texture development in deformed granodiorites from the santa rosa mylonite zone southern california abstract we report on texture development of granodiorite which has been progressively deformed to mylonite and phyllonite in the santa rosa mylonite zone in southern california since it is extremely difficult to measure pole figures of materials with complex diffraction patterns it was necessary to use sophisticated neutron diffraction techniques with high resolution and position sensitive detectors which enable the mathematical deconvolution of at least part of the spectrum we could construct separate pole figures for biotite quartz and plagioclase which are the major components in the granodiorite protolith the preferred orientations of all phases are weak in the mylonite biotite and quartz develop strong preferred orientations whereas feldspars remain randomly oriented quartz has c axes in the intermediate strain axis as is common in other mylonites interestingly biotite a axes show preferred orientation suggesting that slip may be involved rather than just rigid body rotation in phyllonite with a grain size of about 50 m the biotite fabric is very strong however the quartz fabric has largely vanished perhaps by superplastic processes which do not produce texture a weak plagioclase fabric has developed

a new late holocene sea level record from the mississippi delta evidence for a climate sea level connection abstract a detailed relative sea level rsl record was constructed for the time interval 600 1600 ad using basal peat to track sea level and containing 16 sea level index points that capture 60 cm of rsl rise the study area is in the mississippi delta where the spring tidal range is 0 47 m the impact of ocean currents on sea surface topography is limited and crustal motions are well constrained age control was obtained by ams 14 c dating and most ages represent weighted means of two subsamples sample elevations were determined by combining differential gps measurements with optical surveying all index points were plotted as error boxes using 2 confidence intervals for the ages plus all vertical errors involved in sampling and surveying as well as the indicative range of the samples a striking clustering of sea level index points between 1000 and 1200 ad suggests a possible acceleration in the rate of rsl rise removal of the long term trend 0 60 mm yr 1 allows for the possibility of a sea level oscillation with a maximum amplitude of 55 cm however given the size of the error boxes the possibility that oscillations did not occur cannot be entirely ruled out comparison of the new rsl record with various proxy climate records suggests that sea level in this area may have responded to hemispheric temperature changes including the medieval warm period and the little ice age however given the error margins associated with this reconstruction it is stressed that this causal mechanism is tentative and requires corroboration by high resolution sea level reconstructions elsewhere

late pleistocene and holocene palaeogeography of the lower tagus valley portugal effects of relative sea level valley morphology and sediment supply abstract because of the deep glacial incision the lower tagus valley hosts a sedimentary record since 20 000 cal bp making this a unique site along the european atlantic margin with respect to palaeogeographic and sea level changes based on nine cross sections and 55 radiocarbon dates together with a newly created relative sea level curve we constructed five palaeogeographic maps of the infill of the lower tagus valley since 20 000 cal bp we illustrate that relative sea level rise and fluvial sediment supply were the prime forcing factors determining the depositional history and palaeogeographic changes around 20 000 cal bp a deeply incised braided river existed which was directly connected to the ocean across the narrow continental shelf after that 12 000 cal bp the gradually moister and warmer climate caused a change to a single channel river during the following period 12 000 7000 cal bp relative sea level rise resulted in a transgression in the lower tagus valley and the establishment of extensive tidal environments after relative sea level rise had ended 7000 cal bp the valley was progressively filled by a fluvial wedge and tidally influenced bayhead delta since 1000 cal bp the valley fill history was dominated by increased sediment input due to human induced degradation of catchment slopes generally climate was of subordinate importance during the entire studied period merely causing a single channel river resulting from the change from the cold heinrich event 1 to the temperate bolling allerod interstadial despite the tectonic activity in the region neotectonic uplift or subsidence was limited as supported by the horizontal relative sea level curve since 7000 cal bp neotectonics played a minor role due to the large distance from the fennoscandian ice sheet and the narrow continental shelf which prohibited strong glacio and hydro isostatic movements

near field sea level variability in northwest europe and ice sheet stability during the last interglacial global sea level during the last interglacial lig marine isotope sub stage 5e peaked between c 5 5 and 9 m above present implying significant melt from greenland and antarctica relative sea level rsl observations from several far and intermediate field sites suggest abrupt fluctuations or jumps in rsl during the lig highstand that require one or more episodes of ice sheet collapse and regrowth such events should be manifest as unique sea level fingerprints recorded in far intermediate and near field sites depending on the source s of ice mass change involved to date though no coherent evidence of such fluctuations has been reported from near field rsl studies in northwest europe this is an important problem because rsl fluctuations during the lig are portrayed as warning signs for how polar ice sheets may behave in a future warmer than present world here we review the evidence for rsl change during the lig using stratigraphic data from the best resolved highstand records that exist in the near field of northwest europe from a range of settings that include lagoonal shallow marine tidal flat salt marsh and brackish water fluviatile environments consideration of previously published stratigraphic records from two sites in the eemian coastal marine embayment that existed in the central netherlands yields no clear indications for abrupt rsl change during the attainment of the near field highstand nor do we find any such indications common to other records from countries bordering the north sea the baltic sea and the white sea two modelling experiments that explore the global signal of hypothetical sea level oscillations caused by partial collapse and regrowth of either the greenland or antarctic lig ice sheet show that the north sea region is relatively insensitive to mass changes sourced from greenland but should clearly register events with an antarctic origin especially those that occur late in the lig the lack of evidence for abrupt sea level fluctuations at this time in northwest europe concurs with a lack of clear near field evidence for ice sheet collapse

correlation between magnetic fabrics strain and biotite microstructure with increasing mylonitisation in the pretectonic wyangala granite australia abstract the wyangala granite is a foliated porphyritic silurian granite from the palaeozoic circum pacific type eastern lachlan orogen elo of australia it is a paramagnetic ilmenite bearing s marginal i type two mica to mainly biotite granite with different biotite contents and local chlorite alteration very highly strained quartz epidote bands are present in this contribution anisotropy of magnetic susceptibility ams is compared with independently measured intensity and 3d style of strain biotite microstructure and degree of mylonitisation for low strain granites with weak s foliations through medium strain protomylonitic granites with moderate s and c foliations to a high strain altered granite with a strong single foliation the samples are further analysed for possible contributions from sample heterogeneity magmatic flow and sub magmatic deformation a good correlation p ams 1 02 0 04 ln p e qtz is obtained between site average degree of ams p ams in the granite and degree of finite strain anisotropy p e qtz from aspect ratios of quartz aggregates in s foliations in hand specimen and outcrop p ams 1 03 1 14 p e qtz 1 4 19 the magnetic fabric ellipsoids agree with a kinematic regime between neutral and pure oblate predicted by the march model the observed quartz strains however exceed the ams march strains and are near neutral plano linear character the geological factors that may have contributed to these differences include intra and inter crystalline deformation of biotite and bimodality in s and c magmatic fabric is not clearly evident in either the ams or the biotite data new data for synkinematic oligoclase low titanium biotite and low sodium k feldspar show that conditions during deformation were approximately transitional greenschist amphibolite facies i e well below solidus this agrees with published age data that put the granite emplacement in an extensional back arc setting in already deformed country rocks and before later convergent regional deformation in middle devonian tabberabberan event to early carboniferous kanimblan event time

magnetic susceptibility of the rock matrix related to magnetic fabric studies non ferromagnetic minerals constitute what is called the rock matrix whose susceptibility k1 is directly accessible using only high magnetic fields measurements on minerals and a wide range of rock types show that k1 is mainly due to paramagnetism and hardly exceeds 10 3 si with an anisotropy degree p less than 1 35 different methods to estimate the role of the matrix component in low field susceptibility k and its anisotropy include petrological and chemical analysis evolution of p vs k low temperature studies and comparison of k with remanent magnetizations

holocene excursions of the northwest european geoid abstract computer assisted analyses of more than 600 radiocarbon dated sea level indicators from northwestern europe concentrated around the north sea margin indicate that vertical crustal movements are more important that eustatic sea level change in determining the locus of holocene shoreline positions through time for the past 14 000 radiocarbon years the divergence of sea level data for the northwest european sectors exceeds the maximum estimated sea level rise by a factor of two or more projecting these data to a single meridian demonstrates the remarkable variety of vertical crustal movement in northwestern europe accumulating radiocarbon dated sea level indicators into millennial cohorts we generate isobase maps which begin to specify areas of notable vertical crustal mobility these isobase maps appear to confirm that eustatic sea level rise is subordinate to postglacial geoidal excursions in determining the locus of contemporary northwestern european shorelines

the anisotropy of magnetic susceptibility in biotite muscovite and chlorite single crystals the anisotropy of magnetic susceptibility ams of single crystals of biotite muscovite and chlorite has been measured in order to provide accurate values of the magnetic anisotropy properties for these common rock forming minerals the low field ams and the high field paramagnetic susceptibility are defined for the high field values it is necessary to combine the paramagnetic deviatoric tensor obtained from the high field torque magnetometer with the paramagnetic bulk susceptibility measured from magnetization curves of the crystals this leads to the full paramagnetic susceptibility ellipsoid due to the anisotropic distribution of iron cations in the silicate lattice the ellipsoid of paramagnetic susceptibility which was obtained for the three phyllosilicates is highly oblate in shape and the minimum susceptibility direction is subparallel to the crystallographic c axes the anisotropy of the susceptibility within the basal plane of the biotite has been evaluated and found to be isotropic within the accuracy of the instrumental measurements the degree of anisotropy of biotite and chlorite is compatible with previously reported values while for muscovite is smaller than previously published values the shape of the chlorite ams ellipsoid for all the samples is near perfect oblate in contrast with a wide distribution of oblate and prolate values reported in earlier studies reliable values are important for deriving models of the magnetic anisotropy where it reflects mineral fabrics and deformation of rocks d 2003 elsevier science b v all rights reserved

