genetic classification of polish lignite deposits a review abstract poland is one of the largest lignite producers not only in the european union but also in the world the majority of lignite deposits that have economic value are of early and middle miocene age however the early oligocene lignite seam and the so called accompanying lignite seams of middle miocene age may also occasionally be important for the mining industry therefore five main and two accompanying lignite seams are described among the oligocene miocene sediments in central western poland these seams are present in sixty nine deposits which are taken into consideration in this contribution polish lignite deposits can be classified genetically thus they are divided into four main types epeirogenic tectonic karstic and glaciotectonic which contain seven subtypes sheet lenticular grabens salt karst carbonate karst fold thrust sliced of lignite deposits the vast majority of lignite resources represent the tectonic and or epeirogenic type of deposits almost 100 of lignite production in poland that is about 63 66 mt per year is exploited from them on the other hand the most deformed syn and or post depositionally are two deposits the rogo no and sieniawa ones which belong to the salt karst type salt karst subtype and the glaciotectonic type fold and thrust sliced subtypes of lignite deposits respectively finally knowledge about the genesis of lignite deposits can be useful during their exploration and exploitation this allows for proper planning of geological prospecting of the deposits and the use of a better method of lignite mining

relationship between magnetic fabrics and shear directions in melange within the miyama formation shimanto accretionary complex japan article i nfo the magnetic fabrics of tectonic melange in the miyama formation shimanto accretionary complex of kii peninsula japan are examined using anisotropy of magnetic susceptibility ams data and they are com pared with shear directions estimated by traditional measurements of p y intersections in the melange in most cases ams data are consistent with the estimated shear directions and they can be divided into two types one with kmax the maximum magnetic susceptibility axes oriented parallel to the shear direction on the shear planes and another with kmax axes oriented parallel to the p y intersections in both types the kmin the minimum magnetic susceptibility axes are oriented perpendicular to the melange foliation however some sites exhibit unexpected kmax axes orientations trending perpendicular to the melange foli ation analyses of texture and magnetic properties indicate that such unexpected orientations are caused by a predominance of single magnetic domains of magnetite and or the existence of ankerite and siderite veins in which the long axes of crystals are oriented perpendicular to the foliation in the melange as a consequence the restored shear direction deduced from ams data improved the credibility of the kinematics of ancient plate motions although ams data provide useful information on shear directions in melanges it is essential to examine the magnetic carriers and their magnetic domain structures for accuracy of the analyses

short and medium term coastal evolution of necochea municipality buenos aires province argentina the short and medium term coastal evolution of necochea municipality buenos aires province argentina was studied the medium term evolution study was based on aerial photographs from 1967 and 1984 and satellite images from 2004 using the dune or cliff toe as coastline indicator the short term evolution was studied from february 2006 to december 2009 by means of seasonal beach profiles and sediment sampling results showed that in the medium term at necochea the coastline has remained stable or has advanced whereas in the short term the analysis has evidenced incipient erosion processes on the other hand at quequen the retreat of the coastline and the negative sedimentary balances medium and short term are clearly indicating an accentuated erosion process the different degrees of coastal erosion are related in part to beach vulnerability to wave storms but mainly to anthropogenic actions which have affected the beach sediment supply these results evidence the necessity to develop a coastal management programme

aeolian sediment transport on a beach surface moisture wind fetch and mean transport abstract temporal and spatial changes in wind speed wind direction and moisture content are ubiquitous across sandy coastal beaches often these factors interact in unknown ways to create complexity that confounds our ability to model sediment transport at any point across the beach as well as our capacity to predict sediment delivery into the adjacent foredunes this study was designed to measure wind flow and sediment transport over a beach and foredune at greenwich dunes prince edward island national park with the express purpose of addressing these complex interactions detailed measurements are reported for one stormy day october 11 2004 during which meteorological conditions were highly variable wind speed ranged from 4 ms 1 to over 20 ms 1 wind direction was highly oblique varying between 60 and 85 from shore perpendicular and moisture content of the sand surface ranged from a minimum of about 3 by mass to complete saturation depending on precipitation tidal excursion and storm surge that progressively inundated the beach the data indicate that short term variations i e minutes to hours in sediment transport across this beach arise predominantly because of short term changes in wind speed as is expected but also because of variations in wind direction precipitation intensity and tide level even slight increases in wind speed are capable of driving more intense saltation events but this relationship is mediated by other factors on this characteristically narrow beach as the angle of wind approach becomes more oblique the fetch distance increases and allows greater opportunity for the saltation system to evolve toward an equilibrium transport state before reaching the foredunes whether the theoretically predicted maximum rate of transport is ever achieved depends on the character of the sand surface e g grain size slope roughness vegetation moisture content and on various attributes of the wind field e g average wind speed unsteadiness approach angle flow compression boundary layer development moisture content is widely acknowledged as an important factor in controlling release of sediment from the beach surface all other things being equal the rate of sediment transport over a wet surface is lesser than over a dry surface on this beach the moisture effect has two important influences a in a temporal sense the rate of sediment transport typically decreases in association with rainfall and increases when surface drying takes place and b in a spatio temporal sense shoreline excursions associated with nearshore processes such as wave run up storm surge and tidal excursions have the effect of constraining the fetch geometry of the beach i e narrowing the width of the beach because saturated sand surfaces such as found in the swash zone will only reluctantly yield sediments to aeolian entrainment the available beach surface across which aeolian transport can occur becomes narrower as the sea progressively inundates the beach under these constrained conditions the transport system begins to shut down unless wind angle becomes highly oblique thereby increasing fetch distance in this study maximum sediment transport was usually measured on the mid beach rather than the upper beach i e closer to the foredunes this unusual finding is likely because of internal boundary layer development across the beach which yields a decrease in near surface wind speed and hence transport capacity in the landward direction although widely recognized in the fluid mechanics literature this decrease in near surface shear stress as a by product of a developing boundary layer in the downwind direction has not been adequately investigated in the context of coastal aeolian geomorphology

coastal foredune topography as a control on secondary airflow regimes under offshore winds aeolian sediment transport under offshore winds is usually discounted from sediment budget considerations of coastal dunes results presented here indicate however that depending on wind orientation and foredune morphology positive contributions to the sediment budget can arise from offshore winds lee side airflow patterns seaward of the foredune crest under offshore winds were studied at three sites of varying foredune geometry along magilligan strand northern ireland ultrasonic anemometers recorded 1 hz wind velocity data at 1 intervals descriptive statistics and wind rose diagrams were used in the analysis of these data under perpendicularly offshore winds each site exhibited a different type of lee side airflow pattern a tall 11 4 m sharp crested foredune produced flow separation with a recirculation cell a lower 6 6 m more rounded foredune crest exhibited lee side flow that remained attached but was deflected parallel to the crest while flow over a low incipient foredune crest resulted in attached flow with no deflection in the lee the morphology of the lee slopes best explained these airflow adjustments more obliquely offshore winds were also found to affect the secondary airflow patterns with a smooth transition from flow separation to flow attachment as the incident angle decreased at higher wind velocities this smooth transition was replaced with a more abrupt switch between the secondary airflow types this threshold was located at similar approach angles to those recorded for desert dunes 90 20 these findings have significant implications for the post storm recovery and long term evolution of beach dune systems where the predominant winds are offshore and offer an explanation for the presence of many beach dune systems in lee coast locations copyright 2010 john wiley sons ltd

kinematic analysis of melange fabrics examples and applications from the mchugh complex kenai peninsula alaska permian to cretaceous melange of the mchugh complex on the kenai peninsula south central alaska includes blocks and belts of graywacke argillite limestone chert basalt gabbro and ultramafic rocks intruded by a variety of igneous rocks an oceanic plate stratigraphy is repeated hundreds of times across the map area but most structures at the outcrop scale extend lithological layering strong rheological units occur as blocks within a matrix that flowed around the competent blocks during deformation forming broken formation and melange deformation was noncoaxial and disruption of primary layering was a consequence of general strain driven by plate convergence in a relatively narrow zone between the overriding accretionary wedge and the downgoing generally thinly sedimented oceanic plate soft sediment deformation processes do not appear to have played a major role in the formation of the melange a model for deformation at the toe of the wedge is proposed in which layers oriented at low angles to s1 are contracted in both the brittle and ductile regimes layers at 30 458 to s1 are extended in the brittle regime and contracted in the ductile regime and layers at angles greater than 458 to s1 are extended in both the brittle and ductile regimes imbrication in thrust duplexes occurs at deeper levels within the wedge many structures within melange of the mchugh complex are asymmetric and record kinematic information consistent with the inferred structural setting in an accretionary wedge a displacement field for the mchugh complex on the lower kenai peninsula includes three belts an inboard belt of late triassic rocks records west to east directed slip of hanging walls a central belt of predominantly early jurassic rocks records north south directed displacements and early cretaceous rocks in an outboard belt preserve southwest northeast directed slip vectors although precise ages of accretion are unknown slip directions are compatible with inferred plate motions during the general time frame of accretion of the mchugh complex the slip vectors are interpreted to preserve the convergence directions between the overriding and underriding plates which became more oblique with time they are not considered indicative of strain partitioning into belts of orogen parallel and orogen perpendicular displacements because the kinematic data are derived from the earliest preserved structures whereas fabrics related to strain partitioning would be expected to be superimposed on earlier accretion related fabrics 1999 elsevier science ltd all rights reserved

alexandria nile delta coast egypt update and future projection of relative sea level rise previous studies have indicated that the nile river deltaic plain is vulnerable to a number of aspects including beach erosion inundation and relatively high rates of land subsidence this issue motivates an update and analysis of new tide gauge records from which relative sea level changes can be obtained estimated rates from five tide gauges are variable in terms of magnitude and temporal trend of rising sea level analysis of historical records obtained from tide gauges at alexandria rosetta burullus damietta and port said show a continuous rise in mean sea level fluctuating between 1 8 and 4 9 mm year the smaller rate occurs at the alexandria harbor while the higher one at the rosetta promontory these uneven spatial and temporal trends of the estimated relative sea level rise rslr are interpreted with reference to local geological factors in particular holocene sediment thickness subsidence rate and tectonism are correlated with the estimated rates of relative sea level change from the relatively weak correlation between them we presume that tectonic setting and earthquakes both recent and historical ones contribute more to accelerated rslr than that of dewatering and compression dewatering of holocene mud underlying the nile delta plain as a result large areas of the coastal plain have been subsided but some sectors have been uplifted in response to tectonic activities of thick underlying older strata projection of averaged sea level rise trend reveals that not all the coastal plain of the nile delta and alexandria is vulnerable to accelerated sea level rise at the same level due to wide variability of the land topography that includes low lying areas high elevated coastal ridges and sand dunes accretionary beaches and artificially protective structures interaction of all aspects tectonic regime topography geomorphology erosion rate and rslr rate permitted to define risk areas much vulnerable to impacts of sea incursion due to accelerated sea level rise

late quaternary evolution of the feldbiss fault roer valley rift system the netherlands based on trenching and its potential relation to glacial unloading abstract the most important tectonic structure in the southern part of the netherlands is the roer valley rift system rvrs the main border fault zones of the rvrs the peel boundary and the feldbiss fault zones have been active during the quaternary and are still active today as indicated by the occurrence of earthquakes in this paper we present the results of a trench across the feldbiss fault part of the feldbiss fault zone this trench provided no evidence for earthquakes along this segment of the fault zone fluidization structures were not encountered a sudden increase in the average fault displacement rate was inferred for the period around 15 ka b p in a trench nearby across the geleen fault of the same fault zone the limited age control cannot exclude that such an acceleration also occurred at the feldbiss fault during the second half of the 1990 s several paleoseismological trenching studies have been carried out in the rvrs the compilation of the results of these studies reveals that the main border faults possibly experienced an increase in fault activity around 10 15 ka b p the timing of this increased activity and results from glacial rebound modelling indicate that glacial unloading of the crust can have triggered this increase in fault activity

