dissolution and replacement creep a significant deformation mechanism in mid crustal rocks abstract zoning patterns and zoning truncations in metamorphic minerals in a granodioritic orthogneiss indicate that strain and s c fabrics in these rocks were produced by dissolution precipitation and replacement processes even at epidote amphibolite facies metamorphic conditions the metamorphic fabric is defined by alternating layers and folia dominated by quartz feldspars and biotite epidote zoning patterns in most metamorphic plagioclase orthoclase epidote and sphene are truncated at boundaries normal to the shortening direction suggesting dissolution interfaces of relict igneous orthoclase phenocrysts that face the shortening direction are embayed and replaced by biotite epidote and myrmekitic intergrowths of plagioclase and quartz metamorphic plagioclase grains are also replaced by epidote we interpret these microstructures to reflect strain enhanced dissolution the cores of many grains show asymmetric overgrowths with at least two generations of beards all oriented on the ends of grains that face the extension direction we interpret these textures to reflect precipitation of components dissolved by deformation enhanced dissolution while biotite and quartz probably deformed by dislocation creep the overall deformation was accommodated by dissolution perpendicular to the shortening direction and precipitation parallel to it these chemical processes must have been activated at lower stresses than the dislocation creep predicted from extrapolations of data from experiments in dry rocks thus wet crust is likely to be weaker than calculated from these experimental studies

the geomorphic dynamics and environmental history of an upper deltaic floodplain tract in the sacramento san joaquin delta california usa a multi proxy approach was used to examine the geomorphic dynamics and environmental history of an upper deltaic oodplain tract in the sacramento san joaquin delta california three long cores were collected from the mccormack williamson tract mwt and these cores were analyzed for bulk density loss on ignition ne clay and silt content al concentration magnetic susceptibility pollen and charcoal radiocarbon dates obtained for the cores were converted into calendar years and an age depth model was constructed long term vertical accretion and sedimentation rates were estimated from the age depth model cross core relations show that coarse sediment generally accumulates more rapidly and has greater magnetic susceptibility compared to ne sediment percentage ne and loi data show a strong linear relationship that indicates ooding is the primary mechanism for the deposition of particular organic matter on the oodplain and that landscape wash load has contributed a highly consistent fraction of persistent organic matter averaging 5 5 per cent to the site down core grain size pro les show two hydrological domains in the cores namely millennial ne coarse uctuations superimposed on general up core ning coarse sediment is viewed as channel or near channel overbank deposits whereas ne deposits are considered to be distal overbank ood deposits the coarse ne uctuations are indicative of changing depositional settings as channels migrated laterally across mwt whereas the upward ning trend re ects a combination of self limiting overbank deposition as oodplain elevation increased and decreasing competence as sea level rise reduced ood pulse energy slopes mwt has been cross cut and incised numerous times in the past only to have the channels abandoned and subsequently lled by ne sediment the channels around mwt attained their modern con guration about 4000 years ago mwt likely came under tidal in uence at about 2500 cal bp wetlands have recently developed on mwt but they are inorganic sediment dominated copyright 2004 john wiley sons ltd

the significance of grain scale stresses in the kinetics of metamorphism during metamorphism phases grow and dissolve dominantly along grain boundaries bulk diffusion models for the development of metamorphic textures often assume that diffusion is homogeneous in regions of each phase rather than being localised along phase boundaries under isotropic stress chemical potentials of components involved in reactions are likely to be buffered along grain boundaries between phases thus inhibiting diffusion and growth motive forces must exist which overcome this and it is proposed here that local heterogeneous stresses will be important a mathematical theory for stress controlled growth is derived this theory predicts that the growth rates of two phases along their mutual interface will be linked in a quantifiable way it forms a basis for considering the important effects of stresses induced by local volumetric changes during metamorphism and it provides a link between these effects and those related to pressure solution in deforming rocks

