mafic and felsic magma interaction in granites the hercynian karkonosze pluton sudetes bohemian massif the hercynian post collisional karkonosze pluton contains several lithologies equigranular and porphyritic granites hybrid quartz diorites and granodiorites microgranular magmatic enclaves and composite and lamprophyre dykes field relationships mineralogy and majorand trace element geochemistry show that 1 the equigranular granite is differentiated and evolved by small degrees of fractional crystallization and that it is free of contamination by mafic magma 2 all other components are affected by mixing the end members of the mixing process were a porphyritic granite and a mafic lamprophyre the degree of mixing varied widely depending on both place and time all of the processes involved are assessed quantitatively with the following conclusions most of the pluton was affected by mixing implying that huge volumes 475 km of mafic magma were available this mafic magma probably supplied the additional heat necessary to initiate crustal melting part of this heat could have also been released as latent heat of crystallization only a very small part of the karkonosze granite escaped interaction with mafic magma specifically the equigranular granite and a subordinate part of the porphyritic granite minerals from these facies are compositionally homogeneous and or normally zoned which together with geochemical modelling indicates that they evolved by small degrees of fractional crystallization 520 accessory minerals played an important role during magmatic differentiation and thus the fractional crystallization history is better recorded by trace rather than by major elements the interactions between mafic and felsic magmas reflect their viscosity contrast with increasing viscosity contrast the magmatic relationships change from homogeneous hybrid quartz diorites granodiorites to rounded magmatic enclaves to composite dykes and finally to dykes with chilled margins these relationships indicate that injection of mafic magma into the granite took place over the whole crystallization history consequently a long lived mafic source coexisted together with the granite magma mafic magmas were derived either directly from the mantle or via one or more crustal storage reservoirs compatible element abundances e g ni show that the mafic magmas that interacted with the granite were progressively poorer in ni in the order hybrid quartz dioritescgranodioritescenclavesccomposite dykes this indicates that the felsic and mafic magmas evolved independently which in the case of the karkonosze granite favours a deep seated magma chamber rather than a continuous flux from mantle two magma sources mantle and crust coexisted and melted almost contemporaneously the two reservoirs evolved independently by fractional crystallization however mafic magma was continuously being intruded into the crystallizing granite with more or less complete mixing several lines of evidence e g magmatic flux structures incorporation of granite feldspars into mafic magma feldspar zoning with fluctuating trace element patterns reflecting rapid changes in magma composition indicate that during its emplacement and crystallization the granite body was affected by strong internal movements these would favour more complete and efficient mixing the systematic spatial temporal association of lamprophyres with crustal magmas is interpreted as indicating that their mantle source is a fertile peridotite possibly enriched metasomatized by earlier subduction processes

correlation of allochthonous terranes and major tectonostratigraphic domains between nw iberia and the bohemian massif european variscan belt the nw iberian allochthon and the tepla barrandian and moldanubian zones represent the internal parts of the variscan belt in their respective domains a correlation based on the lithological association protolith ages metamorphic evolution detrital zircon age spectra and tectonic setting is attempted between the nw iberian massif and se bohemian massif in order to check whether they could have formed part of the same allochthonous stack the galicia tras os montes zone of the iberian massif and the internal zones of the bohemian massif include from bottom to top a parautochthon and lower allochthon representing the outer edge of the northern gondwana margin an oceanic middle allochthon with cambro ordovician and early devonian ophiolites and an upper allochthon interpreted as a peri gondwanan terrane early variscan subduction related high pressure metamorphism characterizes many of the allochthonous units with ages younging from the structurally upper to the lower units from 400 385 ma to 370 360 ma respectively high and ultrahigh pressure metamorphism occurred also in the saxothuringian autochthon at 360 340 ma but not in the nw iberian autochthon the different behavior of the autochthon in the iberian and bohemian massifs accounts for their distinct evolutions from 360 ma onward we conclude that the upper allochthon was a unique peri gondwanan terrane whereas the middle allochthon represents units of the same peri gondwanan ocean opened at the cambro ordovician boundary and having recorded localized renewed activity in the silurian early devonian no other oceans separated the lower allochthon parautochthon and autochthon

eclogite facies rocks of the monotonous unit clue to variscan suture in the moldanubian zone bohemian massif abstract the formation and exhumation of variscan high to ultrahigh pressure metamorphic rocks from the moldanubian zone in the bohemian massif are the subject of controversy regarding their unclear relationship to possible subduction zones in this paper we present the results of a petrological study of eclogites that occur together with serpentinites within amphibolite facies gneisses in the moldanubian zone east of the tepla barrandian block more than 100 bodies of retrogressed eclogite and serpentinite follow an approximately 250 km long sw ne trending zone in the central part of the bohemian massif together with surrounding gneisses the eclogites share a medium to low pressure amphibolite facies metamorphism p t conditions estimated for the eclogite facies stage indicate a relatively low temperature geothermal gradient similar to those observed in the saxothuringian zone which occurs north and northwest of the tepla barrandian block the presence and distribution of eclogites and comparison of their p t and age data with hp uhpm rocks in other units in the bohemian massif allow us to constrain the variscan suture which straddles the se of the tepla barrandian block the existence of this suture in relation to available geotectonic models and its possible continuation through other allochthonous units along the european variscan belt are discussed

the presumed tepla barrandian moldanubian terrane boundary in the orlica mountains sudetes bohemian massif structural and petrological characteristics the sudetes in southwestern poland and northern bohemia expose a palaeozoic collage of the northeastermost extremity of the variscan belt one of presumed terrane boundaries occurs in the orlica mts along the contact between the phyllite amphibolite complex neoproterozoic of the nove m sto unit of probable tepla barrandian affinities in the sw and the orthogneiss early ordovician protolith and mica schist neoproterozoic complexes of the orlica nieznik unit in the ne most likely representing the moldanubian terrane the synmetamorphic structural evolution of both adjacent units comprised four deformation events the nove m sto rocks have recorded an early stage of ductile top to the se thrusting d1 which must have resulted in an early juxtaposition of the both terranes within a nappe pile the original overthrust contact was subsequently modified by a dextral shear dominated event d2 which produced a 1 2 km wide shear zone at the boundary of both units in which earlier fabric elements were overprinted and mostly obliterated this deformation brought the lower grade nove m sto rocks into present day strike slip contact with those of the regionally uplifted higher grade orlica nieznik unit postdating this juxtaposition are e w trending folds f3 which affect both the adjacent units the contact shear zone also contains record of a late top to the sw semi brittle normal slip displacement d4 downthrowing the nove m sto unit the peak amphibolite facies metamorphic conditions were attained in the orlica nieznik unit and in the contact shear zone prior to the d2 event they corresponded to maximum temperatures and pressures of ca 600 c and 10 kbar respectively the d1 thrusting event in the phyllites of the nove m sto unit took place under greenschist facies conditions ca 350 c and 4 5 kbar and its effects mostly survived the later amphibolite facies metamorphism these structural relationships are equivalent to those observed elsewhere in the bohemian massif on the tepla barrandian moldanubian terrane boundary the characteristic features of this boundary are a high metamorphic gradient but lack of metamorphic inversion the occurrence of mid carboniferous stitching plutons and the importance of mid carboniferous deformation that resulted in significant downwards movement of the low grade tepla barrandian terrane relative to the uplifted high grade and hot lower to middle crust of the moldanubian terrane the downthrow of the tepla barrandian occurred on ductile shear zones showing either down dip slip kinematics or that of transfer strike slip as was the case with the orlica mts both kinematics being associated within the same regional scale linked shear zone extensional system the extensional crustal collapse must have been preceded by a se directed crustal stacking achieved through overthrust emplacement of the tepla barrandian on top of the moldanubian terrane

monazite to the rescue u th pb dating of the intrusive history of the composite karkonosze pluton bohemian massif the large 700 km2 composite karkonosze krkonose pluton in the west sudetes on the border between poland and the czech republic consists mainly of porphyritic and equigranular granitoids but contains a range of lithologies from lamprophyre to leucogranite the absolute age and duration of the plutonism have proved difficult to determine previous age measurements by rb sr ar ar and u pb range from 330 to 290 ma with more recent results converging to 320 300 ma dating of zircon and monazite from samples of a variety of major and minor lithologies by sims u th pb several from the geochemical study of slaby and martin 2008 has narrowed the possible age range further u pb ages measured on eight of ten zircon and monazite samples are in the range 314 311 ma zircon ages measured on the two major types of porphyritic granitoid are 313 3 and 311 4 ma and monazite ages are 312 2 313 3 and 311 3 ma monazite from one hybrid granitoid has an age of 314 3 ma and zircon from another an age of 314 4 ma zircon from a composite dyke has an age of 311 6 ma the monazite u pb age of an equigranular granite at 318 6 ma is consistent with geological evidence that it is older than the porphyritic granitoids but because of the relatively large uncertainties is not conclusive zircon from one microgranular enclave is anomalously young 302 4 ma evidence is mounting that the main porphyritic granitoids hybrid granitoids and composite dykes were emplaced within a short time interval between 314 4 and 311 3 ma given the uncertainties emplacement of these units could have been effectively simultaneous the larger difference between the ages from the equigranular granite and microgranular enclave however indicates that the whole karkonosze thermal episode possibly lasted as long as 15 ma

ages and paleoenvironment of miocene mammalian faunas from thailand abstract the geological survey of continental basins in northern thailand has led to the discovery and the study of several mammalian assemblages in that area all localities from northern thailand occur in a time span ranging from about 16 to 14 ma in addition a diachronism is apparent among the different localities and is indicated by the different stages of evolution in the tooth morphology of rodents ruminants rhinos and mastodonts mae long li basin would be the oldest locality about 16 ma followed by had pu dai lampang basin and then huai siew and ban san klang both in pong basin ban na sai li basin and mae teep would be contemporaneous with ban san klang and mae moh is thought to be the youngest locality in order to study the paleoenvironment of the thai neogene faunas we have used the cenogram method in which structure reflects the general environment of a faunal community we also compared the faunal communities from thailand with those from the pakistan siwaliks and from china in the latter areas the microfauna is well represented and the large mammals are numerous thus suggesting a wet environment with a likely monsoonal climate the middle miocene paleoenvironment in south asia seems to have been quite open and small areas of forests were probably intermixed with grassland the cenogram structure completely excludes an environment dominated by primary forest or by steppe

timing of deglaciation and postglacial environmental dynamics in nw iberia the sanabria lake record abstract the multiproxy study sedimentology geochemistry and diatoms of sediment cores from sanabria lake 42 07 30 n 06 43 00 w 1000 m a s l together with a robust 14c chronology provides the first high resolution and continuous sedimentary record in the region extending back the last 26 ka the development of a proglacial lake before 26 cal ka bp demonstrates the onset of deglaciation before the global last glacial maximum similarly to other alpine glaciers in southern european mountains rapid deglaciation occurred at the beginning of the greenland interstadial gi 1e bolling 14 6 cal ka bp following a short lived episode of glacier re advance 14 4 14 2 cal ka bp gi 1d a climatic improvement at 13 9 cal ka bp suggests the glaciers retreated from the lake basin during the gi 1c another glacier reactivation phase occurred between ca 13 0 12 4 ka starting earlier than the onset of gs 1 younger dryas rapid deglaciation during the early holocene 11 7 10 1 cal ka bp was followed by a period of higher river discharge 10 1 8 2 cal ka bp after 8 2 ka the holocene is characterized by a general decreasing trend in humidity punctuated by the driest phase during the mid holocene ca 6 8 4 8 a wetter interval between 4 8 and 3 3 cal ka bp and a relatively decline of rainfall since then till present with a minor increase in humidity during some phases ca 1670 1760 of the little ice age discrete silt layers intercalated in the organic rich holocene deposits reflect large flooding events of the tera river ca 10 1 8 4 7 5 6 2 5 7 5 6 4 6 4 2 3 7 3 3 3 1 2 7 2 5 and 2 0 cal ka bp their synchronicity with a number of cold and humid events described in the atlantic demonstrates a strong control of nw iberian climate by north atlantic dynamics at centennial millennial scale comparison with western mediterranean records points to similar regional dynamics during the holocene although modulated in the nw iberian peninsula by the stronger atlantic influence

sand invasion along the portuguese coast forced by westerly shifts during cold climate events phases of higher aeolian activity are responsible for the formation and movement of large transgressive dunefields well reported phases of aeolian activity in northwest europe are coincident with global cooling events and were related to enhanced westerly winds and storminess however the extent to which these climatic episodes influenced dunefield dynamics in southwest europe remains an open question ground penetrating radar gpr was used to image the stratigraphy of a cliff top coastal transgressive dunefield in portugal and reconstruct former windfield regimes using optically stimulated luminescence osl five major phases of aeolian activity were dated at 12 6 5 6 1 2 0 4 and 0 3 ka and related to coastal instability and enhanced westerlies these phases were later reconciled to favorable patterns of atmospheric circulation simulated by global and regional climate models at both synoptic and local scales respectively the results prove that major phases of aeolian activity in southwest europe are associated with the onset of cold climate events of global distribution coinciding with aeolian accumulation in northwest europe this implies the dominance of zonal westerlies along the western coast of europe from denmark to portugal during the onset of cold climate events model simulations suggest that the pattern of atmospheric circulation during periods of enhanced aeolian activity is compatible with prolonged negative phases of the north atlantic oscillation nao