influence of vegetation on aeolian sand transport rate from a backshore to a foredune at hasaki japan the influence of vegetation on aeolian sediment transport rate in the region from a backshore to a foredune was investigated at the hasaki coast in japan where an onshore wind was predominant and the creeping beach grasses carex kobomugi and calystegia soldanella were major species the comparison of cross shore distributions of the cross shore component of aeolian sand transport rate with and without vegetation which were estimated on the basis of the beach profile changes and a mass conservation equation showed that the creeping grasses influenced the aeolian sand transport rate the landward aeolian sand transport rate rapidly decreased landward from the seaward limit of vegetation when the grasses grew the aeolian sand transport rate reduced by 95 with a vegetation cover of 28 on the other hand when the grasses were absent the landward aeolian sand transport rate did not decrease near the seaward vegetation limit but near the foot of the foredune

activity along the osning thrust in central europe during the lateglacial ice sheet and lithosphere interactions abstract the osning thrust is one of the major fault systems in central europe with a length of approximately 115 km it underwent a polyphase tectonic evolution in the mesozoic that ranged from extensional movements in the jurassic to reverse faulting and thrusting during inversion in the late cretaceous a series of complex metre scale faults and related fold structures are developed within the upper pleistocene alluvial aeolian complex of the upper senne 1 km away from the thrust the faults dip towards the north and show offsets in a range of several decimetres growth strata indicate a two fold evolution of the structures the faults began as normal faults and were later transformed into reverse faults which resulted in the formation of small scale inversion structures with a typical harpoon shape glaciotectonics can be ruled out as the driving mechanism for these structures because new optically stimulated luminescence osl ages imply that the sedimentary succession was deposited during the late pleistocene between 29 3 2 9 ka and 13 1 1 5 ka at which time the ice margin was much further to the northeast we believe the inversion structures were caused by movement on the osning thrust due to generation of a forebulge of the late pleistocene weichselian ice sheet this led to normal faulting as a consequence of extension in the forebulge area during glaciation the osl ages for the normal fault related growth strata are in a range of 16 13 ka later reverse movements occurred during deglaciation due to the n s directed compressional stress field in northern germany numerical simulations of the deglaciation seismicity point to seismic events with a thrust mechanism in the study area between 15 5 and 12 3 ka bp although normal faulting is also possible in this time period numerous soft sediment deformation structures imply that movement on the osning thrust caused earthquakes with a significant magnitude in the autumn of 1612 an earthquake took place in this area it is very likely that this event is related to background seismicity on this fault although movement due to the influence of the ongoing glacial rebound in fennoscandia is also possible

styles of positive inversion tectonics in the central apennines and in the adriatic foreland implications for the evolution of the apennine chain italy abstract integration of new field structural and geophysical data with existing information from the apennines chain in italy and its adjacent adriatic foreland indicates that the styles of positive inversion tectonics and the modes of interaction between the extensional and the subsequent compressive structures vary starting from the cretaceous the contractional deformation induced by the mainly north directed convergence of africa adria with respect to the european plate promoted the closure of various arms of the atlantic and the neo tethys oceans which opened in different times and with distinct orientations the mosaic of continental blocks carbonate platforms rift basins and oceanic domains with several geometries and orientations with respect to the axis of the subsequent compression and the resulting heterogeneities within the shallow sedimentary cover and the overall lithosphere strongly influenced both the structural evolution of the apennine orogenic belt and the intra continental deformation within the adriatic foreland field observations reveal that the steeply e and w dipping mesozoic cenozoic normal faults are systematically decapitated by sub horizontal or gently west dipping thrusts propagating with short cut trajectories pre thrusting normal faults were commonly deformed by later thrusts but little evidence seems to support their entire reactivation as high angle reverse faults this suggests that these shallow and steeply dipping discontinuities were not suitable to be reutilized by the superficial thin skinned thrust faults propagating within the sedimentary cover in contrast presumably late paleozoic and mesozoic w dipping normal faults appear moderately reactivated in the adriatic foreland and strong positive inversion tectonics affect the deeper and buried structural levels of the apennine chain within the latter the syn rift sediments in the hangingwall blocks of the fault bounded basins were totally extruded and generated the strong uplift of the thinned adria continental crust finally the contrasting styles of interactions of the pre existing normal faults with later thrusts i e passive truncation or positive reactivation strictly result from the different evolution of the apennine chain and the combined thin and thick skinned modes of deformation of the stretched lithosphere of the adria plate

reactivation tendency analysis a theory for predicting the temporal evolution of preexisting weakness under uniform stress state abstract understanding the mechanical controls on reactivation of preexisting weakness is a fundamental problem in tectonic studies in this study we develop a theoretical framework for evaluating the likelihood of seismicity on active faults and the sequence of reactivation of multiple sets of preexisting weakness our analysis overcomes the restrictions of the early work that assumes uniform coefficient of friction across all preexisting planes with negligible cohesive strength and vertical or horizontal orientations of principal stresses using a coordinate system transformation we developed a new graphical technique that can express the reactivation problem in the mohr space with the principal stresses oriented neither vertically nor horizontally we verified the predicted sequence of reactivation on preexisting weakness and initiation of new fractures according to the byerlee law and the coulomb fracture criterion by conducting a simple sandbox experiment our proposed reactivation tendency analysis can be expanded to evaluate the likelihood of seismicity on a single fault with curvi planar geometry e g listric normal faults ramp flat thrusts and strike slip faults with restraining and releasing bend geometry our analysis also provides a new insight into the mechanical cause of temporal evolution of pre existing weakness in geologic records finally our work implies that the sequence of faulting reactivated from preexisting weakness provides critical information on the mechanical properties of the deforming lithosphere

transfer zones and fault reactivation in inverted rift basins insights from physical modelling abstract lateral transfer zones of deformation and fault reactivation were investigated in multilayered silicone sand models during extension and subsequent co axial shortening model materials were selected to meet similarity criteria and to be distinguished on ct scans this approach permitted non destructive visualisation of the progressive evolution of structures transfer zones were initiated by an orthogonal offset in the geometry of a basal mobile aluminium sheet and or by variations of layer thickness or material rheology in basal layers transfer zones affected rift propagation and fault kinematics in models propagation and overlapping rift culminations occurred in transfer zones during extension during shortening deviation in the orientation of frontal thrusts and fold axes occurred within transfer zones in brittle and ductile layers respectively ct scans showed that steep 58 67 rift margin normal faults were reactivated as reverse faults the reactivated faults rotated to shallower dips 19 38 with continuing shortening after 100 inversion rotation of rift phase faults appears to be due to deep level folding and uplift during the inversion phase new thrust faults with shallow dips 20 34 formed outside the inverted graben at late stages of shortening frontal ramps propagated laterally past the transfer structure during shortening during inversion the layers filling the rift structures underwent lateral compression at the depth the graben fill was pushed up and outwards creating local extension near the surface sand marker layers in inverted graben have showed fold like structures or rotation and tilting in the rifts and on the rift margins the results of our experiments conform well to natural examples of inverted graben inverted rift basins are structurally complex and often difficult to interpret in seismic data the models may help to unravel the structure and evolution of these systems leading to improved hydrocarbon exploration assessments model results may also be used to help predict the location of basement discontinuities which may have focused hydrothermal fluids during basin formation and inversion

on the reactivation of extensional fault systems in terranes that have undergone substantial extension three sets of faults dominate a shallow to steep dipping commonly rotational normal faults b a really extensive shallow dipping normal detachment faults and c steep dipping transfer faults that strike at high angles to the normal faults these fault systems may extend through a large fraction of the crust reactivation of these fault systems will depend primarily on the relative strengths of the faults shear zones and their host rock and their orientation in the prevailing stress field it is concluded that reactivation is generally mechanically favoured but that it will probably only take place when the fault shear zones are in near ideal orientations consideration of the tectonic setting of extended terranes and of the limited number of well described examples suggests that reverse thrust reactivation of the normal and detachment faults and wrench reactivation of transfer faults are the most likely styles examples of these styles are described from the bass strait basins of southeastern australia because extended terranes commonly underlie sedimentary basins for example on passive continental margins reactivation of extensional faults may be a key control on the tectonic evolution of such basins i e basin inversion

aeolian sand strip mobility and protodune development on a drying beach examining surface moisture and surface roughness patterns measured by terrestrial laser scanning ephemeral aeolian sand strips are commonplace on beaches their formation during high energy sand transport events often precedes the development of protodunes and their dynamics present interesting feedback mechanisms with surface moisture patterns however due to their temporary nature little is known of their formation mobility or the specifics of their interaction with beach surface characteristics similarly surface moisture has an important influence on sediment availability and transport in aeolian beach systems yet it is difficult to quantify accurately due to its inherent variability over both short spatial and temporal scales whilst soil moisture probes and remote sensing imagery techniques can quantify large changes well their resolution over mainly dry sand close to the aeolian transport threshold is not ideal particularly where moisture gradients close to the surface are large in this study we employed a terrestrial laser scanner to monitor beach surface moisture variability during a three and a half hour period after a rain event and investigated relationships between bedform development surface roughness and surface moisture our results demonstrate that as the beach surface dries sand transport increases with sediment erosion occurring at the wet dry surface boundary and deposition further downwind this dynamic structure dependent upon changing surface moisture characteristics results in the formation of a rippled sand strip and ultimately a protodune our findings highlight dynamic mobility relationships and confirm the need to consider transient bedforms and surface moisture across a variety of scales when measuring aeolian transport in beach settings the terrestrial laser scanner provides a suitable apparatus with which to accomplish this

sedimentary and structural evolution of a pleistocene small scale push moraine in eastern poland new insight into paleoenvironmental conditions at the margin of an advancing ice lobe abstract recent studies of push moraines have focused on the interplay between the dynamics of ice margins and the environmental variables of the foreland into which they advance these studies showed that the spatial distribution geometry and style of the glaciotectonic deformation of push moraines are controlled by ice induced stresses the strain rate the rheology of the deposits and hydraulic conductivity in this work we provide new insight into this interplay at a small spatio temporal scale specifically the ancient glacial system of the liwiec ice lobe within the younger saalian ice sheet in eastern poland the paleoenvironmental variables that are analysed here refer to the dynamics of the hydrological processes that affected the patterns and sediment deposition rate on the terminoglacial fan and the resulting mechanical stratigraphy and hydraulic conductivity of the foreland we document the progradational sequence of the fan deposits that developed as a result of the ice lobe thickening and the steepening of its stationary front the sedimentary features of the fan the lithology of its basement and the hydraulic conductivity of the foreland strongly influenced the geometry and kinematics of fold growth during the advance of the ice lobe the predominance of flexural slip and the development of fractures including fold accommodation faults were interpreted to be an effect of buckle folding due to horizontal shortening induced by ice advance the partial overriding of the push moraine by the ice lobe and thus the submarginal conditions for deformation were inferred from the significant hinge migration and internal deformation of the strata under undrained conditions in one of the folds the synfolding deposition pattern of the fan growth strata allowed us to suggest that the push moraine was probably formed by a sustained advance rather than surge

active faults and paleoseismicity in fennoscandia especially sweden primary structures and secondary effects abstract fennoscandia today a region of low to moderately low seismicity was at the time of deglaciation with rates of uplift on the order of tens of centimetres per year a region of very high seismicity and active tectonics this is evident both from primary fault structures and from secondary sedimentary and hard rock effects in the region around the epicentral areas the map of active faults in fennoscandia includes numerous structures previously not recognised despite this the recording of active faults and paleoseismic events is still in its initial phase much more data will surely accumulate in the near future

