u pb and hf isotopic compositions of detrital zircons from the paragneisses of the quanji massif nw china implications for its early tectonic evolutionary history abstract the quanji massif is a cratonic fragment located on the northeastern margin of the qinghai tibetan plateau in western qinghai province northwest china fig 1 this massif consists of pre neoproterozoic crystalline basement unconformably overlain by mid to late neoproterozoic and cambrian strata the basement is dominantly made up of the delingha complex and the supracrustal dakendaban group the delingha complex is made up of 2 24 2 39 ga granitic gneisses with enclaves of dominant amphibolite and minor felsic gneisses as well as granulites the supracrustal dakendaban group is in tectonic contact with the delingha complex and can be divided into the lower and upper dakendaban sub groups data from detrital zircons show that the protolith rocks of these two sub groups were deposited after 2 32 ga and 2 11 ga respectively the detrital zircon age and hf isotopic data and geological correlations suggest that the quanji massif was possibly fragmented from the tarim craton and the delingha complex was probably uplifted to become the major sedimentary source for the upper dakendaban sub group at 2 11 ga our zircon hf isotope compositions demonstrate important crustal growth at 2 6 2 7 ga and 2 5 ga together with the important magmatic activity at 2 2 2 4 ga and geological data our results seem to suggest that the tarim craton was part of the north china craton in its early evolutionary history but rifted away and joined the yangtze craton prior to the neoproterozoic

wave disturbance behind low crested structures diffraction and overtopping effects abstract in recent years the hydraulic performance of low crested structures has been widely studied both theoretically and through experimental analyses but only a few studies have been focused on the combined diffraction overtopping effects on wave transmission and induced wave currents in this paper hydraulic model tests conducted at the 3d wave basin of delft university of technology caceres et al 2008 were used to obtain and discuss two simple methods for predicting the wave height at the lee of a single detached breakwater of finite length and the related current regime for the first time diffraction effects are expressly accounted for the agreement with experimental data is encouraging the main objective of the paper is to aid engineers in the first stage of the design process when using a mathematical model could be unnecessarily excessive

environmental impacts of baltim and ras el bar shore parallel breakwater systems on the nile delta littoral zone egypt this study evaluates the impacts resulting from the construction of two large scale detached breakwater systems on the nile delta coast of egypt at baltim and ras el bar beaches 18 3 km shoreline length the two protective systems were installed in a water depth of between 3 and 4 m and consist of 17 units in total each 250 m long a comprehensive monitoring program spanning the years 1990 to 2002 was implemented and included beach nearshore profiles grain size distribution of seabed sand and information related to the background coastal processes evaluation of these systems concentrates on the physical impacts on coastal morphodynamics mitigation and their design implications the beach and nearshore sedimentation erosion accretion patterns and grain texture of seabed sediment in the study areas have been substantially disrupted due to the interruption of longshore transport by the shore parallel detached breakwaters rate of shoreline and seabed changes as well as alongshore sediment volume have been substantially affected resulting in accretion in the breakwater landward sides tombolo or salient followed by downdrift erosion the preconstruction beach erosion at baltim 5 m year and at ras el bar 6 m year has been replaced respectively by the formation of sand tombolo 35 m year and salient 9 m year on the other hand beach erosion has been substantially increased in the downdrift sides of these protective systems being 20 m year at baltim and 9 m year at ras el bar further seaward the two protective systems at baltim and ras el bar have accumulated seabed sand at maximum rates of 30 and 20 cm year and associated with downdrift erosion of 45 and 20 cm year respectively strong gyres and eddies formed in the breakwater gabs have drastically affected swimmers and subsequently caused a significant number of drownings each summer averaging 35 and 67 victims year at baltim and ras el bar beaches respectively this study provides baseline information needed to help implement mitigation measures for these breakwater systems

the llamas de cabrera gold district a new discovery in the variscan basement of northwest spain a fluid inclusion and stable isotope study the northwest of the iberian massif is well known to host numerous gold mineralizations which were exploited during roman times this study presents a multidisciplinary approach leading to the mineralogical fluid inclusions and geochemical characterization of the recently rediscovered roman gold district of llamas de cabrera gold occurs in extensional quartz veins hosted in the upper layers of the lower to middle ordovician armorican quartzite and occasionally in the overlaying middle ordovician slates from luarca formation the veins are characterized by multistage ore deposition developed along three hydrothermal stages as fe i as fe ii and au zn cu pb followed by late supergene alteration processes the fluid inclusion study undertaken on mineralized quartz revealed the presence of three types of fluids 1 co2 ch4 fluid inclusions 2 aqueous carbonic fluid inclusions dominated by co2 and subordinate ch4 related to quartz arsenopyrite pyrite deposition and 3 aqueous fluid inclusions related to the au sulfide deposition in conjunction with arsenopyrite geothermometry and fluid inclusion data an attempt was made to determine the p t conditions of ore formation changes occurred in the p t conditions fromarsenopyrite and pyrite deposition in quartz veins from aqueous carbonic fluids at 300 390 c and 200 220 mpa towards 180 310 c and b200 mpa at the stage of gold from aqueous fluids mixing of two aqueous fluids of relatively contrasted salinity were favorable factors for decreasing gold solubility and could allow gold deposition the 34s values are similar for the two as fe stages 8 0 to 16 3 and 9 0 to 19 5 respectively and for the post s1 pyrites from siliciclastic luarca formation suggesting a comparable sulfur source combining calculated 18o values of fluids of 6 7 to 9 4 with fluid inclusion data indicates that fluids of unknown origin are largely equilibrated withmetamorphic lithologies at medium high temperatures the ascent of some late variscan magmatic bodies not exposed at the present day erosion level provides the heat source for convective water circulation gold quartz veins from llamas de cabrera display similar features and processes to related deposits of similar type elsewhere in the variscan belt of western europe northwest and central western iberia french massif central bohemianmassif however llamas de cabrera shows certain differences such as the non appearance of igneous rocks in the area and the absence of sb rich minerals compared to some variscan sb au deposits including northern central and western iberia this last could probably be due to a greater depth of formation for the as au veins in comparison to sb au veins

using airborne lidar sensing technology and aerial orthoimages to unravel roman water supply systems and gold works in nw spain eria valley leon lidar technology based on earth s surface scanning allows the compilation of high resolution digital terrain models recently used in archaeological works for the discovery and description of heritage features such as ancient human made structures and building ruins it is particularly effective in areas with dense vegetation or difficult access where surveying becomes complicated among its main advantages over other traditional methods of archaeological research it highlights the possibility of controlling display parameters which in turn facilitates data analysis and interpretation in this study we present an integrated lidar and aerial photography data analysis in order to obtain a detailed map of ancient mining works within a small sector of the roman mining district in northwestern spain the presence of gold deposits led to intensive extractive work during the first century b p t although many of the mining activities were focused on the northwestern area of las medulas and omanas large deposits were also found along the duerna and eria river valleys our results complement previous work carried out in the eria area valderia providing new insights into the hydraulic engineering techniques and the geometry of the main roman exploitations this work highlights the scope of the ancient mining works and their impact on the landscape which are much greater and more important than previously thought

wave and flow response to an artificial surf reef laboratory measurements waves and currents are essential elements in the design of an artificial surfing reef asr asrs are primarily designed to optimize the surfing conditions i e increase the surfability of the incoming waves possibly in combination with the shoreline protection from erosion the currents generated by waves breaking on the asr play an important role in the surfability through the wave current interaction wci depending on the design the wci may negatively affect the surfability by causing the waves to break prematurely due to the current induced wave steepening in addition wave breaking tends to become more irregular due to the temporal variability of the underlying currents to mitigate the negative effects of wave breaking induced currents on the surfability three asr layouts are examined through detailed laboratory experiments the layouts differ in the alongshore separation distance between two symmetrical reef sides the ensuing flow circulations are examined in detail with both in situ current meters and video observations of surface drifters this is done for regular incident waves bichromatic incident waves and irregular incident waves all with equal energy a data analysis shows that for a given layout the mean flow patterns for regular bichromatic and irregular waves are qualitatively similar with oblique rip currents exiting at either side of the reef and strong flow circulations onshore of the gap in between the two reef sides increasing the separation distance leads to a significant reduction of the obliquely exiting rip currents at the outer sides of the reef but an increase in the flow circulation onshore of the gap this has a positive effect on the surfability by reducing the negative effects associated with the wci on the wave breaking thus providing longer rides