relation between flow through and volumetric changes in natural expansive soils abstract geology and climate govern the evolution and behavior of natural expansive soils in the semi arid canadian prairies the regina clay deposit has a flat topography a homogenous composition and contains hair line fissures this research focuses on understanding the relation between flow through and volumetric changes in the natural expansive soil based on analysis of test data it is concluded that flow occurs through macro pores or fissures 5 10 8 m s during structural volume change and through micro pores or matrix 10 9 m s during normal and residual volume changes the hydraulic conductivity decreases by several orders of magnitude and becomes asymptotic vapor flow 2 10 14 m s during residual volume change a complete assessment of soil behavior requires water retention swell shrink and hydraulic conductivity curves the proposed straight line representation of the functions components is useful for predicting field response of expansive soils

discussion on effects of different drying rates on shrinkage characteristics of a residual soil and soil mixtures by henry krisdani harianto rahardjo eng choon leong engineering geology 102 2008 31 37

river response to rapid holocene environmental change evidence and explanation in british catchments macklin m g jones a f lewin j 2010 river response to rapid holocene environmental change evidence and explanation in british catchments quaternary science reviews 29 13 14 1555 1576 sponsorship welsh assembly government and the higher education funding council for wales for funding this study through its support of the centre for catchment and coastal research at aberystwyth university

river entrenchment and terrace formation in the uk holocene abstract a meta analysis of a large database of 14c dated fluvial units is used to assess the chronology and controls of episodic holocene river entrenchment and terrace formation in the uk most holocene terraces are of a fill cut type developed in pleistocene sediments in places now reaching down to pre holocene bedrock holocene terraces are widespread in higher relief areas of the uk and peripheral higher energy rivers and include up to 7 levels in some valley floor reaches using 14c constrained data sub sets for incision episodes the onset vertical ranges formation times and rates of entrenchment are examined together with geographical distributions the height range of terrace separation is relatively small 0 5 3 5 m with a long term averaged incision rate over the late and mid holocene of 0 43 0 5 0 67 0 7 and 0 81 m ka in the tweed rheidol severn ouse and ribble catchments and a regional similarity in the scale of incision events the periods 4200 3700 3100 2900 2100 1900 1800 1500 cal bp and most notably the last 1000 years with prominent peaks at 900 800 and 700 600 cal bp were times of accelerated incision it appears likely that extreme flood events triggered the formation of incision slots rather than entrenchment being a direct response to glacio tectonic uplift or the result of incremental valley floor lowering by combined incision and lateral reworking river entrenchment has also been rapid in recent centuries reflecting the coupling of extreme events with anthropogenic effects on catchment hydrology incision results in changes of river channel flood power and overbank flood extent and improved data on the long term and large scale vertical tendency of uk rivers are needed for flood risk management purposes

fluvial development and the sediment regime of the lower calder ribble catchment northwest england in the lower reaches of the calder lancashire tributary of the ribble catchment northwest england five river terraces set into the surrounding glacial terrain have been mapped and their underlying sediments radiocarbon dated the earliest terrace t1 reflects sandur style deposition during deglaciation and it aggraded in a reach cut into glacial diamict and glaciolacustrine muds incision below t1 spanned the start of the holocene driven by a combination of reduced sediment supply under a stabilising landscape and lower base levels t2 had aggraded and was being abandoned by 4000 bc its formation latterly involving a period of comparative stability in terms of channel migration perhaps a function of extensive forest cover and sea levels reaching above present day levels the last 3000 years were marked by substantial changes in the sedimentary regime with increased and varying sediment supply driving cycles of cut and fill and greater lateral channel migration these changes coincided with the first widespread and substantial reductions in forest cover and a progression towards an agricultural landscape between the aggradation of terraces t3 and t4 there was a substantial increase in sediment supply which is broadly in keeping with the erosion history in the surrounding uplands this sediment slug appears to have induced a switch from highly sinuous meandering to lower sinuosity channels characterised by lateral scroll style migration late holocene vegetation changes particularly woodland removal driven by anthropogenic land pressure appear to have rendered the floodplain prone to channel migration and the landscape more susceptible to erosion