effects of time dependent moisture content of surface sediments on aeolian transport rates across a beach wildwood new jersey u s a a one day field investigation on an unvegetated backbeach documents the importance of surface sediment drying to aeolian transport surface sediments were well sorted fine sand moisture content of samples taken in the moist areas on the backbeach varied from 2 9 to 9 2 per cent lack of dry sediment inhibited transport prior to 08 50 by 09 10 conspicuous streamers of dry sand moved across the moist surface barchan shaped bedforms 30 to 40 mm high and composed of dry sand moisture content 0 10 per cent formed where sand streamers converged the surface composed of dry sand increased from 5 per cent of the area of the backbeach at 09 50 to 90 per cent by 12 50 mean wind speeds were beetween 5 6 and 8 6 m s 1 at 6 m above the backbeach corresponding shear velocities were always above the entrainment threshold for dry sand and below the threshold for the moist sand on the backbeach measured rates of sand trapped by vertical cylindrical traps increased during the day relative to calculated rates the measured rate of sand trapped on the moist foreshore was higher than the rate trapped on the backbeach during the same interval indicating that the moist foreshore moisture content 18 per cent was an efficient transport surface for sediment delivered from the dry portion of the beach upwind measured rates of sand trapped show no clear relationship to shear velocities unless time dependent surface moisture content is considered results document conditions that describe transport across moist surfaces in terms of four stages including 1 entrainment of moist sediment from a moist surface 2 in situ drying of surface grains from a moist surface followed by transport across the surface 3 entrainment and transport of dry sediment from bedforms that have accumulated on the moist surface and 4 entrainment of sand from a dry upwind source and transport across a moist downwind surface 1997 john wiley sons ltd

sandbox experiments of inverted listric and planar fault systems abstract the kinematic and geometric evolution of basement controlled inversion structures has been analyzed using a plane strain sandbox apparatus the results of two representative scaled analogue models comprising rigid listric and planar detachment faults that both have cut off angles of 60 to the horizontal are described in detail the hangingwall above these detachment geometries was constructed from alternate layers of sand and mica in order to simulate an anisotropic sedimentary sequence in both experiments initial shortening at the onset of inversion was accommodated by bulk strain this was followed by reactivation of the basal detachment together with the main basin controlling planar and listric faults which propagate upwards through the post rift sequence at approximately the same angle as the upper part of the detachment fault i e 60 reactivation of relatively steep intra basinal extensional faults within the cover was restricted to nucleation of reserve faults and thrusts in the region of the tips during approximately the first 10 to 15 contraction this resulted in gently dipping thrusts that propagated upwards through the post rift sequence to produce harpoon shaped structures later in the inversion phase after approximately 15 contraction backthrusts cut through and displaced the original antithetic extensional graben faults producing downward tapering wedge shaped structures at the margins of the basin although deformation in these experiments was limited to purely dip slip displacement the nature of the original extensional faults and their reactivated tip regions resulted in cross sectional geometries that have a marked resemblance to strike slip induced flower structures uplift was asymmetric and centred above the upper part of the main detachment above the listric fault but was more symmetrical and centred above the soling out point of the detachment in the case of the planar fault geometry the results of these experiments show distinct similarities to structures seen on seismic sections form the southern north sea and other inverted sedimentary basins

temporal and spatial variabilities in the surface moisture content of a fine grained beach abstract this study examined spatial and temporal variations in the surface moisture content of a fine grained beach at padre island texas usa surface moisture measurements were collected on a 27 24 m grid that extended from the dune toe to the upper foreshore the grid was surveyed at 2 to 4 h intervals for two tidal cycles generating 17 maps of the spatial distribution of surface moisture simultaneous measurements of air temperature and humidity wind speed and direction tidal elevation and water table elevation were used to interpret observed changes in surface moisture it was found that the spatial distribution of surface moisture was broadly characterized by a cross shore gradient of high to low content moving landward from the swash zone the distribution of surface moisture was conceptualized in terms of three zones saturated 25 intermediate or transitional 5 25 and dry

seismic activity inferred crustal stresses and seismotectonics in the rana region northern norway abstract the seismotectonic significance of the rana region is known both from the fact that this was the location of the largest known earthquake in fennoscandia in recent times the m s 5 8 6 2 earthquake of august 31 1819 and from its relatively high constant seismic activity also in the 20th century in order to study this region in more detail a local seismic network has been in operation there since july 1997 as part of the neonor neotectonics in norway project the network was primarily designed to detect possible activity on the basmoen fault which runs 50 km subparallel to the rana fjord and which shows signs of likely post glacial activity the results have revealed a quite complex spatio temporal distribution of seismic activity and has also shown no activity on the basmoen fault itself during the first 18 months of operation july 1997 january 1999 the network has detected 373 locatable seismic events of which 267 were local earthquakes most of these earthquakes occurred in five groups in the western parts of the network all five groups had similar nnw esw trends in epicenter locations and all have shallow foci 2 12 km similar to what has also been found earlier for other concentrated earthquake zones in northern norway and the magnitude range is between m l 0 1 and 2 8 earthquake focal mechanism solutions within the network reveal a predominance for normal faulting with the tensional stress axis perpendicular do the coastline implying an unusual coast parallel orientation of the principal horizontal compressive stress the earthquakes occur in a region of maximum post glacial uplift gradients which supports deglaciation flexure as a viable explanation for these earthquakes a certain influence from more local factors however tied in general to crustal in homogeneities cannot be ruled out

seismic interpretation and structural restoration of the heligoland glaciotectonic thrust fault complex implications for multiple deformation during pre elsterian to warthian ice advances into the southern north sea basin abstract despite a long history of research the locations of former ice margins in the north sea basin are still uncertain in this study we present new palaeogeographic reconstructions of pre elsterian and warthian ice margins in the southeastern north sea basin which were previously unknown the reconstructions are based on the integration of palaeo ice flow data derived from glaciotectonic thrusts tunnel valleys and mega scale glacial lineations we focus on a huge glaciotectonic thrust complex located about 10 km north of heligoland and 50 km west of the north frisian coast of schleswig holstein northern germany multi channel high resolution 2d seismic reflection data show a thrust fault complex in the upper 300 ms twt ca 240 m of seismic data this thrust fault complex consists of mainly neogene delta sediments covers an area of 350 km2 and forms part of a large belt of glaciotectonic complexes that stretches from offshore denmark via northern germany to poland the deformation front of the heligoland glaciotectonic complex trends approximately nne ssw the total length of the glaciotectonic thrust complex is approximately 15 km the thrust faults share a common detachment surface located at a depth of 250 300 ms twt 200 240 m below sea level the detachment surface most probably formed at a pronounced rheological boundary between upper miocene fine grained pro delta deposits and coarser grained delta front deposits although we cannot rule out that deep permafrost in the glacier foreland played a role for the location of this detachment surface restored cross sections reveal the shortening of the complex along the detachment to have been on average 23 ranging from ca 16 50 the determined ice movement direction from east southeast to southeast suggests deformation by an ice advance from the baltic region the chronospatial relationship of the thrust fault complex and adjacent northwest southeast to northeast southwest trending elsterian tunnel valleys implies a pre elsterian mis 16 age of the glaciotectonic complex however the age of these elsterian tunnel valleys is poorly constrained and the glaciotectonic complex of heligoland may also have been formed during an early elsterian ice advance into the southeastern north sea basin the glaciotectonic complex underwent further shortening and the elsterian tunnel valley fills that were incised into the glaciotectonic complex were partly deformed during the saalian drenthe and warthe 1 ice advances

the dynamic effects of moisture on the entrainment and transport of sand by wind abstract there is an increasing awareness of the influence of surface moisture on aeolian entrainment and transport of sediment existing wind tunnel studies have shown the impact of a limited range of moisture contents on entrainment thresholds but similar investigations are lacking in the field the research reported here investigated the influence of changes in surface moisture content on sand entrainment and transport on a meso tidal beach in anglesey north wales high frequency 1 hz wind velocities measured with hot wire anemometers were combined with grain impact data from a sensit monitor and mass flux measurements from a standard sand trap surface and near surface moisture contents were assessed gravimetrically from surface sand scrapes and also directly by using a thetaprobe critical threshold values for entrainment were specified using a modified form of the time fraction equivalence method stout j e zobeck t m 1996a establishing the threshold condition for soil movement in wind eroding fields proceedings of the international conference on air pollution from agricultural operations mwps c 3 kansas city 7 9 february 1996 pp 65 71 results indicate a time dependent change in dominant control of the sand transport system from moisture to wind speed dependent upon the moisture content of the surface sediment this interchange between controlling parameters on both entrainment and transport was very sensitive to prevailing moisture conditions and took place over a period of minutes to hours under conditions experienced in the experiments presented here the critical moisture threshold for sediment entrainment was determined to be between 4 and 6 higher than the 1 4 specified in previous wind tunnel experiments furthermore a moisture content of nearly 2 where moisture was adhered to transported sediment appeared to have little or no impact on the rate of sand flux

constraints on aeolian sediment transport to foredunes within an undeveloped backshore enclave on a developed coast abstract landforms present in undeveloped beach enclaves located between properties developed with houses and infrastructure are often left to evolve naturally but are influenced by the human structures near them this field study evaluates how buildings and sand trapping fences change the direction of wind approach reduce wind speed and restrict fetch distances for sediment entrainment thereby reducing the potential for aeolian transport and development of dunes in enclaves field data were gathered in an 80 m long 44 m deep beach enclave on the ocean shoreline of new jersey usa comparison of wind characteristics in the enclave with a site unaffected by buildings revealed that offshore winds in the enclave are reduced in strength and altered in direction by landward houses increasing the relative importance of longshore winds vertical arrays of anemometers on the foredune crest foredune toe and berm crest in the enclave revealed increasing wind speed with distance offshore with strongest winds on the berm crest vertical cylindrical traps on the foredune crest foredune toe mid backshore berm crest and upper foreshore revealed the greatest rate of sediment transport on the berm crest sediment samples from the beach and from traps revealed limited potential for aeolian transport because of coarse grain sizes strong oblique onshore winds are common in this region and are normally important for transporting sand to dunes the length of an enclave and the setback distance on its landward side determine the degree to which sediment delivered by oblique winds contributes to dune growth the landward edge of the enclave defined by a sand fence near the dune toe is sheltered along its entire length from winds blowing at an angle to the shoreline of 25 or less a foredune set back this distance in an enclave the length of an individual lot about 20 m would be sheltered at an angle of 57 or less reducing the opportunity for dune building by onshore winds reduced potential for aeolian transport in enclaves implies that human actions may be required to build dunes artificially to protect buildings and roads from storm overwash

wind tunnel simulation of the three dimensional airflow patterns behind cuboid obstacles at different angles of wind incidence and their significance for the formation of sand shadows sand shadows commonly form downwind of obstacles in arid and semi arid regions understanding their dynamics requires insights into the airflow patterns behind the obstacles under different wind regimes here we studied models of cuboid obstacles to characterize the three dimensional responses of airflow behind obstacles with different shape ratios to variations in the incident flow in a wind tunnel simulation wind velocity was measured using particle image velocimetry piv the flow patterns behind cuboid obstacles were complicated by changes in the incidence angle of the approaching flow and in the obstacle s shape ratio the flows separated both horizontally and vertically creating reverse flow cells downwind of the obstacles the horizontal cells were characterized by two asymmetrical opposing reverse vortices at flow incidence angles greater than 60 to 65 whereas the vertical cells formed a single vortex at all angles the cells shifted position in response to changes in the incidence angle and shape ratio reflecting the interaction between outer and reverse flows the parameters of the horizontal and vertical reverse cells depended on the shape ratios and incidence angles but not on the wind velocity the sizes of the horizontal and vertical reverse cells were correlated reflecting their interactions the low velocity shadow behind the obstacle caused sand deposition and determined the sand shadow s evolution field experiments will be required to relate these airflow patterns to sand shadow development