deciphering holocene sea level history on the u s gulf coast a high resolution record from the mississippi delta published holocene relative sea level rsl curves for the u s gulf coast are in mutual conflict with some characterized by a smooth rsl rise akin to widely accepted eustatic sea level curves versus others including several recent ones that are characterized by a conspicuous stair step pattern with prolonged millennium scale rsl stillstands alternating with rapid meter scale rises in addition recent work in texas and alabama has revitalized the notion of a middle holocene rsl highstand estimated at 2 m above present mean sea level an extensive sampling program in the mississippi delta louisiana focused on the collection of basal peats that accumulated during the initial transgression of the pre existing consolidated pleistocene basement we used stable carbon isotope ratios to demonstrate that many of these samples accumulated in environments affected by frequent saltwater intrusion in the 30 cm zone between mean spring high water and mean sea level and we selected plant macrofossils that were subjected to ams 14c dating nearly 30 sea level index points from a 20 km2 study area on the eastern margin of the delta suggest that rsl rise followed a relatively smooth trend for the time interval 8000 3000 cal yr b p thus questioning the occurrence of major rsl stillstands alternating with abrupt rises given the narrow error envelope defined by our data set any sea level fluctuations if present would have amplitudes of 1 m although a true middle holocene highstand never occurred in the mississippi delta the high level of detail of our time series enables a rigorous test of this hypothesis correction of our data set for a hypothetical tectonic subsidence rate of 1 1 mm yr 1 assuming a constant subsidence rate compared to the tectonically relatively stable adjacent coast of texas leads to sea levels near 2 m above present during the time interval 6000 4000 cal yr b p however this model also implies a rsl position near 2 m around 8000 cal yr b p which is inconsistent both with data of this age from texas as well as with widely accepted sea level data from elsewhere we therefore conclude that a middle holocene highstand for the u s gulf coast is highly unlikely and that the entire area is still responding glacio isostatically by means of forebulge collapse to the melting of the laurentide ice sheet

quantitative correlation of texture and magnetic anisotropy of compacted calcite muscovite aggregates abstract deformation of carbonate rocks leads to crystallographic preferred orientations cpos of calcite which in turn generates an anisotropy of magnetic susceptibility ams the use of the diamagnetic anisotropy which arises from the preferential orientation of calcite for texture characterization is usually hindered by 1 the weakness of the anisotropy and 2 overlapping contributions from paramagnetic and ferromagnetic minerals to the ams in this study the diamagnetic paramagnetic and ferromagnetic sub fabrics of synthetic calcite muscovite samples have been separated using high field torque measurements the cpo of calcite and muscovite has been determined by neutron diffraction and the magnetic sub fabrics are compared to the ams that was re calculated from the cpo the isolated diamagnetic sub fabric shows a good correlation with the calcite texture for calcite concentrations above 70 the paramagnetic sub fabric is shown to be a reliable texture parameter for muscovite even at a concentration of 5 the results demonstrate the capability of the ams method as a texture parameter in impure carbonate rocks

book review preferred orientation in deformed metals and rocks an introduction to modern texture analysis han rudolf wenk editor academic press inc new york 1985 xix 610 pp 50 50 59 50 hardback

holocene crustal movements and sea level changes in great britain crustal downwarping has occurred throughout southern and south eastern england and most of wales for at least the last 4000 years but the type of movement in some areas of southern and eastern england is more complicated than simple linear subsidence highest estimated rates of subsidence since 4000 bp are for the thames estuary and norfolk up to 2 mm yr glacio isostatic processes have resulted in uplift in northern england and mainland scotland the rates of uplift have decreased throughout the holocene estimates for the present range from zero in south lancashire and the tees estuary to over 1 mm yr though less than 2 mm yr in central scotland over 400 sea level index points from the databank of 904 cases collected for igcp project 200 are grouped into 15 main areas and used to investigate the nature of crustal movements in great britain since 8800 bp but there are significant deficiencies in available data which constrain the analysis

radiocarbon dated sediment sequences from the belgian coastal plain testing the hypothesis of fluctuating or smooth late holocene relative sea level rise the late holocene deposits of the coastal lowlands bordering the southern north sea were formed by a renewed expansion of the tidal environment replacing freshwater peats the sea level history during the last 2500 years inferred from the post peat deposits containing little to no datable organic material is characterized by two conflicting schools of thought the first one supports a smooth sea level curve the second approach underpins fluctuating sea level changes the fluctuating approach also uses facies variations recorded in the post peat deposits to provide a chronostratigraphical subdivision linked to transgressions and regressions this paper examines the controlling factors responsible for the facies variations in the post peat deposits in order to test the approach of the fluctuating sea level the results of sedimentological investigation coupled with radiocarbon dates of intertidal shells from four shallow outcrops located in nearby sand filled late holocene tidal channels in the belgian

holocene relative mean sea level changes in the wadden sea area northern netherlands although the netherlands has a long tradition of sea level research no holocene relative sea level curve is available for the north of the netherlands previous studies hypothesised that the relative sea level reconstruction for the western netherlands is also valid for the northern part of the country however glacial isostatic adjustment gia models predict a lower and steeper relative sea level curve because of greater postglacial isostatic subsidence long term data of relative sea level change are important to inform gia models and understand postglacial vertical land motion related to the rebound of fennoscandia and neotectonic activity we compiled and evaluated a set of basal peat radiocarbon dates to reconstruct the holocene relative mean sea level rise in the dutch wadden sea area for the early holocene this reconstruction is lower than the western netherlands curve after 6400 cal a bp the curve for the wadden sea is statistically indistinguishable from that for the western netherlands a result that conflicts with gia model results it remains to be investigated whether the problem lies with the gia model predictions or with the quality of the available data additional basal peat radiocarbon dates from suitable sites should be collected to further solve this problem

the melting history of the late pleistocene antarctic ice sheet spatial and temporal variations in the sea levels of the past 20 000 years around the globe place constraints on the melting history of the major late pleistocene ice sheets the antarctic ice sheets provided a significant contribution to the sea level rise at a rate that was approximately synchronous with the melting of the laurentide ice sheet except for the interval 9 000 6 000 years ago when it may have lagged behind minor melting of the antarctic ice sheet continued throughout the holocene

crystallographic preferred orientation magnetic and seismic anisotropy in rocks from the finero peridotite ivrea verbano zone northern italy interplay of anisotropy contributions from different minerals abstract mineral alignment can provide valuable information on a rock s geological history many structural tectonic or geodynamic studies rely on determining the preferred orientation of rock forming minerals either by direct texture determination or using anisotropy measurements as proxies robust interpretations of anisotropy require detailed understanding of its relationship with texture this study investigates the texture magnetic and seismic anisotropies of ultramafic rocks from the ivrea verbano zone ivz northern italy with a special focus on the interplay between anisotropy contributions carried by different minerals texture was obtained from electron backscatter diffraction magnetic anisotropy from low and high field anisotropy of susceptibility measurements and seismic anisotropy from p and s wave velocities along the three principal directions of the macroscopic fabric using 22 mm diameter cores texture based models of magnetic anisotropy agree well with corresponding measurements larger variability is observed for seismic anisotropy possible explanations are 1 velocities were measured in three directions insufficient to determine the full elasticity tensor and 2 seismic anisotropy depends on grain boundaries pores and cracks in addition to crystallographic preferred orientation the contributions to magnetic and seismic anisotropy of each constituent mineral can interfere positively leading to a larger overall anisotropy or negatively resulting in a weaker anisotropy seismic anisotropy is mostly controlled by olivine whereas magnetic anisotropy can be dominated by olivine pyroxene or hornblende this study illustrates that although the relationship between texture and anisotropy can be complex it is possible to quantitatively predict magnetic and to a lesser degree seismic anisotropy from texture data even though both magnetic and seismic anisotropies are common proxies for texture they are not coaxial and no simple relationship between the degree of magnetic and seismic anisotropy was found these results underline the importance of understanding different minerals contributions to anisotropy in upper mantle rocks

characterization of the magnetic fabric of rocks abstract an inextensive system of magnetic susceptibility anisotropy factors is suggested which is sufficient in the majority of practical applications for characterizing the magnetic fabric of rocks the system involves three newly devised factors the corrected anisotropy degree the shape factor and the difference shape factor the first of these characterizes the quantity of anisotropy somewhat better than the commonly used anisotropy degree the shape factor characterizes the quality of anisotropy i e the shape of the susceptibility ellipsoid in a convenient way its definition is based on a certain analogy between the anisotropy ellipsoid and the strain ellipsoid the difference shape factor can replace the shape factor when only the differences between the principal susceptibilities are given while the mean susceptibility is unknown

fabric changes and their influence on p wave velocity patterns examples from a polyphase deformed orthogneiss abstract the complete p wave velocity distribution preferred orientation of rock forming minerals and microcracks of two differently deformed orthogneisses from the kutna hora crystalline unit were investigated the complete symmetry of p wave velocities were determined as a function of confining pressure on the basis of 132 independent propagation directions up to 400 mpa the two samples are of almost identical mineralogical composition but exhibit different fabrics which can be related to different positions within a large scale fold structure the symmetry of the vp diagrams change from nearly transversely isotropic for the sample from the limb area to orthorhombic for the sample from the hinge zone which shows an additional crenulation cleavage this change of symmetry is observed at all pressure levels reorientation of the main velocity directions vpmin vpmax kpint between hinge and limb is controlled by the microcrack fabric and the texture of the rock forming minerals this can cause significant differences in reflectivity related to fabric changes within large scale folds

