climate change signature of small scale parasequences from lateglacial holocene transgressive deposits of the arno valley fill abstract despite recent report of short term cyclicity from lateglacial holocene deposits of several coastal plains worldwide no precise documentation of the key factors controlling cyclic facies architecture has been made available by previous work detailed sedimentological analysis of a continuously cored borehole around the town of pisa in western tuscany provides evidence for the occurrence of three high frequency transgressive regressive cycles within the post last glacial maximum lgm transgressive succession 13 8 cal kyr bp of the arno incised valley fill these cycles which are bounded by lateral equivalents of marine flooding surfaces are 8 12 m thick and correspond to small scale parasequences micropalaeontological foraminifers and ostracods investigations based upon differentiation of eight microfossil associations allow to refine the stratigraphic framework emphasizing subtle changes in palaeosalinity across parasequence boundaries diagnostic changes in vegetation patterns driven by opposite climate conditions enable precise documentation of parasequence development as a function of climate change pollen spectra invariably show expansions of broad leaved forests at parasequence boundaries suggesting that rapid shifts to warmer climate conditions accompanied episodes of rapid sea level rise in contrast stillstand phases saw the development of cold temperate communities upper parts of parasequences suggesting transition to temporary colder climate conditions reconstruction of parasequence architecture on the basis of adjacent stratigraphic data combined with palaeoclimate characterization and radiometric dating enable identification within the transgressive arno valley body of three major regressive pulsations that are tentatively correlated with the most important cooling events of the post lgm period the sedimentary response to these short term phases of climatic cooling is clearly documented by episodes of widespread coastal plain and bay head delta progradation leading to partial estuary infilling and temporary establishment of continental environments in the proximal and central sectors of the valley

age dating and the orbital theory of the ice ages development of a high resolution 0 to 300 000 year chronostratigraphy using the concept of orbital tuning a continuous high resolution deep sea chronostratigraphy has been developed spanning the last 300 000 yr the chronology is developed using a stacked oxygen isotope stratigraphy and four different orbital tuning approaches each of which is based upon a different assumption concerning the response of the orbital signal recorded in the data each approach yields a separate chronology the error measured by the standard deviation about the average of these four results which represents the best chronology has an average magnitude of only 2500 yr this small value indicates that the chronology produced is insensitive to the specific orbital tuning technique used excellent convergence between chronologies developed using each of five different paleoclimatological indicators from a single core is also obtained the resultant chronology is also insensitive to the specific indicator used the error associated with each tuning approach is estimated independently and propagated through to the average result the resulting error estimate is independent of that associated with the degree of convergence and has an average magnitude of 3500 yr in excellent agreement with the 2500 yr estimate transfer of the final chronology to the stacked record leads to an estimated error of 1500 yr thus the final chronology has an average error of 5000 yr

the analogue shear zone from rheology to associated geometry the geometry of ductile strain localization phenomena is related to the rheology of the deformed rocks both qualitative and quantitative rheological properties of natural rocks have been estimated from finite field structures such as folds and shear zones we apply physical modelling to investigate the relationship between rheology and the temporal evolution of the width and transversal strain distribution in shear zones both of which have been used previously as rheological proxies geologically relevant materials with well characterized rheological properties newtonian strain hardening strain softening mohr coulomb are deformed in a shear box and observed with particle imaging velocimetry piv it is shown that the width and strain distribution histories in model shear zones display characteristic finite responses related to material properties as predicted by previous studies application of the results to natural shear zones in the field is discussed an investigation of the impact of 3d boundary conditions in the experiments demonstrates that quantitative methods for estimating rheology from finite natural structures must take these into account carefully

climatic change on the iberian peninsula recorded in a 30 000 yr pollen record from lake banyoles the banyoles lacustrine sequence shows that the vegetational history of the northeastern iberian peninsula during the last 30 000 yr follows the north atlantic pattern of climatic oscillations the banyoles pollen diagram supported by two calibrated 14c dates and nine u th dates shows a clear interstadial event between 30 000 and 27 000 yr b p a pleniglacial period with minor oscillations that ended abruptly ca 14 420 410 yr b p and a late glacial sequence that records the classical stages described in northern europe the bolling allerod interstade the younger dryas event at 12 000 yr b p u series age and a short warming phase between the younger dryas and the last cold event dated at 11 000 yr b p u series age

an evaluation of criteria to deduce the sense of movement in sheared rocks some of the most useful criteria for the deduction of the sense of shear are summarized for use in areas where unequivocal field evidence is lacking apparently conflicting evidence from rotated pressure shadow regions around porphyroclasts and porphyroblasts is clarified the use of quartz crystallographic fabric asymmetry to deduce the shear sense in the bulk rock should be treated with caution and used only together with detailed microstructural observations

biostratigraphy of the last glacial period in europe the european early weichselian early wurmian is characterized by two long and relatively warm interstadials brorup and odderade which can be traced and correlated with certainty across large parts of europe the amersfoort interstadial described earlier from the netherlands has been included in the brorup and represents the older part of it both great interstadials were forested in north west central and southern europe in the north conifer forests prevailed giving way towards the south to deciduous forests the climatic gradient was distinctly steeper mainly due to southward displacement of the gulf stream the two great interstadials are synchronous with the isotopic stages 5a and 5c in the deep sea cores subsequent to eemian brorup and odderade and from within the context of a continuous series two additional and clearly delimited interstadials have been recorded in a new standard profile from oerel nw germany these are now described as the oerel and glinde interstadials they were not forested and belong to the early pleni weichselian the lower one oerel can probably be correlated with the 3rd weichselian wurmian interstadial in southern central europe ognon ii durnten samerberg 3 while the upper one glinde has so far no known counterpart for the younger pleni glacial it is assumed that there was a long phase during which it was not too cold the formation of humic layers during this phase took place at different times partly due to local edaphic factors so that the relevant 14c dates show a wide scatter the hengelo and denekamp interstadials represent only slight ameliorations which facilitated the formation of shrub tundra and can be recorded in certain regions only

multiscaling of shear zones and the evolution of the brittle to viscous transition in continental crust 1 a new method is introduced for quantifying the scale and the intensity of strain localization from maps of natural shear zones the method employs autocorrelation functions to determine local areal scales of geometric homogeneity these homogenization scales are used to calculate scale dependent localization fractions of deformed rock the strain localization intensity is quantified from measurements of mean relative to maximum shear strain this approach is used to analyze shear zones on different scales from an exposure cap de creus spain of the fossil brittle to viscous transition bvt changes in the scaling characteristics of shear zones are interpreted to reflect a time sequence of localization during the evolution of the continental bvt we show that shear zone scaling is related to inherited anisotropies older schistosity lithological layering pegmatite bodies and to the predominant mode of deformation brittle viscous the length to width ratio of shear zones increases with their length up to the meter scale and decreases for larger length scales as they evolve from isolated shear fractures to interconnected mylonitic shear zones variations in strain localization intensity calculated along a single shear zone indicate that such shear zones weakened from their brittle tips to their mylonitic centers thus driving their propagation and growth to larger scales our results imply that the bvt evolves by network widening a process whereby strain localizes on progressively larger scales until a dense network of weak mylonitic layers tens to hundreds of meters wide and hundreds to thousands of meters long forms subparallel to the regional shearing plane