analysis and reinterpretation of deformation features in the rouge river valley scarborough ontario geometry and timing of deformation affecting ordovician bedrock and overlying pleistocene sediments in the rouge river valley near scarborough ontario are analysed to evaluate whether or not the structures are a result of glacial action or neotectonic activity extensive data on local and regional ice flow directions are used to evaluate the kinematic compatibility between the observed faults and folds and the local ice flow directions jointing and multiple episodes of faulting affect both the ordovician bedrock and the overlying pleistocene sediments at one site the bedrock is displaced by a normal fault by a minimum of 1 2 m crosscutting relationships constrain the majority of the faulting in the rouge river valley as being coeval with deposition of the lower bowmanville till during the nissouri phase ca 23 15 ka and possibly younger at one locality the youngest regional ice flow direction is northwestward however local ice flow directions are highly variable this can be explained by local perturbation enhanced by the presence of drumlinoid features in the area most deformation features are compatible with local and regional ice flow directions glaciotectonic ice push and ice thrust deformation affected the thorncliffe formation after about 23 ka although some faults appear to be kinematically incompatible with ice flow directions six boreholes drilled to 52 m depth revealed only minor vertical offsets of bedrock strata in the uppermost 20 m and an absence of obvious fault offsets deeper precluding the possibility that the faults observed in the surface exposures were caused by deep seated neotectonic stresses

concentrated slip zones with subsidiary shears their development on three scales in the cerro brass fault zone appalachian valley and ridge concentrated slip zones bound subsidiary shears at three scales within the cerro brass fault which cuts cambrian dolomites of the n any anticlinorium pennsylvania on the outcrop scale thrust faults along both cerro brass fault zone boundaries acted as concentrated slip zones bounding subsidiary shears developed along original bedding planes the outcrop scale subsidiary shears are zones of concentrated slip bounding hand specimen scale subsidiary shears in turn the hand specimen scale subsidiary shears are concentrated slip zones bounding even smaller scale subsidiary shears subsidiary shears in cerro brass fault zone are analogous to subsidiary shears i e ri and r2 commonly found in laboratory gouge friction experiments the orientations of subsidiary shears at the outcrop and hand specimen scales define a riedel within riedel geometry in which the original bedding played the role of r shears at the outcrop scale and at the same time operated as boundary faults at a smaller scale the presence of subsidiary shears on more than one scale suggests that the coulomb failure theory is not sufficient to explain their origin

aeolian sediment transport on a human altered foredune changes in wind speed and sediment transport are evaluated at a gap and adjacent crest of a 2 to 3 m high 40 m wide foredune built by sand fences and vegetation plantings on a wide nourished fine sand beach at ocean city new jersey anemometer masts cylindrical sand traps and erosion pins were placed on the beach and dune during two obliquely onshore wind events in february and march 2003 results reveal that 1 changes in the alongshore continuity of the beach and dune system can act as boundaries to aeolian transport when winds blow at an angle to the shoreline 2 oblique winds blowing across poorly vegetated patches in the dune increase the potential for creating an irregular crest elevation 3 transport rates and deflation rates can be greater within the foredune than on the beach if the dune surface is poorly vegetated and the beach has not had time to dry following tidal inundation 4 frozen ground does not prevent surface deflation and 5 remnant sand fences and fresh storm wrack have great local but temporary effect on transport rates temporal and spatial differences due to sand fences and wrack changes in sediment availability due to time dependent differences in surface moisture and frozen ground combined with complex topography and patchy vegetation make it difficult to specify cause effect relationships effects of individual roughness elements on the beach and dune on wind flow and sediment transport can be quantified at specific locations at the event scale but extrapolation of each event to longer temporal and spatial scales remains qualitative copyright 2006 john wiley sons ltd

analogue modelling of fault reactivation tectonic inversion and oblique remobilisation of grabens abstract analogue models of sand above a silicone layer were examined to determine the effects of normal fault reactivation models were first subjected to extension which lead to the formation of two linear grabens each model was then subjected to a second phase deformation either parallel or oblique to the previous initial extension and either extensional or contractional the influence of sedimentation has been evaluated using experiments with and without sedimentation in cases of oblique secondary deformation all newly formed faults were parallel to the older grabens thus they were oblique to the direction of the principal stress directions during the second deformation phase in experiments without sedimentation all older faults were reactivated whereas in experiments with sedimentation some of the older faults were not reactivated in the case of an oblique compressional secondary deformation phase with post rift sedimentation strain partitioning occurred between reactivated older normal faults and new reverse faults 2 was vertical on reactivated normal fault planes whereas 3 was vertical on reverse fault planes in the case of oblique compressional secondary deformation phase without post rift sedimentation no strain partitioning was observed in this model 3 was vertical on every fault plane it is therefore concluded that sedimentation within grabens induces a variation of stress orientation and strain partitioning

aeolian dynamics of beach scraped ridge and dyke structures abstract where urban areas are situated close to a beach sand dunes act as protection from flooding and erosion when a dune has been removed or damaged by erosion dune ridge or dyke re building using heavy machinery a process known as beach scraping is a common method of restoration following construction natural accretion of sediment on the backshore is preferable as it facilitates sustained natural dune building growth of vegetation and habitat creation and reduces the need for further beach scraping this study investigates the near surface flow and transport potential for three artificial structure designs a single ridge a double ridge and a dyke the three shapes contained an identical volume of sand and were preceded by 50 m of beach at an angle of 3 a computational fluid dynamic model cfd was created for each scenario to calculate wind flow and shear velocity from 4 different wind directions at 22 5 intervals from 0 onshore to 67 5 from this data sediment flux was predicted along a two dimensional transect for each of the scenarios for all structures shear velocity on the beach and stoss slope decreased as incident wind direction became more oblique conversely shear velocity in the lee of the crest increased a reduction in shear velocity at the foot of each structure also occurred and appears related to stoss slope with the greatest reduction at the toe of the dyke structure stoss slope 34 and the least before the single ridge stoss slope 17 specifically the results suggest that the double ridge structure is the most resilient to aeolian erosion shear velocity reduction on the back beach is comparable to the dyke and sediment flux from the stoss slope of the double ridge structure may become trapped in the swale between the two ridges encouraging sediment deposition thus reducing sediment transport beyond the dunes and backshore although the dyke structure underwent the greatest reduction in shear velocity on the back beach it experienced substantial sediment flux at the crest and along the top of the structure making it susceptible to erosion during a strong wind event the highest sediment transport rate was calculated at the crest of the single ridge and the single ridge structure also created the smallest reduction of shear velocity on the back beach thus making it less desirable than the double ridge

geometry and kinematics of glaciotectonic deformation superimposed on the cenozoic fault tectonic framework in the central polish lowlands abstract the distribution of glaciotectonic structures can be controlled by the occurrence of tectonic or neotectonic faulting of the pre quaternary basement the faulted and thus undulated pre quaternary basement influenced the thinning or pinching out of weak deformable surficial sediments and could play a role of buried obstacles to forcing by ice sheets in both cases such faulting could result in a predisposition to the development of glaciotectonic deformations the present study has demonstrated how the geometry and kinematics of the glaciotectonic structures was controlled by the pre quaternary framework related to the kleczew graben tectonics the central polish lowlands the assumption has been made in this study that the tectonic fractures and faults could influence the reduction of strength and mechanical anisotropy within the pre quaternary sediments which were also remobilised by glaciotectonic forces the renewed stress build up by the glaciotectonic forces assumed herein could reactivate the pre existing fractures and faults at a lower stress level rather than produce new structures that require a higher stress level the results presented in this study are focused on detailed structural and kinematic analysis of the glaciotectonic faults and fractures for each glaciotectonic fault studied the slip vector was directly calculated based on the orientation of the fault striations and indirectly calculated from analysis of the small fractures that developed along the fault additionally the data from this analysis were integrated with the surface based 3d structural model obtained from the borehole data this approach revealed the relationships between the geometry orientation and kinematics of the glaciotectonic structures and the tectonic framework of the pre quaternary basement the different modes of glaciotectonic faulting were determined depending on the geometry and orientation of the pre existing reactivated faults and fractures with respect to the direction of the glaciotectonic contraction in addition to reverse dip slip displacements the strike slip and oblique slip displacements were recognised this study was performed in the kleczew graben the middle part of the polish lowlands in which the quaternary and the miocene sediments are affected by glaciotectonic deformations moreover the miocene sediments were also tectonically deformed in response to the development of the graben

positive fault inversion triggering intrusive diapirism an analogue modelling perspective understanding the formation and the development of salt structures is very important especially because they are of significant economical interest for hydrocarbon trapping and for long term storage of radioactive waste and energy reserves generally the activity of normal faults developed in extensional regimes is considered the most efficient mechanism for salt diapirs the results of analogue models reported in this paper suggest a new triggering mechanism for the rise of salt structures during basin inversion this mechanism relates the localization of ductile diapirs to early normal faults only after their inversion during later shortening in this case diapiric growth is related to the strong dip slip reactivation component along the fault extruding the silicone simulating salt upward some natural cases in which the timing and the mechanism of diapiric growth is not clear can be re interpreted in the light of these analogue model results

tectonic evolution of the fundy rift basin canada evidence of extension and shortening during passive margin development seismic and field data show that the fundy rift basin of southeastern canada experienced two distinct episodes of deformation during mesozoic time the first episode during middle triassic to early jurassic time was extensional rifting associated with nw se extension reactivated ne trending paleozoic compressional structures as normal faults forming the northwestern boundary faults of the fundy basin displacements on the low angle boundary faults locally exceeded 10 km rifting also reactivated east trending paleozoic compressional structures as oblique slip faults with normal and sinistral strike slip components forming the northern boundary faults of the fundy basin several kilometers of sediments and lava flows filled the basin during rifting the second deformational episode occurred during or after early jurassic time and probably before or during early cretaceous time inversion associated with nw se shortening occurred along all faulted margins of the fundy basin the northwestern boundary faults experienced several kilometers of reverse displacement broad anticlines developed within their hanging walls and the fundy basin acquired its synclinal form the northern boundary faults of the fundy basin became oblique slip faults with reverse and dextral strike slip components gentle synclines tight anticlines and faults with reverse separation deformed the synrift strata near the northern margin of the fundy basin neither collision nor subduction zones existed near the fundy basin during mesozoic time hence we believe that tectonic processes associated with seafloor spreading e g incipient ridge push forces continental resistance to plate motion produced the shortening in the fundy basin shortening occurred during the transition from rifting to drifting as north america separated from northern africa and or during the early stages of drifting as the seafloor spreading centers of the north atlantic propagated northward

relative scale and the strength and deformability of rock masses abstract the strength and deformation of rocks depend strongly on the degree of fracturing which can be assessed in the field and related systematically to these properties appropriate mohr envelopes obtained from the rock mass rating rmr classification system and the hoek brown criterion for outcrops and other large scale exposures of fractured rocks show that rock mass cohesive strength tensile strength and unconfined compressive strength can be reduced by as much as a factor often relative to values for the unfractured material the rock mass deformation modulus is also reduced relative to young s modulus a cook book example illustrates the use of rmr in field applications the smaller values of rock mass strength and deformability imply that there is a particular scale of observation whose identification is critical to applying laboratory measurements and associated failure criteria to geologic structures

