phases of soil erosion derived colluviation in the loess hills of south germany in south germany soil erosion is as old as farming and dates back to early neolithic times its sedimentary products form thick colluvial and alluvial sediment bodies in all drainage basins numerous local studies exist but the extrapolation of findings from local case studies to a regional scale has been problematic here a graphical approach is used for frequency analysis of existing data a frequency distribution for optical dates on colluvial sediments from the beginning of agriculture until 1200 ad was constructed by 1 representing the optical ages by gaussian distributions and 2 summing all the single curves the resulting graph clearly shows phases of increased colluviation during periods of stronger human impact a first significant increase occurred during the bronze age during the iron age roman period and at around 800 ad distinct maxima appear in the distribution and highest frequencies are present towards the end of the analysed period at around 1100 ad conclusions that can be drawn from such an approach are limited by sampling bias and other factors but for the analysed period and on a regional and long term scale colluviation seems to have been mainly triggered by intensity of land use climatic fluctuations are of only secondary importance rainfall events that were sufficiently erosive to produce colluvial sediments occurred throughout the agricultural periods the limiting factor for colluvium production was sensitivity of the landscape to erosion and this is a result of land use d 2002 elsevier science b v all rights reserved

a flexible approach to assessing synchroneity of past events using bayesian reconstructions of sedimentation history the dating of depths in two or more cores is frequently followed by a study of the synchroneity or otherwise of events reflected in the cores the difficulties most frequently encountered are a determining precisely the depths associated with the events and b determining the ages associated with the depths there has been much progress in recent years in developing tools for the study of uncertainties in establishing chronologies this has not yet been matched by similar progress in modelling event depth relationships this paper proposes a simple and flexible approach showing how uncertain events can be married to uncertain chronologies difficulties in studying event depth age relationships typically involve a confounding of two different problems first what exactly do we mean by an event a point in history a single depth in the core corresponding to a single time or a depth time range sometimes event is in fact a shorthand for a space time process do the data reflect more than one type of event process this can reflect vagueness in definition second what are the sources and implications of the uncertainties here we illustrate the issues involved by examination of several features seen in north european holocene pollen records the alnus rise is regarded as a diachronous early holocene event in contrast the ulmus decline is widely seen as a near synchronous event in the mid holocene the third feature we examine is the interval between the ulmus decline and the first occurrence of cerealia type pollen the evidence for these events lies in cores of lake sediment from which are determined a the proportions of pollen at many depths and b radiocarbon age estimates from usually fewer depths for this illustration we focus on six sites we draw attention to a new and flexible method implemented in the free r software package bchron haslett j parnell a 2008 a simple monotone process with application to radiocarbon dated depth chronologies journal of the royal statistical society series c 57 4 399 418 for the establishment of the uncertainties surrounding the dating of samples in such cores we illustrate its flexibility by assessing the synchroneity of past events

controls on the strength of coupling among climate erosion and deformation in two sided frictional orogenic wedges at steady state 1 many important insights regarding the coupling among climate erosion and tectonics have come from numerical simulations using coupled tectonic and surface process models however analyses to date have left the strength of the coupling between climate and tectonics uncertain and many questions unanswered we present an approximate analytical solution for two sided orogenic wedges obeying a frictional rheology and in a condition of flux steady state that makes explicit the nature and sensitivity of the coupling between climate and deformation we make the simplifying assumption that the wedge grows in a self similar fashion consistent with airy isostasy such that topographic taper is invariant with orogen width tectonic influx rate and climate we illustrate first how and why the form of the erosion rule matters to orogen evolution and then derive a physically based orogen scale erosion rule we show that steady state orogen width crest elevation and crustal thickness are controlled by the ratio of accretionary flux to erosional efficiency to a power dictated by the erosion process remarkably we show that for most combinations of parameters in the erosion law rock uplift rate is more strongly controlled by erosional efficiency than it is by the accretionary flux further assuming frontal accretion with no underplating the spatial distribution of erosional efficiency dictates the relative rock uplift rates on the pro wedge and retro wedge and the time averaged trajectories of rocks through the orogen the restriction to invariant frictional properties is conservative in these respects systems subject to positive feedback between erosion and rheology will exhibit even stronger coupling among climate erosion and deformation than shown here

fundamentals of fission track thermochronology fission track ft analysis has developed into one of the most useful techniques used throughout the geologic community to reconstruct the low temperature thermal history of rocks over geological time the ft method is based on the accumulation of narrow damage trails i e fission tracks in uranium rich mineral grains e g apatite zircon titanite and natural glasses which form as a result of spontaneous nuclear fission decay of 238u in nature price and walker 1963 fleischer et al 1975 the time elapsed since fission tracks began to accumulate is estimated by determining the density of accumulated tracks in a particular material in relation to the uranium content of that material chemical etching can be used to enlarge fission tracks that have formed within a mineral in order to make them readily observable under an ordinary optical microscope price and walker 1962 if a host rock is subjected to elevated temperatures fission tracks that have formed up to that point in time are shortened progressively and eventually erased by the thermal recovery i e annealing of the damage fleischer et al 1975 because thermal diffusion basically governs the annealing process the reduction in ft length is a function of heating time and temperature importantly fission tracks are partially annealed over different temperature intervals within different minerals this characteristic allows for the construction of time temperature paths of many different rock types by a plotting ft and other isotopic ages from different minerals versus their closure temperatures which is applicable in the case of a monotonous cooling history e g wagner et al 1977 zeilter et al 1982 and or by b the inverse modeling of observed ft age and confined track length data e g corrigan 1991 lutz and omar 1991 gallagher 1995 ketcham et al 2000 see also ketcham 2005

superposed and refolded metamorphic isograds and superposed directions of shear during late orogenic extension in the alboran domain southern spain the timing kinematics and mode of exhumation within the alpujarride complex the largest tectonic unit of the alboran domain are controversial alternative tectonic models include synorogenic exhumation during pre miocene crustal thickening intraorogenic exhumation during repeated phases of contraction and extension and late orogenic exhumation during early miocene crustal thinning new structural and petrographic relationships documented in this study support the latter model subhorizontal foliations stretching lineations and recumbent folds are associated with early miocene high temperature decompressional metamorphism and vertical condensation of the metamorphic sequence relict isograds associated with high pressure metamorphism and burial are systematically overprinted by isograds associated with high temperature metamorphism and rapid decompression during the early stages of extensional exhumation and growth of sillimanite ene directed shear d2 overprinted thrusts and foliations associated with crustal thickening d1 during the later stages of extensional exhumation and growth of andalusite from ductile to semibrittle conditions north directed shear d3 produced kilometer scale recumbent folds that refold isograds stretching lineations characterize superposed directions of orogen parallel l2 and later orogen perpendicular l3 shear associated with a rapid temporal transition in the kinematics of extensional exhumation during the final stages of crustal thinning and cooling ductile structures d2 d3 were cut by brittle low angle normal faults d4

lateglacial to holocene pedogenesis and formation of colluvial deposits in a loess landscape of central europe wetterau germany abstract loess areas in central europe have been settled since ancient times and are therefore predestined to archive information about both the paleoenvironment with and without human activities in gentle rolling loess landscapes distinct short and shallow valleys so called dells are prominent landscape elements that act as sediment traps the loess paleosol colluvium lpc sequence of gambach wetterau germany can be regarded as an exceptional sequence for lateglacial holocene pedogenesis and human impact in dry loess landscapes with the lpc sequence of gambach reflects climate controlled pedogenesis from ca 15 ka to 4 7 ka with the formation of a cambisol having some properties related to chernozem soil forming processes during the lateglacial a chernozem is developed in the deposits of the laacher see tephra which still show the influence of periglacial climate in their lowermost part the upper part of these deposits was relocated by colluvial processes at around 6 7 ka chernozem soil forming processes were still ongoing until 4 7 ka when these shifted to luvisol formation which is still active today since 4 7 ka extended land use with indications of agricultural fire use since at least 2 3 ka led to the formation of colluvial deposits combined with a topographic leveling of upland positions on a landscape scale the results of the formative element of humans on loess landscapes from the wetterau can also be taken as representative for around 9400 km2 of dry loess landscapes in central europe

contrasting patterns of hydrological changes in europe in response to holocene climate cooling phases the quantitative reconstruction of climatic parameters from pollen and lake level data obtained at saint jorioz lake annecy eastern france gives evidence for cooler and wetter conditions during the 8 2 ka cold event a comparison of these regional data with other hydrological records reconstructed in europe for the same period suggests as a working hypothesis that mid latitudes between ca 50 and 43 underwent wetter conditions in response to the cooling whereas northern and southern europe were marked by drier climate in the latter case leading to an interruption of the sapropel 1 formation in the mediterranean a similar hydrological tri partition of europe can be observed during other holocene cooling phases associated with north atlantic ird events data indicate that the middle zone characterised by wetter climate conditions could have had a more extended latitudinal amplitude during phases of climate cooling weaker than the 8 2 ka event the differences in expansion of the wet mid european zone depending on holocene climate cooling phases could reflect variations in the strength of the atlantic westerly jet in relation with the thermal gradient between high and low latitudes