gisp2 oxygen isotope ratios the gisp2 oxygen isotope record with its high resolution detail yields crucial information on past climate change the glacial 18o oscillations of the gisp2 core with their very fast onsets are templates of a prototype oscillation of variable duration with an amplitude of 3 9 the halfway mark of the cold warm transition is reached in 2 years the top is reached in 50 years the 18o time gradient of the leading front is about 7 8 per 100 yr after reaching the top 18o slowly declines by 0 14 per 100 yr the duration of 18o decline varies from a couple of centuries for fast oscillations to about 4000 yr for slower ones the subsequent 18o downturn during the warm cold transition has a 18o time gradient of 3 2 per 100 yr and lasts about 80 yr

epica dome c 2 drilling operations performances difficulties results the european project for ice coring in antarctica epica dome c 2 edc2 drilling was concluded on 21 december 2005 a few metres above bedrock the drilling was stopped both for environmental reasons and because of the drilling difficulties encountered in warm ice this paper describes in detail the progress and the performance of the epica drill including the procedures needed to penetrate into warm ice and their effects on core quality some drill technical data are also presented

the epica dronning maud land deep drilling operation we report on the epica dronning maud land east antarctica deep drilling operation starting with the scientific questions that led to the outline of the epica project we introduce the setting of sister drillings at northgrip and epica dome c within the european ice coring community the progress of the drilling operation is described within the context of three parallel deep drilling operations the problems that occurred and the solutions we developed modified procedures are described such as the monitoring of penetration rate via cable weight rather than motor torque and modifications to the system e g closing the openings at the lower end of the outer barrel to reduce the risk of immersing the drill in highly concentrated chip suspension parameters of the drilling e g corebreak force cutter pitch chips balance liquid level core production rate and piece number are discussed we also review the operational mode particularly in the context of achieved core length and piece length which have to be optimized for drilling efficiency and core quality respectively we conclude with recommendations addressing the design of the chip collection openings and strictly limiting the cable load drop with respect to the load at the start of the run

progressive deformation in anisotropic rocks abstract field observations show that the majority of crustal rocks possess a penetrative foliation defined by either compositional layering preferred orientations of crystals or both ductile deformation involving planar anisotropy of viscosity can be characterized by an anisotropy factor q n r s the ratio of the bulk viscosities in pure and simple shear respectively this ratio of the normal and shear viscosities may be determined analytically if the anisotropy is resolvable in a multilayer sequence with individual laminae of isotropic viscosity in that case the resistance to normal compression will be largely controlled by the competent layers whereas the resistance to shear is controlled by the soft layers more specifically the viscosities of the individual laminae add up like resistances in series and in parallel in the expressions for the normal and shear viscosities respectively the reorientation of the bulk stress within an anisotropic multilayer is systematically investigated for a range of anisotropy factors the mode of progressive deformation is controlled only by the anisotropy factor and the orientation of the principal deviatoric stress the rate of deformation can be scaled if the bulk normal viscosity and the magnitude of the principal deviatoric stress are also known the results are illustrated in a series of nomograms showing the spectrum of strain and rotation histories possible in rock volumes deforming with planar anisotropy it appears that with increasing anisotropy factor the deformation spectrum will narrow on simple shear irrespective of the orientation of the background or bulk deviatoric stress axes plane strain and isochoric conditions are assumed throughout the analysis

heat generated by cutting ice in deep ice core drilling in order to understand and solve the warm ice problem in deep ice core drilling we applied the metal cutting theory to ice and estimated the heat generated during ice coring taking into account the mechanical and thermal properties of the ice and cutters we found that 1 most of the heat in cutting is generated by shear deformation at the shear plane of ice and the heat could increase the chip temperature by several degrees 2 the rake angle of the cutter has more influence on the temperature increase in chips than the barrel rotation speed and penetration pitch 3 if the cutter is made of a material with larger thermal conductivity the temperature increase in the chips can be reduced and 4 if the density of the liquid is less than the density of ice the cutting chips sink to the bottom and the friction heat generated by the drill head and slush can raise the ambient temperature of the drill head by several degrees

generation and modification of finite strain patterns by progressive thrust faulting in the laksefjord nappe finnmark abstract using deformed conglomerates as finite strain markers a strain map of the base of the laksefjord nappe has been produced and is presented finite strains are predominantly of flattening type and are explained in terms of a variable simple shear superimposed on a constant pure shear strain patterns are examined in terms of their three dimensional geometry and are shown to be clearly related to the presence of the basal laksefjord thrust late brittle thrust faulting has modified early finite strain patterns and a progressive thrusting model is presented to explain present day strain patterns finite strains developed in a mid crustal sub horizontal shear zone at lower greenschist facies account for only a small proportion of total nappe translation

weichselian palynostratigraphy palaeovegetation and palaeoenvironment the record from lago grande di monticchio southern italy abstract the palynostratigraphic record from lago grande di monticchio s italy is presented an independent sedimentation rate based chronology provides an age of 101 530 calendar years bp for the lowermost sediments sampled this chronology enables assessment of the rapidity of vegetation changes during the last glacial contrary to widely held views the vegetation showed numerous large magnitude changes in periods of

lithospheric shear zones and mantle crust connections abstract a crustal scale ductile shear zone network in the precambrian granulite facies crust of madagascar is examined to determine the nature of the connections between the mantle and lower crust based on three independent data sets field and satellite mapping c and o isotope geochemistry and gravimetry this crust is divided into three zones 1 outside of shear zones 2 minor shear zones that are 350 km long up to 1000 km and 20 35 km wide the mantle is uplifted by about 10 km beneath the major shear zones the major shear zones are rooted in and are inferred to be controlled by the mantle they directly tapped mantle derived co 2 the small scale minor shear zones were controlled by crustal processes and focused crustally derived h 2 o rich co 2 fluids the regular distribution of the shear zones on a crustal scale is in agreement with models of buckling of the continental lithosphere in a compressional context the propagation of these mechanical instabilities promoted and channelled fluid flow these major pan african shear zones thinned the crust and were reactivated during the subsequent drifting of madagascar and opening of the indian ocean during jurassic to cretaceous times they also controlled many of the brittle fault zones in the overlying sedimentary basins mantle rooted large scale shear zones are inferred to be a general feature of cratonic areas reactivated by shear zone systems

