the permian triassic transition and the onset of mesozoic sedimentation at the northwestern peri tethyan domain scale palaeogeographic maps and geodynamic implications the main aim of this paper is to review middle permian through middle triassic continental successions in european secondly areas of middle late permian sedimentation the permian triassic boundary ptb and the onset of triassic sedimentation at the scale of the westernmost peri tethyan domain are defined in order to construct palaeogeographic maps of the area and to discuss the impact of tectonics climate and sediment supply on the preservation of continental sediment at the scale of the western european peri tethyan basins the upper permian is characterised by a general progradational pattern from playa lake or floodplain to fluvial environments in the northern variscan belt domain areas of sedimentation were either isolated or connected to the large basin which was occupied by the zechstein sea in the southern variscan belt during the late permian either isolated endoreic basins occurred with palaeocurrent directions indicating local sources or basins underwent erosion and or there was no deposition these basins were not connected with the tethys ocean which could be explained by a high border formed by corsica sardinia palaeorelief and even parts of the kabilia microplate the palaeoflora and sedimentary environments suggest warm and semi arid climatic conditions at the scale of the whole study area an unconformity more or less angular is observed almost everywhere between deposits of the upper permian and triassic except in the central part of the germanic basin the sedimentation gap is more developed in the southern area where in some basins upper permian sediment does not occur the large sedimentary supply erosion and or lack of deposition during the late permian as well as the variable palaeocurrent direction pattern between themiddle late permian and the early triassic indicate a period of relief rejuvenation during the late permian during the induan all the intra belt basins were under erosion and sediment was only preserved in the extra belt domains the northern and extreme southern domains in the northern domain the central part of the germanic basin sediment was preserved under the same climatic conditions as during the latest permian whereas in the extreme southern domain it was probably preserved in the tethys ocean implying a large amount of detrital components entering themarinewaters mesozoic sedimentation began in the early olenekian the ephemeral fluvial systems indicate arid climatic conditions during this period three distinct areas of sedimentation occur a northern and southern domain separated by an intra belt domain the latter accumulated sediments during the early middle permian and experienced erosion and or no deposition conditions between the middle late permian and the beginning of mesozoic sedimentation dated as anisian to hettangian at the top of the lower triassic another tectonically induced more or less angular unconformity is observed the hardegsen unconformity which is dated as intra spathian and is especially found in the north european basins this tectonic activity created new source areas and a new fluvial style with marine influences at the distal part of the systems during the anisian and ladinian continental sedimentation was characterised by a retrogradational trend in other words the fluvial system evolved into fluvio marine environments attesting to a direct influence of the tethys ocean in the southern and northern domains both at the end of the olenekian spathian and during the anisian the presence of palaeosols micro andmacrofloras indicate less arid conditions throughout this domain

sedimentary pyrite formation an update sedimentary pyrite formation during early diagenesis is a major process for controlling the oxygen level of the atmosphere and the sulfate concentration in seawater over geologic time the amount of pyrite that may form in a sediment is limited by the rates of supply of decomposable organic matter dissolved sulfate and reactive detrital iron minerals organic matter appears to be the major control on pyrite formation in normal non euxinic terrigenous marine sediments where dissolved sulfate and iron minerals are abundant by contrast pyrite formation in non marine freshwater sediments is severely limited by low concentrations of sulfate and this characteristic can be used to distinguish ancient organic rich fresh water shales from marine shales under marine euxinic conditions sufficient h2s is produced that the dominant control on pyrite formation is the availability of reactive iron minerals calculations based on a sulfur isotope model indicate that over phanerozoic time the worldwide average organic carbon to pyrite sulfur ratio of sedimentary rocks has varied considerably high cs ratios during permo carboniferous time can be explained by a shift of major organic deposition from the oceans to the land which resulted in the formation of vast coal swamps at that time low cs ratios compared to today during the early paleozoic can be explained in terms of a greater abundance of euxinic basins combined with deposition of a more reactive type of organic matter in the remaining oxygenated portions of the ocean the latter could have been due to lower oceanic oxygen levels and or a lack of transportation of refractory terrestrial organic matter to the marine environment due to the absence of vascular land plants at that time

trace fossils from interdune deposits an example from the lower triassic aeolian tumlin sandstone central poland abstract the tumlin sandstone up to 105 m thick is the deposit of a midcontinent extensive at least 1500 km2 dune field it consists of dune deposits and of subordinate intercalations of interdune deposits the latter are represented by horizontally bedded sandstone accumulated in frequently changing conditions on dry damp and wet surface dry surface deposits predominate subordinate but relatively common are damp surface deposits with characteristic adhesion structures and wet surface deposits represented by very thin mudstone layers and horizons of wave ripples which originated in ephemeral ponds the interdune deposits contain numerous trace fossils whose occurrence is almost entirely connected with wet surface and damp surface deposits the dune deposits are devoid of trace fossils the following forms have been recognized arenicolites isp cruziana problematica diplocraterion isp gordia marina planolites montanus planolites isp palaeophycus tubularis tetrapod footprints radial structures shallow double furrows and various oval depressions in places intensive but shallow bioturbation of sediment is observable the trace fossil assemblage is similar to the scoyenia ichnofacies but lacks scoyenia and ancorichnus the assemblage is more comparable to the mixed arenicolites cruziana ichnofacies sensu bromley and asgaard 1979 the invertebrate burrows show an r selected strategy in sediment colonization around the palaeozoic mesozoic transition the highly diversified ichnofauna compared to that of the permian interdune deposits shows increased colonisation of interdunes by an invertebrate mainly arthropod fauna