reconstruction of holocene relative sea level change and residual uplift in the lake inba area japan abstract we collected and analyzed fossil diatoms and volcanic ash and determined 14 c ages in core samples from the lowlands around lake inba in the eastern kanto plain central japan an area where late quaternary sea level change fluvial erosion and tectonic uplift have affected a region of archeological interest we inferred holocene paleoenvironmental changes and relative sea levels on the basis of indicators such as high tide levels derived from fossil diatom assemblages as well as the stratigraphic positions of 14 c dated samples and the k ah tephra our results lead to estimates of the upper half tidal range during 6800 7000 cal yr bp of 1 7 m the holocene highstand took place at approximately 6400 6500 cal yr bp and mean sea level reached an elevation of 1 9 m however the timing of this sea level rise is earlier in the lake inba area than documented in previous studies and it is suggested that the timing of the holocene highstand may appear at least 1000 years earlier as a result of holocene residual uplift after this sea level fell abruptly around 4000 cal yr bp we also recognized a sea level fall corresponding to the yayoi regression at about 2600 cal yr bp during which the mean relative sea level may have been as low as 2 5 m after compensating for uplift subsidence or geomorphologic effects in this area

on the reliability of ams in ilmenite type granites an insight from the marimanha pluton central pyrenees this study has been financed by the research project cgl2009 08969 spanish ministry of science and innovation bou acknowledges financial support from the geotransfer group university of zaragoza dga and the jaedoc postdoctoral program csic reviews from d bilardello b almquist and editor e appel are warmly acknowledged for their help to improve the manuscript info eu repo grantagreement ec fp7

holocene relative sea level change and crustal movement in the southwestern netherlands abstract sea level data collected by jelgersma 1961 from zeeland in the southwestern netherlands show an anomalously high time depth position with respect to sea level curves established for the rest of the netherlands until now it was not clear whether this was related to differential crustal movements a higher tidal range and or to groundwater influenced peat growth above contemporaneous sea level new radiocarbon dates from the base of the basal peat in zeeland and the adjacent estuarine flood plain of the river scheide in belgium have a considerably lower time depth position than the original data of jelgersma 1961 comparison of the lowest mean sea level msl time depth points from the study area with a reference msl error band for the western netherlands yields a maximum crustal uplift of zeeland relative to the western netherlands of about 0 17 m 1000 yr over the last 8000 yrs cal b p a regional msl envelope for the southwestern netherlands has been constructed by correcting the reference msl error band with this maximum rate of relative uplift the new regional maximum msl error band plots significantly below the zeeland curve and the zeeland data points of jelgersma 1961 1966 but is still higher than msl curves established for the rest of the netherlands the remaining vertical distance of the data of jelgersma to the new zeeland msl error band is attributed to early basal peat growth above contemporaneous msl primarily due to a groundwater gradient effect on the gently inclined pleistocene subsoil the sea level index points with the lowest time depth position all come from locations close to or within the late pleistocene palaeovalley of the river scheide this was probably due to the slope of the regional groundwater table towards the palaeovalley resulting in better drainage conditions on the valley sidewalk peat could only develop under the direct influence of the river water level which was controlled by sea level rise this suggests that comparable palaeovalleys on other coastlines of the north sea or elsewhere offer considerable potential for sea level research if the topography of the compaction free substratum is well known

lagoa da apulia a residual lagoon from the late holocene nw coastal zone of portugal the lagoa da apulia is a unique feature in the nw coastal zone of portugal a remaining form from a lagoon complex system that during the late holocene was dominant in the region this system was mainly neotectonically controlled occupying a depressed area bounded by faults on a palaeozoic rocky lower platform today observable on beaches at low tide with the intention of knowing the main architecture of the palaeo lagoon geophysical prospecting with gpr and resistivity was carried out accordingly six cores were taken and the sedimentary and mineralogical facies and diatom and foraminifer contents were analysed and five rich organic layers were dated by radiocarbon analysis with the data an evolutionary environment reconstruction model was created for this palaeo lagoon and the main structural features of the neighbouring area

anisotropy of magnetic susceptibility in diamagnetic limestones reveals deflection of the strain field near the dead sea fault northern israel abstract to exploit the potential of anisotropy of magnetic susceptibility ams as a tool to estimate the strain field around major faults we measured the ams of calcite bearing diamagnetic rocks that crop out next to the dead sea fault dsf in northern israel through integrated magnetic and geochemical methods we found that the rocks are almost pure calcite rocks and therefore the magnetic fabric is primarily controlled by preferred crystallographic orientation pco with the minimum principal ams axes k 3 parallel to calcite c axes we applied a separation procedure in several samples with high fe content in order to calculate the ams anisotropy parameters and compare them to pure diamagnetic rocks aarm thermo susceptibility curves and irm were used to characterize the magnetic phases we found that for fe content below 500 ppm the ams is mostly controlled by the diamagnetic phase and showed that differences in the degree of anisotropy p up to 3 p 1 005 to 1 023 and in anisotropy difference k up to 0 25 10 6 si in diamagnetic rocks are related to differences of strain magnitudes the spatial distribution of the magnetic fabrics indicates n s maximum shortening parallel to the strike of the hula western border fault hwbf one of the main strands of the dsf in northern israel the anisotropy parameters suggest that the strain magnitudes increase eastward with the proximity to the hwbf these results suggest that the strain field near the hwbf is locally deflected as a consequence of the dsf activity in light of the fault weakness model and geological setting of the study area we suggest that the area accommodates dominant transtension during the pleistocene the present study demonstrates the useful application of ams measurements in iron free limestones as recorders of the strain field near plate boundaries

driving mechanisms of coastal change peat compaction and the destruction of late holocene coastal wetlands abstract this paper examines the role of peat compaction as a driving mechanism behind the widespread inundation of a late holocene coastal wetland in southeast england uk detailed stratigraphic and dating evidence lithology grain size foraminifera pollen and radiocarbon dates from a sample site in romney marsh documents the gradual inundation of a coastal wetland after 1263 1085 cal yr bp c 700 850 ad and the establishment of a saltmarsh shortly thereafter there was a rapid increase in water depth that was associated with the deposition of nearly 4 m of laminated intertidal mudflat and tidal channel sediments prior to site reclamation from the sea by ad 1460 grain size data and statistical analysis of sand and mud laminae thicknesses suggest the laminated sediments accumulated rapidly c 0 2 m per year as heterolithic tidal rhythmites rapid compaction of the thick peat bed that underlies the study site provided the accommodation space for their deposition this process began with the gradual tidal inundation of the site but accelerated following the widening of a breach in a coastal barrier in the 13th century compaction lowered the peat surface by at least 3 m and was associated with widespread landscape change the study demonstrates the powerful influence that compaction had on the evolution of the late holocene landscape at this site and we believe at many other coastal lowlands in northwest europe this process is likely to have been a key driving mechanism behind rapid late holocene coastal change far exceeding the longer term effects of either eustatic change or crustal uplift subsidence

insect evidence for environmental and climate changes from younger dryas to sub boreal in a river floodplain at st momelin st omer basin northern france coleoptera and trichoptera the st omer area is a rapidly subsiding basin in which long sequences of weichselian and holocene sediments are preserved a core 21 m long extracted from near st momelin about ten km north of st omer has been analysed for insect fossils four faunal units smi 1 to smi 4 are described based on changes in both coleopteran and trichopteran assemblages the basal faunal unit smi 1 includes many cold adapted species and is attributed to the younger dryas chronozone the transition to holocene sedimentation was abrupt faunal units smi 2 to smi 4 are attributable to the holocene they lack all the cold adapted species found in the basal sediments and in their place are insect assemblages very similar to the present day fauna in this region this sequence spans the period from the pre boreal to the sub boreal faunal unit smi 2 includes insects from the pre boreal the boreal and most of the atlantic periods this fauna was fairly sparse and made up largely of species living in freshwater habitats the faunal unit smi 3 includes the insect assemblages from the late atlantic to sub boreal periods this fauna was much more diverse and indicated a river meandering across its floodplain and bordered by a mature forest at a time when the climate was warmer than that of the present day this chronostratigraphical sequence of events is supported by 14c dates and by lithological data thermal climatic conditions have been quantified using the mutual climatic range method during the younger dryas period smi 1 tmax the mean july temperature was in the region of 10 c and tmin the mean temperature of january february was close to 11 12 c after the sudden climatic amelioration at the start of the holocene smi 2 to smi 4 tmax probably fluctuated throughout the early holocene between 16 c to 19 c and tmin between 0 c to 5 c figures that are close to those of the present day this climatic history is compared with others in northern europe

control of magnetic rock fabrics by mica preferred orientation a quantitative approach magnetic anisotropy analysis represents a well established and frequently used method in structural geology several attempts were made to relate the anisotropy of magnetic susceptibility ams to rock fabrics and to discover the sources of the ams in gneissic rocks paramagnetic phyllosilicates with lattice dependent magnetic properties are assumed to control the whole rock ams i e it is dominated by mica lattice preferred orientation texture in this study ams was modelled on the basis of the mica texture the rock composition and compared to the experimentally determined ams the orientations of the modelled and experimental tensors agree quite well whereas all the other characteristic parameters shape anisotropy mean susceptibility display large differences it has been concluded that accessory high susceptible phases as well as the diamagnetic rock constituents may have significant influence on ams consequently mica pole figure measurements cannot be replaced by ams measurements without control of the sources of ams it was also concluded that the march model to evaluate strain from mica preferred orientations is not valid for highly strained rocks beside the fact that the obtained strains are too low the deformation is generally inhomogeneous which leads to an overprint of the mica texture since the microstructural fabric elements which originate in different strain regimes prolate or oblate may create similar modifications of the mica orientation patterns it is obvious that the relationship between ams and deformation is rather complex

