cuspidata furthermore we observed a correlation since 600 bc among the re expansion of carpinus after a sudden decline ca 950 bc increased peat accumulation increase of hyalosphenia species and fewer fires suggesting lower evapotranspiration and a stable high water table in the bog fagus started to expand after ad 810 gradually replacing carpinus which was possibly due to a gradually more oceanic climate though we cannot exclude human impact on the forests peat accumulation determined by radiocarbon dating varied with bog surface wetness the hydroclimatic phases found in st zki peatland are similar to moisture changes recorded in other sites from poland and europe this is the first detailed record of hydroclimatic change during the holocene in the southern baltic region so it forms a reference site for further studies on other southern baltic bogs that are in progress

development and refinement of proxy climate indicators from peats peat especially from acidic mires bogs is a natural archive of past environmental change reconstructions of past climate from bogs commenced in the 19th century through examination of visible peat stratigraphy and later formed the basis for a postglacial climatic scheme widely used in northwest europe nevertheless misconceptions as to how bogs grow led to a 50 year lacuna in peat climate study before the concept of cyclic regeneration in bogs was refuted in recent decades research using proxy climate indicators from bogs has burgeoned a range of proxies for past hydrological change has been developed as well as use of pollen bog oaks and pines and other data to reconstruct past temperatures most of this proxy climate research has been carried out in northern europe but peat based research in parts of asia and north america has increased particularly during the last decade while research has also been conducted in australia new zealand and south america this paper reviews developments in proxy climate reconstructions from peatlands chronicles use of a range of palaeo proxies such as visible peat stratigraphy plant macrofossils peat humification testate amoebae and non pollen palynomorphs and explains the use of wiggle match radiocarbon dating and relationship to climate shifts it details other techniques being used increasingly such as biomarkers stable isotopes inorganic geochemistry and estimation of dust flux and points to new proxies under development although explicit protocols have been developed recently for research on ombrotrophic mires it must be recognised that not all proxies and techniques have universal applicability owing to differences in species assemblages mire formation topographic controls and geochemical characteristics

15 000 years of black carbon deposition a post glacial fire record from maar lake sediments germany abstract fires accompanied human development throughout the holocene leaving behind black carbon bc as residues from incomplete biomass burning here we used molecular fire markers benzene polycarboxylic acids bpcas to reconstruct fire history in two eifel maar lakes germany we hypothesized to find indications for i changes in bc related to ecosystem changes ii an increase in bc influx at the onset of agriculture until modern times and iii a change in bc quality due to technical progress in combustion e g at the beginning of agriculture and at the onset of the bronze age to calculate absolute bc influx into the maar lakes we multiplied bc contents with sedimentation rates the bc influx rates were elevated during tundra like vegetation in the late pleistocene up to 7 7 g bc m 2 a 1 followed by relatively constant 2 5 g bc m 2 a 1 from the bolling interstadial 13 7 kilo years before present ka bp until the early atlantic when forest began to develop thereafter bc influx increased with the onset of land use of neolithic cultures in the region from 7 5 ka bp to rates of 7 9 g bc m 2 a 1 noteworthy also the quality of bc changed higher ratios of five to six times carboxylated benzenes b5ca b6ca pointed at colder arable fires approximately 1000 years after first neolithic activity from 6 to 4 ka bp b5ca b6ca increased from 1 0 to 2 0 from 4 ka bp bronze age to modern times increasing burning temperatures as indicated by dropping b5ca b6ca ratios from 2 0 to 1 0 were related to metallurgy and industrialization between 2 5 and 1 ka bp maximum bc influx rates were reached with ca 15 g bc m 2 a 1 with increasing combustion efficiency and a reduction of wild fires during the last centuries total bc influx decreased suggesting that fossil fuel combustion contributed less to total bc input into the lake sediments than former vegetation fires

environmental changes during the holocene climatic optimum in central europe human impact and natural causes abstract the priority programme changes of the geo biosphere aimed to reconstruct the environmental history of central europe with emphasis on the time interval from 9000 to 5500 cal bp time slice ii coinciding with the holocene climatic optimum during this period the onset of human activities such as settlement agriculture and animal husbandry caused environmental changes studies of different landscape units in germany were carried out to identify these anthropogenically induced changes and to distinguish them from natural effects on the environmental system the investigated archives included laminated lake sediments fluvial sediments colluvia and soils speleothems peat and coastal sediments the different archives were examined using refined research methods including a variety of sedimentary and geochemical analyses together with pollen analysis and dating methods for the establishment of a reliable chronology the results of the various research groups are summarised and critically discussed based on these results the climatic optimum can be subdivided into three periods 1 the early atlantic from 9000 to 7500 cal bp with negligible human impact and stable environmental conditions 2 the late atlantic during early and middle neolithic from 7500 to 6300 cal bp with pollen evidence for vegetation changes but only negligible changes detectable in other proxy records and 3 the late atlantic during the younger neolithic jungneolithikum after 6300 cal bp with human impact observed in many archives and proxy records especially in the pollen record but also in lacustrine and fluvial sediments during the whole climatic optimum natural causes such as minor shifts of temperature did not induce substantial environmental changes though some changes such as temporary droughts may have facilitated and amplified the observed human impact

focal depths and fault plane solutions of earthquakes and active tectonics of the himalaya synthetic seismograms were compared with long period body waves for nine earthquakes with epicenters in the himalayan arc to determine depths of foci and to improve fault plane solutions focal depths are shallow 10 20 km inferred slip vectors are locally perpendicular to the mountain range they plunge very gently about 10 deg in the eastern sections of the range and more steeply about 25 deg in western sections assuming india to be a rigid plate the radially oriented slip vectors imply that southern tibet extends at about half the rate of underthrusting in the himalaya and therefore probably at about 5 10 mm yr the shallow depths and gentle dips of the fault planes at least for the events in the eastern half of the range are consistent with coherent underthrusting of the indian plate beneath at least the lesser himalaya the steeper dips of fault planes in the western part of the arc might reflect deformation of the overriding thrust plate or simply a steepening of the main underthrusting zone beneath the greater himalaya

synconvergence spreading of the higher himalaya crystalline in ladakh in ladakh suru valley nw himalaya regional fabrics of the higher himalaya crystalline result from a major deformation event that 1 is restricted to the indian crust above the main central thrust mct 2 postdates piling up of units above the mct 3 ended while thrusting was still continuing on the mct 4 developed under high temperature conditions following thickening 5 resulted in an asymmetric gneiss dome and 6 is associated with ene wsw to ew regional extension we suggest that extension was accommodated by spreading of the hot basement accompanied and followed by its uplift within the overlying cover along a major detachment zone the onset of the process appears closely related to strong thermal softening of the higher himalaya crystalline and is broadly synchronous with the formation of the himalayan leucogranites around 25 ma the regional pattern suggests that the mct zone could have acted as a decoupling zone between a thickening lower part and a thinning upper part of the indian crust during miocene times the extension direction is consistent with bulk himalayan kinematics involving nw se dextral wrenching along the western syntax and eastward extrusion of tibet we suggest that exhumation of gneissic ridges which characterize indian units above the mct all along the himalayan belt could reflect large scale crustal instability developed from thermally anomalous layers whose spreading ability can favor synconvergence extension

holocene glacier fluctuations a global overview of glacier advances and retreats grouped by regions and by millennia for the holocene is compiled from previous studies the reconstructions of glacier fluctuations are based on 1 mapping and dating moraines defined by 14 c tcn osl lichenometry and tree rings discontinuous records time series and 2 sediments from proglacial lakes and speleothems continuous records time series using 189 continuous and discontinuous time series the long term trends and centennial fluctuations of glaciers were compared to trends in the recession of northern and mountain tree lines and with orbital solar and volcanic studies to examine the likely forcing factors that drove the changes recorded a general trend of increasing glacier size from the earlyemid holocene to the late holocene in the extra tropical areas of the northern hemisphere nh is related to overall summer temperature forced by orbitally controlled insolation the glaciers in new zealand and in the tropical andes also appear to follow the orbital trend i e they were decreasing from the early holocene to the present in contrast glacier fluctuations in some monsoonal areas of asia and southern south america generally did not follow the orbital trends but fluctuated at a higher frequency possibly triggered by distinct teleconnections patterns during the neoglacial advances clustered at 4 4e4 2 ka 3 8e3 4 ka 3 3e2 8 ka 2 6 ka 2 3e2 1 ka 1 5e1 4 ka 1 2e1 0 ka 0 7e0 5 ka corresponding to general cooling periods in the north atlantic some of these episodes coincide with multidecadal periods of low solar activity but it is unclear what mechanism might link small changes in irradiance to widespread glacier fluctuations explosive volcanism may have played a role in some periods of glacier advances such as around 1 7e1 6 ka coinciding with the taupo volcanic eruption at 232 5 ce but the record of explosive volcanism is poorly known through the holocene the compilation of ages suggests that there is no single mechanism driving glacier fluctuations on a global scale multidecadal variations of solar and volcanic activity supported by positive feedbacks in the climate system may have played a critical role in holocene glaciation but further research on such linkages is needed the rate and the global character of glacier retreat in the 20th through early 21st centuries appears unusual in the context of holocene glaciation though the retreating glaciers in most parts of the northern hemisphere are still larger today than they were in the early and or mid holocene the current retreat