provenance constraints from detrital zircon u pb ages in the nw iberian massif implications for palaeozoic plate configuration and variscan evolution detrital zircons from pre orogenic upper ordovician to devonian low grade metasedimentary rocks have been dated by laser ablation inductively coupled plasma mass spectrometry la icp ms to 1 constrain the variations of zircon age populations within the autochthonous sequences of nw iberia 2 compare u pb detrital zircon ages with previous data 3 test the hypothesis of the armorica microplate as a peri gondwanan terrane separated from gondwana the similarity in the ages of detrital zircons found in the palaeozoic samples studied here to those published for the upper proterozoic lower cambrian and lower ordovician sediments of nw iberia argues against the separation of armorica and points to a common source area for all of the palaeozoic detrital formations of nw iberia the west african craton and the surrounding pan african belts la icp ms u pb dating of zircons from a synorogenic flysch preserved in klippen in the core of a syncline establishes a maximum depositional age for this deposit as early namurian this age is also a maximum age limit for thrusting and refolding in this part of the iberian massif correlation of the zircon age populations with published ages confirms the link between the emplacement of the allochthonous complexes of nw iberia and synorogenic sedimentation

quantification of changes in current intensities induced by wave overtopping around low crested structures the phenomenon of overtopping is traditionally studied for well emerged harbour structures and often focuses on safety and stability in this paper laboratory tests are presented and analysed to sharpen the hypothesis that overtopping is capable of changing the horizontal circulation pattern around low crested structures a unique data set from laboratory experiments was acquired in the wave basin at delft university of technology the experiments were performed using an emerged impermeable low crested structure three freeboards and three different wave conditions for each freeboard and yielded nine different combinations of set up and overtopping driving forces using this information it was possible to quantify the changes in cross shore and longshore velocity induced by the overtopping and the set up changes under the different freeboard and wave conditions described it is found that overtopping enhances the outgoing flows longshore velocities parallel to the structure away from the lee side of the structure and dampens the water level gradient driven flow towards the structure

ages and geodynamic settings of xilamulun mo cu metallogenic belt in the northern part of the north china craton abstract the xilamulun belt along the northern part of the north china craton is located in eastern segment of the central asian orogenic belt and has great economic potential for mo cu mineralization more than ten medium to large ore deposits have been discovered in this region in the recent years the major types of mineralization type include porphyry chehugou mo cu kulitou mo cu xiaodonggou mo and jiguanshan mo quartz vein nianzigou mo xinjing mo epithermal hongshanzi mo u and alteration assemblage liulingou mo the timing of mineralization was previously thought to be yanshanian 208 290 ma however indosinian 260 208 ma ages for intrusions and mineralization have been recognized in recent years based on geochronologic data and regional geological evidence it is suggested that the mineralization in the xilamulun belt was formed during multiple events the mineralization processes are related to a post collisional extension stage 258 210 ma with the generation of the porphyry molybdenum copper deposit a tectonic stress transformation from ns to ew 185 150 ma that gave rise to vein or porphyry molybdenum deposit and a lithospheric thinning stage 140 110 ma with porphyry molybdenum deposit

a mixed solution for a highly protected coast punta marina northern adriatic sea italy abstract spatial data collected over three years are presented to assess the impacts of a mixed intervention carried out in a low sandy microtidal highly protected beach punta marina italy coastal erosion started in the 1980s principally due to reduction of fluvial sediment discharges wave attack and both anthropic and natural subsidence the intervention consisted in a small beach nourishment shallow feeder berm construction and the placement of an artificial reef to retain the sand fill topo bathymetrical surveys with real time kinematic rtk gps multi beam surveys sediment samplings wave data records dive inspections and numerical simulations were undertaken over a 3 year monitoring period to analyse the process response mechanism of this intervention to assess the main factors affecting the performance of the mixed intervention and the possibility of using fine sediments for nourishment practices the results reveal a generally positive impact characterised by short term beach stability that was mostly due to the feeder berm effect the beach nourishment had a short but direct effect on the beach width while the feeder berm dissipated wave energy and successively fed the nearshore with eroded sediment on the other hand the artificial reef did not retain the sand but rather induced rip currents that increased eddy circulation and therefore promoted the loss of offshore sediment settlement and scouring problems were also observed and the structure s failure induced safety problems the results confirm that a feeder berm operation carried out with fine sediment represents a good solution although particular attention must be paid to the relationship between sediment grain sizes volume and location of the nourishment as they are the key factors for good performance finally the cross shore sediment transport represents a critical factor that controls the coastal evolution of beaches bounded by hard structures and assimilated to the littoral cell consequently it should be better integrated within the nourishment design and model setting

nourishing the shoreface observations and hindcasting of the egmond case the netherlands abstract although beach nourishment policy in the netherlands is generally successful in maintaining the 1990 shoreline the efficiency of nourishments at several locations along the north sea coast is unacceptably low these locations are identified as erosion hotspots egmond aan zee is such a hotspot the bathymetric longshore irregularities make this coastal stretch highly susceptible to rip currents and horizontal circulations which transport large volumes of nourished sand to the sea in 1999 an alternative nourishment design was implemented this consisted of a shoreface nourishment at the outer bar at 7 5 m depth combined with a nourishment of the beach behind it high resolution bathymetric surveys carried out with the wesp revealed that the shoreface nourishment resulted in a significant shoreward migration of the outer bar during 1999 2001 after 2 years the system started to return to its natural dynamic equilibrium and lost the positive influence of the shoreface nourishment area shoreward movement of bars and increase of bar height which forms the first defense line of the mainland against the sea and positive contribution to the sand budget which increased as a result of the nourishment after 3 years may 1999 to april 2002 the sediment volume still had an increase of 477 500 m3 45 of the applied sand relative to may 1999 the shoreface nourishment area did not have a direct effect on the beach the shoreface nourishment area probably will have to be maintained to retain the sediment on the beach in the long run in egmond the shoreface nourishment started to disappear before the sediment could reach the beach the time scale of sediment feed to the beach zone probably is of the order of 5 10 years the shoreface nourishment seems to function as a reef creating a lee side effect that influences both cross shore and longshore sediment transport resulting in two main hypotheses firstly the longshore effect in which large waves break at the shoreface nourishment cause a calmer wave climate shoreward of the shoreface nourishment area and a reduction of the longshore current the shoreface nourishment partially blocks the wave driven longshore current secondly the cross shore effect in which shoaling waves generate onshore transport these hypotheses are supported by generated model results with both a process based profile model unibest tc and a process based coastal area model delft3d mor the unibest tc model was able to predict the detachment of the outer bar from the shoreface nourishment and to some extent the shoreward bar movements in the lee of the shoreface nourishment area the model found an increase in sediment confirming the shielding effect of the shoreface nourishment area the delft3d model found as a result of the shoreface nourishment area a decrease of the flow velocity and the wave height just shoreward of the shoreface nourishment area the model was able to predict the similar trend in sedimentation erosion pattern although the intensities were smaller in the lee of the shoreface nourishment area a clear sedimentation was found erosion was found south and seaward of the shoreface nourishment area the modeled profiles did not follow the measured profile changes the separation of the shoreface nourishment from the outer bar and the shoreward migration of the bars could not be accurately modeled because the cross shore transport caused by wave asymmetry is not taken into account in the standard version of delft3d these results were in line with the expectations