glacio seismotectonics ice sheets crustal deformation and seismicity abstract the last decade has witnessed a significant growth in our understanding of the past and continuing effects of ice sheets and glaciers on contemporary crustal deformation and seismicity this growth has been driven largely by the emergence of postglacial rebound models pgm constrained by new field observations that incorporate increasingly realistic rheological mechanical and glacial parameters in this paper we highlight some of these recent field based investigations and new pgms and examine their implications for understanding crustal deformation and seismicity during glaciation and following deglaciation the emerging glacial rebound models outlined in the paper support the view that both tectonic stresses and glacial rebound stresses are needed to explain the distribution and style of contemporary earthquake activity in former glaciated shields of eastern canada and fennoscandia however many of these models neglect important parameters such as topography lateral variations in lithospheric strength and tectonic strain built up during glaciation in glaciated mountainous terrains glacial erosion may directly modulate tectonic deformation by resetting the orogenic topography and thereby providing an additional compensatory uplift mechanism such effects are likely to be important both in tectonically active orogens and in the mountainous regions of glaciated shields in general the short term response to ice fluctuations is similar to the earth s response to fluctuations in water reservoirs with the subsequent increase or decrease in seismicity which depends on the pre existing stress state when the ice fluctuations occur on the spatial scale and magnitude of the late pleistocene glaciation and deglaciation however the viscoelastic response of the earth especially the mantle causes significant changes in crustal deformation and earthquake activity that is spatially extensive and temporally complex the regions of greatest ice thickness and the regions marginal to the late pleistocene ice sheets indicate the most dramatic evidence of earthquake faulting the mantle response to these large ice mass fluctuations and the change in mass between the oceans and land caused and continues to cause measureable crustal deformation at hundreds of kilometres from the ice margins for both tectonically active and cratonic regions palaeoseismic investigations of late pleistocene and holocene faults are an important tool in evaluating earthquake hazard the predicted response of the earth over this time however is very dependent on the model assumed for most regions far more carefully designed field observations are needed to constrain the existing rheological and ice models

neogene paleostress changes in the basin and range a case study at hoover dam nevada arizona at hoover dam 40 km southeast of las vegas nevada well exposed highly faulted miocene rocks provide an excellent opportunity to study the paleostress history of a very small area within a region where previous geologic studies indicate clockwise rotation of paleostress and a nearness to a major strike slip fault zone boundary within 0 5 km3 of rock the sense of slip was determined on almost 500 separate faults the fault slip data show internal consistency with respect to lithology size of faults and location within the small area with respect to fault slip however the data represent an in homogeneous mixture of primarily strike slip and dip slip motions from this mixture it is possible to resolve two distinct stress fields with directions of extension that differ by 60 each stress field corresponds to a mixture of strike slip and dip slip faults and thus the orientations of 1 and 2 are not tightly constrained if however the data are first separated into strike slip and dip slip faulting modes and subsequently searched for sub populations that correspond to contrasting paleostress orientations the computations yield tightly constrained tensors that illustrate two distinct stress fields with subhorizontal 3 axes that trend n50 e and n75 w the 1 and 2 axes permutate in two vertical planes that strike n40 w and n15 e because 1 and 2 are close in value relative to 3 these relationships suggest that strike slip and dip slip faulting belong to the same tectonic regime qualitative observations of polyphase slip fault fault offsets and fault bedding geometric relationships when evaluated in the context of changes in 3 orientation and permutations of 1 and 2 provide a basis for a two stage late cenozoic structural evolution at hoover dam these stages are 1 strike slip faulting partly pre tilt and dip slip faulting and associated stratal tilting and 2 mostly post tilt complexly interrelated strike slip oblique slip and dip slip faulting the qualitative evaluations indicate that strike slip and dip slip faulting alternated in time during the second stage of deformation and may have done so during the first these mixed mode movements probably represent stress oscillations in time and space rather than discrete stress reorganizations in contrast the two different orientations of 3 either represent a major clockwise rotation of the stress field or a major counterclockwise rotation of the rocks during the faulting history each alternative is consistent with regional geologic relationships and the choice of which is correct cannot be made within the small area that was studied

the effect of convergence angle on the kinematic evolution of strain partitioning in transpressional brittle wedges insight from analog modeling and high resoluiton digital image analysis 1 using analog modeling aided by digital image analysis dpiv we constrained the long term kinematic evolution of strain partitioning in transpressional brittle wedges as a function of convergence angle we ran a series of dry quartz sand experiments representing highly oblique continent continent collision convergence angles of 4 to 30 the digital image analysis provided high resolution constraints on the long term kinematic evolution of these wedges which could be subdivided in distinct kinematic stages comprising 1 an initial distributed strain stage and 2 an oblique wedge stage before 3 the stage of strain partitioning is reached thus we document the evolution of different deformation stages from a single plate tectonic boundary condition in addition the relationship between convergence angle kinematic stages and wedge geometry including fault dips and fault hierarchy was established the modeling results show that smaller convergence angles lead to steeper faults besides for a constant convergence angle the proshears that evolved during the strain partitioning stage were less steep than those formed during the oblique wedge stage the fault slip vector on individual fault segments was derived from the dpiv data set for each time increment quantifying the magnitude and orientation of slip on fault segments during the different kinematic stages in addition in the 7 5 and 15 models rotation of the slip vector by up to 40 was observed on a single proshear during the strain partitioning stage these observations allow to some degree a validation of existing analytical models of strain partitioning in particular the assumption of steady state

mechanisms of mass and heat transport during barrovian metamorphism a discussion based on field evidence from the central alps switzerland northern italy 1 tectonic and metamorphic data for the central alps switzerland italy are used to discuss this classic example of a barrovian metamorphic terrain notably the evolution of its thermal structure in space and time available p t t data indicate variable contributions of advective and conductive heat transport during collision and subsequent cooling and exhumation some areas experienced a prolonged period of partial melting while other areas at the same time show but moderate heating the barrow type metamorphic field gradient observed in the final orogen is the result of two distinct tectonic processes with their related advective and conductive heat transport processes the two tectonic processes are 1 accretion of material within a subduction channel related to decompression and emplacement of high pressure units in the middle crust and 2 wedging and related nappe formation in the continental lower plate the second process postdates the first one wedging and underthrusting of continental lower plate material produces heat input into lower crustal levels and this process is responsible for predominantly conductive heat transport in the overlying units the interacting processes lead to different maximum temperatures at different times producing the final barrovian metamorphic field gradient the south experienced rapid cooling whereas the north shows moderate cooling rates this discrepancy principally reflects differences in the temperature distribution in the deeper crust prior to cooling differences in the local thermal gradient that prevailed before the cooling also determined the relationships between cooling rate and exhumation rate in the different areas citation berger a s m schmid m engi r bousquet and m wiederkehr 2011 mechanisms of mass and heat transport during barrovian metamorphism a discussion based on field evidence from the central alps switzerland northern italy tectonics 30 tc1007 doi 10 1029 2009tc002622

lignite cleat studies from the first middle polish first lusatian lignite seam in central poland abstract some miocene lignite seams are characterized by the presence of natural discontinuities so called cleats most often they are opening mode fractures consisting of two orthogonal sets face and butt both almost perpendicular to the bedding this paper determines distributions of cleat orientation spacing and aperture from the first group of the middle polish first lusatian lignite seams mpls 1 which has been exploited inter alia in the jo win iib and kazimierz n opencast mines in central poland all observations and measurements were conducted at macroscopic scale the cleats mean orientations are ne sw and nw se dipping at a high angle 75 the first set of fractures refers to the face cleats and the second one to the butt cleats the spacing of face cleats is from 10 0 to 17 2 cm averaging 12 65 cm and the spacing of butt cleats is from 9 3 to 24 3 cm averaging 13 75 cm on the other hand aperture measurements of these cleats range from 0 2 to 1 9 cm averaging 0 68 cm and from 0 1 to 1 5 cm averaging 0 42 cm respectively the obtained results clearly indicate that face cleat orientations nw se are strictly parallel to the elongation of the main tectonic structures in the study area their origin may be explained in at least two ways that is by tectonic folding the maximum principal stress 1 was horizontal or by salt diapirism the maximum principal stress 1 was vertical in both cases the intermediate principal stress 2 was parallel to the face cleat strikes namely nw se although the well developed butt cleats in the context of regional geology provide additional evidence for the creation of an orthogonal system of fractures cleats in the cover of salt structures thus the nw se direction is characteristic of both the extent of the main tectonic units in central poland and the face cleat orientation in mpls 1

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

the post glacial landscape evolution of the north german basin morphology neotectonics and crustal deformation the recent evolution of the north german basin ngb which is presently a low seismic area was partly affected by glacial loading and unloading of the ice masses major stresses acting within the ngb are induced by the north atlantic ridge push the ongoing alpine collision and the post glacial rebound of fennoscandia present day horizontal stresses within the ngb are directed generally nw se but fan and bend north of 52 n towards nne major basement faults are directed nw se minor faults ne sw and nne ssw and are clearly detectable in geomorphological and satellite lineaments furthermore the drainage pattern and the distribution of lakes in northern germany follow exactly block boundaries and hence mark zones of present day subsidence the understanding of the post glacial morphology and reactivation of faults requires a view into the very heterogeneous crust and upper mantle below the ngb the re adjustment of the individual fault blocks during post glacial relaxation of the lithosphere leads to differential crust dependent uplift and probably to the formation of urstrom valleys the urstrom valleys and terminal moraines in northern germany appear to parallel the major tectonic lineaments and lithospheric block boundaries the lithospheric memory is expressed in the post glacial landscape evolution of the ngb

sandbox experiments on basin inversion testing the influence of basin orientation and basin fill analogue modelling experiments using brittle materials are performed to study the inversion of extensional structures asymmetric grabens of two different orientations are first created during a phase of extension and progressively filled they are subsequently shortened in the same direction the aim of our experiments is to determine factors affecting the style of deformation during inversion we specifically investigate variations in thickness and distribution of strong and weak layers constituting the graben fill and in initial basin orientation the main advantage of our experimental set up is that we have a complete control on graben location width infill and orientation before inversion the experiments show that shortening results only in limited reactivation of pre existing normal faults in general forward thrusts and backthrusts cut across normal faults into the footwall of the graben the forward thrusts either propagate parallel to the enveloping surface of faulted blocks or they cut across basin limiting normal faults at various angles the graben fill is mechanically extruded by displacement along forward thrusts that accommodate most of the shortening both pre existing faults and weak graben fill act as zones of weakness during inversion and determine the orientation and location of both backthrusts and forward thrusts the results of our experiments conform well to natural examples of inverted graben structures

three dimensional numerical modeling of slip rate variations on normal and thrust fault arrays during ice cap growth and melting 1 changes in the volumes of ice caps considerably alter the stress state of the lithosphere by generating a transient signal that is added to the tectonic background stress field these stress field changes in turn affect crustal deformation and in particular the slip behavior of existing faults here we use three dimensional finite element models to investigate how arrays of normal and thrust faults near a growing and subsequently melting ice cap are influenced in their slip evolution the results show that regardless of fault dip both types of faults experience a decrease in their slip rate during ice cap advance and an increase in their slip rate during ice cap retreat if they are located beneath the ice cap in contrast faults outside the ice cap that are loaded on their footwall or hanging wall only show the opposite pattern their slip rate increases during glacial loading and decreases during subsequent unloading if the load is located along strike of the fault that is at one of its tips the slip behavior of normal and thrust faults is different the normal fault shows a slip rate increase during unloading the thrust fault during loading our results explain the location and timing of deglaciation induced paleoearthquakes in scandinavia and the contrasting slip histories reported from normal faults in the basin and range province which are located at different positions relative to the former yellowstone ice cap more generally our findings imply that a uniform slip behavior of faults in formerly glaciated regions should not be expected

inversion tectonics and the evolution of the high atlas mountains morocco based on a geological geophysical transect an edited version of this paper was published by the american geophysical union agu copyright 1998 agu see also http www agu org pubs crossref 1999 1998tc900015 shtml http atlas geo cornell edu morocco publications beauchamp1999 htm