structural evolution and asymmetric uplift of the nanga parbat syntaxis pakistan himalya the nanga parbat syntaxis in the nw himalaya is a still growing crustal scale north trending antiformal structure in the core of which indian plate gneisses have been uplifted from beneath the overthrust rocks of the kohistan island arc isotopic and fission track geochronology show that uplift rates within the syntaxis have increased to present day rates of 6 mm yr uplift has been accommodated by a combination of initial northwest verging thrusting on the western margin of the syntaxis followed by crustal scale folding within the syntaxis and latterly by dextral reverse faulting on the western margin this thrusting folding and faulting is the effect of deformation at the north western lateral tips of the main himalayan thrusts where they interfere with the south southeast verging thrusts of the northwest himalaya

high resolution spectrometric analysis of rare earth elements activated cathodoluminescence in feldspar minerals abstract cathodoluminescence cl investigations of igneous metamorphic and sedimentary feldspars indicate that rare earth elements ree activated cl in feldspars is more common than previously assumed hot cathode cl microscopy combined with high resolution spectrometric analysis of cl emission allow to detect some ree below the detection limits of electron microprobe and proton induced x ray emission analysis pixe and reveal variations in the ree distribution within single feldspar crystals differently luminescing zones can reflect changes during feldspar crystallization and or element fluctuations during secondary alteration processes which are not discernible using conventional polarizing microscopy the results of the study document eu 2 sm 3 dy 3 tb 3 and nd 3 activated cl in feldspars of different origin the influence of the crystal field on shape and position of ree luminescence spectra significantly differs for divalent and trivalent ree ions whereas eu 2 shows a broad band emission 420 nm which is influenced by the local crystal field trivalent ions of the rare earth show narrow emission lines which reflect the transitions between excited state wave functions lying inside closed electronic shells the positions of these peaks and the characteristic energies are described for the different ree 3

diagenetic history and provenance of devonian terrestrial sandstones at the margin of gondwana padeha formation eastern alborz iran abstract the northern margin of gondwana in iran rifted in the devonian forming a passive continental margin to the paleotethys ocean the details of which are obscured by later collision a record of the early phase of opening of paleotethys is preserved in the 600 m thick padeha formation a middle devonian terrestrial rift basin succession the sandstones are quartz arenite sub arkose and arkose and contain minimal detrital matrix 1 bulk rock geochemistry according to major elements suggests a source to the sandstones that was dominated by i type granite but also based on trace elements included small amounts of intermediate or mafic rocks low zr and hree contents suggest little or no sandstone in the source area and thus low abundance of fine grained heavy minerals

mid and late holocene vegetation dynamics and fire history in the boreal forest of european russia a case study from meshchera lowlands abstract climate fire and human activities strongly affected the development of vegetation communities during the holocene yet the relative importance of these individual factors remains unclear in many areas this paper presents new multi proxy records of environmental change for the meshchera lowlands the central part of the east european plain during the holocene changes in regional vegetation during the mid and late holocene were influenced by climate fire regime and human impact as indicated by pollen plant macrofossil charcoal and testate amoebae analysis from several peat cores along with reconstruction of tree cover from pollen assemblages since 8500 cal yr bp the vegetation history represented a series of consecutive phases of birch birch pine and pine broadleaf forests with introduction of spruce after 2500 cal yr bp maximal abundance of broadleaf tree species was detected from 4700 to 2000 cal yr bp vegetation dynamics were strongly influenced by human activity since 1400 cal yr bp high fire frequency was recorded for the periods 8500 4500 cal yr bp and 3500 2000 cal yr bp when the fire return interval varied from 40 to 80 years since 2000 cal yr bp the fire return period exceeded 500 years suggesting a significant decline in fire frequency during the last two millennia

diagenesis and reservoir quality of overpressured deep water sandstone following inorganic carbon dioxide accumulation upper miocene huangliu formation yinggehai basin south china sea abstract turbidite deposits overpressure hydrothermal fluid activity and co 2 accumulations are the basic geologic characteristics of the upper miocene huangliu formation sandstone reservoir in the dongfang gas field yinggehai basin this study aims to unravel the timing and origin of dissolution in sandstone and evaluate the effects of inorganic co 2 accumulation on reservoir quality a comparative study between area dfx 1 co 2 rich and area dfx 2 co 2 poor has illustrated the differences in diagenetic alteration and the effects of co 2 accumulation on the sandstone reservoir diagenetic alteration of sandstones in area dfx 1 was characterised by intense dissolution and medium cementation dissolution of silicates following inorganic co 2 charging in the dfx 1 area created a higher percentage of dissolution porosity 41 0 53 9 of total visible porosity compared with minor dissolution porosity in the dfx 2 area 16 7 29 6 of total visible porosity small amounts of kaolinite authigenic quartz ankerite and siderite were precipitated by co 2 water rock reactions in area dfx 1 these minerals are almost absent in area dfx 2 the carbonate cement of the huangliu formation sandstone in area dfx 1 is characterised by light 13 c 3 3 to 1 6 pdb which is consistent with formation from inorganic carbon the timing of dissolution by inorganic co 2 is suggested to be at about 0 4 ma based on the previous simulation experiments in the two areas studied overpressure was caused by pressure transmission along deep open faults and was not related to mudstone undercompaction overpressure did a little to contribute to porosity preservation co 2 accumulating at low partial pressures related to hydrothermal fluid flow cannot make a net increase in porosity in the huangliu formation sandstone of the dongfang gas field

mechanism of plagioclase albitization abstract observations of closely spaced porous and cemented sandstones from the san joaquin basin the los angeles basin and the gulf coast reveal that albitization of plagioclase occurs during fracturing of the detrital plagioclase grains albitization is found to be a chemically selective hydrous reaction in which an rich plagioclase is preferentially albitized first relative to an poor plagioclase the observed non positive volume change during albitization indicates that aluminum mobility takes place on a scale at least as large as a thin section these findings are supported by thermodynamic stability calculations for plagioclase with different compositions and degrees of aluminum silicon ordering at 25 c in a representative sea water and at 100 c in an oil field water the calculations predict that 1 an rich plagioclase is less stable than an poor plagioclase and 2 plagioclase with a random al si distribution is less stable than plagioclase with the same composition but an ordered al si distribution any composition and structural state of plagioclase including albite is unstable in sea water at 25 c the width of the albitization zone may be controlled by the degree of aluminum silicon ordering this agrees well with the observed smaller temperature interval of albitization in sandstones containing only volcanically derived plagioclase

active tectonics of the western tethyan himalaya above the underthrusting indian plate the upper sutlej river basin as a pull apart structure fault bounded blocks and structural elements were mapped in the eastern ladakh spiti and upper sutlej river basin located within the tethyan himalaya and to the southwest of the karakorum fault zone mainly using landsat multispectral scanner mss band 5 band 7 near infrared images with detailed analysis of smaller areas by interactive digital processing of false color images and returned beam vidicon rbv imagery in conjunction with available topographical geological and seismological data for the first time the leo pargil horst and other nearby fault bounded blocks located at the northwestern end of the upper setlej river basin were clearly revealed on the landsat color composites shallow crustal seismicity is systematically related to the nne trending and n trending normal faults of the leo pargil and nearby regions some of the aftershocks of the kinnaur earthquake of january 19 1975 ms 6 8 appear to be associated with movement along the nne trending westbound fault of the leo pargil horst and the nearby kaurik chango fault the main shock however is teleseismically located at about 30 km to the northwest of the kaurik chango fault fault plane solutions of the main shock and two aftershocks indicate a large component of normal faulting in map view the upper sutlej river basin has an approximately rhomboidal shape and is located to the southwest of the karakorum fault system we suggest that this basin is a pull apart between the nw se oriented right lateral strike slip karakorum fault system and the high angle faults near the southern boundary of the tethyan himalaya the leo pargil horst is the northwestern bounding fault block of this pull apart the active tectonic features in this part of the tethyan himalaya appear to reflect right shear within the crust and this is probably a consequence of oblique underthrusting of the indian continental plate beneath the western himalaya and southwestern tibet during the neogene and quaternary times nw trending right lateral strike slip faults in the lesser himalaya and in southwestern tibet may reflect the same right shear