coupling relationships hillslope fluvial linkages in the hodder catchment nw england abstract variations in the coupling of sediment transfer between different parts of a fluvial catchment e g hillslope to axial stream can hamper understanding but are an integral part of the geomorphological record depositional environments respond to a combination of land use climate storms floods and autogenic conditioning the distribution of sediment in the upland landscapes of nw england is out of equilibrium with contemporary climate and geomorphological processes more a function of peri and paraglacial mobilisation of glacigenic deposits soil and vegetation development after deglaciation have interrupted any progression toward sediment exhaustion with sediment release controlled largely by extrinsic perturbation with late holocene anthropogenic activity climate and extreme hydrological events the likely candidates this paper presents a new radiocarbon dated holocene geomorphological succession for the river hodder nw england alongside evaluating new palaeoecological and geoarchaeological data to discern the impacts of human activity these data show a late holocene expansion in human occupation and use of the landscape since the iron age 700 0 cal b c with more substantial changes in the character and intensity of upland land use in the last 1300 years the geomorphological responses in the uplands were the onset of considerable and widespread hillslope erosion gullying and associated alluvial fan development interpretation of the regional radiocarbon chronology limits gullying to four more extensive and aggressive phases after 500 cal b c the downstream alluvial system has responded with considerable valley floor deposition and lateral channel migration that augmented sediment supply by remobilising the existing floodplain terraces and led to the aggradation of a series of inset alluvial terraces the timing of these changes between states of aggradation and incision in alluvial reaches reflects the increased connectivity between the hillslope and alluvial systems aspects of both the regional climate and land use histories are conducive to increasing discharge and sediment flux but the region wide lowering of erosion thresholds appears a key driver conditioning these sediment rich conditions and producing a landscape that was more susceptible to erosion under lower magnitude flows

drying induced shrinkage of boom clay an experimental investigation drying induced shrinkage of geomaterials may have a strong effect on geostructure stability and deformation the settlement of foundations and fracture openings in slopes roads and tunnel walls may be due to drying shrinkage however there is still a lack of knowledge concerning shrinkage evolution with time and shrinkage propagation within the material in this study the shrinkage of a specific clayey rock boom clay under drying conditions is investigated experimentally this rock is a deep geological formation which is under study for high level and long term radioactive waste storage in belgium two experimental campaigns are presented the first based on the vapour equilibrium drying technique and coupled with sample size manual measurement aims to characterize the material shrinkage in balanced states the second based on the convective drying technique and coupled with shape monitoring using x ray tomography aims to analyse how shrinkage develops before reaching a steady state both app

water content void ratio swell shrink paths of compacted expansive soils this paper addresses the behaviour of compacted expansive soils under swell shrink cycles laboratory cyclic swell shrink tests were conducted on compacted specimens of two expansive soils at surcharge pressures of 6 25 50 00 and 100 00 kpa the void ratio and water content of the specimens at several intermediate stages during swelling until the end of swelling and during shrinkage until the end of shrinkage were determined to trace the water content versus void ratio paths with an increasing number of swell shrink cycles the test results showed that the swell shrink path was reversible once the soil reached an equilibrium stage where the vertical deformations during swelling and shrinkage were the same this usually occurred after about four swell shrink cycles the swelling and shrinkage path of each specimen subjected to full swelling full shrinkage cycles showed an s shaped curve two curvilinear portions and a linear portion however the swelling and shrinkage path occurred as a part of the s shaped curve when the specimen was subjected to full swelling partial shrinkage cycles more than 80 of the total volumetric change and more than 50 of the total vertical deformation occurred in the central linear portion of the s shaped curve the volumetric change was essentially parallel to the saturation line within a degree of saturation range of 50 80 for the equilibrium cycle the primary value of the swell shrink path is to provide information regarding the void ratio change that would occur for a given change in water content for any possible swell shrink pattern it is suggested that these swell shrink paths can be established with a limited number of tests in the laboratory