displacement and strain patterns from naturally occurring shear zone terminations abstract strain distribution patterns are described from several naturally occurring ductile shear zone terminations and a two fold classification is suggested type i termination patterns show a symmetrical decrease in strain area and intensity and are associated with very low shear strain values in the main shear zone the more common type ii termination patterns show a symmetrical increase in strain area with decrease in strain intensity some brittle ductile examples of type ii terminations contain secondary shears that resemble splay faults all the available evidence suggests that the deformation near the terminations of these shear zones is not plane strain nor do the observed strain patterns readily fit the existing theoretical models

vegetation history and palaeoclimate of the last glacial period at lago grande di monticchio southern italy a high resolution palynological study of a 51 m core from lago grande di monticchio southern italy has provided a palaeonvironmental record for the last glacill a annual lamination based chronology supported by radiometric and tephrochronological dates provides an absolute timescale for this record that spans 76 300 years correlations are established between the pollen stratigraphy the grip ice core 18o record and foraminiferal assemblages from atlantic core v23 81 both dansgaard oeschger and heinrich events are reflected by changes in the pollen stratigraphy revised dates are estimated for heinrich events h1 h6 a quantitative palaeoclimate reconstruction based upon the pollen data provides evidence of the climate changes in southern italy associated with these and other fluctuations during the last glacial

rapid environmental changes in southern europe during the last glacial period oxygen isotope records from greenland ice cores1 2 indicate numerous rapid climate fluctuations during the last glacial period north atlantic marine sediment cores show comparable variability in sea surface temperature and the deposition of ice rafted debris3 4 5 in contrast very few continental records of this time period provide the temporal resolution and environmental sensitivity necessary to reveal the extent and effects of these environmental fluctuations on the continents here we present high resolution geochemical physical and pollen data from lake sediments in italy and from a mediterranean sediment core linked by a common tephrochronology our lacustrine sequence extends to the past 102 000 years many of its features correlate well with the greenland ice core records demonstrating that the closely coupled ocean atmosphere system of the northern hemisphere during the last glacial4 extended its influence at least as far as the central mediterranean region numerous vegetation changes were rapid frequently occurring in less than 200 years showing that the terrestrial biosphere participated fully in last glacial climate variability earlier than 65 000 years ago our record shows more climate fluctuations than are apparent in the greenland ice cores together the multi proxy data from the continental and marine records reveal differences in the seasonal character of climate during successive interstadials and provide a step towards determining the underlying mechanisms of the centennial millennial scale variability

strain and shape fabric variations associated with ductile shear zones abstract the foliated and compositionally banded granitic orthogneisses in the central core of the maggia nappe a lower pennine basement nappe of the central swiss alps are shown to be the sheared equivalent of late hercynian age granitic intrusions these ductile shear zones show mineral assemblages in amphibolite facies are alpine in age and form an anastomosing network enclosing remnant lozenge shaped pods of relatively undeformed rock the foliation developed within the shear zones concomitantly with a change in shape of quartz grain aggregates from initially equidimensional through tear drop shapes to ribbon like aggregates these shape changes occurred by intracrystalline glide together with intercrystalline slip on deformation induced planar surfaces

an analysis of eemian climate in western and central europe on the basis of 31 pollen diagrams and additional data for botanical macrofossils an analysis is made of the last interglacial eemian climatic history in western and central europe the main tool for this analysis is the climatic indicator species method only selected woody species are used for the quantification of data partial climatic range diagrams are presented for abies alba acer monspessulanum acer tataricum buxus sempervirens tilia tomentosa the problem of time correlation and pollen zonation of the eemian is discussed the climatic analysis itself is based on an improved version of the indicator species method in this version not every site is analysed for its climatic values instead maps and tables on the migrational history of hedera ilex buxus abies and species of acer tilia and abies are the basis for climatic maps showing respectively january and july isotherms for the periods of the corylus zone e4a and the carpinus zone e5 it is concluded that mean january temperatures were as much as 3 c higher at amsterdam the netherlands than at present and mean temperatures in july were 2 c higher however the thermal maximum in winter was later zone e5 than the summer thermal maximum zone e4a winter temperatures changed parallel to rise and fall of global sea level precipitation changes are more difficult to estimate in the first part of the eemian precipitation must have been relatively low but from zone e4b onward it increased to higher values reaching 800 mm and probably substantially more in zones e5 and e6 hence the eemian climate was in its beginning relatively more contintental and later from e4b onward more oceanic however as compared with the holocene the eemian climate was generally speaking more oceanic

was the climate of the eemian stable a quantitative climate reconstruction from seven european pollen records the aim of the present study is to estimate the range of the climatic variability during the eemian interglacial which lasted about 10 000 years marine isotopic stage 5e the modem pollen analogue technique is applied to seven high resolution pollen records from france and poland to infer the annual precipitation and the mean temperature of the coldest month the succession of pollen taxa and the reconstructed climate can be interpreted coherently the warmest winter temperatures are centred in the first three millennia of the eemian interglacial during the mixed oak forest phase with quercus and corylus as dominant trees a rapid shift to cooler winter temperatures of about 6 degrees to 10 degrees c occurred between 4000 and 5000 years after the beginning of the eemian related to the spread of the carpinus forest this shift is more obvious for the reconstructed temperatures than for precipitation and is unique and irreversible for the whole eemian period following this climatic shift of the eemian variations of temperature and precipitation during the fast 5000 years were only slight with an amplitude of about 2 degrees to 4 degrees c and 200 to 400 mm yr the estimated temperature changes were certainly not as strong as those reconstructed for the stage 6 5e termination or the transition 5e 5d this is consistent with the constantly high ratio of tree pollen throughout the eemian indicative of a succession of temperate forest types this gradual transition between different forest landscapes can be related to intrinsic competition between the species rather than to a drastic climatic change c 1998 elsevier science b v all rights reserved

weichselian palynological records from southern europe correlation and chronology abstract the high resolution independently dated palynostratigraphic record from lago grande di monticchio spanning the last 101 530 calendar years provides a basis for re evaluating the correlations between palaeoenvironmental events in europe during the last glacial as well as a means to determine their chronology the interstadial events recorded from various localities throughout europe are combined into a single scheme of correlations and a chronological framework is suggested this provides a basis for assessing the evolution of the vegetation and environmental patterns across europe during the last glacial revealing a general tendency for the latitudinal climatic gradient to have been steeper than it has been during the holocene the vegetation has also generally been subject to greater moisture deficiency either because of prevailing climatic conditions or as a reflection of the lower atmospheric concentration of co 2 the scheme of correlations is shown to be capable of being extended beyond europe not only to marine and ice core records from the north atlantic region but also to a palynological record from north west north america

