analysis on residual coarse sediment transport in estuaries abstract the analytical expression for residual coarse sediment transport of van de kreeke and robaczewska 1993 is extended for estuaries the major extension concerns the contribution to sediment transport by residual current which is ignored by van de kreeke and robaczewska 1993 tidal constituents m 0 m 2 s 2 n 2 m 4 ms 4 mn 4 m 6 k 1 and o 1 are used to represent the collinear tidal current it is shown that interactions of m 0 and all tidal constituents contribute to residual sediment transport when m 0 is not negligible thus a representative tide based on m 2 and its overtides only is not sufficient to drive morphodynamic models in this case the present analysis also reveals that triad interactions of compound tides with their basic constituents i e ms 4 with m 2 s 2 and mn 4 with m 2 n 2 contribute to residual sediment transport besides interactions of m 0 and m 2 and of m 2 and its even overtides m 4 and m 6 the extended analytical expression is applied to determine residual sediment transport in the yangtze estuary it is demonstrated that a single representative tide does not exist for morphodynamic models in this case this conclusion is likely to also apply to other estuaries in which residual flow is not negligible

the initiation and development of metamorphic foliation in the otago schist part 1 competitive oriented growth of white mica the 3d shape size and orientation data for white mica grains sampled along two transects of increasing metamorphic grade in the otago schist new zealand reveal that metamorphic foliation as defined by mica shape preferred orientation spo developed rapidly at sub greenschist facies conditions early in the deformation history the onset of penetrative strain metamorphism is marked by the rapid elimination of poorly oriented large clastic mica in favour of numerous new smaller grains of contrasting composition higher aspect ratios and a strong preferred orientation the metamorphic mica is blade shaped with long axes defining the linear aspect of the foliation and intermediate axes a partial girdle about the lineation once initiated foliation progressively intensified by an increase in the aspect ratio size and alignment of grains although highest grade samples within the chlorite zone record a decrease in aspect ratio and reduction in spo strength despite continued increase in grain size these trends are interpreted in terms of progressive competitive anisotropic growth of blade shaped grains so that the fastest growth directions and blade lengths tend to parallel the extension direction during deformation the competitive nature of mica growth is indicated by the progressive increase in size and resultant decrease in number of metamorphic mica with increasing grade from c 1000 relatively small mica grains per square millimetre of thin section at lower grades to c 100 relatively large grains per square millimetre in higher grade samples reversal of spo intensity and grain aspect ratio trends in higher grade samples may reflect a reduction in the strain rate or reduction in the deviatoric component of the stress field

magnetic susceptibility fabrics in slates structural mineralogical and lithological influences abstract a single penetrative tectonic deformation of archean greywackes accompanied by low grade metamorphism generated low field magnetic susceptibility fabrics that are coaxial with the rock s schistosity although there are multiple sources of magnetic susceptibility pre metamorphic magnetite and the metamorphic minerals pyrrhotite biotite and chlorite variety thuringite daphnite aphrosiderite are responsible for the anisotropy of susceptibility these minerals grew with preferred crystallographic orientations influenced by the prevailing stress regime on its own rotation cannot be invoked to explain the alignment of the metamorphic minerals there are varying proportions of at least two of these minerals in most specimens for 153 specimens the degree of anisotropy increases as the mean susceptibility increases over the range from 100 to 700 in units of 10 6 s i theory shows that this is to be expected either due to increasing the traces of strongly oriented ferrimagnetics or due to increasing the proportion of chlorite in the latter case this simultaneously increased its preferred orientation by closer packing stress influenced crystallization of chlorite rapidly achieves saturation alignment and a limiting magnetic anisotropy although strain may continue to increase samples taken through individual graded beds show that the susceptibility ellipsoid varies from oblate in slaty rocks to a neutral shape in sandier rocks however its orientation is always structurally controlled with the minimum susceptibility axis perpendicular to schistosity

reconstructing the kinematic evolution of curved mountain belts internal strain patterns in the wyoming salient sevier thrust belt u s a analyses of mesoscopic structural and strain patterns in red beds of the triassic ankareh formation and limestones of the jurassic twin creek formation in concert with complementary paleomagnetic studies constrain the three dimensional kinematic evolution of curved fold and thrust systems in the wyoming salient of the sevier thrust belt spaced cleavage fracture and vein networks minor folds and minor faults in limestones and red beds accommodated early layer parallel shortening lps concentrated in front of the growing thrust wedge along with minor strike parallel extension and wrench shear related to the development of orogenic curvature strain estimated using mass balance relations for cleavage seams crinoid ossicles in bioclastic limestone and reduction spots in red beds displays systematic regional patterns principal shortening directions are subperpendicular to structural trend around the salient reflecting a combination of primary curvature and secondary rotation of early lps fabrics lps magnitudes vary from 5 in central parts of the frontal hogsback thrust system where cleavage is absent to 10 30 in the more interior crawford thrust system where cleavage intensity is moderate to strong strain also increases toward the salient ends internal strain is a significant component of total deformation and should be considered when restoring cross sections strain patterns are consistent with a kinematic model involving curved fault slip and differential shortening that produced progressive secondary curvature during thrusting

magnetic susceptibility anisotropy strain and progressive deformation in permian sediments from the maritime alps france abstract the relationships among magnetic susceptibility anisotropy finite strain and progressive deformation have been studied in permian red shales and slates of the maritime alps southeastern france these rocks contain deformed reduction spots which serve as finite strain indicators the magnetic fabric of undeformed regions is modified during deformation to yield characteristic magnetic susceptibility anisotropy patterns and a magnetic equivalent of the deformation path derived from strain measurements the magnetic fabric changes progressively from oblate to prolate and back to oblate as deformation increases the quantitative relationships between natural strain and magnetic anisotropy in these rocks have been determined they differ between the less and more deformed areas perhaps due to a change in deformation mechanism accompanying an increase in metamorphism the relationships provide a rapid means of strain determination using magnetic measurements but their variation emphasizes the need for local structural control

will river erosion below the three gorges dam stop in the middle yangtze abstract the environmental impact of the three gorges dam has been a subject of vigorous academic political and social debate since its inception this includes the key issue of post dam river channel erosion which was predicted by the feasibility study to extend to the river mouth in this paper we examine the geomorphic response of the channel of the middle yangtze for 660 km downstream of the dam using data on channel characteristics bed material and sediment transport we show that in the decade following the dam closure pre dam seasonal erosion has been replaced by year round erosion a pattern most marked at the upstream end of the study area the sediment carrying capacity of the river channel has been largely reduced below the dam the locus of bed scour has moved progressively downstream ceasing as the bed material became too coarse to be transported e g d 50 0 29 mm pre dam coarsened to 20 mm below the dam by 2008 about 400 km below the dam there is a reduction in channel slope that changes the sediment carrying capacity from 0 25 kg m 3 to only about 0 05 kg m 3 which is insufficient to move bed sediment the new long term hydro morphological equilibrium that will be established in this section of the middle yangtze will prevent the further incision downstream initiated by the three gorges dam the results suggest that the full extent of adverse environmental impact predicted by the pre dam studies will not eventuate

overview of inert tracer experiments in key belgian soil types relation between transport and soil morphological and hydraulic properties to investigate relations between solute transport soil properties and experimental conditions we summarize results from leaching experiments that we carried out in a range of soils at different scales column 0 3 1 0 m id 1 0 m length and field plot scale and using different leaching rates 0 5 30 cm d 1 the lateral mixing regime and longitudinal dispersion were derived from time series of tracer concentrations at several depths in the soil field and column scale transport were similar in loam and silt loam soils the mixing regime was related to soil morphological features such as vertical tongues stratification macropores and a water repellent layer the dispersion increased in all soils more than linearly with increasing leaching rate implying that the dispersivity is not an intrinsic soil characteristic the change of dispersivity with leaching rate was linked to the unsaturated hydraulic conductivity using a multidomain conceptualization of the pore space

implications of flow control by the three gorges dam on sediment and channel dynamics of the middle yangtze changjiang river china the impacts of a dam on the river downstream in terms of hydrology and morphology are determined by a complex mix of variables that includes the patterns of release of water through the dam and the characteristics of the downstream channel scour of the downstream channel is a common response because large dams cause a significant interruption to sediment continuity here we show that in the case of china9s three gorges dam on the yangtze river the outcome is complicated as is commonly the case in large rivers the downstream channel and floodplain system compose an area of long term sediment accumulation and unstable channels with seasonally contrasting erosion and deposition patterns related to the migrating seasonal monsoon rainfall zones in achieving one of the main purposes of this dam that of flood control in the middle and lower basins the pattern of flows released from the dam will closely resemble those seasonal flows that are responsible for channel instability in the middle catchment thus effectively making erosive conditions the most common during a year there is obviously concern about the ultimate impact of sediment storage in the dam on the dynamics of the delta and adjacent coast and we show that this depends on the trajectory and duration of the erosive responses in the middle yangtze basin in this particular case the outcome is of great significance to the well being of the densely populated riparian areas of the river

susceptibility and predictability of conditions for preferential flow preferential flow in the field might be caused by various factors and is difficult to observe in situ this experimental study was designed to identify the combined effects of air entrapment surface desaturation suction head soil layering and water repellency hydrophobicity of the porous media on unstable preferential flow or fingering in the vadose zone the predictability of unstable flow was studied on the basis of two existing criteria for gravity fingering 1 a velocity criterion proposed by hill and parlange 1972 and 2 a pressure head criterion by raats 1973 and philip 1975 two dimensional transparent chambers 60 cm high 41 5 cm wide and 2 8 cm thick and 90 cm deep 74 5 cm wide and 1 8 cm thick were used to visualize water infiltration into a water wettable sand a water wettable loam differently layered sand and loam and a water repellent sand the results suggested that infiltration into the homogeneous sand and a sand over loam system without the effects of air entrapment and surface desaturation was unconditionally stable infiltration into the loam was also stable as observed in the limited chambers the flow was unconditionally unstable in a fine over coarse stratified sublayer and conditionally unstable in the homogeneous sand under the effects of air entrapment and surface desaturation in multiple layered systems infiltration flow was semiunstable fingers developed in the sand layer and were stabilized in the loam in the repellent sand the wetting front was unstable under low ponding conditions however it was stabilized when the ponding depth exceeded the water bubbling entry value of the hydrophobic medium both the velocity and pressure head criteria predicted fingering in the sand layers with the effects of gravity however the criteria failed to predict stable flow in the loam indicating that the capillary stabilizing effects on the flow need to be included in theoretical developments finally the observed width and speed of the fingers and the system flux were found to be always higher under air draining fingering conditions than with fingering under air confined conditions

