allochthonous slope sequence at lobster cove head evidence for a complex middle ordovician platform margin in western newfoundland the upper part of an intact sequence of lower to middle ordovician deep water sediments which now form a large disrupted raft within the rocky harbour melange at lobster cove head is interpreted as having been deposited downslope from a drowned carbonate platform margin the entire 50 m thick section is arenig late canadian or ibexian to early whiterock in age graptolite biostratigraphy demonstrates a correlation with upper parts of the cow head group to the north the basal part of the section is a proximal facies of the cow head group shallow bay formation factory cove member beds 9 10 and part of bed 11 the upper part of the section consists of interbedded dolostone and shale and is unlike any other sequence in the cow head group this upper sedimentary sequence is defined as the lobster cove head member of the shallow bay formation cow head group contact between the two sedimentary packages is also marked by a faunal break and coincides with emplacement of megaconglomerate bed 12 at cow

finite element simulation of fluid flow in fractured rock media fluid dynamics models are used by the petroleum industry to model single and or multi phase flow within fractured rock formations in order to facilitate extraction of fluids such as oil and natural gas and in other areas of engineering to study groundwater flow as well as to estimate contaminant seepage and transport in this paper the numerical modelling software comsol is used to simulate air and water flow through a specimen of granite with a single vertical fracture subjected to triaxial loading conditions the intent of the model is to simulate triaxial test findings on a rock specimen with a natural fracture fluid flow is simulated at various confining and inlet pressures using the cubic law model results were in good agreement with laboratory findings pressure distribution along the fracture and across the specimen are as expected with a near linear pressure distribution along the length of the fracture a drawdown effect on pressure distribution across the specimen in the vicinity of the fracture is also observed pressure gradient was largely uniform however some localised zones of high gradient along the fracture are observed

a raised ois 3 sea level recorded in coastal sediments southern changjiang delta plain china abstract the distribution of marine influenced oxygen isotope stage ois 5 to ois 1 sediments was examined in several late quaternary boreholes from the southern changjiang yangtze delta plain china using different dating methods including osl u series ams 14c and paleomagnetism results demonstrate that coastal and estuarine deposition during ois 5 and ois 3 occurred throughout the study area however holocene transgressive sediments were absent on the taihu block the burial depth of intertidal to subtidal sediment deposited during ois 5e records 30 80 m subsidence caused by sediment compaction and tectonic movement since that time however coastal sediments formed during the late phase of ois 3 were buried to a depth of ca 6 15 m in the taihu lake area while the burial depth increased eastward to ca 45 60 m on the coastal plain this phenomenon combined with the distribution of holocene marine strata indicates at least 25 30 m uplift of the taihu block since the end of ois 3 we suggest that this uplift was mainly caused by the differential subsidence due to substantial amount of post glacial deposition by the changjiang and huanghe rivers on the continental shelf of east china marginal sea

worldwide initiation of holocene marine deltas by deceleration of sea level rise radiocarbon dated deltaic sequences of holocene age from different parts of the world began to accumulate within a restricted time range from about 8500 to 6500 years ago evaluation of major delta processes indicates that deceleration in sea level rise was the key factor in holocene delta formation within many deltas there is as much as a 2000 year age range between basal deposits in seaward and landward cores this age difference records the progressive landward migration of near mean sea level depositional environments during the lower to mid holocene establishment of a chronostratigraphic framework for holocene delta development provides a fundamental global baseline for distinguishing sea level change from vertical land motion by tectonism and isostasy and for evaluating rates of future marine incursion into low lying deltas

yangtze delta eastern china 1 geometry and subsidence of holocene depocenter abstract stratigraphic analysis of 59 borings serves to define the subsurface configuration of late quaternary deposits of the outer yangtze delta including both subaerial lower plain and its contiguous submerged sector isopachous maps of the holocene sediment section reveal a linear thickened trend parallel to the lower yangtze estuary chongming island which extends seaward southeast to the mid shelf maps depicting depths of the holocene to late pleistocene contact also highlight this thickened northwest to southeast trend and a deep downward bowing depression formed by the sedimentary sequence seaward of the yangtze mouth radiocarbon dated facies in the cores serve to calculate long term averaged subsidence rates for the holocene section 0 1 to 3 0 mm year on land and 1 6 to 4 4 mm year at sea this preliminary information is vital for planning coastal protection erosion salt water intrusion in this densely populated low lying region vulnerable to marine inundation

sedimentary facies of the tide dominated paleo changjiang yangtze estuary during the last transgression abstract a large estuary was formed by marine inundation of the paleo changjiang yangtze incised valley during the transgression after the last glacial maximum this paper presents the sedimentary facies and architecture of the estuary fill based on the analysis of three sediment cores cm97 js98 and hq98 obtained from the present changjiang delta plain estuary fill deposits showing an upward fining succession were grouped into five depositional facies tidal river distributary channel muddy intertidal to subtidal flats transgressive lag and estuary front based on sedimentary textures lithology and physical sedimentary structures sand mud couplets are common in these deposits indicating that tides played a significant role in producing these sedimentary structures and that the estuary type was tide dominated some of the successive sand mud couplets probably recorded neap spring cycles as well as semidiurnal tidal cycles the nature of the estuary was very different from other representative tide dominated estuaries in sediment facies its distribution and sediment source for estuarine fill unlike the other estuaries that receive sediments mainly from the sea the paleo changjiang estuarine fill deposits were supplied largely from the river this difference would also have a great influence on the sedimentological and morphological component in the estuary the sediment distribution of the estuary showed fining seaward and estuary mouth sand bodies fed by marine source sand were absent the architecture model of tide dominated estuaries should be divided into two types by the degree of fluvial sediment supply the paleo changjiang estuary shows a good example for an estuary of large rivers