sedimentation in pull apart basins active examples in eastern turkey the erzincan susehri niksar and lake hazar basins are actively evolving pull apart basins in eastern turkey their structural drainage and depositional systems generally support a pull apart basin sedimentation model based on ancient pull apart basin deposits this model involves marginal coarse grained sedimentation adjacent to master faults axial fine grained sedimentation away from master faults and high sedimentation rates however studies of the turkish pull apart basins suggest the following refinements in the model 1 detailed sedimentary facies patterns and the dominant facies of a pull apart basin vary according to basin shape climate drainage character and volcanic activity depositional environments near fault bounded margins include alluvial fan fan delta and alluvial apron depositional environments in central areas away from fault bounded margins include active braid plain inactive braid plain meander plain salt playa marsh lacustrine mouth bar delta and volcanic 2 i

sediment budget of the yellow river delta during 1959 2012 estimated from morphological changes and accumulation rates abstract the yellow river huanghe is a major sediment source of sediment to the bohai sea and yellow sea resulting in the formation of a large and dynamic delta complex however the river sediment discharge reaching the delta has decreased dramatically since the middle 1960s this study examines the sediment accumulation and morphological changes of the delta complex during 1959 2012 using a repeated bathymetry dataset high resolution seismic profiles and sediment cores obtained in 2012 and 2013 sediment accumulation rates were determined using the downcore concentrations of 137cs and 210pb the average accumulation rates calculated for the delta complex range from 6 9 24 cm y 1 on the delta front slope 1 2 cm y 1 at the toe of the slope and

ammonoid recovery after the permian triassic mass extinction a re exploration of morphological and phylogenetic diversity patterns the explosive ammonoid rediversification after the permian triassic mass extinction is now well understood in terms of taxonomic richness and biogeography using an updated dataset of early triassic ammonoids we compare morphological disparity and taxonomic richness patterns at the regional and global scales disparity evolved similarly at both scales suggesting a global influence of abiotic factors morphological diversification occurred early in the smithian and a marked contraction of the morphospace took place during the end smithian extinction we confirm that trends in disparity and richness were decoupled during the griesbachian and dienerian three macroevolutionary processes may be involved 1 a nonselective extinction at the permian triassic boundary 2 a dienerian constrained radiation with several homeomorphic genera 3 a potential deterministic extinction during the end smithian crisis we also demonstrate a superfamily imprint upon disparity for the spathian when most superfamilies occupied a restricted part of the morphospace sphaerocones were the most affected by the dienerian and end smithian extinction but explanations remain elusive on the one hand this may be linked to widespread harsh conditions at those times on the other hand as the sphaerocones occurred episodically during the early triassic this might be explained by a relaxing of ecological constraints or simply by convergent evolution supplementary materials the database including measurements of specimens illustrated in previously published plates and of unpublished specimens from utah south china and spiti as well as the number of genera present in each studied substage of the early triassic are available at www geolsoc org uk sup18571

fluvial aeolian interactions in a proterozoic alluvial plain example from the mancheral quartzite sullavai group pranhita godavari valley india

structural and tectonic setting of the permo triassic basins of northwest europe abstract the permo triassic basins of nw europe formed by i late orogenic spreading of the variscan mountain belt eventually leading to ocean floor formation in the mid atlantic ii continental rifting propagating south from the arctic and iii thermal subsidence following carboniferous volcanic activity in the north sea spreading values in the northernmost north sea west of shetland and west and southwest of britain are relatively high but the sediments are dominantly continental the permo triassic rifting affected lithosphere thickened during caledonian and variscan orogenesis however subsidence associated with the arctic rifting together with global sea level changes allowed marine incursions into the north sea producing the large zechstein salt basins interference of the different basin formation mechanisms led to a complex three dimensional fault pattern and multidirectional extension across britain and the north sea this fault pattern formed the basic framework for subsequent jurassic and cretaceous basin formation

