the mesozoic and tertiary basins of the bohemian massif and their evolution abstract the bohemian massif is a major positive element within the structural framework of the alpine carpathian foreland its basement became consolidated during the variscan orogeny crustal thicknesses range between 32 5 km and 40 km during the late carboniferous and early permian the bohemian massif became dissected by a conjugate system of wrench faults which controlled the accumulation of a continental coal bearing series late permian red beds were deposited on intramontane topographic depressions in triassic to mid jurassic times the bohemian massif formed a high from which clastics were shed into adjacent basins during the late jurassic and late cretaceous it became transected by nw se trending sedimentary basins the sub hercynian and laramide phases of foreland compression resulted in deformation and uplift of the bohemian massif the eger graben a 350 km long volcanotectonic zone cutting across the bohemian massif in an ene wsw direction came into evidence during the oligocene and is at present inactive the crust of the bohemian massif forms the autochthonous substratum of the outer carpathians which are paralleled by the neogene carpathian foredeep the neogene intramontane neo autochthonous vienna basin is superimposed on the alpine carpathian nappe systems and developed under a tensional setting

dynamic recrystallization mechanisms and their transition in the daling thrust dt zone darjeeling sikkim himalaya abstract the daling thrust dt delineates a zone of intense shear localization in the lesser himalayan sequence lhs of the darjeeling sikkim himalaya from microstructural studies of deformed quartzite samples we show a transition in the dynamic recrystallization mechanism with increasing distance from the dt dominated by grain boundary bulging blg recrystallization closest to the dt and progressively replaced by sub grain rotation sgr recrystallization away from the thrust the transition is marked by a characteristic variation in the fractal dimension d of grain boundaries estimated from the area perimeter method for the blg regime d 1 046 which decreases significantly to a value as low as 1 025 for the sgr regime using the available thermal data for blg and sgr recrystallization we infer increasing deformation temperatures away from the dt in the hanging wall based on the quartz piezometer our estimates reveal strong variations in the flow stress 59 00 mpa to 16 00 mpa over a distance of 1 2 km from the dt deformation mechanism maps constructed for different temperatures indicate that the strain rates 10 12 s 1 to 10 14 s 1 comply with the geologically possible range finally we present a mechanical model to provide a possible explanation for the cause of stress intensification along the dt

crustal evolution of the ktb drill site from oldest relics to the late hercynian granites the crustal unit penetrated during the german continental deep drilling program ktb the zone of erbendorf vohenstrauss zev comprises an association of metabasites and paragneisses and orthogneisses that underwent high and medium pressure metamorphic cycles during the early palaeozoic in this summary of the structural petrological geochemical and geochronological information from borehole and surface rocks we show that geological models proposed prior to drilling have had to be significantly modified features of the zev such as the dominant nw se trending structures devonian 370 ma medium pressure amphibolite facies metamorphism 0 6 0 8 gpa 720 c and earlier eclogite stage are directly comparable with those of the nearby bohemicum unit in western bohemia intervening units in contrast exhibit ne sw trending structures and carboniferous 315 325 ma low pressure metamorphism all units are cut by predominantly posttectonic granites mostly 320 ma earlier models to explain this contrast by means of a nappe emplacement of the zev in the narrow time interval between the younger regional metamorphism and granite intrusion could not be substantiated because contrary to predictions the same rock association was present in the whole of the drilled 9 1 km and therefore no nappe boundary was drilled instead it is interpreted that shallow crustal levels reached by the zev subsequent to the devonian event shielded most of it from the effects of the carboniferous metamorphism a lack of expected thermal and baric gradients within the drilled metamorphic pile is a result of repeated stacking of an original 3 km depth section in mesozoic times an important result of the geological investigations of the ktb project is the recognition that the present day geometry of the zev is a result of cold shallow level thin skinned tectonics that in the absence of the view into the third dimension offered by the drill hole could not have been accurately predicted from the fossil high grade assemblages and structures seen at the surface

onset of recent rapid sea level rise in the western atlantic ocean a high resolution record of sea level change spanning the past 1000 years is derived from foraminiferal and chronological analyses of a 2 m thick salt marsh peat sequence at chezzetcook nova scotia canada former mean tide level positions are reconstructed with a precision of 0 055 m using a transfer function derived from distributions of modern salt marsh foraminifera our age model for the core section older than 300 years is based on 19 ams 14c ages and takes into account the individual probability distributions of calibrated radiocarbon ages the past 300 years is dated by pollen and the isotopes 206pb 207pb 210pb 137cs and 241am between ad 1000 and ad 1800 relative sea level rose at a mean rate of 17 cm per century apparent pre industrial rises of sea level dated at ad 1500 1550 and ad 1700 1800 cannot be clearly distinguished when radiocarbon age errors are taken into account furthermore they may be an artefact of fluctuations in atmospheric 14c production in the 19th century sea level rose at a mean rate of 1 6 mm yr between ad 1900 and ad 1920 sea level rise accelerated to the modern mean rate of 3 2 mm yr this acceleration corresponds in time with global temperature rise and may therefore be associated with recent global warming 2005 elsevier ltd all rights reserved

quartz microstructures developed during non steady state plastic flow at rapidly decaying stress and strain rate abstract synseismic loading to very high stresses 0 5 gpa and subsequent creep during stress relaxation in the uppermost plastosphere at temperatures of ca 300 350 c near the lower tip of an inferred once seismically active crustal scale fault was proposed based on peculiar microstructures identified in rocks exposed over 100 km 2 in the sesia zone european western alps here we discuss the conspicuous and highly heterogeneous microstructural record of quartz in disseminated small scale shear zones sub basal deformation lamellae and arrays of elongate subgrains on the tem scale indicate an early stage of glide controlled deformation at high stresses distributed brittle failure is indicated by healed microcracks very fine grained recrystallised aggregates with a pronounced crystallographic preferred orientation reflect intense plastic flow by dislocation creep locally a fine grained foam microstructure indicates a final stage of static grain growth at low differential stress for the previously inferred peak stresses of about 0 5 gpa and given temperatures initial strain rates on the order of 10 10 s 1 are predicted by available flow laws for dislocation creep of quartz we emphasise the importance of short term non steady state deformation in the uppermost plastosphere underlying seismically active upper crust the related heterogeneous record of quartz is governed by the local stress history at constant temperature

scale considerations in using diatoms as indicators of sea level change lessons from alaska this paper assesses variations in quantitative reconstructions of late holocene relative sea level rsl change arising from using modern diatom datasets from different spatial scales applied to case studies from alaska we investigate the implications of model choice in transfer functions using local sub regional and regional scale modern training sets and produce recommendations on the creation and selection of modern datasets for reconstructing rsl change over holocene timescales in tidal marsh environments comparable with those in alaska we show that regional modern training sets perform best in terms of providing fossil samples with good modern analogues and in producing reconstructions that most closely match observations where these are available local training sets are frequently insufficient to provide fossil samples with good modern analogues and may over estimate the precision of rsl reconstructions this is particularly apparent when reconstructing rsl change for periods beyond the last century for reconstructing rsl change we recommend using regional modern training sets enhanced by local samples

brittle deformation events at the western border of the bohemian massif germany investigations of brittle deformation structures present within the crystalline rocks of the bavarian oberpfalz reveal a complex late to post variscan crustal evolution upper carboniferous mainly westphalian granites were emplaced into semibrittle to brittle rocks of the zev zone of erbendorf vohenstraus and the egz erbendorf greenschist unit respectively from both the alignment of the granites and the direction of granite related tension gashes a north east south west extension must be assumed for the period of magmatic activities apart from the granite intrusions rapid crustal uplift about 1 5 km my led to an increase in the geothermal gradient from 40 c km late variscan post granitic the increased geothermal gradient persisted during the succeeding reverse faulting which results from late carboniferous probably stephanian east west and northeast south west compression although not evidenced directly in the area considered strike slip faults seem to have played an important part during the late variscan crustal evolution particularly in the early permian the strike slip events indicate further crustal shortening and indentation under north south compression a similar indentation was present in cretaceous time after a weak phase of early cretaceous reverse faulting which results from north south compression strike slip faults formed under north west south east and north south compression all these faults in particular the strike slip faults seem to be related to the cretaceous and lowermost tertiary convergence of the alpine carpathian orogeny a late stage of crustal extension characterized by a radial stress tensor 2 3 is indicated through high angle normal faults which probably formed during the subsidence of the adjacent neogene eger graben

on the common solar signal in different cosmogenic isotope data sets 1 in this article we aim to determine frequency ranges and intervals of time in which the solar signal dominates in different cosmogenic isotope data from a 14c based reconstruction of cosmic ray intensity over the last millennia we computed expected 10be variations in two antarctic sites dom fuji and south pole and two greenland sites dye 3 and gisp 2 and compared them with the actually measured 10be abundance at the sites by applying different methods of analysis such as bivariate correlation conventional fft coherence and wavelet coherence we found the following 1 the modeled series on the basis of 14c data are in good agreement with the measured 10be data sets on different timescales and at different locations confirming the existence of a common solar signal in both isotope data 2 the 10be data are driven by the solar signal on timescales from about 100 years up to 1000 years or even to multimillennial scales at the longer scales paleomagnetism plays an increasingly important role 3 the local climate dominates the 10be data mostly on short 100 years timescales but the solar signal becomes important even at short scales during periods of grand minima of solar activity 4 there is an indication of a possible systematic uncertainty in the early holocene likely due to a not perfectly stable thermohaline circulation which requires additional studies we have shown that both 14c and 10be based records are consistent with each other over a wide range of timescales and time intervals they form a robust basis for quantitative reconstructions of solar activity variations in the past

contemporary foraminiferal distributions of a mangrove environment great barrier reef coastline australia implications for sea level reconstructions abstract contemporary foraminiferal samples and associated environmental information were collected from cocoa creek a mesotidal fringing mangrove environment on the great barrier reef gbr coastline australia to elucidate the relationship of the foraminiferal assemblages with elevation and environment there is a strong and highly significant relationship between elevation and the foraminiferal assemblages supporting the intertidal vertical zonation concept which suggests that the distribution of foraminifera in the intertidal zone is usually a direct function of elevation with the most important controlling factors being the duration and frequency of subaerial exposure multivariate analyses separate the intertidal foraminiferal assemblages into three elevational zones with zone i the highest and zone iii the lowest zones i and ii are dominated by agglutinated species trochammina inflata and miliammina fusca respectively and zone iii is dominated by calcareous species notably ammonia tepida and elphidium discoidale multiloculum these assemblage zones are similar to those found in both tropical and temperate intertidal environments a predictive transfer function has been developed to allow reconstruction of former sea levels for tropical environments based upon the relationship between foraminiferal assemblage and elevation results suggest that a precision of 0 07 m should be attainable superior to most similar studies from temperate mid latitude environments our work has produced the first foraminifera based transfer function for environmental interpretations for tropical australia and allows the potential development of a new generation of high resolution sea level reconstructions for the post glacial sequences of the gbr shelf