vestiges of saxothuringian crust in the central sudetes bohemian massif zircon evidence of a recycled subducted slab provenance abstract four detrital zircon concentrates from the metasediments and metavolcanics of the central sudetes bohemian massif have been dated using shrimp ii the wyszki paragneiss yielded precambrian age spectra similar to those characteristic of the cadomian terranes 1 archaean and palaeoproterozoic zircons are scattered between 2830 and 1867 ma and 2 there are abundant neoproterozoic zircons dated at 803 577 ma the estimated maximum sedimentation age for this rock is 566 4 ma the klodzko fortress pyroclastic metarhyodacite gave an igneous emplacement age of 536 2 ma the magmatic precursor to the subvolcanic gniewoszow metarhyolite was dated at 501 3 ma finally the cinawica subvolcanic rhyolite yielded an igneous emplacement age of 338 3 ma and a large population of inherited zircons dated at palaeoproterozoic neoproterozoic cambro ordovician and late devonian early carboniferous the dated samples come from two adjacent suspect terranes the orlica nieznik dome and the klodzko massif in the central sudetes that are characterised by contrasting timing of metamorphism and exhumation despite this difference the results obtained show in conjunction with earlier data a similar provenance of the studied units and their common affinity to the saxo thuringian terrane since the central sudetes are separated from saxo thuringia by a collisional suture the pre variscan rocks must represent the deformed and metamorphosed allochthonous equivalents to saxo thuringian lithologies they were probably subducted together with the saxo thuringian passive margin during a variscan collision and then exhumed within an accretionary wedge in front of brunia east avalonia the central sudetic suspected terranes must have been derived from a dismembered single accretionary complex and were then juxtaposed by strike slip faults

late holocene post 4000 years bp coastal dune development in northumberland northeast england the recent environmental history of coastal dune systems in northumberland northeast england has been examined using geomorphological stratigraphical and sedimentological techniques linked to radiocarbon and infrared stimulated luminescence irsl dating stratigraphies were determined from 22 vibracores and three sections and dune chronology was based on 28 14 c dates from peat and soil organic horizons and 26 irsl dates on k feldspar grains from within sand layers almost all dune systems are associated with regressive shorelines consequent upon a fall in relative sea level rsl from its holocene peak and indicate rsl functioned as a macroscale control on dune development where dunes are anchored on terrestrial sediment dune expansion may have been either transgressive or regressive in nature where near shore marine sediments form the dune substrate a regressive prograding dune model seems most likely most dune building occurred during the little ice age lia probably in a

ordovician passive continental margin magmatism in the central european variscides u pb zircon data from the se part of the karkonosze izera massif sudetes sw poland approximately 500 ma old orthogneisses are widespread in the eastern part of the variscan belt and are commonly interpreted to have intruded mica schist series of assumed neoproterozoic age new shrimp zircon ages of quartzofeldspathic metavolcanogenic rocks of the mica schist series in the eastern part of the karkonosze izera massif sw poland indicate that they are late cambrian early ordovician rather than neoproterozoic in age based on the zircon age spectra distributed mainly between ca 500 and 660 ma with a few proterozoic inherited minimum ages of ca 970 and 1 825 ma younger zircon dates dispersed between ca 412 and 464 ma are interpreted as a result of pb loss likely caused by subsequent metamorphism consequently the felsic metavolcanogenic rocks appear to be roughly contemporaneous with the intrusion of ca 500 ma old orthogneiss protoliths with the pooled concordia age of 487 8 ma interpreted as the best approximation of the protolith intrusive age field relationships petrological and geochemical features of the felsic and mafic rocks studied support a model in which the accompanying mica schist series are not the original country rocks to the ca 500 ma granite intrusions and indicate that their recent close proximity is the result of tectonic juxtaposition however both the mica schists enclosing the bimodal metavolcanic rocks and the orthogneisses are interpreted to represent a cambro ordovician passive continental margin sequence being part of the saxothuringian domain they are tectonically overlain to the east by hp t metamorphic units comprising morb type metaigneous rocks and delineating a tectonic suture separating the saxothuringian block in the west from an assumed continental block tepla barrandian to the south east

ground penetrating radar and its use in sedimentology principles problems and progress abstract ground penetrating radar gpr also referred to as ground probing radar surface penetrating radar subsurface radar georadar or impulse radar is a noninvasive geophysical technique that detects electrical discontinuities in the shallow subsurface

decadal scale variation in dune erosion and accretion rates an investigation of the significance of changing storm tide frequency and magnitude on the sefton coast uk abstract monitoring of frontal dune erosion and accretion on the sefton coast in northwest england over the past 50 years has revealed significant spatial and temporal variations previous work has shown that the spatial variations primarily reflect longshore differences in beach and nearshore morphology energy regime and sediment budget but the causes of temporal variations have not previously been studied in detail this paper presents the results of work carried out to test the hypothesis that a major cause of temporal variation is changes in the frequency and magnitude of storms surges and resulting high tides dune toe erosion accretion records dating from 1958 have been compared with tide gauge records at liverpool and heysham relatively high dune erosion rates at formby point 1958 1968 were associated with a relatively large number of storm tides slower erosion at formby and relatively rapid accretion in areas to the north and south occurred during the 1970 s and 1980 s when there were relatively few major storm tides after 1990 rates of dune erosion at formby increased again and dunes to the north and south experienced slower accretion during this period high storm tides have been more frequent and the annual number of hours with water levels above the critical level for dune erosion has increased significantly an increase in the rate of mean sea level rise at both liverpool and heysham is evident since 1990 but we conclude that this factor is of less importance than the occurrence of extreme high tides and wave action associated with storms the incidence of extreme high tides shows an identifiable relationship with the lunar nodal tidal cycle but the evidence indicates that meteorological forcing has also had a significant effect storms and surges in the eastern irish sea are associated with atlantic depressions whose direction and rate of movement have a strong influence on wind speeds wave energy and the height of surge tides however preliminary analysis has indicated only a modest relationship between dune erosion accretion rates and the north atlantic oscillation index

the climate archive dune sedimentary record of annual wind intensity active dunes contain an unread high resolution archive of past wind strength variations in the grain size spectrum of an active dune through time are compared with historical time series of wind speed annually averaged sediment derived wind intensity and instrumental records of wind speed show a correlation as high as 0 75 the potential of eolian dunes to gain long term data series of wind intensity in areas and for time periods lacking an instrumental record is demonstrated by reconstructing 20th century wind intensity variations in the southern north sea area the approach can be used in both recent and fossil dune systems potential applications include the validation of climate models the reconstruction of supraregional wind systems and the monitoring of future shifts in the climate system

8000 years of environmental evolution of barrier lagoon systems emplaced in coastal embayments nw iberia the rocky and indented coast of nw iberia is characterized by the presence of highly valuable and vulnerable small and shallow barrier lagoon systems structurally controlled the case study was se

detrital zircon populations in quartzites of the krkonose jizera massif implications for pre collisional history of the saxothuringian domain in the bohemian massif age spectra of detrital zircons from metamorphosed quartzites of the krkonose jizera massif in the northeastern part of the saxothuringian domain were obtained by u pb laser ablation inductively coupled plasma mass spectrometry dating the zircon ages cluster in the intervals of 450 530 ma and 550 670 ma and show individual data between 1 6 and 3 1 ga zircons in the analysed samples are predominantly of cambrian ordovician and neoproterozoic age and the marked peak at c 525 500 ma suggests a late cambrian maximum age for the sedimentary protolith detritus of the quartzites probably originated from the erosion of cambrian ordovician granitoids and their neoproterozoic meta sedimentary or magmatic country rocks the lack of neoproterozoic meta sedimentary rocks in the central and eastern part of the krkonose jizera massif suggests that the country rocks to voluminous cambrian ordovician magmatic bodies were largely eroded during the formation of early palaeozoic rift basins along the southeast passive margin of the saxothuringian domain the detrital zircon age spectra confirm the previous interpretation that the exposed basement dominated by neoproterozoic to cambrian ordovician granitoids was overthrust during devonian carboniferous subduction collision processes by nappes composed of metamorphosed equivalents of the uppermost cambrian devonian passive margin sedimentary formations only a negligible number of mesoproterozoic ages typically from the grenvillian event supports the interpretation that the saxothuringian neoproterozoic basement has an affinity to the west african craton of the northwestern margin of gondwana

location of the rheic suture in the eastern bohemian massif evidence from detrital zircon data introductionthe variscan orogen of europe con tains a collection of terranes that weredispersed along the northern marginof west gondwana in the late neo proterozoic and early palaeozoic e g murphy et al 2002 linnemannet al 2007 nance et al 2008 theseperi gondwanan terranes show anumber of common features as 1 voluminous late neoproterozoic c 640 550 ma arc magmatism 2 extensive volcano sedimentary succes sions of cogenetic arc related basins 3 a widespread cadomian unconfor mity separating deformed precam brian rock units from their earlypalaeozoic cambro ordovician overstep sequence and 4 an overlyingearly middle cambrian shallow marine platform e g murphy andnance 1989 nance et al 1991 2002 the peri gondwanan terranesrepresent dismembered fragments ofthe avalonian cadomian orogenthat was formed in the late neoprote rozoic c 700 540 ma at the north ern edge of gondwana e g nanceet al 2002 linnemann et al 2007 in the early palaeozoic several peri gondwanan terranes were separatedfrom west gondwana e g avalonia while others including the cadomianterranes remained attached togondwana and were accreted intothe appalachian variscan orogenwith the closure of the rheic ocean inthe late palaeozoic e g linnemannet al 2004 nance et al 2008 pres ently the cadomian terranes areincluded within the variscan belt ofeurope as separate blocks that stretchout from the iberian massif to thesaxo thuringian and tepla barran dian zones fig 1 e g linnemannet al 2008 nance et al 2008 the occurrences of neoproterozoicrocks have long been known from thecentral sudetic segment of the easternvariscides fig 2 although their pre cise age and provenance remainedunclear e g aleksandrowski and ma zur 2002 only recently jastrze bskiet al 2010 reported from the orlica s nieznik dome in the central sudetes a metamorphosed volcano sedimen tary succession continuing from thelate neoproterozoic into the early pal aeozoicwithoutacadomianunconfor mity if uninterrupted sedimentationwas actually the case across theneoproterozoic palaeozoic boundary c 542 ma the orlica s nieznik dome would lack a cadomian a nity con sequently the central sudetes wouldrepresent an exotic terrane insertedbetween the cadomian terranesand east avalonia in such a case existing plate tectonic models for theclosure of the rheic ocean wouldrequiresubstantialrevision in this article we present new sen sitive high resolution ion micro probe shrimp u pb data fordetrital zircon grains to constrain theage and provenance of selectedmetasediments from the orlica s nieznik dome fig 2 these geo chronological data in combinationwith eld relations and publishedresults are used to identify the plate tectonic setting s of neoproterozoicto cambro ordovician rock units ofthe orlica s nieznik dome we then compare the new results with theneoproterozoic to early palaeozoicstratigraphy of the saxo thuringianzone to test the cadomian a nity ofthe central sudetes our goal is toconstrain the eastern extent of thecadomian terranes and the location ofthe rheic suture in central europe geological settingthe orlica s nie znik dome fig 2 isdominated by amphibolite grade or thogneiss locally containing lenses of u hp rocks alternating with belts ofstaurolite grade supracrustal rocks don et al 1990 the orthogneiss istraditionally subdivided into two maintextural varieties fig 2 the por phyric augen to banded s nieznik abstract

magnetostratigraphy of the middle miocene continental sedimentary sequences of the mae moh basin in northern thailand evidence for counterclockwise block rotation abstract a magnetostratigraphic study has been performed on the mae moh basin well known for its lignite mining in the lampang province paleomagnetic samples were collected from 66 stratigraphic levels rock magnetic investigations indicate the presence of low coercivity minerals specimens subjected to progressive thermal or alternating field demagnetization procedures show that nearly all of them exhibit a low temperature magnetization component and a high temperature characteristic component chrm with either positive or negative virtual geomagnetic pole latitudes and opposite polarity considered as the characteristic miocene magnetization the overall mean paleomagnetic direction incl 22 2 decl 358 3 15 95 4 documents a counterclockwise vertical axis rotation of about 13 1 32 with respect to the expected miocene direction derived from the eurasian polar wander curve incl 42 decl 11 our paleomagnetic results are not consistent with the previously reported paleomagnetic data the rotation observed in the mae moh basin can be the response to local tectonics a section sampled for magnetostratigraphy reveals a polarity sequence of nine magnetozones that can reliably be correlated to the geomagnetic polarity time scale according to biochronological constraints the magnetostratigraphic results from the mammal bearing succession correlate with chron c5abn c5an2n between 13 5 and 12 1 ma according to the mean sedimentation rate of about 17 5 cm ka ages of 12 5 and 12 8 ma are proposed for the fossiliferous levels j5 and k1 k2 lignite zones were the mammal remains were found