the palomares brittle ductile shear zone of southern spain the palomares shear zone is a major neogene quaternary strike slip zone which transects the crust of the betic cordillera in se spain the shear zone and the mechanisms that led to its formation are discussed and illustrated on the basis of detailed compilations of both the local and regional geology it is emphasized that the formation of the palomares shear zone was not an isolated tectonic event but part of a complex neogene tectonic history the neogene evolution of the betic rif orogen and its central alboran basin is characterised by the following events 1 emplacement of the alboran diapir with resulting nappe shedding from the overlying crust between 25 and 20 ma ago 2 onset of the subsidence of the alboran basin between 20 and 15 ma ago due to cooling of the alboran diapir and the overlying crust 3 formation of the cabo de gata volcanic chain between 15 and 8 ma ago and 4 refolding of the nappe sheets in the betic rif orogen into a basin and range structure about 7 ma ago continuous activity of the crevillente fault of southern spain may have occured over a period from 20 ma ago up to the present the interrelated palomare fault in se spain was probably formed between 15 and 8 ma ago and seem to be active still the palomares shear zone affects a rock volume 44 km wide at least 80 km long and 30 km deep a shear strain distance diagram constructed across the palomares shear zone and its axial palomares fault involves a new method to estimate or constrain the shear strain magnitude along brittle ductile shears the typical tensor shear strain rates in the approximately 20 km thick ductilely deformed walls of the palomares fault are of the order 10 13 10 14 s 1 the tensor shear strain rate along the palomares fault itself is of the order 10 12s 1 and the time averaged relative displacement rate of its walls is about 2 mm a 1 the range of strain rates within the palomares shear zone are interpreted to be due to a combination of various flow softening mechanisms geometric structural thermal and strain rate softening these softening mechanisms might explain the difference in vertically averaged viscosities of 1020 pa s and 1025 pa s or lower suggested for the crustal rocks in the palomares fault proper and that of the relatively rigid boundaries of the palomares shear zone respectively

determination of finite strain from passive initially planar markers deflected in ductile rocks undergoing simultaneous superposition of heterogeneous strains abstract from an empirical model of strain in ductile heterogeneous shear zones simultaneously undergoing a bulk pure shear we study the influence of the parameters of the deformation on the shape changes of passive initially planar markers and describe a method for determining the finite strain and even sometimes the instantaneous strain from these deflected markers

ecological thresholds and patterns of millennial scale climate variability the response of vegetation in greece during the last glacial period the regional expression of millennial scale climate variability during the last glacial is examined with particular reference to the vegetation response in greece inspection of three pollen records from contrasting bioclimatic areas suggests that differences in the magnitude of cold events as recognized in the north atlantic and western mediterranean are expressed in terms of tree population changes only in areas with a range of favorable habitats by contrast records from sites where populations approach their tolerance threshold do not appear to resolve differences in the amplitude of the climate oscillations understanding the importance of local factors in modulating the biological response to climate change is critical when attempting to establish the spatial pattern of millennial variability

the role of hydrochlorofluorocarbon densifiers in the formation of clathrate hydrates in deep boreholes and subglacial environments clear evidence for the formation of mixed clathrate hydrates of air and hydrochloro fluorocarbon densifier known as hcfc 141b sometimes also called r 141b is found by means of synchrotron x ray diffraction and raman spectroscopy on a sample recovered from the bottom of the epica dronning maud land deep borehole in antarctica subglacial water sgw appears to have reacted with the drilling liquid to build a large lump of clathrate hydrate the hydrate growth may well have been accelerated by the stirring of the sgw densifier mixture during drilling moreover dissolved air in the sgw appears to have participated in the formation of mixed hydrates of air and hcfc 141b as evidenced by the concomitant appearance of raman signals from both constituents our findings elucidate to some extent the meaning of earlier accounts of the formation of heavy chips that may sink to the bottom of the borehole possibly affecting or even impeding the drilling advance these observations raise concerns with respect to the use of hcfc 141b densifiers in ice core drilling liquids under warm ice conditions

the holocene landscape history of the nw italian coasts cores from four coastal plains of the mar ligure sea in n tuscany and e liguria italy were investigated by means of pollen analysis to delineate the holocene landscape history of the nw italian coasts in the first half of the holocene c 9800 7000 cal yr bp all four sites show elevated percentages of abies pollen which suggest the local presence of fir woods with ulmus tilia etc in the second half of the holocene from 7000 cal yr bp abies becomes locally extinct along the coasts leaving space for the development of mosaic landscapes formed by open meso thermophilous woods with deciduous quercus alnus corylus and mediterranean maquis with erica cf arborea the new data represent a significant contribution to the reconstruction of the landscape history of the nw italian coasts and of the history of fir in italy along all examined cores discontinuous pollen records show that initially the coastal areas were characterized by retrodunal wetlands after c 6000 cal yr bp only the large

great slave lake shear zone canadian shield reconstructed vertical profile of a crustal scale fault zone abstract the great slave lake shear zone gslsz of the northwestern canadian shield a 25 km wide early proterozoic transcurrent dextral mylonite zone is a type example of a crustal scale fault zone profile with time 1 1 the metamorphic grade decreased from granulite to greenschist facies 2 2 the locus of high strain narrowed and jumped laterally abandoning relatively older mylonites progressively younger mylonites represent both cooler temperatures and lower pressures thus the sequence of narrowing mylonite belts represents a series of progressively shallower seated sections through the gslsz 3 3 deformation evolved through the brittle ductile transition initially producing non dilational penetrative breccias followed first by discrete non dilational faulting and subsequently by dilational quartz stockworks developing crustal scale shear zones grow to an optimum width dictated by the requirement of minimum geologically reasonable strain rates for given conditions of wall rock rheology and displacement rate independent of variations in relative plate motion mature shear zones change width and migrate laterally as a function of inferred thermally activated rheological changes within the wall rocks

evidence for last interglacial chronology and environmental change from southern europe establishing phase relationships between earth system components during periods of rapid global change is vital to understanding the underlying processes it requires records of each component with independent and accurate chronologies until now no continental record extending from the present to the penultimate glacial had such a chronology to our knowledge here we present such a record from the annually laminated sediments of lago grande di monticchio southern italy using this record we determine the duration 17 70 0 20 ka and age of onset 127 20 1 60 ka b p of the last interglacial as reflected by terrestrial ecosystems this record also reveals that the transitions at the beginning and end of the interglacial spanned only 100 and 150 years respectively comparison with records of other earth system components reveals complex leads and lags during the penultimate deglaciation phase relationships are similar to those during the most recent deglaciation peaks in antarctic warming and atmospheric methane both leading northern hemisphere terrestrial warming it is notable however that there is no evidence at monticchio of a younger dryas like oscillation during the penultimate deglaciation warming into the first major interstadial event after the last interglacial is characterized by markedly different phase relationships to those of the deglaciations warming at monticchio coinciding with antarctic warming and leading the atmospheric methane increase diachroneity is seen at the end of the interglacial several global proxies indicate progressive cooling after 115 ka b p whereas the main terrestrial response in the mediterranean region is abrupt and occurs at 109 50 1 40 ka b p