geochemistry and provenance of the altendorf feldspathic sandstone in the middle bunter of the thuringian basin germany an integrated mineralogical and geochemical study of the altendorf feldspathic sandstone in the middle bunter of the thuringian basin germany was carried out to obtain more information on its provenance sedimentological history and geochemistry the fine to coarse grained sandstone has an average composition of 66 63 71 quartz 30 27 35 feldspar and a fine grained illitic matrix the heavy mineral assemblage consists mainly of tourmaline zircon rutile apatite and opaque fe ti minerals it is inferred that this terrigenous material was laid down at the margin of the bunter basin high abundances of igneous quartz grains determined by cathodoluminescence cl the lack of metamorphic heavy minerals as well as alkali feldspar with an average k2o na2o ratio of 14 9 point to material of mostly granitic origin regional geologic and paleogeographic observations suggest that granites of the older and younger intrusive complex of the western erzgebirge are possible source rocks of the feldspathic sandstone the geochemical signature of the alkali feldspar k2o na2o ratio bao content points to the bergen and kirchberg granites as possible parent rocks comparing the mineralogical and geochemical data of the presumed source granites with those of the altendorf sandstone provides information on the sedimentation processes weathering fluvial transport and sedimentation under arid climatic conditions have caused complete decomposition and removal of plagioclase and biotite lowered the bulk ree content and led to the development of a positive eu anomaly the immobile trace elements e g ta th zr sc co ti are best suited for provenance determination because of their relatively low mobility during sedimentary processes elemental ratios such as la sc th sc co th and th ta have inherited the signature of the parent rocks and thus may be particularly useful for provenance studies to evaluate the control of specific minerals and grain size fractions on the distribution of trace elements in the sandstone separated fractions of quartz feldspar the 20 m fraction and heavy minerals were additionally analyzed the concentration densities elemental concentration in the fraction fraction weight reveal that with exception of hf the influence of the heavy mineral fraction on the whole rock geochemistry is insignificant although this fraction generally plays the most important role as carrier of trace elements quartz feldspar and the 20 m fraction have similar concentration densities between 20 and 40 for the ree with exception of eu which is mainly hosted in feldspar strong positive eu anomaly the influence of the 20 m fraction on the distribution of the ree and the elements u th sc ta strongly depends on the abundance of this fraction in the sediment alkali feldspar contains most of the ba sr rb and cs in the samples concentration densities of up to 97 thus differences in the abundances of these elements in whole rock samples can be related to changes in the mineralogical composition quartz feldspar ratio of the sediment

experimental partitioning of rb cs sr and ba between alkali feldspar and peraluminous melt hydrous partial melting experiments performed between 650 and 750 c at 200 mpa h20 on synthetic metapelite compositions quartz albite muscovite biotite mineral mixtures doped with ba sr rb and cs yielded alkali feldspar crystals with a wide range of compositions in equilibrium at their rims with peraluminous melt measured partition coefficients for normally trace lithophile elements between feldspar and melt d m fsp gl m ba sr rb cs do not depend on either temperature or bulk composition of melt for the compositions studied values of d sr fsp gl are between 10 and 14 and appear to be independent of the albite and orthoclase contents of the feldspar crystals in contrast values of d ba fsp gl and d rb fsp glare strongly dependent on the orthoclase content of feldspar relationships that can be expressed by the following linear equations d ba fsp gl 0 07 0 25 orthoclase and d rb fsp gl 0 03 0 0 1 orthoclase where orthoclase is in mole percent these equations reproduce the range of previously reported values for d ba and d rb determined on natural and synthetic samples a single partition coefficient for cs was also determined at d cs fsp gl 0 13 these data can be used in conjunction with recently published partition coefficients for muscovite biotite and plagioclase feldspars blundy and wood 1991 icenhower and london 1995 to model quantitatively the trace element signatures of peraluminous magmas during anatexis and crystallization depending on bulk composition and pressuretemperature trajectories during episodes of partial melting ba and sr and to a lesser extent rb are retained at the source while cs and li are enriched in the first melts these results explain why peraluminous granitic magmas with s type sedimentary sources carry a distinctive enrichment in li and cs

last millennium palaeoenvironmental changes from a baltic bog poland inferred from stable isotopes pollen plant macrofossils and testate amoebae the baltic coast of northern poland is a region of considerable potential interest for paleoclimatic studies because this region is under the influence of both oceanic and continental climates and that these two influences have likely changed through time also unlike many more intensively studied regions of europe human impact was more limited until the 19th century we present a multiproxy high resolution record from st zki mire an ombrotrophic mire located in northern poland 35 km from the baltic sea coast we combined four proxies from the peat testate amoebae stable isotopes 13c of sphagnum stems pollen and plant macrofossils supported by dendroecological data to assess the palaeoenvironmental changes that took place during the last millennium the general aim of this study was to test if a range of proxies testate amoebae pollen plant macrofossils and tree rings could allow inferring a climatic signal from a peat monolith despite the considerable anthropogenic impact on the pomerania landscape since the early medieval period combining internal e g macrofossils and testate amoebae and external pollen signals is key to distinguishing human from climatic signals in palaeoenvironmental studies of peatlands our more specific aims were to a reconstruct the last millennium palaeoenvironment in a baltic raised bog and its surroundings b identify the major wet dry shifts and correlate those events with climate change and human impact c assess the resilience of the baltic bog ecosystem following human impact we noted two disturbance periods in the history of the mire the two major disturbances in the history of the mire were dry periods i 1100 1500 ad and ii 1650 1900 2005 ad these are reflected in all indicators and can be interpreted as the mixture of climate impact and human activities however the pollen record shows little evidence of human indicators during the first dry shift the second disturbance can be related to local peat exploitation of the mire and then in the 20th century with limited artificial drainage from 1500 ad all proxies show that the water table abruptly rose in the mire the beginning of this shift occurred during the little ice age and therefore it is likely a climatic signal alternatively this wet shift could have been interpreted as a re wetting mire surface after peat burning but this interpretation is rejected because there is no evidence of major local fire in the macrofossil record the macrofossil data shows that sphagnum fuscum dominated the pristine mire vegetation but then declined and finally disappeared this pattern is comparable with the timing of extinction of sphagnum austinii in western europe this study illustrated the value of palynological analysis of peat archives especially for last millennium to assess the magnitude of anthropogenic land use changes for example the comparison of fagus beech and carpinus hornbeam history with the palaeohydrological record allowed us to exclude climate change as the most important factor for the decline and expansion of these tree species this study is the first direct comparison of testate amoeba and stable isotope data

provenance of fluvial sandstones at the start of late jurassic early cretaceous rifting in the cameros basin n spain abstract the cameros basin iberian chain central spain developed during the latest jurassic early cretaceous in an extensional regime characterized by high rates of subsidence its sedimentary fill has been subdivided into eight depositional sequences ds mainly composed of continental sediments ds 1 and ds 2 represent the first rifting stage tera group tithonian the purpose of this study is to characterize the tera group in the eastern part of the basin based on provenance criteria derived from fluvial sandstones in this area of the basin the tera group can be subdivided into three formations the agreda formation the magana formation and the sierra de matute formation these formations are composed of alluvial fan deposits meandering fluvial sediments and lacustrine palustrine mudstones a quantitative petrographic study indicated the presence of three main petrofacies in the tera group the close correlation between petrofacies and lithostratigraphic units indicates that sandstone composition is a powerful tool for deciphering the tectonic processes active during the initial rift stages of the cameros basin petrofacies 1 is sedimentolithic mean qm54f3lt43 and represents erosion of the jurassic marine pre rift substratum mainly kimmeridgian limestones during deposition of the ds 1 alluvial fan deposits agreda fm petrofacies 2 is quartzofeldspathic and can be subdivided into petrofacies 2a with an average composition of qm84f15lt1 and petrofacies 2b whose average composition is q71f23lt6 petrofacies 2 was generated by the erosion of low to medium grade metamorphic terranes and plutonic source rocks it characterizes the magana fm ds 2 petrofacies 3 is quartzolithic mean qm67f16lt17 and is attributed to tectonic reactivation of the basin this petrofacies characterizes the sierra de matute fm ds 2 thus the provenance evolution of this basin is characterized by erosion of the pre rift sedimentary substratum followed by unroofing of the basement as recorded in other ancient and modern rifted basins