ten million year history of a thrust sheet the final deformed state of a fold and thrust belt may be reached by an infinite number of kinematic paths two end member kinematic paths are due to continuous or discontinuous rates of deformation we have used a new magnetostratigraphic section from the spanish pyrenees to calibrate the emplacement history over 10 m y of a major thrust sheet the sierras marginales thrust sheet and the deformation of both its hanging wall and footwall six time windows from before 36 5 ma until after 24 7 ma were recognized on the basis of structural and stratigraphic relationships between syntectonic strata and major structures footwall deformation of the sierras marginales thrust sheet occurred continuously on a detachment within the foreland basin sequence 4 5 km net shortening shortening rates steadily increased from 0 14 to 1 5 mm yr with time although the detachments at the base of the foreland and the detachment at the base of the sierras marginales thrust sheet were active coevally the rate of displacement on the sierras marginales detachment decayed with time and shows considerable variability emplacement of the thrust sheet may be divided into three distinct periods a rapid 13 8 km translation from 37 0 to 36 5 ma 27 6 mm yr a gradual climb of the toe of the thrust sheet up a 4 3 km long ramp across the foreland basin succession from 36 5 to 32 0 ma 0 95 mm yr and a final 8 9 km translation from 32 0 to 29 5 ma 3 56 mm yr internal deformation of the thrust sheet occurred only after it reached its present position at some time before 29 5 ma shortening rates steadily decreased from 0 6 mm yr between 29 5 and 27 8 ma to 0 26 mm yr from 27 8 until after 24 7 ma only 1 km of shortening accumulated during each of the two periods the last shortening localized on the most northerly thrust in the study area folding and subsequent faulting above the detachment beneath the foreland suggest that slip was transmitted to its tip point continuously throughout the deformation in contrast translation followed by internal deformation on the hinterland side of the toe of the sierras marginales thrust sheet indicates a successive deactivation of the southern parts of the detachment with time rate of deformation on both detachments was discontinuous and shows substantial variability about the mean in general the spatial and temporal pattern of deformation was distributed and continuous in detail however shortening was spatially and temporally discontinuous above each detachment and structures related to each one display distinctly different deformational patterns rates and styles

links between orogenic wedge deformation and erosional exhumation evidence from illite age analysis of fault rock and detrital thermochronology of syn tectonic conglomerates in the spanish pyrenees abstract we present new geochronologic data illuminating the tectonic and erosional history of the orogenic wedge exposed in the south central pyrenees spain we interpret illite age analyses from four fault gouges that record thrust belt development and document the importance of out of sequence thrusting fault activity occurs in pulses with slip occurring contemporaneously on multiple faults throughout the wedge new apatite fission track data from syn orogenic sediments of the sis conglomerate body reveal ages of 48 to 42 ma with no consistent variation upsection in strata deposited from 41 to 30 ma we interpret these data as well as thermal modeling of track length distributions to imply rapid cooling in the interior of the pyrenean wedge during the middle eocene the record of fault activity and erosion suggests that orogenic wedges may not evolve in a steady fashion but generally exhibit significant changes in rates of deformation and exhumation the observed correlation in the timing of tectonism and erosional exhumation provides evidence for links between tectonic and surface processes

the brittle plastic transition and the depth of seismic faulting a simple rheological model of shearing of the lithosphere that has gained wide acceptance is a two layer model with an upper brittle zone in which deformation takes place by frictional sliding on discrete fault surfaces and a lower plastic zone in which deformation takes place by bulk plastic flow the two are separated by an abrupt brittle plastic transition which is assumed to be indicated by the lower limit of seismicity experimental studies however as well as the deformation structures of mylonites indicate that a broad transitional field of semi brittle behavior lies between these extremes this is a field of mixed mode deformation with a strength that can be expected to be considerably higher than that predicted from the extrapolation of high temperature flow laws for quartzofeldspathic rocks the semi brittle field lies between t1 the onset of quartz plasticity at about 300 c and t2 feldspar plasticity at about 450 c a model is presented in which the transition t1 does not correspond to a transition to bulk flow but to a change from unstable velocity weakening friction to stable velocity strengthening friction t1 thus marks the depth limit of earthquake nucleation but large earthquakes can propagate to a greater depth t3 t3 t2 which corresponds to the lower limit of dynamic frictional behavior in the semi brittle field and approximately to the peak in strength the zone between t1 and t3 is one of alternating behavior with flow occurring m the interseismic period and with co seismic dynamic slip occurring during large earthquakes this zone is characterized by mylonites interlaced by pseudotachylytes and other signs of dynamic faulting the transition t1 is also marked by a change in the generation mechanism of fault rocks from abrasive wear above which produces cataclastites to adhesive wear below which is proposed as an important generation mechanism of mylonites in the upper part of the semi brittle field

sequential development of selected pyrenean thrust faults new mapping structural analysis and magnetostratigraphy reveal a polyphase deformational history at the leading edge of the spanish pyrenean foreland fold and thrust belt the present structural architecture is the consequence of three discrete periods of deformation map relationships between four syntectonic units and major structures provide tight geometric and age constraints for each deformational period d1 55 to 42 ma d2 30 1 to 28 0 ma d3 27 9 to 25 8 ma most of the shortening in the area accumulated during d2 thrusting at rates which varied from 0 7 mm y 1 to 2 8 mm y 1 along strike from northwest to southeast respectively removal of d2 and d3 displacement on thrust faults restores folds formed during d1 a sequential kinematic history during which an individual structure accommodates shortening by folding tightening of the fold and subsequent truncation by thrust faulting is inferred sequential restoration of three serial cross sections demonstrates that nearly every structure active during d1 was also active during d2 distributed deformation characterizes the temporal and spatial pattern on all time scales from structures active during each individual deformational period to the long term history encompassed by the total deformation

changes in sediment flux and storage within a fluvial system some examples from the rhine catchment the rhine river system can look back on a long history of human impact whereas significant anthropogenic changes to the river channel started only 200 years ago the impacts of land use have been felt for more than 7500 years here we review results from several case studies and show how land use change and climate impacts have transformed the fluvial system we focus on changes in sediment delivery pathways and slope channel coupling and show that these vary in time and depend on the magnitude of a rainfall event these changes must be accounted for when trying to use sediments as archives of land use change and climatic impacts on fluvial systems for example human impact is recorded in slope deposits only as long as rainfall intensity and runoff generation do not exceed the threshold for gullying similarly climatic impacts are only recorded in alluvium when both the landscape is rendered sensitive by human activities e g deforestation and rainfall thresholds for gullying are exceeded copyright 2003 john wiley sons ltd

climatic change and contemporaneous land use phases north and south of the alps 2300 bc to 800 ad fluctuations in the 14c curve and subsequent gaps of archaeological findings at 800 650 and 400 100 bc in western and central europe may indicate major climate driven land abandonment phases to address this hypothesis radiocarbon dated sediments from four lakes in switzerland were studied palynologically pollen analysis indicates contemporaneous phases of forest clearances and of intensified land use at 1450 1250 bc 650 450 bc 50 bc 100 ad and around 700 ad these land use expansions coincided with periods of warm climate as recorded by the alpine dendroclimatic and greenland oxygen isotope records our results suggest that harvest yields would have increased synchronously over wide areas of central and southern europe during periods of warm and dry climate combined interpretation of palaeoecological and archaeological findings suggests that higher food production led to increased human populations positive long term trends in pollen values of cerealia and plantago lanceolata indicate that technical innovations during the bronze and iron age e g metal ploughs scythes hay production fertilising methods gradually increased agricultural productivity the successful adoption of yield increasing advances cannot be explained by climatic determinism alone combined with archaeological evidence our results suggest that despite considerable cycles of spatial and demographic reorganisation repeated land abandonments and expansions as well as large scale migrations and population decreases human societies were able to shift to lower subsistence levels without dramatic ruptures in material culture however our data imply that human societies were not able to compensate rapidly for harvest failures when climate deteriorated agriculture in marginal areas was abandoned and spontaneous reforestations took place on abandoned land south and north of the alps only when the climate changed again to drier and warmer conditions did a new wide spread phase of forest clearances and field extensions occur allowing the reoccupation of previously abandoned areas spatial distribution of cereal cultivation and growth requirements of cerealia species suggest that increases in precipitation were far more decisive in driving crop failures over central and southern europe than temperature decreases

oscillations of the water balance during the holocene in interior central europe features dating and consequences abstract the continental water balance depends on precipitation and evaporation with the latter due to temperature moreover both the components of weather and climate are influenced by the annual seasonality all these factors have changed during the last millennia and periods of significant moisture have alternated with ones of low moisture evidence of these oscillations results from geostratigraphical subdivision of sequences of freshwater lime deposits and from lake level changes of inland lakes but also from many archaeological observations concerning settlement distribution all these observations reflect oscillations that can be correlated through archaeological and other dating alternation of drier and moister periods in the course of the central european holocene can be recognized