surface distributions of salt marsh foraminifera from connecticut usa modern analogues for high resolution sea level studies abstract salt marsh foraminifera are routinely used as sea level indicators since their vertical distribution is closely linked with elevation relative to the tidal frame the precise nature of these relationships is variable in time and space and the accuracy of sea level reconstructions depends upon the selection of appropriate modern analogues that reliably reflect past fauna environment associations the marshes of connecticut usa are sites of ongoing research seeking to produce high resolution records of sea level change yet little published data regarding their modern foraminiferal distributions exist this paper presents new surface foraminiferal data from three connecticut salt marshes and evaluates their suitability as modern analogues for past sea level changes the results indicate that significant intra and inter site variability between these marshes and those of neighbouring states exists as a consequence of this the extrapolation of fauna environment relationships developed from marshes with different hydrographic physiographic vegetative or climatic characteristics may produce erroneous reconstructions even when adjusted for variations in tidal range these errors are potentially greatest if single indicator species are used since the relative abundance of individual taxa does not vary consistently with elevation even in high marsh environments from the same site whilst cluster analysis demonstrates that foraminiferal assemblages from connecticut are vertically zoned with respect to mean high water mhw the composition elevation and height range of these zones is variable between sites this spatial heterogeneity results in reconstructions of relatively low and variable precision that restricts their utility in high resolution sea level research new studies seeking to distil decimetre scale changes in relative sea level will need to employ quantitative methods capable of combining multi site information to develop fauna environment relationships that capture this spatial variability reconstructions will be most precise when employing local foraminiferal distributions but may require the collection of additional modern analogue samples from other regions when the extant foraminiferal population of a site differs in composition from its sub fossil counterpart

beryllium 10 transport to antarctica results from seasonally resolved observations and modeling 1 cosmogenic 10be measured in polar ice cores has important application in the reconstruction of past solar activity however the processes controlling its atmospheric transport and deposition to the ice sheets are not fully understood here we use the seasonal changes in 10be concentrations in a 10 year monthly resolved ice core record from the law dome site east antarctica in conjunction with echam5 ham general circulation model gcm simulations of 10be and 7be deposition as tools to examine this problem maximum 10be concentrations are observed in the ice core during the austral late summer to early autumn summer autumn while minimum concentrations are observed during the austral winter the gcm simulations corroborated by earlier observations of 10be 7be ratios in antarctica from the georg von neumayer air sampling station suggest that the 10be concentration maximum is linked to direct input of stratospheric 10be from the antarctic stratosphere to the lower levels of the antarctic troposphere during the austral summer autumn this result contrasts with the modeled transport of 10be to greenland where the seasonal maximum in stratospheric input is seen in the late winter to spring synchronous with the timing of the seasonal maximum in midlatitude stratosphere to troposphere exchange our results suggest that a different combination of processes is responsible for the transport of 10be to the antarctic and greenland ice sheets

reconstruction of the last deglaciation deconvolved records of δ18o profiles micropaleontological variations and accelerator mass spectrometric14c dating bioturbation acts as a low pass filter in displacing and reducing the amplitudes of stratigraphic signals this often leads to a loss of high frequency events in the stratigraphic record in addition when considering an isotopic signal 18o 14c measured in stratigraphic carriers such as foraminifera bioturbation and carrier abundance changes can create artifacts which may be falsely interpreted as leads or lags in the paleoclimatic record

orientation and nature of active crustal stresses determined by electromagnetic measurements in the patagonian segment of the south america plate based on electromagnetic measurements we determined the current stress directions in the uppermost continental crust of patagonia between the active plate margin of the chilean pacific coast and the argentinean passive atlantic margin regional variations of the observed stress pattern are giving details onto the acting tectonic processes we distinguish five regional stress domains with different prevailing horizontal stress directions sh 1 southern coastal cordillera and longitudinal valley sh ssw nne 2 chiloe island sh sw ne 3 northern patagonian andes sh wsw ene 4 argentinean pampa and atlantic margin sh wnw ese and 5 southern patagonian andes sh wnw ese these stress regimes can be related to the geometry of the subducting nazca and antarctic plates to the transform fault between the south america and scotia plates and to passive margin processes along the atlantic coast absolute plate motion and rapid relative plate convergence control the subduction geometry and therefore the stress directions along the convergent margin of the south america plate and the structural style within and landward of the magmatic arc the knowledge of current local stress directions permits the characterisation of potential fault kinematics by in situ measuring of electromagnetic emissions from rocks we determined the maximum horizontal stress orientation in the uppermost crust using a new geophysical tool our investigations on the orientation of the stress regimes also allow conclusions about the causative forces of either tectonic or gravitational origin in this part of the south america plate

sheared bedding parallel quartz vein as an indicator of deformation processes abstract monomineralic veins are well known as good recording of filling and precipitation processes however they are also able to register the action of deformation in rocks we used monomineralic quartz veins from quadrilaterro ferrifero brazil to represent how the deformation actuated during the transformation of different structures they were analyzed using a combination of a u stage and ebsd two main types of quartz aggregates are distinguished single crystals with subgrain development and strain free grains of quartz we interpret the microstructures and textures as the result of a combination of concurrent crystal plasticity microfracturing solution transfer and recrystallization the single quartz grains were deformed by dislocation glide however as the c axis orientation of the grain was not favorable for further glide on basal planes the deformation was accommodated by microfracturing new grains were formed along the deformed zones with crystallographic orientations suitable for gliding on basal planes as the deformation proceeded the new grains continue to develop until the vein was completely recrystallized into an aggregate of granular grains

recognising subtidal foraminiferal assemblages implications for quantitative sea level reconstructions using a foraminifera based transfer function microfossil based transfer function models are increasingly used to provide decimeter scale sea level change reconstructions in this paper i demonstrate that in the tropical location of northern australia problems arise in selecting the appropriate elevation range for the modern training set used to calibrate fossil calcareous foraminiferal assemblages most calcareous foraminiferal species found in cores occur in both modern intertidal and shallow subtidal environments a lack of independent measures to indicate whether fossil assemblages come from intertidal environments forces use of a training set that includes intertidal and subtidal environments this results in decreased precision compared to using a training set solely from intertidal environments the widely used method of assessing model fit to fossil assemblages modern analogue technique often fails to discriminate between acceptable and unacceptable reconstructions it is important to investigate a number of different measures including modern analogue technique canonical correspondence analysis and changing bootstrapped sample specific transfer function errors to fully understand the level of similarity between modern and fossil foraminiferal samples to judge the reliability of transfer function predicted sea level reconstructions copyright 2008 john wiley sons ltd

reassessing transfer function performance in sea level reconstruction based on benthic salt marsh foraminifera from the atlantic coast of ne north america abstract the need to increase the number and distribution of sea level records spanning the last few hundred years has led to particular interest in developing high precision geologically based sea level reconstructions that capture decimetre and multi decadal scale changes transfer functions for tide level are statistical tools that quantify the vertical relationship between inter tidal microfossils and elevation within the tidal frame and their use in sea level reconstruction is growing in popularity whilst a range of sampling strategies dataset qualities and underlying statistical models have been used in transfer function development all variants share the common requirement of accurately extracting precise species elevation relationships from surface data and reliably applying these to fossil assemblages to infer past conditions we present surface foraminiferal data from six transects sampled at three sites spanning a large latitudinal range extending from newfoundland canada to north carolina usa these data demonstrate that significant spatial differences exist within the high marsh foraminiferal assemblages commonly used to reconstruct past relative sea level rsl we standardise these data to account for inter site differences in tidal range using several variants of the standardised water level index swli of horton et al 1999b and show that the best performance is achieved by using the highest occurrence of foraminifera as the upper tidal datum level the standardised surface foraminiferal data are used to develop a suite of foraminiferal transfer functions for tide level which are then applied to fossil assemblages from two sediment cores to reconstruct palaeomarsh surface elevation we highlight the manner in which species elevation relationships are extracted and modified during transfer function development and the impacts that choices in dataset composition and transfer function type have on the resulting reconstructions our results graphically illustrate the importance of these choices and the impacts of temporal and spatial variability in foraminiferal distributions none of which are adequately represented or discernible from the standard summary statistics of performance that commonly accompany transfer function reconstructions we conclude that a more explicit treatment of the transfer function development process is required to support the growing body of precise rsl reconstructions that are now appearing in the literature to that end we make the following four recommendations for a framework to assist in transfer function development that will allow better record inter comparison and minimise the potential for producing precise but ultimately inaccurate reconstructions 1 sampling for surface data should focus on capturing complete species response curves rather than simply compiling modern analogues for fossil material 2 the similarity between the surface assemblages used to produce transfer functions and the fossil assemblages to which they are applied should be better quantified using a range of statistical approaches and must accompany any reconstruction 3 where modern analogues are lacking in local surface assemblages data from additional sites should be added with selection based on fulfilling the requirements of the previous two recommendations the manner in which individual species optima are combined to produce a composite optimum and the extent to which this provides a reasonable representation of the surface data should also be documented 4 the application of wa pls component 2 and higher cannot be justified solely on the grounds of increased performance measures e g r2jack and rmsep and if applied the pattern of optima updates should be used to highlight species that may distort reconstructions

c slip in quartz from subsolidus deformed granite abstract the slip behaviour of quartz from a granite and granitic veins during subsolidus high temperature conditions 700 800 c of deformation is studied by lattice preferred orientation lpo and microstructural techniques lpos with a point maximum of c axes parallel to the shear direction which is close to the stretching lineation are presented and interpreted with the aid of light and electron microscopy in terms of c as the dominant slip direction during plastic deformation microscopy of such samples reveals the presence of 0001 tilt boundaries and free 0001 burgers vector dislocations in edge orientations a change in lpo in a decreasing temperature environment from c axes parallel to the shear direction to c axes normal to the shear direction documents a fabric transition from the rare c slip to the more common a slip fabric it is concluded that conditions of high temperature and partial pressure of water are required to initiate dominant c slip during deformation at geological strain rates

variability of the rebound hardness as a proxy for detecting the levels of continuity and isotropy in archaeological quartz abstract the equotip hardness tester is applied to different types of quartz and other lithic raw materials in order to determine if variations in the rebound hardness measured by this device may serve as a proxy for detecting the levels of continuity and isotropy of toolstones continuity the amount of cracks and other internal defects and isotropy the measure of the directional properties of a raw material are known to have important effects on the level of consistency and predictability of fractures which in turn is traditionally considered a main factor for defining the flaking quality of a given raw material the results demonstrate the existence of differences among the raw materials analysed in both the average value and the variability of the rebound hardness while cryptocrystalline samples show the most homogeneous results quartz and metamorphic rocks display a comparatively higher variance in the specific case of quartz such variability seems to be mainly caused by the presence of internal planes and discontinuities while anisotropy although also active had played a comparatively modest role the results achieved by the equotip hardness tester suggest that this device could be successfully used for a basic or preliminary estimating of some of the physical and mechanical properties of stone raw materials therefore it is a potential index test for complementing other more accurate laboratory methods