theoretical strain patterns in ductile zones simultaneously undergoing heterogeneous simple shear and bulk shortening abstract structures observed in ductile shear zones show that deformation is continuous and strain is heterogeneous this leads us to define a simple model for shear strain rate when a shear zone simultaneously undergoes simple shearing and pure shearing contraction or extension the condition of continuity of deformation shows that must be a function of time integration of the deformation rate equations yields the particle paths in the deforming body from these we can determine at any time and at any point in the body the finite strain tensor lengths and orientations of the axes of the finite strain ellipsoid we can therefore define the finite strain trajectories and compare them with orientations of internal structures schistosity tension gashes the particle paths also allow us to study the progressive deformation of passive strain markers

the wurm in nw iberia a pollen record from area longa galicia the pollen record at area longa is the westernmost sequence available for investigation of the last glaciation in continental europe it is located in a region nw iberia for which data from times earlier than the late glacial period are scarce it comprises a series of exposed limnetic levels that lie above an eemian oxygen isotope stage ois 5e beach and are separated by inorganic layers the oldest limnetic level level i attributed to the early glacial period ois 5a to ois 5d shows a dominance of woodland with high proportions of fagus pollen and is tentatively identified with st germain i the lower pleniglacial ois 4 level ii records a stadial landscape of grassland and shrub level iii from the pleniglacial interstade ois 3 reflects a complex period in which three warmer woodland phases alternated with periods of more open vegetation this cyclical behavior correlates with the ice core isotope record and with the general tendencies observed in other wurmian pollen records but the composition of our pollen profiles differs from those observed in these other records in nw iberia the dominant trees were deciduous taxa not conifers of particular note is the presence of lowland fagus woodlands during the pre wurm and the occurrence of carpinus considerably farther west than the boundary of its current distribution in the iberian peninsula

late quaternary multiple incised valley systems an unusually well preserved stratigraphic record of two interglacial valley fill successions from the arno plain northern tuscany italy

theoretical and natural strain patterns in ductile simple shear zones abstract a simple empirical model representing the variation of shear strain throughout a simple shear zone allows us to determine the evolution of finite strain as well as the progressive shape changes of passive markers theoretical strain patterns intensity and orientation of finite strain trajectories deformed shapes of initially planar equidimensional and non equidimensional passive markers compare remarkably well with patterns observed in natural and experimental zones of ductile simple shear intensity and orientation of schistosity shape changes of markers foliation developed by deformation of markers the deformed shapes of initially equidimensional and non equidimensional passive markers is controlled by a coefficient p the product of 1 1 the ratio between marker size and shear zone thickness 2 2 the shear gradient across the zone for small values of p approximately p p lead to retort shaped markers this theoretical study also allows us to predict throughout a simple shear zone various relationships between the principal finite strain trajectory planar passive markers and foliations developed by deformation of initially equidimensional passive markers

flow and strain patterns at the terminations of tapered shear zones with the help of corner flow theory this paper numerically analyzes the deformation pattern at the terminations of tapered shear zones the walls of which are rigid and move parallel to each other in opposite directions the overall flow pattern is characterized by curvilinear particle paths that show convexity towards and opposite to the tapering direction respectively for low 10 inclinations of the wall verging opposite to the sense of wall movement in tapered shear zones there are two distinct fields of instantaneous shortening and extension parallel to the direction of wall movement numerical models reveal that the finite strain distributions are generally asymmetrical with larger strain concentration occurring near the wall verging opposite to sense of wall movement the s foliation trajectories show a curvilinear pattern convexing against the tapering direction the analysis of rotationality vorticity indicates that the sense of vorticity near the synthetically verging wall is reverse to the sense of wall movement however wk is one everywhere within the shear zone

volume loss and tectonic flattening strain in granitic mylonites from the blue ridge province central appalachians abstract granitic mylonites from the blue ridge province in the central appalachians demonstrate the contribution of various deformation mechanisms to the strain geometry that developed during greenschist facies deformation in thrust related shear zones strain accumulated through cataclasis in feldspar crystal plastic processes in quartz and a significant contribution of pressure solution in both feldspar and quartz strain analysis was performed using r f f techniques on quartz grain shapes and by measuring stretched and boudinaged feldspars petrographic and geochemical evidence indicates that deformation ranged from isovolumetric to upwards of 60 bulk rock volume loss quartz and feldspar strain values plot within the field of apparent flattening feldspars in both xz and yz sections are boudinaged and separated by transverse veins and record a true tectonic flattening strain strain data indicate that the bulk deformation path in shear zones throughout the blue ridge province significantly deviated from plane strain

high resolution palynological record off the iberian margin direct land sea correlation for the last interglacial complex abstract we present high resolution pollen dinocyst and isotopic data for the last interglacial complex from marine core md952042 southwestern margin of the iberian peninsula 37 48 n 10 10 w 3148 m direct land sea correlation from this core indicates that during this period north atlantic sea surface temperatures were in phase with iberian climate our palynological analysis suggests a younger dryas like event at the marine isotope stage mis 6 5 transition the analysis also indicates that the eemian spans from the lightest isotopic values of mis 5e ca 126 ky bp to the heavier isotopic values towards the mis 5e 5d transition therefore the eemian is not entirely equivalent to mis 5e pollen analysis identifies four climatic phases of low amplitude during the eemian a mediterranean climate in southwestern europe is gradually replaced by oceanic conditions the middle of the eemian is characterized by an increase in precipitation on the land and ocean associated with a slight cooling this seems to be the result of a displacement of the polar front as far south as southern europe during this period after the eemian three relatively short climatic phases on land melisey i st germain ia and montaigu cold event occurred contemporaneously with three shifts of sea surface temperatures the montaigu event first identified in terrestrial pollen sequences is therefore also recorded in core md952042 on the basis of pollen dinocyst and planktonic isotopic data our results also show that the warm periods of mis 5 are not characterized by similar climatic conditions on land

the last climatic cycle at kopais central greece thick lacustrine sequences from southern europe provide an opportunity to derive continuous records where the chronostratigraphical position of pre holocene stages can be determined with increased confidence here high resolution sediment and pollen analytical results from a 60 m core recovered from the kopais basin central greece spanning the interval from the last interglacial to the early holocene are presented the record shows distinct shifts between open vegetation periods of increased erosion with sediment inwashing and forest periods associated with calcite precipitation in the lake the sequence of major events of the last climatic cycle contained at kopais bears strong similarities to other records in greece but also reveals the presence of high frequency oscillations with higher amplitudes than previously seen at other sites

earthquakes and rock deformation in crustal fault zones the physical origin of earthquakes lies ultimately in the geological structure of fault zones and the deformation processes that occur therein in response to tectonic stress although the possibility now exists that the nucleation regions for large earthquakes at depths of 10 km may shortly become directly accessible by deep drilling our present knowledge of fault structure and the shallow earthquake source is derived largely from a variety of indirect sources these include seismological studies surface studies of fault zones and earthquake ruptures geodetic information on modes of fault slip geophysical constraints on fault zone structure and rheology and information garnered from materials science and experi mental rock deformation studies of fault zone structure and the rock products of faulting provide complementary information on deformation processes at depth in fault zones although descriptions of fault rocks are widespread in the geological literature e g spry 1969 higgins 1971 it is only in the past decade that they have begun to be interpreted in the context of the physical conditions and processes prevalent in seismically active fault zones at different crustal depths sibs on 1977 watts williams 1979 anderson et a11983 wise et ai 1984 such interpretations are still at an early stage but the deformation textures and structural associations of fault rocks have already been shown to have the potential to yield information on such diverse topics as shear stress levels power dissipation and seismic efficiency during earthquake faulting on fluid pressure levels and episodic fluid flow accompanying