diagenetic albitization of detrital k feldspars in jurassic lower cretaceous and tertiary clastic reservoir rocks from offshore norway ii formation water chemistry and kinetic considerations abstract formation waters from clastic reservoirs offshore norway are saturated or supersaturated with respect to albite deeper than 2 5 km and support the view of saigal et al 1988 that albitization of k feldspar is presently active in these sandstones thermodynamic and mass constraints show that the albitization process is more sensitive to potassium removal than sodium supply the temperature of albitization commencement coincides more or less with the estimated onset temperature of illitization of smectite 70 80 c interbedded shales seem to be the major potassium sink and source of sodium kinetic considerations indicate that at temperatures below 145 c the dissolution of k feldspar is always faster than albite growth combined with replacement constraints the kinetic data also explain the observed coarsening of growing albite crystals with increasing burial temperature

criteria for recognition of localization and timing of multiple events of hydrothermal alteration in sandstones illustrated by petrographic fluid inclusion and isotopic analysis of the tera group northern spain stratigraphic relations detailed petrography microthermometry of fluid inclusions and fine scale isotopic analysis of diagenetic phases indicate a complex thermal history in tithonian fluvial sandstones and lacustrine limestones of the tera group north spain two different thermal events have been recognized and characterized which are likely associated with hydrothermal events that affected the cameros basin during the mid cretaceous and the eocene multiple stages of quartz cementation were identified using scanning electron microscope cathodoluminescence on sandstones and fracture fills primary fluid inclusions reveal homogenization temperatures th from 195 to 350 c in the quartz cements of extensional fracture fillings the high variability of th data in each particular fluid inclusion assemblage is related to natural reequilibration of the fluid inclusions probably due to cretaceous hydrothermal metamorphism some secondary fluid inclusion assemblages show very consistent data th 281 305 c and are considered not to have reequilibrated they are likely related to an eocene hydrothermal event or to a retrograde stage of the cretaceous hydrothermalism this approach shows how multiple thermal events can be discriminated a very steep thermal gradient of 97 214 c km can be deduced from 18o values of ferroan calcites 18o 14 2 11 8 v pdb that postdate quartz cements in fracture fillings furthermore illite crystallinity data anchizone epizone boundary are out of equilibrium with high fluid inclusion th these observations are consistent with heat flux related to short lived events of hydrothermal alteration focused by permeability contrasts rather than to regional heat flux associated with dynamo thermal metamorphism these results illustrate how thermal data from fracture systems can yield thermal histories markedly different from host rock values a finding indicative of hydrothermal fluid flow

diagenetic albitization in the tera group cameros basin ne spain recorded by trace elements and spectral cathodoluminescence abstract this paper deals with the diagenetic albitization of both plagioclases and k feldspars in the tithonian fluvial sandstones of a rift basin cameros basin the sandstones in the lower part of the rift record have not suffered this albitization process a clear relationship is observed between sodium contents as the main element of some feldspars and their cathodoluminescence cl color the higher the sodium content the lower is their cl intensity in conclusion albitization processes are detectable by decreased cl intensities and changes in the cl spectra in addition very different trace element compositions are obtained by laser ablation when comparing trace elements of non albitized feldspars in sandstones of the lower part of the rift record with those of albitized feldspars in sandstones of the infill top non albitized k feldspars show rb sr ba and pb contents of up to 1000 ppm in contrast very flat profiles of trace element contents cl spectra from non albitized and albitized k feldspars and plagioclases revealed marked differences non albitized k feldspars present blue main emission band at 460 nm and brownish cl colors 590 nm sometimes in the same grain brownish colors are related to weathering processes the primary blue emission is related to al o al centers enhanced probably by al incorporation due to the coupled substitution of ba2 al3 m si4 weathered k feldspars present 4 8 times lower ba content than fresh blue luminescent ones the brownish colors are related to the external border or fractured grain zones altered by weathering processes therefore the observed 590 nm emission is assumed to be caused by structural defects resulting from weathering and alteration albitized k feldspars are usually weak luminescent with a typical cl emission band at 620 nm sometimes relicts of the original blue luminescence 460 nm band are still present the leaching of probably both al and ba can be responsible for the decrease in the blue band the characteristic 620 nm band is also dominant in albitized weak luminescent plagioclases two additional emission bands at 440 nm al o al center and 565 nm mn2 occur when albitized plagioclases preserved their original cl characteristics green cl color another spectral peak at ca 720 nm can be explained by fe3 activation due to fe3 al3 substitution the spectral cl measurements indicate that changes in luminescence due to albitization 620 nm emission seem to be more related to structural defects than to trace element activation or quenching

strain partitioning along the himalayan arc and the nanga parbat antiform shortening along the himalayan arc of continental convergence is approximately in the radial direction if the underthrusting foot wall block india is not deformed the hanging wall block tibet needs to stretch along the arc as suggested by radial grabens in southern tibet in contrast the nanga parbat haramosh massif and the western himalayan syntaxis are part of a 250 km long antiform that strikes in the radial direction northeast and verges northwest the nanga parbat antiform is the structural and topographic expression of arc parallel shortening that compensates for arc parallel extension in southern tibet this shortening is predicted to be as high as 12 mm yr

oblique plate convergence slip vectors and forearc deformation slip vectors from thrust earthquakes at subduction zones where convergence is oblique to the trench often point between the directions of relative plate convergence and normal to the trench axis suggesting that oblique convergence is taken up by partial decoupling decoupling means that a component of arc parallel motion of the leading edge of the upper plate results in less oblique thrusting at the trench partial decoupling is modeled by partitioning of oblique convergence into slip on thrust and strike slip faults that are parallel to the trench and to each other and starting with a force equilibrium condition a relationship between the obliquity and the earthquake slip vector orientation is derived assuming that either fault slips when shear stress on it reaches a yield stress oblique slip parallel to the plate vector should occur on the thrust fault when obliquity is smaller than a critical angle for obliquity at or greater than this angle the stress on the strike slip fault is large enough to start it slipping and when both faults are active the arc parallel motion of the forearc deflects the slip vector back toward the trench normal if we assume that continued slip on either fault occurs at constant stress but the two faults can be at different stresses the slip vector will maintain a constant angle relative to the trench normal even when obliquity is larger than the critical angle this limiting angle of the slip vector called max measured relative to the trench normal is simply the arcsine of the ratio of the shear forces resisting slip on the strike slip and thrust faults a consequence is that when the obliquity exceeds max the slip vectors on the thrust fault are sensitive only to the thrust fault orientation and contain no information about the convergence direction between the plates slip vectors at the java trench southwest of sumatra show the relationship clearly with max 20 5 while slip vectors at the aleutian trench show the relationship less clearly with max 25 to 45 the greater angle at the aleutian trench suggests that the upper plate is stronger in the aleutian arc relative to the thrust fault than in the sumatran arc consistent with the sumatran arc being continental and having a well developed strike slip fault while the aleutian arc is oceanic and without a clear transcurrent fault slip vectors at the philippine trench which like sumatra has a large strike slip fault inboard of it tend to stay within 25 of the trench normal when obliquity is as large as 50 if obliquity exceeds max and continues to increase along a subduction zone the rate of motion of the forearc relative to the upper plate will vary with obliquity in which case the forearc sliver should extend or contract parallel to the arc from the geometry of modern island arcs arc parallel extension should be the more common and has been hypothesized for both sumatra and the aleutians on the basis of earthquake slip vectors and for these and other arcs from geological observations from estimates of max and the arc parallel gradients in obliquity arc parallel strain rates are estimated to be 1 to 3 10 8 yr for the sumatran forearc 2 to 6 10 8 yr for the aleutian forearc and 0 3 to 3 10 8 yr for the philippine forearc oblique convergence and subsequent arc parallel extension if accompanied by crustal thinning may provide an important yet little appreciated mechanism for bringing high grade metamorphic rocks to the surface of subduction complexes