numerical simulation of wave overtopping at coastal dikes and low crested structures by means of a shock capturing boussinesq model abstract in this paper a shock capturing numerical model based on the combined solution of boussinesq and nonlinear shallow water equations is applied to the simulation of wave runup overtopping and wave train propagation over impermeable emerged and low crested structures in order to improve the performances of the scheme at wet dry interfaces a numerical treatment is introduced to provide well balancing of advective fluxes and source terms one and two dimensional test cases are presented to validate the performances of the model under both regular and irregular wave conditions

sinking of concrete modules into a sandy seabed a case study abstract three submerged coastal structures on the sandy seabed at santa maria del mar smm beach in southwest spain were monitored during the six months after installation starting in november of 2005 the monitoring evaluated the self burial phenomenon of the 40 precast modular concrete elements of the three structures assessment included scouring around the structures their vertical movement the sinking velocity of the modules and the resulting beach profiles pressure sensors and precision topographies permitted continuous monitoring of the self burial process for the first time in a full scale case comparison of two bathymetries one performed immediately prior to installation and another performed six months after installation indicated slight accretion of the seabed whereas intermediate topographic surveys indicated extensive scouring around the structures the three structures began sinking into the sandy bottom platform immediately after placement and continued until they reached the rocky bottom this study implemented a new methodology using pressure sensors attached to the concrete modules to monitor the structural sinking unexpectedly the average sinking speed was extremely rapid at approximately 3 6 cm day 50 of the height of the element was reached in three to six weeks the results of this study are also compared with the results of other full scale cases among other conclusions data from this study indicated that the sinking rate of the modules in smm beach was one order of magnitude greater than the other values

laboratory measurements of the vertical structure of rip currents 1 this paper describes the three dimensional variation of rip currents through the use of experimental measurements of rip currents in a directional wave basin the rip currents are unstable appearing sporadically at any given location the vertical profile of the rip current is found to vary from depth uniform inside the channel to depth varying further offshore offshore from the channel the rip current has much stronger velocities at the surface than near the bottom the instantaneous profiles twist rapidly over depth farther offshore and are fairly uniform in the channel the depth variations are shown to be sensitive to the total volume flux in the rip

interaction of two successive alpine deformation fronts constraints from low temperature thermochronology and structural mapping nw iberian peninsula the lateral termination of the alpine pyrenean orogen relief onshore is located in the nw iberian peninsula it overlies a variscan basement iberian massif where the sedimentary record of the alpine tectonic is very scarce thus the characterisation of the tectonic evolution of the lateral termination is difficult and timing and geometries of the main tectonic structures remain unclear combining the tectonothermal histories obtained by modelling of the apatite fission track data aft with structural mapping allows for a comparative study of the different tectonic scenarios and deformation transfer in the lateral termination of an orogen aft ages for the studied area vary from 53 5 12 9 and 222 12 ma from late triassic to early eocene the beginning of the cenozoic cooling episodes is in agreement with the infilling of the tertiary basins late eocene or oligocene calculated uplift for the alpine orogeny is around 2 400 m the cantabrian mountains were uplifted and emplaced southwards and the main period of exhumation began in the palaeogene at rates of 0 02 mm a and continued during the neogene at rates of 0 06 mm a however the galaico leoneses mountains located to the south of the studied area were uplifted and emplaced northwards during the neogene showing more rapid uplift rates of 0 08 mm a suggesting that the western termination of the alpine pyrenean orogen relief is the result of the successive interaction of two alpine deformation fronts

shoreline response to multi functional artificial surfing reefs a numerical and physical modelling study the results of a series of 2dh numerical and 3d scaled physical modelling tests indicate that processes governing shoreline response to submerged structures such as artificial surfing reefs are different from those associated with emergent offshore breakwaters unlike the case of emergent offshore breakwaters where shoreline accretion salient development is expected under all structural environmental conditions the principal mode of shoreline response to submerged structures can vary between erosive and accretive depending on the offshore distance to the structure the predominant wave incidence angle and structure crest level also have important implications on the magnitude of shoreline response but not on the mode of shoreline response i e erosion vs accretion based on the results obtained here a predictive empirical relationship is proposed as a preliminary engineering tool to assess shoreline response to submerged structures

geochronology geochemistry and petrogenesis of the late palaeoproterozoic a type granites from the dunhuang block se tarim craton china implications for the break up of the columbia supercontinent the discovery of c 1 77 ga a type granite in the tarim craton tc provides the first evidence that supports an extensional event related to fragmentation of the columbia supercontinent in the late palaeoproterozoic we present laser ablation inductively coupled plasma mass spectrometry la icp ms zircon u pb ages lu hf isotopic data and the whole rock geochemical and nd isotopic data of a type granites in the dunhuang area in the se tarim craton zircon u pb dating for three granite samples indicate that they were emplaced at c 1 77 ga zircons from these granites have e hf t values ranging from 5 9 to 8 7 corresponding to two stage model ages of 1 9 2 7 ga these granites exhibit the following petrological geochemical characteristics that are typical of a type granite a high content of sio 2 and alkalis i e high k 2 o na 2 o with k 2 o na 2 o 1 enrichment of high field strength elements hfse and rare earth elements ree except for eu and extreme depletion of ba sr p ti and eu b 10000 ga al ratios in the dunhuang granites of 3 5 4 4 with an average value of 3 79 which is similar to the global average of 3 75 for a type granites c the presence of characteristic minerals such as amphibole sphene and perthite and d zirconium saturation temperature results indicate that the dunhuang granites have high initial magmatic temperatures in the range 887 950 c similar to those of typical of a type granites whole rock e nd t values range from 2 5 to 6 2 and t dm model ages from 2 3 to 2 7 ga nd hf isotopic and whole rock geochemical data indicate that these granites were most likely derived from the late archean crustal source in a post collisional post orogenic extensional tectonic environment the late palaeoproterozoic a type granites in the tc could be correlated with those of the north china craton ncc india and the canadian shield thus demonstrating extensional tectonics and break up of the columbia supercontinent

detection of exposed and subsurface archaeological remains using multi sensor remote sensing abstract multi sensor airborne remote sensing has been applied to the itanos area of eastern crete to assess its potential for locating exposed and known buried archaeological remains and to delineate subsurface remains beyond the current limits of ground geophysical data in order to permit future targeted geophysical surveys and archaeological excavations a range of processing techniques e g reed xiaoli anomaly detection have been applied to the casi atm and lidar data in order to detect anomalies based on the premise that buried remains are likely to alter the physical and chemical characteristics of the soil compared with those of the surroundings due to variations in soil depth and drainage through a combination of casi atm and lidar data surface remains have been classified and mapped effectively using an object oriented approach the detection of subsurface remains is more problematic however the thermal data is most promising in this respect the value of capturing multi or hyperspectral data at a high spatial resolution has been demonstrated as well as the additional benefits of combining these with airborne lidar

an experimental study of rip channel flow a laboratory study of the flow over a bar with a single rip channel has been performed first the well known pattern of a bar circulation cell with a strong offshore directed current out through the rip channel and a weaker onshore directed return flow over the bar is documented then measurements of the three dimensional structure of the flow in the area where the rip channel the bar and the trough meet and well inside the rip channel are presented these measurements reveal that 3d effects play an important role and that a depth integrated viewpoint may not always be sufficient for predicting the flow in the near bed region particle tracking experiments illustrate the near bed flow pattern over the entire area these demonstrate how the overall trajectory pattern changes as a function of the distance of wave breaking from the bar crest for some conditions the rip current is fed from the trough and for other conditions it is fed directly from the bar both the 3d measurements and the trajectory tests show the existence of a weaker onshore directed near bed drift in the area where the rip current ceases finally in a series of sensitivity tests measurements of the rip current intensity for different wave climate and water level conditions reveal a strong correlation between the rip current intensity and the wave height both normalized