climatic signature of two mid late holocene fluvial incisions formed under sea level highstand conditions pisa coastal plain nw tuscany italy abstract a multi proxy stratigraphic geomorphological palynological geophysical study of mid late holocene deltaic alluvial deposits beneath the pisa plain tuscany italy reveals short term enhances of fluvial activity under relative sea level highstand hst conditions last 7000 cal yr bp early hst delta progradation led to the progressive infill of a broad lagoon area 5000 cal yr bp followed by the development of a stable alluvial depositional environment 4000 cal yr bp the intense phase of alluvial aggradation was punctuated by two events of enhanced fluvial incision that cut down to 10 m the underlying lagoonal substrate the two erosive events which reflect centennial scale changes in the aggradation degradation ratio are chronologically constrained to the eneolithic bronze age transition 3800 cal yr bp and to the bronze iron age transition 2900 2800 cal yr bp respectively a detailed pollen profile highlights the correlation between these erosive events and two phases of increased humidity abies peaks 1 and 2 recorded in several sites of europe this correlation suggests a key role of climate fluctuations in triggering channel incision the peculiar high compressibility of the lagoonal substrate can also have acted as a factor able to foster the deepening of the channels in contrast the role of relative sea level changes and human impact on the activation of the two erosive processes appears negligible

nucleation growth and structural development of mylonitic shear zones in granitic rock abstract well exposed shear zones in granitic rock of the sierra nevada are preserved in various degrees of development facilitating interpretation of the mechanisms of shear zone nucleation and growth field relations suggest that these shear zones formed by shear localization within pre existing aplite dikes that served as tabular zones of inherent weakness crossing dikes provide a measure of the offset at several points along the shear zones apparently the shear zones grew in width as they accumulated offset and propagated longitudinally by end to end linkage of approximately coplanar aplite dike segments propagation caused discontinuous dikes or dike segments to be joined giving the shear zones a forked or eye shaped trace pattern some shear zones have developed opening fractures at their tips analogous to the splay fractures that form near the tips of small faults these shear zones provide an excellent opportunity to study the processes involved in natural shear zone formation in granitic rocks where shear is localized along pre existing zones of inherent weakness they may serve as useful analogs for the growth and development of larger scale faults that involve ductile shearing

european climatic response to millennial scale changes in the atmosphere ocean system during the last glacial period abstract pollen foraminifer dinocyst and coarse lithic high resolution analyses and 18 o measurements have been carried out for the last glacial section of marine core md95 2042 located near the southwestern margin of the iberian peninsula the pollen data indicate a high frequency of vegetational changes on the adjacent continent during this period suggesting a climatic variability very similar to that of the dansgaard oeschger cycles recorded by the greenland ice cores the detailed direct correlation of the terrestrial and marine proxy data from core md95 2042 indicates a three phase pattern of heinrich events in land and ocean environments the first and last phases of the h5 and h4 events are characterized by a mild and humid climate in southwestern europe probably associated with the european origin of the ice rafted detritus the middle phase exhibits a cold and dry climate in iberia linked with the maximum input of ice rafted detritus this phase seems to correspond with the laurentide ice sheet surges between the heinrich events several cold and dry periods on land are correlated with stades of the dansgaard oeschger cycles the impact of the dansgaard oeschger stades in southwestern europe seems to be preferentially connected to the cold winter air masses reaching this mid latitude region

incremental deformation and fabric development in a kcl mica mixture abstract the history of deformation and of mica reorientation is described in a kcl mica mixture in the middle of a kink like experimental shear zone the history was reconstructed by deforming several specimens to successively greater total strains and assuming the more deformed specimens passed through the states of strain and fabric exhibited by the less deformed specimens a pseudo differentiated layering is described which arises from the original network distribution of the mica grains without benefit of any differentiation process a comparison is made between the observed mica fabrics at various strains and those predicted by the march model taking the measured initial preferred orientation of the micas into account the actual reorientation processes in the material are found to be more efficient than the march transformation at shortening strains less than about 70 but less efficient at higher strains these departures from marchian behavior are explaned qualitatively comparison is also made between observed and predicted intensities of mica preferred orientation assuming a hypothetical random orientation of micas in the starting material for the march calculation

strain patterns in an ice cap and implications for strain variations in shear zones glacier flow is a form of gravity tectonics in thin sheets characterized by the development of large strains foliation and folds strain is difficult to measure in ice but numerical methods provide a good means of estimating cumulative strains in simple terms flow in an ice cap involves vertical flattening at the center with bottom parallel shear increasing in intensity downwards and outwards in steady state cumulative strains will be plane if flow is two dimensional as in parts of many valley glaciers and some ice caps and of flattening type if lateral extension occurs normal to the flow direction as in many ice sheets in both radial and plane flow strain gradients will be large vertically and low horizontally outwards cumulative strain magnitude can be extremely large near the base and at the margin z is everywhere sub vertical if flow is unsteady more complex strain patterns develop even if changes in the flow field are slight over bedrock ridges flow perturbations can lead locally to rotations greater than those of the quasi simple shear acting near the base in steady state flow this may cause the x direction of the cumulative strain to rotate through the shear plane in the neighborhood of the perturbation in which case strain magnitudes subsequently diminish leading to low or zero strains in plane flow and to constrictional strains in radial flow in the latter case x lies horizontal and perpendicular to the flow direction and we have local constrictional strain in an overall flattening field the zones of perturbed strain tend to be associated with the inverted limbs of recumbent folds shear zones in rocks are expected to show similar patterns of strain perturbation

a long pollen record from lac du bouchet massif central france for the period ca 325 to 100 ka bp ois 9c to ois 5e abstract pollen analysis was carried out on sediments older than the wurm pleniglacial ois 4 in two new sequences h and i derived from the centre of lac du bouchet massif central the inferred vegetation history enables for the first time in france five temperate episodes to be defined which pre date the last interglacial these temperate episodes alternate with episodes during which the changes in vegetation are indicative of glacial climates comparison of these climatic episodes with the oceanic isotope record shows that the pollen record of sequences h and i from lac du bouchet spans the time interval from ois 9c ussel interstadial to ois 5e ribains eemian interglacial in the organic sediments from the amargiers interstadial ois 9a a trachytic layer ar ar dated to ca 275 ka enables a correlation to be established with the upper part of a sequence derived from the nearby praclaux crater the lower part of this sequence being of holsteinian age ois 11c the cross dating of the pollen sequences from lac du bouchet cores h i and d and from praclaux provides a complete record from the massif central southern france of successive glacial and interglacial episodes that span the last ca 400 ka that is the interval from the holsteinian to the holocene