testing models of mid to late holocene sea level change north queensland australia understanding the nature of global ice equivalent eustatic sea level changes during the mid to late holocene is important to our understanding of how ice sheets will respond to future climate change this study re analyses the indicative meaning and age control of existing relative sea level rsl data from cleveland bay north queensland australia and presents new rsl data from a foraminifera based transfer function as a preliminary test of global geophysical models in this region during the mid to late holocene the foraminifera based transfer function produces reliable rsl estimates consistent through the mid to late holocene at different locations in cleveland bay analysis of the combined rsl database reveals that rsl rose above present between 8 and 6 2 ka cal bp with the peak of the sea level highstand c 2 8 m above present at c 5 ka cal bp remaining relatively stable above 1 5 m from 6 2 until at least 2 3 ka cal bp falling to present in the last millennia this long period of sea level above present in the mid to late holocene suggests a gradual rather than abrupt end to global ice melt which must have continued into the late holocene this new analysis also shows no evidence for episodic fluctuations within the highstand although they cannot be entirely ruled out by this study this study demonstrates that more sea level data needs to be collected from locations uncontaminated by glacio isostasy hydro isostasy and tectonic effects in order to better constrain the late holocene melt histories of the large polar ice sheets

microfacies characteristics of a tropical mangrove fringed shoreline cleveland bay queensland australia sedimentary and taphonomic controls on mangrove facies development mangrove ecosystems strongly influence the sedimentology and geomorphology of contemporary intertidal environments and are known to have occupied similar ecological niches at least as far back as the early cenozoic given this it is remarkable how few records of mangrove occurrence have been reported in the geologic record here a microfacies approach is adopted to examine the characteristics of a contemporary mangrove colonized intertidal succession along an active prograding shoreline in north queensland australia and compared with a proximal mid late holocene preserved intertidal succession this enables a comparison of microfacies development and preservation potential in like for like depositional environments over short temporal and spatial scales in the contemporary intertidal system active shoreline progradation has produced a highly gradational shallowing upward succession mid to low intertidal substrates characterized by an abundant and diverse bioclast especially molluscan fauna and a rich calcareous foraminiferal assemblage are overlain by organic rich upper intertidal mangrove facies characterized by abundant organic material especially wood and bark fragments and a distinct fauna of agglutinated foraminifera the major sedimentary effects of mangrove progradation are to introduce substantial amounts of organic matter into the substrate effectively overprinting the mudflat facies to mix and re texture due to root network development and infaunal bioturbation the sediment substrate and to modify the depth ranges over which infaunal molluscs and foraminifera occur variations in the relative abundance of constituents permit however the clear delineation of mangrove and intertidal mudflat facies whilst an essentially similar facies succession is identifiable in the sub recent many of the diagnostic facies constituents are either not preserved or are present in far lower abundances than in the modern in particular the inferred mangrove units contain far less organic material most wood and root material is absent are essentially devoid of bioclastic material and contain a depauperate agglutinated foraminiferal fauna the primary drivers of this are 1 loss of calcareous foraminifera and bioclasts due to carbonate dissolution 2 loss of agglutinated foraminifera due primarily to biological fiddler crab test degradation and mineralization of their organic binding agents and 3 aerobic and anaerobic degradation of organic material consequently actual criteria for identifying the presence of a former mangrove in this succession are limited such poor preservation even within sub recent mangrove deposits suggest that the longer term preservation potential of key diagnostic criteria is likely to be extremely poor within similar terrigenoclastic dominated organically enriched successions thus whilst mangroves significantly modify and re texture intertidal substrates use may often need to be made of sparsely preserved faunal or floral remains or traces interpreted in the context of the broader intertidal depositional succession to infer the presence of mangrove colonized substrates in the rock record

distribution of modern salt marsh foraminifera in the albemarle pamlico estuarine system of north carolina usa implications for sea level research abstract we described the distributions of foraminifera from ten physiographically distinct salt marshes in the albemarle pamlico estuarine system north carolina using 193 surface samples we defined elevation dependent ecological zones at individual sites using cluster analysis and detrended correspondence analysis additionally seven principal biozones of salt marsh foraminifera were identified that have distinctive spatial distributions reflecting a pattern of salinity regimes caused by the current configuration of barrier island inlets high salinity sites along the southern outer banks are associated with sub tidal calcareous assemblages low marshes dominated by miliammina fusca and high marsh environments defined by haplophragmoides wilberti trochammina inflata and arenoparrella mexicana in contrast lower salinity marshes have ammobaculites spp in sub tidal settings miliammina fusca dominated low marshes and high marsh settings characterized by jadammina macrescens spatial variation of foraminiferal populations and the potential for biozones to migrate in response to changing inlet configuration and salinity suggests that datasets of modern salt marsh foraminifera from multiple environments would be appropriate for reconstructing holocene relative sea level in north carolina

a 600 year annual 10be record from the ngrip ice core greenland understanding the link between the sun and climate is vital in the current incidence of global climate change and 10be in natural archives constitutes an excellent tracer for this purpose as cosmic rays enter the atmosphere cosmogenic isotopes like 10be and 14c are formed variations in solar activity modulate the amount of incoming cosmic rays and thereby cosmogenic isotope production atmospherically produced 10be enters natural archives such as sediments and glaciers by wet and dry deposition within about a year of production 10be from natural archives therefore provides information on past solar activity and because these archives also contain climate information solar activity and climate can be linked one remaining question is to what degree 10be in natural archives reflects production and to what extent the local and regional environment overprints the production signal to explore this 10be was measured at annual resolution over the last 600 years in a greenland ice core measurement potentials for these samples benefited from the development of a new laboratory method of co precipitating 10be with niobium to diversify geographic location and archive media type a pioneer study of measuring 10be with annual resolution in varved lake sediments from finland was conducted with samples from the entire 20th century pathways of 10be into lake sediments are more complex than into glacial ice inferring that contemporary atmospheric conditions may not be recorded here it is shown for the first time that tracing the 11 year solar cycle through lake sediment 10be variations is possible results also show that on an annual basis 10be deposition in ice and sediment archives is affected by local environmental conditions on a slightly longer timescale however diverse 10be records exhibit similar trends and a negative correlation with solar activity cyclic variability of 10be deposition persisted throughout past grand solar minima when little or no sunspot activity was recorded 10be levels indicate that although solar activity has been high during the 20th century levels are not unprecedented in the investigated 600 years aerosol 10be 7be values indicate possible influence of stratosphere troposphere exchange on isotope abundance and the production signal

phase of solar activity affects response of solar proxy be 10 the solar proxy be 10 measured in natural archives has previously been assumed to lag solar activity by 1 2 yr this reflects its residence time in the stratosphere where its main source lies this study based on a 30 yr global model simulation of the atmospheric transport of be 10 shows that the stratospheric fraction of production varies significantly with the phase of solar activity this leads to a lag between production change and deposition response of ca 1 yr during the decreasing phase of solar activity but nearly no lag when solar activity increases no lag is found for be 7 the fraction of 10be production in the stratosphere varies from ca 65 to 69 between solar minimum phi 400 mv and maximum phi 1200 mv being highest during low solar activity when production is highest when solar activity starts to decrease and production rate increase the change is largest in polar stratosphere where residence time is long this leads to a delayed response in be 10 deposition when production rate decreases the relative production change is larger in the troposphere leading to a quicker deposition response the difference between phases is larger in southern hemisphere the form of reconstructed 11 yr cycles based on high resolution be 10 records could therefore be biased if no correction is applied c 2013 elsevier b v all rights reserved less

cosmogenic 26al in the atmosphere and the prospect of a 26al 10be chronometer to date old ice abstract cosmogenic radionuclides in the one million year half life range offer unique possibilities for age determinations in geophysics in measurements where the radioactive decay is being utilized as a clock uncertainties in age determinations may be reduced if the ratio of two radioisotopes with different half lives can be used as a chronometer in this work we investigate the atomic ratio of atmospheric 26al t1 2 0 717 ma to 10be t1 2 1 386 ma measured with accelerator mass spectrometry ams and its potential as a chronometer for dating old ice the 26al 10be ratio decreases with an effective half life of t1 2 26al 10be 1 49 ma for its application as a chronometer the atmospheric 26al 10be ratio has to be well characterized however the properties of atmospheric 26al have been understood only poorly so far at the vera ams facility of the university of vienna a first systematic study of the global variations of the 26al 10be ratio in the atmosphere and in surface firn has been carried out and pilot measurements of the 26al 10be ratio in deep antarctic ice have been performed our results indicate that this ratio is globally constant to within 5 in the atmosphere and in surface firn with a mean value of 1 89 10 3 the data also suggest that non atmospheric sources of 26al such as extraterrestrial in situ produced or re suspended 26al do not contribute significantly to the observed 26al 10be ratio in addition atmospheric mixing seems to exert only a minor influence in a first application of the method 26al 10be ratios were measured in chips collected in connection with the drilling of the lowest part of an ice core 2250 to 2760 m in dronning maud land antarctica surprisingly variable 26al 10be ratios ranging between 0 5 and up to 2 times the atmospheric ratio were found at different locations in this deep ice core while the cause for the ratios higher than atmospheric remains unexplained so far the ratios lower than atmospheric may be caused by radioactive decay allowing a first dating attempt using the 26al 10be ratio thus at an ice depth of 2760 m an approximate date of 6 7 2 6 105 years was established

development of microcracks in granites during cooling and uplift examples from the variscan basement in ne bavaria germany abstract microcracks in two late variscan granites in ne bavaria provide information about regional paleostress directions and p t conditions during cooling and uplift in both granites three prominent generations of healed microcracks called ci cii ciii constitute an orthorhombic fabric the orientation of which is closely related to the mesoscopic joint pattern we present a model relating this orthorhombic crack fabric not only to external deviatoric stresses but also to internal stresses on the grain scale resulting from the strong thermal contraction of quartz relative to the feldspar framework at the deepest level 1 subvertical steep ci cracks developed normal to 3 and selectively in the quartz their formation caused a stress uncoupling of quartz aggregates from the external 3 direction so that further contraction of quartz produced steep cii cracks normal to 2 forming bridges between ci cracks at higher levels 2 subvertical the same process reactivated the ci cracks and now formed horizontal crack bridges ciii p t estimates based on fluid inclusion data and inferred geothermal gradients are 250 400 c at 1 5 3 kbar for ci cii cracks and 150 200 c at 1 2 kbar for ciii cracks the orientation of the younger open cracks which formed at higher crustal levels partly corresponds to the present regional stress field