effect of water regime and vegetation on initial granite weathering in a glacier forefield evidences from cl sem and nomarski dic microscopy glacier forefields are characterised by high spatial variability in water availability solar radiation and vegetation as well as weathering processes the aim of this study is to improve the understanding of initial weathering of granite material with respect to the water regime availability and residence time of the water and the vegetation cover samples of granite powder were buried in four selected sites at the damma glacier forefield for one year a combined application of cathodoluminescence cl microscopy and spectroscopy scanning electron microscopy sem and nomarski differential interference contrast nomarski dic microscopy was used to investigate the initial stage of weathering the examination of the initial weathering stage revealed that the exposed mineral grains were strongly characterised by intra variations a clear change in particle shape and surface morphology could not be observed within the relatively short exposure period of one year however the grains from the lake sediment exhibited a clearly rounded shape caused by mechanical abrasion during transport processes the combination of several microscopic methods revealed i a strong influence of vegetation in the case of plagioclase oligoclase alteration ii a mutual effect of water and vegetation in the case of biotite delamination and iii alterations of potassium feldspar independent of local environments investigations with cathodoluminescence microscopy showed the suppression of blue luminescence and developed brown luminescence and confirmed a new insight in potassium feldspar weathering

role of oblique convergence in the active deformation of the himalayas and southern tibet plateau noting similarities with subduction along curved oceanic trenches and using a simple block model we show that radial vergence evident in earthquake slip vectors along the himalayan deformation front east west extension on north trending normal faults in the himalayas and southern tibet and right lateral strike slip on the karakorum jiali fault zone can all result from basal shear caused by the indian plate sliding obliquely beneath tibet along a gently dipping arcuate plate boundary within the framework of this mechanism the normal faults in the himalayas and southern tibet are not proxies for the uplift history of tibet the distribution and style of the faults in the himalayas and southern tibet suggest that the basal drag from the underthrusting indian lithosphere extends northward beneath most of southern tibet

changes in fire regimes since the last glacial maximum an assessment based on a global synthesis and analysis of charcoal data fire activity has varied globally and continuously since the last glacial maximum lgm in response to long term changes in global climate and shorter term regional changes in climate vegetation and human land use we have synthesized sedimentary charcoal records of biomass burning since the lgm and present global maps showing changes in fire activity for time slices during the past 21 000 years as differences in charcoal accumulation values compared to pre industrial there is strong broad scale coherence in fire activity after the lgm but spatial heterogeneity in the signals increases thereafter in north america europe and southern south america charcoal records indicate less than present fire activity during the deglacial period from 21 000 to 11 000 cal yr bp in contrast the tropical latitudes of south america and africa show greater than present fire activity from 19 000 to 17 000 cal yr bp and most sites from indochina and australia show greater than present fire activity from 16 000 to 13 000 cal yr bp many sites indicate greater than present or near present activity during the holocene with the exception of eastern north america and eastern asia from 8 000 to 3 000 cal yr bp indonesia and australia from 11 000 to 4 000 cal yr bp and southern south america from 6 000 to 3 000 cal yr bp where fire activity was less than present regional coherence in the patterns of change in fire activity was evident throughout the post glacial period these complex patterns can largely be explained in terms of large scale climate controls modulated by local changes in vegetation and fuel load

late glacial and holocene landscape dynamics in the southern taiga zone of east european plain according to pollen and macrofossil records from the central forest state reserve valdai hills russia abstract new pollen and macrofossil data are presented from three peat mires in the central forest state biosphere reserve southern valdai hills russia significant changes were recorded in the vegetation during the late glacial and the holocene caused by climate changes three main stages of wetland development clearly determined in the southern valdai hills were attributed to the boreal the onset of subboreal and the last two centuries intensive peat accumulation and forest paludification were induced by increasing humidity as a result of shifts in precipitation evaporation rate and probably of cooling and increased rainfall evidence of agricultural activity in places in the vicinity of the territories with traditional land use is preserved in pollen records since 2500 14 c bp however the forest ecosystems of the reserve were not significantly disturbed by anthropogenic activity until the last 200 150 years effective agriculture was possible in the southern valdai hills only from the 18th century

some elements of continental subduction along the himalayan front abstract detachment tectonics in which the subducting basement is not internally affected by thrusting and a steady state system in which the pattern of deformation and topography are invariant uplift is balanced by erosion and the material can experience subsequent phases of deformation by migrating through the system are proposed to be the fundamental mechanisms of convergence at the himalayan arc both surface and subsurface data are more consistent with these concepts than with more familiar concepts widely used in current models intracrustal thrusting and evolutionary tectonics where superimposed phases of deformation are interpreted as distinct phases the belt of intermediate magnitude thrust earthquakes the topographic front at the high himalaya and the main central thrust mct are associated with the same fundamental element the basement thrust front btf which traces a small circle in the central portion of the himalayan arc fault plane solutions indicate thrusting in the radial direction of this arc this radial convergence at the btf implies that tibet is extending laterally at a rate similar to the rate of convergence across the btf this extension cannot be unidirectional and must be parallel to the btf if the circular shape of the btf is invariant

a basin based approach to the long term history of forest fires as determined from peat strata valid reconstruction of long term forest fire histories from individual peat cores usually fails for a number of reasons even though visible charcoal horizons in peat are indisputable evidence of local orin situ fires both the dating and reliability of fire records from peat can be improved by the means of a basin based approach in which the gradual lateral growth of the peat is studied carefully by means of numerous dated basal peat samples applying this principle the frequency of forest fires in an esker landscape in southern finland was elucidated over the past 7000 years the results indicate that a period of active land use but undeveloped fire control in the area reduced the mean fire interval from the natural background fromc 130 years toc 40 years

palaeohydrology of the seim river basin mid russian upland based on palaeochannel morphology and palynological data abstract morphological geological geochronological and palynological analyses show that the landscape climate and hydrological history of the seim river basin includes 1 a period of sandy terrace 1 formation by shallow flows with the surface transformation by cryogenic and aeolian processes close to the last glaciation maximum 2 a cold and dry period about 16 14 k radiocarbon years b p with very high surface runoff and extremely large meandering channel formation 3 a period between the oldest dryas and the preboreal of non steady surface runoff decrease large meander abandonment and formation of smaller channels against the background of climate warming 4 a period of relative stability of hydrological regime and small variations of water runoff as in modern rivers throughout the holocene

july mean temperature and annual precipitation trends during the holocene in the fennoscandian tree line area pollen based climate reconstructions july mean temperature and annual precipipation during the last 9900 cal yr bp were recon structed from pollen assemblages preserved in a sediment core from northern finland quantitative recon structions were performed using a modern pollen climate calibration model based on weighted averaging partial least squares regression the predictive ability of the model was evaluated against modern meteoro logical data using leave one out cross validation the prediction error for july mean temperature is c 1 0 c and for annual precipitation 340 mm the july mean temperatures during the earliest holocene were low c 1 1 0 c and annual precipitation was high c 600 800 mm between 8200 and 6700 cal yr bp july mean temperatures reached their maxima 12 5 13 0 c which are c 1 4 1 7 c higher than at present at the same time precipitation decreased during the late holocene july mean temperatures declined and the last 2000 years have been the coolest since the early holocene precipitation has slightly increased the spatial coherence between our results and of several other climate reconstructions from northern europe indicates that the holocene climate was strongly influenced by north atlantic oceanic and atmospheric circulation patterns we propose that the distinctly oceanic climate of the early holocene was due to enhanced westerly latitudinal airflow which was replaced at c 8200 cal yr bp by a more meridional flow pattern and by the development of predominantly anticyclonic summer conditions

tibet uplift and erosion abstract the 5 km high tibetan plateau is an outstanding topographic feature on the earth today its horziontal extent elevation and location cause significant effects on modern atmospheric circulation and climate so the history of uplift of the surface of tibet is linked to cenozoic climate changes at local regional and perhaps global scales geological and geophysical studies of the plateau are contributing data on the present and past deformation of the tibetan lithosphere that has formed the plateau primarily during the cenozoic the principal of isostasy then can be used to estimate the elevation history of the surface for a given deformation history different parts of tibet probably had different uplift histories but presently available data are not sufficient for distinguishing many contrasts in one scenario cretaceous and early cenozoic north south distributed shortening of tibetan crust and mantle lithosphere probably caused significant uplift of the surface relative to sea level to perhaps half of the present elevation by the early miocene thinning of the high density mantle portion of the lithosphere during the miocene may then have allowed the thick tibetan crust to rise close to its present elevation perhaps higher before 8 ma since then slow east west extension of tibet probably reduced the crustal thickness slightly and may have caused the elevation of the plateau to decrease during the late cenozoic erosion of tibet unlike narrow mountain belts has been unable to match the uplift of a broad plateau orographic precipitation and efficient river networks concentrate erosion on the edges while the interior is protected from significant erosion despite its lofty elevation the southern edge of the plateau the himalaya has suffered a minimum of 25 km of denudation since the miocene while central tibet shows little or no sign of major erosion since that time the gangdese arc in southern tibet was rapidly eroded during the mid miocene when 4 km of rock apparently were removed from the surface as shown by mineral cooling ages this pulse of erosion was probably caused by a combination of local thrust system movement and changes in base level and precipitation due to relative elevation changes between the gangdese and the himalaya to the south the modern long wavelength flatness of tibet is unlikely to have been caused by erosion and indicates viscous flow at some level of the lithosphere has been acting to level the plateau surface