vegetation dynamics during the last interglacial glacial cycle in the arno coastal plain tuscany western italy location of a new tree refuge abstract pollen analysis of the pre last glacial maximum succession of a 105 m long continuous core from tirrenia tuscany provides evidence for the existence of an area of relatively high ecological stability where the effects of climate change were mitigated the chronological framework of the vegetation record spanning the last interglacial glacial cycle was established by i ams 14c dating ii correlation with well dated pollen sequences and iii local stratigraphical constraints a high lithological and sedimentological variability with facies associations changing from fluvial to alluvial and coastal plain enhances the palaeoenvironmental control on pollen distribution thus helping to discriminate the impact of local factors on vegetation history the most remarkable evidence however is represented by the continuous record of temperate trees throughout the whole glacial period which provides useful indications on the location and nature of cold stage refugia most of the vegetation changes recorded in the core can be compared to the vegetation history of the last interglacial glacial cycle from southern europe as a whole in addition local geographic and environmental features account for a more complex and varied floristic composition only the last phase of the penultimate glacial mis6 which was characterized by the diffusion of an arid steppe tundra is recorded at the base of the core the subsequent last interglacial mis5e interval shows a poor and scattered pollen content due to the instability of the sedimentary environment nevertheless it provides evidence of both global and local controls on vegetation dynamics as indicated by the initial expansion of thermophilous forests and the remarkably late diffusion of conifers pinus abies picea forests respectively similarly the transition to the last glacial mis5b and 5a in the core is characterized by a reduced vegetation response to the typical stadial interstadial climate variability this is because the diffusion of a characteristic pioneer vegetation mainly represented by hippophae cf rhamnoides helped to confer to the local environment a high ecological stability buffering vegetation changes finally during the last glacial mixed broad leaved deciduous and pinus forests widely occupied the arno coastal plain demonstrating that this area acted as an important tree refuge local ecological conditions favourable to tree survival were determined mainly by i high precipitation as a function of orographic uplift of air charged with moisture from the nearby tyrrhenian sea ii mild temperatures which were also influenced by proximity to the sea and iii high topographic variability providing a series of suitable microenvironments

the last climatic cycle at la grande pile vosges france a new pollen profile a new pollen diagram has been made from an old unanalyzed core from la grande pile gp xx correlations with the previous work of woillard 1975 1978 leads to the following conclusions the end of the eemian was marked by a minor climatic change prior to the melisey i stadial the ognon ii and ognon iii interstadials are not consistent and correspond to the level of reworking of mesophilous taxa during the last pleniglacial the limitations of the botanical interpretation of pollen spectra from the last pleniglacial are underlined lastly bruckenthalia and larix are identified for the first time at la grande pile the respective roles of these taxa following the eemian are additional arguments for correlating the st germain i and ii with the early weichsel interstadials in the north of middle europe

european vegetation during marine oxygen isotope stage 3 european vegetation during representative warm and cold intervals of stage 3 was inferred from pollen analytical data the inferred vegetation differs in character and spatial pattern from that of both fully glacial and fully interglacial conditions and exhibits contrasts between warm and cold intervals consistent with other evidence for stage 3 palaeoenvironmental fluctuations european vegetation thus appears to have been an integral component of millennial environmental fluctuations during stage 3 vegetation responded to this scale of environmental change and through feedback mechanisms may have had effects upon the environment the pollen inferred vegetation was compared with vegetation simulated using the biome 3 5 vegetation model for climatic conditions simulated using a regional climate model regcm2 nested within a coupled global climate and vegetation model genesis biome despite some discrepancies in detail both approaches capture the principal features of the present vegetation of europe the simulated vegetation for stage 3 differs markedly from that inferred from pollen analytical data implying substantial discrepancy between the simulated climate and that actually prevailing sensitivity analyses indicate that the simulated climate is too warm and probably has too short a winter season these discrepancies may reflect incorrect specification of sea surface temperature or sea ice conditions and may be exacerbated by vegetation climate feedback in the coupled global model

drilling comparison in warm ice and drill design comparison for the deep ice core drilling community the 2005 06 antarctic season was an exciting and fruitful one in three different antarctic locations dome fuji epica dml and vostok deep drillings approached bedrock the ice water interface in the case of vostok emulating what had previously been achieved at northgrip greenland summer 2003 and 2004 and at epica dome c2 antarctica season 2004 05 for the first time in ice core drilling history three different types of drill kems jare and epica simultaneously reached the depth of warm ice under high pressure after excellent progress at each site the drilling rate dropped and the drilling teams had to deal with refrozen ice on cutters and drill heads drills have different limits and perform differently in this comparative study we examine depth pressure temperature pump flow and cutting speed finally we compare a few parameters of ten different deep drills

evidence for general instability of past climate from a 250 kyr ice core record recent results1 2 from two ice cores drilled in central greenland have revealed large abrupt climate changes of at least regional extent during the late stages of the last glaciation suggesting that climate in the north atlantic region is able to reorganize itself rapidly perhaps even within a few decades here we present a detailed stable isotope record for the full length of the greenland ice core project summit ice core extending over the past 250 kyr according to a calculated timescale we find that climate instability was not confined to the last glaciation but appears also to have been marked during the last interglacial as explored more fully in a companion paper3 and during the previous saale holstein glacial cycle this is in contrast with the extreme stability of the holocene suggesting that recent climate stability may be the exception rather than the rule the last interglacial seems to have lasted longer than is implied by the deep sea specmap record4 in agreement with other land based observations5 6 we suggest that climate instability in the early part of the last interglacial may have delayed the melting of the saalean ice sheets in america and eurasia perhaps accounting for this discrepancy

evaluating magnetic lineations ams in deformed rocks magnetic lineation in rocks is given by a cluster of the principal axes of maximum susceptibility kmax of the anisotropy of magnetic susceptibility ams tensor in deformed rocks magnetic lineations are generally considered to be the result of either bedding and cleavage intersection or they parallel the tectonic extension direction in high strain zones our ams determinations based on a variety of samples that were taken from mudstones slates and schists from the pyrenees and appalachians show that strain is not the only factor controlling the development of magnetic lineation we find that the development and extent to which the magnetic lineation parallels the tectonic extension direction depends on both the original ams tensor which in turn depends on the lithology and the deformation intensity rocks having a weak pre deformational fabric will develop magnetic lineations that more readily will track the tectonic extension

strain localisation in an orthogneiss laccolith the pinet massif aveyron southern france abstract sheared granitoids of the pinet laccolith southern france display strain gradients from undeformed protolith to s c mylonites and ultramylonites that formed at amphibolite facies of metamorphism we study shear strain distribution at a regional scale and use image processing techniques to measure strain across continuous shear gradients local perturbations of strain intensity seem to represent early stages of shear strain localisation parallel to the main mylonitic foliation our study suggests that localisation of shear strain shows a periodicity at regional and outcrop scales