using foraminiferal faunas as proxies for low tide level in the estimation of holocene tectonic subsidence new zealand abstract fossil foraminifera provide some of the most precise reconstructions of former holocene sea levels but these are based on their narrow high tidal zonation in this study we identify two foraminifera based proxies for low tide levels in sheltered harbour or estuarine mudflats one proxy is the increasing relative abundance of two calcareous foraminifera elphidium advenum and haynesina depressulus which comprise 5 of the fauna below mean low water neap level in salinities 30 psu the second proxy is based on the periodic occurrence of a wedge of low salinity low ph surface water trapped in the heads of sheltered elongate bays this water promotes the abundance of intertidal brackish agglutinated foraminifera mostly miliammina fusca and haplophragmoides wilberti and the dissolution of calcareous shelled foraminifera down to 0 5 m below extreme low water spring level we use these two foraminiferal proxies in association with the modern analog technique to estimate former sea level heights in four cores of holocene sediment from two sites in the northern south island of new zealand on the basis of these we calculate a gradual subsidence rate of 0 55 1 05 m kyr 1 over the last 4 kyr at anakoha bay in the outer marlborough sounds and no significant vertical displacement over the last 6 kyr in nelson haven 70 km to the southwest the anakoha bay results provide independent evidence in support of long held hypotheses favouring a recent subsidence origin for the deeply drowned valley systems of the marlborough sounds the nelson haven results provide constraints on recent vertical movement across the waimea flaxmore fault system which forms the western boundary of the actively uplifting east nelson mountains

paleobathymetric history of the western mediterranean sea shelf during the latest glacial period and the holocene quantitative reconstructions based on foraminiferal transfer functions abstract we present results of the palaeobathymetric evolution in cool water shelf carbonate environments of the western mediterranean sea during the latest glacial period and the holocene for this quantitative approach we used the weighted averaging partial least squares wa pls regression method for the development of benthic foraminifera based transfer functions and the modern analog technique mat to test the robustness of the models transfer functions were created on the basis of recent benthic foraminiferal assemblages in surface samples modern data sets and were then applied to fossil samples in sediment cores from the alboran platform the oran bight and the mallorca shelf the performance of the wa pls transfer functions suggests a close relationship between the observed and estimated water depths in the modern data sets with a precision of 11 m root mean squared error of prediction rmsep within water depths ranging from 38 to 160 m the estimated relative sea level histories of the alboran platform and the mallorca shelf show a total relative sea level rise of 50 m with sample specific errors of approximately 7 m and generally match the global and regional mediterranean sea records inconsistencies in the paleobathymetric estimates are strongly attributed to redeposition processes dating problems and to minor effects of an under representation of modern samples from shallower water depths

reef shallowing is a critical control on benthic foraminiferal assemblage composition on nearshore turbid coral reefs abstract declining water quality represents a major threat to the coral reefs of australia s great barrier reef gbr due to their close proximity to river point sources reefs situated on the inner shelf of the gbr are widely perceived to be most susceptible to the increased discharge of nutrients and sediments from coastal catchments many of which have been modified since european settlement however the impact and magnitude of water quality change on the gbr s inner shelf reefs remains unclear much of the uncertainty can be attributed to a paucity of long term records with which to assess ecological and environmental change over appropriate reef building timescales here we present benthic foraminiferal palaeo records from three proximal nearshore turbid zone reefs located within the central region of the gbr bayesian age depth modelling was used to identify the core intervals corresponding to the timing of european settlement in the region c 1850 ce enabling the investigation of 1 the composition and variability of benthic foraminiferal assemblages during reef shallowing towards sea level and 2 whether any signal of increased nutrient and sediment inputs as the result of historical land use change can be discerned on the most nearshore reefs of the central gbr multivariate analyses identified two assemblage groups delineated by a significant increase in the relative abundance of pararotalia spp up core our results suggest that post european settlement associated increases in nutrient and sediment inputs are unlikely to have driven the observed shifts in benthic foraminiferal assemblage composition rather we interpret changes in the composition of benthic foraminiferal assemblages as being linked to changes in hydrodynamic energy light availability and the carbonate content of reef matrix sediments during reef shallowing towards sea level our findings support the hypothesis that nearshore turbid zone reefs have a higher resistance to increased nutrient and sediment inputs than those located further offshore towards the inner mid shelf boundary of the gbr

assessing sea level data from connecticut usa using a foraminiferal transfer function for tide level concerns surrounding possible future climate change sea level rise and their potential impacts on coastal environments have stimulated research seeking to elucidate the relationship between ocean levels and climate at the sub century scale the need for increasingly precise reconstructions of relative sea level change has in turn driven the development of new methodologies capable of resolving fine scale variability within salt marsh sedimentary sequences the use of salt marsh foraminifera as precise indicators of past tide levels has played a central role in this process and is exemplified by a number of detailed studies conducted in connecticut usa in this paper we apply the most recent methodological advance in the reconstruction of relative sea levels using salt marsh foraminifera we develop a foraminiferal transfer function for tide level derived from the modern foraminiferal distributions of four connecticut salt marshes in contrast to existing approaches that employ site specific interpolations of local vertical foraminiferal assemblage zones this transfer function can provide objective quantitative and reproducible estimates of palaeomarsh surface elevation with explicitly stated error terms for marshes throughout connecticut irrespective of differences in tidal range we demonstrate the foraminiferal transfer function approach by employing it to reconstruct changes in palaeomarsh surface elevation from three cores recovered from hammock river marsh connecticut the resulting reconstructions which are precise to f0 09 m are tested using an independent dataset from the neighbouring state of maine and are used to assess a pivotal record of mean high water mhw change from this site we conclude that the transfer function reconstructions show good general agreement with previous records of palaeomarsh surface elevation but with the advantages of quantified error terms and a transparent reproducible methodology this replicability will assist in the comparison or combination of local records of mhw change to infer large scale regional sea level variations d 2003 elsevier b v all rights reserved

solar and climate influences on ice core 10be records from antarctica and greenland during the neutron monitor era abstract cosmogenic 10be in polar ice cores is a primary proxy for past solar activity however interpretation of the 10be record is hindered by limited understanding of the physical processes governing its atmospheric transport and deposition to the ice sheets this issue is addressed by evaluating two accurately dated annually resolved ice core 10be records against modern solar activity observations and instrumental and reanalysis climate data the cores are sampled from the dss site on law dome east antarctica spanning 1936 2009 and the das2 site southeast greenland 1936 2002 permitting inter hemispheric comparisons concentrations at both dss and das2 are significantly correlated to the 11 yr solar cycle modulation of cosmic ray intensity r xy 0 54 with 95 ci 0 31 0 70 and r xy 0 45 with 95 ci 0 22 0 62 respectively for both sites if fluxes are used instead of concentrations then correlations with solar activity decrease the strength and spectral coherence of the solar activity signal in 10be is enhanced when ice core records are combined from both antarctica and greenland the amplitudes of the 11 yr solar cycles in the 10be data appear inconsistent with the view that the ice sheets receive only 10be produced at polar latitudes significant climate signals detected in the 10be series include the zonal wave three pattern of atmospheric circulation at dss r xy 0 36 with 95 ci 0 57 0 10 and the north atlantic oscillation at das2 r xy 0 42 with 95 ci 0 64 0 15 the sensitivity of 10be concentrations to modes of atmospheric circulation advises caution in the use of 10be records from single sites in solar forcing reconstructions

contemporary distribution of benthic foraminiferal assemblages in coastal wetlands of south eastern australia abstract benthic foraminifera identified from the upper intertidal zone of coastal mangrove and saltmarsh wetlands of south eastern australia exhibit spatial zonation that varies with elevation and corresponds to position in the tidal frame this study describes relationships between benthic foraminiferal assemblages and environmental variables such as wetland elevation pore water salinity substrate organic matter content and sediment grainsize agglutinated taxa dominated higher in the tidal frame whereas calcareous taxa increased in both relative abundance and diversity lower in the tidal frame species composition varied within and between study sites reflecting local differences in other environmental variables three major spatial clusters were identified in the upper intertidal zone from a dataset consisting of 111 contemporary samples a high to mid elevation assemblage consisting of differing abundances of entzia macrescens and trochammina inflata a mid elevation assemblage comprised of arenoparrella mexicana in association with trochammina inflata and quinqueloculina seminula and mid to low elevation assemblage characterised by cribroelphidium excavatum quinqueloculina seminula ammobaculites spp and miliammina fusca multivariate analysis correlated foraminiferal assemblages with environmental variables showing that foraminiferal distribution in the region is constrained primarily by wetland elevation but also by pore water salinity foraminiferal assemblages derived from cluster analysis correlated with vegetation zones implying that both foraminifera and vegetation are influenced by elevation and salinity this paper seeks to demonstrate that the consistency in spatial zonation of assemblages provides greater confidence that contemporary distribution of foraminiferal assemblages can assist with the interpretation of past depositional conditions and palaeo environmental reconstructions providing insights into the evolution of coastal wetlands of south eastern australia over the holocene

the application of local and regional transfer functions to the reconstruction of holocene sea levels north norfolk england foraminiferal assemblages from thornham and brancaster marshes norfolk uk illustrate statistically significant relationship with elevation with respect to the tidal frame we develop local data from thornham and brancaster marshes and regional data from thornham and brancaster marshes combined with those from 11 other sites around the uk predictive foraminifera based transfer functions to reconstruct former sea levels from a holocene sediment sequence from holkham north norfolk uk the two transfer functions produce similar patterns of tidal elevation change during the holocene the vertical error ranges of the local transfer function are smaller than those of the regional transfer function although the difference 0 09 m is not significant when compared to other factors affecting the reconstructed elevation the value of the reconstructed elevations also differ between the two transfer functions by up to 0 43 m and this is primarily due to the lack of modern analogues in the local transfer function we conclude that the reconstructions derived from the regional transfer function are more reliable than those of the local transfer function since the latter achieves its slight increase in precision at the expense of a significant decrease in predictive power the regional transfer function is used to construct a relative sea level curve from fossil assemblages within a sediment core from north norfolk uk these results are consistent with existing sea level data and geophysical model predictions and illustrate the utility of the foraminifera based transfer function approach

stratigraphic evidence for an early holocene earthquake in aceh indonesia abstract the holocene stratigraphy of the coastal plain of the aceh province of sumatra contains 6 m of sediment with three regionally consistent buried soils above pre quaternary bedrock or pre holocene unconsolidated sediment litho bio and chronostratigraphic analyses of the lower buried soil reveals a rapid change in relative sea level caused by coseismic subsidence during an early holocene megathrust earthquake evidence for paleoseismic subsidence is preserved as a buried mangrove soil dominated by a pollen assemblage of rhizophora and or bruguiera ceriops taxa the soil is abruptly overlain by a thin tsunami sand the sand contains mixed pollen and abraded foraminiferal assemblages of both offshore and onshore environments the tsunami sand grades upward into mud that contains both well preserved foraminifera of intertidal origin and individuals of the gastropod cerithidea cingulata radiocarbon ages from the pre and post seismic sedimentary sequences constrain the paleoearthquake to 6500 7000 cal yrs bp we use micro and macrofossil data to determine the local paleoenvironment before and after the earthquake we estimate coseismic subsidence to be 0 45 0 30 m which is comparable to the 0 6 m of subsidence observed during the 2004 aceh andaman earthquake on aceh s west coast