evolution of the coastal depositional systems of the changjiang yangtze river in response to late pleistocene holocene sea level changes abstract the paleo changjiang yangtze incised valley fills approximately 80 90 m thick provide an opportunity to document the evolution of coastal depositional systems with large sediment supply in response to late pleistocene holocene sea level fluctuations on time scales of 103 to 104 years the sedimentary facies of the incised valley fills record three main depositional systems fluvial tide dominated estuary and tide dominated delta radiocarbon ages for the incised valley fills suggest that these depositional systems developed before about 11 ka between 11 and 8 ka and after approximately 8 ka respectively by applying sequence stratigraphic concepts the evolution of the depositional systems can be divided into three systems tracts a lowstand systems tract lst a transgressive systems tract tst and a highstand systems tract hst sea level changes on a 104 year time scale controlled the basic architecture of the sequence of the incised valley fill on the other hand sea level changes on a millennial time scale affected the stacking pattern of the systems tracts in particular the continuous sea level rise with episodic rapid rises during the last deglaciation affected the stacking pattern of the tst which is characterized by a combination of aggradation and backstepping the aggradation of fluvial and estuarine systems was dominant and the shoreline migrated only gradually landward under the relatively slow rise in sea level and a very rapid sea level rise around 12 and 10 ka caused the system to migrate abruptly landward unlike the transgressive estuarine phase the stacking pattern of the regressive tide dominated delta hst which developed within the almost filled incised valley and on the surrounding interfluve zones was characterized by seaward progradation with clinoform architecture it was initiated with aggradational and progradational stacking about 8 ka during the last phase of decelerated sea level rise and was followed by a progradational phase after the highest sea level about 6 ka

geological and hydraulic characterisation of the excavation disturbed zone in the opalinus clay of the mont terri rock laboratory abstract the fracture network in the excavation disturbed zone edz of an argillaceous formation the opalinus clay in the mont terri rock laboratory in northwest switzerland is characterised using structural and hydrogeological techniques sampling of unloading fractures is done by analysing resin injected overcores taken from the edz resulting in a structural data set of fracture orientations frequencies and extent of the edz these parameters are derived in tunnel sections which were excavated by blasting pneumatic hammering and road header techniques pneumatic and hydrogeological tests are subsequently carried out to derive hydraulic parameters such as permeability and transmissivity distributions of the fracture network synthesis of the structural and hydrogeological data led to a conceptual model of the edz in the mont terri rock laboratory which is defined by a 2 m plastically deformed zone around the tunnel this plastic zone is further divided into an inner 1 m zone consisting of an air filled fracture network and an outer zone with mostly saturated and isolated fractures transmissivities in the inner zone are orders of magnitude higher than those of the undisturbed opalinus clay finally a methodology is proposed for the structural and hydrogeological characterisation of the edz this methodology is not site specific and is thus applicable at any argillaceous underground facility

assemblages de chitinozoaires dans l ordovicien inferieur de l est du canada from a description of middle arenig chitinozoa from the levis formation zone c and the cow head group a succession of the main lower ordovician chitinozoan assemblages is proposed this succession is compared with the main assemblages described in the literature this comparison allows recognition of taxa with potential stratigraphie value

yangtze delta eastern china 2 late quaternary subsidence and deformation abstract late quaternary deposits examined on high resolution seismic profiles provide evidence of recent subsidence of the outer yangtze delta in the east china sea deformed late pleistocene strata and mud diapirs tilted bedding and gas deformed structures in holocene sequences record remobilization of underconsolidated sediment within and adjacent to the yangtze depocenter deformation types and their specific position relative to the depocenter record displacement of sediment as a result of quaternary overburden and probable compaction and deep seated tectonic motion the configuration of depositional sequences demonstrates that subsidence in the outer yangtze delta has continued from the late pleistocene to the present

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

seismic investigation of the excavation damaged zone in opalinus clay a mini sonic borehole probe was used to investigate the excavation damaged zone edz around an underground opening in the opalinus clay in the mont terri rock laboratory in switzerland the edz could be determined by using seismic parameters as interval velocities and amplitudes of first arrivals derived from measurements in eight radial drilled boreholes the extent of the edz is about 1 m but varies between 0 6 and 2 2 m

engineered damage zone sealing during a water injection test at the tournemire url low permeability clay formations provide good candidate host rocks for geological disposal of radioactive waste because there is expected to be limited movement of gas or water through the formation however when constructing tunnels the stress state in the formation around the tunnel will change which can lead to damage to the formation changing the bulk hydraulic properties of the formation close to the tunnel there is the potential for this damaged zone to act as a preferential pathway for fluid flow and radionuclide transport a water injection experiment is ongoing at the tournemire underground rock laboratory to investigate the hydraulic properties of the toarcian argillite in which the laboratory is constructed water is injected into the formation at the end of a sealed borehole and moves preferentially in the damaged zone along the borehole walls the rate of water injection into the rock changed over the first year of the experiment and the causes of this change are investigated in this paper by numerical modelling the study demonstrates that the change in water injection rate into the argillite can be explained by the evolving hydraulic properties of the damaged zone around the borehole the findings of the modelling study are discussed in the context of long term radioactive waste disposal

eastern mississippi delta late wisconsin unconformity overlying transgressive facies sea level and subsidence abstract analysis of 92 engineering core logs located in the balize sector of the eastern mississippi delta focuses on the late wisconsin unconformity and lithofacies of strata lying immediately below and above this stratigraphic horizon this major sequence boundary is a key feature used to correlate strata across shelf and slope to the basin observations emphasize lithofacies distributions of the latest pleistocene sediments underlying the unconformity the late pleistocene to early holocene transgressive facies and the immediately overlying deltaic deposits maps and a cross section compiled with this information highlight the critical relation between lithofacies distributions and late wisconsin sea level oscillations core analysis reveals that the transgressive facies comprises distinct environments of deposition offshore to onshore findings identify criteria to determine the approximate position of the shoreline at the late wisconsin maximum sea level lowstand and at the extent of early holocene maximum marine inundation in the balize complex mapping of lithologies along the late wisconsin unconformity serves to improve correlation of sediment facies with changes in acoustic response along high resolution seismic profiles an estimate of long term averaged land subsidence suggests lowering of at least 1 mm year near the shelfedge during the past 18 000 years this mapping also refines sea level response models for the mississippi delta including criteria to locate key paleogeographic features such as shelfedges and maximum flooding surfaces in other recent marine deltas and in older stacked deltaic sequences