note on the paper by guochun zhao simon a wilde sanzhong li min sun matthew l grant and xuping li 2007 u pb zircon age constraints on the dongwanzi ultramafic mafic body north china confirm it is not an archean ophiolite

swash zone boundary conditions for long wave models abstract in this note a description of swash zone boundary conditions for implementation in wave resolving and wave averaging long wave models is given along with a discussion of the role of such conditions on the modelling of the entire surf zone hydro morphodynamics

crustal thickening and deformation sequence in the footwall to the suture of the variscan belt of northwest spain abstract the sequence of formation and propagation of structures as well as the evolution of crustal thickening in the variscan belt of northwest spain are proposed in this paper the foreland of this mountain belt shows thin skinned tectonics a polyphase deformation with associated regional metamorphism is recognized in the hinterland zones two important culminations the narcea and lugo antiforms are present in an e w cross section through the footwall to the suture of this orogen such culminations are derived from the stacking of several thrust systems generated during two successive periods the sequence of thrust emplacement helps to clarify the formation of different types of structures at the same time in different places in the orogen

analysis of the effects of different storm events on shoreline dynamics of an artificially embayed beach a five year dataset of argus derived mean intertidal positions has been analysed to characterize the shoreface variability in a beach protected by a system of groynes and a parallel low crested structure lido di dante ravenna italy for the period 2004 2009 84 intertidal beach bathymetries and shorelines at the zero sea level were used as indicators to assess beach changes in between a number of selected surveys and to determine characteristic patterns of the beach response to storm events from different directions variations in the shoreline at the zero sea levels have been quantified and analysed in conjunction with nearshore wave conditions and provenance linked to storm events these fall into two categories 1 storm events occurring during bora north eastern wind conditions and 2 storm events occurring during scirocco south eastern wind conditions the results show that apart from main beach advances of the whole protected beach due to nourishments periodically carried out a marked variability is observed among the four sub cells into which the shoreface behaviour has been separately analysed in particular a dependence of beach rotation in the artificially embayed area on the substantially bi directional wave climate has been shown bora and scirocco storm events produce shoreline rotation in counterclockwise and clockwise directions respectively due to the occurrence of longshore currents in the opposite direction in the nearshore an attempt was made to correlate the shoreface dynamics for the main rotation events 14 selected ones to the wave attack intensity as the total energy flux due to storm events a relationship seems to occur for each storm category between the shoreline displacements estimated for each sub cell and the total energy flux computed for inter survey periods supporting the occurrence of a link between the observed morphological changes and the hydrodynamic forcing associated with storm events in the five year monitoring period copyright 2011 john wiley sons ltd

geochronological and geochemical constrains on petrogenesis of the huangyangshan a type granite from the east junggar xinjiang nw china abstract the huangyangshan pluton occurs in the kalamaili region which is situated in the central part of the central asian orogenic belt east junggar xinjiang nw china the granitoid rocks are composed of medium grained biotite richterite arfvedsonite alkali feldspar granite fine grained arfvedsonite alkali feldspar granite and microgranular enclaves the granites have a pronounced a type affinity they are metaluminous to weakly peraluminous and calc alkaline to alkaline in composition with high concentrations of na 2 o k 2 o varying from 8 4 to 9 2 wt high feot mgo and 10 000 ga al ratios low abundances of cao mgo and tio 2 enrichment in some liles such as rb and th and hfses such as zr y and rees except eu depletion in sr and ba moreover they display characteristic tetrad ree patterns and non charac trace element behavior which is well demonstrated in highly differentiated rocks with strong hydrothermal interaction the u pb zircon la icp ms ages of the host rocks and enclaves are 311 5 ma and 300 6 ma respectively the similar of these two ages suggests that host rocks and enclaves formed at a same time furthermore the time span closely corresponds to known ages of post collisional a type granitoids of the junggar terrane geochemical geochronological and isotopic data e nd t in the range 5 2 to 6 6 and i sr mostly in the range 0 7031 0 7041 suggest that the huangyangshan intrusions and the enclaves are of mixed origin and are most probably formed by the interaction between the lower crust and mantle derived magmas in the late carboniferous post collisional tectonic setting a 2 type granite the magma for the huangyangshan granites was derived by partial melting of an enriched subcontinental lithospheric mantle sclm that was modified by slab derived components from an earlier subduction event this melting resulted from heat supplied from the asthenosphere through an opening created during the break off of an oceanic slab this further proves the important contribution of the late paleozoic granitic magmatism in terms of vertical crustal growth in northern xinjiang

beach morphologies induced by breakwaters with different orientations abstract a desired outcome in the construction of a detached emerged breakwater is the formation of an accretionary salient in its lee to augment the beach improve beach amenity and provide an additional buffer from storm waves the extent to which this salient forms and its morphology are strongly controlled by the breakwater geometry with respect to the original shoreline sediment availability and local wave climate the purpose of this paper is to identify how breakwater geometry and orientation of gaps between individual breakwaters alter the direction of waves entering the gaps and change the asymmetry of the salients four distinct breakwater sites along the emilia romagna coastline in northern italy were chosen for a detailed field and desktop study comprising three dimensional topographic and bathymetric surveys sediment sampling lidar flights and historical shoreline mapping the orientations of the shorelines at these four sites range over 43 resulting in different exposures to the dominant waves the oblique orientations of the gaps between individual breakwater segments at three of the four sites effectively create a gap window between breakwaters favoring the exposure of short period waves from the north and diminishing the effect of longer waves from the dominant east salients can be symmetrical despite an acute angle of approach of the dominant deep water waves where refraction is enhanced by offshore topography and breakwaters are parallel to the shore waves approaching normal to the gap window undergo less diffraction due to their shorter length relative to the gap window width and undergo less attenuation by breaking and bottom friction if they are locally generated and have short periods greater breaking wave energy on the gap facing slope of the salient can create shoreline and morphological asymmetry the implication is that breakwater orientations can be designed or altered to selectively dampen or facilitate wave energy to enhance sediment transport in a desired direction provided that breakwaters are not too far offshore and sediment availability is not restricted to affect salient formation adjusting exposure via gap orientation can create morphologies that cannot be inferred from process dominant conditions

visualization of lidar derived relief models for detection of archaeological features abstract this paper presents visualisation techniques of high resolution digital elevation models dems for visual detection of archaeological features the methods commonly used in archaeology are reviewed and improvements are suggested one straightforward technique that has so far not been used in archaeology the shift method is presented the main purpose of this article is to compare and evaluate different visualisation methods two conclusions have been reached where a single method must be chosen for printing or producing digital images for non professionals the use of sky view factor or slope gradient is endorsed both presented in greyscale otherwise interpreters should choose different techniques on different terrain types shift on flat terrain sky view factor on mixed terrain slope gradient on sloped terrain and sky view factor preferably as a composite image with slope gradient on rugged terrain

lower paleozoic extensional tectonics in the limit between the west asturian leonese and central iberian zones of the variscan fold belt in nw spain the limit between the west asturian leonese and central iberian zones in the nw of the iberian peninsula is described in the area of caurel truchas provinces of orense and leon from the distribution of the sedimentary formations and the variscan structures it is inferred that the transition between the two zones was a fault system which was active during at least the ordovician and lower silurian the faults were supposedly normal though they had probably some strike slip component and gave rise to a half graben in which a syn rift sequence was deposited the latter underwent inversion at the onset of the variscan tectonism producing a ramp anticline syncline pair that forms the more important folds in the area the varying geometry of these folds is interpreted partly as being due to the existence of previous en echelon folds related to the strike slip component of the faults and partly as a result of the variable intensity of the shear strain undergone during the first variscan phase