holocene development of the yellow river s subaqueous delta north yellow sea high resolution seismic profiles from the north yellow sea reveal a 20 40 m thick subaqueous clinoform delta that wraps around the eastern end of the shandong peninsula extending into the south yellow sea this complex sigmoidal oblique clinoform containing an estimated 400 km 3 of sediment overlies prominent relict transgressive surfaces the nearshore topset of the clinoform 50 m contain less than 1 m of holocene sediment with low sedimentation rates 1 mm year in contrast to other clinoforms the shandong clinoform appears to be a compound subaqueous deltaic system with what we interpret to be proximal and distal phases of clinoform development the underlying proximal sequence formed proximally between f11 and 9 2 ka in response to a temporary pause in the rapid postglacial sea level rise after the meltwater pulse 1b mwp 1b and increased discharge from the yellow river to the north yellow sea due to intensification of the summer monsoon a flooding surface appears to separate the proximal and distal phases corresponding to the next rapid sea level rise 9 5 9 2 ka bp mwp 1c since 9 2 ka bp an overlying distal sedimentary sequence has accumulated reflecting the backstepping and shifting river mouth westward to the gulf of bohai some inputs from coastal erosion and nearby small streams may be locally important along shore transport cross shelf advection and upwelling in the north yellow sea have reworked post lgm sediment and have helped maintain the morphology of the clinoform in the shandong mud wedge d 2004 elsevier b v all rights reserved

triassic climates state of the art and perspectives abstract the climate of the triassic period was characterized by a non zonal pattern dictated by a strong global monsoon system with effects that are most evident in the tethys realm this strong monsoonal regime is related to the aggregation of the pangaean supercontinent which by triassic time was already completed climate oscillations existed within this framework the harsh hot house climatic conditions that characterized the late permian and perhaps precipitated the end permian mass extinction were probably maintained during the early triassic and may account for the impoverished but distinctive faunal and floral lower triassic associations although metazoan reef builders were probably the most affected group carbonate production remained high at least in the western tethys realm the middle triassic was characterized locally by humid episodes although their geographical distribution has yet to be clarified the carnian pluvial event marks an episode of increased rainfall documented worldwide was the most distinctive climate change within the triassic different hypotheses have been proposed for its causes changes of atmospheric or ocean circulation driven by plate tectonics a peak of the global monsoon due to maximum continent aggregation or triggering by the eruption of a large igneous province subsequently the late carnian and norian seem to have been climatically stable although minor climatic changes have recently been described even from this time period finally the end triassic extinction event is also associated with climate change specifically warming and increased rainfall but this evidence comes mostly from the northern parts of the central atlantic magmatic province and the global pattern of climate change at the triassic jurassic boundary has still to be resolved many facets of triassic climate are intriguing and deserve further research however palaeoclimate studies on the triassic have so far been carried out only locally with different proxies those proxies will require inter calibration in order to depict correctly the temporal and geographical patterns of triassic climate

recent morphological changes of the yellow river huanghe submerged delta causes and environmental implications abstract the yellow river huanghe submerged delta yrsd has been under the threat of erosion and retreat during the anthropocene due to dramatic climatic and anthropogenic changes in the yellow river basin the analysis of field data shows that over the period of 1977 2005 the changes in climate decrease in precipitation and increase in air temperature and human interventions increase in water diversion projects throughout the watershed have resulted in the sharp reductions of river flow and sediment discharges into the bohai sea consequently over the decadal timescale morphological evolution of the yrsd has gone through three stages i e rapid accumulation 5 77 10 8 m 3 year in 1977 1985 moderate accumulation 3 80 10 8 m 3 year in 1986 1995 and slow accumulation 0 91 10 8 m 3 year in 1996 2005 climatic change within the catchment characterized by the rapid increase of air temperature contributed significantly to the transitions from the rapid accumulation to the moderate accumulation and to the subsequent slow accumulation the decadal morphological changes of the yrsd also show peculiar deposition erosion characteristics over the medium timescale under river input reduction within the three decades the patterns of the main sedimentary body exhibit irregular ellipses with the long axis parallel to the 5 or 10 m isobaths and short axis perpendicular to the isobaths the depocentres of the yrsd are located between the 10 and 15 m isobaths close to the respective river mouths with a high vertical accretion rate of 1 20 m year the time series data of annual volumetric change of the yrsd and river sediment load from 1977 to 2005 further demonstrate significant linear positive relationships between deltaic geomorphic change and fluvial input over shorter timescales annual and 3 year the critical sediment discharges for maintaining the deposition erosion equilibrium state of the yrsd over the annual and 3 year timescales are found to be 1 79 10 8 t year and 1 29 10 8 t year respectively the analysis from the latest hydrological data 2006 2015 suggests that over the decadal timescale the evolution state of the yrsd currently has transitioned from constructive to destructive due to the weakened fluvial input moreover there exists a close quantitative link between the progradation of the yellow river subaerial delta yrad and the yrsd over the five year timescale indicating that every 1 10 8 m 3 year increase of the yrsd s yearly volumetric change will result in a 3 28 km 2 year increase of the yrad s yearly land accretion area and the yrad will reach the extension retreat balance state when yearly morphological change of the yrsd is at 0 73 10 8 m 3 year