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

chitinozoaires de l arenig superieur zone d de la formation de levis quebec canada the shumardia limestone that forms the upper part of the levis formation zone d yields well preserved assemblages of chitinozoans these assemblages seem to be characterized by a new species cono

a robust geochronology of the yangtze river delta based on magnetostratigraphy and cyclostratigraphy of sediment core zka2 abstract studying the evolution of sea level fluctuations climate oscillations and tectonic movements in the yangtze river delta requires a reliable chronology here we present the results of a comprehensive study of the magnetostratigraphy and cyclostratigraphy of a 295 m long sediment core zka2 recovered from nantong city jiangsu province china anisotropy of magnetic susceptibility ams studies reveal that the petrofabrics are mainly primary based on rock magnetic and thermal demagnetization analyses the major magnetic minerals in the studied sediments are magnetite hematite and greigite but only magnetite and hematite carry the primary remanence the magnetostratigraphy reveals seven reversed polarity intervals nine normal polarity intervals and one interval of mixed polarity variations in natural gamma ray activity reflect variable continental weathering in the sediment source regions and are paced by earth orbital cycles notably a prominent 405 kyr long eccentricity cycle and 100 kyr short eccentricity cycle are evident which allow us to constrain the basal age of core zka2 to 3 1 ma the magnetostratigraphic and cyclostratigraphic results together enable us to define the depths of key chronostratigraphic and magnetostratigraphic boundaries they include the late middle pleistocene boundary at 18 m depth the brunhes matuyama boundary at 88 m depth and the matuyama gauss boundary at 254 m depth according the new chronology we find that although clear long eccentricity 405 kyr and short eccentricity cycles 100 kyr cycles are evident in the magnetic susceptibility record they are not well matched with cycles of natural gamma ray activity this suggests the source and post depositional process of the magnetic particles is complicated and it should be cautious to choose magnetic properties for cyclostratigraphic analysis

analysis of thermo hydrologic mechanical impact of repository for high level radioactive waste in clay host formation an indian reference disposal system in our study a coupled hydrologic mechanical analysis is done of the excavation damaged zone before the emplacement of nuclear waste this is followed by a coupled thermal hydrologic mechanical analysis to evaluate the impact of nuclear waste repository in porous water containing rock mass this analysis has been under taken in accordance with the indian reference disposal system the paper considers the changes in pore pressure and stresses due to excavation of disposal holes a critical study of rock mass permeability porosity thermally induced stresses strains and temperature distribution after the emplacement of nuclear spent fuels in disposal holes has also been done coupling to the mechanical constitutive equations is done via effective normal strain rates

morphodynamic impacts of large scale engineering projects in the yangtze river delta morphodynamics of world s river deltas are increasingly affected by human activities which are of great ecological economic and social implications however impacts of human interventions in deltaic regions are insufficiently understood especially superimposed upon diminishing sediment supplies this study uses the heavily interfered yangtze river delta as an example to address this issue the morphodynamic impacts of the deepwater navigation channel project dncp during 1997 2013 are investigated through process based modeling approach delft3d and bathymetric data analysis the dncp was implemented in the mouth bar area of the yangtze river delta including the twin dikes and 19 groynes with the total length of 132 0 km hydrodynamic simulations indicate that the training walls resulted in weaker tidal flow and longer slack period at the east hengsha shoal ehs and stronger tidal flow at the subaqueous delta thus the ehs is characterized as a sediment accumulation zone after the completion of the training walls subsequently morphological modeling shows enhanced accretion at the ehs and enhanced erosion at the subaqueous delta when the training walls are taken into account numerical experiments further demonstrate that the above changes are mainly attributed to the seaward half of the northern training walls constructed in 2002 2005 this is probably the reason for the observed accretion peak of the ehs in 2002 2007 and the gradual increase in the erosion rate of the subaqueous delta after 2002 the schematized paths of sediment transport after the dncp indicate that sediment eroded from the subaqueous delta serves as an important source for accretion of the mouth bar area it is suggested that siltation promoting projects within the mouth bar area increased shallow shoal accretion and aggravated erosion at the subaqueous delta with the overall erosion of the yangtze river delta due to river sediment reduction large scale estuarine engineering projects substantially increase the complicacy of its morphodynamic pattern which merits close attention for sustainable delta management

a precise worldwide correlation of early ordovician graptolite sequences fourteen early ordovician tremadoc llandeilo graptolite sequences from around the world are precisely infrazonally correlated based on the stratigraphic ranges of 130 species and species groups the composite standard sequence css of graptolites has been determined from the six best regional sequences by a nonparametric graphic correlation two data sets were selected one comprised first appearance events of 103 taxa the other first and last appearance events of 45 taxa the results of the two runs accord well and reveal respectively 66 and 73 successive bioevents in early ordovician time event spacing averages 0 7 0 8 ma and enables fine subdivision correlation and homotaxial testing for diachroneity the strong correlation between each of the six regional sequences and the css indicates the high level of accordance among graptolite successions around the world

classification and conodont based age of the ordovician trilobite ellsaspis middle arenigian ville guay quebec ellsaspis rasetti 1945 occurs in a thin intraclast granule and echinoderm hash packstone in continental slope facies at ville guay presence of an anterior median glabellar node and assignment of

arenig biostratigraphy of the pointe de levy slice quebec appalachians canada the pointe de levy slice includes a nearly complete arenig graptolite succession a conspicuous gap exists in the yapeenian ya to lower darriwilian da part ya 1 da 1 the lithological column is compiled from several sections at levis quebec that yield only parts of the complete succession the graptolite zonation can be compared closely with that from the cow head group of western newfoundland and the deep kill formation of eastern new york the shumardia limestone is differentiated into four graptolite zones and subzones of which the youngest zone clearly belongs to the llanvirn the araneograptus murrayi and holmograptus lentus zones are documented for the first time from the levis area the undulograptus dentatus zone of the latest arenig is introduced