geoarchaeological records in temperate european river valleys quantifying the resource assessing its potential and managing its future throughout the quaternary episodes of glaciation and associated low sea level have resulted in the connection of the terrestrial landmasses of britain and mainland europe the river systems that established themselves across these newly emergent land surfaces of the coastal plain would have created important migration corridors for both animals and humans a point corroborated by the affinity of palaeolithic remains across britain and europe technological developments within the last decade have allowed these now submerged valley floors and adjacent terrestrial landscapes associated with the last cold stage and early and middle parts of the current holocene interglacial to be explored and their archaeological legacies unravelled providing geoarchaeologists with an opportunity to contribute to major cultural debates however in order to maximize knowledge it is essential that geoarchaeologists working within river valleys across both britain and the european continent are addressing similar research questions by collecting data using comparable methodologies this paper reviews the approach taken in different regions and provides a baseline assessment to allow the development of a coherent european wide framework for alluvial geoarchaeology and geoprospection particularly with respect to the holocene record

sequence mapping of holocene coastal lowlands the application of the streif classification system in the belgian coastal plain a geological map of the holocene deposits of a portion of the western belgian coastal plain is presented the map differs from a conventional geological map which is of little use for coastal lowlands because of the high lateral and vertical variability in lithology in the subsoil the method of sequence maps was chosen because these maps allow the representation of the entire vertical sequence of the holocene deposits a sequence map is constructed on the basis of profile types consisting of the vertical succession of the various mapping units in order to produce a user friendly map preference was given to lithogenetic units instead of formal lithostratigraphic units for the determination of mapping units the organisation of the mapping units was established according to the streif classification system the application of the system is demonstrated with two different sequence maps each constructed on a different level of the hierarchic system a general sequence map and a special sequence map showing further differentiation

kinematic and metamorphic aspects of cleavage formation in very low grade metamorphic slates abstract fabric studies on first cleavages in very low grade metamorphic slates from the rheinisches schiefergebirge and other very low grade metamorphic fold belts reveal two types of slaty cleavage 1 1 cleavage without syntectonic phyllosilicate recrystallization these are generally crenulation cleavages 2 2 cleavage with syntectonic phyllosilicate recrystallization with increasing syntectonic metamorphism the crenulation fabric is modified by solution of grains along cleavage planes and precipitation of material within the cleavage lamellae with further increase of metamorphism the crenulation fabric is gradually obliterated the finite fabric results from progressive solution crystallization and recrystallization superimposed with bending kinking and internal rotation achieved by slip parallel to the basal planes of phyllosilicates

the high resolution holocene sea level curve for northwest germany global signals local effects or data artefacts a few years ago a new relative sea level curve for northwest germany was constructed for the entire german north sea coast it is characterised by several suspected sea level fluctuations to test this curve for local effects it was broken down into five relative sea level curves representative for five coastal sections the relative sea level curves were corrected for tidal effects and also a rough first correction for compaction was applied the five curves all differ from the original curve and from each other most of the suspected sea level fluctuations in the original curve cannot be supported and are discussed as data artefacts or local effects around ad 800 1000 all curves show stagnation or drop of sea level thus this signal is discussed as of over regional stratigraphic meaning this study is a first step 1 to show that several curves are needed to demonstrate the holocene sea level history of such a big area as the entire german north sea coast and 2 to establish reliable relative sea level curves for the german north sea coast further research is necessary to apply detailed corrections especially with respect to compaction prone data and to improve the individual curves

holocene evolution of a wetland in the lower seine valley marais vernier france estuaries like that of the seine river in nw europe developed in incised fluvial valleys after the last glacial maximum since the 1940s several authors have studied the largest wetland of the seine estuary the marais vernier to understand depositional environments during holocene infilling we reinterpret previous research based on new and published data for example fill thickness and material source to 1 describe facies and depositional environments 2 reconstruct palaeoenvironmental evolution 3 show the influence of local and global forcing on depositional environments before 7000 6000 cal bc terrestrial material was deposited because of catchment erosion related to changes in climate just before 7000 6000 cal bc estuarine material began to be deposited in low lying areas in response to sea level rise while terrestrial material still settled at higher elevations after this but before 5850 5710 cal bc estuarine material areas began to accumulate at both high and low elevations this marked a general flooding of the marais vernier synchronous with that at the seine estuary mouth soon after peat accumulated over a wide area as a response to a local change in accommodation and a worldwide drop in sea level a tidal channel developed to the west of the marais vernier providing minerogenic material after 1130 900 cal bc human influence becomes increasingly clear in the record this record of regional change during the holocene can serve as a reference for further studies in the area

sea level change glacial rebound and mantle viscosity fornorthern europe northwestern europe remains a key region for testing models of glacial isostasy because of the good geological record of crustal response to the glacial unloading since the time of the last glacial maximum models for this rebound and associated sea level change require a detailed knowledge of the ice sheet geometry including the ice thickness through time existing ice sheet reconstructions are strongly model dependent and inversions of sea level data for the mantle response may be a function of the model assumptions thus inverse solutions for the sea level data are sought that include both ice and earth model parameters as unknowns sea level data from fennoscandia the north sea the british isles and the atlantic and english channel coasts have been evaluated and incorporated into the solutions the starting ice sheet for fennoscandia is based on a reconstruction of a model by denton hughes 1981 that is characterized by quasi parabolic cross sections and symmetry about the load centre both global northwestern europe as a whole and regional subsets of the data solutions have been made for earth model parameters and ice height scaling parameters the key results are as follows 1 the response of the upper mantle to the changing ice and water loads is spatially relatively homogenous across scandinavia the north sea and the british isles 2 this response can be adequately modelled by an effective elastic lithosphere of thickness 65 85 km and by an effective upper mantle viscosity from the base of the lithosphere to the 670 km depth seismic discontinuity of about 3 4 1020 pa s the effective lower mantle viscosity is at least an order of magnitude greater 3 the ice thickness over scandinavia at the time of maximum glaciation was only about 2000 m much less than the 3400 m assumed in the denton hughes model 4 the ice profiles are asymmetric about the centre of the ice sheet with those over the western part being consistent with quasi parabolic functions whereas the ice heights over the eastern and southern regions increase much more slowly with distance inwards from the ice margin

changes in coastal zone processes at a high sea level stand a late holocene example from belgium this paper presents the results of an investigation of late holocene deposits on the belgian coastal plain the upper clastic deposits overlying the uppermost intercalated peat bed were studied on the basis of lithology radiocarbon dates and foraminiferal assemblages to determine why silting up phases or peat beds are lacking and to establish the evolution of the sedimentary environments as well as the age of the deposits two contrasting sites in quite different locations and showing a different stratigraphy were studied it appears that the coastal evolution was not gradual and continuous but characterised by short periods with high energy conditions alternating with long periods where low energy conditions and little sedimentation prevailed the evolution is determined mainly by tidal channel activity at about 3400 cal yr bp the peat was eroded in narrow zones by the main tidal channels and this until the landward limit of the plain the peat was only partly flooded and mudflats fringed the channels with time new tributaries formed and the channel network progressively enlarged the channels were rapidly filled followed by a period of little sedimentation which lasted at least until 1400 1200 cal yr bp the following channel activity is characterised by lateral sedimentation rather than vertical erosion together with increased sediment reworking the mechanisms of coastal change in the late holocene might be similar over the entire plain but the timing of the changes is certainly not copyright 2002 john wiley sons ltd

evolution of the rhone delta plain in the holocene abstract the delta plain of the rhone shows many sandy beach ridges cropping out at the surface we propose here a radiocarbon chronology for the accumulation of the sedimentary bodies and an interpretation of the morphology of the mouth lobes that they form morphologies of the lobes depend on four principal factors 1 the variation of the relative sea level which constitutes the morphogenic base level 2 the fluvial input volume of water discharge and sedimentary input number and position of the mouths 3 marine dynamics volume and direction of the longshore drift dominant wave direction 4 the accommodation space created by the rise of relative sea level along with the paleobathymetry onto which the lobe will prograde immediately in front of the delta and at sea our conclusions are the main holocene paleo delta lobes of ulmet and saint ferreol were contemporaneous being deposited from 4000 to 2000 yr bp however the fluvial style of their downstream channel meandering for ulmet channel and linear for saint ferreol and the lobe morphologies of both channels are contrasted rounded in the case of ulmet and elongated for saint ferreol the role of the accommodation space is confirmed by two recent drillholes traversing the entire holocene succession which reveal a prior stage of sedimentary filling in the case of the saint ferreol lobe thus limiting the accommodation space and favouring a rapid and pointed progradation of this lobe the decoupling between hydrological activity and progradation of lobe indicates the complexity of mechanisms in the large catchment basin of rhone however the high rate of progradation of saint ferreol lobe after 2900 bp is probably a consequence of the increase of human activity after this date the variation of relative sea level remains an important factor controlling the evolution of the rhone delta after 6000 bp the local stabilization of the relative sea level between 4585 bp and 3520 bp played an important role in the triggering of coastal progradation saint ferreol lobe eastern margin rhone delta

magnetic fabrics in the bjerkreim sokndal layered intrusion rogaland southern norway mineral sources and geological significance abstract magnetic anisotropy can provide important information about mineral fabrics and thus magmatic processes particularly when it is known how multiple mineral species contribute to the anisotropy it may also affect the direction of induced or remanent magnetization with important consequences for paleomagnetic studies or the interpretation of magnetic anomalies here we aim at describing the magnetic fabrics in the bjerkreim sokndal layered intrusion and identifying their carriers anisotropies of magnetic susceptibility and remanence were measured on samples covering different geographic locations and stratigraphic units within the bjerkreim sokndal layered intrusion the intrusion is characterized by magmatic layering and has a synform structure with strong foliation on the limbs detailed comparison between magnetic and mineral fabric shows that they are not necessarily coaxial but the minimum susceptibility and minimum anhysteretic remanence are generally normal to the foliation or the magmatic layering the minimum susceptibility and anhysteretic remanence are associated with pyroxene 100 axes and the maximum susceptibility and anhysteretic remanence are sub parallel to the pyroxene 001 axes in layers mcu ivc and mcu ive for which electron backscatter data are available however the paramagnetic anisotropy of pyroxene is too weak to explain the observed anisotropy we propose that the magnetic anisotropy of magnetite free specimens is carried by hemo ilmenite exsolutions within pyroxene in addition to pyroxene itself when present multi domain magnetite dominates both the anisotropy of magnetic susceptibility and anhysteretic remanence due to shape preferred orientation and distribution anisotropy the orientation of the magnetic fabric appears independent of carrier due to their common deformation history but the degree of anisotropy is stronger for magnetite bearing specimens the results of this study will facilitate future structural interpretations and may be used to correct for magnetization deflection