magnetic fabric implications for the relationships between deformation mode and grain growth in slates from the borrowdale volcanic group in the english lake district abstract in the less chlorite rich slates from the borrowdale volcanic group chlorite magnetic fabric almost corresponds to fabric resulting from deformation following the march fernandez model but chlorite grain rotation could be related to the first stages of the tectonic deformation in the other slates the chlorite grains probably impinging after these stages upon one another and a simple grain rotation mechanism being therefore no longer possible

a study of colour changes in purple green slate by petrological and rock magnetic methods abstract the purple cambrian slates of north wales show colour changes to green in bedding parallel patches and ellipsoidal spots these are referred to as reduction spots but the process is more complex the colour change is not simply associated with the reduction of iron the green discoloration is accompanied by diffusion of fe 3 away from and possibly by mg and ca towards the green material the actual colour change is brought about by the replacement of the fine metamorphic hematite pigment with magnetite however coarser clastic hematite persists in the green slate the green slate has twice as much chlorite and traces of magnetite despite having less total fe the additional chlorite is chiefly responsible for the doubling of the magnetic susceptibility of the green slate with respect to the purple slate chlorite and epidote have the same compositions in both green and purple slates despite the difference in whole rock fe content both purple and green slates behave predominantly as paramagnets between 194 c and 700 c the anisotropy of low field susceptibility magnetic fabric is increased by heating and therefore made easier to measure and the principal directions of anisotropy are preserved heating to 700 c increases the saturation isothermal remanence dramatically and increases its anisotropy due to the growth of single domain magnetite however heating is not universally recommended as a means of enhancing otherwise feeble magnetic fabrics some other slates and schists show regressive changes in magnetic fabric on heating with erratic changes in principal directions

effects of navigational works on morphological changes in the bar area of the yangtze estuary abstract to improve navigability of the major access channel into shanghai harbor a large scale deep waterway project was carried out in the north passage np of the yangtze estuary in this paper we investigate how the navigational works affected morphological changes of this channel as well as those of the adjacent north channel nc hengsha east shoal hes jiuduansha shoal jds and the south passage sp morphological changes were assessed by analyzing digitized bathymetric data of this area prior to and after execution of the engineering works the qualitative relations between these changes along with the hydrodynamic changes as a result of the construction of engineering works were subsequently investigated the results reveal that the construction of training walls groins and jetties resulted in decreased ebb transport in the upper reach of the np and increased ebb transport in the upper reach of the sp in turn this led to intensive upstream erosion with large amounts of sediment transported seaward in the sp and associated sedimentation in the downstream area at the same time intense siltation occurred in the upper reach of the np while the main channel of the np mainly experienced erosion caused by the construction of training walls and groins that concentrated ebb flow in the main channel the waterway deepened significantly in previously shallow areas small tidal channels in the hes which used to connect the np and the nc were cut off by the northern training wall consequently residual flow in the middle reach of the nc flowed directly toward the northern bank of the hes leading to local erosion flow obstruction by the southern training wall reduced the upstream propagation of the flood tide in the sp as a result a collection of small flood channels evolved under the flushing action of flood currents in the jds preventing the natural trend of horizontal extension of the jds however the flow obstruction enhanced the vertical accretion of the jds

paleomagnetism carried by crystal inclusions the effect of preferred crystallographic orientation abstract randomly oriented phlogopite crystals from a pegmatite contain submicroscopic inclusions of magnetite the inclusions have oblate magnetic fabrics subparallel to the ab crystal plane alternating field demagnetization of individual crystals shows that the remanence is influenced by the crystal symmetry of the phlogopite host the magnetizations isolated by alternating field demagnetization either cluster close to the a axis or scatter in the ab plane coarse grained igneous and metamorphic rocks can only record a paleofield direction accurately if there is a suitable orientation distribution of the rock forming minerals that host the ferromagnets an isotropic distribution of rock forming minerals is preferable but it is not obligatory rock forming minerals that have l fabrics or s fabrics with a strong l component are also suitable if they contain oblate inclusion fabrics of ferromagnets

linking the infilling of the north branch in the changjiang yangtze estuary to anthropogenic activities from 1958 to 2013 abstract many tidally dominated estuaries of the world are experiencing variations in bottom topography due to changes in natural forcings and intensive human activities here we focus on the morphological evolution of the north branch nb a tidally dominated distributary of the changjiang estuary our analysis is based on long term bathymetric and hydrological data collected between 1950 and 2010 the results show that mean water depth channel volume below 0 m and channel volume below 5 m have respectively decreased by 43 53 and 92 in the last 50 years a reduction of the whole estuarine surface with aggradation in elongated tidal sand bars and erosion at the mouth are the main morphological variations of the nb while a decrease in channel volume below 5 m due to infilling is the second mode of morphological change while the drastic decrease in sediment load from upstream is likely unrelated to the silting of the nb local land reclamation along the banks is directly responsible for the reduction of estuarine surface area and related tidal prism between 1958 and 2013 enhanced flood tide currents resulted in a large import of sediments from offshore into the nb triggering a sustained decrease in channel volume below 0 m it is argued that the recovery of the funnel shaped configuration of the estuary by restoring mud flats over 0 m dredging the southern part of the estuary bend and forbidding land reclamation could prevent the silting of the nb otherwise the nb will likely vanish in few decades

human influence and the changing geomorphology of mediterranean deltas and coasts over the last 6000 years from progradation to destruction phase the present geomorphology of the mediterranean s coasts is largely a product of an intricate long term relationship between nature and human societies a cradle of ancient civilisations the mediterranean has seen its shores occupied by humans since prehistory and is therefore a particularly pertinent unit of analysis the morphotectonic context and other forcing agents e g climate shaped out a highly diversified coastal morphology and generated a sediment supply regime potentially favourable to the formation of numerous open coast deltas and bay head deltas in infilled rias as sea level stabilised during the mid holocene this supply of riverine sediment has also been the key agent in mediating human occupation of the mediterranean s clastic coasts expressions of this relationship have been extensively archived in clastic coastal deposits including base level deltaic and estuarine sedimentary sinks which comprise records to explore the interactions between geosystems and the human environment the stratigraphic sequences in these coastal sedimentary archives comprise in many places a clearly identified anthropogenic signature notably in ancient harbours some of which underwent extremely rapid silting up due to massive sediment sourcing generated by new agricultural practices from the neolithic onwards increasing human influence especially over the last 3000 years has been in turn an important driver of changes in sediment supply strongly modulating deltaic development pulses of sediment supply from catchments rendered vulnerable by human perturbations during the roman period resulted in a new cycle of inception of many other deltas and in rapid delta growth e g the ebro the po the arno and the ombrone another progradation dynamic during the little ice age at a time of strong rural population growth river discharge increases technological developments and urbanisation further consolidated delta growth understanding the life cycle of these deltas since their initial formation is in turn key to unravelling the relative role of natural and anthropogenic forcing agents rapid climate changes are deemed to have contributed through both the stripping of landscapes rendered fragile by human activities and active fluvial sediment transport to the coast but disentangling climate change effects from human impacts in the mediterranean remains a challenge the patterns of subsequent deltaic growth and delta morphodynamics reflect adaptations to pulsed sediment supply river discharge variations the microtidal fetch limited context of the mediterranean and direct engineering interventions the progradation dynamic of the roman period and little ice age contrasts markedly with the situation of common coastal destabilisation over the last two centuries particularly well documented for the last 50 years this period has been characterised by reduced sediment flux to base level geosystems due to catchment reforestation retenion within reservoirs fluvial regulation and dredging resulting in the erosion of deltas and barrier lagoon and beach dune systems large stretches of shoreline and narrow coastal plains have been massively engineered for coastal defence and protection against erosion but also for the construction of marinas leisure harbours and artificial beaches resulting in the emergence of veritable artificial seafronts these interventions have collectively and progressively raised societies to a pervasive and overarching position in the geomorphic stability instability of the mediterranean s coasts a situation that will be exacerbated by pressures from sea level rise paving the way for rampant coastal erosion and delta destruction

how stable is the mississippi delta large deltas are commonly believed to exhibit rapid rates of tectonic subsidence largely due to sediment loading of the lithosphere as a result deltaic plains are prone to accelerated relative sea level rise coastal erosion and wetland loss hurricane katrina s devastation testifies to the severe threat that these processes pose to the mississippi delta but the relative role of tectonics versus other mechanisms causing land subsidence remains elusive relative sea level records derived from basal peat have the potential to quantify differential crustal movements over holocene time scales with exceptionally high accuracy and precision here we present new sea level index points from two study areas in the southwestern mississippi delta that essentially coincide with a recently published detailed relative sea level record from the eastern part of the delta our results show that differential vertical movements among the three study areas have been only 0 1 mm yr 1 w e compare our evidence with a recent sea level compilation from the caribbean to a large extent based on data from areas that are tectonically stable our sea level index points nearly coincide with the caribbean data showing surprising tectonic stability for considerable sections of the mississippi delta however the well documented high subsidence rates in and near the birdfoot of the mississippi delta indicate that different conditions prevail there the rapid wetland loss in coastal louisiana is likely due to a considerable extent to the compaction of holocene strata