magnetostratigraphy of the miocene chiang muan formation northern thailand implication for revised chronology of the earliest miocene hominoid in southeast asia abstract a paleomagnetic study has been conducted on the miocene chiang muan formation in northern thailand in order to provide a chronology for the earliest large bodied miocene hominoid in southeast asia the chiang muan formation is mainly composed of clay silt and sand beds indicating lacustrine and fluvial environments paleomagnetic samples were collected from 124 horizons along an approximately 150 m thick section from the chiang muan formation at the opencast chiang muan mine rock magnetic experiments and stepwise thermal demagnetizations revealed that the main carrier of the magnetization of the sediments is magnetite and the samples have stable magnetization exceptionally stable magnetization is also carried by hematite which is represented by red colored sediments characteristic remanent magnetization chrm directions calculated by the principal component analysis revealed normal or reversed polarities of magnetization which allow the application of the reversal test of mcfadden and mcelhinny mcfadden p l mcelhinny m w 1990 classification of the reverse test in paleomagnetism geophys int 103 725 729 the mean paleomagnetic directions of the normal and reversed polarities passed the reversal test with a classification c indicating that the chiang muan formation preserved the primary magnetization in total five normal and four reversed polarity zones are recognized from the studied section based on paleontological age constraints this magnetostratigraphic column of the chiang muan formation correlates best with chron c5aan c5n of the geomagnetic polarity time scale gpts from the geological time scale gts2004 developed by gradstein et al gradstein f ogg j smith a eds 2004 a geological time scale 2004 cambridge univ press cambridge uk p 589 this correlation revealed that sedimentation of the chiang muan formation began approximately at 13 ma and continued until 9 8 ma with a mean sedimentation rate of approximately 4 2 cm ky the age of the earliest southeast asian hominoid is between 12 4 and 13 0 ma

dating of detrital zircons and tracing the provenance of quartzites from the bystrzyckie mts implications for the tectonic setting of the early palaeozoic sedimentary basin developed on the gondwana margin we studied the petrographical characteristics and bulk chemical composition along with the age of detrital zircon grains from quartzites exposed in the western part of the orlica nieznik dome in the saxothuringian zone age spectra of detrital zircons were obtained by u pb laser ablation inductively coupled plasma mass spectrometry dating the zircon ages define a few clusters of which the most numerous are cambro ordovician and neoproterozoic and less frequent are paleoproterozoic and archean a distinctive feature of the investigated samples is the lack of mesoproterozoic zircon grains the youngest age cluster documented in the investigated quartzites points to a late cambrian maximum depositional age and detritus derivation from erosion of cambro ordovician metagranitoids bulk chemical composition of the quartzites indicates that they originated owing to erosion of granite within sedimentary basins developed on a passive continental margin presented data prove the similarity of the examined rocks to quartzites known from the eastern part of the orlica nieznik dome and quartz metasandstones documented in other parts of the variscan belt of europe known as the armorican quartzites or their equivalents exposed in the saxothuringian zone our results support the suggestion that the orlica nieznik dome has an affinity to the west african craton of the gondwana margin and represents a fragment of the saxothuringian zone

the impact of north atlantic storminess on western european coasts a review abstract instrumental and documentary records of storminess along the atlantic coast of western europe show that storm activity exhibits strong spatial and temporal variability at annual and decadal scales there is evidence of periods of increased storminess during the little ice age lia ad 1570 1990 and archival records show that these periods are also associated with sand movement in coastal areas independent evidence of sand movement during the lia is derived from dating the coastal sand deposits using luminescence or radiocarbon methods the holocene record of sand drift in western europe includes episodes corresponding to periods of northern hemisphere cooling particularly at 8 2 ka and provides the additional evidence that these periods like the lia were also stormy

form flow interactions of an aeolian saucer blowout airflow patterns through a saucer blowout are examined from wind speed and direction measurements made during a chinook wind event the blowout long axis is oriented east west with a broad depositional apron on the east side wind directions during the event rotated from south westerly to westerly permitting an assessment of oblique and axis parallel flows results show that airflow passing over the windward rim of the saucer blowout expands and decelerates leading to flow separation and a small re circulation zone on sheltered lee slopes near the deflation basin airflow re attaches to the blowout surface and accelerates up to a small opening in the east rim where it can be up to 50 faster than on the windward edge beyond the downwind rim the airflow expands and decelerates and sand is deposited onto a broad apron similar to coastal trough blowouts the degree of airflow steering and acceleration along the deflation basin is determined by the angle of incidence between the approach wind and the long axis of the blowout as the angle of incidence increases wind speed accelerates at 0 3 m above the surface of the deflation basin and the degree of airflow steering increases overall a two fold process is identified where south westerly flows have greater potential for eroding the deflation basin while westerly flows have greater potential for evacuating sand from within the blowout visual observations indicate that sand eroded from the deflation basin during south westerly flows is re distributed to adjacent zones of low wind speed until axis parallel winds evacuate the sand through the opening in the east rim morphometric changes since 1994 indicate that the blowout morphology has remained relatively constant suggesting a persistent interplay between oblique and axis parallel wind erosion events collectively these findings indicate that the angle of approach winds is an important control on saucer blowout morphodynamics copyright 2009 john wiley sons ltd

the late holocene coastal dunefield at vejers denmark characteristics sand budget and depositional dynamics abstract the coastal dunefield at vejers west coast of jutland which is now stabilized by vegetation covers an area of approximately 120 km 2 and occurs in a very high energy wind regime along the coastline a narrow belt of 5 15 m high dune ridges occur the dune ridges are gradually replaced inland by 10 20 m high parabolic or irregular dune forms in the central part of the dunefield a large aeolian sand plain ca 50 km 2 occurs at the windward side of a large and up to 20 m high parabolic dune the 3d structure of the dunefield deposits have been studied by geomorphological analysis sedimentological facies analysis of borings trenches and natural exposures and most importantly by georadar mapping the aeolian deposits which overlie a middle to late holocene barrier spit depositional system can be divided into a lower unit that drapes the underlying barrier system topography and an upper unit that includes the present dunes the boundary between the two aeolian units is a well developed phragmites peat the lower aeolian unit is composed of two aeolian subunits separated by an organic rich horizon also the upper unit is composite and composed of a basal aeolian sand cover and overlying dune or sand plain deposits the dune deposits locally are composed of up to four depositional subunits separated by immature soils the base of the lower aeolian unit formed around 300 a d whereas the phragmites peat at the base of the upper aeolian unit has been dated to ca 1000 a d from historical sources we know that the present dunefield primarily formed between 1550 and 1850 a d the sand content in the upper unit is estimated to 550 10 6 m 3 which yields sand transport rates between 25 m 3 m width 1 yr 1 accumulation in 1000 years and 83 m 3 m width 1 yr 1 accumulation in 300 years the sand in the dunefield originated from beach deposits a large but pulsating supply of sand was supplied to the beaches by southwards running coastal currents the composition of the vejers dunefield deposits indicate that periods of dunefield growth alternated with periods of dunefield stabilization during the last ca 1700 years the final and most important phase of dunefield growth took place during the little ice age this period was characterized by an overall cold and stormy climate and a relative low sea level and resulted in an increased availability of sand in the shorezone and a high influx of sand into the dunefield short periods of decreased storminess are recorded by the immature soils dunefield growth prior to 1000 a d was also linked to cold and stormy climatic intervals

forearc deformation and strain partitioning during growth of a continental magmatic arc the northwestern margin of the central bohemian plutonic complex bohemian massif abstract the late devonian subduction followed by the early carboniferous continental collision of the saxothuringian and overriding upper crustal tepla barrandian units led to the growth of a large magmatic arc the 354 337 ma central bohemian plutonic complex in the central part of the bohemian massif far field tectonic forces resulting from the collision produced wnw ese to nw se regional shortening across the forearc upper crust above the subduction zone the shortening was accommodated by predominantly top to the ese tectonic transport along the southeastern flank of the tepla barrandian unit approaching the magmatic arc margin the regional structural pattern changes and exhibits significant across and along strike variations interpreted as a result of strain partitioning where the saxothuringian tepla barrandian convergence interacted in different ways with the intruding magma pulses around the voluminous northeasterly 354 ma sazava pluton the principal shortening was at high angle to the forearc facing intrusive contact and the host rocks were significantly thermally softened the regional top to the ese tectonic transport converted here into arc parallel ductile flow within the structural aureole around and above the pluton in contrast a narrow to nonexistent ductile strain aureole is preserved in the host rocks around discordant sheet like plutons the southwesterly pre 354 ma marginal granite and the milin granodiorite of unknown radiometric age our ams study of the marginal granite and milin granodiorite and mapping of mesoscopic magmatic foliations and lineations in another neighboring sheet like pluton the 346 ma kozarovice granodiorite reveals sigmoidal map scale fabric patterns consistent with dextral transpression we thus suggest that the thin sheet like plutons were oriented obliquely to the principal shortening and were rheologically weaker than the host rocks prior to final crystallization producing dextral transpression recorded by the internal fabrics of these plutons our study shows that the far field plate kinematics during pluton emplacement is not the only factor that controls strain partitioning in continental magmatic arcs the two contrasting styles of pluton emplacement documented here indicate that the pluton shape orientation of intrusive contacts with respect to the background plate convergence vector and heat budget of intrusions magma volume composition and proportion of hot mantle component may also govern strain partitioning

sedimentary evidence of landscape and climate history since the end of mis 3 in the krkonose mountains czech republic abstract a sedimentary core recovered from the cirque basin of labsk d l valley 1039 m a s l in the krkonose mountains reflects the environmental history for approximately the last 30 000 years analyses of magnetic susceptibility carbon content pollen assemblages and macrofossil data in a 15 m thick sediment sequence provide the first continuous record of lateglacial and holocene vegetation history in sudetes region of the czech republic the succession of sedimentary units in the lower part of the core suggests that the cirque was ice free before the onset of the last glaciation at the beginning of marine isotope stage 2 highly variable climate prevailed during this period with cold conditions culminating about 18 cal ka bp cold climates persisted until the lateglacial period evidenced by an identified warming and subsequent cooling event correlated with the younger dryas period sparse treeless vegetation dominated in the catchment area at that time the sequence of interrupted thinly laminated silts reflects the retreat and temporary readvance of a local glacier in the cirque during 12 5 10 8 cal ka bp subsequently the alpine treeline ecotone gradually shifted above the cirque floor palaeoclimatic conditions in the early holocene fluctuated strongly whereas since 5 1 cal ka bp conditions have been more stable pollen based climate reconstructions suggest significant cooling at around 9 8 9 3 7 7 7 5 and 4 0 3 3 cal ka bp spruce forests have dominated the site since 5 0 cal ka bp when the vegetation became similar to the modern one two phases of increased sedimentation were identified within the holocene culminating about 9 2 7 5 cal ka bp and 5 8 5 5 cal ka bp sediment yield was as high as 2 4 mm yr 1 during the period reflecting environmental changes during the atlantic sub boreal transition

shrimp zircon study of a micromonzodiorite dyke in the karkonosze granite sudetes sw poland age constraints for late variscan magmatism in central europe the large variscan karkonosze granite in the west sudetes representative of the vast variscan granite plutonism in central europe and located adjacent to regional tectonic suture and strike slip zones has been difficult to date precisely a range of published data varies between c 304 and 328 ma however the granite is cut by locally numerous lamprophyre and other dykes dating of the dyke rocks emplaced shortly after the granite intrusion and cooled more rapidly provides a promising tool for the verification of published shrimp results on the granite itself shrimp zircon geochronology of a studied micromonzodiorite dyke indicates substantial admixture of inherited zircons of c 2 0 1 4 ga 207 pb 206 pb minimum ages and c 570 and 500 ma the average concordia age of the main magmatic population of the zircons in the dyke is 313 3m a 2 however the true magmatic age might be older around 318 ma this would constrain the age of the hypabyssal magmatism in the karkonosze massif and the minimum age of the host karkonosze granite thus the karkonosze granite is confirmed as representative of an early phase of variscan granite plutonic activity in the central european variscides

storminess and vulnerability along the atlantic coastlines of europe analysis of storm records and of a greenhouse gases induced climate scenario abstract identification of the distinctive circulation patterns of storminess on the atlantic margin of europe forms the main objective of this study dealing with storm frequency intensity and tracking the climatology of the extratropical cyclones that affect this region has been examined for the period 1940 1998 coastal meteorological data from ireland to spain have been linked to the cyclone history for the north atlantic in the analysis of storm records for european coasts the study examines the evolution in the occurrence of storms since the 1940s and also their relationship with the north atlantic oscillation nao results indicate a seasonal shift in the wind climate with regionally more severe winters and calmer summers established this pattern appears to be linked to a northward displacement in the main north atlantic cyclone track an experiment with the echam4 a gcm at high resolution t106 has also been used to model the effect of a greenhouse gases induced warming climate on the climatology of coastal storms in the region the experiment consists of 1 a 30 year control time slice representing present day equivalent co 2 concentrations and 2 a 30 year perturbed period corresponding to a time when the radiative forcing has doubled in terms of equivalent co 2 concentrations the boundary conditions have been obtained from an atmosphere ocean coupled oa gcm simulation at low horizontal resolution an algorithm was developed to allow the identification of individual cyclone movements in selected coastal zones for most of the northern part of the study region covering ireland and scotland results describe the establishment by ca 2060 of a tendency for fewer but more intense storms the impacts of these changes in storminess for the vulnerability of european atlantic coasts are considered for low lying exposed and soft sedimentary coasts as in ireland these changes in storminess are likely to result in significant localised increases in coastal erosion