north atlantic marine rifting in the early triassic new evidence from east greenland two early triassic marine rifting events have been recognized in new outcrop data from east greenland increasing our understanding of this important tectonic episode in the development of the ne atlantic norwegian greenland sea a detailed ammonoid stratigraphy together with stratigraphic and radiometric evidence show that the first rifting event took place in the early griesbachian this event was largely confined to major basin margin faults the second rifting event which involved splay faulting and intra basinal fault block tilt is dated as late griesbachian deposition in east greenland took place in half grabens dominated by deep water gravity flow sandstones and mudstones as well as shallow marine conglomerates and sandstones similarly recent core data from offshore mid norway show that deposition on the eastern margin of the norwegian greenland sea took place in deep marine settings dominated by gravity flows this suggests that the early triassic marine realm extended from east greenland to the present day norwegian coastline and that the marine rift basin was significantly wider than previously thought

aeolian sands in continental red beds of the middle buntsandstein lower triassic at the western margin of the german basin abstract aeolian sands occur widespread in continental red beds of the middle buntsandstein lower triassic at the western margin of the german basin middle europe in the eifel area cross bedded sands were mainly deposited by grainfall on lee slopes of barchanoid type dunes in unimodal wind regime in both low energy and high energy environments occasionally sets are internally truncated by reactivation surfaces crest height of solitary set dunes varies in the range of some meters locally sequences of cosets both of tabular planar and wedge planar type capped by flat or gently windward dipping topset beds represent larger dune complexes of about 10 20 m in height and at least 80 100 m in lateral extent horizontal laminated deposits originated as sand sheets in interdune areas the dune sands were deposited by trade winds of the northern hemisphere in low palaeolatitude predominantly by southeasterly and southwesterly trade winds in summer when the intertropical convergence zone was shifted to the north aeolian sands built up an extensive dune belt in the eifel intersected by braided to anastomosing rivers fluviatile incursions or heavy ephemeral rainfall led to aquatic redeposition of aeolian sediments and origin of shallow lakes in interdune depressions distribution of aeolian and fluviatile sediments in karlstal schichten is different in the southern western and northern eifel middle buntsandstein sequence in the southern eifel reflects an evolution of the fluviatile depositional environment also incorporating the occurrence and distribution of aeolian sands evolution is characterized by increasing spacing and sinuosity of channels weakening supply of coarse detritus from the source areas and decreasing braiding of the river systems aeolian sands occur in the final phase of this evolution which led from local alluvial fans via cobbly and pebbly braided rivers to sandy braided streams and finally to an intertonguing of aeolian dunes and braided to anastomosing rivers matching with the climax of regional diversification of depositional milieu the aeolian sand sea in the eifel covered an area of nearly 2500 km2 at the time of its largest extension the dune belt ended in the northern eifel the alternating sequence passed into an entirely alluvial succession which graded northwards by continuously diminishing grain size into the central playa lacustrine to marine sediment series in northwest germany palaeogeography sedimentology and genesis of the middle buntsandstein at the western margin of the mid european basin and of rotliegendes in northwest germany appear to be partially similar as is revealed by certain characteristics of the palaeogeographical reconstructions concurrence of middle buntsandstein palaeogeographical models for both eifel and the whole german basin most clearly delineates the key position of the eifel for interpretation of the buntsandstein sedimentary environment and the palaeogeography in middle europe

the early triassic ammonoid recovery paleoclimatic significance of diversity gradients ammonoids recovered much faster than other marine shelly invertebrates after the end permian mass extinction based on a refined global data set at the basin level we investigate the paleobiogeographical global latitudinal and longitudinal diversity patterns in terms of climatic changes during the early triassic such analysis differs from already published qualitative or quantitative studies in that it estimates faunal patterns and endemicity at an ecologically meaningful level of spatial resolution i e at the basin level during the early triassic the global first order trend in increasing ammonoid diversity was accompanied by a progressive change from cosmopolitan to latitudinally restricted distributions this led to the emergence of a clear latitudinal diversity gradient during most of the smithian and spathian stages which entails increased steepness of the sea surface temperature gradient during the late early triassic however two brief episodes of ammonoid cosmopolitanism combined with low global diversity interrupted the first order increasing trend at the very beginning of the smithian and at its very end the longitudinal analysis of smithian distributions indicates a westward decrease of diversity within the tethys which faded away during the spathian analysis of endemicity indicates a rapid biogeographical maturing and structuring of faunas concomitant with the edification of the latitudinal diversity gradient

210pb 137cs and 239 240pu in east china sea sediments sources pathways and budgets of sediments and radionuclides profiles of 210 pb 137 cs and 239 240 pu measured in 83 sediment cores collected from various sedimentary regimes in the east china sea were analyzed to elucidate the sources routes and budgets ofsediments as well as these radionuclides distributions ofsedimentation rates and nuclide inventories reveal alongshore transport ofsediments 137 cs and 239 240 pu from the mouth of the yangtze river toward the south largely confined to the inner shelf area water depth 6 70 m mass balance calculations suggest that the east china sea is a sink for the particle reactive 210 pb and 239 240 pu with about one sixth oftheir sedimentary budgets supplied via boundary scavenging in contrast due to lower affinity of 137 cs for particles and rapid turnover of the shelf water the east china sea serves as a source for 137 cs about two thirds ofthe cumulative input of 137 cs have been transported out ofthe east china sea leaving the remaining one third stored in the bottom sediments and the overlying water column as for the sediment budget mass balance cannot be established due to a shortfall in sediment supply of more than 30 based on a comparison between input terms documented thus far and the sedimentation flux derived from this study it is very likely that we have overestimated the sediment burial flux or that long distance transport from the yellow river s dispersal system to the east china sea is underestimated alternatively the imbalance could be explained by the discrepancy between sediment input and output on decadal to centennial timescales 7 2002 elsevier science b v all rights reserved