magnetic fabrics crystallographic preferred orientation and strain of progressively metamorphosed pelites in the helvetic zone of the central alps quartenschiefer formation we investigate the relationships between the anisotropy of magnetic susceptibility ams mineral preferred orientation macroscopic structures and finite strain in a section of increasing metamorphism in the helvetic zone of the central alps switzerland the upper triassic quartenschiefer formation an initially hematite bearing red bed sedimentary rock can be traced from unmetamophosed shale to amphibolite facies schists the magnetic fabrics of 805 specimens agree well in orientation with the foliation normal to kmin kmax kint kmin are principal susceptibilities and the mineral stretching lineation parallel kmax in all metamorphic grades the maximum susceptibility axes are in an approximately n s orientation and were acquired during the miocene north directed nappe transport the effects of the tectonic position and the metamorphic grade on the ams ellipsoid suggests that deformation has a stronger influence on its shape than the metamorphic grade the identification and quantification of the sources of magnetic susceptibility was done with 1 a model calculation 2 the high field low field method and 3 low temperature heating curves the ams of low grade samples is dominated by the paramagnetic minerals mainly mica and the ams of higher susceptible medium grade samples by magnetite the paramagnetic dominated magnetic fabrics correlate well with mica 002 lattice preferred orientations obtained from x ray texture goniometry a one to one correlation between march strains and a magnetic parameter mi ln ki kmaxkintkmin is predicted by a numerical model and verified empirically the magnetic fabrics of well characterized samples can thus be used to quantify the degree of mica preferred orientation using relatively simple magnetic anisotropy equipment

mid and late holocene sea level changes in roudsea marsh northwest england a diatom biostratigraphical investigation diatoms vascular vegetation sediment data and water salinity from contemporary intertidal environ ments in roudsea marsh northwest england are used to define altitudinal relationships between diatom assem blages and reference water levels comparison of these data with the high resolution diatom biostratigraphy of a fossil marsh sequence allows identification of fluctuations of relative sea level in the mid and late holo cene two oscillations in relative sea level are recorded a rise in sea level 0 6 m led to the inundation of the site after 6000 bp and was followed by a fall in sea level c 1 m around 4700 bp a second rise in sea level 0 5 m occurred before 2420 bp and was followed by a relatively stable or smaller rise of sea level during the last millennium the use of diatom groups based on marsh altitude was successful

how subsoil morphology and erodibility influence the origin and pattern of late holocene tidal channels case studies from the belgian coastal lowlands abstract this paper aims at a better understanding of the late holocene re entrance of the tidal system in the belgian coastal plain after a 2 3 ka years long period of peat growth the re entrance was associated with the development of deeply incised tidal channels the initial cause of the re entrance still a missing link in the understanding of the late holocene coastal change is investigated by focusing on the specific location of the young tidal channels the research though based in the western belgian coastal plain is relevant to the lowlands of the southern north sea and english channel the investigation combines stratigraphic radiocarbon and sedimentological data together with maps showing the morphology of the pre holocene surface the distribution of the holocene deposits and the erosional surface produced by the late holocene channels it appears that the young channels re occupied the same position as their early and mid holocene predecessors the re entrance of the tidal system began by a removing of the upper part of the older channels which originated from the mainland once the channels were cleaned of sediment tidal waters could re enter and rework the easily erodable sand of the older channels and pleistocene deposits

oblique magmatic structures of two epizonal granite plutons hoggar algeria late orogenic emplacement in a transcurrent orogen abstract two granite plutons in the pan african belt of hoggar algeria are studied using the anisotropy of magnetic susceptibility technique ams at low field together with a study of microstructures the tesnou complex is made of coalescent plutons at the margins of which dextral n s oriented shearing imprints solid state textures in the granite microstructures and low magnetic anisotropy magnitudes indicate a magmatic state weak deformation consistent nw se trending sub horizontal magnetic lineations making an overall oblique pattern with respect to bordering shear faults is attributed to low n s trending dextral shear strain magnitudes

the concept of steady state foliation abstract a steady state foliation is thought of as a foliation with constant orientation and intensity in a rock undergoing steady state flow the problem discussed is whether such straininsensitive foliations exist in rocks and how they might be distinguished from the more familiar strain sensitive foliations steady state foliations would be useful indicators of stress or of strain rate yet misleading if used as indicators of finite strain one requirement for maintenance of steady state foliations is operation of processes that locally weaken grain shape preferred orientation or reduce grain aspect ratios or destroy lithological layering during flow these are the inverses of the processes normally discussed in connection with foliation development many such processes are known though the details of how and when they operate efficiently enough to stabilize a foliation are unknown there is however a tendency for some of them to operate more efficiently at high strains high temperatures and in flow regimes with high vorticity natural and experimental high temperature shear zones are accordingly one environment in which steadystate foliations may be encountered an experiment is described in which a thin specimen of para dichlorobenzene was given a large shearing deformation at 90 of its absolute melting point a steady state foliation was not produced but the technique is a promising one for further microstructural studies where in situ observation of material undergoing large deformations is desirable

middle holocene alluvial forests and associated fluvial environments a multi proxy reconstruction from the lower scheldt n belgium analyses of pollen plant macrofossils seeds fruits wood and mosses molluscs diatoms and vertebrate mainly fish remains allowed a detailed reconstruction of a middle holocene alluvial forest and its associated hydrological conditions the use of multiple proxies resulted in a taxonomically more detailed and environmentally more comprehensive understanding of terrestrial as well as aquatic habitats the results demonstrate possible biases in palaeoecological reconstructions of alluvial and estuarine environments drawn from single proxies many locally occurring woody taxa were underrepresented or remained undetected by pollen analyses seeds and fruits also proved to be inadequate to detect several locally important taxa such as ulmus and hedera helix apparently brackish conditions inferred from diatoms pollen and other microfossils conflicted strikingly with the evidence from molluscs fish bones and botanical macroremains which suggest a freshwater environment brackish sediment and the microfossil indicators is likely to have been deposited during spring tides or storm surges when estuarine waters penetrated more inland than usual despite the reworking and deposition of estuarine and saltmarsh sediment well above the tidal node at such events local salinity levels largely remained unaffected

water level changes in the flevo area central netherlands 5300 1500 bc implications for relative mean sea level rise in the western netherlands abstract the younger post 4000 cal bc part of the water level curve for the eastern flevo area central netherlands runs below the relative mean sea level msl curve for the western and northern netherlands mededelingen rijks geologische dienst 36 1 1982 93pp we investigated if this difference can be attributed to i root rejuvenation of the bulk dated basal peat samples on which the curve for the eastern flevo area is based and or ii underestimation of the water depth in which the dated peat accumulated it appears that these potential sources of error did not influence significantly the results obtained by roeleveld and gotje de holocene laagveenontwikkeling in de randzone van de nederlandse kustvlakte noordoostpolder unpublished ph d thesis vrije universiteit amsterdam 1993 pp 76 86 on the basis of new and recently published water level data from the eastern and southwestern flevo area we confirm refine and tentatively extend the water level rise reconstruction by roeleveld and gotje and establish a relative msl trend curve for the central netherlands the systematic age differences of our radiocarbon dates on various fractions of four new basal peat samples from the eastern flevo area support the interpretation by roeleveld and gotje that the younger part of the 1982 msl curve may be based on basal peat samples all from the rotterdam area that have been dated 100 200 yr too old if this interpretation is correct the fact that the relative msl curve for the central netherlands lies below the 1982 msl curve cannot be interpreted to indicate less crustal subsidence for the rhine meuse delta as predicted by geophysical modeling j quat sci 17 2002 535

relative sea level rise and neotectonic events during the last 6500 yr on the southern eastern rhone delta france abstract the analysis of peat formations from the eastern limit of the rhone delta allows us to follow relative sea level changes over the last 6300 yr the curve represents two periods of rapid relative sea level rise about 2 mm yr the first between 6295 50 and 4585 45 bp and then the second between 2120 55 and 1200 55 bp these two periods are separated by a period of stability between 4085 60 and 3520 55 bp the comparison with data from the rocky coast to the east of marseille indicates a negative difference of between 1 5 and 0 5 m then rapid adjustment after 2120 55 bp the existence of an incompressible substrate along with the thinning out of the holocene deposits along the limits of the deltas restricted the effects of subsidence and compaction we prefer the hypothesis that tecto subsident movements account for these differences as well as the rapid rise in relative sea level during this second period this is compatible with the network of post miocene faults that account for the differences in altitude of the roman quarries carved out from the miocene layers

the streif classification system a tribute to an alternative system for organising and mapping holocene coastal deposits the classification system for organising and mapping holocene coastal deposits as introduced by streif is highlighted with respect to mapping requirements apart from the requirements such as a user friendly legend and map the linkage of the classification system with the history of deposition is demonstrated for the tide dominated lowlands of the southern north sea and english channel the linkage becomes obvious when considering the effect of the changes in the rate of relative sea level rise the difficulties that surrounded the lithostratigraphy of holocene coastal deposits and the principles of the classification system which eventually made an end to the well known and long standing debate about the lithostratigraphy are briefly recalled