a complete magnetic polarity stratigraphy of the miocene continental deposits of mae moh basin northern thailand and a reassessment of the age of hominoid bearing localities in northern thailand northern thailand comprises more than 40 tertiary intermontane basins these basins tectonically interpreted as grabens or half grabens have yielded hominoid fossils and rich neogene mammal faunas relative ages provided by biochronological studies are controversial and neither absolute ages nor correlations with marine deposits are available a precise temporal framework provided by magnetic polarity stratigraphy is therefore crucial to understand the evolution of these southeast asian mammalian faunas to estimate the timing and duration of basin formation and finally to allow correlations with other neogene hominoid localities of the old world a complete magnetostratigraphic study which significantly extends previous paleomagnetic investigations has been conducted in the miocene sequence of mae moh basin lampang province northern thailand based on the biostratigraphic constraints the 15 polarity zones recognized from the composite section have been correlated with chrons c5acr c5r 3r between 14 1 and 12 0 ma the present study provides a high resolution magnetostratigraphic reference for the continental middle miocene of all southeast asia by correlation with the miocene sequence of the nearby basin of chiang muan the large bodied hominoid khoratpithecus chiangmuanensis bearing levels can be precisely dated between 12 4 and 12 2 ma

the izera metabasites west sudetes poland geologic and isotopic u pb zircon evidence of devonian extension in the saxothuringian terrane abstract in the lausitz izera massif of the saxothuringian terrane part of the central european variscides 515 480 ma metagranites have been intruded by a swarm of basic veins that have within plate alkali basalt geochemistry or rarely normal mid ocean ridge basalt n morb geochemistry based on their spatial orientation distribution in the region and structural relationships to the host metagranites these basic veins could be grouped into three types that displayed six varieties of host vein contacts zircons extracted from eight of the basic veins revealed that there were two populations clear zircons and brown zircons each type were subjected to both single grain conventional u pb analysis and to sensitive high resolution ion microprobe shrimp u pb analysis the clear grains yielded ages 480 ma clustering at 500 ma the brown grains yielded ages between 390 and 365 ma clustering at 370 ma the colourless zircons possess an oscillatory zoned structure and rare earth element ree distribution pattern that suggests they come from the host granites and from deeper neoproterozoic granitoid basement however the basic host rocks show almost no obvious contamination by felsic material the turbid brown grains which are dark under cathodoluminescence also seem to be mainly magmatic because of their internal structures high th u ratios and ree pattern when the zircon results are integrated into the regional geology an 30 m y period of episodic intra plate predominantly alkaline basic magmatism at the passive margin of the saxothuringian terrane is suggested with maximum activity at 370 ma during an extensional regime combining the factors of the relatively high thermal gradient during early metamorphism of the metabasites 450 c 2 kbar the geology of saxothuringia and the regional structural data we propose a plume model of hot fingers type whereby the basic magmatism of the izera region was due to repeated devonian intrusions derived from garnet bearing enriched oib type and less commonly depleted asthenosphere sources the waning stages of this activity were coeval with the early deformation of the izera granite host basic vein system and matched by rifting and extensional widening of the saxothuringian basin in its izera kaczawa segment

foredunes and blowouts initiation geomorphology and dynamics this paper reviews the initiation dynamics geomorphology and evolution of incipient foredunes established foredunes and blowouts incipient foredunes may be initiated in a variety of ways leading to the formation of ramps terraces or ridges depending on progradation rates vegetation type and cover sediment transport rates and scale of erosional processes vegetation cover morphology growth rates and types combine with aerodynamic processes to determine dune and swale morphology established foredunes are classified into five morpho ecological types and the flow behaviour over two types is detailed a new model of foredune evolutionary paths at various possible time scales is presented blowout initiation dynamics and sediment transport and evolution is examined throughout the review the gaps in present understanding of dune processes and a range of ideas for new research possibilities are provided

the tepla saxothuringian suture in the karkonosze izera massif western sudetes central european variscides the southern and eastern karkonosze izera massif northern bohemian massif exposes blueschist facies rocks and morb type magmatic complexes during late devonian to early carboniferous times these were overthrust within a nappe pile toward the nw onto the pre variscan saxothuringian basement composed of the izera kowary metagranitoids and their envelope the lowermost nappe or parautochthonous unit of the pile is the low grade metamorphosed jest d complex comprising a devonian to early carboniferous sedimentary succession of the saxothuringian passive margin this is tectonically overlain by the south karkonosze complex which represents ordovician silurian volcano sedimentary infill of the saxothuringian basin affected by late devonian hp metamorphism the uppermost nappe is the early palaeozoic epidote amphibolite grade leszczyniec morb like complex cropping out on the eastern margin of the karkonosze izera massif it probably represents a fragment of obducted saxothuringian basin floor the nappe pile was stacked beneath the overriding upper plate margin now concealed below the intra sudetic basin and hypothesized to represent a fragment of the tepla barrandian terrane the nappe stacking triggered by buoyancy controlled upward extrusion of the subducted continental slab was the main mechanism for the exhumation of hp rocks the final stages of the nw ward nappe stacking were accompanied and followed by se directed early carboniferous extensional collapse the lower plate of the suture zone was uplifted at that time and intruded by the 330 ma old nearly undeformed karkonosze granite pluton as a result of the collapse the tepla barrandian upper plate was downthrown on shear zones and brittle faults and buried under several km thick synorogenic late tournaisian through namurian and post orogenic late carboniferous early permian succession of the intra sudetic basin the south and east karkonosze suture most probably is a fragment of the tepla saxothuringian munchberg tepla suture belt known from the western bohemian massif

chronology of the eocene continental deposits of africa magnetostratigraphy and biostratigraphy of the el kohol and glib zegdou formations algeria despite numerous discoveries that have considerably enriched the african arabian tertiary fossil record over the last decades our knowledge of the evolutionary history of many continental african vertebrate groups during the paleogene period remains inadequate particularly when it is compared with the fossil records of europe or north america the eocene epoch in africa is especially poorly documented being restricted to few fossiliferous localities our understanding of the early tertiary emergence diversification and paleobiogeographic history of african arabian mammals has been further hindered by the lack of a precise temporal framework for these sites we conducted magnetostratigraphic analyses associated with biostratigraphic studies in the fossiliferous sequences exposed in the northwestern hammadas of the saharan platform in the glib zegdou area and in the saharan atlas at the el kohol locality algeria to further define the age of these eocene continental deposits based on biostratigraphic constraints the six polarity zones identified in the el kohol section can be correlated with chrons c24n to c22r providing the first direct age estimates for the el kohol fossiliferous strata between 52 and 51 ma correlation to the geomagnetic polarity time scale using previously published biostratigraphic data for the glib zegdou fauna suggests an age ranging between 49 and 45 ma for this section the high resolution magnetostratigraphic study of the poorly known continental eocene epoch of algeria provides new insights into the early tertiary stratigraphy of northwest africa the placement of the algerian localities into a consistent chronological framework constitutes considerable advancement to achieve biostratigraphic correlation of the paleogene african arabian mammal localities

late holocene sand invasion and north atlantic storminess along the aquitaine coast southwest france holocene forested coastal dunes of different morphology fringe the atlantic coast of southwest aquitaine infra red stimulated luminescence irsl dating has been applied to sands from these dunes in the aquitaine region in order to test the validity of dune classification theories the ages obtained from the dunes show three phases of sand invasion and dune development during the late holocene 3000 4000 years ago 900 1300 years ago 250 550 years ago the timing of the most recent phase of sand mobilization as dated by irsl is supported by historical maps and records from the fifteenth to the eighteenth centuries ad showing problems for human settlement in the region and village abandonment due to dune drift sand invasion is driven by an increase in frequency of severe storms in the north atlantic associated with the cooler periods of the little ice age and early mediaeval warm period the dunes emplaced 900 1300 years ago were naturally fixed by a mixed deciduous and maritime pine forest durin

boundaries of mantle lithosphere domains in the bohemian massif as extinct exhumation channels for high pressure rocks abstract five domains microplates have been recognized by seismic anisotropy in the mantle lithosphere of the bohemian massif the mantle domains correspond to major crustal units and each of the domains bears a consistent fossil olivine fabric formed before their variscan assembly the present day mantle fabric indicates that this process consisted of at least three oceanic subductions each followed by an underthrusting of the continental lithosphere the seismic anisotropy does not detect remnants of the oceanic subductions but it can trace boundaries of the preserved continental domains subsequently underthrust along the paths of previous oceanic subductions the most robust continent continent collision was followed by westward underthrusting of the brunovistulian mantle lithosphere still detectable by seismic anisotropy more than 100 km beneath the moldanubian mantle lithosphere major occurrences of the high pressure ultra high pressure hp uhp rocks follow the ene and nne oriented sutures and boundaries of the mantle lithosphere domains mapped from three dimensional modeling of body wave anisotropy the hp uhp rocks are products of oceanic subductions and the following underthrusting of the continental crust and mantle lithosphere exhumed along the mantle boundaries the close relation of the mantle sutures and occurrences of the hp uhp rocks near the paleosubductions testifies for models interpreting the granulite garnet peridotite association by oceanic continental subduction underthrusting followed by the exhumation of deep seated rocks our findings support the bivergent subduction model of tectonic development of the central part of the bohemian massif the inferences from seismic anisotropy image the bohemian massif as a mosaic of microplates with a rigid mantle lithosphere preserving a fossil olivine fabric the collisional mantle boundaries blurred by tectonometamorphic processes in easily deformed overlying crust served as major exhumation channels of the hp uhp rocks

uplift of the hengduan mountains on the southeastern margin of the tibetan plateau in the late miocene and its paleoenvironmental impact on hominoid diversity abstract the southeastern margin of the tibetan plateau has a number of well known late miocene localities that have yielded fossil hominoids belonging to lufengpithecus and khoratpithecus these localities provide critical evidence about the evolutionary history of hominoids including their response to environmental changes associated with uplift of the tibetan plateau here we present magnetostratigraphic dating of the baoshan hominoid locality in yunnan southwestern china which based on preliminary biochronological evidence was previously assumed to be the youngest known miocene hominoid locality in eurasia paleomagnetic investigations yield three normal and three reversed magnetozones which can be best correlated in conjunction with biostratigraphic constraints to chrons c3n 4n to c3ar the baoshan hominoid is derived from a horizon correlated with the lowest part of c3r having an estimated age of 6 0 ma this indicates that the baoshan hominoid is slightly younger than l cf lufengensis from zhaotong dated to 6 2 ma and l lufengensis from lufeng dated to 6 9 6 2 ma our results coupled with previously published magnetochronology indicate that hominoids occurred in southeast asia from the latest middle miocene to the terminal miocene 13 6 ma the period after 6 ma coincides with the uplift of the hengduan mountains especially the gaoligong mountain we propose that the late miocene uplift of these n s oriented mountains on the southeastern margin of the tibetan plateau created a barrier to the warm and moist indian monsoon from the west and this led to a cooler and drier climate in the southeastern margin of the tibetan plateau this paleoenvironmental change potentially had a profound impact on the diversity of the hominoid community in southwestern china and southeast asia

origin and evolution of playas and blowouts in the semiarid zone of tierra de pinares duero basin spain abstract a large number of blowouts and playas occur in the marginal sectors of the aeolian deposits located in the southern sector of the duero depression tierra de pinares in spain the blowouts are relict landforms that were developed on sand sheets by deflation during dry periods with lower vegetation cover and a deeper water table the studied blowouts form complexes of nw se and nnw sse elongated hollows with accompanying dunes up to 4 km long in the leeward margins some hollows host lakes or swampy areas related to a shallow water table the dunes formed by ne ene winds show steep windward slopes and gentle leeward slopes the studied playas with prevalent nnw sse orientations result from the aeolian excavation of terrace deposits and the underlying marly bedrock it is probable that the formation of these depressions in an initial stage was related to deflation processes affected preferentially nnw sse sandy channels perpendicular to the dominant wind direction the precipitation of salts in the playas generates aggregates of clay particles peloids that are easily removed by the wind once the bottom reached the substratum the deepening of the depressions progressed by the deflation of particles produced by weathering of the argillaceous bedrock

migration of parabolic dunes at aberffraw anglesey north wales abstract aberffraw is a 1 km wide and 3 km long transgressive dunefield that extends inland along a northeast southwest trending valley from a southwest facing beach traeth mawr the prevailing wind is from the southwest and both the parabolic dunes and the valley within which they lie are sub parallel to the prevailing wind the dunefield at aberffraw includes two foredune ridges and three rows of active compound parabolic dunes at the landward end is a lake llyn coron which has been formed by dunes migrating up the valley and damming the river afon ffraw between the parabolic dunes are gently sloping interdune areas with a close cropped vegetation the parabolic dunes at aberffraw have been migrating inland across the interdune areas rates of parabolic dune migration are derived from three sets of aerial photographs taken in 1940 1982 and 1993 the aerial photographs have been scanned and manipulated in arcview gis software registration of the aerial photograph to an ordnance survey os map was performed using ground control points gcps common fixed features that are identifiable on both the aerial photographs and the baseline map attempts to correct for the inherent distortions of aerial photography were made during registration standardising the projection of the photographs to a common baseline allows meaningful spatial analysis and the dune ridges trailing edges and areas of bare sand were mapped from each photograph as a series of overlays rates of dune migration are calculated from the spatial distance between linear trend lines parallel to the dune crests and perpendicular to the dune migration orientation applied to sections of dune ridges for 1940 and 1993 trend lines were only fitted to sections where continuity of dune form was maintained over the given period the method provides an improved representation of the actual migration rate as it incorporates the whole of the parabolic dune form and the whole of the compound dune ridge form into the calculation it effectively measures the centre point or line of a dune or dune ridge as opposed to the variable positions and orientations of the dune crest noses which represent maximum migration rather than the mean rates of parabolic dune migration range from a minimum of 0 m year 1 to a maximum of 3 6 m year 1 with an average migration rate of 1 m year 1