sedimentary facies and holocene progradation rates of the changjiang yangtze delta china abstract the changjiang yangtze river one of the largest rivers in the world has formed a broad tide dominated delta at its mouth during the holocene sea level highstand three boreholes cm97 js98 and hq98 were obtained from the changjiang delta plain in 1997 1998 to clarify the characteristics of tide dominated delta sediments and architecture based on sediment composition and texture and faunal content core sediments were divided into six depositional units in ascending order they were interpreted as tidal sand ridge prodelta delta front subtidal to lower intertidal flat upper intertidal flat and surface soil deposits the deltaic sequence from the prodelta deposits to the delta front deposits showed an upward coarsening succession overlain by an upward fining succession from the uppermost part of the delta front deposits to the surface soil thinly interlaminated to thinly interbedded sand and mud sand mud couplets and bidirectional cross laminations in these deposits show that tide is the key factor affecting the formation of changjiang deltaic facies sediment facies and their succession combined with ams 14c dating revealed that isochron lines cross unit boundaries clearly and delta progradation has occurred since about 6000 to 7000 years bp when the rising sea level neared or reached its present position the average progradation rate of the delta front was approximately 50 km kyear over the last 5000 years the progradation rate however increased abruptly ca 2000 years bp going from 38 to 80 km kyear the possible causes for this active progradation could have been an increase in sediment production in the drainage basin due to widespread human interference and or decrease in deposition in the middle reaches related to the channel stability caused by human activity and climatic cooling after the mid holocene

link between east asian summer monsoon and sedimentation in river mouth sandbars since the early holocene preserved in the yangtze river subaqueous delta front this paper presents geochemical and grain size records since the early holocene in core ecs0702 with a fine chronology frame obtained from the yangtze river subaqueous delta front since 9500 cal yr bp the proxy records of chemical weathering from the yangtze river basin generally exhibit a holocene optimum in the early holocene a weak east asian summer monsoon easm period during the middle holocene and a relatively strong easm period in the late holocene the 8 2 and 4 4 cal ka bp cooling events are recorded in core ecs0702 the flooding events reconstructed by the grain size parameters since the early holocene suggest that the floods mainly occurred during strong easm periods and the yangtze river mouth sandbar caused by the floods mainly formed in the early and late holocene the yangtze river mouth sandbars since the early holocene shifted from north to south affected by tidal currents and the coriolis force and more importantly controlled by the easm our results are of great significance for enriching both the record of holocene climate change in the yangtze river basin and knowledge about the formation and evolution progress of the deltas located in monsoon regions

initiation of the changjiang yangtze delta and its response to the mid holocene sea level change abstract the changjiang yangtze delta in eastern china is one of the largest tide dominated deltas in the world to obtain a more detailed information on its initiation we drilled three sediment cores pk01 hg01 and xj03 from the uppermost region of the delta plain on the basis of sedimentary facies and ams 14c dating we identified three depositional systems 1 a fluvial system 2 an estuarine system and 3 a deltaic system including an initial delta estuary delta transition and a typical delta the maximum flooding surface separates the estuarine and deltaic systems and occurred at ca 8 0 cal kyr bp when brackish water intruded landward and reached the nanjing area the changjiang delta was initiated at the area between nanjing and yizheng when the sea level rise decelerated after the rapid rise in sea level during 9 0 8 2 cal kyr bp the subsequent evolution of the changjiang delta has been shown as a seaward development model of river mouth bars with shoreline migration the oldest river mouth bar called hongqiao sand body which is located most landward was dated at 6 0 5 5 cal kyr bp in this study nearly one thousand years younger than the previous estimates a tide dominated funnel shaped estuary was formed at 8 0 cal kyr bp and lasted until the hongqiao sand bar became exposed this stage is regarded as an aggradation dominated initial stage of the changjiang delta followed by a progradation dominated stage that is characterized by the formation of a series of seaward migrating river mouth bars a relative sea level highstand in the mid holocene may be associated with glacio hydro isostatic tilting

modeling the growth limit of the changjiang delta river deltas grow in response to sediment discharge from the land it is not clear however whether or not there is a limit for such growth conceptual geometric models are used in this paper in association with the principle of mass conservation in an attempt to answer this question preliminary analyses of the changjiang delta indicate that delta growth is constrained by a number of factors the original topography bathymetry sediment supply sediment retention in the estuary sea level rise ground subsidence the quantity of sediment supply per unit area and the sediment retention index for the subaqueous delta decrease as the delta progrades towards deeper water resulting in a decreasing rate of growth the limit of growth is reached when the index approaches zero i e the shoreline reaches the shelf edge if the combined effect of sea level rise and ground subsidence is considered together with decrease in the sediment discharge from land the limit is reached at an earlier stage for the changjiang delta the model output using hypothesized sediment retention index estimates implies that the delta growth will reach its limit in the near future this will occur sooner if the sediment output of the river is reduced to 60 of its original level in response to the upstream basin changes further knowledge however is required of the retention index together with the information on future changes in river input and the character of the sediments in order to improve the accuracy of the simulations