are mid latitude slopes sensitive to climatic oscillations implications from an early holocene sequence of slope deposits and buried soils from eastern germany abstract on a straight slope within the lake catchment of kleiner tornowsee brandenburg germany a sequence of slope sediments has been deposited during the late glacial the early holocene and around cal 4 2 ka before today 800 500 and 300 years ago the chronology is based on 21 radiocarbon dates and 11 osl dates and a deposition model including the numerical data as well as stratigraphic information has been calculated with oxcal 4 1 a comparison of the woody taxa of charcoal particles n 566 embedded within the sediments with the known regional vegetation history confirmed the reliability of the dates according to the age volume and distribution the deposition of the early holocene sediments at ca 10 3 kyrs ca 9 5 kyrs and ca 8 2 to 7 7 kyrs before today strongly suggests an influence of known climatic deteriorations phases on geomorphologic processes cold and dry climatic conditions probably promoted wildfires in pinus dominated forests and therefore triggered the observed repeated slope instability in consequence mid latitude slope deposits provide a potential to reconstruct the geomorphological response to climatic events at a high spatial resolution in contrast the recorded mid to late holocene soil erosion phases on the slope have been triggered by land use activities apart from traditional environmental archives slope deposits provide valuable information about the vegetation and climate history

sense of nappe emplacement from quartz c axis fabrics an example from the betic cordilleras spain preferred crystallographic orientation patterns fabrics in zones of ductile deformation beneath nappes are a potentially useful indicator of the sense of nappe translation quartz c axis fabrics from a shear zone beneath the pile of higher betic nappes in the betic cordilleras spain have distinctly asymmetric topologies revealed by constructing a fabric skeleton these skeletons closely resemble those produced by computer simulations of quartz fabric development basedon taylor bishop hill theory the fabric asymmetry indicates a northerly sense of transport for the nappes consistent with field evidence from the same area analyses of both c and a axis fabrics based on asymmetric intensity distributions within the fabric give equivocal results and may reflect the presence of earlier preferred orientation patterns predating nappe emplacement

orogeny and orography the effects of erosion on the structure of mountain belts a numerical model of the coupled processes of tectonic deformation and surface erosion in convergent orogens is developed to investigate the nature of the interaction between these processes crustal deformation is calculated by a two dimensional finite element model of deformation in response to subduction and accretion of continental crust erosion operates on the uplifted surface of this model through fluvial incision which is taken to be proportional to stream power the relative importance of the tectonic and erosion processes is given by a dimensionless erosion number relating convergence velocity rock erodibility and precipitation rate this number determines the time required for a system to reach steady state and the final topographic shape and size of a mountain belt fundamental characteristics of the model orogens include asymmetric topography with shallower slopes facing the subducting plate and an asymmetric pattern of exhumation with the deepest levels of exhumation opposite to subduction these characteristics are modified when the regional climate exhibits a dominant wind direction and orographically enhanced precipitation on one side of the mountain belt the two possible cases are dominant wind in the direction of motion of the subducting plate and dominant wind direction in the opposite direction of the subducting plate velocity models of the former case predict a broad zone of exhumation with maximum exhumation in the orogen interior models of the latter case predict a focused zone of exhumation at the margin of the orogen and at high erosion number a reversal in the topographic asymmetry natural examples of these two cases are presented the southern alps of new zealand exhibits the climate and exhumation asymmetry characteristic of wind in the direction opposite to motion of the subducting plate the asymmetry of topography suggests that erosion is not efficient enough to have reversed the topographic asymmetry the contrasting example of dominant wind in the direction of subduction motion is provided by the olympic mountains of washington state in this case exhumation of deep levels of the cascadia accretionary wedge shows a broad domal pattern consistent with the observed orographic precipitation

inversion of small basins effects on structural variations at the leading edge of the axial zone antiformal stack southern pyrenees spain the southern axial zone of the pyrenees consists of a foreland dipping system of thrusts and backthrusts forming the leading edge of a basement involved antiformal stack several small stephanian permian extensional basins were strongly inverted during the pyrenean cainozoic orogeny and controlled thrust geometry and kinematics causing lateral structural variation palinspastic restoration reveals three main grabens erill castell estac and gramos basins capped by undeformed triassic strata in the lower orri and erta thrust sheets the overlying nogueres thrust sheet partitioned into several slices contains smaller basins northern basins the erill castell half graben with a steeply dipping sedimentary infill was inverted along its border fault and extruded by bedding parallel backthrusts the narrow thick estac basin which was less deformed internally was a heterogeneity causing major lateral variation in the system the gramos basin originally wide and covered by a gentle unconformity angle was also inverted along its border fault but caused less lateral variation in the thrust system the northern basins appear only in the western part of the present day nogueres thrust sheet where minor units are strongly stacked and rotated in the east thrust slices are large and shallow dipping the study case is a good example of complex 3d thrust development influenced by the initial geometry of a heterogeneous basin system

apatite fission track analysis apatite fission track aft analysis has been widely used during the past 30 years to constrain the low temperature thermal histories of many igneous metamorphic and sedimentary rocks in a wide range of geological settings applicable geological settings include orogenic belts rifted margins faults sedimentary basins cratons and mineral deposits the types of geologic problems that can be addressed include the timing and rates of tectonic events sedimentary basin evolution the timing of hydrocarbon generation and ore mineralization the absolute age of volcanic deposits the effects of major climatic changes on the near surface geothermal gradient and long term landscape evolution early work by naeser 1967 and wagner 1968 1969 first established the basic procedures that enabled the fission track dating method to be applied routinely to these geologic problems fleischer et al 1975 summarized the early studies of the broader discipline of nuclear track detection in different solid state materials more recent comprehensive overviews of fission track applications have been provided by naeser and mcculloh 1989 wagner and van den haute 1992 gallagher et al 1998 van den haute and de corte 1998 dumitru 2000 and gleadow et al 2002 etched natural fission tracks in several apatite grains are shown in figure 1 successful aft analysis is limited by the following 1 the availability of apatite from which useful aft data can be obtained often due to a lack of apatite of sufficient grain size and quality within available rock types or alternatively the lack of available rock samples due to minimal outcrop exposure or other reasons 2 economic considerations in terms of the time and money required to obtain sufficient aft data 3 the inherent limitations of aft data to resolve geological thermal history information often related to limited numbers of accumulated spontaneous fission tracks due to

new geophysical constraints on the deep structure of the pyrenees a 2d modeling of geoid quasigeoid data across the pyrenees is consistent with electromagnetic images of the pyrenean lithospheric structure showing a subducted iberian lower crust using new magnetotelluric data acquired through the orogen a 3d electrical conductivity model of the pyrenean lithospheric structure is obtained the most outstanding feature is the presence of a high conductivity zone at lower crustal depths along the orogen in the contact zone between the iberian and european plates the integration of various geophysical parameters suggests that the simplest and most reasonable mechanism to explain the observed data is partial melting of the subducted iberian lower crust

a new structural and kinematic framework for the alboran domain betic rif arc western mediterranean orogenic system the processes that drastically thinned and rapidly exhumed the alboran domain in southern spain are poorly understood geological maps cross sections and a synthesis of previous work in the alpujarride complex provide a new structural framework for the alboran domain with major revision of the previously defined lithotectonic units alboran continental lithosphere was buried and thickened in the paleogene d 1 and subsequently thinned during late orogenic extension in the early miocene regional patterns of stretching lineations and late recumbent folds record important spatiotemporal changes in the kinematics of extension east directed shear d 2 is preserved in deep orogenic levels and thinned the crustal sequence during rapid exhumation and high temperature metamorphism north directed shear d 3 d 4 is preserved in upper orogenic levels and reworked earlier structures during the later stages of exhumation and cooling this large scale switch in the direction of finite stretching resulted from the interaction between components of orogen parallel d 2 and orogen perpendicular d 3 d 4 extension and associated vertical and lateral gradients in strain we provide a novel kinematic model for gravity driven extensional collapse of the alboran domain compatible with both westward motion of the alboran domain relative to the iberian margin and subsequent northward extensional flow and emplacement of alboran lithosphere onto the iberian margin supplementary material a list of sample names coordinates and descriptions plus a google earth kmz file of sample locations is available at https doi org 10 6084 m9 figshare 5508643 a geological sketch map of the sierra de las estancias indicating the trend of stretching lineations in the alpujarride complex and location of major geological boundaries is available at https doi org 10 6084 m9 figshare 5513398

mechanisms of argon retention in clays revealed by laser 40ar 39ar dating a method for dating clays is important for studies of weathering diagenesis hydrocarbon migration and the formation of major metalliferous deposits however many attempts have produced imprecise or inaccurate results data from shales show that contrary to expectations the 40ar 39ar dating technique can be successfully used to determine the diagenetic age of ancient sediments because 39ar losses during irradiation are controlled by release from low retentivity sites in illite equivalent to those that have lost radiogenic 40ar in nature rather than by direct recoil as is generally assumed

colluvium definition differentiation and possible suitability for reconstructing holocene climate data abstract this study examines whether colluvial soils store climatic data and if these data can be used as proxies colluvial soils as the correlated sediments of soil erosion represent a widespread geoarchive these soils store the morphology data of the eroded soils and contain clues as to the processes of the eroded soils formation as well as indications of the pedogenesis which took place after the deposition all of these processes are closely related to climatic factors especially rainfall this study discusses the genesis of young soils in colluvial sediments and shows that typical soil features may be related to climatic factors furthermore the study investigates the genesis of anthropogenic colluvial sediments which must be seen as a syngenetical product of relief field size time of usage pressure of population farming technique sediment erodibility deposition area and climatic factors to this end pedogenic features are separated from the sedimentological features the results show that the reconstruction of all factors which control the genesis of the formation of a colluvium is still not yet possible this is the necessary precondition for colluvial soils to yield proxy climate data or for the data to be correlated with already existing holocene climate archives as the results of our discussion are ambiguous in their interpretation we conclude that colluvial soils which clearly include climatic information cannot be used for the reconstruction of proxy climate data at present