ore mineralization related to geological evolution of the karkonosze izera massif the sudetes poland towards a model abstract the karkonosze izera massif is a large tectonic unit located in the northern periphery of the bohemian massif it includes the variscan karkonosze granite about 328 304 ma surrounded by the following four older units izera kowary the early paleozoic continental crust of the saxothuringian basin jest d the middle devonian to lower visean sedimentary succession deposited on the ne passive margin of the saxothuringian terrane out of the present study area southern karkonosze metamorphosed sediments and volcanics filling the saxothuringian basin out of the present study area leszczyniec early ordovician obducted fragment of saxothuringian basin sea floor the authors present a genetic model of ore mineralization in the karkonosze izera massif in which ore deposits and ore minerals occurrences are related to the successive episodes of the geological history of the karkonosze izera massif formation of the saxothuringian basin and its passive continental margin about 500 490 ma variscan thermal events regional metamorphism 360 340 ma karkonosze granite intrusion 328 304 ma late cretaceous and neogene to recent hypergenic processes the oldest ore deposits and ore minerals occurrences of the karkonosze izera massif are represented by pyrite and magnetite deposits hosted in the leszczyniec unit as well as by magnetite deposit and presumably by a small part of tin mineralization hosted in the izera kowary unit all these deposits and occurrences were subjected to the pre variscan regional metamorphism most of the karkonosze izera massif ore deposits and occurrences are related to the karkonosze granite intrusion this group includes a spatially diversified assemblage of small ore deposits and ore mineral occurrences of fe cu sn as u co au ag pb ni bi zn sb se s th ree mo w and hg located within the granite and in granite related pegmatites in the close contact aureole of the granite and within the metamorphic envelope at various distances from the granite assuming world standards all these deposits are now uneconomic various age determinations indicated that ore formation connected with the karkonosze granite might have taken place mostly between about 326 and 270 ma the last ore forming episode in the karkonosze izera massif is related to hypergenic processes particularly important in the northern part of the massif in the izera kowary unit where some uranium deposits and occurrences resulted from the infiltration of ore solutions that originated from the weathering of pre existing accumulations of uranium minerals a separate problem is the presence of oxidation zones of ore deposits and occurrences both the fossil and the recent a full list of ore minerals identified in described deposits and occurrences of the karkonosze izera massif together with relevant key references is presented in the form of an appendix

flow dynamics and geomorphology of a trough blowout the dynamics and geomorphological development of a trough blowout located at fiona beach in the myall lakes national park in nsw australia are examined wind speeds velocities and flow structure were measured utilizing an array of miniature rimco cup anemometers gill bivane and uvw instruments and wind vanes flow measurements indicate that when the wind approaches the trough blowout parallel to the throat orientation jets occur both in the deflation basin and along the erosional walls relative flow deceleration and expansion occurs up the depositional lobe jets are formed over the depositional lobe crest accompanied by downwind flow separation on the leeward side of the lobe and flow separation and the formation of corkscrew vortices occur over the crests of the erosional walls maximum erosion and transport occurs up the deflation basin and onto the depositional lobe trough blowout morphologies are explained as a function of these flow patterns when the wind approaches the blowout obliquely the flow is steered considerably within the blowout and the degree and complexity of topographic steering is dependent on the blowout topography the flow is usually extremely turbulent and large corkscrew vortices are common the local topography of a blowout can be very important in determining overall sand transport and blowout evolutionary conditions and paths estimates of potential sand transport within the blowout may be up to two orders of magnitude lower than actual rates if remotely sensed wind data are used

sediment supply from shoreface to dunes linking sediment transport measurements and long term morphological evolution a significant problem in current coastal research is the understanding of linkages between morphological phenomena occurring on different temporal and spatial scales morphodynamic processes in the nearshore typically exhibit nonlinear behaviour and consequently phenomena which occur on short temporal event scales as e g observed during field experiments have generally been difficult to upscale to provide an understanding of the long term behaviour of the coast on the time scale of seasons or decades this paper documents a persistent onshore migration of nearshore bar features over a period of 3 decades using a set of cross shore profile surveys from a barrier on the danish north sea coast the observed behaviour is consistent with experimental data obtained during weeklong field campaigns when sediment transport and bar migration were found to be landward directed during high energy dissipative conditions hydrodynamic and sediment transport processes leading to onshore bar migration and eventually welding of the bars are documented to provide an explanation for the observed long term evolutionary trends in addition bar welding and the resulting intertidal bar formation represent an onshore sediment storage which is subsequently available for aeolian transport observations on aeolian sediment transport indicate that transport rates and sediment supply to the foredunes critically depend on the presence of dry sand sources as represented by well drained intertidal bars measurements of long term accretion rates in foredunes indicate that volumes deposited on the crest and lee slope of the dunes are in reasonable correspondence with volumes supplied to the subaerial beach through the process of bar welding hence the data suggest that a persistent onshore directed sediment supply occurs from the shoreface across the surf and intertidal zones and into the dunes of the investigated barrier

blowout dynamics on lake huron sand dunes analysis of digital multispectral data from colour air photos abstract we adapted a digital image analysis procedure to extract multispectral data from sequential colour air photos of a lake huron sand dune system and then classify land cover into water sand and vegetation we isolated portions containing individual blowouts from georeferenced land cover maps of the dune system in 1973 and 1998 and overlaid the sequential images using geographic information systems gis this allowed us to quantify changes in blowouts over the 25 year period net change in land cover m 2 within each blowout was expressed as the difference between retrogression bare areas created by erosion or burial of existing vegetation and colonization vegetation patches created by plant establishment on bare areas the analysis procedure produced maps with an overall accuracy of 90 for land cover classification within blowouts the individual blowouts fell along a continuum of activity varying from significant retrogression 748 m 2 to significant colonization 1148 m 2 overall sand movement in all sampled blowouts produced 3991 m 2 17 9 of the blowout area in 1998 of bare sand patches that replaced formerly existing patches of vegetation colonization of bare areas over the 25 year period was 4127 m 2 or 18 5 of the 1998 blowout area retrogression and colonization are natural cooccurring processes in coastal dune systems and the technique described here represents a new tool for the study of temporal and spatial vegetation dynamics in blowouts

the effect of climate change on the mobility and stability of coastal sand dunes in ceara state ne brazil the coast of ceara state in ne brazil is covered by vast fields of active and stabilized coastal sand dunes its tropical climate is characterized by two seasons wet and dry with wind intensity determined by the meridional shift of the intertropical convergence zone the wind power is negatively correlated with precipitation and precipitation is negatively correlated with the difference between sea surface temperatures of the tropical atlantic north and south of the equator we present a model suggesting that during the late pleistocene wind power determined the mobility and stability of the dunes sand dunes accumulated during periods of high wind power as it is today and stabilized when wind power was low once the dunes were stabilized by vegetation they could not be activated even by increased wind power samples that were taken for luminescence dating from 25 stabilized dunes along the coasts of ceara gave ages ranging from135 ka to 100 yr we postulate that these luminescence ages fall at the beginning of wet periods in ne brazil characterized by low wind power these paleoclimatic wet periods correlate well with the cold periods of stades in greenland ice core records

development and age structure of holocene coastal sand dunes at horn head near dunfanaghy co donegal ireland two areas of holocene coastal sand dunes on the western side of the horn head peninsula extend from low ground immediately inland of their respective source beaches onto flanking higher ground 100 m od stratigraphic investigations supported by 14c dating of buried organic rich horizons and shells demonstrate several phases of sand accumulation in the pollaguill croaghadara system in contrast to the larger tramore anloge hill system where the available evidence points to relatively recent dune emplacement a broadly synchronous phase of dune development occurred during the thirteenth to fourteenth centuries ad and is viewed as part of a regional northwestern europe dune building episode resulting from climatic deterio ration earlier phases pre 3300 2800 14c years bp of aeolian sand deposition at pollaguill croaghadara have no apparent equivalents at tramore anloge hill and repeated fluvial incision and sand reworking during the last 2000 14c years is also evident at the former site dated organi

effects of sand supply on the morphodynamics and stratigraphy of active parabolic dunes bigstick sand hills southwestern saskatchewangeological survey of canada contribution 20060654 sand supply is a major controlling factor on parabolic dune form and stratigraphy in inland settings in this study aerial photographs ground penetrating radar gpr and stratigraphic analysis d

a general framework for modeling sediment supply to coastal dunes including wind angle beach geometry and fetch effects a series of spatially explicit equations are derived that form the foundation of a modeling framework that provides insight into how the interaction of the fetch effect and angle of wind approach leads to tradeoffs that govern the magnitude of aeolian sediment transport across beaches of different geometry the spatial distribution of sediment transport rate per unit width at any point on the beach is shown to vary predictably as a function of wind angle critical fetch and beach geometry and this has evident implications for the total volume and distribution of sediment transport into the dunes behind the beach as well as the proportion of sediment lost from the beach dune system at the downwind margin as the wind field shifts from onshore shore perpendicular to oblique shore parallel approach angle total sediment transport rate across a dune line segment will reflect a tradeoff between transport reduction because of the cosine effect and transport enhancement because of potentially longer fetch distances traversed by the wind prior to encountering the dune line this tradeoff is most evident on long narrow beaches when beach width is less than the critical fetch for such beaches and with onshore winds the total sediment transport rate across the dune line will be less than that predicted for a wide beach because of the constraint imposed by the fetch effect however as the angle of wind approach becomes oblique the available fetch becomes progressively longer transport limitations imposed by the fetch effect are negated and transport enhancement across the dune line is to be expected with very large angles of wind approach the cosine effect dominates the interaction and transport reductions across the dune line occur until the wind is shore parallel and sediment supply to the dunes ceases altogether this sequence of adjustments and tradeoffs were only partially understood prior to this study and yet they form the foundation of coastal dune modeling the framework proposed in this paper serves to place future studies of process form interaction in beach dune systems on a robust theoretical foundation it also facilitates the testing of various alternative hypotheses regarding the uneven spatial and temporal distribution of dune height and growth rate in coastal environments

transformation weakening diffusion creep in eclogites as a result of interaction of mineral reactions and deformation abstract the deformation of eclogites and the driving forces for their fabric development are an important topic potentially allowing to determine deformation rates and stresses in subduction zones where the greatest number of large earthquakes occurs here fabric studies of grain size and shape texture and chemical composition from two locations of variscan and alpine eclogites are presented all samples show a well developed crystallographic preferred orientation cpo of omphacite with a strong maximum of 001 in the lineation direction and a weaker maximum of poles to 010 normal to foliation garnet shows no systematic cpo anisotropic chemical zoning developed in omphacite and garnet during growth together with elongated grain shapes and can be related to a prograde in terms of pressure change p t path the individual chemically zoned and elongated grains orientated in the stretching direction are single crystals without major internal misorientations chemical microstructural and cpo data indicate that the deformation microstructure and texture were produced by preferential crystal growth of garnet and omphacite grains in the extension direction dislocation creep can be excluded as a possible fabric formation process by the systematic and oriented chemical zonation of single crystals and absence of dynamic recrystallization microstructures the dominant deformation is inferred to be diffusion creep where dissolution of material took place in reacting mafic phases plagioclase pyroxene and precipitation took place in the form of new eclogite facies minerals omphacite garnet zoisite this type of diffusion creep deformation represents a transformation process involving both deformation and metamorphic reactions it is emphasized that the weakening is directly connected to the transformation and therefore transient the weakening facilitates diffusion creep deformation of otherwise strong minerals pyroxene garnet zoisite at far lower stresses than dislocation creep the results imply low stresses during the deformation of eclogite blocks in subduction zones these results can be applied to other rock types too