quantitative vertical zonation of salt marsh foraminifera for reconstructing former sea level an example from new jersey usa we present a quantitative technique to reconstruct sea level from assemblages of salt marsh foraminifera using partitioning around medoids pam and linear discriminant functions ldf the modern distribution of foraminifera was described from 62 surface samples at three salt marshes in southern new jersey pam objectively estimated the number and composition of assemblages present at each site and showed that foraminifera adhered to the concept of elevation dependent ecological zones making them appropriate sea level indicators application of pam to a combined dataset identified five distinctive biozones occupying defined elevation ranges which were similar to those identified elsewhere on the u s mid atlantic coast biozone a had high abundances of jadammina macrescens and trochammina inflata biozone b was dominated by miliammina fusca biozone c was associated with arenoparrella mexicana biozone d was dominated by tiphotrocha comprimata and biozone e was dominated by haplophragmoides manilaensis foraminiferal assemblages from transitional and high salt marsh environments occupied the narrowest elevational range and are the most precise sea level indicators recognition of biozones in sequences of salt marsh sediment using ldfs provides a probabilistic means to reconstruct sea level we collected a core to investigate the practical application of this approach ldfs indicated the faunal origin of 38 core samples and in cross validation tests were accurate in 54 of 56 cases we compared reconstructions from ldfs and a transfer function the transfer function provides smaller error terms and can reconstruct smaller rsl changes but ldfs are well suited to rsl reconstructions focused on larger changes and using varied assemblages agreement between these techniques suggests that the approach we describe can be used as an independent means to reconstruct sea level or importantly to check the ecological plausibility of results from other techniques

coastal subsidence in oregon usa during the giant cascadia earthquake of ad 1700 quantitative estimates of land level change during the giant ad 1700 cascadia earthquake along the oregon coast are inferred from relative sea level changes reconstructed from fossil foraminiferal assemblages preserved within the stratigraphic record a transfer function based upon a regional training set of modern sediment samples from oregon estuaries is calibrated to fossil assemblages in sequences of samples across buried peat mud and peat sand contacts marking the ad 1700 earthquake reconstructions of sample elevations with sample specific errors estimate the amount of coastal subsidence during the earthquake at six sites along 400 km of coast the elevation estimates are supported by lithological carbon isotope and faunal tidal zonation data coseismic subsidence at nehalem river nestucca river salmon river alsea bay siuslaw river and south slough varies between 0 18 m and 0 85 m with errors between 0 18 m and 0 32 m these subsidence estimates are more precise consistent and generally lower than previous semi quantitative estimates following earlier comparisons of semi quantitative subsidence estimates with elastic dislocation models of megathrust rupture during great earthquakes our lower estimates for central and northern oregon are consistent with modeled rates of strain accumulation and amounts of slip on the subduction megathrust and thus with a magnitude of 9 for the ad 1700 earthquake

evidence for two great earthquakes at anchorage alaska and implications for multiple great earthquakes through the holocene abstract multiple peat silt couplets in tidal marsh sediment sequences at anchorage suggest up to five possible great earthquakes during the last 2500 years litho stratigraphic diatom and radiocarbon data of the youngest two couplets record the last two great earthquakes ad 1964 and 950 850 cal yr bp similar multiple peat silt couplets around cook inlet suggest recurring great earthquakes associated with marsh subsidence over large areas comparable in extent to that recorded in ad 1964 potential difficulties in interpreting evidence include lack of modern analogues for applying quantitative diatom transfer functions to parts of the fossil record and the observation that under certain sedimentary conditions co seismic subsidence in the case of ad 1964 of known magnitude is recorded by a transitional peat silt boundary this differs in diatom stratigraphy from a phase of pre seismic relative sea level rise recorded for other great earthquakes a field experiment to simulate co seismic subsidence identifies limited mixing at the top of submerged marsh sediment and indicates how mixing must be shown to differ from evidence for pre seismic relative sea level rise analysis of diatom assemblages from ice frozen intertidal sediment and melt out sediment demonstrates the importance of winter processes in transporting diatoms and their interpretation in fossil sequences winter processes may also be important in transporting organic material that leads to significant differences 120 2800 yr between radiocarbon ages from plant macrofossils and bulk peat samples this necessitates a new approach for establishing between site correlations recurrence intervals and spatial extent of great holocene earthquakes in southern alaska

recent horizontal stress directions in basement rocks of southern sweden deduced from open microcracks abstract the strike direction of open intragranular microcracks in quartz and feldspar host grains was determined using optical transmission and reflection microscopy on eight oriented samples taken in two study areas in precambrian basement rocks of southern and south central sweden for an area of about 160 km 2 sw of vastervik and two sample locations w of uppsala the vast majority of open microcracks displays a strong preferred nw se strike direction according to the common assumptions that natural cracks in crystalline rocks are predominantly extensional mode i and that open cracks belong to the latest microcrack generation these strike directions should reflect the sub recent main horizontal stress direction h of the recent tectonic stress field this conclusion is supported by corresponding directions known from in situ stress measurements and focal plane solutions in the vicinity of the study areas it is remarkable that even in samples taken close i e a few hundred metres to recently active large scale faults the orientation of microcracks does not deviate from this common direction this may point to slip on already softened faults very local stress reorientations e g m scale or that local stress relief was accomplished by other processes at micro scale e g mechanical twinning in favourably oriented feldspar crystals or slip on grain boundaries

the application of foraminifera to reconstruct the rate of 20th century sea level rise morbihan golfe brittany france abstract foraminiferal assemblages preserved within salt marsh sediment can provide an accurate and precise means to reconstruct relative sea level due to a strong relationship with elevation which can be quantified using a transfer function we collected a set of surface samples from two salt marshes in the morbihan golfe france to determine foraminiferal distribution patterns dominant taxa included jadammina macrescens trochammina inflata haplophragmoides spp and miliammina fusca we developed a foraminifera based transfer function using a modern training set of 36 samples and 23 species the strong relationship between observed and predicted values r 2 jack 0 7 indicated that foraminiferal distribution is primarily controlled by elevation with respect to the tidal frame and precise reconstructions of former sea level are possible rmsep jack 0 07 m the application of the transfer function to a short salt marsh core 0 32 m allowed the reconstruction of former sea levels which were placed in a chronological framework using short lived radionuclides 210 pb and 137 cs the agreement between the foraminifera based sea level curve and the brest tide gauge record confirms the reliability of transfer function estimates and the validity of this methodology to extend sea level reconstructions back into the pre instrumental period both instrumental and microfossil records suggest an acceleration of sea level rise during the 20th century

structural model for the saxothuringian moldanubian suture in the variscan basement of the oberpfalz northeastern bavaria f r g interpreted from geophysical data abstract the moldanubian saxothuringian boundary marks a prominent subduction zone in the internal parts of the european variscides in the oberpfalz area deep reflection seismic profiles show a high density of various reflectors mainly in the upper crust indicating a complex polyphase deformation during the collision process seismic structures and related data from surface geology suggest that the moldanubian saxothuringian collision consisted of two main phases the first phase is marked by extensive nw directed overthrusting of moldanubian onto saxothuringian crust along se dipping master decollements some of which can be traced down to the moho during an advanced stage progressive overthrusting led to the development of wedge structures associated with se directed backthrusting and backfolding in the upper structural levels subsequently some of these wedges and their related decollements were folded to form the main ne striking anticlines the first phase of crustal imbrication correlates with a regional low pressure high temperature metamorphism at about 320 ma decreasing in grade northwestward the second phase is characterized by a reorientation of the main direction of crustal shortening from nw se to sw ne which is interpreted as the result of the n directed indentation of the vindelician terrane into the moldanubian this event is recorded by conjugate systems of overthrusting and subsequent strike slip faulting in the oberpfalz and the bavarian forest and the black forest vosges area in the area of the southern german block between these basement outcrops the indentation front is marked by the arc shaped axes of gravimetric and magnetic anomalies and permo carboniferous troughs

thermobarometry and p t path of garnet aluminosilicate bearing gneisses from the ktb drill core continental deep drilling project germany garnet zoning characteristics reaction microstructures and thermobarometric studies document a multistage p t evolution for the paragneisses of the ktb drill core the prograde heating and burial path led through the sillimanite stability field before it entered the kyanite field close to the p t peak the uppermost paragneiss amphibolite unit 0 560 m reached peak conditions at 650 670 c and 7 8 kbar the units below 560 3574 m show higher peak temperatures of 680 720 c with maximum pressures between 8 and 9 kbar this p t discontinuity implies a tectonic contact but otherwise the two sections of the drill core do not show evidence for a separate metamorphic history and probably lay on a common crustal paleogeotherm at peak conditions homogenization of mg fe and mn in garnet at or near peak conditions points to a significant time interval between burial and subsequent decompression accordingly the prograde metamorphic episode must be significantly older than the 380 370 ma decompression and cooling period possibly mid ordovician following nearisothermal decompression with partial breakdown of garnet and growth of sillimanite a second previously unrecognized pressure peak was reached at 5 7 6 7 kbar and temperatures of around 590 c a late low pressure imprint is documented by the local presence of andalusite the lack of a continuous metamorphic p t gradient in the drilled crustal section either requires strong postmetamorphic tilting of isograds and or small scale intraformational stacking of crustal slices of similar metamorphic grade

foraminifera in a new zealand salt marsh and their suitability as sea level indicators abstract vertical distributions of live and dead foraminiferal abundances are investigated in a salt marsh at pounawea in southeastern new zealand for potential use in holocene sea level reconstructions statistical analyses are conducted to determine whether dead foraminiferal abundances can be utilised as a proxy for elevation in southeastern new zealand it is concluded that dead salt marsh foraminifera which can predict elevations to within 5 cm or better are precise sea level proxies holocene sea level reconstructions along the tectonically stable catlins coast based on fossil salt marsh foraminifera can therefore serve as a potential baseline tool to estimate relative vertical tectonic displacement along tectonically active coasts in new zealand

stress dependent morphological features on fracture surfaces of quartz and glass abstract stress dependent morphological features have been found on tensile fracture surfaces of natural brazilian quartz and synthetic quartz specimens which were flexed in air at room temperature these features are similar to stress dependent morphological features found on fracture surfaces of pyrex soda lime and lead glass when deformed in similar experiments for glass the relevant morphological feature is the fracture mirror a planar region surrounding the initial flaw stress dependent index features chosen for measurement in quartz depend upon the crystallographic orientation on the fracture surface their development is related to the crack system energy but in contrast to glass the features are not directly related to crack branching the experimental results follow an equation of the form a f r 1 2 where f is the fracture stress r is the size of a particular morphological feature e g the mirror radius in the case of glass and a is a constant from the magnitudes of a and the fracture toughness determined in these experiments we conclude that the natural brazilian quartz used in this study has significantly higher resistance to fracture than synthetic quartz

an antarctic circumpolar wave in surface pressure wind temperature and sea ice extent the southern ocean is the only oceanic domain encircling the globe it contains the strong eastward flow of the antarctic circumpolar current and is the unifying link for exchanges of water masses at all depths between the world s major ocean basins1 as these exchanges are an important control on mean global climate the southern ocean is expected to play an important role in transmitting climate anomalies around the globe interannual variability has been often observed at high southern latitudes and observations of sea ice extent suggest that such features propagate eastwards around the southern ocean2 3 here we use data from a variety of observational techniques to identify significant interannual variations in the atmospheric pressure at sea level wind stress sea surface temperature and sea ice extent over the southern ocean these anomalies propagate eastward with the circumpolar flow with a period of 4 5 years and taking 8 10 years to encircle the pole this system of coupled anomalies which we call the antarctic circumpolar wave is likely to play an important role in climate regulation and dynamics both within and beyond the southern ocean