early paleoproterozoic magmatism in the quanji massif northeastern margin of the qinghai tibet plateau and its tectonic significance la icpms u pb zircon geochronology and geochemistry abstract the quanji massif is located on the north side of the qaidam block and is interpreted as an ancient cratonic remnant that was detached from the tarim craton there are regionally exposed granitic gneisses in the basement of the quanji massif whose protoliths were granitic intrusive rocks previous studies obtained intrusion ages for some of these granitic gneiss protoliths the intrusion ages span a wide range from 2 2 ga to 2 47 ga this study has determined the u pb zircon age of four granitic gneiss samples from the eastern central and western parts of the quanji massif cl images and trace elements show that the zircons from these four granitic gneisses have typical magmatic origins and experienced different degrees of pb loss due to strong metamorphism and deformation la icpms zircon dating yields an upper intercept age of 2381 41 2 ma from monzo granitic gneiss in the hudesheng area and 2392 25 2 ma from granodioritic gneiss in the mohe area eastern quanji massif and 2367 12 2 ma from monzo granitic gneiss in the delingha area central quanji massif and 2372 22 2 ma from monzo granitic gneiss in the quanjishan area western quanji massif these results reveal that the intrusive age of the protoliths of the widespread granitic gneisses in the quanji massif basement was restricted between 2 37 and 2 39 ga indicating regional granitic magmatism in the early paleoproterozoic perhaps related to the fragmentation stage of the kenorland supercontinent geochemical results from the granodioritic gneiss from the mohe area indicate that the protolith of this gneiss is characterized by adakitic rocks derived from partial melting of garnet amphibolite beneath a thickened lower crust in a rifting regime after continent continent collision and crustal thickening genetically similar to the ttg gneisses in the north china craton this suggests that the quanji massif had a tectonic history similar to the archean central orogenic belt of north china craton during the early paleoproterozoic we tentatively suggest that the quanji massif and the parental tarim craton and the north china craton experienced rifting in the early paleoproterozoic after amalgamation at the end of the archean the tarim craton and north china craton might have had close interaction from the late neoarchean to the early paleoproterozoic

laboratory experiments on low crested breakwaters abstract new unique laboratory experiments on low crested structures lcss have been performed within the delos project the experiments were carried out in three european laboratories aiming at extending and completing existing available information with respect to a wide range of engineering design properties such as structural stability wave and current flows and wave transmission 3d wave basin tests were performed to provide information especially about the wave obliquity where almost no research has been done before flow velocities inside and close to the surface of structures were studied in a wave channel at small scale and scale effects regarding wave transmission and reflection were studied in a wave channel at a large scale facility the paper describes the experiments and associated databank with respect to objectives test program set ups and measurements results guidelines and recommendations elaborated from the tests are included in the other companion papers of the coastal engineering special issue on delos

a simplified model of rip currents systems around discontinuous submerged barriers although in the last years several numerical models have been shown to be able to reproduce rip currents around discontinuous submerged barriers only few simple methods of practical use are available for estimating main flow parameters like the current intensity and the mean water levels in terms of geometrical barrier and gap dimensions parameters and wave characteristics the aim of this paper is to present a simplified model to be used for an easy estimate of these important rip currents parameters the model which is based on rough simplifications considers the area between the shoreline and the barrier as a reservoir in which water is pumped by breaking short waves across the barrier and from which water flows out at the gap four equations mass and momentum conservation across the barrier free discharge at the gap and balance of water pumped towards the shore and freely flowing offshore are used to derive one single model equation that can be solved for the wave set up and subsequently used for rip current velocity calculation two free parameters appear in this equation which respectively account for energy losses at the gap cv and bed friction the proposed model is validated against available laboratory experiments to show its ability in providing reasonable estimates of the desired parameters that may be considered by engineers adequate at the preliminary design stage of submerged breakwaters and that can be used for evaluating hydrodynamics on barred beaches

three dimensional investigations of wave overtopping on rubble mound structures to study the influence of wave obliquity and directional spreading on wave overtopping of rubble mound breakwaters a total of 736 three dimensional model tests were carried out at aalborg university the results of these tests are presented and analysed in this paper yielding a new empirical reduction factor to describe the influence of wave obliquity and directional spreading on the average wave overtopping discharges the study shows that perpendicularly incident long crested waves result in conservative values of the overtopping discharge for the tested cross section

automated feature extraction for prospection and analysis of monumental earthworks from aerial lidar in the kingdom of tonga abstract recent lidar light detection and ranging survey in tonga has documented a dense and complex archaeological landscape particularly on the principal island of tongatapu among the features revealed by the lidar are a profusion of earthen mounds most of which are associated with residence sporting or burial in the period 1000 1850 ce for identification and mapping of the mounds we use and evaluate two automated feature extraction afe techniques object based image analysis and an inverted pit filling algorithm imound accuracy of these methods was measured using an f1 score harmonic mean of precision and recall variable afe results indicate that continual and iterative fine tuning is required successful mapping of some 10 000 mounds on tongatapu reveals a distinct spatial structure that relates to traditional land division and tenure

modelling of waves and currents around submerged breakwaters abstract recent experimental data collected during the delos project are used to validate two approaches for simulating waves and currents in the vicinity of submerged breakwaters the first approach is a phase averaged method in which a wave model is used to simulate wave transformation and calculate radiation stresses while a flow model 2 dimensional depth averaged or quasi 3d is used to calculate the resulting wave driven currents the second approach is a phase resolving method in which a high order 2dh boussinesq type model is used to calculate the waves and flow the models predict wave heights that are comparable to measurements if the wave breaking sub model is properly tuned for dissipation over the submerged breakwater it is shown that the simulated flow pattern using both approaches is qualitatively similar to that observed in the experiments furthermore the phase resolving model shows good agreement between measured and simulated instantaneous surface elevations in wave flume tests

onshore scour characteristics around submerged vertical and semicircular breakwaters abstract a laboratory study is presented herein investigating the two dimensional onshore scour along the base of submerged vertical and semicircular breakwaters experiments were conducted with normally incident monochromatic waves breaking at the breakwater on both sloping and horizontal sandy bottoms a principle conclusion of this investigation is that the characteristics of onshore breakwater scour are independent of submerged breakwater shape type it is also concluded that the onshore scour patterns can be divided into two distinct regimes that solely rely on the keulegan carpenter number kc h i w bw wbw breakwater crest width hi incident wave height for kc values larger than the scour forms detached from the breakwater while for kc values smaller than or equal to the scour occurs attached to the onshore breakwater face three important scour characteristics are investigated maximum scour depth smax scour length ls and the distance of smax location from the onshore breakwater face ds smax value is observed to be regime independent and rely on both kc and the mobility number h i t sinh k h 2 g d g reduced gravitational acceleration d median diameter of the sediment k wave number h still water depth t wave period while ls and ds are observed to be regime dependent and rely only on kc semi empirical parameterizations to predict smax ls and ds values for onshore breakwater scour are proposed

stratigraphic and sedimentary records of the rift to drift evolution of the northern north china craton at the paleo to mesoproterozoic transition article i nfo this paper presents a stratigraphic and sedimentary study of late paleoproterozoic to early mesoproterozoic successions of the northern margin of the north china craton including the changcheng and nankou groups a reconstruction of the tectono sedimentary history of these two groups demonstrates that the northern north china craton experienced a two stage evolution as recorded by the changcheng group early synrift subsidence and sedimentation were controlled by normal faults and accompanied by volcanism in contrast a late postrift stage was characterized by broad subsidence and widespread occurrence of shallow marine clastic and carbonate rocks a transgressive unconformity is identified and together with its time equivalent conformable contact clearly separates the synrift and postrift sequences the diachronous unconformity can be related to continental rifting and the separation of the north china craton from the adjacent india craton at roughly 1600 ma and is thus interpreted as a breakup unconformity this age of ca 1600 ma is constrained by newly reported precise shrimp u pb zircon ages of transgressive deposits in the overlying mesoproterozoic dahongyu and gaoyuzhuang formations just coincident with the paleoproterozoic to mesoproterozoic transition the 1600 ma time estimate for the tectonic departure of the north china craton from the india craton is comparable with the timing for the breakup of columbia a pre rodinia supercontinent containing almost all of the earth s continental blocks