application of geometric models to inverted listric fault systems in sandbox experiments paper 2 insights for possible along strike migration of material during 3d hanging wall deformation abstract fault geometry is a primary control on hanging wall deformation in this study a series of positive inversion analogue experiments was conducted using rigid fault surfaces of true 3d geometry with consistent listric geometry along the transport direction the deformed geometry of the top horizon of the syn extension sequence on vertical serial sections was examined with a conventional 2d geometric restoration technique to calculate the inclined antithetic shear angle that best approximates the actual fault shape and to estimate the amount of apparent horizontal shortening during contraction the apparent shear inclination and the estimated apparent shortening show a systematic change along strike corresponding to the plan geometry of the master detachment surface at the hanging wall above embayments in the fault geometry the uplift is highest the apparent shear inclination is gentlest and the apparent horizontal shortening is greatest in contrast the apparent shear inclination is steepest and the estimated shortening is smallest above salients in the master detachment geometry where the uplift is lowest these changes suggest that the hanging wall displacement had an along strike component during deformation the hanging wall material moves from the regions above salients to those above embayments in the detachment surface during contraction average of the estimated apparent shortening was smaller than the actual amount of the experiments probably due to tectonic compaction this study shows that the geometry of the master detachment in plan view has the primary control on the lateral variation of the hanging wall deformation the data presented in this paper help understand 3d geometric relations between the hanging wall deformation and the underlying detachment surfaces

long term acoustic measurement of temperature variations in the pacific north equatorial current a 247 km path length sound transmission experiment using a single sound source sending to a remote receiver was performed during february june 1992 along the latitudinal line of 10 n in the north equatorial current off mindanao island phillipines the range averaged temperature was reconstructed at three layers 65 500 m 500 1500 m and 1500 3300 m through the inverse analysis of travel time data obtained between the source and receiver the temperature remained nearly constant during february march and increased by 0 8 c for the upper and middle layers and 0 2 c for the lower layer in the subsequent months a 0 8 c temperature increase was in good agreement with expendable bathythermograph results obtained at the start and finish of the experiment national oceanic and atmospheric administration advanced very high resolution radiometer images also show evidence of a warming of the surface water by 2 0 c during the same period it is concluded that this acoustic experiment observed a warm event which took place in the western equatorial pacific with the decay of the 1991 1992 el nino

an acoustic travel time method for continuous velocity monitoring in shallow tidal streams 1 long term variations of streamflow in a tidal channel were measured using a fluvial acoustic tomography fat system through one transmission path fat is an innovative acoustic technology that utilizes the time of travel method to determine velocity between two points from multiple ray paths that traverse the entire cross section of stream due to high spatial variability of flow distribution stationary adcp measurements were not likely to yield true section averaged flow velocity and moving boat adcp method was therefore used to provide reference data as such two short term moving boat adcp campaigns were carried out by the authors in the first campaign a couple of acoustic stations were added to the fat system in order to resolve flow angularity in addition to the mean velocity comparing the fat results with corresponding adcp section averaged flow direction and velocity indicated remarkable consistency second campaign was designed to capture the influence of salt wedge intrusion on the sound propagation pattern it was found that fat velocity measurements bias high if acoustic stations lay inside the cooler freshwater layer ray tracing hindcasts suggest that installing acoustic stations inside the salt wedge may significantly improve function of output of the system comparing salinities evaluated from long term fat travel time records with nodal salinity measurements provided by conductivity temperature sensors reveals the potential ability of fat in measuring salt flux

postglacial tectonics of the scottish glacio isostatic uplift centre new evidence combined with a detailed re evaluation of postglacial fault movements seismic activity and shoreline sequences suggests that the period of deglaciation and the early holocene was more seismically active than the mid to late holocene it is proposed that the large scale lateral displacements formerly proposed can not be justified rather all postglacial fault movements appear to be limited to metre scale vertical movements along pre existing fault lines in addition it is argued that the younger dryas ice advance may have produced localised crustal redepression but not the more widespread impact formerly proposed both tectonic and postglacial rebound stresses however may be needed to explain the contemporary seismotectonics of the scottish highlands

aeolian transport rates across raked and unraked beaches on a developed coast wind characteristics and aeolian transport were measured on a naturally evolving beach and dune and a nearby site where the beach is raked and sand trapping fences are deployed the beaches were composed of moderately well sorted to very well sorted fine to medium sand the backshore at the raked site was wider and the foredune was more densely vegetated and about 1 m higher than at the unraked site wind speeds were monitored using anemometers placed at 1 m elevation and sand transport was monitored using vertical traps during oblique onshore alongshore and offshore winds occurring in march and april 2009 inundation of the low backshore through isolated swash channels prevented formation of a continuously decreasing cross shore moisture gradient the surface of the berm crest was dryer than the backshore making the berm crest the greatest source of offshore losses during offshore winds the lack of storm wrack on the raked beach reduced the potential for sediment accumulation seaward of the dune crest during onshore winds and the higher dune crest reduced wind speeds and sediment transport from the dune to the backshore during offshore winds accretion at wrack seaward of the dune toe on the unraked beach resulted in a wider dune field and higher narrower backshore although fresh wrack is an effective local trap for aeolian transport wrack that becomes buried appears to have little effect as a barrier and can supply dry sand for subsequent transport aeolian transport rates were greater on the narrower but dryer backshore of the unraked site vegetation growth may be necessary to trap sand within zones of buried wrack in order to allow new incipient foredunes to evolve copyright 2010 john wiley sons ltd

the effect of wind gusts moisture content and fetch length on sand transport on a beach this paper reports on an analysis of instantaneous sediment transport in relation to wind gusts moisture content and fetch length from a field study carried out at skallingen denmark wind speeds were measured with cup anemometers and instantaneous sediment transport with vertical traps coupled to electronic balances moisture content was measured gravimetrically using samples taken along a beach profile at intervals of 1 to 2 h sediment transport and wind speeds were sampled at 1 hz and a 5 s running mean was used to smooth the data from the trap because of limitations of the balance resolution three measures of the threshold of sediment motion the intermittency threshold minimum threshold and maximum threshold were explored using data from five runs carried out on october 26 2000 the intermittency threshold and maximum threshold were largely insensitive to wind speed but varied spatially along the fetch distance the minimum threshold increased significantly with increasing mean wind speed as a result of reduced time for drying of the surface layer examination of time series for instantaneous wind speed and sediment transport for a number of runs on october 26 and november 6 2000 showed close agreement between fluctuations in wind speed and fluctuations in sediment transport cross spectral analysis of instantaneous wind speed and sediment transport for one run on each day where there was continuous transport showed high coherence between the two variables over a range of frequencies from 0 2 hz to 0 01 hz plots of all non zero instantaneous sediment transport values versus wind speed show considerable scatter in general transport rates are highest for traps located further from the upwind non erodible boundary i e along the fetch best fit power relationships show r2 values generally ranging from 0 4 to 0 6 and exponents ranging from 4 5 to 6 94 i e much higher than the traditional value of 3 found in most transport equations traps located close to the upwind boundary had lower r2 values and exponents 2 5

a process based model for aeolian sediment transport and spatiotemporal varying sediment availability aeolian sediment transport is influenced by a variety of bed surface properties like moisture shells vegetation and nonerodible elements the bed surface properties influence aeolian sediment transport by changing the sediment transport capacity and or the sediment availability the effect of bed surface properties on the transport capacity and sediment availability is typically incorporated through the velocity threshold this approach appears to be a critical limitation in existing aeolian sediment transport models for simulation of real world cases with spatiotemporal variations in bed surface properties this paper presents a new model approach for multifraction aeolian sediment transport in which sediment availability is simulated rather than parameterized through the velocity threshold the model can cope with arbitrary spatiotemporal configurations of bed surface properties that either limit or enhance the sediment availability or sediment transport capacity the performance of the model is illustrated using four prototype cases the simulation of two wind tunnel experiments from literature and a sensitivity analysis of newly introduced parameters

deglaciation seismotectonics a principal influence on intraplate seismogenesis at high latitudes abstract in many high latitude stable continental regions deglaciation dominates the current crustal strain field interference between polarised tectonic and radial deglaciation strain fields affects the deviatoric stress state and fault stability margins and in consequence both the levels and properties of seismicity throughout glacial loading and unloading the most notable present day affects of this strain interference are predicted to include alternating quadrants of enhanced seismicity and aseismicity around rebound domes and former peripheral forebulges such strain interference can explain much of the geography and timing of holocene earthquake occurrence across northern europe and eastern north america

dependence of horizontal stress magnitude on load dimension in glacial rebound models summary it has been proposed that the deglaciation of the northern hemisphere triggered large earthquakes within intraplate environments and in this paper we examine this hypothesis by evaluating quantitatively the stress state in the lithosphere produced by time dependent surface loads a series of models demonstrate the dependence of horizontal incremental stress in an elastic plate overlying an inviscid or viscoelastic mantle on the lateral extent of a load applied at the surface the horizontal stress is largest when the dominant wavelength that is twice the diameter of the load is close to eight times the elastic thickness of the plate when the mantle is inviscid and for the particular viscosity model employed in this paper close to 12 times the elastic thickness for a viscoelastic mantle at wavelengths close to the critical wavelength the horizontal incremental stress may be up to six times as large as the vertical incremental stress for appropriate earth model parameters amplification of horizontal stress is close to maximum for ice loads with a radius of 280 km comparable to the dimensions of the former ice sheet over great britain this amplification may be sufficiently large that loading by small ice sheets can lead to failure on marginally stable faults in contrast to the behaviour for large ice sheets the models also predict greater fault instability for fennoscandia than for the larger laurentide ice sheet consistent with the observation of large postglacial faults in northern sweden the model is used to predict the stability of faults and style of faulting due to rebound stresses in the absence of a background tectonic stress field since the last glacial maximum 18 000 years ago in northern europe within the formerly glaciated region thrust faulting is predicted to occur at the end of deglaciation and normal faulting is predicted to occur in peripheral regions for the entire period since the last glacial maximum

evaluation of aeolian sand transport equations using intertidal zone measurements saunton sands england sand transport rates were measured using a vertical sand trap along the intertidal zone of a beach in north devon england together with simultaneous monitoring of the wind speed on the beach and moisture levels in the surface layers of sand the results of 88 sand trap samples in a wide range of wind speeds showed that moisture levels up to 14 in the top 1 2 mm of the beach sand have no discernible effect on the transport rates transport rates measured from areas of the beach where the moisture was below this level are compared with the rates predicted by seven expressions based on theoretical and wind tunnel research together with the empirical results of other published research measured transport rates range from 0 0001 to 0 22 kg m 1 s 1 the results indicate that expressions based on a power relation between the wind speed and the transport rate and which include a threshold velocity term provide the best estimates of the observed transport rates

wind initiation thresholds of the moistened sands 1 the widely accepted bagnold type function for calculating threshold wind velocity or shear velocity was developed for dry sands but surface moisture is an extremely important variable controlling the entrainment process of sands by wind because the tensile force between the water molecules and sand grains produces cohesion here we report detailed wind tunnel experimental results on the threshold shear velocity of moistened sand of different sizes the results show that relative threshold shear velocity which is the ratio of threshold shear velocity of sand in the moistened state to that in the dry state is better related to moisture content than threshold shear velocity itself function modified after the bagnold equation has been developed to estimate the threshold shear velocities of moistened sands for a given grain size the threshold shear velocity is proportional to 1 km 1 2 where m is the moisture content and k is a coefficient depending on grain size

rates of aeolian transport on a beach in a temperate humid climate short term field measurements of aeolian transport using a saltiphone indicate that actual rates of transport deviate considerably from the potential rates predicted by transport equations when examined in detail however potential rates are approached during special conditions mostly when the wind blows offshore parallel or slightly oblique to the beach and relative humidity is below 85 also the potential rates of transport may be approached when wind speeds considerably exceed threshold speed even during showers the main cause of the large deviation of actual from potential rates is in the absence of transport during very wet conditions prolonged rainfall regardless of wind speed and the variation of threshold velocity with time the threshold velocity increases during wet conditions with onshore winds or because of the presence of algae therefore potential transport is defined as the transport optimum to predict the actual rates of transport accurately insight into the variation of the threshold velocity is essential aeolian transport of sand seems to be related to moderate events and not to extreme events conforming to the principle of magnitude and frequency