flux and fate of yangtze river sediment delivered to the east china sea numerous cores and dating show the yangtze river has accumulated about 1 16 x 10 12 t sediment in its delta plain and proximal subaqueous delta during holocene high resolution seismic profiling and coring in the southern east china sea during 2003 and 2004 cruises has revealed an elongated similar to 800 km distal subaqueous mud wedge extending from the yangtze river mouth southward off the zhejiang and fujian coasts into the taiwan strait overlying what appears to be a transgressive sand layer this distal clinoform thins offshore from similar to 40 in thickness between the 20 and 30 m water depth to 1 2 in between 60 and 90 m water depth corresponding to an across shelf distance of less than 100 km total volume of this distal mud wedge is about 4 5 x 10 11 m 3 equivalent to similar to 5 4 x 10 11 t of sediment most of the sediment in this mud wedge comes from the yangtze river with some input presumably coming from local smaller rivers thus the total yangtze derived sediments accumulated in its deltaic system and east china sea inner shelf have amounted to about 1 7 x 10 12 t preliminary analyses suggest this longshore and across shelf transported clinoform mainly formed in the past 7000 yrs after postglacial sea level reached its mid holocene highstand and after re intensification of the chinese longshore current system sedimentation accumulation apparently increased around 2000 yrs bp reflecting the evolution of the yangtze estuary and increased land erosion due to human activities such as fanning and deforestation the southward flowing china coastal current the northward flowing taiwan warm current and the kuroshio current appear to have played critical roles in transporting and trapping most of yangtze derived materials in the inner shelf and hence preventing the sediment escape into the deep ocean c 2006 elsevier b v all rights reserved

hydrodynamics and sedimentation induced by large scale coastal developments in the keum river estuary korea abstract the macro tidal keum river estuary located in the eastern yellow sea has been suffering siltation and morphological change since 1994 to understand the effects of the large scale coastal developments on the sedimentation processes in the estuary hydrodynamic and sedimentary data collected from 1985 to 2002 were analyzed and numerical experiments of hydrodynamics were performed the sedimentation rate in the estuary increased by a factor of 1 9 from 3 5 10 6 to 6 7 10 6 m 3 y 1 after the construction of a dam in the upper reaches of the estuary in 1994 large part of the estuary is veneered by the muddy sediments noticeably which were rarely found before dam construction since then siltation has concentrated in the upper estuary rather than the lower the upstream transport and accumulation of fine grained sediments is due to 1 the change to flood dominance in the main channel i e the relative intensification of flood current and the flood directed residual current and 2 the decrease in transport capacity in the upper estuary i e the marked decrease in current velocity which was induced by dam construction the former has resulted in the ebb dominance of the gaeya channel a distributary in the north of the main channel the tidal pumping of fine sediments was reinforced not by the freshwater saltwater interaction but by the residual tidal circulation the sediment fluxes observed in 2001 2002 demonstrate year round net inflow both at the entrance of the jetties and at the gaeya channel which implies that the sediments delivered by the keum river are entirely confined to the estuary incapable of escaping to the sea the net inward transport of fine sediments may accumulate pollutants adsorbed to or absorbed in the sediment grains in the estuary thus deteriorating the benthic environment gradually and the water quality eventually

partial anhysteretic remanence and its anisotropy applications and grainsize dependence the distribution of remanence coercivities in a rock sample can be obtained by differentiating alternating field af demagnetization curves of anhysteretic remanent magnetization arm however significant errors can be introduced by grain interactions and by the noise inherent in differentiation we have found that 1 this error can be significantly reduced by measuring partial arm s parm s and 2 parm patterns show a strong empirical correlation with grain size parm s are imparted by exposing a sample to a small direct magnetic field in the presence of a large decreasing af the direct field is switched on over a specified range of af s thus magnetizing a fraction of the magnetite grains in the corresponding coercivity range we have further found in both synthetic and natural sediments that measurement of the anisotropy of parm enables us to detect the preferred orientations of distinct subpopulations of magnetite particles related to the size and shape of the grains

magnetic fabrics and petrofabrics their orientation distributions and anisotropies abstract magnetic fabric and other petrofabric anisotropies may be described by second rank tensors represented by ellipsoids for a homogeneous petrofabric that is adequately sampled a stereoplot of the orientation distribution of the tensors principal axes maximum intermediate and minimum should show three orthogonal concentrations the concentrations form some combination of shapes from circular clusters through partial girdles to full girdles the concentrations elliptical eccentricities are constrained by the symmetry of the sample orientation distribution i e l l s l s etc as well as the individual sample anisotropies the mean orientations of principal axes must be orthogonal just as with individual sample tensors this requires tensor statistics for their calculation jelinek 1978 furthermore elliptical confidence cones for the means should parallel principal planes preserving overall orthorhombic symmetry however in practice sub orthorhombic symmetry may arise from unrepresentative sampling but it may also be a useful indicator of multiple or heterogeneous petrofabrics in the case of magnetic fabrics the wide range in average susceptibility values and variation in magnetic mineralogy permit small numbers of high susceptibility samples to deflect the orientation of the tensor mean away from the majority of samples normalizing the samples by their bulk susceptibility overcomes this but the orientation of high susceptibility outliers may signify an event or subfabric of importance that we should not discard therefore stereoplots of both normalized and non normalized orientation distributions should be compared preferably also identifying the outliers it is important to distinguish the shape of the orientation distribution ellipsoid from the shape of the individual magnetic fabric ellipsoids the qualitative l s nomenclature is best replaced by tj where tj 1 oblate tj 1 prolate jelinek 1981 invariably the orientation distribution is described by an ellipsoid whose shape is more spherical than that of the individual sample anisotropy ellipsoids because the latter have scattered orientations furthermore the shape of the orientation distribution ellipsoid need bear no relation to the shape of individual sample ellipsoid anisotropies the concepts are illustrated with 1119 measurements of anisotropy of magnetic susceptibility ams from seven areas and with 188 measurements of anisotropy of anhysteretic remanence aarm from two areas

does the reactive surface area of sandstone depend on water saturation the role of reactive transport in water film abstract to investigate how mineral water reactive surface area changes depending on water saturation flow through dissolution experiments were performed using a sandstone core at various water saturations fontainebleau sandstone with an open porosity of 6 3 consisting of 100 quartz was used the water saturation of the core was adjusted to 0 51 or 100 and at each saturation water was infiltrated into the core at a constant pressure the experimental results showed that the total amount of dissolved si did not change with decreasing water saturation it can be therefore concluded that virtually all of the mineral surfaces were wetted with water film and allowed the progression of dissolution i e the reactive surface area was not affected by water saturation despite the presence of air in the pores the results also suggested that the flushing rate of dissolved si from the interior of the water film to the exterior was fast enough to keep the si concentration in the film sufficiently lower than the equilibrium concentration of quartz we derived a reactive transport model describing dissolution and diffusion in water film the model shows that the solute concentration in a film is a function of the film thickness diffusion length dissolution rate of the mineral equilibrium concentration and roughness factor as for the fontainebleau sandstone film thicknesses of 7 18 nm and diffusion lengths of 300 600 m were estimated the reactive transport calculation confirmed that the overall dissolution rate of our sandstone sample was almost unaffected by water saturation owing to the high flushing efficiency of dissolved si in water film which agrees with the experimental result application of the model allows us to evaluate whether the reactive surface area and the dissolution rate change with water saturation for a given rock of interest

remanence stability and magnetic fabric development in synthetic shear zones deformed at 500 c shear experiments were performed on magnetite bearing calcite aggregates to examine magnetic fabric development and remanence stability in a deforming system using elevated temperature and pressure to encourage deformation by crystal plastic processes samples composed of 1 wt pseudo single domain magnetite 1 2 m in a calcite matrix were created with either strong or weak initial fabrics and deformed in coaxial simple shear to strains up to 1 5 at constant strain rates between 6 10 5 and 1 10 4 s 1 at 500 c and confining pressure of 300 mpa samples were given weak field thermal remanent magnetizations prior to deformation demagnetization of postdeformation remanence reveals that a primary remanent magnetization can withstand deformation at pressures and temperatures approximately equivalent to greenschist facies metamorphic conditions on laboratory time scales but this stability is found to depend on the character of the predeformation fabric the origin of secondary remanence components acquired during deformation is uncertain but is likely to partially result from thermal viscous remagnetization complete postdeformation remagnetization in initially anisotropic samples appears to involve a stress softening or piezoremanent magnetization mechanism postdeformation anisotropy measurements show progressive changes in magnetic fabric strength with strain in the absence of a strong initial magnetic anisotropy magnetic fabric intensity increases linearly as a function of strain however deformation that overprinted an existing fabric results in an apparent decrease of the initial anisotropy at low strains followed by rapid increases in magnetic fabric strength with increasing strain our results underscore the important role that initial fabric can play in determining the character of deformation fabrics

the multi decadal morphodynamic changes of the mouth bar in a mixed fluvial tidal estuarine channel abstract inner channel mouth bars imb are common and vital geomorphological structures in estuaries that can efficiently promote the progradation of a fluvial delta however these significant structures face serious interferences by natural and human forces this study mainly focuses on imb deposited in the mixed fluvial tidal dominated south passage sp of the changjiang estuary between 1959 and 2018 to reveal how multidecadal morphodynamic variability in a mouth bar responds to natural forcing and human interferences the results show that the volume of the imb in the sp increased from 1128 106 m3 in 1959 to 1636 106 m3 in 1989 and then decreased to 462 106 m3 in 2018 meanwhile the evolution of the imb could be divided into five stages the growing phase 1959 to 1979 which showed a v shape the partial adjustment phase 1999 2003 which showed a crest dent shape the stable phase which showed a flat shape 2004 2010 the partial adjustment phase 2011 2017 when jiangyanan shola inserted into the sp and finally evolved into a flat shape in 2018 fluvial water discharge and suspended sediment discharge ssd did not control the variation in the mouth bar enso events were normally responsible for not only the periodic variations in the landward slope and the water depth of the crest of the imb but also occasional extreme changes in the imb moreover local sandbar insertion sediment from the seaside induced by strong tidal power and intensified engineering projects resulted in the continual shrinkage of the mouth bar by depositing more sediment at the mouth bar our work implies that understanding and governing this imb will bring additional economic benefits to this fast developing society but the protection of this delicate estuarine geomorphology system should still receive great attention