graptolite conodont biostratigraphy and biofacies of the middle ordovician cerro viejo succession san juan precordillera argentina abstract high resolution graptolite conodont biostratigraphy and biofacies analysis have been carried out for the lower member of the los azules formation exposed in the cerro viejo area san juan precordillera western argentina the rock succession is composed of alternating rich fossiliferous argillites and virtually barren volcanic ash beds k bentonites of darriwilian da2 age graptolite and conodont collections from the los azules and amarilla creeks sections are studied graptolites are the most common fossils in the lower member of the los azules formation and represent the undulograptus dentatus and holmograptus lentus zones a diverse conodont fauna recovered from the uppermost limestones of the underlying san juan formation and conodont elements preserved on bedding plane surfaces in the lower los azules formation indicate the lenodus variabilis and eoplacognathus suecicus zones micaceous siltstone with bergstroemograptus crawfordi harris and abundant biserial graptolites close to the top of the lower member is notable this bed yielded the first specimens of polonodus magnum albanesi this species precedes the entrance of pygodus anitae bergstrom which is typical from the upper part of the e suecicus zone characteristic graptolites of the diplograptus decoratus zone da3 or equivalent faunas were not recorded in the studied sections suggesting the presence of a hiatus between the lower and middle members which may indicate a critical event in the history of the basin a rich conodont assemblage dominated by planktic pelagic forms periodon paroistodus protopanderodus drepanoistodus an abundant shelly fauna and scarce graptolites are recorded in the upper san juan limestone after drowning of carbonate platform the conodont diversity dramatically dropped becoming graptolites the dominant elements of the faunas in the lower member of the los azules formation the periodon pygodus biofacies represents a low diversity deep water conodont community present both in the upper part of the lower member and the middle member graptolite faunas represent the isograptid biofacies including pandemic and pacific forms of the epipelagic and deep water biotopes they are related to a transgressive event that diachronically flooded the precordilleran carbonate platform during the early middle ordovician

architectural stacking patterns of the ebro delta controlled by holocene high frequency eustatic fluctuations delta lobe switching and subsidence processes abstract during the late pleistocene and holocene 125 ka b p to present a type 1 4th order depositional sequence comprising regressive lowstand transgressive and highstand system tracts formed worldwide the holocene 10 ka b p to present part of this contains the latest and present highstand systems tract hst within this and the underlying transgressive systems tract tst of the ebro delta in northeastern spain higher frequency 5th to 6th order sea level fluctuations are recognised these form retrogradational and progradational high frequency depositional sequence sets within the tst and hst respectively each high frequency sequence comprises 1 a basal highly reflective shell lag associated with an erosional transgressive surface 2 aggradational deposits which seawards consist of a wedge of marine clays with transparent seismic facies but inland are represented by thick peats 3 progradational deposits composed of sandy delta front facies displaying slope clinoforms these pass seawards into prodeltaic grey silts and landwards into red silts and pebbly sands of delta plain facies the progradational deposits downlap towards their bases the aggradational deposits formed in response to a period of rising sea level and a rapid increase in accommodation space progradation began when sediment supply to the delta exceeded accommodation space as a result of relative sea level fall the relative sea level curve for the delta has a stepped character caused by the punctuation of the 4th order sea level trend by higher frequency eustatic fluctuations as well as by high subsidence rates of about 1 75 mm per year the tst comprises retrogradational parasequences that onlap the underlying pleistocene gravels the maximum flooding surface separating the tst from the hst was formed about 6900 yrs b p on the basis of14c dating of peats the hst comprises progradational deltaic and aggradational units stacked as progradational high frequency parasequence sets the hst of the ebro delta is compared with other deltaic sequences around the world in particular with that of the mississippi delta a tentative chronology of the high frequency climatic and eustatic oscillations influencing deltaic sedimentation globally over the last 7000 years is presented

seismic framework and the holocene morphological evolution of the changjiang river mouth china abstract acoustic profiling in combination with coring has been used to examine the recent evolution of river mouth of the changjiang two acoustic facies are present petrologic radiometric and seismic analyses show that the upper facies i of 10 20 m thick fine sand and silt represents the sandy shoals of late holocene age in the distributary and the 5 20 m thick lower facies ii of fine grained silty clay with abundant marine microfossils represents the mid holocene prodelta facies deposited as fillings in the former large estuarine valley of late pleistocene to early holocene origin rapid accumulation during the holocene has led to some instability of unconsolidated sedimentary strata in the distributary such as strata collapse and mud diaper formation the existence of large cross beddings such as tabular and trough stratification in facies i identifies the sediment transport as predominantly bed load driven by runoff and tidal currents two sets of discrete flood ebb flow troughs oriented nw and se reflect controls by tidal waves generated from the sea and the superimposition of runoff and ebb flows symmetrical sand waves that appear at the northern trough of one of the distributaries also indicate the balancing sediment dynamics between runoff ebb and flood currents whereas the asymmetrical ones in the southern trough indicate superimposed sedimentation by runoff and ebb flows a large quantity of sediment has been deposited in the slack water region between the discrete flood and ebb flows to form sandy shoals the principal mechanism of the evolution of estuarine islands in the holocene changjiang mouth the morphology of the extended river mouth to the southeast possibly indicates an external driving force such as the coriolis effect nw prevailing wind and longshore currents

coupled multiphase flow and elasto plastic modelling of in situ gas injection experiments in saturated claystone mont terri rock laboratory abstract understanding gas migration in host rock is one of the most important issues to consider in the final disposal of radioactive waste in deep geological formations in order to investigate gas transport in water saturated argillaceous rock constant gas pressure injection tests on the samples from the mont terri rock laboratory switzerland as well as pulse injection tests with a stepwise increasing of gas pressure were carried out during gas migration desaturation and hydraulic mechanical interaction can be observed to simulate gas migration in water saturated porous media a coupled multiphase flow and mechanical method within the fem code family opengeosys ogs was developed including the van genuchten function for the relationship between capillary pressure and water saturation the approach of mualem for the relative permeability of both gas and water phases and an elasto plastic deformation model two approaches were applied taking into consideration the permeability change by pore gas pressure and by deformation respectively both permeability approaches are based on experimental observations and allow for the significant increase in permeability when gas pressure exceeds the minimal stress the material parameters for the multiphase model are determined using the measured data from laboratory experiments under well defined test conditions with the calibrated model parameters the in situ experiment was simulated good agreement between the numerical results and the experimental data is achieved