deformation of leucogranites of the crystalline main central sheet in southern tibet china abstract towards the top of the main central sheet in southern tibet china leucogranites intrude metamorphic rocks related to rocks of the main central thrust in the himalayas our study shows that the leucogranites suffered a northward shear deformation the significance of this event is discussed in terms of gravity driven decollement of the 10 000 m thick tethyan sedimentary pile over its crystalline basement

quantitative interpretation of fossil pollen spectra dissimilarity coefficients and the method of modern analogs abstract dissimilarity coefficients measure the difference between multivariate samples and provide a quantitative aid to the identification of modern analogs for fossil pollen samples how eight coefficients responded to differences among modern pollen samples from eastern north america was tested these coefficients represent three different classes 1 unweighted coefficients that are most strongly influenced by large valued pollen types 2 equal weight coefficients that weight all pollen types equally but can be too sensitive to variations among rare types and 3 signal0to noise coefficients that are intermediate in their weighting of pollen types the studies with modern pollen allowed definition of critical values for each coefficient which when not exceeded indicate that two pollen samples originate from the same vegetation region dissimilarity coefficients were used to compare modern and fossil pollen samples and modern samples so similar to fossil samples were found that most of three late quaternary pollen diagrams could be reconstructed by substituting modern samples for fossil samples when the coefficients indicated that the fossil spectra had no modern analogs then the reconstructed diagrams did not match all aspects of the originals no modern analogs existed for samples from before 9300 yr b p at kirchner marsh minnesota and from before 11 000 yr b p at wintergreen lake michigan but modern analogs existed for almost all holocene samples from these two sites and brandreth bog new york

holocene climate variability although the dramatic climate disruptions of the last glacial period have received considerable attention relatively little has been directed toward climate variability in the holocene 11 500 cal yr b p to the present examination of similar to50 globally distributed paleoclimate records reveals as many as six periods of significant rapid climate change during the time periods 9000 8000 6000 5000 4200 3800 3500 2500 1200 1000 and 600 150 cal yr b p most of the climate change events in these globally distributed records are characterized by polar cooling tropical aridity and major atmospheric circulation changes although in the most recent interval 600 150 cal yr b p polar cooling was accompanied by increased moisture in some parts of the tropics several intervals coincide with major disruptions of civilization illustrating the human significance of holocene climate variability c 2004 university of washington all rights reserved

vegetation dynamics and fire history at the southern boundary of the forest vegetation zone in european russia during the middle and late holocene climate and human activity affected significantly the eurasian on the forest vegetation zone through the holocene this paper presents new multi proxy records of environmental changes at the southern boundary of the mixed coniferous broadleaved forest zone in the east central part of the east european plain during the middle and late holocene palaeoecological analyses of a peat core for pollen charcoal peat humification plant macrofossils and testate amoebae with dating using radiocarbon have shown that climate appears to have been a dominant control on vegetation there is strong evidence for a reduced precipitation evapotranspiration ratio and high fire frequency during the holocene thermal maximum 6 9 5 3 ka bp leading to dominance of betula pinus forests by contrast subsequent climatic cooling led to the expansion of broadleaved forests and establishment of picea human activities influenced vegetation from the neolithic onwards but played a role which was secondary to climate until the recent past over the last century human impacts considerably increased because of harvesting of broadleaved trees and contributed to the formation of the current mixed coniferous broadleaved forests

role of sandstone provenance in the diagenetic albitization of feldspars a case study of the jurassic tera group sandstones cameros basin ne spain abstract the cameros basin iberian chain ne spain formed during the latest jurassic early cretaceous rifting stage in an extensional regime characterized by high subsidence rates its sedimentary infill thicker than 6000 m has been subdivided into eight depositional sequences ds mainly composed of continental sediments ds 1 and ds 2 represent the first rifting stage tera group tithonian mainly formed by fluvial and lacustrine sediments sandstone petrofacies evolved from quartz sedimentolithic in ds 1 to quartz feldspathic in ds 2 due to the rifting process in ds 2 three different types of detrital feldspars k feldspars albites and polysynthetic plagioclases with similar sodium rich compositions mean ab94 0 an4 5 or1 5 can be recognized chemically pure nonluminescent albites ab 99 are common in ds 2 diagenetic albitization of both plagioclases and k feldspars is inferred from conventional microscopy observations cathodoluminescence and electron microprobe analyses ds 1 contains few plagioclase grains which show no evidence of transformation into albite although the albitization is characterized as diagenetic it seems to be provenance controlled since it affects the units showing higher original plagioclase k feldspar ratio ds 2 due to the greater influence of plutonic and metamorphic source areas in ds 2 possible na sources are 1 the percolation of moderate to high salinity residual brines from related alkaline lakes developed at top of ds 2 in the eastern sector of the basin 2 clay mineral reactions sodium smectite to illite and chlorite indicated by mudstone composition in the interlayered mudstones and 3 the replacement of detrital sodium plagioclases by carbonate these three sources can be complementary

trace element partitioning in pantellerites and trachytes abstract in order to investigate the effect of increasing melt peralkalinity on partitioning partition coefficients have been determined using neutron activation analyses of coexisting phenocrysts and glass of five samples from pantelleria spanning the range trachyte to pantellerite alkali feldspar partition coefficients for fe rb ba sr and eu vary with melt peralkalinity due to changes in melt polymerization and to the systematic increase in xor and decrease in xan of the feldspar in going from trachyte to pantellerite fe partition coefficients increase from 0 04 to 0 10 presumably because fe 3 increasingly substitutes in the feldspar tetrahedral site as melt activity of al declines and fe concentrations increase partition coefficients for trivalent light rees decrease and the partitioning pattern becomes flatter the most evolved samples having some of the lowest published values for feldspar the hundredfold decline in eu partition coefficients 2 5 to 0 024 and the decrease in the size of the positive partitioning anomaly are attributed to increasing eu3 eu2 in the melt as it becomes more peralkaline as well as to concomitant decrease in the ca content of feldspar as a result the behavior of eu during fractional crystallization of peralkaline suites is fundamentally different from that in metaluminous suites absolute abundances rise and the size of the negative eu anomaly changes little with fractionation beyond pantelleritic trachyte barium and strontium do not decline to extremely low concentrations in pantellerites as they do in highly evolved metaluminous rhyolites because the feldspar partition coefficients drop precipitously with peralkalinity similarly rb contents do not get large because the partition coefficient increases slightly 0 11 to 0 25 with peralkalinity and is sufficient to make rb only weakly incompatible in the feldspar dominated assemblage partition coefficients calculated for sr and ba from natural phenocryst matrix pairs can be gross over estimates in these feldspar rich felsic rocks if phenocrysts are zoned this effect is severe for assemblages with bulk distribution coefficients d greater than 4 even at very small crystal contents and for 4 d 2 it is significant if crystal contents exceed about 25 some of the very high values and much of the variability reported in the literature for ba and sr feldspar partition coefficients may be a result of this effect in contrast to feldspar partition coefficients for apatite and mafic phases change little with peralkalinity partition coefficients for rees and the compatible elements sc co and cr are all less than half those in fe rich clinopyroxene and olivine of similar composition in high silica rhyolite although absolute levels of partition coefficients are a function of melt polymerization the shapes of the ree partitioning patterns appear to be related to the composition of the clinopyroxene scandium is most strongly concentrated in clinopyroxene partition coefficient 27 60 having larger values in more fe rich compositions apatite shows a wide range in composition within the suite the concentrations of si fe rees and y increasing and mg ca and p decreasing in more evolved samples these trends however parallel those in coexisting glasses so that partition coefficients are essentially constant in peralkaline suites cs is the most incompatible of commonly analyzed elements but its great mobility during alteration and weathering limits its use as a differentiation index next in order of incompatibility are th u hf zr and ta which have small but finite values of d due to the partitioning of th and u into apatite 2 the accommodation of zr and hf by clinopyroxene 0 4 and titanomagnetite 0 2 and relatively high concentrations of ta in cossyrite and fe ti oxides the next most incompatible are the lightest and the heaviest rees and finally the middle trivalent rees and rb plots of pairs of relatively incompatible elements form straight line trends over large compositional ranges in peralkaline suites because the replacement of olivine titanomagnetite by cossyrite as the melt becomes more peralkaline causes little change in d the ree patterns of titanomagnetite and cossyrite are both approximately flat at values less than 0 1 and the relatively high titanomagnetite partition coefficients for ta 2 zr and hf when combined with the very low partition coefficients for these elements for olivine approximate the moderate partition coefficients for cossyrite