magnetostratigraphy of the xiaolongtan formation bearing lufengpithecus keiyuanensis in yunnan southwestern china constraint on the initiation time of the southern segment of the xianshuihe xiaojiang fault the late cenozoic extensional basins in yunnan province southwestern china which are kinematically linked with the regional strike slip faults can provide meaningful constraints on the fault activity history and tectonic evolution of the southeast margin of the tibetan plateau semtp and further on the geodynamic evolution of the tibetan plateau however this has been severely impeded by the lack of precise age constraints on the timing of fault activity to better constrain the timing of fault activity and the tectonic rotation of semtp we undertook a high resolution magnetostratigraphic study on the xiaolongtan formation in the xiaolongtan basin which is located at the southern tip of the xianshuihe xiaojiang fault and is well known by the presence of hominoid lufengpithecus keiyuanensis rock magnetic experiments indicate that magnetite is the main remanence carrier correlation to the geomagnetic polarity timescale was achieved by combining magnetostratigraphic and biostratigraphic data our correlation suggests that the xiaolongtan formation sedimentary sequence spans from chron c5ar 1r to chron c5n 2n which indicates that the age of the xiaolongtan formation ranges from 10 ma to 12 7 ma and that the ages of the two sedimentary layers possibly bearing the hominoid l keiyuanensis are 11 6 ma or 12 5 ma the basal age of the sediments is 12 7 ma which indicates that the activation of the southern xianshuihe xiaojiang fault was initiated at this time the overall mean paleomagnetic direction d 353 2 i 34 2 95 2 1 n 166 documents a counter clockwise vertical axis rotation of 8 3 with respect to eurasia which is the response to the activity of the left lateral xianshuihe xiaojiang fault

environmental controls on coastal dune formation skallingen spit denmark abstract many coastal dune systems in western europe were emplaced during the little ice age lia the formation of such dune fields has generally been ascribed to a combination of low sea level and strong winds during that time period providing a supply of sand from the exposed shoreface and sufficient wind energy to transport this sand landward however little information exists on the processes that controlled sediment supply to the beach and why this onshore supply was initiated at all in this contribution we consider the origin and development of older dune fields on a barrier spit complex skallingen located in the northern part of the danish wadden sea maps and new data on dune litho and chrono stratigraphy the latter based on osl dating allow a precise estimate of the initiation and termination of dune emplacement dune formation at skallingen started at a relatively late stage of the lia and it can be temporally correlated with a phase of relative sea level rise in north western europe and with a high frequency of storm surges along the danish west coast these are the conditions during which nearshore bars currently migrate onshore across the shoreface off skallingen the bars eventually merge with the beach and constitute a source of sand for modern foredune accretion it is probable that the onshore bar migration occurred under similar conditions in the past and the migration was triggered or enhanced by the sea level recovery from the mid lia low stand and the associated frequent storm surge activity consequently at skallingen onshore sand supply was caused by marine rather than aeolian agents this supply provided the basis for subsequent dune formation indications are however that the sediment supply to the beach dunes was a factor of 2 3 larger in the past dune aggradation eventually ceased around 1900ad because of dyke construction hence the association between dune formation and sea level surge variation at skallingen is somewhat contrary to other statements of coastal dune development during the lia in north western europe

aeolian sand movement and relative sea level rise in ho bugt western denmark during the little ice age this study documents an extensive aeolian sand sheet buried in the salt marshes of the ho bugt embayment in western denmark the extent of the sand sheet was mapped from c 60 cores and sections which were also used to reconstruct late holocene changes in relative sea level based on diatom analyses chronology was provided by optically stimulated luminescence osl and radiocarbon dating our study shows that since 2000 cal yr bp relative sea level in ho bugt has risen by approximately 1 5 m the overall rise was punctuated by two periods with higher than average rates of sea level rise the first between 2000 and 1400 cal yr bp and the second commencing c 500 cal yr bp around 700 cal yr bp the evolution of the skallingen spit may have been responsible for a reduction in the local tidal range and the formation of an extensive black layer in the western part of the embayment osl analyses date the sand sheet to between ad 1460 40 and ad 1550 30 490 40 and 400 30 cal yr bp consistent wi

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

climate change and coastal hydrographic response along the atlantic iberian margin tagus prodelta and muros ria during the last two millennia the tagus prodelta w portugal and the muros ro a nw spain are areas of high deposition rates registering high resolution palaeoclimatic records for western iberia we compare the climatic conditions of the two areas over the last two millennia based on proxies of temperature sea surface temperatures and oxygen isotopes continental input grain size iron and magnetic susceptibility and productivity inorganic and organic carbon carbon isotopes benthic foraminifera and diatoms biogeochemical changes in the tagus prodelta reflect widely recognized north atlantic climatic periods encompassing the roman period ad 0 350 the dark ages ad 400 700 the mediaeval warm period mwp ad 800 1200 and the little ice age lia ad 1300 1750 the atmospheric north atlantic oscillation nao drives the tagus prodelta multidecadal long term variability in precipitation river input during cold periods negative nao and marine upwelling during warmer periods positive nao a scheme that is reversed in the galician region the muros ro a shows only local hydrodynamics until ad 1150 including a suboxic event in the inner ro a around ad 500 700 since ad 1150 atlantic warm upwelled waters have ventilated the outer ro a but only reach the inner ro a at ad 1750 the twentieth century records are also interpreted as a reflex of the inverse nao mode in both areas resulting in amplification of the lia biogeochemical water conditions centennial scale solar activity appears to be another important forcing mechanism or the only one if solar activity drives the nao and bond cycles behind changes in the hydrography of the tagus prodelta and primary production bottom ventilation and organic carbon degradation in the muros ro a

relationship between foredune profile morphology and aeolian and marine dynamics a conceptual model abstract foredunes are highly dynamic coastal features that are intrinsically connected with their adjacent beaches correlations among parameters representative of aeolian and marine dynamics and the size and location of foredunes were carried out the results indicate that foredune steady state location depends mainly on marine dynamics given that foredune toe level was positively correlated with the total water level of 10 year return period which guarantees that the foredune is only eroded by waves occasionally and therefore will have time to recover and return to its long term morphological state foredune steady state size was characterized by its volume which was positively correlated with aeolian sediment drift potential and exponentially related to the total water level with a 10 year return period aeolian sediment drift potential is indicative of the total amount of sand that potentially reaches the foredune and therefore the foredune size is directly related to it higher total water level with a 10 year return period leads to a foredune located further from the shoreline and at a higher altitude higher toe level as mentioned above consequently the beach is wider and the presence of moisture is expected to be lower this wider and dryer beach allows the aeolian sediment transport to approximate to its maximum value increasing its potential to build a bigger foredune data confirmed that the total water level with a 10 year return period and the foredune volume are exponentially related the correlations found show that foredune steady state size is related to both aeolian sediment drift potential and marine dynamics based on these results a long term conceptual model is proposed to explain the different morphological characteristics of the steady state shape of foredunes as a function of the joint action of marine and wind dynamics

a lifetime of the variscan orogenic plateau from uplift to collapse as recorded by the prague basin bohemian massif the ordovician to middle devonian prague basin bohemian massif represents the shallowest crust of the variscan orogen corresponding to c 1 4 km palaeodepth the basin was inverted and multiply deformed during the late devonian to early carboniferous variscan orogeny and its structural inventory provides an intriguing record of complex geodynamic processes that led to growth and collapse of a tibetan type orogenic plateau the northeastern part of the prague basin is a simple syncline cross cut by reverse thrust faults and represents a doubly vergent compressional fan accommodating c 10 19 nw se shortening only minor syncline axis parallel extension and significant crustal thickening the compressional structures were locally overprinted by vertical shortening kinematically compatible with ductile normal shear zones that exhumed deep crust in the orogen s interior at c 346 337 ma on a larger scale the deformation history of the prague syncline is consistent with building significant palaeoelevation during variscan plate convergence based on a synthesis of finite deformation parameters observed across the upper crust in the centre of the bohemian massif we argue for a differentiated within plateau palaeotopography consisting of domains of local thickening alternating with topographic depressions over lateral extrusion zones the plateau growth involving such complex three dimensional internal deformations was terminated by its collapse driven by multiple interlinked processes including gravity voluminous magma emplacement and thermal softening in the hinterland and far field plate boundary forces resulting from the relative dextral motion of gondwana and laurussia

impact of atmospheric circulation patterns on coastal dune dynamics nw spain article i nfo dunes in temperate latitudes have experienced a significant stabilization in recent times essentially as a conse quence of the expansion of dense vegetation cover yet the causes for this gradual stabilization as well as the causes promoting antecedent aeolian mobilization remainpoorlyunderstood the traba coastal dune field located in nw spain was examined to explore the causes inducing aeolian activity and subsequent stabilization since 1940 morphological changes were identified through the combination of aerial photographs and geophysical techniques local wind field regimes were simulated using a regional climate model to obtain the variability of the most relevant modes of atmospheric circulation in the north atlantic and european regions north atlantic oscillation nao eastern atlantic ea and scandinavian scand this allows us to identify the impact of these circulation modes over dune dynamics results document an episode of aeolian activity during the 1950s followed by a gradual stabilization and fixation of the dune coincident with a decrease on storm and wind inten sity yet aeolian sand movement remained active insmall areas blowouts occurring mainly during the summer ne winds associated with a negative phase of the ea explain the movement of sand within the dune field under favorable conditions of sand supply on the other hand sand supply to the dune field from the beach was promoted by nw winds coincident with the summer negative phase of nao during winter the negative nao favored frequent sw winds associated with the passage of intense storms which in turn explain sand remobilization from the beach making sediment available for the nw winds to blow inland with this work it is proven that to understand past and future aeolian activity requires critical consideration of the variability and impact of the two principal modes of atmospheric circulation in the north atlantic nao and ea the scand mode explaining alowerpercentageofthelocalwind fieldvariabilitywasalsoincludedtoachievehigher significance levels of explained variance

cooling driven climate change at 12 11 ma multiproxy records from a long fluviolacustrine sequence at guyuan ningxia china abstract to explore the evolution of climate through the miocene especially during the middle miocene climate transition multiproxy continental records were analyzed by susceptibility sus lightness l total inorganic carbon tic and total organic carbon toc content from the 2900 m thick fluviolacustrine sediment sequence at guyuan ningxia china and compared with the redness a and the pollen humidity indices from the same section the published miocene records of sedimentation rate sediment grain size biota turnover and palaeoproductivity from other regions were also compiled and compared results show that multiproxies of the sikouzi section have changed substantially since 12 11 ma ago sus l and tic have increased while a toc and the pollen humidity index decreased all implying that the palaeoclimate in the study area has got cooler and drier since that time this climate change also left imprints in many other regions probably resulting from global cooling and the development of the east antarctic ice sheet since about 14 ma several positive feedback mechanisms are proposed to have effectively modulated and magnified the mid miocene global cooling including vegetation change greenhouse gas atmospheric co2 and water vapor fluctuations they led to the strengthing of ocean and atmospheric circulation significant lowering of sea level and increasing aridification over the globe especially in middle high latitudes since 12 11 ma ago a continuously cooler and drier climate may have caused the substantial intensification of physical weathering and exhumation on the earth s surface the increased sediment accumulation rates on the land and in the sea and the inception of productivity increase in the oceans nevertheless when and where these mechanisms operated and how they were tied to each other remain ambiguous deserving further investigation

internal structure of a trough blowout determined from migrated ground penetrating radar profiles ground penetrating radar gpr was used to investigate the relationship between the geomorphological development of a large aeolian trough blowout and the stratigraphy and internal sedimentary structure of its associated deposits although analogous many of the data processing techniques routinely applied in seismic reflection are very rarely applied in gpr studies in this study a simple migration program was used that significantly enhanced the quality of gpr images from a large trough blowout at raven meols on the sefton coast northwest england these improvements aided subsequent data interpretation which was achieved through application of the principles of radar stratigraphy gpr shows the pre blowout dunes to have a complex internal structure that suggests they were formed in the presence of at least a partial vegetation cover subsequent to stabilization of these dunes a thin soil developed this dune soil forms an important radar sequence boundary and delineates a complex topography beneath the depositional lobe of the blowout the internal structure of the depositional lobe of the blowout does not conform to a model of simple radial foreset deposition as derived from contemporary process studies reported in the literature instead the pattern of deposition has been extensively modified by the antecedent dune topography and by varying spatial and temporal exposure to important sand transporting winds that is partly controlled by interactions between the regional wind pattern and local dune morphology trough blowout deposits in coastal aeolian sedimentary sequences are likely to be recognized by the presence of laterally continuous packets of relatively high angle cross strata which often display a spatially variable radial dip pattern that is only very poorly or partially developed in addition a soil or other surface representing a significant hiatus in dune deposition is likely to underlie the blowout deposits the topography of which will show a clear relationship to the dip and orientation of the overlying cross strata

high resolution measured and modelled three dimensional airflow over a coastal bowl blowout abstract blowouts are common landforms found within coastal dunes their dynamics are primarily driven by aeolian transport caused by surface wind stress though patterns of deflation and deposition within blowouts are poorly understood as near surface wind flow is complex three dimensional wind flows around blowouts have yet to be properly quantified especially within zones of separation re attachment and acceleration this has been largely due to inadequate measurement of airflow and a lack of suitable airflow models with this in mind we present results from a study that has quantified alongshore and oblique onshore wind flow dynamics over a bowl blowout on the belmullet peninsula ireland using ultrasonic three dimensional anemometry measuring at 50 hz and three dimensional computational fluid dynamic cfd modelling we measure and model for the first time in 3d a detailed picture of the heterogeneity of wind flow over this type of terrain during alongshore wind conditions wind speeds within the deflation basin were retarded by 50 compared to the foredune zone and flow separation restricted to a small zone in lee of the windward rim wind was directed into the deflation basin through a gap in a western erosional wall termed the blowout throat in oblique onshore wind airflow orientated with the blowout throat remained unchanged in direction and slowed by only 30 compared to wind speed on the foredune in lee of the erosional wall adjacent to the blowout throat small zones of flow separation occurred close to the erosional wall in both cases the highest variation in wind speed and direction occurred in zones of separation and attachment whilst flow increased in steadiness with height over the erosional walls the results illustrate that wind is manipulated according to localised topography within the bowl blowout itself resulting zones of potential sediment transport erosion and deposition are spatially complex and alter with wind direction the presence of a blowout throat has a significant influence on airflow patterns within a deflation basin modelled cfd and measured anemometer data demonstrated excellent comparisons for wind direction and speed allowing much greater spatial measurement resolution than physical instrumentation simulated turbulence did not correlate well with measured data highlighting the requirement for high frequency three dimensional anemometry in areas of complex flow