the effect of surface moisture on the entrainment of dune sand by wind an evaluation of selected models reliable predictions of wind erosion depend on the accuracy of determining whether erosion occurs or not among the several factors that govern the initiation of soil movement by wind surface moisture is one of the most significant some widely used models that predict the threshold shear velocity for particle detachment of wet soils by wind were critically reviewed and evaluated wind tunnel experiments were conducted on pre wetted dune sand with moisture contents ranging from 0 00 to 0 04 kg kg 1 sand samples were exposed to different wind speeds for 2 min moisture content was determined gravimetrically before and after each experiment and the saltation of sand particles was recorded electronically with a saltiphone shear velocities were deduced from the wind speed profiles for each moisture content the experiments were repeated at different shear velocities with the threshold shear velocity being determined by least squares analysis of the relationships between particle number rates and shear velocity within the 2 min test runs temporal changes in particle number rates and moisture contents were detected a steep increase in the threshold shear velocity with moisture content was observed when comparing the models large differences between the predicted results became apparent at a moisture content of 0 007 kg kg 1 which is half the moisture content retained to the soil matrix at a water tension or matric potential of 1 5 mpa the increase in wet threshold shear velocity predicted with the different models relative to the dry threshold shear velocity ranged from 117 to 171 the highest care should therefore be taken when using current models to predict the threshold shear velocity of wet sediment nevertheless the models of chepil 1956 proc soil sci soc am 20 288 292 and saleh fryrear 1995 soil sci 160 304 309 are the best alternatives available

gauging rivers during all seasons using the q2d velocity index method this paper presents a new model q2d for the velocity distribution in a channel cross section for use in estimating discharge it describes the model and its theoretical basis and presents the results of a case study the distribution is determined by combining the principle of maximum entropy with a probability distribution obtained by the solution of the poisson equation over the cross section the model uses observed depth and velocity in the water column where an acoustic doppler current profiler is installed to determine three key flow parameters to obtain velocity and discharge in addition if supporting field discharge measurements are available the model can be further calibrated to account for any asymmetry in the flow if velocity distribution data exist for the entire cross section the model can be adjusted to stretch the predicted velocity pattern to better conform to experimental observations when applied to the ch teauguay river quebec for both ice covered and open water q2d predict

influence of configuration of bulkheads on use of estuarine beaches by horseshoe crabs and foraging shorebirds construction of bulkheads is a common response to erosion of estuarine shorelines bulkheads are usually built incrementally resulting in wider sandy beaches remaining as enclaves between bulkhead segments this paper measures the characteristics of bulkheads and enclaves and evaluates 1 whether horseshoe crabs limulus polyphemus utilize enclaves for spawning when they provide partial sheltering during periods of high wave energies and 2 whether eggs become trapped in the enclaves and are available to shorebirds when the beaches in front of bulkheads are inundated the characteristics of bulkheads and beach enclaves were identified in five developed reaches in delaware bay usa counts of horseshoe crabs were made in enclaves in two of these reaches during times of high wave energies and compared to counts in nearby unarmored segments egg tracer and trapping experiments were conducted at one of the enclaves to assess egg movement results indicate that the percent of bulkheads intersecting the beach below mid foreshore varies from 10 to 50 spawning densities were greater in enclaves than on longer unarmored segments on some days enclaves serve as a sink for eggs moving along the base of the bulkheads most birds feeding on horseshoe crab eggs preferred sites outside the enclaves and bulkhead segments any advantage of bulkheads creating enclaves and sinks for eggs moving alongshore is likely overridden by their disruption to natural process and habitats but having unarmored enclaves between bulkhead segments may be preferable to one continuous bulkhead based on environmental benefits

long term measurement of stream flow and salinity in a tidal river by the use of the fluvial acoustic tomography system summary long term variation of stream flow of a tidal river was measured by an innovative technology called the fluvial acoustic tomography fat the reciprocal sound transmission was performed between two acoustic stations located on both sides of the river even in the tidal river with the periodic intrusion of salt wedges the cross sectional average velocities along the river stream axis estimated from the travel time difference data were consistent with the average velocities observed by an array of moored downward looking adcps the cross sectional average salinity was also estimated by using the mean travel time data collected from the reciprocal sound transmission the mean values of temperature measured by the conductivity temperature c t sensors and the ray simulation result the derived salinity data from the fat are comparable with that obtained by the c t sensors it is concluded that the fluvial acoustic tomography fat is a prospective method for the continuous monitoring of tidal river discharge and temperature salinity variations

continuous measurements of discharge from a horizontal acoustic doppler current profiler in a tidal river 1 acoustic doppler current profilers adcps can be mounted horizontally at a river bank yielding single depth horizontal array observations of velocity across the river this paper presents a semideterministic semistochastic method to obtain continuous measurements of discharge from horizontal adcp hadcp data in a tidal river in the deterministic part single depth velocity data are converted to specific discharge by applying the law of the wall which requires knowledge of local values of the bed roughness length z0 a new filtration technique was developed to infer cross river profiles of z0 from moving boat adcp measurements width averaged values of z0 were shown to be predominantly constant in time but differed between ebb and flood in the stochastic part of the method specific discharge was converted to total discharge on the basis of a model that accounts for the time lag between flow variation in the central part of the river and flow variation near the banks model coefficients were derived using moving boat adcp data the consistency of mutually independent discharge estimates from hadcp measurements was investigated to validate the method analyzing river discharge and tidal discharge separately inaccuracy of the method is attributed primarily to mechanisms controlling transverse exchange of momentum which produce temporal variation in the discharge distribution over the cross section specifically development of river dunes may influence the portion of the discharge concentrated within the range of the hadcp

the influence of pre existing thrust faults on normal fault geometry in nature and in experiments relations between normal faults and pre existing thrust faults are classically described in terms of three basic situations normal faults can cross cut thrust faults they can branch out from thrust faults at depth on a de collement level or they can entirely reactivate thrust planes the mechanical aspects of these types of interaction were studied by analogue modelling in which sand simulates the brittle rocks and silicone putty an interlayered de collement the models underwent compression producing thrust faults with variable dips followed by extension three possible ways of interaction are described here a no interaction occurs in the case of low dip thrust faults 32 1 and normal faults are developed independently displaying a listric geometry b branching at depth on the de collement level occurs when dip of the thrust faults reaches 32 1 in this case the dip of the normal faults whose geometry becomes planar decreases with increasing thrust dip we suggest that this change in dip of normal faults depends upon the rotation of stress tensor axes along the pre existing fault zone where a drop in the friction coefficient is likely to occur c reactivation occurs in brittle material when dip of the pre existing fault exceeds 41 1

aeolian sediment supply at a mega nourishment abstract mega nourishments are intended to enhance growth and resilience of coastal dunes on medium to long time scales by stimulation of natural sediment transport processes the growth and resilience of coastal dunes largely depends on the presence of a continuous supply of aeolian sediment a recent example of a mega nourishment is the 21 mm 3 mega nourishment known as the sand motor the sand motor is intended to nourish the entire holland coast over a period of two decades four years of bi monthly topographic measurements of the sand motor domain provide an opportunity to analyze spatiotemporal variations in aeolian sediment supply using an aeolian sediment budget analysis it appears that more than 58 of all aeolian sediment deposits originate from the low lying beaches that are regularly reworked by waves aeolian sediment supply from higher beaches diminished after half a year after construction of the sand motor likely due to the formation of deflation lag deposits that constitute a beach armor layer the compartmentalization of the sand motor in armored and unarmored surfaces suggests that the construction height is an important design criterion that influences the lifetime and region of influence for any mega nourishment

continuous measurements of flow rate in a shallow gravel bed river by a new acoustic system 1 the continuous measurement of river discharge for long periods of time is crucial in water resource studies however the accurate estimation of river discharge is a difficult and labor intensive procedure thus a robust and efficient method of measurement is required continuous measurements of flowrate have been carried out in a wide shallow gravel bed river water depth 0 6 m under low flow conditions width 115 m using fluvial acoustic tomography system fats that has 25 khz broadband transducers with horizontally omnidirectional and vertically hemispherical beam patterns reciprocal sound transmissions were performed between the two acoustic stations located diagonally on both sides of the river the horizontal distance between the transducers was 301 96 m fats enabled the measurement of the depth and range averaged sound speed and flow velocity along the ray path in contrast to traditional point transect measurements of discharge in a fraction of a second fats covers the entire cross section of river in a single measurement the flow rates measured by fats were compared to those estimated by moving boat acoustic doppler current profiler adcp and rating curve rc methods fats estimates were in good agreement with adcp estimates over a range of 20 to 65 m3 s 1 the rms of residual between the two measurements was 2 41 m3 s 1 on the other hand the flowrate by rc method fairly agreed with fats estimates for greater discharges than around 40 m3 s 1 this inconsistency arises from biased rc estimates in low flows thus the flow rates derived from fats could be considered reliable

delivery and movement of horseshoe crab eggs limulus polyphemus in the breaking waves and swash uprush of an estuarine foreshore abstract knowledge of conditions for entrainment of eggs and larvae from beach spawning sites is critical in determining the likelihood that these food sources will be delivered to shorebirds the exhumation of horseshoe crab eggs buried within the beach foreshore is a function of changes in wave and current velocities over a tidal cycle this field study was conducted to evaluate the temporal constraints to egg release at two different locations across the foreshore of a sandy estuarine beach in delaware bay new jersey wind wave current characteristics beach change and eggs in transport were sampled over two tidal cycles egg counts were determined using four colors of dyed egg tracers placed as point sources 5 and 10 m bayward of the expected upper limit of swash tracer recovery varied from 1 to 18 of the tracer eggs buried wave heights were relatively low instrumented hs 0 09 0 17 m but with long periods 5 6 8 8 s results reveal that egg release is discontinuous and occurs in pulses when the swash and breakers migrate across the injection points on the rising tide and when the breakers migrate past the injection points during the falling tide a lack of tracer at the upper 5 m injection point after early stages of high tide is likely due to the maximum disturbance depth being achieved early leaving no eggs within the swash boundary layer peaks in recovery of tracer initially buried at the lower 10 m location after the breakers migrated up the foreshore well past the injection location are likely from eggs deposited in the wrack on the upper beach or reburied in the sediment near the upper limit of swash and remobilized by high swash uprushes these results using point sources of tracer eggs suggest that the contribution of eggs from within the beach matrix is temporally variable across the foreshore most eggs are released during rising tide but additional eggs can be released during falling tide if the depth of activation of the bed is greater than on the rise due to net erosion or change to higher wave energy conditions successful shorebird foraging at other times in the falling tide appears due to transport of eggs released earlier in the tidal cycle and delivered alongshore and not due to eggs exhumed in situ at that time

basin inversion and contractional reactivation of inherited normal faults a review based on previous and new experimental models abstract compressional inversion of former extensional sedimentary basins is a particularly common phenomenon given that passive margins share the same destiny of being subsequently incorporated into fold and thrust belts during basin inversion pre existing faults may concentrate stress and localise future thrust ramps or may be reactivated recording reversal of movement from extension to reverse this process has attracted attention largely because of its economic implications related to petroleum and ore deposit prospects and seismic hazard assessment since more than two decades analogue modelling has been used to indentify and or test a number of parameters relevant for the inversion process this paper aims therefore to offer a reasoned review of the analogue modelling work done on the subject coupling such previous results with those of a new experimental series inspired to the northern apennines stratigraphy and evolution past models have explored the role of main factors governing fault reactivation susceptibility such as fluid pressure fault weakness fault steepness angle of shortening and sediment loading the new models have addressed the role played by geometry and strength of a basal ductile layer during inversion two sets of sand silicone models were first extended orthogonally at different velocities to produce dissimilar pre inversion internal geometries and then shortened coaxially at different velocities to vary the brittle ductile coupling the experimental results confirm the selectiveness of fault inversion and reveal strong similarities with structural styles of tectonic inversion reported from the northern apennines and various areas worldwide the preferred geological model inferred from this modelling involves contribution of 1 syn inversion rotation of pre existing faults to shallower dip and 2 rotation of principal stress axes which could explain the invariable reactivation of only one of the two oppositely dipping graben bounding faults these factors would thus interact with the other well established parameters controlling the fault reactivation process