diachronous post orogenic magmatism within a developing orocline in iberia european variscides 1 u pb zircon crystallization ages of 52 late variscan granitoid intrusions from nw iberia 19 from new data 33 from previous studies constrain the lithospheric evolution of this realm of the variscan belt of western europe and allow assessment of the relationship between oroclinal development and magmatism in late carboniferous early permian times the u pb ages in conjunction with a range of geological observations are consistent with the following sequence of events i oroclinal bending starts at 310 305 ma producing lithospheric thinning and asthenospheric upwelling in the outer arc of the orocline accompanied by production of mantle and lower crustal melts ii between 305 and 300 ma melting continues under the outer arc of the orocline central iberian zone of the iberian variscan belt and mid crustal melting is initiated coevally the lithospheric root beneath the inner arc of the orocline thickened due to progressive arc closure iii between 300 and 292 ma foundering of the lithospheric root followed by melting in the lithospheric mantle and the lower crust beneath the inner arc due to upwelling of asthenospheric mantle iv cooling of the lithosphere between 292 and 286 ma resulting in a drastic attenuation of lower crustal high temperature melting by 285 ma the thermal engine generated by orocline driven lithospheric thinning delamination had cooled down beyond its capability to produce significant amounts of mantle or crustal melts the model proposed explains the genesis of voluminous amounts of granitoid magmas in post orogenic conditions and suggests that oroclines and similar post orogenic granitoids common constituents of numerous orogenic belts may be similarly related elsewhere

space and time in the tectonic evolution of the northwestern iberian massif implications for the variscan belt recent advances in geochemical studies of igneous rocks isotopic age data for magmatism and metamorphism quantitative pressure temperature p t estimates of metamorphic evolution and structural geology in the northwestern iberian massif are integrated into a synthesis of the tectonic evolution that places the autochthonous

wave overtopping and piling up at permeable low crested structures the paper aims at providing a simple model for evaluating piling up overtopping filtration and rip currents for low crested structures the model is essentially based on mass and momentum balance and on resistance laws that relate piling up and mass fluxes a procedure is suggested and validated against 2d and 3d experimental data this procedure is innovative with respect to existing formulations since it applies both to emerged and submerged structures and it simultaneously accounts for structure permeability return flow through gaps and dissipative effects

equilibrium beach profile model for perched beaches abstract a beach profile equilibrium model for perched beaches is presented the model assumes that wave reflection at the seaward and leeward sides of the breakwater is the most important process that modifies dean s equilibrium profile model for non perched beaches the influence of wave breaking over the submerged structure is also discussed several laboratory data sets are used to analyze the merit of the proposed model for describing the equilibrium condition of a perched beach a good comparison is obtained results show that if the ratio between the water depth above the submerged structure d and the water depth at the toe of the structure h e is large d h e 0 5 only minor advance of the shoreline is achieved with the construction of a toe structure a considerable advance is obtained for d h e less that 0 1 in these situations however resonant effects may result in an inefficient structure the proposed model is used to provide an estimation for the required sand volume and the associated beach advance for the case of narrow breakwaters

hydrodynamic and morphodynamic response of isolated and multiple low crested structures experiments and simulations abstract low crested structures for beach defence purposes are frequently configured in the form of cells this paper investigates the hydrodynamic and morphological response of such defence schemes by means of laboratory experiments and numerical simulations experiments were carried out at the large mobile bed basin of the laboratorio di idraulica costiera of the politecnico di bari it tests peculiarity is the simultaneous simulation of three different types of lateral confinement a channel representative of an indefinitely long structure and two areas with narrow and wide gaps representative of a common scheme and of an almost isolated structure respectively submerged zero freeboard and emerged conditions were tested a typical storm of the northern adriatic sea was reproduced by 6 wave attacks water level and currents were measured in front and behind the structures at gaps and roundheads results focusing on rip current intensities and piling up are presented and discussed an extensive plan view of wave intensities and flow patterns inside the basin is provided through numerical simulations with mike 21 numerical suite the sand bed was surveyed along 30 profiles covering the narrow gap area and the isolated structure roundheads for the submerged conditions tests 15 of these profiles and the shoreline position were monitored after each step of the simulated storm average and maximum values of local erosion at the structure toe are presented time evolution of erosion at gaps is related to the main hydrodynamic variables through bijker sediment transport formula evaluation of volume changes in the protected area shows that sand is in average trapped behind the barriers being transported offshore from gaps and returning inshore over the crest the observed and reconstructed transport mechanism is a combination of bed load and suspended transport the latter being slightly more important bed level changes are well predicted by morphodynamic simulations performed with mike 21 cams

archaeological prospection of forested areas using full waveform airborne laser scanning abstract airborne laser scanning als is a potential tool for recognising and measuring topographic earthwork features in wooded areas to explore its potential for archaeological reconnaissance in a densely forested area a test scan covering an iron age hillfort in the eastern part of austria was carried out during the first phase of a research project als sensors can penetrate vegetation canopies allowing the underlying terrain elevation to be accurately modelled the latest generation of airborne laser scanners was used in the project this sensor digitally records the entire waveform of the received laser echoes we argue that the digital terrain model dtm generated from entire waveform als data could be classified with greater confidence providing a more accurate dtm than with previous als devices the processing algorithms used to create the interpretative dtm are discussed in detail using the described procedures it was possible to remove most of the forest canopy and understorey brushwood and low level vegetation covering the archaeological features the als dtm was compared with a detailed topographic mapping of the visible archaeological traces collected by a terrestrial survey significantly very low earthwork features which were not recognized by the trained surveyors in the field were identified in the als derived dtm therefore in this study area als has been demonstrated as an important tool for systematic archaeological prospection in vegetated areas there are however some restrictions which are discussed in the paper

wave transmission and reflection at low crested structures design formulae oblique wave attack and spectral change abstract a part of the delos research focused on wave transformation at low crested structures called lcs this paper gives a summary of all results wave transmission on rubble mound structures has been subject for more flume tests in the delos programme and simultaneously an existing database has been increased extensively by receiving data from other researchers in the world this new database consists of more than 2300 tests and has been used to come up with the best 2d wave transmission formula for rubble mound lcs although not necessarily new as existing ones have been evaluated oblique wave attack on lcs was a second objective within delos results were analysed leading to new empirical transmission formulae for smooth lcs and to conclusions on 3d effects for both rubble mound and smooth lcs the spectral shape changes due to wave transmission and this change has been subject of analysis for all new test data described above although analysis has not been finished completely former assumptions on spectral change were more or less confirmed finally some analysis was performed on reflection at lcs and a first formula was derived to take into account the effect that wave overtopping or transmission reduces reflection and must be dependent on the crest height of the structure

full scale monitoring study of a submerged breakwater palm beach florida usa abstract in an attempt to reduce beach erosion and wave impact on a protective seawall an experimental proprietary submerged breakwater reef of 1 260 m length was installed in a water depth of approximately 3 m off the town of palm beach florida to provide a basis for evaluating the effects of this installation a comprehensive field monitoring program was carried out and included wave measurements beach and offshore profiles settlement of the units local scour data and information related to the background coastal processes the system consists of 330 units 57 of which were installed in the summer of 1992 and the remainder in the summer of 1993 monitoring surveys available up to june 1995 are presented herein the wave height reduction attributable to the reef ranges from 5 for the lower waves and higher tides to 15 for the higher waves and lower tides the profile data documented erosion in the entire monitored area with the greatest erosion landward of the reef changes in profile data were consistent with and are interpreted as due to water conveyed over the submerged breakwater as mass transport a partial ponding of this water due to its return flow being impeded by the presence of the breakwater resulting in a portion being redirected as longshore currents these longshore currents transport sand from landward of the breakwater with deposition occurring near the south end of the system in the direction of the predominant natural transport although these breakwater induced longshore currents were not documented in the monitoring program the mechanisms are supported by the patterns of erosion and deposition by a model study carried out to evaluate installation of a submerged breakwater at a different location and by previous documentation and discussion of the phenomenon in the available literature results obtained here are interpreted in terms of design implications