deltaic land subsidence and sea level fluctuations along the east coast of india since 8 ka a palynological study the consequences of climate change and land subsidence are often related to sea level rise fall mangrove extinction and migration were assessed through palynological studies in two sedimentary cores in order to address climate relative sea level rsl and its relation to geomorphology since 8420 cal yr bp from kanuru 500 cm deep and since 5850 cal yr bp from machilipatnam 118 cm deep krishna delta india four units nine phases of sediment depositional environment were identified on the basis of marine terrestrial palynomorphs in unit 1 the marine palynomorphs indicate palaeoshoreline in kanuru from 8420 to 8300 cal yr bp which is now 4 5 km from the present day shoreline but after a short span a retreat in sea level took place between 8300 and 7040 cal yr bp about three to four short term intermittent rise fall in rsl were recorded in unit 2 between 7040 and 3980 cal yr bp in kanuru and between 5225 and 3240 cal yr bp in machilipatnam during this period the diversity of mangroves was

dating modern deltas progress problems and prognostics 1 abstract radiocarbon dating is the method most frequently used to date holocene deltaic sequences but less than one quarter of 14c dates are within 500 years of predicted age such dates tend to be unreliable in other words often too old and commonly inverted upsection and core sample dates obtained near deltaic plain surfaces may be as old as mid to late holocene stratigraphic irregularities result primarily from downslope reworking of upland alluvial sediment with displacement of old carbon in the sediment that accumulates in lower valleys and deltaic plains use of dates that are too old results in inaccurately calculated rates most often too low of relative sea level rise and or land subsidence more reliable timing of deltaic sediment requires a multiple method dating approach including where possible identification of associated archaeological material developing an accurate dating strategy is a critical step for implementing reliable coastal protection measures needed for the rapi

environmental change in the yangtze river delta since 12 000 years b p abstract a 52 m core from qidong at the tip of the yangtze river chang jiang delta provides a history of sea level change deltaic development and vegetational and climatic changes during the last 12 000 yr about 12 000 yr ago when sea level was about 60 m below the present level the coring site was situated in the innermost part of the exposed continental shelf the late pleistocene vegetation on the uplands of the lower yangtze river valley was a mixed forest of deciduous and broadleaved evergreen trees in which betula ulmus tsuga and cupressaceae were slightly more abundant than at present abies and picea were probably present as relict populations on mountains bordering the region rapidly rising sea level converted the qidong area to a coastal or estuarine environment between 11 000 and 10 800 yr b p leading to widespread development of wetlands dominated by gramineae and cyperaceae during the next 2500 yr coastal erosion due to marine transgression obliterated the sedimentary record deltaic sedimentation predominated from 8300 to 3800 yr b p as the yangtze river delta prograded by successively building a series of estuarine sand bars during the mid holocene the climate was slightly warmer and more humid than at present allowing the subtropical broadleaved evergreen trees to increase their populations pinus and quercus became more abundant after 3800 yr b p in response to climatic cooling the present deltaic plain in qidong formed less than 200 yr ago

the lower ordovician fezouata konservat lagerstatte from morocco age environment and evolutionary perspectives abstract the lower ordovician fezouata konservat lagerstatte from southern morocco has been one of the major palaeontological discoveries of the last decade it provides a unique insight into one of the most critical periods in the evolution of marine life the cambrian ordovician transition however its potential for deciphering key trends in animal diversification was hitherto largely limited by major uncertainties concerning its stratigraphic position age and environmental setting based on extensive fieldwork fossil evidence and facies recognition our study provides clarification on these three crucial issues exceptional preservation is limited to two intervals within the fezouata shale graptolites indicate a late tremadocian age for the fezouata konservat lagerstatte as a whole which is supported by biostratigraphical evidence provided by acritarchs sedimentological features and reconstructed patterns of relative sea level changes indicate relatively shallow water environmental conditions under distal storm influence in an offshore to lower shoreface siliciclastic ramp setting the fezouata biota represents a unique and exceptional window into the palaeobiodiversity in open marine conditions thus contrasting with the other ordovician konservat lagerstatten presently known in our analyses of this new set of data we pave the way for accurate temporal faunal and environmental comparisons with other lower palaeozoic konservat lagerstatten and unlock the full potential of the fezouata biota to better understand the processes and scenarios of early animal radiations

analysis of flow path around the sealing section hg a experiment in the mont terri rock laboratory as part of the hg a experiment in the mont terri rock laboratory large scale in situ water gas injection experiments was conducted in a microtunnel this research work focuses on the numerical analysis of the experimental data and the in situ observations concerning a temporary change of the hydromechanical properties of opalinus clay during experimental operations three phases were numerically interpreted these included the generation of excavation damaged zone during tunnel excavation in which highly permeable flow paths around the tunnel have been formed the self sealing effect during water tests and the pressure evolution during a long term gas injection test a coupled two phase flow and mechanics model taking into account the strong anisotropic properties of opalinus clay was developed to interpret the measured data the hydraulic anisotropy was described by a transversely isotropic permeability tensor an elasto plastic model was established to consider both stiffness anisotropy and strength anisotropy anisotropic plasticity was studied using the microstructure tensor method

yapeenian early ordovician graptolites in the quebec appalachians a newly discovered oncograptus upsilon fauna occurs in a sequence of turbiditic siltstones within the lower ordovician ste anne river nappe in the gaspe area of quebec this is the first discovery

neolithic agriculture freshwater resources and rapid environmental changes on the lower yangtze china analyses of sedimentary evidence in the form of spores pollen freshwater algae dinoflagellate cysts phytoliths and charcoal from ams 14c dated holocene aged sequences provide an excellent opportunity to examine the responses of neolithic agriculturalists in the lower yangtze to changing environments evidence from two sites close to the southern margin of the yangtze delta and separated by what is now hangzhou bay attests the critical importance to early attempts at food production of access to freshwater resources more readily if episodically available freshwater resources during the early to mid holocene on the hangjiahu plain may have encouraged an early reliance on rice based agriculture which in turn facilitated the accumulation of agricultural surpluses and cultural diversification cultural change was relatively attenuated and human population pressures possibly lower on the ningshao plain seemingly because of much more profound environmental impacts of variations in local hydrological conditions and because predominantly saline conditions associated with rising relative sea level hampered the early development of irrigated agriculture the evidence although largely dating to the early and middle parts of the holocene provides a timely warning of the complexity of vulnerability to climate change induced processes of agriculture and indeed human activities more generally on megadeltas in asia