archean regional transpression and paleomagnetism in northwestern ontario canada abstract the archean metamorphic rocks of the superior province of the canadian shield occur in lithologically defined belts or subprovinces the tectonically more stable interiors of belts possess consistent primary components of magnetic remanence in the case of the quetico belt these stable directions are tightly grouped about 005 55 with some minor dispersion and most were acquired during the cooling that followed syntectonic recrystallisation this study examines the directions of primary remanence components for rocks along the margins of the quetico belt within 4 km of the strongly deformed vertical ene trending boundaries the boundaries are known to have experienced dextral transpression involving penetrative single phase deformation which out lasted metamorphism within a few kilometres of the belt boundaries the primary remanence components are re distributed along a vertical ene trending great circle girdle which is nearly parallel to the plane of transpressive shear and regional schistosity it is suggested that the effects of transpression have mechanically deflected the components of primary remanence toward this plane

process based morphodynamic modeling of the yangtze estuary at a decadal timescale controls on estuarine evolution and future trends abstract understanding the decadal morphodynamic evolution of estuaries and deltas and their controls is of vital importance regarding management for estuarine function and sustainable development this work addresses this issue by applying a process based model system delft3d to hindcast and then forecast the morphodynamic evolution of the yangtze estuary at a decadal timescale forced by the river and tides the model considers sand mud mixture and the variations of river water discharge and sediment discharge the morphodynamic model is validated against three periods i e an accretion period 1958 1978 an erosion period 1986 1997 and a recent accretion period with human activities 2002 2010 model results show good performance with respect to spatial erosion and deposition patterns sediment volume changes and hypsometry curves the model reveals quite different behaviors for mud transport between the dry and wet seasons which is subject to the prescription of river boundary conditions and bed composition we define six scenarios to project evolution to the year 2030 under decreased river inputs and increased relative sea level the simulations reveal that overwhelming amount of erosion will likely occur in the inner and mouth bar area of the estuary particularly the mouth zone will shift from net deposition before 2010 to net erosion by 2030 mainly because of decreasing sediment supply changes in water discharge have minor effects on the projected trend net erosion will be considerable when the sediment supply is extremely low 100 mt yr 1 due to the abundance of erodible modern sediment in the yangtze estuary erosion within the mouth bar area may be unexpected including the deepening of the tidal inlet at east chongming mudflat and the formation of a flood channel on the seaward side of jiuduansha shoal overall the model results provide valuable information for sustainable delta management under changing conditions for both the yangtze system and other similar estuaries and deltas with diminishing sediment supplies

decline in suspended sediment concentration delivered by the changjiang yangtze river into the east china sea between 1956 and 2013 abstract the temporal evolution of suspended sediment concentration ssc in a river debouching into the ocean provides vital insights into erosion processes in the watershed and dictates the evolution of the inner continental shelf while the delivery of sediment from rivers to the ocean has received special attention in the recent past few studies focused on the variability and dynamics of river ssc especially in the changjiang yangtze river china the longest river in asia here variations in ssc delivered by the changjiang river to the east china sea and possible causes of its variability were detected based on a long term time series of daily ssc and monthly water discharge measured at the datong gauging station the ssc data are further compared to a hydrological analysis of yearly precipitation covering the entire catchment the results indicate the presence of a decline in ssc in the period 1956 2013 which can be divided into three phases i high ssc 0 69 kg m3 in the wet season and low ssc 0 2 kg m3 in the dry season from 1956 to 1970 ii relative high ssc 0 58 kg m3 in the wet season and low ssc 0 15 kg m3 in the dry season from 1971 to 2002 and iii low ssc 0 19 kg m3 in the wet season and very low ssc 0 09 kg m3 in the dry season after 2002 these three periods have a mean yearly ssc values of 0 62 0 42 and 0 18 kg m3 respectively compared with 1956 1970 the slope of the rating curve between ssc and water discharge decreased respectively by 2 and 30 during the period 1971 2002 and 2002 2013 soil erosion dam construction and banks reinforcement along the changjiang river are the main causes of ssc variations fluctuations in water discharge are also controlling the ssc long term variations specifically from 1956 to 1970 the effect of soil erosion overrules that of dam impoundment which is likely responsible for the high ssc during the period 1970 2002 the influence of dam impoundment increases while that of soil erosion decreases which together produce a small reduction in ssc since 2002 the impact of soil erosion further decreases and large scale sediment trapping behind the three gorges dam is responsible for the occurrence of extremely low ssc the results presented herein for the changjiang river can inform a better management strategy of sediment resources and water quality for both the river and the coast our conclusions can be well applied to other rivers discharging in the ocean subject to similar human activities

bathymetric evolution of the mersey estuary uk 1906 1997 causes and effects this paper examines how a continuous series of measurements and model studies have developed our understanding of the evolving interactions between tidal dynamics sediment regime and bathymetry of the mersey estuary among the most intensively monitored worldwide this includes familiar assessments of the capabilities of fine resolution 3 d models but is here extended to examine historical changes in tides sediments and estuarine bathymetries a century of bathymetric surveys indicates a net loss of estuarine volume of about 0 1 or 1 million cubic metres per year in contrast sea level rise of 1 2 mm a 1 represents only a 0 02 annual increase this relative stability persists in a highly dynamic regime with suspended sediment concentrations exceeding 2000 mg l 1 and spring tide fluxes of order 200 000 t detailed analyses of the bathymetric sequences indicate most significant changes occur in the upper estuary and in inter tidal zones a long period up to 63 years of tidal elevation records in the lower estuary shows almost no changes to the predominant m2 and s2 constituents the 3 d numerical model accurately reproduces both these elevation constituents and corresponding cross sectional distributions of currents simulation accuracies reduce upstream due to cumulative errors associated with relatively unstable bathymetries and increasing sensitivities to the bed stress coefficients impacts from increases in river flows of up to two or three times the long term mean value can only be detected in the upper estuary a detailed examination of sediment fluxes utilised a numerical simulation of conditions over a cross section in the narrows the 10 km by 1 5 km prismatic entrance channel the limited mobility of coarse sediments was contrasted with the near continuously suspended nature of the finest clay a sensible match between the net sedimentation rates indicated by the model and the net observed deposition rate was found to occur for silty sand corresponding directly with evidence from dredging records and from direct sampling while the model indicated sedimentation rates might increase by up to a factor of ten for much finer particles such occurrences are likely to be restricted by the limited availability of such material in the adjacent coastal zone the controlling mechanism for this import of fine sediments is via tidal pumping the nature of which depends critically on the phase lead of tidal currents relative to elevation however since this phase lead is determined by the large scale tidal energy balance of the estuary the conclusion is that stability of the overall tidal dynamics the associated sediment regime and bathymetry are likely to co exist and evolve slowly as indicated by the observed annual decrease in net volume suggestions are included for monitoring strategies in other estuaries to provide insight into such dynamics sediment bathymetry inter relationships

strain anisotropy of anhysteretic remanence and anisotropy of magnetic susceptibility in a slaty tuff finite strain data for the borrowdale slaty tuffs compare variably with the anisotropy of magnetic susceptibility ams and anisotropy of anhysteretic remanent magnetization aarm finite strain determined from lapilli rims shows that slaty cleavage was formed by coaxial flattening with x y z in the ratio 1 74 1 21 and 0 48 aarm was measured in different coercivity windows to isolate contributions from magnetite of different grain sizes a 0 3 mt for multi domain md b 3 15 mt for pseudo single domain psd and c 15 60 mt for single domain sd ams combines petrofabric contributions from silicates as well as magnetite magnetite grains may grow recrystalize or rearrange domains after or during metamorphism and postdate or overlap with the silicate s fabric evolution ams foliation defined by paramagnetic chlorites is parallel to slaty cleavage aarm foliation for sd magnetites is offset clockwise from ams foliation which may reflect late crystallization or domain rearrangement of magnetites in response to a latter noncoaxial increment ams fabric shape consistently corresponds to strain ellipsoids and indicates that the strain induced ams fabric is susceptible to the change of oblateness rather than strain intensity furthermore investigation of the different aarm subfabrics and finite strain shows that only sd magnetite s aarm correlates with finite strain and weakly at that 2001 elsevier science b v all rights reserved

drowning of the mississippi delta due to insufficient sediment supply and global sea level rise global sea level rise reduced sediment supply and subsidence threaten the stability of the mississippi delta calculations of riverine sediment load and storage indicate that 10 000 13 500 km2 of the delta could be submerged by ad 2100

tectonics of the akamas and mamonia ophiolites western cyprus magnetic petrofabrics and paleomagnetism abstract the akamas ophiolite is shown to be a distal off axis extension of the main outcrop of cretaceous ophiolite in the troodos complex of cyprus mantle sequence harzburgites of both ophiolites share similarly oriented mantle flow fabrics and the same tertiary magnetizations acquired during exhumation however compared with the troodos mantle sequence rocks the akamas ferromagnetic mineralogy is more oxidized and remanences with lower blocking temperatures were acquired chemically paleopoles calculated from published vectors and our own new data define an apparent polar wander path apwp for the troodos microplate the apwp shows that between 88 and 50 ma the troodos microplate was equatorial and the vertical axis for its 60 anticlockwise rotation was located within the microplate subsequently the microplate drifted northward to 34 n with minor anticlockwise rotation at a reduced rate that requires microplate rotation about a vertical axis located to the west of cyprus in the last 50 ma the allochthonous triassic mamonia terrane docked with the cretaceous troodos terrane in sw cyprus within it disrupted tectonized ophiolite has been regarded as part of a triassic ocean floor or as sheared fragments of cretaceous troodos ophiolite incorporated into the mamonia terrane when it docked with the troodos terrane whatever their provenance their paleomagnetic signals postdate their penetrative deformation and metamorphism and their paleopoles may still be used to track their post strain motion our calculations of paleopoles from published vectors for the mamonia terrane smear along an extension of the apwp for the troodos microplate that is moreover concentric with the troodos microplate this suggests that the paleopole dispersion of the triassic mamonia rocks and their post magnetization disruption occurred during their accretion onto the anticlockwise spinning troodos microplate