modelling morphological processes in the vicinity of shore parallel breakwaters abstract a coastal area morphological modelling system is used to investigate the planform development tombolo or salient behind a single surface piercing detached breakwater a quasi three dimensional q3d description of the flow and the sediment transport together with a revised bed level update scheme were incorporated recently in the morphological modelling suite applied in the present investigation the q3d sediment transport formulation used allows simulating beach profile evolution and planform development simultaneously several breakwater layouts were investigated in a series of tests in which the incident wave condition was taken as constant in time the investigation was done for surface piercing shore parallel breakwaters in a non tidal environment the morphological simulation results for the planform shape agree qualitatively with field observations and predictions from empirical rules using the simulation results simple design curves for surface piercing breakwaters are derived the importance of properly accounting for the influence of wave diffraction when modelling sediment transport and morphology in the vicinity of shore parallel structures is also investigated the present paper summarises much of the work performed at dhi water environment over the past 10 years within the field of coastal area morphological modelling

zircon u pb geochronology and geochemistry of low grade metamorphosed volcanic rocks from the dantazi complex implications for the evolution of the north china craton abstract the late neoarchean witnessed the cratonization of the north china craton ncc through amalgamation of several micro blocks to form a coherent basement the archean orthogneisses and supracrustal rocks in this craton have experienced various grades of metamorphism ranging up to upper amphibolite and granulite facies at 2500 ma recently a suite of low grade metamorphosed greenschist to lower amphibolite facies volcanic rocks was discovered in the late neoarchean dantazi complex in northern hebei province these meta volcanic rocks consist of bimodal basalt andesite and trachyte dacite with a sio2 gap between 54 4 wt and 60 7 wt here we report shrimp zircon u pb ages of 2490 19 ma mswd 2 0 and 2502 8 ma mswd 0 83 from the meta mafic and meta felsic volcanics respectively representing the timing of igneous activity all the meta mafic volcanic rocks display coherent trace element and ree patterns which are characterized by enriched lile and lree but depleted hfse and hree la yb n 6 29 15 10 combining these trace element features with the positive zircon ehf t values 1 3 to 6 6 we propose that the mafic rocks were likely derived from partial melting of a previously metasomatized lithospheric mantle in the primitive mantle normalized diagram the felsic rocks display uniform patterns enriched in lile but depleted in nb and ta similar to those of lower crust furthermore their strongly fractionated ree la yb n 15 24 61 20 lower hree concentrations yb 0 47 1 65 ppm and positive zircon ehf t values 1 6 to 5 3 suggest that they were derived from partial melting of the lower crust with garnet in the residue this coeval occurrence of metasomatized mantle derived mafic magmas and potassic felsic magmas from different source regions reflects an intracontinental extensional setting during the late neoarchean to earliest paleoproterozoic following the cratonization of the ncc our new data combined with previous published data allow us to speculate that the intracontinental extensional regime might have prevailed in the ncc from late neoarchean onwards

a re os study of molybdenites from the lanjiagou mo deposit of north china craton and its geological significance article i nfo the lanjiagou mo deposit is located in the eastern part of the north china craton rhenium and osmium isotopes in molybdenites from the lanjiagou porphyry mo deposit have been used to determine the timing of mineralization molybdenite was analyzed mainly from granite porphyry which is characterized by moderate to strong silicification rhenium concentrations in molybdenite samples are between 33 and 48 g g analysis of eleven molybdenite samples yields an isochron age of 181 6 6 5 ma 2 based on the geological history and spatio temporal distribution of the granitoids it is proposed that the mo deposits in the eastern part of the north china craton were related to the subduction of the paleo pacific plate during jurassic time 2009 published by elsevier b v on behalf of international association for gondwana research

late paleozoic volcanic record of the eastern junggar terrane xinjiang northwestern china major and trace element characteristics sr nd isotopic systematics and implications for tectonic evolution article i nfo the eastern junggar terrane of the central asian orogenic belt includes a late paleozoic assemblage of volcanic rocks of mixed oceanic and arc affinity located in a structurally complex belt between the siberian plate the kazakhstan block and the tianshan range the early history of these rocks is not well constrained but the junggar terrane was part of a cordilleran style accreted arc assemblage by the late carboniferous late paleozoic volcanic rocks of the northern part of the east junggar terrane are divided from base to top into the early devonian tuoranggekuduke formation fm middle devonian beitashan fm middle devonian yundukala fm late devonian jiangzierkuduke fm early carboniferous nanmingshui fm and late carboniferous batamayineishan fm we present major element trace element and sr nd isotopic analyses of 64 ultra mafic to intermediate volcanic rock samples of these formations all devonian volcanic rocks exhibit remarkably negative nb ta and ti anomalies on the primitive mantle normalized trace element diagrams and are enriched in more highly incompatible elements relative to moderately incompatible ones furthermore they have subchondritic nb ta ratios and their zr nb and sm nd ratios resemble those of morbs characteristics of arc related volcanic rocks the early devonian tuoranggekuduke fm middle devonian beitashan fm and middle devonian yundukala fm are characterized by tholeiitic and calc alkaline affinities in contrast the late devonian jiangzierkuduke fm contains a large amount of tuff and sandstone and its volcanic rocks have dominantly calc alkaline affinities we therefore propose that the jiangzierkuduke fm formed in a mature island arc setting and other devonian fms formed in an immature island arc setting the basalts from the nanmingshui fm have geochemical signatures between n morb and island arcs indicating that they formed in a back arc setting in contrast the volcanic rocks from the batamayineishan fm display geochemical characteristics of continental intraplate volcanic rocks formed in an extensional setting after collision thus we propose a model that involves a volcanic arc formed by northward subduction of the ancient junggar ocean and amalgamation of different terranes during the late paleozoic to interpret the formation of the late paleozoic volcanic rocks in the eastern junggar terrane and the altai and junggar terranes fully amalgamated into a cordilleran type orogen during the end of early carboniferous to the middle late carboniferous

geophysical and geological tests of tectonic models of the north china craton abstract the geometry and timing of amalgamation of the north china craton have been controversial with three main models offering significantly different interpretations of regional structure geochronology and geological relationships one model suggests that the eastern and western blocks of the ncc formed separately in the archean and an active margin was developed on the eastern block between 2 5 and 1 85 ga when the two blocks collided above an east dipping subduction zone a second presumes the eastern block rifted from an unknown larger continent at circa 2 7 ga and experienced a collision with an arc perhaps attached to the western block above a west dipping subduction zone at 2 5 ga and the 1 85 ga metamorphism is related to a collision along the northern margin of the craton when the ncc joined the columbia supercontinent a third model suggests two collisions in the central orogenic belt at 2 1 and 1 88 ga but recognizes an early undated deformation event recent seismic results reveal details of the deep crustal and lithospheric structure that support both the second and third models showing that subduction beneath the central orogenic belt was west directed and that there is a second west dipping paleosubduction zone located to the east of the cob dipping beneath the western block ordos craton the boundaries identified through geophysics do not correlate with the boundaries of the trans north china orogen suggested in the first model and the subduction polarity is opposite that predicted by that model high pressure granulite facies metamorphism at 1 85 ga is not restricted to the tnco as suggested by the first model but is documented across the ncc as predicted by the second model suggesting a major continent continent collision along the north margin of the craton at 1 85 ga further it has recently been shown that in the southern tnco there is no record of metamorphism at circa 1 85 ga but only at 2 7 2 5 ga showing that the tnco as defined as a circa 1 85 ga orogen does not exist this is further confirmed by recent re os isotopic studies which show that the subcontinental lithospheric mantle beneath the southern cob is late archean in age and that a province in the northern ncc is circa 1 8 ga correlating with the proposed collision belt of the ncc with the columbia supercontinent across the entire ncc the cob is an archean convergent belt re worked in the paleoproterozoic and the paleoproterozoic tectonism is widespread across the ncc as predicted by the model whereby the previously amalgamated eastern and western blocks experienced a continental collision with columbia at circa 1 85 ga but uplift exhumation rates are slow necessitating a re evaluation of the tectonic models of the ncc