the importance of plant macrofossils in late glacial climatic reconstructions an example from western norway a contribution to the north atlantic seaboard programme of igcp 253 termination of the pleistocene abstract late glacial pollen diagrams from two sites on the outermost coast of western norway are discussed on the islands of utsira paus 1990 and blomoy mangerud 1970 during the allerod chronozone 12 000 11 000 bp their climatic reconstructions depend on the assumed local occurrence of tree betula b pubescens at blomoy and on the presence of pollen of thermophilous taxa at utsira the plant macrofossil analyses at these same sites do not indicate the presence of betula at either during the allerod reconstruction of the local vegetation is of willow shrubs and empetrum dwarf shrub heath at utsira and of salix herbacea dominated vegetation at blomoy these reconstructions accord well with modern analogues above the tree line in the west norwegian mountains the inferred summer temperatures during the allerod are thus 2 6 c lower than had been proposed from pollen evidence alone late glacial plant macrofossil assemblages can generally be easily matched with modern vegetation analogues on the west norwegian coast it would appear that the pollen of betula and thermophilous indicators arrived by long distance dispersal facilitated by the strong winds during the late glacial the frequently found no analogue pollen assemblages of the late glacial period may therefore be due to their previously unsuspected content of extra regional pollen dispersed by strong winds this emphasises that climatic reconstructions should only be made using taxa that were certainly growing locally it demonstrates the importance of using locally derived ecologically sound vegetational reconstructions for the reconstruction of late glacial climates and for this plant macrofossil analysis is invaluable

swelling phenomena and effective stress in compacted expansive clays the central aim of this paper is to discuss the applicability of the effective stress principle as defined by terzaghi total stress minus pore water pressure to predict the behaviour of expansive

influence of drying wetting cycles on soil water characteristic curve of undisturbed granite residual soils and microstructure mechanism by nuclear magnetic resonance nmr spin spin relaxation time t2 relaxometry due to the formational environment and climatic variability granite residual soils with grain size distribution ranging from gravel to clay undergo multiple drying wetting cycles the influences o

braiding and meandering parameters modifications to standard definttrons of brarding and meandertng are proposed to indicate the morphology of every rrver channel reach quantrtatrvely whether tt has srngle channel or multiple chinnels srnuosrty p rs defined as p l llr where l ts the length of the midline of the channel rn single channel rivers or the wldest channel inlnulti channel rivers and lp is the overall length of the reach braiding rs a measure of channel multiplicity and a new term brard channel ratlo b has been defined as b l rorll o where l o is the total of the mrd channel lengths of a ll the channels tn a reactt anoiiiir e p ssion for the brard channel ratto which gives the same numerical rcsult is b p rorl p where the total sinuosity p o l o1 lp and p has been defined above scatter pio on braid channel ratlo slnuoslty axes show a negatlve correlatton between these parameters as would be expected from the above relatlonshrps stnglechannel rivers b l have relatrvely hrgher srnuosrtres and the upper hmrt of these rs the point at which cut off becomes hrghly probable for multi channel rivers a i sinuoslty iemains low reflecting the limrtrng effect of braid bars on the development of fully dcveloped spiral seconciary flow data analyses showing that increasesin channel slope and bankfull diiharge are associated with changes from meandering to braided morpiology are diverting attenti on from the importance of the rncreased avarlability of bed load grade sediment as a control a variety of river systems supplying water and sediment to the gangetic al luvial plarns of indta have been investigated these alluvral plains are some of the most extensive in the world so the examination has dcpcndcd hcirvi ly t l thc tr c l topographical maps and satel l l te imagcs i he degree of braiding and meanderrng displayed by these rivers varies greatly from rlver to rtver and along the course of part lcular r lve rs ollc of thc first steps has therefore been to devise methods of measuring the degree of brardrng and meandering which can be applied to al l the rivers using maps and satel l i te tmagcs wrth exist ing schemes a r ivcr channel rcach cun either be expressed ln terms of brardrng or meandering sinuosrty although arguments have been developed against the thresholds between brarding and meandering that were suggested by leopold wolman 1957 there have been very few attempts at devlsing common parameters to quantl tat ively express the morphology of channels that vary from one type to the other the f irst part of this paper discusses definit ions of braiding and nrcanderrng rnd thc modif icat ions of these definrtrons that havc been adopted variat ions of thcsc nume rtcal measurements are then r l lustrated hrghhghting some of thc factors that may bc tnvolvcd tn causlng the variatton the meandering parameter sinuosity two minor modrf icat ions have been adopted to the procedures previously used in defining the slnuosity of channcls e g l copold wolman 1957 first ly the channel length has been measured along a l ine that runs mid way between the channel banks this has al lowed mcasuremcnt readl ly from topographical maps aenal photographs and satel lr te images and also has the advantage that the channel length is unlrkely to change ln a major way with changes of r rver water leve l secondly the r ivers rn india show so many transit ions between srngle channel and brarded morphologies that i t was found necessary to abandon the hard and fast dist inct ion be ween braided and meandering classes of r ivers and employ definit ions of brarding and meandering that can each be applied to every rrver no matter whether i t has single or multrple channels or both therefore the meandering sinuostty parameter has been extended to mult i channel situations where i t is based on the mid channel length o f the channe l tha t rs wtdes t tn each reach of the channel belt the modif ied sinuosttv parameter p rs