gps measurements of present day convergence across the nepal himalaya the high elevations of the himalaya and tibet result from the continuing collision between india and asia which started more than 60 million years ago1 4 from geological and seismic studies of the slip rate of faults in asia5 it is believed that approximately one third of the present day convergence rate between india and asia 58 4mmyr 1 is responsible for the shortening uplift and moderate seismicity of the himalaya great earthquakes also occur infrequently in this region releasing in minutes the elastic strain accumulated near the boundary zone over several centuries and accounting for most of the advance of the himalaya over the plains of india the recurrence time for these great earthquakes is determined by the rate of slip of india beneath tibet which has hitherto been estimated indirectly from global plate motions6 from the slip rates of faults in asia7 8 from seismic productivity9 and from the advance of sediments on the northern ganges plain10 here we report geodetic measurements using the global positioning system gps of the rate of contraction across the himalaya which we find to be 17 52 2 mm yr 1 from the form of the deformation field we estimate the rate of slip of india beneath tibet to be 20 5 2 mmyr 1 strain sufficient to drive one or more great himalayan earthquakes with slip similar to that accompanying the magnitude 8 1 bihar nepal 1934 earthquake may currently be available in western nepal

the surface of labradorite feldspar after acid hydrolysis abstract after reaction with a ph both the surface area of the reacted feldspar and the porosity increase with acid hydrolysis modeling of nitrogen sorption onto the surface suggests that the pores have a nominal radius of 20 80 a or less this distribution of pore sizes resembles other acid reacted silicate materials such as glass chrysotile and kaolinite although the mineral surface clearly becomes more porous during acid hydrolysis the increase in powder area also does not coincide with an increase in the flux of dissolved si from the powder we thus attribute most of this increase in area to spallation of the silica rich surface from the feldspar upon drying

assessing holocene vegetation and fire history by a multiproxy approach the case of stodthagen forest northern germany the woodland history of the forest of stodthagen northern germany was investigated by using complementary palaeobotanical indicators six soil profiles from the study plot were sampled the wood charcoal pieces extracted from the soil samples were quantified taxonomically identified and some were radiocarbon dated peat sequences from a small adjacent mire were also sampled and the pollen microcharcoal and macrocharcoal were analysed the pollen record shows a continuous forestation during the holocene with small indication of a disturbance phase during the late holocene this continuity of the woodland presence is confirmed by the weak quantity of macrocharcoal indicating that fire did not have a serious impact during the holocene in terms of canopy opening despite the identification of three local fire events however large amounts of wood charcoal pieces were found in the soil samples allowing the identification of at least one more fire event dated in the iron age unrecorded in the charcoa

mid to late holocene climate change an overview the last 6000 years are of particular interest to the understanding of the earth system because the boundary conditions of the climate system did not change dramatically in comparison to larger glacial interglacial changes and because abundant detailed regional palaeoclimatic proxy records cover this period we use selected proxy based reconstructions of different climate variables together with state of the art time series of natural forcings orbital variations solar activity variations large tropical volcanic eruptions land cover and greenhouse gases underpinned by results from general circulation models gcms and earth system models of intermediate complexity emics to establish a comprehensive explanatory framework for climate changes from the mid holocene mh to pre industrial time the redistribution of solar energy due to orbital forcing on a millennial timescale was the cause of a progressive southward shift of the northern hemisphere nh summer position of the intertropical convergence zone itcz this was accompanied by a pronounced weakening of the monsoon systems in africa and asia and increasing dryness and desertification on both continents the associated summertime cooling of the nh combined with changing temperature gradients in the world oceans likely led to an increasing amplitude of the el nin o southern oscillation enso and possibly increasingly negative north atlantic oscillation nao indices up to the beginning of the last millennium on decadal to multi century timescales a worldwide coincidence between solar irradiance minima tropical volcanic eruptions and decadal to multi century scale cooling events was not found however reconstructions show that widespread decadal to multi century scale cooling events accompanied by advances of mountain glaciers occurred in the nh e g in scandinavia and the european alps this occurred namely during the little ice age lia between ad w1350 and 1850 when the lower summer insolation in the nh due to orbital forcing coincided with solar activity minima and several strong tropical volcanic eruptions the role of orbital forcing in the nh cooling the southward itcz shift and the desertifi cation of the sahara are supported by numerous model simulations other simulations have suggested that the fingerprint of solar activity variations should be strongest in the tropics but there is also evidence that changes in the ocean heat transport took place during the lia at high northern latitudes with possible additional implications for climates of the southern hemisphere sh

holocene annual mean temperature changes in estonia and their relationship to solar insolation and atmospheric circulation patterns abstract we reconstructed annual mean temperature tann trends from three radiocarbon dated holocene pollen stratigraphies from lake sediments in estonia northern europe the reconstructions were carried out using a north european pollen climate calibration model based on weighted averaging partial least squares regression the cross validated prediction error of the model is 0 89 c and the coefficient of determination between observed modern tann values and those predicted by the model is 0 88 in the reconstruction the holocene thermal maximum htm is distinguishable at 8000 4500 cal yr b p with the expansion of thermophilous tree species and tann on average 2 5 c higher than at present the pollen stratigraphical data reflect progressively warmer and drier summers during the htm analogously with the modern decadal scale climatic variability in north europe we interpret this as an indication of increasing climatic continentality due to the intensification of anticyclonic circulation and meridional air flow post htm cooling started abruptly at around 4500 cal yr b p all three reconstructions show a transient ca 300 years cooling of 1 5 2 0 c at 8600 8000 cal yr b p we tentatively correlate this cold event with the north atlantic 8 2 ka event at 8400 8000 cal yr b p provided that the 8 2 ka event was caused by freshening of the north atlantic surface water our data provide evidence of the climatic and vegetational responsiveness of the boundary of the temperate and boreal zones to the weakening of the north atlantic thermohaline circulation and the zonal energy transport over europe no other cold events of comparable magnitude are indicated during the last 8000 years

quantitative pollen based climate reconstruction in central japan application to surface and late quaternary spectra abstract climate reconstruction in japan by the best modern analogues method was tested with 285 surface pollen spectra and then applied to the 47 000 years pollen profile from lake mikata central japan both pollen taxa percentages and plant functional type affinity scores were used in the reconstruction of six climate variables the reconstructed values were compared with the estimated modern climate at each surface pollen site in order to evaluate the accuracy of the pollen based reconstruction the reconstruction of thermal parameters is very reliable correlation coefficient r between 0 86 and 0 89 the reconstruction of annual precipitation is less accurate r 0 7 we also proposed a new technique to calibrate reconstructed values into both probability distribution and or confidence regions of observed values the specialized programs for this calibration polcalib and polhist are available at qsr website http www elsevier nl locate quascirev the reconstruction of the late quaternary climate changes around lake mikata shows that the summer and winter temperatures were 5 c lower than present around 40 uncal kyr bp reached a minimum around 20 uncal kyr bp 10 c lower than present and became similar to present day at 8 uncal kyr bp the estimates for annual precipitation show that it was driest around 20 uncal kyr bp