meso cenozoic morphotectonic evolution of southern norway neogene domal uplift inferred from apatite fission track thermochronology apatite fission track aft thermochronology of precambrian and paleozoic basement samples from southern norway reveals a post paleozoic exhumation history related to offshore mesozoic and cenozoic extensional basin development the data indicate two major phases of rapid exhumation a first mesozoic phase started in the triassic 220 ma in the east and south of the study area and migrated to the west where jurassic 160 ma ages of exhumation predominate a second event is indicated by thermal history modeling of aft ages and track length distributions it is inferred to be neogene in age initiated at about 30 ma and it produced a domal pattern of aft isochrons which follow present day topographic elevation youngest aft ages 100 ma are encountered at sealevel in the inner fjords near the areas of highest topography ages increase radially outward to the mountain peaks and the coastlines forward modeling of age elevation patterns suggests that mesozoic geothermal gradients were 10 15 c km higher than the present value of 20 c km during the triassic and jurassic a total of 1 3 3 5 km of overburden was removed from the study area assuming a 30 c km geothermal gradient for that period we attribute this to rift margin erosion as a result of erosional base level lowering and flank uplift as evidenced by thick continental clastic sequences deposited in triassic jurassic half grabens in the north sea basins we propose that 1 5 2 5 km of neogene exhumation were a result of late stage domal uplift this is supported by basinward dipping pre neogene strata in the basins surrounding southern norway and the infill of a 1 to 2 km thick neogene sediment wedge containing various internal unconformities domal uplift probably started in the late oligocene may have been amplified in the pliocene and was overprinted by plio pleistocene glacial erosion maximum neogene tectonic uplift is estimated at approximately 1 1 5 km radially decreasing outward to a value 500 m near the shoreline neogene domal uplift is coincident with oligocene and pliocene plate reorganizations in the north atlantic similar neogene domes are found around the norwegian greenland sea i e svalbard and the barents sea northern norway east greenland suggesting a regional tectonic cause the onset of neogene uplift postdates major volcanism and continental breakup by 25 m y and predates plio pleistocene glaciations its origin is possibly a combination of induced mantle convection resulting in thermal erosion of the lithosphere and the operation of intraplate stresses

tectonic and climatic control of triassic sedimentation in the beryl basin northern north sea the beryl basin embayment occupies a central position along the viking graben of the northern north sea and has been a hydrocarbon play since the early 1970s detailed analysis reveals a complex half graben that was established during a rift phase of development that occurred in the early triassic teist formation after which a long period of thermal subsidence lomvi and lunde formations provided accommodation for in excess of 1000 m of sediment the teist formation sediments are complex they include shales sands and conglomerates and their superimposition on zechstein salts is indicative of both uplift and the development of a moderate relief they give way to the comparatively clean and occasionally pebbly sands of the lomvi formation for which an analysis of both bedding and texture suggests deposition by a westerly directed river system draining the hanging wall ramp the lunde formation records the spreading influence of a bajada playa complex and its eventual conversion to a more persistent lake the growing importance and eventual dominance of the succession by lacustrine sediments gives clear indication of a change in climate and this has been attributed to the rapid northward drift of pangea during the triassic period

analogue models of pull apart basins sandbox analogue models of pull apart basins that developed in sedimentary strata above releasing steps in underlying basement faults are characterized by rhombic basins that are flat bottomed box grabens with a subhorizontal synkinematic basin infill steep to nearly vertical sigmoidal oblique slip and segmented oblique extensional faults are the dominant bounding structures of the pull apart basins cross basin short cut faults link the offset principal displacement zones that are characterized by flower structure development the structural architectures of the physical models compare directly in form and dimensions to natural examples of strike slip pull apart basins

sedimentary records off the modern huanghe yellow river delta and their response to deltaic river channel shifts over the last 200 years abstract the modern huanghe yellow river delta sedimentary complex has developed since 1855 when the lower river channel migrated northward from the yellow sea to the bohai sea as a result the river laden sediment accumulated rapidly on the lowlying plain and formed the mega delta here we present high resolution sedimentary sequences based on 137 cs and 210 pb dating and grain size parameters of two sediment gravity cores collected near the present river mouth core a11 and in adjacent laizhou bay core a26 based on these sedimentary sequences the different responses of the sediment records to natural and artificial channel shifts are presented the average sedimentation rates of the two cores a11 1951 2006 and a26 1808 2006 were estimated to be 2 25 cm year and 0 80 cm year respectively the results indicated that the geometry of the delta e g the location of river mouth and changing coastline and sediment supply from the river played an important role in the sedimentation of the subaqueous delta the channel shifts in 1976 and 1996 shortened the distances from the river mouth to the location of core a11 resulting in the local accumulations of relatively coarse particles from the river mouth the sedimentation of core a26 indicated four major channel shifts in 1855 1904 1947 and 1976 when the river mouth approached the core location the accumulated sediment became finer otherwise the active resuspension due to strong hydrodynamics resulted in the accumulation of coarser sediment the sediment records preserved in the two gravity cores illustrated different sedimentary responses to the lower channel shifts of the huanghe and sediment supply from the river at centennial scales which is critical to understanding the evolution of the modern huanghe delta in the past and to predicting the future trend