hillslope gullying in the solway firth morecambe bay region great britain responses to human impact and or climatic deterioration abstract in the solway firth morecambe bay region of great britain there is evidence for heightened hillslope instability during the late holocene after 3000 cal bp little or no hillslope geomorphic activity has been identified occurring during the early holocene but there is abundant evidence for late holocene hillslope erosion gullying and associated alluvial fan and valley floor deposition interpretation of the regional radiocarbon chronology available from organic matter buried beneath alluvial fan units suggests much of this geomorphic activity can be attributed to four phases of more extensive gullying identified after 2500 2200 1300 1000 1000 800 and 500 cal bp both climate and human impact models can be evoked to explain the crossing of geomorphic thresholds and palaeoecological data on climatic change bog surface wetness and human impact pollen together with archaeological and documentary evidence of landscape history provide a context for addressing the causes of late holocene geomorphic instability high magnitude storm events are the primary agent responsible for gully incision but neither such events nor cooler wetter climatic episodes appear to have produced gully systems in the region before 3000 cal bp increased gullying after 2500 2200 cal bp coincides with population expansion during iron age and romano british times the widespread and extensive gullying after 1300 1000 cal bp and after 1000 800 cal bp coincides with periods of population expansion and a growing rural economy identified during norse times 9 10th centuries ad and during the medieval period 12 13th centuries ad these periods were separated by a downturn associated with the harrying of the north ad 1069 to 1070 the gullying episode after 500 cal bp also coincides with increased anthropogenic pressure on the uplands with population growth and agricultural expansion after ad 1500 following 150 years of malaise caused by livestock and human the black death plagues poor harvests and conflicts on the scottish english border the increased susceptibility to erosion of gullies is a response to increased anthropogenic pressure on upland hillslopes during the late holocene and the role of this pressure appears crucial in priming hillslopes before subsequent major storm events in particular the cycles of expansion and contraction in both population and agriculture appear to have affected the susceptibility of the upland landscape to erosion and the hillslope gullying record in the region therefore contributes to understanding of the timing and spatial pattern of human exploitation of the upland landscape

the chronology of late quaternary fluvial activity in part of the milfield basin northeast england the sediment stratigraphy of a 4 m thick intercalated holocene alluvial fill and valley floor peat at a site in the milfield basin northumberland has been dated by a series of eight 14c assays and related to a previously analysed pollen record the sequence extends from the earliest holocene until c 2800 cal bp prior to the onset of peat inception substantial amounts of channel trenching can be demonstrated to have occurred in the milfield basin during the loch lomond stadial there is no measurable early holocene accelerated fluvial activity but a major flooding event occurred at c 7500 cal bp much earlier than recorded elsewhere in the region the explanation for this is not clear however the cessation of mid holocene overbank sedimentation at c 4000 3500 cal bp is tentatively correlated with slope stability associated with woodland regeneration 1998 john wiley sons ltd

impacts of matric suction equalization on small strain shear modulus of soils during air drying in this study a weight control bender element system has been developed to investigate the impact of matric suction equalisation on the measurement of small strain shear modulus gmax during an