ice core evidence for secular variability and 200 year dipolar oscillations in atmospheric circulation over east antarctica during the holocene two holocene ice core records from east antarctica vostok and epica dome c were analysed for dust concentration and size distribution at a temporal resolution of 1 sample per 50 years a series of volcanic markers randomly distributed over the common part of the ice cores from 9 8 to 3 5 kyear bp ensures accurate relative dating 33 years dust size records from the two sites display oscillations structured in cycles with sub millennial and secular scale frequencies that are apparently asynchronous the power spectra of the composite sum of the two dust size records display spectral energy mostly for 150 to 500 year periodicities on the other hand the 200 year band is common to both records and the 200 year components of the two sites are out of phase 100 year lead or lag over 5 5 kyear a phenomenon also reflected by a significant 99 conf lev band in the power spectra of the composite difference of the two size records during long range transport mineral dust originating from the southern hemisphere continents is graded to a variable extent depending on the altitude and duration of atmospheric transport relatively coarse dust is associated with air mass penetration from the middle lower troposphere and conversely relatively fine dust with upper troposphere air masses or the influence of subsidence over the antarctic plateau a hypothesis already proposed for the changes that occurred during the last glacial maximum to holocene transition delmonte et al 2004b moreover we assume that the overall fluctuation of air mass advection over antarctica depends on the meridional pressure gradient with respect to low latitudes i e the antarctic oscillation aao we therefore suggest a regional variability in atmospheric circulation over east antarctica the 150 500 year power spectrum of the composite parameter represents the long term variability of the aao imprinted by secular internal oscillations probably related to the southern ocean climatic system on the other hand the dust composite parameter suggests a persistent atmospheric dipole over east antarctica delivering coarser finer dust particles alternatively to vostok and dome c regions with a bi centennial periodicity indeed a seesaw phenomenon in dust size distribution was already observed at three east antarctic sites during the last deglaciation delmonte et al 2004b and was interpreted as a progressive reduction of the eccentricity of the polar vortex with respect to the geographic south pole interestingly the parameter shows a pronounced 200 year oscillation mode throwing new light on the unresolved question of a possible relationship between climate and solar activity

volcanic and solar activity and atmospheric circulation influences on cosmogenic 10be fallout at vostok and concordia antarctica over the last 60years abstract the cosmogenic nuclide beryllium 10 10be recovered from ice cores is often used to study solar activity on long timescales however the 10be signal is also influenced by factors other than the sun to identify and quantify various contributions to the 10be signal two antarctic snow records from the vostok and concordia sites spanning the last 60 years were studied at a sub annual resolution three factors that contribute to the 10be signal were identified first a significant period of approximately 11 yr that can be associated with the modulation of 10be production by solar activity was detected in both records the solar imprint constitutes 20 35 of the variance within the total signal the 11 yr 10be snow component was attenuated by a factor of 0 5 and was delayed by 1 4 yr compared to the 10be production expected within the polar atmosphere the result could be interpreted as the composite response of a stratospheric 10be reservoir with an 11 yr modulation that was attenuated and delayed with respect to 10be polar production and to a tropospheric 10be reservoir with an 11 yr modulation that was not attenuated or delayed then peaks in 10be concentrations that were 66 and 35 higher than the average concentration were observed during the stratospheric volcanic eruptions of agung in 1963 and pinatubo in 1991 respectively in light of these new results published 10be ice core records could be reinterpreted because spikes in 10be concentration appear at the time of several stratospheric events the data indicate that stratospheric volcanic eruptions can impact 10be transport and deposition as a result of the roles played by the sedimentation of sulfate aerosols and the formation and rapid settling of polar stratospheric clouds psc also an interannual variability of 4 yr was determined in both 10be records corresponding to 26 of the variance within the signal at vostok as with species of marine origin sodium this 4 yr variability is interpreted as a tropospheric modulation the 4 yr variability could be associated with atmospheric circulation associated with the coupled southern ocean ocean atmosphere system the results presented here from sites within the high antarctic plateau open new possibilities for ice core dating over the last few centuries and for the reconstruction of past solar activity in relation to climate

microfracturing and regional stress field a study of the preferred orientations of fluid inclusion planes in a granite from the massif central france abstract a study of the deformation of a granitic massif indicates a relationship between palaeostress fields and the geometry of microfractures as defined by fluid inclusion trails that is healed microfractures a statistical study of the distribution of the trails leads to the following conclusions trails exhibit several distinct preferred orientations on the scale of a grain which may be observed in many samples the orientations of the trails are similar to those of micro and mesoscale fractures in the granite and the dominant trail direction is parallel to the main direction of regional shortening thus fluid inclusion trails are mode i cracks which can be used as excellent markers of palaeostress fields

formation and evolution of snowball quartz phenocrysts in the dongping porphyritic granite hebei province china insights from fluid inclusions cathodoluminescence trace elements and crystal size distribution study abstract quartz phenocrysts are common in many granites volcanic rocks metamorphic rocks and hydrothermal deposits the dongping porphyritic granite contains large amounts of rounded to sub rounded quartz phenocrysts minerals in this porphyritic granite show weak but distinct orientation dense clusters of fluid inclusions and albite crystals exist in the quartz showing snowball texture two types of snowball quartz are recognized 1 large snowball quartz phenocrysts containing large albite grains distributed in the core and small albite grains distributed in the mantle and 2 small snowball quartz crystals containing small albite grains the granite is characterized by high sio2 7 15 73 44 wt k2o 4 70 5 10 wt and na2o 4 93 5 21 wt contents low cao 0 41 0 71 wt mgo 0 03 0 05 wt fe2o3 0 87 0 94 wt tio2 0 02 0 03 wt and ree 7 10 9 80 ppm contents the granite has similar mineral and chemical composition with the aplite in the area and they were derived from the residual melt of the shuiquangou magma that suffered assimilation fractional crystallization process fluid inclusions in the quartz phenocrysts have homogenization temperatures of 260 380 c and salinities of 1 4 12 4 wt nacl equiv for liquid vapor type inclusions and 34 1 44 3 wt nacl equiv for brine ones the quartz phenocrysts exhibit homogeneous cathodoluminescence without growth bands or zoning the trace element contents in the quartz phenocrysts are extremely low ti 3 4 5 1 ppm al 13 118 ppm li

evolution of quartz microstructure and c axis crystallographic preferred orientation within ductilely deformed granitoids arolla unit western alps abstract we have studied quartz microstructures and the c axis crystallographic preferred orientations cpos in four granitoid samples representative of increasing ductile shear deformation from a weakly deformed granitoid stage 1 to a mylonitic granitoid stage 4 the quartz c axis cpo measured in the mylonitic granitoid has been compared with the one observed in a fully recrystallized quartz mylonite from the same area all the samples belong to the austroalpine arolla unit western alps and were deformed at greenschist facies conditions the quartz c axis cpo was analyzed using a u stage and the optical orientation imaging technique the magmatic plagioclase forming more than 50 of the volume of the granitoid is extensively replaced by a mica rich aggregate even in weakly deformed samples of stage 1 these aggregates flow to form an interconnected weak matrix with increasing deformation wrapping relatively less strained quartz grains that undergo dominantly coaxial strain recrystallization of quartz ranges from less than 1 in the weakly deformed granitoid to up to 85 in the mylonitic granitoid with average grain strain of 41 and 64 respectively with increasing strain and recrystallization quartz grains in the granitoids show a sequence of transient microstructures and cpos crystal plastic deformation is initially accomplished by dislocation glide with limited recovery and at 50 grain strain it results in a cpo consistent with dominantly basal a slip at 60 grain strain recrystallization is preferentially localized along shear bands which appear to develop along former intragranular cracks and the recrystallized grains develop a strong c axis cpo with maxima orthogonal to the shear band boundaries and independent of the host grain orientation within the granitoid mylonite at an average quartz grain strain of 64 recrystallization is extensive and the c axis cpo of new grains displays maxima overlapping the host c axis orientation and therefore unrelated to the bulk sense of shear the host controlled cpo is inferred to reflect pervasive recrystallization by progressive subgrain rotation the switch from shear band control to host control on c axis cpo occurred between 40 and 70 of recrystallization in the quartz mylonite the quartz c axis cpo develops an asymmetric single girdle consistent with the bulk sense of shear and the synkinematic greenschist facies conditions this study indicates that the cpo evolution of quartz may significantly differ in cases of polymineralic vs monomineralic rocks under the same deformation conditions if quartz in the polymineralic rock behaves as a strong phase

modern diatom assemblages from chilean tidal marshes and their application for quantifying deformation during past great earthquakes tidal marsh sediments from south central chile provide evidence for multiple great earthquakes diatom transfer functions statistical models of the relationship between species preserved in the sediment and elevation provide quantitative estimates of coseismic vertical land level change associated with individual earthquakes however in south central chile our ability to quantify land level change is currently limited by a lack of understanding of the environmental variables controlling the distribution of diatoms an essential prerequisite for converting variations in fossil diatom assemblages into quantitative estimates of past elevation changes we present a new modern diatom dataset for the region and explore the implications of the scale of the dataset used in transfer function models on the reconstructions of land level change modern training sets containing samples from a regional scale are superior to sub regional and local scale training sets providing closer estimates for known deformation during the great 1960 chilean earthquake a higher proportion of good modern analogues and uncertainty terms up to 42 smaller than previously published reconstructions copyright 2017 the authors journal of quaternary science published by john wiley sons ltd

holocene palaeoenvironmental evolution of the ebro delta western mediterranean sea evidence for an early construction based on the benthic foraminiferal record major mediterranean deltas began to develop during a period between 8000 and 6000 yr bp when the rate of fluvial sediment input overtook the declining rate of sea level rise however different aut