geology of the northern part of the nanga parbat massif northern pakistan and its implications for himalayan tectonics the northern outcrop termination of indian continental crust lies at the nanga parbat massif from where this contribution presents new field data the tectonic contact with the structurally overlying kohistan island arc is concordant and ductile is associated with interleaving of nanga parbat and kohistan lithologies and may be correlated with the main mantle thrust found elsewhere in the nw himalayas this ductile shear zone is locally overprinted by cataclastic faults associated with exhumation of the massif but overall the northern outcrop termination of the massif is controlled by erosion through a gently northward plunging antiformal structure this folds both the main mantle thrust and the underlying concordant 9layered unit9 of the nanga parbat basement thus there is no indication that the massif acted as a promontory to the indian continent during collision nor that it is a structure entirely bound by neotectonic faults ductile shear fabrics associated with the 9main mantle thrust9 are cross cut by leucogranite sheets and pegmatites these may represent the stockwork to a significant crustal melt granite body described here in the northern massif this jutial granite shows many geochemical characteristics in common with similar bodies in the high himalayas which are consistent with anatexis of the buried indian continental basement rocks however the granite is enriched in heat producing elements particularly th 22 ppm and shows extremely high 87 sr 86 sr ratios 0 88 the high concentrations of radiogenic sr are also an attribute of a suite of hitherto enigmatic leucogranitic pegmatites that laces the nanga parbat massif suggesting that these may represent a stockwork to a largely buried body of which the jutial granite is a small exposure the enrichment in heat producing elements within the granite may reflect similarly high heat production in the source indian continental crust requiring in turn a fundamental re examination of the thermal evolution of this crust during himalayan metamorphism and exhumation

the pace of holocene vegetation change testing for synchronous developments mid to high latitude forest ecosystems have undergone several major compositional changes during the holocene the temporal and spatial patterns of these vegetation changes hold potential information to their causes and triggers here we test the hypothesis that the timing of vegetation change was synchronous on a sub continental scale which implies a common trigger or a step like change in climate parameters pollen diagrams from selected european regions were statistically divided into assemblage zones and the temporal pattern of the zone boundaries analysed the results show that the temporal pattern of vegetation change was significantly different from random times of change cluster around 8 2 4 8 3 7 and 1 2 ka while times of higher than average stability were found around 2 1 and 5 1 ka compositional changes linked to the expansion of corylus avellana and alnus glutinosa centre around 10 6 and 9 5 ka respectively a climatic trigger initiating these changes may have occurred 0 5 to 1 ka earlier respectively the synchronous expansion of c avellana and a glutinosa exemplify that dispersal is not necessarily followed by population expansion the partly synchronous partly random expansion of a glutinosa in adjacent european regions exemplifies that sudden synchronous population expansions are not species specific traits but vary regionally

sandstone petrography of continental depositional sequences of an intraplate rift basin western cameros basin north spain the cameros basin in central spain is an intraplate rift basin that developed from late jurassic to middle albian time along nw se trending troughs the sedimentary basin fill was deposited predominantly in continental environments and comprises several depositional sequences these sequences consist of fluvial sandstones that commonly pass upward into lacustrine deposits at the top producing considerable repetition of facies this study focused on the western sector of the basin where a total of seven depositional sequences ds 1 to ds 7 have been identified the composition of sandstones permits the characterization of each sequence in terms of both clastic constituents and provenance in addition four main petrofacies are identified petrofacies a is quartzosedimentolithic mean of qm85f2lt13 and records erosion of marine jurassic pre rift cover during deposition of fluvial deposits of ds 1 brezales formation petrofacies b is quartzofeldspathic mean of qm81f14lt5 with p f 1 at the base this petrofacies was derived from the erosion of low to medium grade metamorphic terranes of the west asturian leonese zone of the hesperian massif during deposition of ds 2 jaramillo formation and ds 3 salcedal formation quartzose sandstones characterize the top of ds 3 mean of qm92f4lt4 petrofacies c is quartzarenitic mean of qm95f3lt2 with p f 1 and was produced by recycling of sedimentary cover triassic arkoses and carbonate rocks in the sw part of the basin ds 4 pen acoba formation finally depositional sequences 5 6 and 7 pinilla de los moros hortiguela pantano and abejar castrillo de la reina formations respectively contain petrofacies d this petrofacies is quartzofeldspathic with p f near zero and a very low concentration of metamorphic rock fragments from qm85f11lt4 in pantano formation to qm73f26lt1 in castrillo de la reina formation petrofacies d was generated by erosion of coarse crystalline plutonics located in the central iberian zone of the hesperian massif in addition to sandstone petrography these provenance interpretations are supported by clay mineralogy of interbedded shales thus shales related to petrofacies a and c have a variegated composition illite kaolinite and randomly interlayered illite smectite mixed layer clays the presence of chlorite characterizes interbedded shales from petrofacies b and illite and kaolinite are the dominant clays associated with petrofacies d these petrofacies are consistent with the depositional sequences and their hierarchy an early megacycle consisting of petrofacies a and b ds 1 to ds 3 was deposited during the initial stage of rifting when troughs developed in the west asturian leonese zone a second stage of rifting resulted in propagation of trough bounding faults to the sw involving the central iberian zone as a source terrane and producing a second megacycle consisting of petrofacies c and d ds 4 ds 5 ds 6 and ds 7 sandstone composition has proven to be a powerful tool in basin analysis and related tectonic inferences on intraplate rift basins because of the close correlation that exists between depositional sequences and petrofacies

diagenetic albitization of detrital k feldspar in jurassic lower cretaceous and tertiary clastic reservoir rocks from offshore norway i textures and origin abstract the origin of albitized grains in sandstones has been the topic of considerable discussion in recent years some workers believe that the albitization of feldspar can occur in situ during burial diagenesis but others argue that albitization is a feature inherited from source clastic grains our petrological and chemical studies of subsurface samples of the jurassic lower cretaceous and tertiary reservoir sandstones from offshore norway show that detrital grains of potassium feldspar have been albitized during burial diagenesis criteria suggesting that the albitization has occurred during burial diagenesis include 1 euhedral habit of albite crystals with sharp edges and comers and markedly smooth crystal faces 2 generally untwinned albitized grains mostly riddled with minute br wnish inclusions 3 lack of cathodoluminescence in albite 4 homogeneous and pure albite composition 99 ab 5 absence of albitized grains in carbonate cemented zones and 6 increase in the percentage and degree partial to complete of albitized k feldspar with depth under sem albitized grains display two types of fabrics type i albitized grains are composed of numerous tiny albite crystals 1 30 m growing along cleavage planes in parent grains and they have abundant dissolution porosity while type ii albitized grains show blocky albite crystals 5 80 m forming pseudomorphs of detrital k feldspar and they lack any dissolution porosity type i albitized grains are found commonly at shallower depths between 2 2 and 3 km and temperatures varying from 65 to 90 c whereas type ii albitized grains dominate at greater depths 3 5 km and at temperatures 90 c albitization proceeds by a dissolution precipitation mechanism at shallower depth dissolution of the parent k feldspar is more rapid than the precipitation of albite and rates of albite precipitation increase with depth favoring pseudomorphic replacement of k feldspars other factors that influence albitization processes are ana ak permeability reduction and surface dissolution kinetics of the parent grain

forest history peatland development and mid to late holocene environmental change in the southern taiga forest of central european russia understanding the long term ecological dynamics of boreal forests is essential for assessment of the possible responses and feedbacks of forest ecosystems to climate change new data on past forest dynamics and peatland development were obtained from a peat sequence in the southern valdai hills european russia based on pollen plant macrofossil micro charcoal peat humification and testate amoeba analyses in terms of vegetation history the results demonstrate a dominance of broadleaved forests in the study area from 7000 4000 cal yr bp picea was initially a minor component of this forest but increased in cover rapidly with climatic cooling beginning at 4000 cal yr bp becoming the dominant species broadleaved species persisted until 900 cal yr with evidence for intensified felling and forest management over recent centuries over the last four hundred years there is evidence for widespread paludification and the establishment of picea sphagnum forests these data demonstrate how modern wet woodlands have been shaped by a combination of climatic and anthropogenic factors over several millennia the results also demonstrate the value of a multiproxy approach in understanding long term forest ecology

k feldspar phenocrysts in microgranular magmatic enclaves a cathodoluminescence and geochemical study of crystal growth as a marker of magma mingling dynamics abstract the crystallization history of zoned k feldspar phenocrysts in microgranular magmatic enclaves in the karkonosze granite sw poland reveals that the crystals grew in stirred coeval magmas of contrasting compositions the growth mechanism and crystal compositions are investigated using cathodoluminescence and profiling by electron microprobe and laser ablation icp ms these methods provide insight into the crystallization process and the varying compositions of the host melt the phenocrysts show two types of growth patterns with or without resorption interfaces the trace element distribution heterogeneous across different zones and within single phenocryst zones reflects a dynamic process of crystal growth from compositionally heterogeneous magma hybridization is also reflected in the density of structural al o al defects features that relate to coupled ba al incorporation into the crystal structure differences in structural defect densities and crystal composition trace the degree of hybridization in the granitic magma during the growth of the k feldspar phenocrysts