holocene environmental variability in the central ebro basin ne spain from geoarchaeological and pedological records abstract environmental fluctuations during the holocene caused important landscape changes in the central ebro basin which is a very sensitive region due to its semiarid climate lithology and continuous human presence severe erosion processes hinder palaeoenvironmental and archaeological record preservation infills of ephemeral stream valleys in semiarid environments are some of the best contexts for geoarchaeological studies in this paper we analyse the geomorphological processes pedological features and charcoal and pollen content and composition of the sedimentary sequence of la poza valley catchment area with the support of additional information from la bajada valley 14 c dates for 13 charcoal fragments provide the necessary chronological control we describe 5 sedimentary units and a polycyclic sequence of six soils that covers most of the holocene beginning ca 9 5 ky cal bp buried soils help to identify stability periods in the sedimentary sequence while incision stages are detected through erosive contacts and terraced organisation of the sedimentary units charcoal and pollen content and composition as well as the soil development reveal an open forest of junipers and pines for the early holocene in the lower part of the sequence mainly in unit 1 very different from the current deforested landscape also represented in the sequence unit 4 thus la poza record shows the environment was favourable for hunter gatherers from the late mesolithic and for the first neolithic farmers from then on progressive degradation due to a combination of climate changes and increasing human pressure led to the current deforested landscape

geomorphic tectonic control of sediment discharge to the ocean the importance of small mountainous rivers analysis of data from 280 rivers discharging to the ocean indicates that sediment loads yields are a log linear function of basin area and maximum elevation of the river basin other factors controlling sediment discharge e g climate runoff appear to have secondary importance a notable exception is the influence of human activity climate and geology on the rivers draining southern asia and oceania sediment fluxes from small mountainous rivers many of which discharge directly onto active margins e g western south and north america and most high standing oceanic islands have been greatly underestimated in previous global sediment budgets perhaps by as much as a factor of three in contrast sediment fluxes to the ocean from large rivers nearly all of which discharge onto passive margins or marginal seas have been overestimated as some of the sediment load is subaerially sequestered in subsiding deltas before the proliferation of dam construction in the latter half of this century rivers

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

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

correcting temporal frequency distributions for taphonomic bias in this paper we expand upon a prior study surovell t a brantingham p j 2007 a note on the use of temporal frequency distributions in studies of prehistoric demography journal of archaeological science 34 1868 1877 that explored the problem of taphonomic bias taphonomic bias refers to the tendency for younger things to be over represented relative to older things in the archaeological record due to the operation of destructive processes like erosion and weathering using a database of radiocarbon dated volcanic deposits from bryson r u bryson r a ruter a 2006 a calibrated radiocarbon database of late quaternary volcanic eruptions earth discussions 1 123 124 we develop an empirical model of taphonomic bias in contrast to our prior study in which we modeled taphonomic bias as an exponential function wherein the likelihood of site loss remains constant through time we argue that the probability of site destruction actually decreases with site age we further demonstrate how this model can be used to correct temporal frequency distributions and extract demographic histories we illustrate this approach using databases of radiocarbon dates from rockshelter and open air sites in the bighorn basin wyoming usa and mammoths and humans in siberia russia

high resolution record of northern hemisphere climate extending into the last interglacial period high resolution record of northern hemisphere climate extending into the last interglacial period

age and source of colluvial sediments at vaihingen enz germany abstract colluvial sediments accumulated on the lower slopes of a ridge as a result of past and present soil erosion were dated by optical 14 c and archaeological methods this allowed us to reconstruct the depositional history of the colluvium and also to identify temporary sedimentary sinks in its transportational pathway a cascade model of colluvium formation is developed colluvial sediments resulting from early soil erosion in the neolithic to iron age periods were mainly deposited on the upper slopes significant deposition on the lower slope occurred for the first time during the iron age and roman period since then deposition rates have increased because of more intensive land use

the late thermal history of the ronda area southern spain abstract the betic rif belt in the western mediterranean experienced a pre alpine history and was later extensively reworked by major alpine tectonics there is abundant data showing that the betic chain suffered very high cooling rates during its alpine history constrained mainly by geochronology using various isotopic systems and by palaeontological age determinations in the westernmost part of the chain the high closure temperature isotopic systems recorded miocene high grade metamorphism in the country rocks in order to constrain the later stages of cooling fission track analysis has been applied to both zircon and apatite the results point to extremely high rates of cooling 400 c ma between 21 and 19 ma rates slowed to 100 c ma for the time period 19 to about 12 ma the fission track analysis also confirms the existence of an extensional tectonic stage between 19 and 17 ma

the sis palaeovalley a record of proximal fluvial sedimentation and drainage basin development in response to pyrenean mountain building the sis conglomerate body represents the middle eocene to oligocene transfer zone trunk palaeovalley fill of the sis fluvial system a drainage system established within the pyrenees during late palaeocene times the spatial stability of the fluvial transfer zone active for at least 38 my and hence the longevity of its aggradational palaeovalley component 19 5 my was controlled by its location between long lived pre existing structures coarse grained fluvial facies dominate the palaeovalley fill with alluvial fan facies shed from its defining marginal structures the detailed sedimentology of very proximal fluvial facies deposited within the dominantly erosional realm of an active mountain belt has rarely been documented before because of their poor preservation potential the sis conglomerate body contains a robust internal stratigraphy with stratigraphic units defined by distinct bounding surfaces across which there are pronounced changes in facies and provenance these mark the reorganization of the headward portions of the sis fluvial system during the evolution of the pyrenean axial zone antiformal stack major changes in discharge resulted demonstrating the highly variable nature of even mountain belt scale fluvial systems when viewed on timescales of several to tens of millions of years provenance details indicate that initial unroofing of hercynian granitoids situated within the pyrenean axial zone occurred around 54 5 ma early ypresian immediately before the first significant exhumation event within the drainage basin of the sis fluvial system this is earlier than previously constrained by apatite fission track studies rock uplift accelerated in the lutetian and bartonian with the initial aggradation of the palaeovalley fill the cajigar and cornudella formations and sis one and two members this became marked in the priabonian sis three and four members with significant activity on local structures including the morreres backthrust an increase in basement derived clasts and a headwater decapitation event also indicate pronounced axial zone antiformal stack development at this time axial zone development intensified further in the oligocene with the deposition of the collegats formation and the switch in the main depositional loci of the system from the tremp graus thrust sheet top basin to the ebro basin to the south

thrust tectonics in the south central pyrenees abstract surface structural data and published stratigraphies are combined to construct two balanced and restored sections through the nogueras zone of the south central pyrenees the allochthonous nogueras zone units are interpreted as the foreland dipping margin of a major antiformal stack in the palaeozoic rocks of the pyrenean axial zone their structural evolution is summarized in a hangingwall sequence diagram this reinterpretation of the nogueras zone is incorporated into a new n s balanced and restored section from the centre of the pyrenean axial zone to the ebro basin a classical rocky mountains piggy back thrust model is employed and the resulting section is a significant departure from those previously published it is argued that gravity gliding has never been an important mechanism in the alpine pyrenees section restoration casts doubt on the correlation of the surface expression of the north pyrenean fault and the seismically detected moho step beneath it

on folding and shear zone development a mesoscale structural study on the transition between two different tectonic styles abstract an example of coeval development of ductile shear zones and folds in schistose terrains is documented by detailed mapping and structural analysis folds and shear zones were formed under retrogressive conditions after the peak of the regional hercynian metamorphism and both affect a previous regional schistosity a gradual change in structural style on a regional scale is evidenced by the disappearance in higher grade domains of late folds and the preponderance of shear zones geometrical analysis reveals that the bulk structural pattern is compatible with a non coaxial strain history structural variation reflects a gradual change in mechanical behaviour of schists which show a marked variation in crystallinity at the time of deformation