origin of a complex and spatially diverse dune field pattern algodones southeastern california the algodones dune field of southeastern california shows a complex and spatially diverse dune field pattern that is superimposed upon a series of topographic lineations analysis of dune field pattern parameters dune crest length crest orientation dune spacing and defect density derived from aerial images indicates that the dune field pattern represents two constructional generations prominent compound crescentic dunes formed during the first constructional generation a younger generation consists of a variety of simple crescentic dunes linear dunes and zibars statistical differences in the pattern parameters between the dune groups within the second generation are resolved through consideration of the boundary conditions under which the dune pattern evolved and provide explanations for 1 diversity of dune types 2 range in implied constructional times 3 range in crest orientations and 4 the anomalous nature of the population of linear dunes the boundary conditions that have modified pattern development include orographic effects grain size vegetation areal extent and antecedent conditions topographic lineations in the algodones range from the western ramp which defines the field margin to subtle features masked by the pattern of dunes imaging of the western ramp using ground penetrating radar shows high angle cross strata migrating perpendicular to the lineation trend the most plausible hypothesis for the origin of the lineations is as dune ridges sequentially shed from adjacent lake cahuilla which is the source of algodones sands the overall geomorphic complexity of the algodones originates from the emplacement of the dune ridges during stages of lake cahuilla the two generations of dune field construction and the controls exerted by boundary conditions

crustal influx indentation ductile thinning and gravity redistribution in a continental wedge building a moldanubian mantled gneiss dome with underthrust saxothuringian material european variscan belt 1 the contribution of lateral forces vertical load gravity redistribution and erosion to the origin of mantled gneiss domes in internal zones of orogens remains debated in the orlica snieznik dome moldanubian zone european variscan belt the polyphase tectono metamorphic history is initially characterized by the development of subhorizontal fabrics associated with medium to high grade metamorphic conditions in different levels of the crust it reflects the eastward influx of a saxothuringian type passive margin sequence below a tepla barrandian upper plate the ongoing influx of continental crust creates a thick felsic orogenic root with hp rocks and migmatitic orthogneiss the orogenic wedge is subsequently indented by the eastern brunia microcontinent producing a multiscale folding of the orogenic infrastructure the resulting kilometre scale folding is associated with the variable burial of the middle crust in synforms and the exhumation of the lower crust in antiforms these localized vertical exchanges of material and heat are coeval with a larger crustal scale folding of the whole infrastructure generating a general uplift of the dome it is exemplified by increasing metamorphic conditions and younging of 40ar 39ar cooling ages toward the extruded migmatitic subdomes cored by hp rocks the vertical growth of the dome induces exhumation by pure shear dominated ductile thinning laterally evolving to non coaxial detachment faulting while erosion feeds the surrounding sedimentary basins modeling of the bouguer anomaly grid is compatible with crustal scale mass transfers between a dense superstructure and a lighter infrastructure the model implies that the moldanubian orlica snieznik mantled gneiss dome derives from polyphase recycling of saxothuringian material

age and dynamics of linear dunes in the namib desert bristow c s duller g a t lancaster n 2007 age and dynamics of linear dunes in the namib desert geology 35 6 555 558 sponsorship american chemical society

the evolution of holocene coastal dunefields jutland denmark a record of climate change over the past 5000 years coastal dunefields have developed on the west coast of jutland in denmark over the past 5000 years the dunefields are situated in a temperate climate zone with frequent high energy wind events dunefield development was characterized by repeated periods of transgressive dune formation punctuated by periods of dune stabilization and soil formation the chronology of dunefield evolution is based on accelerator mass spectrometry ams radiocarbon dating of peaty palaeosols 24 samples and optically stimulated luminescence osl dating of aeolian sand deposits 19 samples these dates indicate that the completeness of the stratigraphic record varies considerably but that the timing of aeolian activity events was identical in the dunefields examined here initiation of aeolian activity occurred around 2200 bc 800 bc ad 100 ad 1050 1200 and between ad 1550 and 1650 proxy climate data from bogs in southwestern sweden suggest that these periods of dunefield activity were initiated during wet cool summers most likely these climatic situations were associated with a more frequent passage of cyclones across denmark in the summer seasons increased storminess causing aeolian sand movement and dune formation the continued removal of vegetation in jutland between 4000 bc and ad 1850 allowed the aeolian sand when first activated to move more and more easily across the coastal plains the final phase of aeolian sand movement between ad 1550 1650 and 1900 had catastrophic implications for many coastal inhabitants in the region c 2008 elsevier b v all rights reserved less

extension tectonics the neogene opening of the north south trending basins of central thailand paleomagnetic samples were collected from late neogene basalt flows from thailand all of these flows are horizontal and are relatively unaltered in thin section these rocks possess a stable magnetization which is believed to be primary samples from 48 lava flows were collected from sites located within the khorat plateau the chao phraya phitsanulok basin and the mountainous terrane west of the chao phraya phitsanulok basin these data were combined with previously reported late neogene data from five flows from western thailand although the average inclination from the 53 sites is indistiguishable from the expected dipole inclination the average declination has a net clockwise rotation of 13 5 5 8 from the geocentric dipole field furthermore the mean declination values from the 29 flows from the khorat plateau are indistinguishable from the present dipole field direction dm 4 3 7 5 and indistinguishable from the mean declination from 28 late neogene volcanic flows from vietnam in contrast the mean declinations from 24 flows collected from central and western thailand are deflected significantly clockwise dm 24 4 7 7 from the geocentric dipole field direction the differential rotation between western and central thailand versus the khorat plateau suggests that indochina is composed of at least two structural blocks which underwent a different rotational history these observations when combined with geologic and geophysical data from the chao phraya phitsanulok basin gulf of thailand and the intermontane basins of western thailand suggest that the rotations are recording a late neogene phase of e w extension of these basins we suggest that the formation of these basins and the related basaltic volcanism developed in reponse to subduction of the indian plate under western burma we envision the tectonics of this region is similar in style to the basin and range region of the western united states last we have observed field relationships from some of the rhyolites located in the central basin although these rhyolites are reported to be mesozoic or paleozoic in age our field observations and a k ar age date show that at least some of these rhyolites are younger than the basalts we suggest that the rhyolites form a bimodal suite with the basaltic rocks which were erupted in the later stages of the extension

the tess 1 suction corer a new device to extract wet uncompacted sediments conventional coring can be an expensive and cumbersome technique in uncompacted waterlogged sediments especially when large numbers of samples are required rapidly and when vehicular access is restricted the existing van der staay suction corer van de meene et al 1979 solves economic and other problems chiefly logistical and environmental issues but sample extraction has to be done in the field the original purposes of the van der staay suction corer were to enable rapid drilling through sand and allow field sampling it was not designed to recover intact samples for subsequent laboratory analysis cores from the new tess 1 suction corer however are encapsulated in the field the tess 1 therefore combines the advantages of the original corer with the possibility of taking samples for laboratory analysis samples collected using the tess 1 suction corer show little deformation allow coring of soft uncompacted mud and retention of sedimentary structures problems due to sediment fluidization and movement inside the core pipe are usually minimal the tess 1 suction corer can be used in both wetland areas beach tidal flats and marshes and in shallow subaqueous environments lakes rivers and nearshore subtidal areas

late palaeozoic strike slip tectonics versus oroclinal bending at the sw outskirts of baltica case of the variscan belt s eastern end in poland geophysical and geological data from the eastern sector of the central european variscan belt are presented and reviewed in the regional tectonic context matched filtering of isostatic gravity guided by results of spectral analysis along with other derivatives of gravity and magnetic fields reveal a dominant wnw ese trending pre permian structural grain in the external zones of the variscan belt in poland this trend is confirmed by regional distribution of dips in carboniferous and devonian strata that were penetrated by boreholes beneath permian mesozoic sediments based on these data two alternative concepts explaining the connection of the variscan belt and its ne foreland those of strike slip tectonics versus oroclinal bending are discussed the wnw ese structural trend in the variscan foreland is parallel to a set of major strike slip fault zones in the area including those of upper elbe intra sudetic odra dolsk and krakow lubliniec these faults are considered to convey a significant dextral displacement between laurussia and gondwana the revised position of the variscan deformation front shows a similar uninterrupted generally wnw ese trend up to the se border of poland which indicates an initial continuation of the variscan belt into the area of the present day western carpathians the geometry of the variscan deformation front along with the pattern of the variscan structural grain are inconsistent with the idea of an oroclinal loop affecting the external non metamorphic variscan belt however the data presented do not entirely rule out an oroclinal loop within the variscan internides the still possible options are 1 a semi oroclinal model postulating 90 bending of the variscan tectonostratigraphic zones into parallelism with the wnw ese strike slip faults or 2 an orocline limited only to the belt linking the wolsztyn high and moravo silesian non to weakly metamorphic fold and thrust belt regardless of the kinematic model preferred our data indicate that structural evolution of the polish variscides was concluded with the end carboniferous nne ssw shortening that resulted in the present day extent of the variscan deformation front

how did the ad 1755 tsunami impact on sand barriers across the southern coast of portugal idl pest oe cte la0019 2013 plani2c ed481b 2014 132 0 post doc eu fp7 research project risc kit ga 2013 603458 e fct investigator program ref if 01047 2014

on the connection between winter anomalous precipitation in the iberian peninsula and north west africa and the summer subtropical atlantic sea surface temperature 1 recent studies show that the state of the winter nao is led by changes in the north atlantic na sea surface temperature sst with some months in advance this finding encouraged us to analyze the possible predictability of the precipitation in the iberian peninsula and north west africa ipna regions two of the most nao affected areas the results of a lag singular value decomposition analysis with the precipitation and the sst anomalies show a possible connection between the first mode of the anomalous ipna winter precipitation and the previous summer sst anomalies over the north atlantic na basin the use of a monte carlo test confirms the significance of the results and moreover this sst pattern tends to persist from the previous summer months in the subtropical na to show that this connection is robust a crossvalidation analysis is performed using as a predictor the anomalous summer sst in the na basin

grain scale processes in actively deforming magma mushes new insights from electron backscatter diffraction ebsd analysis of biotite schlieren in the jizera granite bohemian massif abstract in the porphyritic jizera granite bohemian massif three distinct types of lattice preferred orientations of biotite grains were revealed in schlieren delineated magmatic structures using the electron backscatter diffraction ebsd method 1 biotite basal planes 001 reorient from schlieren subparallel near the schlieren base to schlieren perpendicular in the upper part of the schlieren both orientations share subhorizontal n s to nne ssw trending a axes 2 in some domains the a axes are steep and at a high angle to the schlieren plane while the c axes plunge shallowly and rotate around an ill defined a axis 3 in other domains the ebsd coincides with background magnetic fabric of the host granite revealed using the anisotropy of magnetic susceptibility ams method that is the a axes plunge shallowly to the se or nw while the c axes are subhorizontal and cluster around the ne sw trend these multiple biotite orientations in the schlieren are interpreted to reflect 1 velocity gradient in laminar magma flow along channel like conduits localized within the high strength host phenocryst framework 2 grain scale gravity driven constrictional deformation of the magma mush and 3 overprinting background tectonic deformation transmitted across large parts of the magma chamber prior to its final crystallization the grain scale mechanisms of biotite fabric acquisition in the schlieren presumably involved rotation of biotite crystals during flow with the biotite alignment reflecting the flow geometry and kinematics replaced after flow cessation by melt aided grain boundary sliding of those biotite crystals still enclosed in melt pockets within otherwise static highly crystallized magma mush the latter process was sufficient to reorient biotite grains but not to cause destruction of the schlieren using the jizera granite as a case example we argue that the lattice preferred orientation of mineral grains in mafic schlieren is highly sensitive to reorient in response to processes both associated with the schlieren formation e g localized magma flow and those that occur later and are superimposed onto the effectively solid high strength magma mush

cyclical evolution of a modern transgressive sand barrier in northwestern spain elucidated by gpr and aerial photos abstract the internal structure of a modern baymouth barrier is analyzed in detail including its historical evolution and the factors controlling it historical evolution was reconstructed using available aerial photographs from 1956 to 2003 detailed geophysical data were acquired using ground penetrating radar gpr and analyzed along with airphotos to reconstruct the recent evolution of a barrier located in northwestern spain the gpr data reveal the internal architecture of the barrier which consists of two main radar facies 1 washover deposits associated with landward barrier migration and vertical aggradation and 2 beach deposits associated with seaward barrier progradation the reconstruction of the stratigraphic sequence indicates the occurrence of two erosive periods followed by an accretionary period the erosion along the barrier is outlined by the presence of three well defined bounding surfaces the stratigraphic record of the subsequent recovery phase depends on the impact level of the erosive phase which is controlled by the presence of ephemeral inlets along the barrier this alternating behavior implies a discontinuous shoreline trajectory in spite of a net landward migration this trend is consistent with regional sea level rise albeit being intensified locally by the interplay of sediment starvation and storm regime landward barrier retreat occurs by overwash and inlet breaching which permits barrier preservation of volume due to a continuous constructive destructive cycle the results acquired from this example expand our understanding of the internal structure and evolutionary trends of transgressive sand barriers