the relationship of strain and preferred orientation of phyllosilicate grains in rocks a review abstract the calculation of strain from the preferred orientation of platy phyllosilicate grains taking strain to be homogeneous is surprisingly often successful from a pragmatic point of view although numerous theoretical objections to this procedure can be and have been raised for the calculation to succeed the original distribution of mica or clay mineral grains must be known or assumed the usual assumption that the starting distribution was random and therefore nearly uniform implies that the strain history of pelitic sediments is taken to start when the watery sediment was last stirred by waves or bioturbation or if it was laid down in still anoxic waters from the moment of first deposition it therefore includes compaction as part of the strain history which is usually neglected by structural geologists originally random distribution of clay flake orientations has been observed in recently deposited sediments in many instances and has been theoretically explained in various ways exceptions probably exist but their frequency has not been estimated biologically disturbed sediments may be brought nearer to a state of random orientation of clay flakes than they were at deposition with the exception of whole beds or concretions in which pores are early filled with cement mudrocks are almost always compacted by the weight of later deposits the strain so induced is axially symmetric about the vertical and thus about the pole of the bedding planes compaction acts on soft unconsolidated rocks but may continue with increasing overburden on rocks strengthened by cementation and by increasing interlocking of grains tectonic deformation may start early before the rock is fully compacted or it may begin only much later and the mechanisms of deformation increase in complexity with the increasing temperature and hydrostatic stress of deeper burial up to a certain level of mild metamorphism however phyllosilicate grains seem to be rather permanent if not as mineral species then at least by preservation of their constituent sheets of silica tetrahedra given this permanence the mechanisms of rock deformation whether intergranular slip cataclasis or dissolution and reprecipitation and various intragranular processes in the non phyllosilicate matrix hardly matter as far as the recording of strain is concerned even a certain amount of stress solution at especially heavily loaded points of the phyllosilicate grains themselves does not destroy their value as strain markers as long as the dissolved material is disposed of mainly by crystallographically continuous overgrowth on existing grains the same holds for local dissolution of phyllosilicates in portions of old grains that have become thermodynamically unstable by bending widespread irregular or random nucleation and growth of newly nucleated phyllosilicate grains at intermediate or high grades of metamorphism can reduce the reliability of the strain record and so can domainal structure of the deformed rock if both the volume fraction of phyllosilicate grains and the intensity of total strain differ sharply from one domain to another if distinct domains are not equant and have themselves a strong preferred orientation of shape nevertheless rocks containing an anastomosing network of zones rich in phyllosilicate grains as slates and other deformed mudrocks commonly do have in many cases been found to have average preferred orientations of mica or chlorite which if used to estimate the strain give results similar to those obtained from independent strain markers in the same rocks thus the most significant verification of the usefulness of strain estimates by measurement of preferred orientation is the mutual confirmation with independently determined strain the limit to such verification is the rarity of strain markers so that the coexistence of two independent ones is exceptionally rare for this reason however it is important to make full use of the orientation of phyllosilicate grains where they are available the alternative to have no strain measurements at all causes structural geologists to miss potential information

mathematical model relationship between the paramagnetic anisotropy and strain in slates abstract a simple mathematical model is used to investigate the relationship between the paramagnetic anisotropy and strain in slates the relationship found is similar to the relationship of whole rock magnetic anisotropy to strain in weakly magnetic slates the anisotropy is probably mostly due to paramagnetic phyllosilicates and the whole rock relationship reflects the paramagnetic fraction

sedimentology and stratigraphy of a tidal sand bank in the southern north sea abstract a set of 125 vibrocores collected on the basis of a dense grid of high and very high resolution seismic coverage over a tidal sand bank the middelkerke bank provides a unique opportunity to reconstruct the stratigraphy and sedimentary facies succession of such a large tidal sand body five sedimentary facies are distinguished they range from clay to pebble and display various types of bedding and lithologies corresponding to different depositional environments a succession of four late quaternary units are defined on the basis of the stratigraphic framework given by the seismic grid the first unit represents the infill of a palaeovalley system by tidally influenced sedimentary facies it is followed by extensive and thick lagoonal or sub tidal deposits the third unit reveals the development of a landward prograding storm dominated sand bar this unit is dominated by clean fine sand the last unit corresponds to the present day tidal sand bank it shows the typical offshore tidal sand bank facies cross bedded sand prograding in an offshore direction like other banks located in a more offshore position the middelkerke bank is a composite bank incorporating facies which do not occur in classic tidal sand banks

holocene sea level database for the rhine meuse delta the netherlands implications for the pre 8 2 ka sea level jump abstract this paper provides the most accurate sea level index points slips for the rhine meuse delta rmd the netherlands identified amidst a wealth of data accumulated in sixty years of research following documented protocols 106 selected radiocarbon dates from peat beds from transgressed valley floor upper estuarine and back barrier lagoonal settings were first listed individually then screened in ensemble on quantified age depth position and inshore palaeotidal setting the database contains 50 slips and 56 upper limiting data points spanning a depth range of 34 to 1 5 m the dates in the database originate from dedicated sea level research which kept surface elevation and sampling depth uncertainty small and sampling of basal peat beds was favoured keeping compaction uncertainties small too the slips cover an age range of 8 8 3 0 ka bp and are available from greater rotterdam and its near offshore for upper limiting data points the coverage extends offshore tracing the rhine palaeovalley and reaches back to 11 5 ka bp the age depth data density and spatial concentration of subsets of dates allow to perform bayesian radiocarbon calibration and to reduce temporal uncertainty by 25 for the average sample 1 age uncertainty 75 cal yr when depth position and rates of relative sea level rise rslr are used to assign sequence order between 8 0 4 5 ka bp rates of rslr gradually decreased from 9 to 1 mm yr in the millennium before rates of rslr were much higher on average 10 mm yr and marked by a sea level jump between 8 45 8 2 ka bp a two phased nature of this jump starts to be resolved with local magnitudes of 1 7 0 6 m 1 first phase and 0 2 0 2 m second phase corresponding to globally averaged jumps of 2 5 m 0 9 m for the first and 0 3 0 3 m for the second phase for the pre 9 ka bp period only offshore upper limiting data points are currently available until new offshore data are gathered trends of rslr before 9 ka bp can only be estimated fed with global insights in post glacial eustasy regional estimates regarding rates of glacio isostatic adjustments and tectonic subsidence and sedimentary geological interpretations of scattered basal peat presence

anisotropy of diamagnetic susceptibility in thassos marble a comparison between measured and modeled data abstract a study of shear zones within the calcite marble complex of the island of thassos greece shows that the low field anisotropy of magnetic susceptibility ams technique can be successfully applied to diamagnetic rocks for characterizing rock fabrics the strain path involves both an early pure shear stage and a simple shear overprint that is documented by a transition from triaxial neutral to uniaxial prolate shapes of ams ellipsoids the maximum susceptibility is oriented perpendicular to the rock foliation reflecting the preferred orientation of calcite c axes in the protolith as well as in the mylonites for three samples that represent different types of calcite fabrics the ams was recalculated from neutron and electron backscatter diffraction textural data a comparison of the measured and modeled data shows a good coincidence for the orientation of the principal ams axes and for the recalculated anisotropy data both measured and modeled data sets reflect the change from neutral to distinct prolate ellipsoids during progressive deformation

paramagnetic metamorphic mineral assemblages controlling ams in low grade deformed metasediments and the implications with respect to the use of ams as a strain marker a regional analysis of the anisotropy of magnetic susceptibility ams has been performed on low grade metamorphic deformed homogeneous siltstone beds hsbs of the plougastel formation in the central armorican domain together with exhaustive compositional analyses of the studied specimens despite sampling a single horizon different paramagnetic minerals are controlling the ams in the crozon peninsula sites white mica and chlorite and in the inland sites of the central armorican domain white mica chloritoid and some chlorite both the crozon peninsula and inland datasets show a hockey stick shaped pattern on a plot of the shape parameter t versus the corrected degree of anisotropy p j although the whole pattern is shifted to higher p j values for the inland dataset high field ams indicates that the low field p j and t values from two inland sites are slightly enhanced by a small ferromagnetic sensu lato contribution furthermore variation in p j and t values within single sites can be attributed to an effect of the observed quartz white mica ratio as quartz grains disrupt the petrofabric intensity our findings clearly demonstrate that the ams of the hsbs in the central armorican domain is strongly influenced by compositional variations and does not merely indicate tectonic strain even in very similar tectonostratigraphic settings supplementary material outcrop coordinates with information on the hsbs and samples and the summarized low field room temperature ams data are available at www geolsoc org uk sup18578

holocene relative sea level change isostatic subsidence and the radial viscosity structure of the mantle of northwest europe belgium the netherlands germany southern north sea abstract a comprehensive observational database of holocene relative sea level rsl index points from northwest europe belgium the netherlands northwest germany southern north sea has been compiled in order to compare and reassess the data collected from the different countries regions and by different workers on a common time depth scale rsl rise varies in magnitude and form between these regions revealing a complex pattern of differential crustal movement which cannot be solely attributed to tectonic activity it clearly contains a non linear glacio and or hydro isostatic subsidence component which is only small on the belgian coastal plain but increases significantly to a value of ca 7 5 m relative to belgium since 8 cal ka bp along the northwest german coast the subsidence is at least in part related to the post glacial collapse of the so called peripheral forebulge which developed around the fennoscandian centre of ice loading during the last glacial maximum the rsl data have been compared to geodynamic earth models in order to infer the radial viscosity structure of the earth s mantle underneath nw europe lithosphere thickness upper and lower mantle viscosity and conversely to predict rsl in regions where we have only few observational data e g in the southern north sea a very broad range of earth parameters fit the belgian rsl data suggesting that glacial isostatic adjustment gia only had a minor effect on belgian crustal dynamics during and after the last ice age in contrast a narrow range of earth parameters define the southern north sea region reflecting the greater influence of gia on these deeper older samples modelled rsl data suggest that the zone of maximum forebulge subsidence runs in a relatively narrow wnw ese trending band connecting the german federal state of lower saxony with the dogger bank area in the southern north sea identification of the effects of local scale factors such as past changes in tidal range or tectonic activity on the spatial and temporal variations of sea level index points based on model data comparisons is possible but is still complicated by the relatively large range of earth model parameters fitting each rsl curve emphasising the need for more high quality observational data