diagenesis in oxidising and locally reducing conditions an example from the triassic skagerrak formation denmark abstract diagenetic changes in red and white parts of the skagerrak formation triassic from onshore wells in denmark were analysed by scanning electron microscope electron microprobe and petrographic microscope in reflected and transmitted light the diagenetic sequences of the red and white parts of the skagerrak formation are in many ways the same early infiltration clays followed by precipitation of caliche calcite dolomite mixed layer illite smectite quartz feldspar kaolin minerals illite chlorite and anhydrite with increasing burial differences between the red and white parts of the skagerrak formation comprise oxidation stage in detrital minerals oxidation of glauconite in the red part and reduction of biotite in the white part the presence of eogenetic authigenic minerals pyrite and poikilotopic calcite in the white part hematite and red coatings in the red part the amount of mesogenetic authigenic kaolin minerals larger in the white part the chemistry of mesogenetic authigenic chlorite mg rich in the red part and fe rich in the white part and the preservation stage of detrital opaque minerals magnetite hematite chromite ilmenite show none or minor alteration in the red part whereas they have been almost completely altered in the white part as the differences between red and white areas are found both in early eogenetic and in mesogenetic authigenic minerals different oxidising conditions must have prevailed immediately after the deposition and continued into burial oxidising conditions were dominant in the arid triassic climate and the widespread red colour of the skagerrak formation was probably formed during early diagenesis due to precipitation of iron oxides or hydroxides locally reducing areas were formed probably by oxidation of organic material precipitation of oxidised iron minerals was thus prevented and the original white colour was preserved reducing conditions prevailed until the reducing agent was exhausted then an outer rim of the reduction spot might locally have been secondarily oxidised these changing redox conditions explain the occurrence of hematized authigenic pyrite and crandallite group minerals in red areas

ocean stagnation and end permian anoxia ocean stagnation has been invoked to explain the widespread occurrence of organic carbon rich laminated sediments interpreted to have been deposited under anoxic bottom waters at the time of the end permian mass extinction however to a first approximation stagnation would severely reduce the upwelling supply of nutrients to the photic zone reducing productivity moreover it is not obvious that ocean stagnation can be achieved numerical experiments performed with a three dimensional global ocean model linked to a biogeochemical model of phosphate and oxygen cycling indicate that a low equator to pole temperature gradient could have produced weak oceanic circulation and widespread anoxia in the late permian ocean we find that polar warming and tropical cooling of sea surface temperatures cause anoxia throughout the deep ocean as a result of both lower dissolved oxygen in bottom source waters and increased nutrient utilization buildup of quantities of h2s and co2 in the late permian ocean sufficient to directly cause a mass extinction however would have required large increases in the oceanic nutrient inventory

the nature origin and accumulation of loess abstract loess can be defined simply as a terrestrial clastic sediment composed predominantly of silt size particles which is formed essentially by the accumulation of wind blown dust there are three fundamental requirements for its formation 1 a sustained source of dust 2 adequate wind energy to transport the dust and 3 a suitable accumulation site most loess has been modified to some degree by local reworking bioturbation and syn depositional weathering but a process of loessification is not necessary for a dust deposit to qualify as loess the terms primary loess and secondary loess have previously been used to described wind deposited loess and redeposited loess respectively but it is more accurate to describe material reworked and redeposited by non aeolian processes as loess derived colluvium or loess derived alluvium during the quaternary loess formed in three main situations 1 mid continental shield areas beyond the limits of ice sheets periglacial loess 2 on the margins of high mountain ranges perimontane loess and 3 on the semi arid margins of some lowland deserts peridesert loess peridesert loess is relatively poorly developed partly due to the limited efficiency of silt generating mechanisms in low land deserts compared with glaciation but also important is the tendency in arid areas for dust to be dispersed over a wide area and to be rapidly reworked after deposition particularly in areas which experience frequent climatic changes the remarkably thick loess of china and central asia results from an unusual combination of conditions which has persisted for much of the last 2 3 million years namely rapid uplift of the tibetan plateau and surrounding mountain ranges high rates of sediment production and supply to adjacent basins a strong northwesterly and westerly wind regime and the existence of effective dust traps downwind of the source regions