upward decrease of organic c n ratios in the okinawa trough cores proxy for tracing the post glacial retreat of the continental shore line abstract six piston cores were collected along the nw se line in the okinawa trough close to the chinese continental shelf edge and dated by 23 ams 14 c measurements along with planktonic 18 o stratigraphy and an ash layer dated as 6 3 ka on a time scale to 19 ka the ratio of total organic carbon to total nitrogen concentration c n ratio displays gradual decreases toward the present and suggests the decrease of vascular plant fragment input to the trough from continental rivers this suggestion is confirmed by similar decreases of lignin phenol content and ratio of c 28 fatty acid to c 16 fatty acid content in core rn93 pc3 the gradual decrease of land plant fragment input is interpreted to be a consequence of the retreat of the continental coastline during the deglacial period

transparent heavy minerals and magnetite geochemical composition of the yangtze river sediments implication for provenance evolution of the yangtze delta abstract heavy mineral and detrital magnetite geochemistry were analyzed to extract sediment provenance indexes from different reaches of the modern yangtze river which were used to trace sediment source of the yangtze delta and to speculate its geomorphology change since the pliocene our results show that diagnostic heavy minerals of the upper yangtze sediment are characterized by clinopyroxene 12 on average and magnetite 7 on average the middle reaches by ilmenite zircon and tourmaline and the local small rivers by fluorite detrital magnetite composition of ti mg v and cr is high in the upper yangtze from the underlying basalt these diagnostic indexes are then used in the pliocene sediment core to extract provenance signal of different yangtze reaches analysis of core sediment of the yangtze delta reveals that sediment provenance of the pliocene was from local small rivers since the beginning of the pleistocene core sediments provenance was similar to that of the middle yangtze tributaries after 1 2 ma high content of pyroxene and magnetite grains that are rich in ti mg v cr imply sediment provenance signals from the upper yangtze sediment provenance shift from short distance sources to more distant sources indicates that the geomorphology of the yangtze delta region has undergone a great transformation since the pliocene this dramatic landform change is likely in response to continuous uplift of the tibetan plateau and accelerated subsidence of the east china coast since the pliocene

climacograptus pungens ruedemann 1904 and the definition of the darriwilian ordovician graptolite genus archiclimacograptus mitchell 1987 the genus archiclimacograptus represents one of the earliest taxa of axonophoran graptolites with geniculate the cae but its current status and evolutionary relationships are difficult to access even after a number of cladistic analyses have been executed archiclimacograptus pungens ruedemann a poorly known little species from the lower darriwilian of eastern north america is interpreted as a possible member of the genus the species belongs to a group of axonophorans with highly asymmetrical proximal end and pattern c astogeny characterized by the lack of an apertural spine on th1 2 rang ing from the levisograptus dentatus biozone darriwilian to the nemagraptus gracilis biozone sandbian specimens are common in north america and the argentinian precordillera but have not been reported from any atlantic faunal realm localities the distribution of the group indicates a restriction to the pacific faunal realm providing the earliest indication of a developing biogeographic differentiation of axonophoran graptolites after their origin in the oceanic biofacies during the upper dapingian to lower darriwilian time interval archiclimacograptus ambiguus is described as a new species resume si le genre archiclimacograptus represente un des taxons les plus anciens de graptolites axonophores dotes de theques geniculees son statut actuel et ses liens evolutionnaires sont difficiles a evaluer et ce meme apres diverses analyses cladistiques archiclimacograptus pungens ruedemann une petite espece meconnue du darriwilien inferieur de l est de l amerique du nord est interprete faisant possiblement partie de ce genre l espece appartient a un groupe d axonophores presentant une extremite proximale tres asymetrique et une astogenie de type c caracterisee par l absence d une epine apertu rale sur th12 dont la distribution va de la biozone a levisograptus dentatus darriwilien a la biozone a nemagraptus graci lis sandbien des specimens sont repandus en amerique du nord et dans la precordillere argentine mais leur presence dans des localites du domaine faunique atlantique n a jamais ete signalee la distribution du groupe indique qu il se limite au domaine faunique pacifique constituant l indice le plus ancien d une differentiation biogeographique des graptolites axo nophores apres leur apparition dans le facies oceanique durant l intervalle allant du dapingien superieur au darriwilien infe rieur archiclimacograptus ambiguus est decrit comme etant une nouvelle espece traduit par la redaction

impacts of human activity on the late holocene development of the subaqueous yangtze delta china as shown by magnetic properties and sediment accumulation rates development of the yangtze delta during the late holocene and its relationship to human activities in the drainage basin was analyzed using data from 16 cores collected from distributaries to the

theoretical and experimental validation of mining enhanced permeability for simultaneous exploitation of coal and gas simultaneous recovery of coal and methane is a promising solution for making reasonable use of energy resources and preventing gas disasters coal mining produces an effect that enhances the permeability of coal and thus paradoxically enhances the ability to collect methane hence existing knowledge about permeability enhancement needs to be improved therefore a new parameter referred to as mining enhanced permeability is proposed to characterize the evolution of permeability for coal and other rocks a theoretical expression for the new parameter is deduced from the tablet fluid model to analyze the mining enhanced permeability of coal mass quantitatively a laboratory test was conducted to simulate the stress environment of the protected layers in protected coal seam mining at the same time a field test was conducted at a working face of mine no 10 at the pingdingshan coal mining group in china the evolution of the volumetric strain and mining enhanced permeability for both protective and protected layers were analyzed quantitatively the loading induced volumetric strain and permeability enhancement in the laboratory showed improvements of 1 59 and 72 26 respectively the mining induced volumetric strain and permeability enhancement also showed improvements of 0 14 and 7 77 respectively the evolution of enhanced permeability agreed with gas flow data observed in both laboratory and in situ tests namely a higher mining enhanced permeability led to high gas flow demonstrating the plausibility of mining enhanced permeability theory based on the tablet fluid model the theory describes the impact of mining on coal permeability and quantitatively captures the evolution of coal permeability in conclusion the proposed theory provides a strong foundation for designing systems to simultaneously recover coal and gas