orientation of nucleating faults in anisotropic media insights from three dimensional deformation experiments abstract physical experiments have been undertaken to investigate the influence of planar rheological anisotropy on the orientation of fault structures in three dimensional flow associated with layer normal shortening the experimental results indicate that plane strain is a special case characterised by the lowest angle between the faults and the principal extension direction for any combination of rheology and flow type during progressive pure shear a model is proposed wherein the role of the anisotropy appears to be two fold first it determines that shear bands operate internally by a mechanism involving rotating slip surfaces during fault nucleation the initial orientation of the faults is determined by the optimisation of the driving processes in the propagating shear bands as a partial function of the angle they make with the external anisotropy second it induces directionally dependent variation in the resistance to flow which manifests itself differently according to the symmetry of the strain ellipsoid in three dimensions x y 1 z in flattening flow it is proposed that anisotropy induced geometrical hardening leads to an increase in the angles made by the shear bands with the principal extension directions of the deformation in constriction the same effect is seen in xz sections but in yz sections it is suggested that the wide range of fault orientations observed is due to anisotropy induced geometrical softening it is possible that the low angle of dip of crustal scale extensional detachment faults may reflect anisotropic behaviour of the lower continental crust

terminations of ductile shear zones abstract we propose a plane strain model for ductile shear zone terminations in rocks that otherwise record no visible shear strain this model may explain the strain distribution patterns in naturally occurring terminations of shear zone which show in the xz plane of finite strain 1 a decrease in the area of finite strain and in strain intensity ellipsoidal or lens like feature and 2 an increase in the strained area as strain intensity decreases splay like or horse tail feature

ice age refugia and quaternary extinctions an issue of quaternary evolutionary palaeoecology abstract quaternary palaeoecology as a discipline involves the analysis of a large range of fossil organisms from the last ca 2 million years this paper considers the role that these quaternary records can take in better understanding the evolution of those organisms we also discuss the surprisingly low uptake of evolutionary biology in quaternary palaeoecological studies this leads us to encourage an advance on both these fronts with a greater degree of collaboration with phylogeographic and ancient dna researchers these discussions accompany a summary of a special issue of quaternary science reviews representing the proceedings of the xvii inqua held in cairns australia in 2007 this special issue includes papers on a wide variety of quaternary evolutionary palaeoecological and population dynamic subjects including extinct pacific island palm trees beringian beetles scandinavian trees and the effects on human and animal populations of an extraterrestrial impact event in the late glacial of north america

middle to late holocene environmental evolution of the pisa coastal plain tuscany italy and early human settlements a cross disciplinary sedimentological geochemical micropalaeontological and archaeological examination of 12 continuous cores up to 20 m long integrated with stratigraphical geomorphological and historical investigations allows for reliable delineation of the middle late holocene environmental evolution in the pisa old town area with special emphasis on the etruscan age transition depositional facies were identified through integration of sedimentological and micropalaeontological benthic foraminifers ostracods phytoclasts and palynomorphs data while sediment dispersal patterns were reconstructed on the basis of geochemical analyses facies architecture was chronologically constrained by combined archaeological and radiocarbon dating the turnaround from early holocene transgressive conditions to the ensuing middle late holocene phase of sea level highstand is witnessed by a prominent shallowing upward succession of lagoonal paludal and then poorly drained floodplain deposits supplied by two river systems arno and serchio this regressive trend reflecting coastal progradation under nearly stable sea level conditions was interrupted by widespread swamp development close to the iron etruscan age transition the expansion of vast low lying paludal areas across the alluvial plain was mostly induced by the intricate short term evolution of the meandering arno and serchio river systems these changes in the fluvial network which occurred during a period of variable climate conditions strongly influenced the early etruscan culture 7th 5th century bc in terms of human settlement and society behaviour conversely a strong impact of human frequentation on depositional environments is observed at the transition to the roman age from the 1st century bc onwards when the wetlands were drained and the modern alluvial plain started to form the palaeoenvironmental reconstruction fits in with the original geographical descriptions mentioned in strabo s chronicles and provides chronologically constrained data of fluvial evolution from the pisa old town area

abrupt climatic changes during the last glaciation based on pollen analysis of the abric romani catalonia spain the abric romani continental pollen record provides evidence of abrupt climate variations during the last glaciation the pollen record reveals a pattern of high frequency variations similar to that in ice cores as shown by oxygen isotopes or dust content analyses of 14 travertine samples yield coherent u series ages in correct stratigraphic order ranging from 40 000 to 70 000 yr according to changes in the composition and structure of the vegetation five paleoclimatic phases have been differentiated the oldest ranging from 70 200 to 65 500 yr ago records thermophilous taxa which correspond to the last warm events of isotopic stage 5 the next phase from 65 500 to 56 800 yr records a cold humid climate that correlates with isotope stage 4 during the third phase from 56 800 to 49 500 yr relatively warm and cold events alternate the fourth phase from 49 500 to 46 200 yr records a cold dry climate the fifth phase ranging from 46 200 to 40 800 yr records a milder phase that is similar in appearance to the beginning of the holocene

origin and incremental evolution of brittle ductile shear zones in granitic rocks natural examples from the southern abitibi belt canada abstract metre scale shear zones developed in the mooshla granitic pluton exhibit a plethora of internal mesoand microstructures revealing their mode of nucleation growth and termination the subvertical e w brittle ductile shear zones are developed in the most isotropic part of the intrusion and consist of phyllonites characterized by mylonitic fabrics and well developed down dip mineral lineations they are exposed on a single large and flat outcrop perpendicular to the mineral lineation these brittle ductile shear zones are in close spatial association with a fracture system along which they have nucleated and propagated joints fractures and brittle faults contain abundant evidence of ductilely deformed and recrystallized minerals suggesting that they underwent ductile shearing after their formation the deformation was accompanied by the influx of a metasomatic fluid which altered original fe mg bearing minerals and plagioclase into quartz epidote chlorite sericite and carbonate that precipitated in dilatant fractures and narrow breccia zones we recognize two different types of lateral terminations i shear zones that terminate into joints and fractures that are parallel or oblique to the shear direction and ii curved segments of shear zones that connected with neoformed splay fractures at high angle to the shear direction in the latter case sharp bending and severe perturbation of the shear zone orientation occur at the shear zone termination where ductile shearing is transfered into an adjacent shear zone via dilatational fractures this demonstrates that shear zones tended to grow towards each other and coalesce to form a well developed anastomosing network we propose that narrow dilatational fractures and joints acted as paleo weakness planes along which fluid rock interaction and resulting reaction softening occurred the deformation scenario involves episodic fluid drawn into dilatant sites responsible for cyclic fluid pressure fluctuation in the system dilatancy related fracturing and reaction softening lead to deformation under brittle to plastic conditions and to shear strain localization