thermochronology of a convergent orogen constraints on the timing of thrust faulting and subsequent exhumation of the maladeta pluton in the central pyrenean axial zone abstract the pyrenees mountains of spain and france are a collisional orogen cored by a south vergent antiformal stack of paleozoic basement thrust sheets the axial zone thrusting accommodated shortening due to convergence between iberia and europe granitic plutons intruded during the hercynian orogeny form an important component of the basement units thermochronology of granodioritic samples collected from a vertical age elevation profile from the south central maladeta pluton provide new constraints on the timing of thrust faulting and rock exhumation of the pyrenean orogen the maladeta massif lies within the orri thrust sheet presently occupying the immediate footwall of the gavarnie thrust a major axial zone alpine age thrust fault new biotite and k feldspar 40ar 39ar and apatite u th he ahe data combined with previous apatite fission track aft thermochronology and structural studies of the maladeta pluton constrain the thermal evolution of this massif biotite weighted mean plateau and k feldspar maximum 40ar 39ar ages from the highest elevations of the maladeta pluton 2850 m are 280 ma close to the age of intrusion and are interpreted to date the timing of rapid cooling in the hercynian subsequently the maladeta massif remained close to the surface as indicated by the presence of unconformable triassic continental sediments k feldspar 40ar 39ar multiple diffusion domain thermal models from two samples at lower elevations 1780 m and 1400 m indicate heating initiated at 65 ma reaching maximum temperatures of 270 to 280 c these data are interpreted to record thrust burial of the maladeta pluton to depths of 6 10 km in the footwall of the gavarnie thrust burial and heating were followed by a period of relatively rapid cooling beginning at 50 ma recorded in three k feldspar thermal models from samples at different elevations 2850 m 1780 m and 1400 m aft thermal models in conjunction with the aft and apatite ahe age elevation profile interpretation reveal a lower temperature portion of the thermal history these data indicate the onset of rapid cooling that began at 30 35 ma slowed dramatically at 25 30 ma and continued at a reduced rate until 15 ma finally aft thermal models from the lowest elevation samples record rapid cooling in the late miocene pliocene most likely due to re excavation of the southern flank of the pyrenean orogen following burial by syn tectonic conglomerates the integrated thermochronologic data set from the age elevation profile within the maladeta pluton illustrates the potential for obtaining age constraints related to processes operating within the interior portions of convergent orogenic systems e g the onset and or duration of thrust fault activity that are otherwise unobtainable

archaeopedology and chronostratigraphy of colluvial deposits as a proxy for regional land use history baar southwest germany abstract soils are the basis of our food production supplying plants with nutrients and water farming leaves traces in the soil because cultivation can cause soil erosion one result is the formation of colluvial deposits which can be used as geoarchives of past human impacts on their terrestrial environment the present study combines pedological and archaeological knowledge with chronostratigraphic analyses to infer deposition phases of colluvial material thereby allowing the reconstruction of past land use and settlement activities in the baar region sw germany local colluvial signals are interpreted as a regional proxy for increased soil erosion and colluviation on the baar seven main deposition phases of colluvial material can be detected by 28 luminescence dates and 41 radiocarbon ages distributed through 26 soil profiles our results indicate increased colluviation in the younger neolithic 3800 bce the early to middle bronze age 1550 bce the iron age 500 bce the roman empire 100 ce and from the high middle ages onwards 1200 ce 1300 ce 1600 ce these dates and record of colluviation complement archaeological knowledge of the fundamental impact of human activities on the landscape due to sedentism and agriculture early anthropogenic hypothesis our study shows that most periods of intensified colluvial deposition often but not always date to times with colder more humid climatic periods the spatial and temporal correlation of main depositional phases with archaeological finds points to land use as the determining factor of colluvial deposition at least since roman times

s c mylonites two types of foliations are commonly developed in mylonites and mylonitic rocks a s surfaces related to the accumulation of finite strain and b c surfaces related to displacement discontinuities or zones of relatively high shear strain there are two types of s c mylonites type i s c mylonites described by berthe et al typically occur in deformed granitoids they involve narrow zones of intense shear strain which cut across mylonitic foliation type ii s c mylonites described here have widespread occurrence in quartz mica rocks involved in zones of intense non coaxial laminar flow the c surfaces are defined by trails of mica fish formed as the result of microscopic displacement discontinuities or zones of very high shear strain the s surfaces are defined by oblique foliations in the adjacent quartz aggregates formed as the result of dynamic recrystallization which periodically resets the finite strain clock these oblique foliations are characterized by grain elongations alignments of segments of the grain boundary enveloping surfaces and by trails of grains with similar c axis orientations examples of this aspect of foliation development in mylonitic rocks are so widespread that we suggest the creation of a broad class of s c tectonites and a deviation from the general tradition of purely geometric analysis of foliation and time relationships kinematic indicators such as those discussed here allow the recognition of kilometre scale zones of intense non coaxial laminar flow in crustal rocks and unambiguous determination of the sense of shear

the variscan geology of the pyrenees abstract the main outlines of the geology of the variscan part of the pyrenees are discussed rocks involved in this cycle are high grade basement gneisses palaeozoic sediments and their metamorphic equivalents late intrusive granodiorites and early pre variscan granites the main features of the stratigraphy of the palaeozoic are given structures fall into two domains a low grade suprastructure essentially with steep folds and cleavages and a high grade infrastructure with dominantly low dipping foliations an important phase of early pre cleavage folding occurs in low grade rocks mainly along the southern border of the axial zone in high grade rocks most structures and the metamorphism postdate the main cleavage phase in low grade rocks the influence of the alpine orogeny on the variscan structures consists mainly of faults steep reverse faults in the northern and south directed thrusts in the southern part of the pyrenees metamorphism took place under high geothermal gradients and low pressures as indicated by the abundant occurrence of andalusite and cordierite

brittle frictional mountain building 3 low grade metamorphism an active fold and thrust belt in unchanging tectonic and climatic conditions exhibits a dynamic steady state with the flux of rocks accreted at the toe balanced by the flux of rocks eroded off the top rocks entering the toe are buried and heated before they are uplifted and eroded this results in a characteristic map pattern of low grade metamorphism on the surface metamorphic isograds are generally parallel to the regional strike of a fold and thrust belt with the grade increasing progressively from unmetamorphosed and zeolite facies near the deformation front up to greenschist facies in the highest mountains such a pattern is observed in the active fold and thrust belt of taiwan this paper examines the origin of this low grade syntectonic metamorphism using a previously developed mechanical and thermal model of a steady state fold and thrust belt as a basis to model the metamorphism we develop a petrogenetic grid for rocks of basaltic composition considering phases within the chemical system cao mgo al2o3 sio2 h2o equilibria diagnostic of stable low grade mineral assemblages are mapped onto a cross section of the taiwan fold and thrust belt using the calculated fluid pressure and temperature distributions within the wedge the variation of metamorphic grade along the surface is predicted by assuming that there is no retrograde metamorphism the most important mechanical factor controlling the degree of metamorphism in an active fold and thrust belt is the amount of frictional heating both on the basal decollement fault and within the deforming brittle wedge frictional heating raises temperatures in the deepest portions of the taiwan fold and thrust belt by 200 c to 250 c the resulting high temperatures in excess of 400 c are responsible for the extensive greenschist facies metamorphism the amount of heating is well constrained by the observed heat flow anomaly geochronological data and the critical wedge taper the best fitting coefficient of basal friction in taiwan is b 0 5 0 2 underplating of footwall rocks by the assimilation of duplexes along the decollement fault is not considered to be a significant process in taiwan because of the observed balance between the accretionary influx at the toe and the erosive efflux off the top in other fold and thrust belts however underplating can significantly increase the outcrop width of higher metamorphic grades on the surface by increasing the flux of rocks through the higher fluid pressure and temperature regions within the wedge

erosion and exhumation in accretionary orogens experimental and geological approaches 1 this study examines the role of erosion on exhumation and deformation history of accretionary orogens through experimental and geological methods fault propagation kinematics and exhumation rates in an eroded thrust wedge are analyzed through scaled sandbox simulations by testing different parameters friction rheologic layering and sediment input output ratio a model coulomb wedge is submitted to erosion under flux steady state conditions that is the volume of eroded material remains equal to the volume of newly accreted material maintaining a constant surface slope during shortening results show that the way of exhumation depends on the internal dynamics of thrust wedges and conversely on how this dynamics is modified by erosion in the eroded thrust wedges the diversity of exhumation patterns is controlled by the mode of fault propagation depending on the basal friction high or low the vertical component of exhumation is generally higher for the wedges with high basal friction than for low friction wedges the uplift of material occurs along a cluster of subvertical thrusts in the middle part of the eroded thrust wedge with low basal friction the material is exhumed along a series of inclined 20 50 thrusts in the rear of the high friction wedge the zone of maximum exhumation is generally localized in the middle part of the thrust wedge and migrates toward the backstop with continued shortening the vertical exhumation rate increases with time and the material accreted later is rapidly transferred to the main exhumation zone compared to the material accreted during the early stages the exhumation occurs at rates 2 times faster in the wedges with half the thickness than in full thickness wedges the total quantity of eroded material at the end of convergence constitutes 36 50 of initial model area for the thrust wedges with low basal friction and 20 40 for the high basal friction wedges the extent of basal underplating increases with total shortening the area of basal underplated material constitutes up to 30 and 40 of the eroded thrust wedge area for the models with low and high basal friction respectively presence of decollements in the accreted series allows underplating of thrust units developing an anticlinal stack whose growth and location is favored by erosion our results are compared to different present day active and ancient convergent orogens himalaya taiwan southern alps of new zealand and cascadia orogen allowing the different specific exhumation processes to be characterized