do reduction spots predate finite strain a magnetic diagnosis of cambrian slates in north wales abstract the purple cambrian slates of north wales contain green colored irregular patches drawn out along cleavage and the more familiar ellipsoidal reduction spots that are parallel to cleavage because parallelism of pre strain ellipsoids could only be produced by extremely high strain we reject the hypothesis that these are strain markers here we use magnetic methods to resolve this argument the magnetic analysis reveals that the magnetic fabric of purple slate differs from the green variety of the slate only in the oxidation state and indicates that the reduction process postdates cleavage this suggests that the shape of reduction spots reflects the anisotropy of diffusion during reduction not finite strain and alignment of an initially ellipsoidal object in the slates

new and revisited paleomagnetic data from permian triassic red beds two kinematic domains in the west central pyrenees abstract new paleomagnetic results of permian triassic red beds from bielsa aure and somport anayet sectors in the pyrenean axial zone are presented and combined with revisited and reviewed paleomagnetic data from the west central pyrenees the paleomagnetic data from the red beds vary between different sectors that share similar structural position i e whilst all sectors share the existence of a characteristic prefolding component a cenozoic postfolding component is found only in one area but not in other areas with similar structural position and kinematics previous paleomagnetic data to the west of the studied zone reveal a pre turonian remagnetization component but this secondary component is not found in an area that shares a similar structural position aure this variability suggests that the paleomagnetic behavior is the result of a series of factors related to the particular tectonic history of the region sedimentation burial and deformation during basin inversion and therefore paleomagnetic data demands careful assessment in order to unravel the kinematics of areas with equivalent structural positions in orogens however important kinematic implications that hold in the pyrenees can be inferred from the restoration of the permian triassic characteristic magnetizations to positions previous to the paleomagnetic rotations recorded by cretaceous or cenozoic paleomagnetic data the restoration reveals on one hand the lack of large rotations in the south pyrenenan zone except in the nogueras area according to bates 1989 and on the other hand the contrasting rotations recorded to the west of the studied zone in the paleozoic basque massifs pbm and the south pyrenean zone indicating the existence of two different tectonic domains in the west central sector of the pyrenees the strong clockwise rotations postdating the early cretaceous remagnetization that are recorded in the pbm and in the north pyreneean zone suggest a late dextral shear deformation affecting areas near the north pyrenean fault zone

secular bathymetric variations of the north channel in the changjiang yangtze estuary china 1880 2013 causes and effects abstract as the interface between the fluvial upland system and the open coast global estuaries are facing serious challenges owing to various anthropogenic activities especially to the changjiang estuary since the establishment of the three gorges dam tgd currently the world s largest hydraulic structure and certain other local hydraulic engineering structures the changjiang estuary has experienced severe bathymetric variations it is urgent to analyze the estuarine morphological response to the basin wide disturbance to enable a better management of estuarine environments north channel nc the largest anabranched estuary in the changjiang estuary is the focus of this study based on the analysis of bathymetric data between 1880 and 2013 and related hydrological data we developed the first study on the centennial bathymetric variations of the nc it is found that the bathymetric changes of nc include two main modes with the first mode representing 64 of the nc variability which indicates observable deposition in the mouth bar and its outer side area lower reach the second mode representing 11 of the nc variability which further demonstrates channel deepening along the inner side of the mouth bar upper reach during 1970 2013 further recent erosion observed along the inner side of the mouth bar is caused by riverine sediment decrease especially in relation to tgd induced sediment trapping since 2003 while the deposition along the lower reach since 2003 can be explained by the landward sediment transport because of flood tide force strengthen under the joint action of tgd induced seasonal flood discharge decrease and land reclamation induced lower reach narrowing generally the upper and lower nc reach are respectively dominated by fluvial and tidal discharge however episodic extreme floods can completely alter the channel morphology by smoothing the entire channel the results presented herein for the nc enrich our understanding of bathymetric variations of the changjiang estuary in response to human activities which can be well applied to other estuaries subject to similar interferences

morphological evolution of the south passage in the changjiang yangtze river estuary china abstract estuarine morphology of the world s major large rivers have experienced great changes due to intensive anthropogenic activities and natural forcings especially in the changjiang estuary located at the end of the longest river in asia this study focuses on morphological changes of the south passage sp which is one of the 4 channels in the branching estuary at the mouth of the changjiang yangtze river china a multivariate analysis technique of empirical orthogonal eigen function eof method was used to examine the major modes of change in the long term over 26 years water depth data the results show that the morphological changes at the sp could be divided into two stages between 1987 and 1997 the sp had a single stable channel with closure of a cross channel between 1997 and 2012 sp displayed southeastward elongation of a spit into the main channel and westward shoal incision by a cross channel the opening of the sp developed a two channel morphology which stabilized and showed infilling during 2003 2012 the average deposition rate was 10 cm yr in the past 30 years the most dominant morphological changes of sp included the deposition around the upstream opening of the channel the second most important pattern of morphological change was related to the downstream elongation retreat and lateral migration of the spit of the jiangyanan shoal which resulted in the two channel configuration of the sp additionally these morphological changes were not triggered by the decline of the distal sediment source from the upstream but due to the input of proximal sources of the shoal at the upstream opening of the sp and spill over sediment from the north passage via a short cut channel

rapid human induced siltation of the macro tidal ord river estuary western australia field studies on the sediment dynamics of the two arms of cambridge gulf tropical western australia were undertaken the system is macro tidal with 8 m tides the west arm is the estuary of the durack and pentecost rivers which are largely untouched by human activities the east arm is the estuary of the ord river affected by land clearing which started 100 years ago and by two river dams constructed 30 years ago prior to damming of the ord river the natural flow in all rivers was highly seasonal characterized by small at times negligible flow during the dry season which lasts eight months and occasional river floods during the wet season which lasts four months the river flow has been regulated in the east arm as a result of damming this resulted in suppressing large river floods the salinity intrusion length has decreased by about 50 in the east arm following river damming the east arm has silted measurably over the last 30 years with the stream cross sectional area decreasing by about 50 field and numerical studies suggest that this is due to the dam induced suppression of large river floods which has in turn allowed a greater amount of tidal pumping of sediment into the east arm from cambridge gulf since tidal pumping is increasing as the system is silting the east arm appears to now be geomorphologically unstable as a result of human activities numerical studies suggest it may take as little as 100 years for the ord river to reach a new equilibrium modelling suggests that this equilibrium may be characterized by a salinity intrusion length half that before damming a channel width and depth reduced by 70 and a much stronger tidal asymmetry characterized by an increasing size of the tidal bore the west arm appears to be at equilibrium since there has been no net loss or gain of sediment for the last 111 years tidal dynamics and river floods appear responsible for self scouring this channel

analysis of anisotropy of magnetic susceptibility in iron oolitic beds a potential tool for paleocurrent identification a combined sedimentological shape preferred orientation and anisotropy of magnetic susceptibility ams analysis has been performed at the arroyofrio bed callovian oxfordian boundary level in the locality of moneva iberian range ne spain the arroyofrio bed is a widespread iron ooid limestone interval forming a condensed sequence the present study has focused on the analysis of the potential presence of a preferred ooid orientation at the arroyofrio bed the obtained data show that ooids were originally ellipsoidal and had an imbricate disposition with respect to the bedding lamination surface the main ooid orientation within the bedding plane shows a nne ssw trend results of ams analyses show a magnetic foliation parallel or slightly imbricated with respect to bedding and magnetic lineation parallel to the main ooid orientation magnetic mineralogy of studied samples shows that ams is mainly controlled by magnetite with minor contributions of hematite and paramagnetic minerals that can reach contributions of 35 the analyzed ooids show axial ratios between 1 4 and 2 8 intrinsic anisotropy while the anisotropy of their distribution shows lower anisotropies e g rs 1 15 or very low values of the anisotropic magnetic parameters e g p 1 01 sedimentary texture matrix features bioturbation and fossil content influenced both ooid main orientation and the magnetic fabric magnetic lineation and main orientation of long ooid axes are transverse to the inferred coastline in the studied area and parallel to the expected paleocurrent direction with respect to the ejulve maestrazgo paleogeographic high the direct correlation between ams magnetic lineation and the ooid analysis permits to demonstrate that the paleocurrent imprint can be recorded by means of ams despite the highly ferromagnetic context fabric and at coarse deposits obtained results support the interest and reliability of ams to unravel paleocurrent imprints for paleogeographic reconstructions

the anisotropy of magnetic susceptibility ams in low grade cleaved pelitic rocks influence of cleavage bedding angle and type and relative orientation of magnetic carriers