a review of the ecological and taphonomic controls on foraminiferal assemblage development in intertidal environments intertidal foraminifera from surface sediments are commonly used as a high resolution indicator of sea level change the integrity of this approach is based upon the assumption that surface assemblages are similar in composition to their buried fossil counterparts this assumption may in some cases be inappropriate due to subsurface or infaunal production and taphonomic alteration here we review the current understanding of foraminiferal production and taphonomic loss in intertidal environments and examine the extent to which these processes can affect the development of foraminiferal assemblages in intertidal environments as a sediment layer undergoes burial dead tests are added at a rate proportionate to the standing crop at that depth as a consequence test accumulation within the layer is proportionate to the depth integrated standing crop depending on the nature of its vertical living distribution the upper 1 cm of sediment may therefore not adequately characterise a given species total input instead a comparison of each species contribution to the entire depth integrated living community may offer a better a priori estimate of relative input to the sediment column this provides an improved base line for identifying true taphonomic trends downcore the potential for infauna to create discrepancies between surface and subsurface assemblages may be minimised however where 1 reproduction is concentrated near to the sediment surface transforming an apparent infaunal standing crop into an effective epifaunal production 2 the living fauna is composed similarly at all depths of production and or 3 intense bioturbation homogenises the upper sediment layers the likely decline in the intensity of taphonomic processes with depth may mean that the foraminiferal production from different depths may not experience taphonomic processes uniformly consequently in addition to their possible gradual enrichment due to subsurface production infaunal species may be preferentially preserved by virtue of their production closer to the base of the taphonomically active zone additionally homogenisation of the sediment column by reworking may mix temporally and perhaps environmentally distinct faunas affecting the stratigraphic integrity of the sediment deposit the most important taphonomic processes in intertidal environments are those associated with early diagenesis while the organic cements of agglutinated taxa may be directly oxidised the associated changes in the saturation state of porewaters with respect to calcium carbonate may affect calcareous species the type of diagenetic reaction operating within the sediment provides a quantitative control on agglutinated test degradation but a largely qualitative control on calcareous preservation in addition calcareous test preservation is dependent upon the rate with which organic matter is supplied while agglutinated test preservation is independent of organic matter concentrations although the specific morphological pathways of test degradation for calcareous species are well understood the stages under which agglutinated tests are lost are less clear the combined but varying influences of production infaunal and species composition taphonomic processes and bioturbation may create complex pathways in the transition from live to dead to fossil assemblages understanding the extent to which infauna taphonomic loss and sediment reworking affect assemblage development in different intertidal environments is essential in order to interpret the fossil record

developing detailed records of relative sea level change using a foraminiferal transfer function an example from north norfolk uk this paper provides a brief overview of the transfer function approach to sea level reconstruction using the example of two overlapping sediment cores from the north norfolk coast uk the advantages and limitations of the transfer function methodology are examined while the selected cores are taken from different sites and display contrasting patterns of sedimentation the foraminiferal transfer function distils comparable records of relative sea level change from both sequences these reconstructions are consistent with existing sea level index points from the region but produce a more detailed record of relative sea level change transfer functions can extract sea level information from a wider range of sedimentary sub environments this increases the amount of data that can be collected from coastal deposits and improves record resolution the replicability of the transfer function methodology coupled with the sequential nature of the data it produces assists in the compilation and analysis of sea level records from different sites this technique has the potential to bridge the gap between short term instrumental and long term geological or geophysical records of sea level change

crystallographic orientation of microcracks in quartz and inferred deformation processes a study on gneisses from the german continental deep drilling project ktb abstract this study was carried out on four gneiss samples from the german continental deep drilling project ktb taken at depths between 556 and 8633 m the crystallographic orientation of microcracks in quartz was determined by a combination of the electron channelling pattern method ecp and u stage microscopy the distinct preferred crystallographic orientations of various crack generations point to different processes of crack initiation and propagation which partly seem to be depth dependent for older healed cracks a crystalplastic initiation due to dislocation pile up and related lattice distortion is indicated by cracking normal to prominent slip directions which are a at lower or c at comparatively higher temperatures in contrast younger open cracks preferentially formed on crystallographic planes with low surface energy rhombs and prisms which is interpreted in terms of pure elastic crack mechanisms because of the thermoelastic anisotropy of quartz internal stresses resulting from thermal contraction during cooling may be the main driving force for the initiation or further propagation of cracks parallel to the c axis crack propagation preferentially affects grains with crystal lattices and operating crack mechanisms being in a direction appropriate to the applied external tectonic stresses this selective cracking explains why cracks also show constant orientations with respect to geographic directions up to regional dimensions

crystallographic control and texture inheritance during mylonitization of coarse grained quartz veins abstract quartz veins within rieserferner pluton underwent deformation during post magmatic cooling at temperature around 450 c different crystallographic orientations of cm sized quartz vein crystals conditioned the evolution of microstructures and crystallographic preferred orientations cpo during vein parallel simple shear up to high shear strains 10 for glide in ribbons with c axis sub parallel to the shear zone vorticity y axis ribbons with c axis orthogonal to y xz type ribbons were stronger and hardened more quickly they show lower aspect ratios and fine grain size 10 20 m recrystallization along sets of microshear zones szs exploiting crystallographic planes distortion of xz type ribbons and recrystallization preferentially exploited the slip systems with misorientation axis close to y new grains of szs initiated by subgrain rotation recrystallization sgr and thereupon achieved high angle misorientations by a concurrent process of heterogeneous rigid grain rotation around y associated with the confined shear within the sz dauphine twinning occurred pervasively but did not play a dominant role on sz nucleation recrystallization became widespread at 2 and pervasive at 10 ultramylonitic quartz veins are fine grained 10 m similar to new grains of sz and show a cpo banding resulting in a bulk c axis cpo with a y maximum as part of a single girdle about orthogonal to the foliation and orientations at the pole figure periphery at moderate to high angle to the foliation this bulk cpo derives from steady state sgr associated with preferential activity in the different cpo bands of slip systems generating subgrain boundaries with misorientation axes close to y the cpo of individual recrystallized bands is largely inherited from the original crystallographic orientation of the ribbons and therefore vein crystals from which they derived high strain and pervasive recrystallization were not enough to reset the initial crystallographic heterogeneity and this cpo memory is explained by the dominance of sgr this contrast with experimental observation of a rapid erasure of a pristine cpo by cannibalism from grains with the most favourably oriented slip system under dominant grain boundary migration recrystallization

solar modulation of cosmogenic nuclide production over the last millennium comparison between 14c and 10be records for about the last 30 years it has been recognized that the high frequency component of the tree rings 14c 12c record is dominated by the modulation of the cosmic ray flux by the solar wind in particular it has been demonstrated that the three most recent periods of low sunspot occurrence were characterized by high values of atmospheric 14c 12c during the last millennium other periods of high 14c 12c values were observed but their solar origin is still debatable in the present work we compare these fluctuations with an independent record of cosmogenic 10be measured in ice from the south pole to check the solar origin of the observed 14c 12c variations in order to compare quantitatively the results obtained on 10be and 14c it is necessary to take into account the different behaviour of these two cosmogenic isotopes and especially the damping effect of the carbon cycle in the case of 14c as an input to a 12 box numerical model we used the relative fluctuations of the 10be concentrations record measured in south pole ice and converted it into a synthetic 14c record we took into account the fact that 10be modulation is enhanced in polar regions due to the orientation of the geomagnetic field as expected the fluctuations of the modelled 14c record are much smaller a factor of 20 than those observed for the raw 10be record in addition the variations are smoother and shifted in time by a few decades the 10be based 14c variations closely resemble the 14c measurements obtained on tree rings r 0 81 in particular it is easy to identify periods of maximal 14c 12c which correspond to solar activity minima centred at about 1060 1320 wolf 1500 sporer 1690 maunder and 1820 dalton yr a d cross correlation calculations suggest that there is no significant lag between the 10be based 14c and the tree ring 14c records our study strongly suggests the dominance of the solar modulation on the cosmonuclide production variations during the last millennium

dynamic recrystallization near the brittle plastic transition in naturally and experimentally deformed quartz aggregates the electron backscattering diffraction technique ebsd was used to analyze bulging recrystallization microstructures from naturally and experimentally deformed quartz aggregates both of which are characterized by porphyroclasts with finely serrated grain boundaries and grain boundary bulges set in a matrix of very fine recrystallized grains for the tonale mylonites we investigated a temperature range of 300 380 c 0 25 gpa confining pressure a flow stress range of 0 1 0 2 gpa and a strain rate of 10 13 s 1 were estimated experimental samples of black hills quartzite were analyzed which had been deformed in axial compression at 700 c 1 2 1 5 gpa confining pressure a flow stress of 0 3 0 4 gpa a strain rate of 10 6 s 1 and to 44 to 73 axial shortening using orientation imaging we investigated the dynamic recrystallization microstructures and discuss which processes may contribute to their development our results suggest that several deformation processes are important for the dismantling of the porphyroclasts and the formation of recrystallized grains grain boundary bulges are not only formed by local grain boundary migration but they also display a lattice misorientation indicative of subgrain rotation dynamic recrystallization affects especially the rims of host porphyroclasts with a hard orientation i e with an orientation unsuitable for easy basal slip in addition dauphine twins within porphyroclasts are preferred sites for recrystallization we interpret large misorientation angles in the experimental samples which increase with increasing strain as formed by the activity of fluid assisted grain boundary sliding

holocene relative sea level movements along the north norfolk coast uk abstract relative changes in holocene sea level are reconstructed from foraminiferal assemblages in seven cores recovered from the intertidal zone of north norfolk eastern england a total of 33 radiocarbon and infra red stimulated luminescence dates provide a detailed chronological framework for these changes a transfer function approach developed from modern uk foraminiferal datasets establishes a series of 21 new sea level index points for this coastline which are combined with 18 existing index points and a further number of limiting values errors associated with changing tidal ranges through the holocene are reduced by adopting recently developed tidal models for this period this new approach allows the use of foraminiferal assemblages to be extended from the upper saltmarsh environment traditionally used for sea level studies to lower elevations in the tidal frame and include clastic detrital sediments the results confirm the previously observed trend of continuously rising sea levels in this area during the last 10 000 years which is consistent with a glacial isostatic adjustment model relative sea level rsl rises from an observed minimum of approximately 13 50 m od at about 7500 cal bp to approximately 4 0 m at about 5300 cal bp which equates to a mean rise of c 4 3 mm yr 1 subsequently rsl rose gradually to present levels although there is evidence that a minor reverse in this trend occurred between 4000 and 2000 cal bp when sea level fell by about 1 m to c 3 5 m the rate of land subsidence for north norfolk is 0 54 0 03 mm yr 1 inverse of late holocene sea level rise

assessing the performance of a foraminifera based transfer function to estimate sea level changes in northern portugal a b s t r a c t a r t i c l e i n f o article history received 14 april 2010 available online 15 december 2010 we assessed the performance of a transfer function model for sea level studies using salt marsh foraminifera from two estuaries of northern portugal an independent data set of 12 samples and 13 sub fossil samples from a core were used to evaluate if reconstructions and errors derived from current models are adequate initial transfer function models provided very strong results as indicated by cross validation component 2 r 2 0 80 0 82 rmsep ranged from 10 7 to 12 3 cm and improved its performance by ca 10 when sample size reached ca 50 results derived using an independent test data set indicate that cross validation is a very effective approach and produces conservative errors when compared to observed errors we additionally explored the possible effect of transforming the concentration data into percent in the error estimations by comparing the results obtained based on the use of both concentration and compositional data results indicate that this type of transformation does not affect the performance of the transfer function results derived from a reconstruction of sub fossil samples from a core indicate that high resolution sea level reconstructions are possible but show that depositional environments have to be selected carefully in order to minimize the impact of possible taphonomical loss