postglacial faulting in eastern canada nature origin and seismic hazard implications abstract at more than 70 locations in southeastern canada and the adjacent united states tiny bedrock faults displace glacial striations that are about 10 000 years old these reverse faults mostly of small displacement occur in a broad arc from western ontario to newfoundland the faults lie near the margin of the laurentian ice sheet strike generally tangential to it and imply compression nearly normal to the ene directed contemporary regional stress these observations and some age relationships suggest that the faults formed very soon after deglaciation perhaps in the first few thousand years after ice melting in each place and probably represent the release of stresses caused by flexural deformation of the upper crust although the individual offsets are small the faults are believed to be pervasive and individual outcrops reflect amounts of stress relief consistent with stresses implied by the postglacial tilt of nearby lake shorelines

offshore aeolian sediment transport across a human modified foredune concepts derived from previous studies of offshore winds on natural dunes are evaluated on a dune maintained for shore protection during three offshore wind events the potential for offshore winds to form a lee side eddy on the backshore or transfer sediment from the dune and berm crest to the water are evaluated as are differences in wind speed and sediment transport on the dune crest berm crest and a pedestrian access gap the dune is 18 20 m wide near the base and has a crest 4 5 m above backshore elevation two sand trapping fences facilitate accretion data were obtained from wind vanes on the crest and lee of the dune and anemometers and sand traps placed across the dune on the beach berm crest and in the access gap mean wind direction above the dune crest varied from 11 to 3 deg from shore normal no persistent recirculation eddy occurred on the 12 deg seaward slope wind speed on the berm crest was 85 89 of speed at the dune crest but rates of sediment transport were 2 27 times greater during the strongest winds indicating that a wide beach overcomes the transport limitation of a dune barrier limited transport on the seaward dune ramp indicates that losses to the water are mostly from the backshore not the dune the seaward slope gains sand from the landward slope and dune crest sand fences causing accretion on the dune ramp during onshore winds lower the seaward slope and reduce the likelihood of detached flows during offshore winds transport rates are higher in access gaps than on the dune crest despite lower wind speeds because of flatter slopes and absence of vegetation transport rates across dunes and through gaps can be reduced using vegetation and raised walkover structures

basin inversion and fault reactivation in laboratory experiments abstract a series of analogue models have been performed to get insights into the relationships between the reactivation of pre existing normal faults and the orientation of a successive compressive stress field the models were deformed in two phases 1 a first extension phase h 3 generating a graben and 2 a successive compressive phase with the orientation of the shortening direction h 1 trending between 0 and 90 obliquity angle to the faults bounding the graben the deepening of this graben was accompanied by syn tectonic sedimentation that included a basal ductile layer simulating salt in nature overlain by a brittle sand pack the experimental results suggest that the development of compressive structures is strongly controlled by the pre existing normal faults and by the obliquity angle the experiments have invariably shown that the extensional faults were reactivated during shortening whatever the value of the angle whereas strike slip reactivation of major normal faults is favoured by low obliquity angles mostly dip slip reactivation of pre existing structures is instead promoted for high obliquity angles the analysis of model results highlights the important role played by a ductile layer at the base of the basin fill and the obliquity angle in controlling both strain partitioning and brittle ductile decoupling

sedimentological evidence of pleistocene earthquakes in nw poland induced by glacio isostatic rebound abstract soft sediment deformation structures are abundantly present in two levels within warthanian eemian lacustrine sediments at siekierki near the polish german border the two event horizons show intense folding collapse sag and load structures indicative of liquidization and fluidization the structures must have been caused by sudden shocks most probably resulting from earthquakes that were induced by glacio isostatic rebound probably after the warthanian deglaciation such seismites have not been previously recognized in polish quaternary sediments they provide supporting evidence for glacio isostatic movements that were interpreted up till now based on drilling lithostratigraphic geophysical and geodetic data the recognition of seismites in nw poland may help recognize other deformed event horizons in pleistocene sediments as glacio isostatic or neotectonic seismites

graben inversion in nature and experiments the inversion of crustal scale basement grabens is studied here through laboratory experiments on small scale models and available oil industry seismic lines from the southern north sea two basic configurations are considered first both the basement and the sedimentary cover are brittle and inversion does not involve any potential decollement between them second the basement and sedimentary cover are separated by a weak ductile layer e g salt which can allow decollement of the cover during both extension and later compression and inversion the second configuration is more complicated and can lead to a large variety of geological structures laboratory experiments were carried out on brittle ductile models built with sand to represent brittle layers basement and sedimentary cover and silicone putty to simulate the decollement layer between basement and cover a mechanically based classification of inversion structures is proposed the effects of some crucial parameters are investigated including obliquity between the direction of shortening and normal faults as well as strength profiles and the presence or absence of salt diapirs the experimental investigation leads to the following conclusions 1 the inversion of the graben by reactivation of normal faults implies that the angle between the direction of compression and the graben is less than 45 2 if there is a superficial decollement e g basement cover interface inversion initiates low dipping thrust faults in the cover localized at graben borders 3 salt diapirs or salt walls localized along the graben borders in the cover are preferential sites for the development of thrust faults and 4 when the cover is decoupled from the basement by a decollement layer inversion induced deformation in the cover which is partitioned between thrust faults along the graben borders and strike slip faults within the graben trending oblique to the graben borders experimental results are compared with field examples in particular from the southern north sea

geological evidence for neotectonic activity during deglaciation of the southern sperrin mountains northern ireland in the southern sperrin mountains northern ireland stacked glacigenic sequences that accumulated during deglaciation ca 17000 13000 yr bp overlie a basement of jointed and mascerated bedrock the glacigenic sequences comprise interbedded glaciotectonic shears diamictic breccias and rock rafts at one site a normal fault with a metre scale vertical displacement cuts through part of the sequence and is overlain by a glacial diamict sediments at an adjacent site show that faulting and associated hydrothermal activity was related to neotectonic reactivation of pre existing caledonian lineaments caused by ice unloading from stratigraphical and directional evidence fault reactivation occurred early in the deglaciation after north central ireland ice had retreated southwards into lowland areas but before sperrin mountain ice readvanced from the north this relationship provides evidence for the relative timing of neotectonic activity in northern ireland and demonstrates the effects of glacio isostatic unloading near ice sheet centres copyright 1999 john wiley sons ltd

discharge estimation from h adcp measurements in a tidal river subject to sidewall effects and a mobile bed horizontal acoustic doppler current profilers h adcps can be employed to estimate river discharge based on water level measurements and flow velocity array data across a river transect a new method is presented that accounts for the dip in velocity near the water surface which is caused by sidewall effects that decrease with the width to depth ratio of a channel a boundary layer model is introduced to convert single depth velocity data from the h adcp to specific discharge the parameters of the model include the local roughness length and a dip correction factor which accounts for the sidewall effects a regression model is employed to translate specific discharge to total discharge the method was tested in the river mahakam representing a large river of complex bathymetry where part of the flow is intrinsically three dimensional and discharge rates exceed 8000 m3 s 1 results from five moving boat adcp campaigns covering separate semidiurnal tidal cycles are presented three of which are used for calibration purposes whereas the remaining two served for validation of the method the dip correction factor showed a significant correlation with distance to the wall and bears a strong relation to secondary currents the sidewall effects appeared to remain relatively constant throughout the tidal cycles under study bed roughness length is estimated at periods of maximum velocity showing more variation at subtidal than at intratidal time scales intratidal variations were particularly obvious during bidirectional flow conditions which occurred only during conditions of low river discharge the new method was shown to outperform the widely used index velocity method by systematically reducing the relative error in the discharge estimates

the effects of surface moisture on aeolian sediment transport threshold and mass flux on a beach this paper presents results from a study designed to explore the effects of beach surface moisture and fetch effects on the threshold of movement intensity of sand transport by wind and mass flux the experiment was carried out over a period of five weeks at greenwich dunes prince edward island canada in may and june 2002 moisture content was measured with a delta t moisture probe over a 50 m by 25 m grid established on the beach measurements of wind speed and direction were made with arrays of cup anemometers and a two dimensional sonic anemometer transport intensity was measured at a height of 2 4 cm above the bed using omnidirectional saltation probes which count the impact of saltating grains on a piezoelectric crystal anemometers and saltation probes were sampled at 1 hz sand transport was measured with vertical integrating sand traps over periods of 10 20 minutes results show that where there is a considerable supply of dry sand the saltation system responds very rapidly 1 2 s to fluctuations in wind speed i e to wind gusts where sand supply from the surface is limited by moisture mean transport rates are much lower and this reflects in both a reduction in the instantaneous transport rate and in a transport system that becomes increasingly intermittent threshold wind speed is significantly correlated with an increase in surface moisture content near the upwind end of the beach fetch but the relationship is not significant at the downwind end where sediment transport is initiated primarily by saltation impact from upwind mass flux increases with increasing fetch length and the relationship is described best by a power function further work is necessary to develop a theoretical function to predict the increase in transport with fetch distance as well as the critical fetch distance copyright 2007 john wiley sons ltd

wind blown sand on beaches an evaluation of models five models for predicting rates of aeolian sand transport were evaluated using empirical data obtained from field experiments conducted in april 1994 at a beach on inch spit co kerry republic of ireland measurements were made of vertical wind profiles to derive shear velocity estimates beach slope and rates of sand transport sediment samples were taken to assess characteristics of grain size and surface moisture content estimates of threshold shear velocity were derived using grain size data after parsing the field data on the basis of the quality of shear velocity estimation and the occurrence of blowing sand 51 data sets describing rates of sand transport and environmental conditions were retained mean grain diameter was 0 17 mm surface slopes ranged from 0 02 on the foreshore to about 0 11 near the dune toe mean shear velocities ranged from 0 23 m s 1 just above the observed transport threshold to 0 65 m s 1 rates of transport ranged from 0 02 kg m 1 h 1 to more than 80 kg m 1 h 1 these data were used as input to the models of bagnold bagnold r a 1936 the movement of desert sand proc r soc london a157 594 620 kawamura kawamura r 1951 study of sand movement by wind translated 1965 as university of california hydraulics engineering laboratory report hel 2 8 berkeley zingg zingg a w 1953 wind tunnel studies of the movement of sedimentary material proc 5th hydraulics conf bull 34 iowa city inst of hydraulics pp 111 135 kadib kadib a a 1965 a function for sand movement by wind university of california hydraulics engineering laboratory report hel 2 8 berkeley and lettau and lettau lettau k and lettau h 1977 experimental and micrometeorological field studies of dune migration in k lettau and h lettau eds exploring the world s driest climate university of wisconsin madison ies report 101 pp 110 147 correction factors to adjust predictions of the rate of transport to account for the effects of slope and moisture content were calculated using the models of bagnold bagnold r a 1973 the nature of saltation and bed load transport in water proc r soc london ser a 332 473 504 and belly belly p y 1964 sand movement by wind u s army corps eng cerc tech mem 1 washington d c 38 pp respectively none of the models was able to produce a strong correspondence between measured and predicted rates of transport best results were obtained using the bagnold and zingg models and the kadib model was the least viable of this group the influence of sediment moisture content appeared to be the critical factor in degrading model viability overall none of the models is adequate for general applications to coastal aeolian environments where moisture content complications tend to override the predictive competence of the simple transport formulations c 1998 elsevier science b v