specific processes during in situ infiltration into a sandy soil with low level water repellency summary despite growing knowledge about water repellent soils it is not well investigated how soil water repellency swr of a lower level influences the in situ water infiltration into soils hence we investigated a sandy soil where we found subcritical water repellency and unexpected stable persistent contact angles cas in the subsoil characterized by ca measurements in the laboratory to characterize the influence of this persistence on in situ water infiltration a ponded tracer infiltration experiment was carried out during the infiltration hydraulic sensors revealed a slight saturation at the wetting front which is a sign for unstable flow the excavated dye stained infiltration zone was conical and its lateral extent decreased with increasing depth showing characteristics of a macro finger we suggest the subsoil to exhibit a strong hysteretic water retention characteristic governing the infiltration process but we could not verify this by standard laboratory measurements as strongly persistent swr prevented the fast wetting of the soil samples close to saturation the persistence of swr led to a wetting period of soil samples of at least 56 days to overcome swr and reaching an equilibrium state there are three major conclusions of this study 1 in contrast to many other studies we found persistent swr also in the subsoil and not only in the humic topsoil 2 the shape of the wetting front is contrary to common expectations for homogeneous sandy soils and 3 the wettability characteristics found might also be relevant for assessing infiltration dynamics at other sites regarding the fact that those observations are not obvious

fluvial and marine controls on combined subaerial and subaqueous delta progradation morphodynamic modeling of compound clinoform development 1 fluviodeltaic systems commonly display a compound clinoform geometry that consists of a subaerial subaqueous delta couplet the extent of subaqueous delta development varies significantly and in modern systems is a function of fluvial input and basin hydrodynamics we present a model of fluviodeltaic progradation in which the repeated occurrence of characteristic terrestrial floods and large coastal storms drives fluvial and shallow marine morphodynamics respectively we couple fluvial and shallow marine sediment dynamics via the surf zone which we collapse to a shock condition and treat as a moving boundary with steady sediment supply and sea level and simple basin geometry our model naturally develops prograding deltas with compound clinoform geometries the subaerial delta grows via fluvial aggradation and shoreface progradation whereas the subaqueous delta expands through foreset progradation with only minor topset aggradation the interplay of fluvial input with the wave current field controls the basic partitioning of sediment between subaerial and subaqueous deltas and by extension the compound clinoform geometry increasing the frequency or magnitude of coastal storms decreasing flood frequency or discharge and reducing grain size all increase the fraction of sediment delivered to the shallow marine environment and the extent of subaqueous delta progradation relative to subaerial delta development our model which emphasizes the intrinsic coupling of fluvial and shallow marine sediment dynamics and downplays the importance of allogenic fluctuations can explain many of the first order morphologic features of natural delta systems including significant lateral separation of the shoreline and clinoform rollover and differing rates of subaerial and subaqueous delta progradation

long term morphological change and its causes in the mersey estuary nw england changes in the morphology of the mersey estuary and their possible causes have been investigated using historical trend analysis and expert geomorphological assessment historical bathymetric charts were digitised and analysed within a gis to provide quantitative estimates of changes in areas and sediment volumes above and below selected elevation planes the results show that the estuary experienced major changes over the last 150 years notably between the late 19th century and ca 1950 an analysis of data relating to possible natural and human factors which could have influenced these changes suggests that training wall construction and dredging in the outer estuary and liverpool bay was the most significant factor contributing to change during this period these activities modified the hydrodynamic and sediment transport regime in a way which enhanced an existing natural tendency for movement of sediment from liverpool bay and the outer estuary into the inner estuary changes in other factors including sea level tidal range wind wave climate freshwater flow and embanking land reclamation were of relatively minor importance between 1950 and 1977 the rate of sediment accumulation in the inner estuary declined as the estuary approached a new condition of dynamic equilibrium and since 1977 there has been a slight net loss of sediment under these conditions the changes in natural forcing factors such as sea level and storminess are likely to have a relatively greater effect on the estuary than in the past

the effect of non passive clast behaviour in the estimation of finite strain in sedimentary rocks abstract existing methodologies that use ellipsoidal objects for the analysis of geological strain typically assume that these objects acted passively during deformation this assumption when not valid can lead to significant underestimates of strain in rocks deformed under low grade conditions in orogenic forelands this is especially true when clastic sedimentary rocks are utilized to measure strain the competency contrast between clasts and matrix possibly leading to marked non passive behaviour the systematic nature of this finite strain underestimation may allow for a correction of strain estimates when this type of behaviour is evident

decadal morphological response of an ebb tidal delta and down drift beach to artificial breaching and inlet stabilisation abstract the morphodynamic response of a mixed energy ebb tidal delta guadiana estuary southern portugal and its down drift barrier island canela island to channel relocation and stabilisation by jetties is examined using a series of sequential bathymetric maps and vertical aerial photographs spanning five decades morphological analysis indicates that the ebb delta is in an immature state characterised by weak sediment bypassing landward migrating shoals on the swash platform have been produced by the jetty induced artificial bank breaching and by the collapse of the eastern portion of the delta the welding of these shoals has largely controlled the evolution of the coast with local accretion and erosion lasting for years and large amounts of regional accretion occurring over decades due to sand accumulation against jetties located further down drift these observations provide insights into the potential response of a coast to very large locally concentrated sand nourishment in the form of shoals the main effects of the jetties on the coast are observed at the centre of canela island with the production of an erosion hot spot associated with a temporally persistent and divergent longshore transport providing sand to the adjacent areas significant accretion is anticipated for the next decade along the entire island due to the ongoing attachment of the presently observed shoals after the depletion of this sediment source and in the context of weak sediment bypassing the most severe down drift erosion induced by the jetties is predicted to occur some decades after their construction this study demonstrates that the geomorphic response of an ebb tidal delta to jetty construction must be considered at multiple temporal and spatial scales when assessing the impacts of jetties on the down drift coast

finite strain patterns and their significance in permian rocks of the alpes maritimes france abstract more finite strain data has been obtained from autochthonous permian mudstones of the alpes maritimes s e france these new data were computed from field measurements of green spots on all available sections deformed mudcracks and from the quantitative correlation between magnetic susceptibility anisotropy and finite strain in these rocks previously published finite strain data and the new results are presented on a series of structural maps and cross sections for the dome de barrot the tinee and vionene region and the roya region as in previous studies difficulties arise in explaining the apparently variable extension parallel with the 100 subhorizontal bedding cleavage intersection either this is real or there were large volume changes during the tectonic deformation study of quartz fibres developed in deformed mudcracks in the tinee valley suggest that early in the tectonic history incremental stretching directions were parallel with the bedding cleavage intersection while later they were down dip in the 100 trending cleavage since these permian rocks have remained stuck to the argentera basement they also record displacements and deformations in the basement the early 100 subhorizontal stretching is consistent with nw se dextral strike slip basement faulting while later down dip stretching in the cleavage is consistent with contraction faults in the basement this information and new palaeomagnetic data on the same samples are combined with recent geophysical evidence and regional tectonic studies to provide a new precision to the tectonic history of this part of the western alpine external zone

long term morphological change in the ribble estuary northwest england morphological change in the ribble estuary northwest england has been studied using bathymetric charts topographical surveys and remote sensing data a sediment budget has been prepared from the analysis of these data the results reveal a net accretional trend over the last 150 years the main channels experienced major infilling sediment also accumulated in higher parts of the intertidal zone salt marshes and sand banks while the sediment volume in the lower intertidal zone remained essentially the same there were both zones of net erosion and deposition in the outer estuary with a small net gain in subtidal sediment volume infilling associated with major morphological change was accelerated in the nineteenth century and early twentieth century principally as a result of human activities the triggering factors for increased sedimentation were embankment construction and reclamation after 1810 which progressively reduced the intertidal area tidal prism and current velocities within the estuary additionally construction of a trained channel between 1847 and 1910 to secure navigation and maintenance of this channel by dredging concentrated the ebb flow in this overdeepened channel and reduced periodic scour over the sand banks on both sides enhancing sedimentation thus the effects of human activities have outstripped those of changes in natural forcing factors on the morphological development in the area

treated wastewater effects on water repellency and soil hydraulic properties of soil aquifer treatment infiltration basins summary irrigation with treated wastewater tww has been reported to induce low to moderate hydrophobicity in soils of different texture with or without vegetation cover additional potential sites for adverse effects of tww are infiltration basins where tww undergoes tertiary treatment known as soil aquifer treatment sat the annual organic matter om loads in sat are a hundred fold higher than those applied in irrigation with tww therefore we initially presumed that in the sandy soils of sat infiltration basins hydrophobicity would be expressed to a higher extent and would further affect the hydraulic properties of these soils this hypothesis was tested in the dan region wastewater reclamation project tel aviv israel in terms of water drop penetration time wdpt test the results obtained exhibited similar hydrophobicity levels 0 wdpt 238 s to those obtained in the tww irrigated fields and in a similar manner soil hydrophobicity was only exhibited in the surface soil layer it is suggested that the low to moderate hydrophobicity obtained under tww irrigation and recharge into the sat basins may primarily stem from the drying and wetting cycle regimes employed under these conditions hydrophobic compounds which may impart hydrophobicity to the soil particles are likely to detach and dissolve into the soil solution at the subsequent irrigation or recharge event furthermore the frequent displacement of the resident tww derived om by repeatedly flooding events prevents maturation and humification of the resident om further investigations on the hydraulic properties of the basin soils were conducted in conjunction with the solid liquid contact angle and the surface tension l of the soil solution the results obtained imply that the dependence of the hydraulic properties on and or l can be attributed to the hydrophobic nature of both the solid and dissolved om originating from the recharged tww

long term morphodynamic evolution and the equilibrium mechanism of a flood channel in the yangtze estuary china the stability of flood channels has attracted considerable attention because of their complicated interactions with the prevailing hydrodynamics and importance in ship navigation this research examines long term morphodynamic evolution in the yangtze estuary from 1861 to 2002 and the equilibrium mechanism of the xinqiao channel in the yangtze estuary by digitizing 15 selected maritime charts and calculating the volume of the channel although the total period of channel development is much longer than the historical data used in this paper three stages are identified during the study period the first embryonic stage 66 years the second formation stage 33 years and the third equilibrium stage 45 years variations in coastline location channel volume and hydrodynamics in the channel during the three stages indicate that the channel equilibrium was reached and maintained when the channel direction was aligned with the direction of offshore tidal wave propagation variations in river and sediment discharges affect erosion and deposition in the channel and thus channel geometry however future reduction in sediment supply by 10 33 due to the ongoing river engineering projects would increase the volume of the xinqiao channel only by 1 3 it seems unlikely that the above change in sediment discharge will disrupt the equilibrium of the xinqiao channel