rock topography causes spatial variation in the wave current and beach response to sea breeze activity we hypothesized that beach profiles that are perched on natural rock structures would be better protected from waves and currents than profiles that are not fronted by rock in southwest western australia many beaches such as at yanchep are perched on quaternary limestone yanchep lagoon is fronted by a low crested limestone reef that partially encloses a coastal lagoon the spatial variation of waves and currents around the rock structures were quantified during the sea breeze cycle at locations 1 offshore 2 20 m seaward of the reef 3 inside the lagoon and 4 in the surf zone the spatial variation in the beach profile response was measured at two beach profiles 1 the exposed profile that was not fronted directly seaward by outcropping limestone and 2 the sheltered profile which was fronted seaward by submerged limestone at 2 m water depth and that was near the lagoon exit at the end of the limestone reef the sheltered profile had greater volume changes during the cycle of the sea breeze whilst the exposed profile recovered more by overnight accretion when wind decreased the lagoonal current drove the strong response of the sheltered profile and may have contributed to the lack of overnight recovery of the beach together with the seaward rock formation impeding onshore sediment transport the different direction and speed responses of bottom currents in the surf zone fronting the two profiles reflected the local variation in geology the influence of the jet exiting the lagoon and wave refraction around the reef that was measured with gps drifters and wave ray tracing using xbeach major spatial variation in waves currents and beachface behavior at this perched beach shows the importance of the local geological setting

wave overtopping and induced currents at emergent low crested structures abstract this paper deals with wave overtopping associated to low emergent detached breakwaters it starts presenting the various mechanisms which define the functional behaviour of detached breakwaters which are frequently overtopped the emphasis is on the role played by overtopping and how this contributes to the wave pumping in the area around the structure the paper then reviews the available formulations for predicting overtopping considering the sensitivity of various equations to climatic drivers and their suitability for low crested coastal structures the paper then analyzes nearshore circulation models and how overtopping discharges can be included this is illustrated with a sample q 3d model by analyzing the differences obtained with without overtopping the emphasis is on the implications for the functional design of the structure and its morpho hydrodynamic impact the main conclusion is the sensitivity of the functional design of such structures to the underlying hydrodynamics processes and the importance to explicitly include overtopping for numerical simulations of the morpho hydrodynamic behaviour of low crested breakwaters

experimental and numerical investigation of bed morphology in the lee of porous submerged breakwaters abstract in the present work the evolution of a sandy beach in the lee of a permeable submerged breakwater was studied both experimentally and numerically three dimensional laboratory experiments were performed to investigate regular and irregular wave propagation over a porous submerged structure and the resulting bed morphology evolution down wave of it the tests included normal wave incidence of breaking and non breaking long and shorter waves the measurements were also used to validate a compound numerical model the basic solver relies on enhanced boussinesq type equations extended to simulate wave propagation over porous beds the wave module accounts for the entire nearshore zone from deep water to the swash zone and it is coupled with a sediment transport module including both bed and suspended loads adequate agreement between measurements and model results was achieved in most cases

modelling the effect of wave overtopping on nearshore hydrodynamics and morphodynamics around shore parallel breakwaters wave overtopping nearshore coastal structures such as shore parallel breakwaters can significantly alter the current circulation and sediment transport patterns around the structures which in turn affects the formation of tombolos and salients in the nearshore area this paper describes the implementation of a wave overtopping module into an existing depth averaged coastal morphological mode coast2d and model applications to investigate the effect of wave overtopping on the hydrodynamics and morphodynamics around a group of shore parallel breakwaters the hydrodynamic aspects of the model were validated against a series of laboratory conditions the model was then applied to a study site at sea palling norfolk uk where 9 shore parallel segmented breakwaters including 4 surface piercing and 5 low crested breakwaters are present for the storm conditions in nov 2006 the model results were compared with laboratory data and field measurements showing a good agreement on both hydrodynamics and morphological changes further analysis of wave overtopping effect on the nearshore hydrodynamics and morphodynamics reveals that wave overtopping has significant impacts on the nearshore circulation sediment transport and the resulting morphological changes within such a complex breakwater scheme under the storm and macro tide conditions the results indicate the importance of including the wave overtopping in modelling nearshore morphodynamics with the presence of coastal structures

wave height setup and currents around a detached breakwater submitted to regular or random wave forcing wave height set up and currents were measured in the laboratory around a detached breakwater erected on a 1 in 50 plane beach and subjected to regular unidirectional waves random unidirectional waves and directional random waves a comparison is made between regular and random wave cases which had equal incident wave energy while few differences are noticed between unidirectional and directional random waves wave height setup and current variations are smoother for random waves than for regular waves for regular wave conditions the location and the extent of the eddy currents behind the breakwater are strongly constrained by the breaking line location a steep gradient of the current is observed across it the circulating flow observed in the lee of the breakwater surrounds a wide eddy centre with almost quiescent fluid this is interpreted as a result of the significant reduction of eddy diffusivity outside the surf zone for comparison with numerical modelling results an extensive investigation of one regular wave case was conducted including determination of the vertical structure of the currents it is shown that currents inshore from the breakwater display limited variations over depth

airborne lidar application to karstic areas the example of trieste province north eastern italy from prehistoric sites to roman forts abstract the trieste karst at the northernmost shore of the adriatic sea is rich in prehistoric caves and protohistoric hill forts most of these archaeological sites were already identified in the second half of the 19th century when large parts of the area were almost without vegetation coverage for the effect of sheep breeding and exploitation of wood resources only a few open air archaeological sites have been discovered in recent years due to the lack of systematic archaeological surveys and reforestation airborne lidar light detection and ranging data originally acquired for environmental monitoring over the friuli venezia giulia region north eastern italy have been recently analysed by means of free open source softwares for archaeological prospection of the trieste karst area the lidar derived images have allowed identifying numerous unknown fortified structures ranging from prehistory to roman time within a complex archaeological landscape that includes possible funerary barrows agricultural terraces and other structures the discovery of a probable roman republican fort is particularly significant since similar structures almost unknown in italy find comparison only with later examples of military forts from roman provinces the discovery of prehistoric protohistoric and roman fortified sites reported in this paper shows that airborne lidar remote sensing represents a revolution in landscape archaeology and archaeological mapping of karstic areas this technique can provide unexpected results even in relatively urbanized territories investigated for a long time

the anthropic landscape imprint around one of the largest roman hydraulic gold mines in europe sierra del teleno nw spain abstract this study explores the information gathered from the landscape transformation that occurred during the intense period of roman hydraulic gold mining activity in northwest spain the sierra del teleno and its surroundings are characterised by the presence of quaternary glacial and periglacial deposits and locally neogene alluvial sediments which were intensely mined by the romans however the mining debris often obscures natural deposits making their identification and description a challenging task the aim of this study is to determine the existence of specific geomorphological features that can improve the identification of anthropic elements related to mining activity river captures and widened drainage systems are among the most outstanding structures remaining due to the extent and complexity of the work involved however other mining elements such as anthropic modification of alluvial fans moraine deposits and rock ridges are also evident in the landscape in many cases these remains are linked to the hydrologic infrastructure found in the area which mainly comprises an extensive system of natural and man made channels and distribution water tanks difficulties arise in areas where no such structures are found thus the use of geomorphic elements and patterns can help to distinguish natural and anthropic landforms using this approach therefore we have performed the first systematic and detailed analysis of the morphological imprint of roman hydraulic gold mining activity on the landscape these data will help piece together the puzzle of how the landscape was transformed by roman mining activity and can contribute to discussions surrounding the new epoch the anthropocene