parabolic dune reactivation and migration at napeague ny usa insights from aerial and gpr imagery abstract observations from mapping since the 19th century and aerial imagery since 1930 have been used to study changes in the aeolian geomorphology of coastal parabolic dunes over the last 170 years in the walking dune field napeague ny the five large parabolic dunes of the walking dune field have all migrated across or are presently interacting with a variably forested area that has affected their migration stabilization and morphology this study has concentrated on a dune with a particularly complex history of stabilization reactivation and migration we have correlated that dune s surface evolution as revealed by aerial imagery with its internal structures imaged using 200 mhz and 500 mhz ground penetrating radar gpr surveys both 2d transect and high resolution 3d gpr imagery image downwind dipping bedding planes which can be grouped by apparent dip angle into several discrete packages of beds that reflect distinct decadal scale episodes of dune reactivation and growth from aerial and high resolution gpr imagery we document a unique mode of reactivation and migration linked to upwind dune formation and parabolic dune interactions with forest trees this study documents how dune dune and dune vegetation interactions have influenced a unique mode of blowout deposition that has alternated on a decadal scale between opposite sides of a parabolic dune during reactivation and migration the pattern of recent parabolic dune reactivation and migration in the walking dune field appears to be somewhat more complex and perhaps more sensitive to subtle environmental pressures than an idealized growth model with uniform deposition and purely on axis migration this pattern believed to be prevalent among other parabolic dunes in the walking dune field may occur also in many other places where similar observational constraints are unavailable

the central sudetic ophiolites sw poland petrogenetic issues geochronology and palaeotectonic implications abstract the central sudetic ophiolites cso including the largest and best studied leza ophiolite are relatively well preserved complete palaeozoic ophiolitic sequences at the ne margin of the bohemian massif near the eastern edge of the variscan belt in central europe despite a detailed study and a well documented morb type affinity the geochemical complexity of these ophiolites has only recently been appreciated allowing construction of petrogenetic models we review here petrological and geochemical data indicating a contrast between the plutonic and volcanic members of the leza ophiolite this contrast was previously interpreted in terms of a model of two stage incremental melting of a depleted asthenospheric source producing basaltic magmas and subsequent melts crystallizing as gabbros however we argue that the geochemical differences between the plutonic and volcanic members can be explained by differentiation and cumulation processes of broadly similar parental magmas preliminary interpretation of new shrimp zircon age data from plutonic and volcanic members are consistent with earlier u pb zircon ages and provide evidence for magmatic crystallization of the leza ophiolite at c 400 ma the cso interpreted as traces of the rheic ocean are key for reconstructing the early to mid palaeozoic rifting processes distinct similarities exist with time equivalent ophiolitic units in the western variscan segment of the nw iberian massif the cso represent c 400 ma oceanic crust fragments and their structural position delineates likely major variscan tectonic sutures and tectonic mosaic domains within the variscan accretionary prism

late oligocene recent stress evolution in rift basins of northern and central thailand implications for escape tectonics abstract the tertiary rift basins of thailand are known through sub surface seismic and borehole data collected for hydrocarbon and coal exploration outcrops in open cast coal mines and a few natural outcrops these data provide mixed perspectives on how the basins evolved some providing data on ages and structural geometries others palaeostress data in general the region evolved under approximately e w extension although the extension direction probably changed periodically within basins extension was episodically interrupted by inversion events associated with sub horizontal nw se to ne sw 1 direction there is no evidence to suggest that the string of rift basins running from n thailand and laos into the gulf of thailand evolved in a similar way on the contrary the evolution of each basin seems different although certain regional trends along the rift system are apparent as follows 1 oligocene lower miocene extension is widespread in the region 2 in central and northern thailand middle miocene extension is also important and extension persisted into the upper miocene pliocene 3 in the extreme south of the area w natuna basin penyu basin malay basin extension ceased in the earliest miocene 4 in the northern gulf of thailand extension ceased in the middle miocene 5 thermal subsidence is greatest up to 4 km in the south malay pattani w natuna and penyu basins and least in northern thailand a few tens to hundreds of metres 6 inversion in the southern gulf of thailand was intense and occurred during the lower and middle miocene in the northern gulf of thailand inversion is very mild and occurred during the lower and middle miocene onshore inversion is patchy during the miocene but is strongest in the northwestern rift basins particularly the li basin the most widespread inversion event that affects the north occurred during the plio pleistocene it might be associated with the change from left to right lateral motion on the red river fault the relationship between strike slip faults and rift basins in terms of timing of extensional and inversion events and palaeostress orientation and evolution is more complex than can be explained by simple escape tectonic models

polytopic vector analysis pva modelling of whole rock and apatite chemistry from the karkonosze composite pluton poland czech republic abstract this study presents a novel approach for analysing the magma evolution path in composite plutons applying the so termed polytopic vector analysis pva to whole rock and apatite chemistry as an example of a multiphase magmatic body the karkonosze granitoid pluton was chosen which formed by a combination of magma mixing and fractional crystallization of two distinct melts granitic crust derived and lamprophyric mantle derived the goal was to model end member magma compositions recorded by apatite and to estimate to what extent these end members interacted with each other although using single minerals as proxies to magma compositions is tricky the studied apatite well reflects the compositional trends within the magma e g decreasing lree y ratios varying halogen content increasing mn and na concentrations the results of pva simulations for whole rock geochemistry demonstrate a model similar to that constrained from previous studies apart from the main trend of mixing between a felsic 80 wt sio 2 and a mafic 53 wt sio 2 end member em an additional process has been recognized representing most probably the continuous evolution of the mafic end member responsible for the compositional diversity of some rocks one felsic ree poor mn f rich and one mafic cl sr si ree rich apatite end members were recognized whereas the third one represents most probably a fluid component enriched in si y ce and nd present at all magmatic stages however most prominent during the late stage the widest range of em proportions and the highest contribution of the mafic em are displayed by apatites from the early stage during the middle and late stages the apatites present a narrow range of em proportions with almost all apatites bearing a felsic signature this pattern reflects the progressive homogenization of the system although the pva method applied to mineral chemistry poses some limitations it may provide a more detailed image of the combination of differentiation processes and magma sources involved in the formation of a complex composite pluton

morphometric characterization of foredunes along the coast of northern spain abstract foredunes are defined as the first shore parallel dune ridges adjacent to stable and prograding beaches formed on the backshore by aeolian sand deposition influenced by vegetation foredunes have the important functions for mitigating impacts caused by extreme events providing sediment to the beaches during storm and accumulating sediment again under fair weather wave conditions mainly for this reason there is currently great interest in preserving building or recovering foredunes on a long term timescale decades foredunes are recognized as exhibiting possible equilibrium conditions the identification of this condition is of interest to projects involving the recovery and creation of foredune beach systems therefore the main objective of this work is to identify the morphometric characteristics of equilibrium foredunes and the interrelations between the morphometric parameters of height width volume and maximum slope allometric relationships to reach this objective 193 foredune subaerial beach profiles from along the northern coast of spain that have characteristics close to equilibrium conditions were evaluated the results indicate that foredune size can vary significantly however strong correlations between morphometric parameters have been verified and allometric relationships between foredune volume height width and maximum slope are proposed

the structure and development of foredunes on a locally prograding coast insights from ground penetrating radar surveys norfolk uk the internal structure of coastal foredunes from three sites along the north norfolk coast has been investigated using ground penetrating radar gpr which provides a unique insight into the internal structure of these dunes that cannot be achieved by any other non destructive or geophysical technique combining geomorphological and geophysical investigations into the structure and morphology of these coastal foredunes has enabled a more accurate determination of their development and evolution the radar profiles show the internal structures which include foreslope accretion trough cut and fill roll over and beach deposits foredune ridges contain large sets of low angle cross stratification from dune foreslope accretion with trough shaped structures from cut and fill on the crest and rearslope foreslope accretion indicates sand supply from the beach to the foreslope while troughs on the dune crest and rearslope are attributed to reworking by offshore winds bounding surfaces between dunes are clearly resolved and reveal the relative chronology of dune emplacement radar sequence boundaries within dunes have been traced below the water table passing into beach erosion surfaces these are believed to result from storm activity which erodes the upper beach and dunes in one example at brancaster a dune scarp and erosion surface may be correlated with erosion in the 1950s possibly the 1953 storm results suggest that dune ridge development is intimately linked to changes in the shoreline with dune development associated with coastal progradation while dunes are eroded during storms and where beaches are eroding a stable coast provides more time for dune development resulting in higher foredune ridges a model for coastal dune evolution is presented which illustrates stages of dune development in response to beach evolution and sand supply in contrast to many other coastal dune fields where the prevailing wind is onshore on the north norfolk coast the prevailing wind is directed along the coast and offshore which reduces the landward migration of sand dunes

ground penetrating radar 2 d and 3 d subsurface imaging of a coastal barrier spit long beach wa usa abstract the ability to effectively interpret and reconstruct geomorphic environments has been significantly aided by the subsurface imaging capabilities of ground penetrating radar gpr the gpr method which is based on the propagation and reflection of pulsed high frequency electromagnetic energy provides high resolution cm to m scale and shallow subsurface 0 60 m near continuous profiles of many coarser grained deposits sediments of low electrical conductivity this paper presents 2 d and 3 d gpr results from an experiment on a regressive modern barrier spit at willapa bay wa usa the medium grained sand spit is 38 km long up to 2 3 5 km wide and is influenced by a 3 7 m tidal range spring as well as high energy longshore transport and high wave energy depositional processes the spit has a freshwater aquifer recharged by rainfall the gpr acquisition system used for the test was a portable digital pulseekko system with antennae frequency ranging from 25 to 200 mhz and transmitter voltages ranging from 400 to 1000 v step sizes and antennae separation varied depending on the test requirements in addition 100 mhz antennae were used for conducting antennae orientation tests and collecting a detailed grid of data 50 50 m sampled every meter the 2 d digital profiles were processed and plotted using pulseekko software the 3 d datasets after initial processing were entered into a landmark workstation that allowed for unique 3 d perspectives of the subsurface to provide depth near surface velocity measurements were calculated from common midpoint cmp surveys results from the present study demonstrate higher resolution from the 200 mhz antennae for the top 5 6 m whereas the 25 and 50 mhz antennae show deeper penetration to 10 m for the study site 100 mhz antennae provided acceptable resolution continuity of reflections and penetration the dip profiles show a shingle like accretionary depositional pattern whereas strike profiles show a horizontal and subhorizontal nearly continuous reflection pattern results from the gpr experiment reveal upper shoreface reflections with dip towards the ocean at about 1 2 the loss of signal from below a depth of 6 8 m indicates a lithofacies change because of the storm wave base the parallel broadside and perpendicular broadside antennae orientation tests show detailed stratigraphy continuity and depth of penetration the cross polarization test exhibits reduced continuity of reflections and less depth of penetration but dipping reflections are apparent the grid pattern data provided a detailed view of 3 d geometry of individual reflections high quality data were obtained processed and directly exported into a landmark workstation for interpretation the resulting interpretations of the upper shoreface beds from the test cube 50 50 m total 2600 traces are shown as vertical sections slices horizontal sections time slices contour maps 3 d representations of individual beds and an isopach map the 3 d depositional framework allows a more detailed interpretation than widely spaced 2 d profiles

identification of the main driving mechanisms in the evolution of a small coastal wetland traba galicia nw spain since its origin 5700 cal yr bp this paper examines the interdependence among the different forcing factors in the evolution of the traba coastal wetland galicia nw spain based on lithofacies and diatom analyses of three cores reaching the basement according to radiocarbon data the wetland originated 5700 cal yr bp a time when similar systems on the atlantic coast of the iberian peninsula were formed diatom assemblage data allow the estimation of the sea level position at 5700 cal yr bp at least 7 m below present day mean sea level attenuation of the sea level rise at that time was a major driving mechanism that permitted the establishment of an incipient beach dune complex causing water logging in the traba basin however the location of this incipient wetland on a basement high which prevented an open connection to the sea made topographic inheritance the main forcing factor in the subsequent evolution of the wetland thus traba was never a coastal lagoon system as it has sometimes been defined the maximum permeability of the beach dune complex enclosing the wetland was recorded after its origin until 2900 cal yr bp when increased stormy conditions affected the galician shelf waters since then the evolution of the wetland has been mainly controlled by more local factors especially the continental sediment supply changes in land use in the basin have accelerated the infilling of the water body since the 19th century this rapid infilling makes the whole system more prone to total encroachment in the short term rather than to sea drowning palaeoenvironmental analyses showing the main trends in the long term evolution of coastal wetlands can be of key importance in any management decisions aimed at preserving these kinds of sensitive coastal environments