tide modulated hyperpycnal flows off the huanghe yellow river mouth china few hyperpycnal flows have ever been observed in marine environments although they are believed to play a critical role in sediment dispersal within estuarine and deltaic depositional systems the paper describes hyperpycnal flows observed in situ off the huanghe yellow river mouth their relationship to tidal cycles and the mechanisms that drive them simultaneous observations at six mooring stations during a cruise off the huanghe mouth in the flood season of 1995 suggest that hyperpycnal flows observed at the river mouth are initiated by high concentrations of sediment input from river and modulated by tides hyperpycnal flows started near the end of ebb tides when near bottom suspended sediment concentration ssc increased rapidly and salinity decreased drastically an inverse salt wedge the median grain size of suspended particles within the hyperpycnal layer increased causing strong stratification of the suspended sediments in the water column towards the end of flood tides the hyperpycnal flow attenuated due to frictions at the upper and lower boundaries of the flow and tidal mixing which collapsed the stratification of the water column both sediment concentration and median grain size of suspended particles within the bottom layer significantly decreased the coarser sediment particles were deposited and the hyperpycnal flows stopped the intra tidal behaviors of hyperpycnal flows are closely associated with the variations of ssc salinity and stratification of the water column as nearly 90 of riverine sediment is delivered to the sea during the flood seasons when hyperpycnal flows are active hyperpycnal flows at the huanghe mouth and the river s high sediment loads have caused rapid accretion of the huanghe delta copyright 2010 john wiley sons ltd

stepwise morphological evolution of the active yellow river huanghe delta lobe 1976 2013 dominant roles of riverine discharge and sediment grain size abstract the presently active yellow river huanghe delta lobe has been formed since 1976 when the river was artificially diverted the process and driving forces of morphological evolution of the present delta lobe still remain unclear here we examined the stepwise morphological evolution of the active yellow river delta lobe including both the subaerial and the subaqueous components and illustrated the critical roles of riverine discharge and sediment grain size in dominating the deltaic evolution the critical sediment loads for maintaining the delta stability were also calculated from water discharge and sediment load measured at station lijin the last gauging station approximately 100 km upstream from the river mouth the results indicated that the development of active delta lobe including both subaerial and subaqueous components has experienced four sequential stages during the first stage 1976 1981 after the channel migration the unchannelized river flow enhanced deposition within the channel and floodplain between lijin station and the river mouth therefore the critical sediment supply calculated by the river inputs obtained from station lijin was the highest however the actual sediment load at this stage 0 84 gt yr was more than twice of the critical sediment load 0 35 gt yr for sustaining the active subaerial area which favored a rapid seaward progradation of the yellow river subaerial delta during the second stage 1981 1996 the engineering facilitated channelized river flow and the increase in median grain size of suspended sediment delivered to the sea resulted in the critical sediment load for keeping the delta stability deceasing to 0 29 gt yr the active delta lobe still gradually prograded seaward at an accretion rate of 11 9 km2 yr at this stage as the annual sediment load at lijin station was 0 55 gt yr from 1996 to 2002 the critical sediment load further decreased to 0 15 gt yr with the sediment grain size increased to 22 5 m however the delta suffered net erosion because of the insufficient sediment supply 0 11 gt yr in the most recent stage 2002 2013 the intensive scouring of the lower river channel induced by the dam regulation provided relatively coarser sediment which effectively reduced the critical sediment load to 0 06 gt yr much lower than the corresponding sediment load at lijin station 0 16 gt yr consequently the subaerial yellow river delta transitioned to a slight accretion phase overall the evolution of the active yellow river delta is highly correlated to riverine water and sediment discharge the sediment supply for keeping the subaerial delta stability is inconstant and varying with the river channel morphology and sediment grain size we conclude that the human impacted riverine sediment discharge and grain size composition play dominant roles in the stepwise morphological evolution of the active delta lobe

the structural evolution of the northern viking graben and its bearing upon extensional modes of basin formation recent advances in the understanding of rift basin formation coupled with the increasing public availability of seismic and well data across the northern viking graben 60 61 n have enabled a detailed analysis of its development two rifting episodes can be recognized late permian early triassic and bathonian ryazanian major regional unconformities thought to be primarily tectonic rather than eustatic in origin separate and subdivide the rifting episodes the earlier episode involved extension about a n s axis ensuing triassic mid jurassic thermal subsidence was accommodated on steep faults during the later episode a new ne sw fault trend was superimposed on pre existing patterns major block rotation marking active rifting ceased at the end of the ryazanian during the second post rift episode there was a progressive migration of active faulting towards the basin margins and as a result a widening with time of the area undergoing subsidence asymmetric subsidence of the central part of the basin was hinged at the western margin of the horda platform and accommodated to the nw on major faults within the tampen spur factors for the second rifting episode were calculated both by relating subsidence to extension and by measuring observed extension values calculated by both methods increase consistently towards the basin axis for both rifting and thermal subsidence phases but are greater for the latter phase subsidence patterns are similar for both rifting and thermal subsidence episodes so that there is vertical stacking of relatively thick sequences in the axis of the northern viking graben these factors preclude the application of models involving uniform and non uniform stretching and also preclude oblique extension depth dependent stretching is preferred