the chinamora batholith zimbabwe structure and emplacement related magnetic rock fabric abstract the origin of dome and keel structural geometries in archean granite greenstone terrains appears to lack any modern analogues and is still poorly understood the formation of these geometries is investigated using structural and anisotropy of magnetic susceptibility ams data for the chinamora batholith in zimbabwe the roughly circular shaped batholith is surrounded by ca 2 72 2 64 ga greenstones the batholith granitoid suites have been divided on the basis of their ages and fabric relationships into four distinct units i banded basement gneisses ii granodioritic gneisses iii equigranular granites and iv central porphyritic granites in the gneissic granites a partial girdle n s of poles to the magnetic foliation is developed that has been folded around a consistent flat lying magnetic lineation plunging at shallow angles to the e or w in the equigranular granites the magnetic lineation generally plunges to the nw the magnetic foliation has a variable strike no clear trends can be distinguished the ams measurements of the porphyritic granite revealed a nw se striking foliation and showed subhorizontal magnetic lineations the magnetic foliation is subparallel to the macroscopic foliation wall rocks are moderately inclined and show radial or concentric lineations triaxial strain ellipsoids and kinematics that demonstrate off the dome sliding and coeval pluton expansion the results of the observations do not point to a single emplacement process neither the observed structural data nor the magnetic fabric support a model envisaging spherically ballooning it is argued that pluton diapirism played a major part in the formation of the fabrics in the gneisses whereas the fabrics in the porphyritic granites reflect emplacement as laccolith like sheets

resolution of ferrimagnetic and paramagnetic anisotropies in rocks using combined low field and high field measurements summary a method of separation of ferrimagnetic and paramagnetic components of magnetic anisotropy from the total anisotropy is developed from the anisotropy measurement of a specimen in a low field susceptibility anisotropy and from measurement in two high fields stronger than the saturation field of the ferrimagnetic fraction present the following anisotropy components can be calculated susceptibility anisotropy field independent of the paramagnetic fraction low field susceptibility anisotropy of the ferrimagnetic fraction and high field anisotropy of the ferrimagnetic fraction errors possibly arising from imperfect saturation of the ferrimagnetic fraction in the field practically available are analysed

magnetic anisotropy rock fabrics and finite strain in deformed sediments of sw sardinia italy abstract although some empirical relationships have been established between the anisotropy of magnetic susceptibility ams and the state of finite strain in studies from specific geologic areas the mechanisms governing correlations are not well understood a comparative study has been made in order to elucidate the ams strain relationship by investigating mineral preferred orientations and the responsible microstructural deformation processes detailed analyses are presented from low grade metamorphic slates of a palaeozoic sequence exposed in the variscan of sw sardinia rock magnetic experiments suggest that paramagnetic minerals dominate the ams in these rocks excellent agreement was found between magnetic fabrics and lattice preferred orientations 001 of mica and chlorite determined from x ray texture goniometry measurements depending on the oblate or prolate ellipsoidal shape of anisotropy the minimum principal axes of ams and x ray textures can coincide with the poles to slaty cleavage or the maximum principal axes can coincide with the bedding cleavage intersection respectively the measured ams and x ray textures only partially reflect the finite strain determined from deformed micro pebbles and reduction spots axial orientations of magnetic fabrics mica and chlorite preferred orientations and finite strain ellipsoids are generally in good agreement depending on development of oblate or prolate fabric ellipsoidal shapes linear correlations can be established for magnitudes of minimum and intermediate axes of the ams and finite strain ellipsoids but shape comparisons are complex microstructural studies by scanning electron microscopy sem indicate that the preferred orientation of the phyllosilicates is caused by different grain scale deformation mechanisms such as kinking micro folding and preferential growth thus magnetic fabrics and mineral preferred orientations evidently result from different deformation mechanisms than the finite strain they reflect the heterogeneous deformation due to micro mechanical reorientation processes of mineral grains while finite strain reflects the homogeneous deformation accommodated cumulatively by the strain markers

chironomid responses insect diptera to younger dryas and holocene environmental changes in a river floodplain from northern france st momelin st omer basin lateglacial to holocene subfossil chironomids from the st omer basin at st momelin northern france were analysed at the end of the lateglacial stratigraphic and chironomid sequences indicate a shallow oligotrophic and slow flowing freshwater stream with abundant aquatic macrophytic vegetation cold water adapted taxa indicate a cold climate during the early holocene from about 9500 to 7700 conventional radiocarbon yr bp climate improvement is marked by an increase in warm water adapted taxa and a decrease in cold water fauna however the cold water fauna persist probably because of both the instability and continentality of the climate during the mid holocene from about 7700 to 6000 bp the marine transgression strongly influenced the river s hydrological regime and consequently the chironomid assemblages at that time eutrophic warm and shallow stagnant water conditions occured throughout the basin from 6000 to 3200 bp the st momelin basin was subjected to a marine regression chironomids indicate a hydrological regime marked by an alternance of phases with either a dominance of rheophilous or limnophilous fauna during this period equivalent percentages of warm and cold adapted taxa may be explained by cold water input in context of a temperate climate

preferred mineral orientation of a chloritoid bearing slate in relation to its magnetic fabric 2014 elsevier ltd a regional analysis of the anisotropy of the magnetic susceptibility on low grade metamorphic chloritoid bearing slates of the paleozoic in central armorica brittany france revealed very high values for the degree of anisotropy up to 1 43 nonetheless high field torque magnetometry indicates that the magnetic fabric is dominantly paramagnetic chloritoid s intrinsic degree of anisotropy of 1 47 0 06 suggests that chloritoid bearing slates can have a high degree of anisotropy without the need of invoking a significant contribution of strongly anisotropic ferromagnetic s l minerals to validate this assumption we performed a texture analysis on a representative sample of the chloritoid bearing slates using hard x ray synchrotron diffraction the preferred orientation patterns of both muscovite and chloritoid are extremely strong 38 6m r d for muscovite 20 9m r d for chloritoid and display roughly axial symmetry about the minimum magnetic susceptibility axis indeed suggesting that chloritoid may have a profound impact on the magnetic fabric of chloritoid bearing rocks however modeling the anisotropy of magnetic susceptibility by averaging single crystal properties indicates that the cpo of chloritoid only partially explains the slate s anisotropy

holocene evolution of relative sea level and local mean high water spring tides in belgium a first assessment abstract holocene age depth data from the belgian coastal plain basal peat data particularly are assessed in terms of local water and tide levels basal peat formation was generally induced by sea level rise effects of local seepage were limited and significant river gradient effects were absent no relation was found between the timing of basal peat inception and substrate permeability in general edaphic moisture conditions were unfavourable for organic accumulation prior to sea level related rise of the groundwater table error envelopes for the minimum level of local mean high water spring tides and for upper and extreme lower relative mean sea level limits during the last 9400 solar years 8400 yrs b p are presented these indicate that the rate of relative sea level rise showed marked retardations at ca 7500 7000 yrs cal b p 6650 6100 yrs b p and ca 5500 5000 yrs cal b p 4400 yrs b p a eustatic explanation appears to be plausible particularly for the former prior to ca 4000 yrs cal b p ca 3600 yrs b p the relative sea level rise in belgium differs noticeably from that established for the western netherlands with both diverging progressively back in time this implies that considerable differential crustal movement occurred between the two areas in the early holocene

current challenges and future developments in magnetic fabric research abstract magnetic fabrics are used extensively as proxies for mineral fabrics and to correct paleomagnetic data and have been proposed to quantify pore fabrics today s understanding and interpretation of magnetic anisotropy benefits from decades of carefully observing anisotropic mineral and rock properties establishing and testing empirical relationships between magnetic and mineral fabrics and developing models to quantify aspects of anisotropy each advance was preceded by some puzzling observations i e data that could not be explained based on the models available at the time e g oblique or inverse fabrics or lithology dependent anisotropy strain relationships these observations led to numerous experimental and numerical techniques designed to characterize magnetic fabrics and determine their origin despite the successful application of magnetic fabrics in many structural and tectonic problems there are still phenomena and measurements that cannot be explained based on today s magnetic fabric theory with the purpose of fostering future development i will touch on three main areas where i see challenges in magnetic fabric research 1 experimental characterization of magnetic anisotropy including the non uniqueness of reported tensors and non linearity 2 anisotropy modelling and defining the carrier minerals and origin of the magnetic fabric 3 selection of adequate sets of anisotropy tensors to correct paleomagnetic data the description of the challenges presented here will hopefully help define directions for future research inform those that are new to anisotropy and advance our field