historical soil erosion by water in germany scales and archives chronology research perspectives abstract the published record of historical soil erosion by water in germany as deduced from dated slope deposits n 306 alluvial sediments n 120 and lake sediments is summarized in this paper the number of sediments investigated reflects the state of knowledge chronology of historical soil erosion and to a certain degree the intensity of the human impact on german landscapes during the holocene even though few data of calculated historical soil erosion intensities exist an estimation of historical soil erosion in germany combining the available data has been calculated soil erosion in germany occurred first locally during the early holocene probably triggered by climatic variability from the neolithic onward the record reflects the human impact according to agricultural land use the observed variability indicates phases of weaker and regained intensity of agricultural land use in germany few records characterise the early and middle bronze age ca 2000 1600 bc and the migration period and the early medieval times ca 400 1000 ad surprisingly for the roman emperor times ca 1 400 ad a decreasing number of soil sediments is recorded even when the data from southern germany is examined separately phases characterised by an increase in soil erosion were the late bronze age and pre roman iron age ca 1600 bc 1 ad the high and late medieval times ca 1000 1350 ad and the modern times ca 1500 ad until today some extraordinary heavy precipitation events late 18th early 19th first half of 14th century pre roman iron age topped the even high soil erosion intensities research gaps as well as potential for future research as derived from the available data are outlined

quartz fabric evolution within the adra nappe betic cordilleras spain abstract the adra nappe alpujarride complex betic cordilleras is an imbricated thrust sheet of metamorphic rocks at the regional scale changes in c axis fabrics of deformed quartzites in the nappe are fully consistent with the strain path inferred from the microstructures in the upper part of each imbricate where the reference frame s 2 l 2 is weakly deformed by open f 3 folds quartz c axis fabrics are characterized by symmetrical patterns of small circle girdles around z increasing strain towards the basal thrust faults is marked by new quartz fabrics developed during a pervasive d 3 mylonitization these fabrics correspond to asymmetrical single girdles or asymmetrical type ii cross girdles these changes in quartz fabric can be correlated with the progressive replacement of an initial coaxial flow d 2 by a non coaxial flow d 3 near the thrust fault as a result of the movement of the adra nappe

the temporal and spatial quantification of holocene sediment dynamics in a meso scale catchment in northern bavaria germany the aufsess river catchment 97 km2 in northern bavaria germany is studied to establish a holocene sediment budget and to investigate the sediment dynamics since the early times of farming in the third millennium bce the temporal characterization of the sediment dynamics is based on an intensive dating program with 73 osl and 14 14c ages to estimate soil erosion and deposition colluvial and alluvial archives are investigated in the field by piling and trenching supported by laboratory analyses the sediment budget shows that 58 of these sediments are stored as colluvium in on and foot slope positions 9 are stored as alluvium in the floodplains and 33 are exported from the aufsess river catchment colluviation starts in the end neolithic c 3100 bce while first indicators of soil erosion derived alluviation is recorded c 2 3 ka later the pattern of sedimentation rates also displays differences between the colluvial and alluvial system with a distinct increase in the middle ages c 1000 c

stratigraphy and age of colluvial deposits indicating late holocene soil erosion in northeastern germany abstract in the focus of this study are the sedimentary characteristics chronology magnitude and causes of past soil erosion dynamics of an agriculturally intensively used glacial lowland landscape from the mesoscale quillow river catchment sedimentary sections bearing colluvial sediments from different landforms were analysed to explore their geoarchive potential and to establish a local chronology of late holocene soil erosion sections from footslopes contain a rather simple stratigraphy with one topping colluvial horizon of up to 1 m thickness burying a palaeosol in contrast glacial kettle holes preserve more complex sequences partly having several colluvial layers with intercalating palaeosols the most complex stratigraphy is associated with a kettle hole being the ultimate sediment trap for a dendritic gully system forming a 4 m thick sequence of alternating peat and colluvial layers thirty osl ages and 13 radiocarbon ages are used to reconstruct phases of soil erosion potentially human induced soil erosion which is corroborated by local archaeological and palynological data can be traced back to the last c 4000 years the oldest colluvial deposits date back to the late bronze age most datings however cluster within the last 600 years with a peak in the last 200 years ascribing the main phase of local soil erosion to the recent past thus although numerous archaeological finds are detected in the catchment since the neolithic considerable agricultural soil erosion does not occur before the last millennium a compilation of osl chronologies based on colluvial sediments from other regions in central europe shows a more complex erosion history there with a pronounced two or three phased distribution of ages primarily dating into the last c 4000 5000 years this study underlines that in northeastern central europe human impact on landscapes was effective apparently at a later stage as compared to some adjacent regions

the importance of apatite composition and single grain ages when interpreting fission track data from plutonic rocks a case study from the coast ranges british columbia abstract fission track results determined from granitic rocks exposed within the coast ranges of british columbia indicate that significant variations in apatite chemistry may occur in small plutonic rock samples to test ages determined earlier by parrish using the population method of fission track dating new apparent apatite ages were completed using the external detector method so that single grain ages could be generated in most cases the new apatite ages were similar to the earlier ones within 2 however in many cases it was found that individual samples contained significant variations in single grain apatite ages microprobe analyses showed the spread in ages were directly related to variations in apatite chemistry such that chlorine rich apatites retained older ages than fluorine rich grains examination of the single grain age data suggested that the spread in single grain ages provided information which constrained the thermal history of the sample and that distributions of single grain ages reflected the temperatures at which they resided during cooling these results suggest that it is important to generate more than a few single grain fission track ages when dating apatite from granitic rocks since variations in the chlorine concentration in apatite grains may exist in kg sized granitic rock samples therefore it is no longer a valid assumption that each apatite grain separated from a small granite sample will have a similar chlorine concentration and in future apatite fission track studies of granitic terrains it is important to recognize that the apatite composition might be heterogeneous when interpreting results

pedosedimentary and geoarcheological archives from clay dominated sinkhole infillings in middle franconia germany abstract sinkholes in the karstified middle keuper gypsum of middle franconia germany reveal numerous archeological findings and contain unique pedosedimentary records of landscape development and human environment interaction during the holocene mudstone derived high clay contents result in a unique set of sedimentary and pedogenic properties of these archives in that all units exhibit vertic properties since the horizons have a polygenic history detailed field and micromorphological observations together with laboratory analyses grain size color iron pedochemistry are the basis for a classification of the pedosediments 14c dating provides a chronological framework for geomorphological stability phases and thus identified soil forming processes the first anthropogenic colluvial sediments of the studied archive date to the early bronze age and accumulated in an initial karst depression water saturation caused iron reduction of these early infillings in the pedosediments above oxidation and iron release are largely related to changes in the parent material here the soil material contains coarse silt indicating an admixture of nearby periglacial slope deposits furthermore fossil root traces point to a longer time with stable conditions which we interpret as absence of humans or at least an extended period of fallow land the superimposed sediments from the urnfield period are more inhomogeneous and consist of material from the eroded agricultural soils of the surrounding the characteristics of these pedosediments point to intensified human land use pedogenic processes such as iron release reduction of iron swelling shrinking and short distance translocation of clay intensively overprinted all soil sediments in this context micromorphology proved to be an essential tool for the characterization of polygenesis in terms of soil forming as well as redepositional processes that lead to the formation of these complex archives the present study reflects a multi methodological approach to a rather disregarded type of polygenic terrestrial records it constitutes an example for the investigation of clayey pedosediments in karstic environments under moderate climate in the frame of a prehistoric geoarcheological setting

the human impact in geomorphology 50 years of change abstract concern with the human impact in geomorphology has a long history what is new is that since 1969 a number of developments have taken place that have led to an increasing realisation of its importance these developments are in four main areas i intellectual and policy related ii technological developments that alter geomorphological processes iii demographic trends and iv the proliferation of techniques for the study of landform and process change there has been a realisation of the role of humans in landscape transformation in ancient times the human impact has developed through time but particularly notable are the potential early effects of fire extinctions and deforestation on geomorphological processes the spread of european agriculture particularly in the nineteenth century transformed erosion and sedimentation rates in many parts of the world notwithstanding the importance of some of these changes in prehistoric and historic times recent researches have demonstrated that humans have become an increasingly important agent of geomorphological change during the period of the great acceleration of the past five or six decades the interest in global warming that has developed since the early 1980s has created considerable interest in its consequences for a range of geomorphological phenomena it is also becoming apparent that anthropogenic geomorphological change is having an impact on the earth system as a whole finally geomorphologists have taken an increasing interest in how they can make an impact in the field of landscape conservation

continental collision crustal thinning and nappe forming during the pre miocene evolution of the alpujarride complex alboran domain betics the tectono metamorphic evolution of the alpujarride complex within the internal zones of the gibraltar arc indicates that the alboran crustal domain underwent several contractional and extensional events the superposition of structures and the metamorphic evolution observed in the alpujarride complex and in particular in the adra unit suggest that these events are as follows a the first thickening event d1 results from continental subduction and is evidenced by the presence of pre s2 high pressure mineral relicts b the thinning and associated vertical shortening event d2 is indicated by an almost isothermal decompression during which the s2 main foliation developed c kilometric scale n vergent recumbent folds of the condensed metamorphic sequences and thrust and nappe forming in the alpujarride complex suggest that a second thickening event d3 took place d the second thinning event d4 which affects the whole alboran domain is evidenced by extensional fault systems resulting in the opening of the alboran sea the oldest synrift deposits are of the late oligocene and early miocene suggesting that d1 to d3 events are pre miocene and e from the late tortonian to the pliocene the extensional systems were folded due to a continuous n s to nw se compression

a new middle to late eocene continental chronostratigraphy from ne spain abstract the calibration of the european paleogene mammal biochronology with the international reference geochronological scale is unconstrained due to the lack of direct marine continental correlations and insufficient robust magnetostratigraphic data for mammal fossil bearing sequences the currently accepted european continental biochronology argues for a correlation of the paleogene mp14 to mp16 mammal reference levels with the bartonian stage and of the mp17 to mp20 levels with the priabonian however new magnetostratigraphic data of the continental sediments of the south central pyrenees substantially challenge this chronology our new results from the la pobla de segur basin and sierra de sis have been integrated into the framework of previous marine continental stratigraphic correlations and magnetostratigraphic data of the south central pyrenees in this new chronology mp14 and mp15 reference levels correspond to the lutetian whereas mp16 and early mp17 correlate with the early bartonian this calibration represents a significant revision of currently accepted marine continental correlations in europe but is not in conflict with the available biostratigraphic data of the south pyrenean ebro foreland basin and other western european reference basins