impact of eustatic and tectonic processes on the southeastern mediterranean shelf during the last one million years quantitative reconstructions using a foraminiferal transfer function abstract benthic foraminifera based transfer function models provide accurate sea level reconstructions for shelf and coastal environments around the world this study presents for the first time results of a foraminiferal transfer function aiming at the reconstruction of relative sea level in the southeastern mediterranean shelf during the past one million years a weighted averaging partial least squares wa pls regression method was used for the development of the transfer function based on an extensive set of surface samples modern training data set from the study area the transfer function was applied to three shelf sediment successions retrieved from haifa bay israel the modern analog technique mat and the random tf test were used to investigate similarity between modern and fossil foraminiferal faunas testing the reliability and significance of our model for paleowater depth reconstruction the performance of the wa pls transfer functions suggests a strong relationship between the observed and estimated water depths in the modern data set with relatively precise reconstructions of 7 0 m root mean squared error of prediction over a water depth range of 3 to 80 m the deepest paleo water depths were reconstructed for the earliest sea level highstands recorded in the sediment records mis 27 and mis 29 in the down faulted boreholes due to tectonic movements whereas the younger interglacial sedimentary units mis 25 13 11 7 5 5 and 1 were mostly deposited at

nuclide production by cosmic rays during the last ice age carbon dating is an extremely important method for determining the age of ancient organic matter the method relies on measurements of radioactive carbon 14 produced by cosmic rays and incorporated into the bodies of animals and plants as bard discusses in his perspective the accuracy of the technique depends on quantifying the production rates of cosmogenic isotopes over time results presented in the same issue by plummer et al shed light on the past history of the important chlorine 36 isotope which in turn offers clues on how the geomagnetic field has influenced cosmic ray production of other isotopes

hypersaline benthic foraminifera from the shuaiba lagoon eastern red sea saudi arabia their environmental controls and usefulness in sea level reconstruction abstract the shuaiba lagoon is a fossil back reef hypersaline small basin located 80 km south of jeddah city on the eastern red sea coast saudi arabia the surface sediments of the lagoon were investigated for their benthic foraminiferal content in order to correlate in general with environmental factors such as temperature salinity ph sediment grain size organic matter and in particular with tidal elevations to develop a training set for predicting sea level changes in the lagoon hierarchical cluster analysis divided the benthic foraminifera in the shuaiba lagoon into four distinct faunal assemblages quinqueloculina cf q limbata assemblage 1 and monalysidium acicularis assemblage 2 assemblages dominated the intertidal high subtidal areas 0 3 to 0 5 m lat the peneroplis planatus sorites orbiculus assemblage 3 occurred abundantly at all subtidal elevations 0 to 1 m lat whereas the quinqueloculina costata spiroloculina communis elphidium striatopunctatum assemblage 4 dominated the lowest elevations

the effect of dauphine twinning on plastic strain in quartz we present an electron backscatter diffraction analysis of five quartz porphyroclasts in a greenschist facies t 300 400 c granitoid protomylonite from the arolla unit of the nw alps mechanical dauphine twinning developed pervasively during the incipient stage of deformation within two porphyroclasts oriented with a negative rhomb plane z almost orthogonal to the compression direction z twin orientation twinning was driven by the anisotropy in the elastic compliance of quartz and resulted in the alignment of the poles of the planes of the more compliant positive rhomb r nearly parallel to the compression direction r twin orientation in contrast we report the lack of twinning in two porphyroclasts already oriented with one of the r planes orthogonal to the compression direction one twinned porphyroclast has been investigated with more detail it shows the localization of much of the plastic strain into discrete r twins as a consequence of the higher amount of elastic strain energy stored by r twins in comparison to z twins the presence of dauphine twins induced a switch in the dominant active slip systems during plastic deformation from basal regions without twinning to and pervasively twinned regions dynamic recrystallization is localized along an r twin and occurred dominantly by progressive subgrain rotation with a local component of bulging recrystallization part of the recrystallized grains underwent rigid body rotation approximately about the bulk vorticity axis which accounts for the development of large misorientation angles the recrystallized grain size piezometer for quartz yields differential stress of 100 mpa the comparison of this palaeostress estimate with literature data suggests that mechanical dauphine twinning could have a potential use as palaeopiezometer in quartz bearing rocks

late holocene relative sea level changes and the earthquake deformation cycle around upper cook inlet alaska abstract multiple peat silt couplets preserved in tidal marsh sediment sequences suggest that numerous great plate boundary earthquakes caused the coast around cook inlet alaska to subside over the past 3500 years field and laboratory analyses of the two youngest couplets record the well documented earthquake of ad 1964 and the penultimate one approximately 850 cal yr bp diatom assemblages from a range of modern day estuarine environments from tidal flat through salt marsh to acidic bog produce quantitative diatom transfer function models for elevation reconstructions based on fossil samples only nine out of 124 fossil assemblages analysed including previously published data for the ad 1964 earthquake have a poor modern analogue calibration of fossil samples indicate co seismic subsidence of 1 50 0 32 m for ad 1964 similar to measurements taken after the earthquake and 1 45 0 34 m for the 850 cal yr bp earthquake elevation standard errors for individual fossil samples range from 0 08 m in peat layers to 0 35 m in silt units lack of a chronology within fossil silt units prevents identification of changes in the rate of recovery and land uplift between the post seismic and inter seismic periods however preservation of multiple peat silt couplets indicates no net emergence over multiple earthquake cycles glacio isostatic movements from little ice age glacier advance and retreat explains a 0 15 m relative sea level oscillation recorded within the peat layer subsequently submerged as a result of the ad 1964 earthquake before both this and the 850 cal yr bp earthquake diatom assemblages suggest pre seismic relative sea level rise of 0 12 0 13 m representing possible precursors to great earthquakes

microcracks in ultrabasic rocks under uniaxial compressive stress the initiation and propagation of microcracks under stress are highly dependent upon the mineralogical and textural characteristics of the various lithotypes detailed observation and quantification of microcracks before and after uniaxial compression test were conducted a fresh olivine rich harzburgite and a serpentinized dunite were analyzed collected from the pindos and vourinos ophiolites northern greece respectively in order to compare their microcrack patterns quantitative analysis indicated that during uniaxial compression the intragranular microcracks which are the dominating crack type are gradually transformed or organized into transgranular cracks some of the newly formed transgranular cracks may also be a result of the growth of existing grain boundary cracks the new intragranular microcracks in the olivine rich harzburgite are oriented predominantly parallel to the compressive stress direction while those in the serpentinized dunite show a scattered orientation presumably due to the mesh texture of this rock type the new transgranular cracks of both peridotites tend to be subparallel to the compressive stress direction however many of them show a random orientation due to the fact that they have been formed as a result of the propagation of grain boundary cracks the occurrence of the soft serpentine along fracture surfaces of olivine when it is in assemblage with orthopyroxene tends to absorb the applied stress hampering the development of microcracks in olivine on the other hand in serpentinized peridotites the microcracks are enhanced in olivine because it is surrounded by large amounts of the much softer and flexible serpentine microcracks are usually formed along the cleavage planes of orthopyroxene porphyroclasts indicating that such crystallographic preferred orientations act as planes of weakness controlling the direction of the crack paths cr spinel grains likely comprise locations of initiation of microcracks due to their very hard nature and different mechanical behaviour relative to the surrounding silicate phases knowledge of the mineralogical and textural characteristics may assist in the prediction of potential development of failure surfaces of an ultrabasic rock in service

suitability of salt marsh foraminifera as proxy indicators of sea level in tasmania this paper aims to establish whether contemporary salt marsh foraminifera from eastern tasmania are suitably related to elevation and can therefore be used to reconstruct past sea levels a proxy reconstruction of recent sea level change in tasmania is potentially useful because in new zealand a prominent early 20th century acceleration of sea level rise has been documented which requires regional confirmation forty three surface samples were collected from two salt marshes in the little swanport estuary common species are trochammina inflata jadammina macrescens miliammina fusca trochamminita irregularis and trochamminita salsa the latter two species have been previously grouped together as t salsa but are distinguished here because they occupy distinct vertical niches we performed regression analyses on the agglutinated foraminifera and their surface elevations using the software package c 2 and tested the accuracy of various regression models by comparing predicted heights of the two transects with surveyed heights we found that the surveyed heights are closely matched by elevations predicted by weighted average partial least squares wa pls models these models predict sea level to within 0 10 m pls models showed favourable statistical parameters but were unreliable when used for predictions applications of pls regression models in sea level reconstructions therefore require caution we compare our results with other studies from around the world and conclude that microtidal coastlines provide the most advantageous conditions for precise sea level reconstructions

microcracks in rocks a review abstract in the past decade the number of studies about microcracks in rocks has rapidly increased this review of recent work concentrates on microcracks in rock as separate entities emphasizing microcrack morphogenesis kinematics dynamics population statistics and observational techniques cracks are produced when the local stress exceeds the local strength the local stress may be augmented by twin lamellae interactions kink bands and deformation lamellae stress concentrations at grain boundary contacts and around intracrystalline cavities local strength may be reduced along cleavage planes along grain boundaries and along any internal surface as a result of corrosion by chemically active fluids dislocations appear not to be a significant factor for crack nucleation below about 500 c in silicates spatial and temporal changes in temperature can also induce microcracking as a result of differential thermal expansion between grains with different thermoelastic moduli and thermal conductivities the amount of quartz in the rock has a significant effect on thermally induced microcracks because of its large and variable thermal expansivity the application of hydrostatic pressure between 100 and 200 mpa effectively closes most cracks but the closure may not be uniform if crack wall asperities exist hydrostatic pressure appears to stabilize cracks and make crack growth more difficult the number and average size of mechanically induced microcracks is greater in rock deformed at higher pressures the application of a deviatoric stress field on the boundaries of a rock mass results on a microscopic scale in a very complex stress system which greatly affects nucleation and propagation paths the relative amount of intragranular and intergranular cracking appears to depend upon mineralogy rock type and stress state the vast majority of stress induced microcracks in rocks appear to be extensional statistically they are predominantly oriented within 30 of the macroscopic maximum stress direction crack densities increase as macroscopic deviatoric stress increases above a threshold level crack size distributions may be either lognormal or exponential fracture in rock under compressive boundary loads is a result of the coalescence of many microcracks not the growth of a single crack some crack configurations are more favorable for coalescence than others as deviatoric stress increases and rock failure is approached the microcrack population changes spatially from random to locally intense zones of cracking away from the fault the crack density dies off rapidly to the background level a few grains away under lesser deviatoric stresses slow subcritical microcrack growth can occur as a result of stress aided corrosion at the crack tip the rate governing mechanism may be either the chemical reaction rate or the rate at which water can get to the crack tip important details still remain to be worked out

using foraminiferal transfer functions to produce high resolution sea level records from salt marsh deposits maine usa quantitative analyses of foraminiferal distributions along the coast of maine are used to provide transfer functions for reconstruction of sea level changes from fossil foraminiferal assemblages the indicative meaning of fossil assemblages is most accurately predicted by a training set that incorporates live and dead foraminifera and that uses flooding duration not height as the predictor variable sea level records are produced for two sites in maine usa a middle marsh site in scarboro and a high marsh site in machiasport these records offer temporal resolution of five to seven years and span the past century they are compared with instrumental data from a nearby tidal station to assess their accuracy strong correlations are found between the geologic records and the observational data in particular between the foraminiferal record from machiasport and the tide gauge record from eastport r2 0 83 p 0 005 thus a foraminifera based transfer function approach offers great potential for reso