prediction of fingering in porous media immiscible displacement involving two fluids in a porous medium can be unstable and fingered under certain conditions in this paper the original linear instability criterion of chuoke et al 1959 is generalized considering wettability of two immiscible fluids to the porous medium this is then used to predict 24 specific flow and porous medium conditions for the onset of wetting front instability in the subsurface wetting front instability is shown to be a function of the driving fluid wettability to the medium differences in density and viscosity of the fluids the magnitude of the interfacial tension and the direction of flow with respect to gravity scenarios of water and nonaqueous phase liquid infiltration into the vadose zone are examined to predict preferential flow and contamination of groundwater the mechanisms of finger formation propagation and persistence in the vadose zone are reviewed and the existing equations for calculating the size the number and velocity of fingers are simplified for field applications the analyses indicate that fingers initiate and propagate according to spatial and temporal distribution of the dynamic breakthrough water or air entry pressures in the porous medium the predicted finger size and velocity are in close agreement with the experimental results

shoreline variability via empirical orthogonal function analysis part i temporal and spatial characteristics empirical orthogonal functions eofs or principal components were used to extract the significant modes of shoreline variability from several data sets collected at three very different locations although eofs have proven to be a valuable tool in the analysis of nearshore data most applications have focused on the ability of the technique to describe cross shore or profile variability here however eofs were used to help identify the dominant modes of longshore shoreline variability at duck north carolina the gold coast australia and at several locations within the columbia river littoral cell in the u s pacific northwest in part one of this analysis characteristic patterns of shoreline variability identified by the eof analysis are described in detail at each site the dominant modes consisting of the first four eigenfunctions were found to describe nearly 95 of the total shoreline variability at both duck and the gold coast several interesting longshore periodic features suggestive of sand waves were identified while boundary effects related to natural headlands and navigational structures entrances dominated the pacific northwest data sets

on the origin of the magnetic fabric in purple cambrian slates of north wales anisotropy of magnetic susceptibility ams in samples of cambrian slate from penrhynn wales is surprisingly weak maximum minimum 1 1 to 1 2 in view of their large finite strain x z 3 5 to 4 5 and their hematite dominated magnetic mineralogy several lines of evidence suggest that this is a result of the presence of two or more generations of hematite sem observations show a somewhat bimodal size distribution of hematite particles with modal diameters of approximately 1 3 m and 10 20 m the larger grains tend to have ragged subequant shapes and contain titaniferous laminae they are probably of igneous detrital origin the finer grains have crystallographically controlled shapes are ti free and are probably authigenic or metamorphic initially chemical leaching of deeply incised solid specimens preferentially removes the more soluble particles and results in significant changes in ams further leaching attacks the remaining grains on exposed surfaces and the ams ellipsoid reverts to its initial shape isothermal remanent magnetization irm is significantly more anisotropic than low field susceptibility the variation of irm anisotropy with applied field indicates relatively strong fabric development in the fine grained hematite but weak fabric in the coarser fraction grain boundaries were digitized from sem photos in order to calculate flinn fabric ratios by the rf method the x z ratios thus obtained for quartz and fine hematite grains are 3 14 and 1 70 respectively it is therefore clear that the hematite fabric does not reflect the total finite strain

from the highest to the deepest the gaoping river gaoping submarine canyon dispersal system abstract there are many different source to sink dispersal systems around the world and the gaoping river gpr gaoping submarine canyon gpsc provides an example especially as a canyon captured system the gpr a small mountainous river having an average gradient of 1 150 and the gpsc which links the river catchment to the deep sea basin represent two major topographic features around sw taiwan together they constitute a terrestrial to marine dispersal system that has an overriding impact on the source to sink transport of sediment in this region the gpsc extents from the mouth of the gpr through the shelf and slope and into the northeastern manila trench a distance of about 260 km it is a major conduit for the transport of terrestrial sediment and carbon to the south china sea and the landward transport of particles of marine and biological origin in the gpsc the dominant mode of suspended sediment transport is tidal oscillations and the net direction is up canyon in contrast sediment transport associated with episodic gravity driven events is down canyon the steady sedimentation of the tidal regime results in hemipelagic mud across the canyon floor whereas the gravity driven hyperpycnal regime causes turbidite erosion and deposition along the canyon thalweg typhoon induced river floods often lead to hyperpycnal plumes at the river mouth which directly and indirectly ignite hyperpycnal turbidity currents in the canyon forming an effective agent for transporting large amounts of terrestrial organic material modern and fossil carbon to the south china sea basin therefore the gpr gpsc represents a source to sink system in which terrestrial sediment in a mountainous catchment is promptly removed and transported to the deep sea by episodic gravity flows this is also a pathway by which modern terrestrial organic carbon is quickly and effectively delivered to the deep sea

the correlation of magnetic anisotropy with strain in the chelmsford formation of the sudbury basin ontario abstract a quantitative correlation has been established between finite strain and the anisotropy of magnetic susceptibility ams in sandstones of the precambrian chelmsford formation of the sudbury basin ontario investigations of the progressive acquisition of isothermal remanent magnetization and its destruction with reverse field and thermal demagnetization as well as microscopic examination of polished thin sections show that both pyrrhotite and magnetite are present in the sandstone measurements of the ams have been carried out at 16 sites distributed throughout the chelmsford formation outcrop considerable variation in the shapes of the magnetic susceptibility ellipsoids axes k max k int k min exists within each site with the k max and k int axes contained in the cleavage planes where developed the magnitudes of the magnetic susceptibility axes have been quantitatively correlated with strain measurements carried out by clendenen et al this issue two different strain to magnetics correlations have been carried out between the site mean strain determined using deformed concretions and the mean values of the ams at each site and between individual specimen strain values determined at the microscopic scale and the individual specimen ams in both cases separate correlations were made between strain long intermediate and short axes and their corresponding magnetic k max k int and k min axes at 10 sites the site mean strain values were derived from strain analysis of the concretions and at an additional 6 sites the site mean strain values were derived from the ams to strain correlation 527 individual cores were converted to equivalent strain values using the ams structural correlation of individual specimens this study extends the use of ams methods to include strain determination in sandstones and provides an order of magnitude increase in the available number of such data for further structural analysis

a thirteen year record of bathymetric changes in the north passage changjiang yangtze estuary article i nfo the mouths of major rivers in the world have always been important waterways and as a result subject to significant human intervention therefore it is necessary to understand the coupling of natural processes and human intervention in the sediment movement and deposition to determine long term morphodynamic evolution in the mouth regions of major rivers a multivariate technique was used to analyze high resolution bathymetric data from the north passage of changjiang yangtze river which is the vital shipping channel in the mouth region and for the entire changjiang waterway our findings show that there are two modes of bathymetric changes the first mode represents 85 of the variability which includes the deposition in the peripheral groin fields along the shipping channel and deepening of the shipping channel which is primarily due to the channel maintenance the second mode represents 6 of the variability of the river mouth shoal seaward migration and size reduction attributable to the declining sediment discharge of the changjiang

use of continuous turbidity sensor in the prediction of fine sediment transport in the turbidity maximum of the trent estuary uk results from continuous monitoring of turbidity and water level at burringham on the tidal river trent uk are presented for the period 18 may 1997 to 9 february 1998 these measurements together with detailed readings of velocity and suspended sediment concentration over an individual tidal cycle near the opposite bank at derrythorpe help to describe the mechanisms and behaviour of the turbidity maximum tm it is demonstrated that there is a distinct pattern of fine sediment movement that reflects a predictable system response to changing hydraulic features it is shown that the tm in this system is highly mobile and its location depends on antecedent fresh water flow and tidal range approximate representative flood and ebb tide suspended sediment concentrations of up to 13 g l over this nine month period have been derived from the data and plotted against fresh water flow and tidal range in order to show the relationship between these parameters three semi empirical polynomial regression models have been tested for goodness of fit against available data it was found that a partitioning approach whereby data are grouped into different categories depending on antecedent fresh water flow yielded the lowest standard error for the period analysed analysis of detailed observations of suspended sediment concentration and velocity measured over an individual tidal cycle also help to elucidate the mechanism of tidal pumping within this system these results also help to give an estimate of the relative magnitude of suspended sediment fluxes during typical low fresh water flow conditions it is estimated that for low fresh water flow conditions a typical spring tide can mobilise at least an order of magnitude more sediment than a neap tide