a new holocene relative sea level curve for western brittany france insights on isostatic dynamics along the atlantic coasts of north western europe abstract this study presents new relative sea level rsl data that were obtained in the finistere region western tip of brittany france and the implications those data have for the understanding of the isostatic dynamics across north western europe and more specifically along the atlantic and channel coasts new stratigraphic sequences were obtained and analyzed to derive 24 new sea level index points in which 6 are basal these new data considerably increase the knowledge we have of the rsl evolution along the coasts of western brittany since the last 8 kyr b p from this new dataset rsl was estimated to rise continuously over the last 8 kyr with a major inflection at ca 6 kyr cal bp our results show large vertical discrepancies between the rsl records of brittany and south western uk with the latter plotting several meters below the new data from this comparison we suggest that the two regions underwent a very different pattern and or amplitude of subsidence during the last 8 kyr which has implications for the spatial and temporal pattern of the peripheral bulge of the european ice sheets we compared our data against predictions from glacio isostatic adjustment models gia models there are large misfits between rsl observations and the predictions of the global ice 5g vm2a peltier 2004 glac1 b tarasov and peltier 2002 tarasov et al 2012 briggs et al 2014 and regional uk models biis bradley et al 2009 bradley et al 2011 kuchar kuchar et al 2012 which can t be resolved through significant changes to the deglaciation history and size of the british irish ice sheet paleo tidal modelling corrections indicate regional changes in the tidal ranges played a negligible role in the data model misfits hence we propose that the misfits are due to some combination of i unaccounted mass loss of far field ice sheets antarctic ice sheet or laurentide ice sheet ii unresolved differences in the deglaciation history and size of the fennoscandian ice sheet or more likely iii significant lateral variations in the earth s structure across the english channel

sediment supply and barrier dynamics as driving mechanisms of holocene coastal change for the southern north sea basin the combined effects of climate change and human impact lead to regional and local coastal responses that pose major challenges for the future resilience of coastal landscapes increasing the vulnerability of communities infrastructure and nature conservation interests using the suffolk coast southeast england as a case study we investigate the importance of sediment supply and barrier dynamics as driving mechanisms of coastal change throughout the holocene litho bio and chronostratigraphic methods are used to decipher the mechanisms of coastal change from the record preserved within coastal stratigraphy results suggest that local coastal configuration and sediment supply were the most influential in determining coastal change during the mid and late holocene against a background control of sea level rise the importance of sedimentological and morphological factors in shaping holocene coastal changes in the southern north sea basin must therefore be considered when using the database of evidence from this region as an analogue for future change under accelerated sea level rise

preferred orientation of phyllosilicates in phyllonites and ultramylonites abstract x ray texture goniometry operated in the transmission mode has been applied to fine grained phyllosilicate rich sc mylonites from the santa rosa mylonite zone california the whipple mountains core complex california and the austroalpine nappes of the eastern alps austria basal planes 001 phyllosilicate pole figures depart in two respects from orthorhombic symmetry a the maximum pole density deviates from the pole to the mylonitic foliation and lies along a great circle which is normal to the foliation and contains the mylonitic lineation and b the contours of equal pole density are more widely spaced on one side of the 001 maximum than on the other measured along the mylonitic lineation optical microscopy reveals s and c surfaces and sets of shear bands sb characteristic of non coaxial deformation the pole figures are used for two purposes a the first is strain estimation after the march model by imposing orthorhombic symmetry the resulting march strains are more or less the same in all californian samples this is interpreted as evidence for a steady state foliation b the second is shear sense determination it is demonstrated that consistently asymmetric preferred orientations reflect structures which are typical of non coaxial deformation it is concluded that x ray analysis of phyllosilicate rich mylonites can in addition to providing an estimate of total strain give information about deformation regime and shear sense furthermore the study documents the heterogeneous nature of deformation on macroscopic and microscopic scales and the importance of non coaxial deformation in accommodating large strains

the indicative meaning of diatoms pollen and botanical macro fossils for the reconstruction of palaeoenvironments and sea level fluctuations along the coast of lower saxony germany abstract interdisciplinary studies carried out on marine and terrestrial deposits such as tidal flats lagoonal deposits and salt marshes have provided the basis for interpreting holocene sea level fluctuations along the southern north sea coast radiocarbon dating provides the timeframe for the studies the employed palaeoecological techniques include analysis of pollen diatoms and botanical macro remains benefits and constraints of each technique are discussed using examples of sediment cores from around the southern north sea sea level index points have been defined using the results of these interdisciplinary studies and then employed to reconstruct the sea level oscillations of the last two millennia

mathematical simulations of anisotropy of magnetic susceptibility on composite fabrics 1 the anisotropy of magnetic susceptibility ams is an integral measure of the preferred orientation of all minerals present in a rock when the ams is carried by paramagnetic minerals alone the principal directions of the susceptibility ellipsoid should reflect the crystallographic orientation of the minerals the relationship between the ams and deformation depends on several factors which control the development of lattice preferred orientation lpo in a rock a mathematical model is presented that simulates the magnetic susceptibility ellipsoid for samples composed of more than one mineral phase measurements of the ams are compared with fabric based anisotropy models for black slates from the navia alto sil slate belt in northern spain the ams is carried by paramagnetic minerals as has been confirmed by high field torque magnetometry low temperature ams and magnetization curves the lpo of mica and chlorite has been determined by x ray texture goniometry pole figures and orientation ellipsoids show the changes in the degree of alignment of the phyllosilicates the models have been tested in samples displaying three types of pole figures a high intensity point maximum a medium intensity elliptical maximum and a girdle shaped distribution at one site displaying kink bands the lpo shows variations between these types at the outcrop scale the case studies illustrate the success in modeling different lpo types

conversion of the magnetic susceptibility tensor into the orientation tensor in some rocks abstract the preferred orientation of minerals in a rock with a structural or sedimentary fabric can be referred to by the orientation tensor this paper describes the determination of the orientation tensor of the crystallographic c axes from the rock magnetic anisotropy and the mineral anisotropy degree in rocks in which the magnetic anisotropy is dominantly carried by one mineral with uniaxial magnetic anisotropy e g phyllosilicates pyrrhotite hematite the orientation tensor of biotite c axes in four samples of the bites orthogneiss determined in this way is similar to that determined independently through the universal stage measurement of biotite leaves in thin sections and is obtained much more rapidly by the magnetic method

improving methodology for high resolution reconstruction of sea level rise and neotectonics by paleoecological analysis and ams 14c dating of basal peats abstract sea level research in several submerging coastal regions has traditionally been based on 14 c dating of basal peats that overlie a compaction free substratum and can be related to paleo ground water levels provided that an unequivocal relationship between ground water level and sea level can be assumed this approach contains two sources of uncertainty 1 the paleoenvironmental interpretation of samples is usually based on inherently inaccurate macroscopic descriptions in the field and 2 14 c ages of bulk peat samples may be erroneous as a result of contamination due to the uncertainties in both the altitude and the age the two crucial sources of evidence necessary to arrive at accurate sea level curves sea level index points are therefore represented by considerable but typically not quantified error boxes accelerator mass spectrometry ams opens new perspectives for this type of sea level research as illustrated by a paleoecological and ams 14 c study of basal peats from a small study area in the rhine meuse delta the netherlands where previous conventional work revealed highly problematic results a detailed macrofossil analysis has two purposes 1 an inferred paleoecological succession indicates a relatively accurate level of paludification of the site and hence rise of the ground water level 2 suitable macrofossils from that specific level are then selected for ams 14 c dating in spite of very small sample sizes our results are consistent and indicate that this approach can constitute a step forward in high resolution reconstruction of sea level rise the new results further enable a revision of holocene ground water gradient lines for the rhine meuse delta a knickpoint in these gradient lines can be related to the effect of faulting this approach therefore also has considerable potential to unravel and quantify neotectonic activity in submerging coastal settings

comments on shoreface sand supply and mid to late holocene aeolian dune formation on the storm dominated macrotidal coast of the southern north sea by e j anthony m mrani alaoui and a hequette marine geology 276 2010 100 104 abstract anthony et al 2010 published a recent paper in marine geology on the origin and chronology of an inland dune for which they presented an explanation for the regional pattern of mid to late holocene coastal development this explanation contradicts other data collected from this coastal area it is moreover in contrast to our current understanding of holocene coastal evolution of the southern north sea the data used by anthony et al 2010 includes a number of inconsistencies that led the authors to incorrect conclusions this discussion reports on our critical evaluation of data and reasoning in antony et al 2010 we propose an alternative model of coastal evolution which is in line with the current knowledge about mid to late holocene coastal evolution

anisotropy of complex magnetic susceptibility as an indicator of strain and petrofabric in rocks bearing sulphides abstract a new method anisotropy of complex magnetic susceptibility acms for determining the petrofabric of specimens with conductive minerals is developed the method uses the same induction coil equipment and techniques that can be used for the measurement of the anisotropy of magnetic susceptibility ams however a higher 100 khz operating frequency emphasizes the electrical conductivity response and thus yields a measure of the anisotropy of electrical conductivity of the specimen the method was tested on variably deformed plasticine samples containing aluminium fabric markers and on synthetic aggregates of pyrrhotite and talc pyrrhotite mixtures deformed triaxially at a confining pressure of 200 mpa 2 kbar by up to 35 homogeneous shortening acms successfully defines the petrofabric and permits prediction of the principal directions of finite strain the intensity of ams and to a lesser extent of acms correlate with the strain ratio in these simple coaxial flattening plane strain experimental deformations on selected materials

late quaternary sea level change and isostatic and tectonic land movements along the belgian dutch north sea coast geological data and model results early and middle holocene sea level data from belgium plot ca 2 m above data from the western netherlands reflecting differential tectonic and isostatic movements the total uplift rate of belgium relative to the western netherlands decays gradually from 0 66 m kyr 1 at 7500 cal yr bp to less than 0 25 m kyr 1 since 5000 cal yr bp the tectonic component of this relative movement inferred from eemian sea level data is in the order of 0 06 to 0 16 m kyr 1 the isostatic component of the uplift is related to the last phase of the collapse of a peripheral bulge under the netherlands and the dutch and german sectors of the north sea and to hydroisostatic subsidence of the north sea basin caused by water loading as sea level rose comparisons with isostatic rebound models show that they predict well the holocene isostatic movement between belgium and the western netherlands and that the predictions are improved when the tectonic component is removed from the observations preliminary evaluation of sea level data from the dutch sector of the north sea shows that glacio hydroisostatic subsidence relative to belgium was significantly greater than for the western netherlands coastal area and spatially highly variable copyright 2002 john wiley sons ltd