evaluation of mineral precipitation potential in a spent nuclear fuel repository in this study the potential for mineral precipitation reactions to occur during the excavation disposal backfilling and closure of a deep geological repository for the final disposal of spent nuclear fuel was evaluated with the assistance of hydrogeochemical modelling four modelling exercises corresponding to the main expectable geochemical scenarios in the excavation damaged zone edz throughout repository evolution were carried out and the times for sealing of the discontinuities owing to mineral precipitation in each of them were evaluated and discussed the simulations show that mineral precipitation reactions are thermodynamically feasible in most of the studied cases the main mineral phases potentially responsible for the hydraulic sealing of the edz are calcite and ferric oxyhydroxides being the estimated volumes occupied by the precipitation of calcite between one and three orders of magnitude larger than the volume of precipitating ferric phases the estimated times for complete sealing of the edz may vary between several hundreds to more than 1 million years the shortest sealing times less than 3 000 years are obtained for the mixture of groundwaters from the repository depth with dilute infiltration waters

the huanghe yellow river and changjiang yangtze river deltas a review on their characteristics evolution and sediment discharge during the holocene abstract today asian rivers play an important role in delivering sediment from the land to the oceans however past sediment discharge before human activities modified the landscape is not well known and is estimated to have been roughly one third to one half of the present level chinese rivers have been strongly influenced by human activities and their sediment discharge has changed over the last 6000 years for the study of the long term human impact on rivers and catchment basins chinese rivers provide excellent examples because continuous historical records are available here the characteristics evolution and sediment discharge during the holocene of the deltas of two large chinese rivers huanghe yellow river and changjiang yangtze river are summarized the huanghe and changjiang deltas are different with respect to coastal environments water and sediment discharge the pattern of development of the delta lobe thickness of holocene sediments and basal topography of the incised valleys formed during the last glacial period the huanghe delta is characterized by a high concentration of sediment huge sediment discharge thin holocene deltaic sediments a lateral delta lobe shift and a steep longitudinal profile in its lower reaches the changjiang delta is characterized by a large water discharge a large interseasonal water level change a tide dominated coastal environment continuous seaward progradation with isolated river mouth sand bodies thick holocene sediments and a deep incised valley formed during the last glacial period based on the sediment volume of prograding deltaic sediments over the last 6000 years the sediment discharge of huanghe 1000 years ago is estimated to have been 1 10 8 tons year 1 10 of the present level an abrupt increase occurred at ca 1000 years ago as a consequence of human activities on the loess plateau especially involving cultivation and deforestation moreover the estimated sediment load of huanghe at sanmenxia station prior to 1000 years was 2 7 4 0 10 8 tons year or about 20 15 25 of the present level our recent study estimated that the sediment discharge of changjiang before 2000 years bp was ca 2 4 10 8 tons year total sediment discharge of both rivers before 2000 years bp is estimated to have been 3 4 10 8 tons year or only about 20 of the present level moreover the total sediment load to the lower reaches is estimated to have been 5 6 10 8 tons year or one fourth the present level

recent subsidence and northeast tilting of the nile delta egypt abstract sediment borings collected in the nile delta of egypt many of them radiocarbon dated indicate that the entire northern sector of this major depositional center in the eastern mediterranean is presently subsiding mapping of the base of the holocene deltaic facies which is dated at about 8000 6500 yrs b p reveals that differential lowering of the northern delta plain is preferentially accentuated toward the northeast long term subsidence rates at or near the coast averaged for the mid to upper holocene range from about 0 1 to 0 25 cm yr between alexandria and the north central delta margin rates increase markedly eastward to a maximum of about 0 5 cm yr in the port said manzala lagoon region and this rapid lowering explains the presence of thick marine delta lobe sequences of holocene age in cores in the northeastern delta in contrast only reworked remnants of holocene marine delta lobe deposits of the earlier river nile branches which once flowed to the north and northwest are preserved seaward of the present north delta coast subsidence has induced marked environmental changes particularly with respect to coastal erosion and salt water incursion the asymmetric pattern of saline ground water here attributed in part to the northeast tilt of the delta plain has serious implications for agricultural development in this intensely cultivated region

graptolite biozone correlation charts charts are presented showing the correlation of graptolite biozonations for the lower ordovician to lower devonian i e for the entire stratigraphical range of the planktonic graptoloid graptolites regions chosen are those for which the most detailed biostratigraphical studies have been undertaken for baltica average graptolite zone chron duration appears to vary from c 300000 years ludlow epoch to 2 4 ma lochkovian epoch

lower ordovician arenig llanvirn graptolites from the notre dame subzone central newfoundland many lower paleozoic rocks in the notre dame subzone of central newfoundland are of unknown or imprecise age several new lower ordovician graptolite occurrences are here reported and earlier records revised new graptolite localities in the balsam bud cove formation at snooks arm on the baie verte peninsula previously recorded as early ordovician arenig have yielded an assemblage identical to that found in the middle part of bed 11 of the cow head group western newfoundland indicating a probable lower didymograptus bifidus zone age at corner pond southeast of corner brook an abundant diverse fauna from the corner pond formation indicates a marginally older age for the black shales than those at snooks arm pendeograptus fruticosus zone equivalent to lower bed 11 black shales associated with felsic volcanics and limestone breccia belonging to the cutwell group at lushes bight on long island western notre dame bay which were previously assigned to the widespread black shales of the lawrenc