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

synchronous holocene climatic oscillations recorded on the swiss plateau and at timberline in the alps eight synchronous pre roman cold phases were found at 9600 9200 8600 8150 7550 6900 6600 6200 5350 4900 4600 4400 3500 3200 and 2600 2350 radiocarbon years bp by reconstructing past climate at two sites on the swiss plateau and at timberline in the alps the cooling events during the early and mid holocene represent temperature values similar to today and apparently the onset of cooling events represents a deviation from today s mean annual temperature of about 1 c and is triggered at a 1000 year periodicity at wallisellen langachermoos 440 m a former oligotrophic lake near zurich the correlation between sum mertime lake levels and the seed production of the amphi atlantic aquatic plantnajas flexilis was used to reconstruct lake levels over a 3000 year period during the first part of the holocene at lake seedorf on the western swiss plateau 609 m the sedimentological palynological and macrofossil record revealed fluctuations of lake levels for the complete holocene from lago basso in the

quantifying multiple electromagnetic properties in emi surveys a case study of hydromorphic soils in a volcanic context the lac du puy france we used two different loop loop electromagnetic induction emi devices to determine the 3d geometry and morphology of the pedo sedimentary filling and underlying basaltic bedrock of a former wetland in a volcanic soil area the lac du puy depression auvergne france electrical conductivity or resistivity is usually sufficient for environmental and soil science applications but the local volcanic context of the survey area results in high values of magnetic susceptibility and possible electrical polarization effects therefore we investigated the roles of the four properties electrical conductivity magnetic susceptibility magnetic viscosity and dielectric permittivity we created models using these four properties for the two coil configurations of each device in order to assess the degree to which each of the properties contributed to the recorded electromagnetic signal the results show that electrical conductivity controls the quadrature component of the secondary field response but that it can be affected by high values of magnetic viscosity while magnetic susceptibility controls the in phase component moreover the low frequencies imply a limited contribution of dielectric permittivity to the in phase component except in the cases of higher permittivity or frequency values or greater inter coil separation based on these observations we propose a way to map the apparent properties from field measurements we then carried out a 1d inversion first by considering the electrical conductivity alone and secondly by taking all the electromagnetic properties into account the results show that there is a marked contrast in the complex magnetic susceptibility between the sedimentary in fill and the border of the lac de puy depression stronger than for the electrical conductivity and that permittivity is unlikely to have a significant influence the shape and nature of the sedimentary in fill was thus considerably refined by the second inversion results based on the three other properties these data combined with litho stratigraphic observations from a previous study allowed the lateral continuity and geometry of the in fill to be assessed across the whole basin results are also consistent with previous interpretations of the depression as a pseudo sinkhole a relatively common morphology in volcanic plateaus analysis of the magnetic properties also made it possible to characterize the spatial variation of some key features related to hydromorphic processes such as clayey granularity and the development of iron oxides hydroxides this opens up the possibility for using new methods for rapid spatial and pedological characterization of hydromorphic soils and palaeosoils

internal structure of the adra nappe alpujarride complex betics spain abstract the adra nappe belongs to the alpujarride complex of the betic chain southern spain this metamorphic nappe is of great interest to the understanding of the tectonic evolution of the betic chain since two episodes of thrusting inside the same alpujarride nappe can be differentiated these two episodes have been produced in different physical p t conditions and with different directions of thrusting the first one towards the northeast and the second towards the north northwest furthermore the plate tectonics reconstructions weijermars 1987 dewey 1988 and geodynamic models andrieux et al 1989 platt and vissers 1989 published so far for the betic chain have not considered these two episodes of thrusting recognized in all nappes belonging to the alpujarride complex of the betic chain in the area studied to the south of sierra nevada the adra nappe shows a marked structural variation from an upper folded zone consisting of low grade metamorphic rocks to a mylonitic zone located in lower levels and characterized by medium to high grade metamorphic materials it has been observed that the emplacement of the adra nappe has involved two episodes the first episode produces the formation of mylonitic rocks with a stretching lineation n45 e the second one gives rise to gouges and fault breccias and is bound to movements of the upper block in n10 w direction from a regional point of view in this sector the adra nappe occupies the upper tectonic position of the alpujarride complex the extensional regime of the adra nappe appears to be intimately associated with the n s convergence of africa and iberia from oligocene times whereas the ne thrusting would reflect a previous strike slip motion parallel to the trend of the betic chain probably in an oblique convergence setting these points concerning the two directions of movement must be considered for geological palaeoreconstructions of the western mediterranean area

a synchronized dating of three greenland ice cores throughout the holocene as part of the effort to create the new greenland ice core chronology 2005 gicc05 a synchronized stratigraphical timescale for the holocene parts of the dye 3 grip and ngrip ice cores is made by using volcanic reference horizons in electri cal conductivity measurements to match the cores the main annual layer counting is carried out on the most suited records only exploit ing that the three ice cores have been drilled at locations with different climatic con ditions and differences in ice flow however supplemental counting on data from all cores has been performed between each set of reference horizons in order to verify the valid ity of the match after the verification the main dating is transferred to all records us ing the volcanic reference horizons as tie points an assessment of the mean annual layer thickness in each core section confirms that the new synchronized dating is consistent for all three cores the data used for the main annual layer counting of the past 7900 years are the dye 3 grip and ngrip stable isotope records as the high accumulation rate at the dye 3 drill site makes the seasonal cycle in the dye 3 stable isotopes very resistant to firn diffusion an effort has been made to extend the dye 3 holocene record the new syn chronized dating relies heavily on this record of 75 000 stable isotope samples the dat ing of the early holocene consists of an already established part of gicc05 for grip and ngrip which has now been transferred to the dye 3 core gicc05 dates the younger dryas termination as defined from deuterium excess to 11 703 b2k 130 years earlier than the previous grip dating

crustal scale strike slip deformation in hokkaido northern japan abstract field surveys in hokkaido reveal that the entire tectonic belt in northern japan was a right lateral shear zone from eocene to middle miocene time this zone of deformation can be followed northwards in sakhalin for more than 2000 km and formed at the same time as the opening of the japan sea a thrusting component during the strike slip deformation and later deformation stages led to the uplift of the deep parts of the shear zone exposing a complete section through the upper crust the stress field inferred from the analysis of fault sets is consistent with the non coaxial deformation observed in the deeper ductile parts of the shear zone there is a transition from west to east across the width of the belt 100 km from en echelon folds thrusts and nappes at upper structural levels through the brittle ductile transition with an incipient vertical schistosity into ductile deformation with a vertical foliation and metamorphic recrystallization in the amphibolite facies deep parts of the crust granulites were uplifted and retrogressed during the strike slip movement fault set analysis together with data concerning the direction and sense of nappe emplacement imply that thrusting west of the ductile deformation zone occurred during the strike slip deformation minor flat lying structures coexist with vertical pure strike slip structures this study and previous ones reveal a crustal scale half flower structure with superficial thrusting associated with a deep narrow ductile zone with a high gradient of deformation and temperature

the history of soil erosion and fluvial deposits in small catchments of central europe deciphering the long term interaction between humans and the environment a review abstract during the last few decades many case studies focused on the dynamics of fluvial systems in response to hillslope erosion land use impact and climate changes this paper will review the current state of knowledge of the dynamics of past soil erosion and gullying in small catchments

catena linking of landscape geochemical processes and reconstruction of pedosedimentogenesis a case study of defensive constructions of the mid 17th century south russia abstract the catena concept along with previously proposed meanings of this term has recently acquired a soil evolutionary content the prospects of wider special and chronological study of dated pedotopocatenas include the possibility of a more detailed analysis of the mutual dependence of soil geomorphological relationships through distinguishing relatively homogeneous climatic stages of pedogenesis and denudation with this purpose the present study comprised earthen defensive constructions which within the rampart ditch system combine erosive trans accumulative catenas and accumulators of pedolithosediments the goal was to develop a system of the most information rich pedogenetic indicators to reconstruct the dynamics of erosion accumulative processes on the basis of dated earthen defensive constructions of a historical period using the example of a frontier rampart within a ditch from the mid 17th century soil samples were collected within the limits of the erosion and trans accumulative catenas as well as in the closing alignment of the ditch over the vertical profile in eight strata of pedosediments of up to 1 m high the granulometric composition concentration of macroelements and trace elements 25 metals and oxides in soils and in particles with sizes 0 01 mm in size the content of organic carbon and its qualitative composition the sum of the elements accumulated in the soil p ca k mg mn cu as well as the geochemical ratios which reflect the processes of leaching can serve as palaeogeographic tracers of the climatic variability at the level of intra secular changes under forest steppe conditions the history of the formation of pedosediments over 3 5 centuries in the forest steppe zone of eastern europe comprises two wet periods 1890 1935 1976 2013 when the average annual rates of pedosedimentogenesis were similar 2 80 2 85 mm yr 1 and two periods of geomorphological lull and a xeromorphic climatic condition span 1821 1890 and 1666 1741 these periods correspond to diminution of the average rate of accumulation of sediments down to 2 47 mm yr 1 the results of the present study suggest the need for purposeful research and wide inclusion of dated sites of the anthropogenic relief formation with flow geochemical series over the topographic gradient into studies of soil geomorphologic interrelations and calibration of mathematic models of natural processes using on site data