late proterozoic reconstructions of north west scotland and central canada magnetic fabrics paleomagnetism and tectonics red beds dominate the stoer group and the unconformably overlying torridon group having accumulated between 1400 and 1000 ma in a rift of the hebridean foreland the sequences were weakly strained and shortened e w and each underwent successive diagenetic changes which altered their magnetic properties and caused their different characteristic post depositional magnetizations anisotropy of magnetic susceptibility ams reveals an n s vertical tectonic foliation superimposed on the bedding planar ams sub fabric the tectonic ams sub fabric was isolated by comparing normalized and non normalized mean tensors of multiple specimens the n s vertical ams tectonic foliation postdates warps of bedding thus the high susceptibility minerals including those carrying palaeomagnetic signals re oriented or recrystallized after deposition and diagenesis thus characteristic remanence vectors chrm were acquired long after deposition first in the stoer group then in the torridon chrms were isolated for 143 stoer specimens and 94 torridon specimens using two cycles of low temperature demagnetization followed by at least 12 steps of thermal demagnetization for the stoer group two structurally integral groups of sites yield mean magnetizations of 317 0 43 1 95 11 3 n 49 and 309 9 52 1 95 10 6 n 23 some stoer specimens bear a torridon age overprint 133 3 525 95 9 6 n 19 the younger torridon group yields 138 4 52 2 95 7 4 n 42 134 9 45 5 95 16 0 n 15 and 134 4 55 1 95 11 3 n 19 from three structurally integral clusters of sites these late chemical magnetizations postdate bedding warps faults and tectonic ams fabrics they do not warrant local rigid body tilt corrections however we restored the chrm directions for the regional post cambrian eastwards tilt which affected the entire foreland from the lewisian basement to the overlying proterozoic strata paleopoles calculated from the strata s restored vectors were rotated into laurentian coordinates for comparison with canadian proterozoic palaeopoles the stoer group was magnetized in a normal polarity geomagnetic field whereas the torridon group was magnetized in a reversed polarity epoch however both sequences include at least one polarity transition indicating long duration chemical magnetizations successfully averaging secular variation at a minimum red bed magnetization processes exceeded 0 1 ma and may have encompassed several million years during stoer group magnetization the hebridean craton was at paleolatitudes of 26 44 n when the torridon group magnetized it was at 23 27 s accepting published ages this defines a minimum southward latitudinal displacement rate of 27 40 km ma restored stoer group paleopoles lie in the present day north central pacific ocean 190e 25n corresponding to the laurentian apwp dated at between 1090 and 1109 ma torridon group paleopoles lie in the south central pacific 210e 25s near the poorly documented 900 ma southernmost part of the laurentian apwp

plastic behavior of magnetite and high strains obtained from magnetic fabrics in the parry sound shear zone ontario grenville province abstract magnetic anisotropy and quantitative petrology of a transition from relatively undeformed metaanorthosite protolith to highly deformed ultramylonite in the parry sound shear zone provide information on magnetite as a kinematic indicator rock magnetic experiments show that anisotropy of magnetic susceptibility ams is controlled by magnetite in the mylonites and ultramylonites and by paramagnetic minerals hornblende biotite ilmenite in the protolith geothermometry in the ultramylonite indicates a temperature of 630 50 c during deformation a deformation mechanism map calculated from published experimental work for 630 c indicates that magnetite in the parry sound shear zone deformed plastically rather than via rigid body rotation the ams orientations accurately track a foliation trajectory in a portion of the shear zone which allows the utilization of orientation based strain models to determine shear strains shear strains of 1 9 were obtained and an empirical correlation of strain with the ellipsoid shape resulted in the logarithmic relationships mmax 0 15 ln x and mmin 0 13 ln z where mi ki kmean describes the principal ams axes or k max k min x z 0 14 these ams strain correlations were subsequently applied to mylonites and ultramylonites elsewhere in the shear zone predicting shear strains as high as 13 these observations also reveal that ams fabrics do not saturate at high strains as would be expected for rigid body rotation due to the plastic behavior of magnetite during deformation

from qualitative to quantitative magnetic anisotropy analysis the prospect of finite strain calibration abstract a method of separating low field susceptibility anisotropies due to ferrimagnetics and the matrix proposed hitherto in cases where the principal axis of these two components are merged is generalized in cases where the axes are distinct the method consists of analysing in specimens close in the same sample anisotropies the differences of which are due to the variation of respective percentages of the two components although the strain rate remains constant one thus uses the cause which itself renders global anisotropy unusable a first application is presented where a control using the anisotropy of isothermal remanent magnetization allows the validity of the method to be tested a discussion of the choice of the best ellipsoid relative either to the matrix or to the ferrimagnetics to give the best indication of relative finite strain rate is opened

correlation between magnetic anisotropy and fabric for devonian shales on the appalachian plateau the magnetic anisotropy of devonian black shale samples was measured from two cores drilled in the appalachian plateau the mineralogy of the shales is predominantly clay with small quantities of quartz and minor amounts of opaques and chlorite magnetite is the predominant ferromagnetic mineral present in the samples the magnetic fabric was measured at both room temperature and liquid nitrogen temperature and is dominated by a well defined bedding vertical compaction and a lesser defined magnetic lineation measurements of the anisotropy of magnetic susceptibility ams at liquid nitrogen temperature which enhances the paramagnetic contribution in the rock showed a strong increase in both the bulk susceptibility and susceptibility differences this increase suggests that the ams is controlled by the paramagnetic minerals particularly the clays and chlorite strain was measured from the orientation of basal planes of the chlorite crystals by texture goniometry good correlations have been found 1 between the orientation of the magnetic lineation and the long axes of the chlorite crystals and 2 between the degree of magnetic foliation and the amount of vertical compaction the magnetic lineation also agrees well with the direction of seismic anisotropy over the plateau the anisotropy of the anhysteretic remanence which expresses the anisotropy due to the ferromagnetic component in the rocks shows a weaker correlation with the amount of vertical compaction a weak magnetic lineation suggests that the magnetite grains were aligned during a deformation phase which post dates the main alleghanian orogeny the magnetic anisotropy of the devonian shales mirrors the compaction and tectonic fabric on the appalachian plateau

reduction spheroids from northern switzerland mineralogy geochemistry and genetic models abstract reduction spheroids are small isolated redox systems occurring in hematite stained rocks of variable age origin and provenance reduction spheroids from permo triassic continental red beds and from crystalline rocks of northern switzerland have been studied mineralogically and geochemically 48 authigenic minerals were identified in the dark mineralized cores of the spheroids most common are roscoelite uraninite and ni arsenides minerals containing ag au pd and pt have been found as well the bleached spheroids are depleted in ferric iron due to hematite dissolution mass balance calculations show that mobilization of only a minor fraction of the trace elements present in the bulk rock is needed to explain the formation of mineralized spheroids the relative mobilities were as u ni v the elements precipitated in reduction spheroid cores as mineral phases were probably released from fe hydroxides during their alteration to hematite the reduction spheroid containing red beds are unusually rich in as and b compared with underlying organic rich sediments reduction spheroid formation probably took place during mesozoic time at depths of burial of 400 1100 m pore waters were highly saline organic matter of unknown origin reacted with dissolved high valence ions and hematite at discrete sites in the rocks and caused local precipitation of rare elements as mineral phases and dissolution of hematite the formation of reduction spheroids is not due to detrital organic matter as is demonstrated by their presence in crystalline rocks and by the absence of organic relicts of the needed size ore mineral precipitation probably was catalyzed by bacteria because sulfides were formed by in situ lowtemperature

modeling fingered flow of water in soils owing to wetting front instability a review abstract fingered flow in the unsaturated zone caused by wetting front instability enhances solute leaching to the groundwater this paper reviews recent progress in fingered flow research focusing on theoretical results and model development a variety of stability criteria have been derived to predict wetting front instability mainly through linear and sometimes non linear stability analysis but also by theoretically analyzing infiltration into dry soils and by stochastic methods that take into account random variations of the soil properties fluid pressure and front location these stability criteria are discussed and compared eight expressions for finger size are presented they fall into three categories based on the dependence on the ratio of the infiltration rate to the soil hydraulic conductivity in the finger next the modeling of finger growth is discussed because of its relevance to solute transport recent advances in the measurement and modeling of finger behavior in moist soils are thoroughly reviewed various models ranging from easily applied closed form equations for risk assessment to sophisticated transient numerical codes have been developed over the past 15 years these are discussed and selected results are shown finally some remaining gaps in our understanding are given among these are the role of the initial water content the nature of the flow in the distribution zone above the fingers the effect of soil heterogeneity on wetting front instability and the combined effect of soil heterogeneity and wetting front instability on field scale solute transport

decadal link between longitudinal morphological changes in branching channels of yangtze estuary and movement of the offshore depo center in estuaries the morphology of inland and offshore areas usually evolves synergistically this study examines the decadal link between longitudinal changes in morphology of branching channels and movement of the offshore depo center where sediment deposition rate is maximum of the yangtze river estuary under intense human interference integrated data analysis is provided on morphology runoff discharge and ebb partition ratio from 1950 to 2017 channel volume reductions and change rates between isobaths in branching channels reflect the impact of estuarine engineering projects ebb partition ratio and duration of discharge 60 000 m3 s 1 act as proxies for the water excavating force in branching channels and runoff intensity it is found that deposition occurs in the lower upper sub reaches or further downstream upstream channels of the inland north south branching channels and the offshore depo center moves southward or southeastward as runoff intensity grows the reverse occurs as runoff intensity declines this is because the horizontal circumfluence in the yangtze estuary rotates clockwise as ebb partition ratios of the north south branching channels increase decrease for increasing runoff and conversely rotates anticlockwise for decreasing runoff land reclamation activities the deepwater channel project and the qingcaosha reservoir have impacted greatly on longitudinal changes of morphology in the north branch and the south passage and on ebb partition ratio variations in the north south channel and the north south passage dam induced runoff flattening has enhanced deposition in the upper lower sub reaches of the north south branching channels and caused northward movement of the offshore depo center except in areas affected by estuarine engineering projects dam induced longitudinal evolution of branching channel morphology and offshore depo center movement will likely persist in the future given the ongoing construction of large cascade dams in the upper yangtze and the completion of major projects in the yangtze estuary

gravity driven infiltration instability in initially dry nonhorizontal fractures experimental evidence demonstrating gravity driven wetting front instability in an initially dry natural fracture is presented an experimental approach is developed using a transparent analog rough walled fracture to explore gravity driven instability three different boundary conditions were observed to produce unstable fronts in the analog fracture application of fluid at less than the imbibition capacity inversion of a density stratified system and redistribution of flow at the cessation of stable infiltration the redistribution boundary condition analogous to the cessation of ponded infiltration is considered in a series of systematic experiments gravitational gradient and magnitude of the fluid input were varied during experimentation qualitative observations imply that finger development is strongly correlated to the structure of the imbibition front at the onset of flow redistribution measurements of fingertip velocity are used to develop a first order relationship with fingertip length measured finger width is compared to theoretical predictions based on linear stability theory