holocene relief and soil changes in loess covered areas of south western germany the pedosedimentary archives of bretten bauerbach kraichgau based on infrared stimulated luminescence irsl dating of loess borne sediments a chronometry of holocene landscape evolution is established for a representative study site in the early settled kraichgau area in south western germany the results show that the gently rolling relief is due essentially to soil erosion and colluvial deposition triggered by humans cultivating the loess soils since the onset of agriculture in the neolithic period levelling of relief is accompanied by alterations in soil type patterns from haplic luvisols before the impact of humans over variably truncated luvisols with bt horizons prevailing at the slope surfaces in the middle ages to calcaric regosols characterizing both sites of erosion and accumulation since then the tremendous changes show that the effects of human activities have been recorded over thousands of years indicating an early anthropocene in a geomorphological and pedological sense most landscapes are probably more modified by humans than thought at first sight as the results show this recognition requires considering that current geomorphological and soil forming processes might work at different frequencies or magnitudes e g by changes of internal system thresholds such as increased erodibility following the complete erosion of a more resistant bt horizon and or in a different direction e g accumulation instead of erosion or sediment transport due to slope angles decreased by former deposition of colluvium than they would in the absence of a human controlled pre history

luminescence dating of hillslope deposits a review abstract luminescence dating determines the last exposure to light of quartz and feldspar mineral grains and thus the time a sediment was laid down prerequisite is that the sediment grains were sufficiently exposed to light prior to deposition for eolian deposits this seems a fair assumption although exceptions may well exist for other depositional environments light exposure prior to burial is often restricted in duration intensity and spectral composition and may result in an age overestimation recent developments now allow dating of sediments that were exposed to only little light prior to deposition the main developments are single aliquot techniques and statistical tests that allow extraction of valid age estimates even from deposits in which bleached and unbleached grains are mixed these developments in combination with the fact that the great majority of sediments near the earth s surface are not of eolian origin have resulted in the large interest in the luminescence dating of non eolian deposits here we review possibilities and challenges of luminescence dating of colluvial deposits we summarize techniques for the detection and handling of insufficiently bleached sediments a common condition in colluvial deposits we give an overview how luminescence dating has been applied on hillslope sediments for reconstructing landscape response to climate change to analyze past fault activity and unravel human induced soil erosion we discuss sampling strategies and give guidelines as to which techniques are best suited to establish luminescence chronologies for colluvium

stratal extension in thrust footwalls makran accretionary prism implications for thrust tectonics small scale stratal extension is commonly associated with thrust faults in the makran accretionary prism of southwest pakistan low angle normal faults dipping in the direction of transport relative to the thrust are common in gouge zones and duplexes and may also cut the footwall and hanging wall where they cause stratal extension these faults are probably riedel shears we have studied a broad zone of more complex extensional deformation beneath one bedding parallel thrust the zone disrupts earlier compressional structures and affects a significant volume of the footwall normal faults initiating in a rearward sequence branch off the thrust and cut down into the footwall merging at a lower stratigraphic level part of the thrust displacement was thereby transfe red to that level and fragments of the footwall were detached and transferred southward beneath the hanging wall the latter remained undeformed and accommodation structures are confined to the footwall these effects may have been caused by variations in sliding resistance along the fault if a thrust transfers part or all of its displacement down section along normal faults in this way before eventually cutting back up toward the surface it will detach a rootless fragment of footwall rocks from a position forward of the initial ramp through that horizon this process can be referred to as footwall plucking it can explain rootless basement slices along thrusts for example and it has important implications for section restoration techniques and the interpretation of thrust belts

syntectonic emplacement of the maladeta granite pyrenees deduced from relationships between hercynian deformation and contact metamorphism the relationships between hercynian deformation and contact metamorphism in the aureole of the aneto unit a constituent pluton of the maladeta granite complex spanish pyrenees provide new data relevant to the controversy between the syn and post tectonic models of emplacement for the pyrenean granites the deformation in the aneto aureole is related to two superimposed hercynian episodes the first was a top to the sw thrusting which induced sw verging recumbent folds the second which was essentially compressive in the aneto area is represented by e w trending subvertical cleavage and folds with subhorizontal axes this second episode can be assigned to the d2 main hercynian tectonic event of the pyrenees the contact metamorphic assemblages grew during the d2 event and were deformed by it close to the contact the conclusion that the pluton was emplaced during d2 is strengthened by the structural and kinematic similarities between the magmatic deformation in the southern rim of the pluton and the d2 deformation in the country rocks this syntectonic timing is supported by new geochronological data that conflict with an existing rb sr post tectonic permian whole rock age for the maladeta granite more generally in accordance with some very recent structural and u pb zircon studies our results contradict the geodynamical models of the pyrenees which relate the granite intrusions to a late extensional event

improved measurement of fission track annealing in apatite using c axis projection apatite fission track length data are used extensively for thermal history inversion however several studies have documented instances of poor reproducibility of length data we address this problem by using c axis projection to normalize track lengths for crystallographic angle in the extensive laboratory annealing data set acquired by barbarand et al 2003a 2003b a new simplification reduces the c axis projection model from six to four fitted parameters normalizing for track angle using c axis projection improves every aspect of length measurement reproducibility examined it accelerates convergence of mean length in single analyses increases consistency among replicate measurements by a single analyst enhances consistency of measurements of the same mounts by different analysts and improves the match between analyses conducted with and without cf irradiation c axis projection is also shown to enhance the thermal sensitivity of length data based on these results we assert that c axis projection is a good means of compensating for observer bias although it does not overcome differences caused by experimental error

a revision of the eurasian african plate boundary in the western mediterranean the current picture of the plate configuration in the western mediterranean suggests that africa and europe are separated by a transcurrent fault striking east west through the strait of gibraltar and the alboran sea such a fault has been generally assumed because the azores transform fault approaches the horseshoe seamounts north of madeira and therefore could possibly extend through the strait of gibraltar however detailed geological studies in the arc of gibraltar and the alboran sea reveal no major east west fault transecting the crust there this finding is used here to revise the boundary between the african and eurasian plates it is suggested that the northern boundary of the african plate in the western mediterranean is formed by the hayes atlas fault instead of the azores transform

thrust tectonics in the north pyrenees abstract balanced and restored cross sections through the central and eastern pyrenees constructed using both surface and borehole data demonstrate the presence of c 18km of shortening above a flat lying n directed alpine decollement surface hangingwall diagrams show how the north pyrenean satellite massifs are culminations within this thrust system pre thrusting structures such as subhorizontal stretching lineations in the north pyrenean fault zone became rotated above these culminations as the north pyrenean fault was cut by alpine thrusts stratigraphic evidence demonstrates that n directed thrust movements occurred between mid eocene and oligocene time and this is similar to the age of major s directed thrust movements on the south side of the axial zone the n directed thrust system probably originated as a series of backthrusts to the dominant s directed structures

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

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

holocene river activity analysing 14c dated fluvial and colluvial sediments from germany records of fluvial dynamics in response to long term changes of climate and land use impacts are rare therefore cumulative probability functions cpfs of 401 14c ages originating from german rivers and hillslopes were compiled to reconstruct phases of increased geomorphic activity and stability during the holocene an improved analytical method is suggested to normalise cpfs and eliminated the effects of wiggles of the calibration curve and the young age bias nine periods of activity are identified peaking at 7050 6250 5525 3690 2250 1350 820 325 bc and since 875 ad and are compared with climatic palaeohydrological and human impact proxy data until 2250 bc events of geomorphic activity are mainly coupled to wetter and or cooler climatic phases due to growing population and intensive agricultural activities during the bronze age the increased geomorphologic activity between 1300 and 820 bc cannot unequivocally be related to climate since 875 ad the growing population density is considered as the major external forcing differential geomorphic activity of hillslopes and floodplains suggest that the hillslope channel coupling during the holocene is mainly controlled by human impact with a strong increased coupling after 1500 bc

fabric asymmetry and shear sense in movement zones asymmetry between lattice preferred orientation and shape fabrics is commonly observed in microstructural studies of many deformed mineral aggregates e g ice carbonate rocks peridotites and quartzites theoretical predictions are limited by the nature of the models available and more can be gained by discussion of the mechanisms which give rise to such asymmetry in specific natural and experimental situations