sediment accumulation in a modern epicontinental shelf setting the yellow sea sediment accumulation in the yellow sea epicontinental shelf environment is investigated on 100 yr and 1000 yr time scales using 210pb and 14c geochronologies the distribution of modern 210pb accumulation rates in the yellow sea reveals that the loci of modern huanghe sediment accumulation are the topset 1 2 mm yr foreset 4 9 mm yr and proximal bottomset deposits 2 4 mm yr of the shandong subaqueous delta which extends south from the shandong peninsula 210pb rates in the distal bottomset deposits of the subaqueous delta in the central and southern yellow sea are generally low 0 3 0 9 mm yr a sediment budget demonstrates that between 9 15 of the annual huanghe discharge is accumulating in the yellow sea about two thirds of this sediment is accumulating in the topset foreset and proximal bottomset deposits of the shandong subaqueous delta with the remaining third accumulating as widespread distal bottomset deposits 14c age dates of subaqueous delta sediments indicate that the thick 40m clinoform structure formed predominantly between 6200 and 4060 yrs b p at rates approaching 20 mm yr observations in the yellow sea as well as on the amazon and ganges brahmaputra shelves demonstrate that subaqueous deltaic stratigraphy is the general rule where major rivers enter energetic shelves whether epicontinental or pericontinental the development of extensive bottomset deposits may be restricted to epicontinental shelf environments and may be diagnostic of sedimentation in this type of setting

a unique yellow river derived distal subaqueous delta in the yellow sea abstract newly acquired high resolution chirp sonar profiles reveal a unique yellow river derived alongshore distributed bidirectional landward and seaward across shelf transported omega shaped distal subaqueous deltaic lobe deposited around the eastern tip of the shandong peninsula in the yellow sea this clinoform deposit directly overlies the postglacial transgressive surface featured by convex up seafloor morphology up to 40 m thick locally radiocarbon 14 dates from the underlain pre holocene and transgressive sediments indicate this distal lobe has formed since the middle holocene highstand under a relatively stable sea level this along shelf distributed distal clinoform has been deposited mainly by the resuspended yellow river sediments carried down by the coastal current interacting with the local waves tides and upwelling collectively over the past 7000 years nearly 30 of the yellow river derived sediment has been re suspended and transported out of the bohai sea into the yellow sea overall the yellow river derived sediment could reach the 80 m water depth in the central south yellow sea about 700 km from the river mouth in contrast a very small fraction of the modern riverine sediment could escape the outer shelf or reach the okinawa trough

coastline change of the yellow river estuary and its response to the sediment and runoff 1976 2005 abstract the dramatic decreases in runoff and sediment have great impacts on erosion deposition variation in the yellow river estuary this study extracted mean high tide lines of the yellow river estuary from mss tm and etm data from 1976 to 2005 and explored relationships between the accretion erosion of land and the runoff and sediment load of the yellow river the results showed that the general pattern of accretion erosion of the entire estuary was divided into four stages rapid accretion stage 1976 1986 accretion erosion adjustment stage 1986 1996 slow erosion stage 1996 2003 and slow accretion stage 2003 present for maintaining the annual balance of the entire estuary 1976 2005 and q8 estuary most recent course of the qingshuigou estuary from 1996 to 2005 critical annual runoff and sediment load are 140 36 108 m3 year 1 and 3 31 108 t year 1 and 85 0 108 m3 year 1 and 1 63 108 t year 1 respectively in the future decades the q8 estuary is likely to maintain its shape and area balance or have a little accretion but the entire estuary could be in an eroding state

latest caledonian to present tectonomorphological development of southern norway abstract the regional resultant stress field of the northeastern north atlantic has shifted significantly throughout the phanerozoic in fennoscandian parts of the caledonian orogen mountain building which was characterized by nw se contraction reference to present north was followed by a collapse with transport both parallel and transverse to the mountain chain the late palaeozoic mesozoic saw several stages of e w to nw se extension varying in time and position local episodes of inversion are traceable in some cases particularly in connection with deep seated and long lived zones of weakness the cenozoic has to a larger degree been affected by compression including folding and basin inversion again some of the more pronounced effects of local inversion are related to pre existing fault systems neogene uplift of the western mountainous area in scandinavia can be unravelled by potential field study aft data and reflection seismic sections assuming that the region is close to isostatic equilibrium the uplifted areas must be supported at depth by substantial volumes of low density material within the crust or the mantle close to the crust mantle interface or close to the lithosphere asthenosphere interfaces a series of nw se oriented cross sections representing successive stages of development from the late caledonian to present were prepared and used to analyse the tectonomorphological development as related to the shifting stress configurations three stages are inferred stage 1 devonian late permian denudation of the caledonian mountain chain during the latest stage of closing of the iapetus ocean in early to mid devonian times the caledonian mountain chain reached its maximum elevation of perhaps as much as 8 9 km including the foreland basins to the east the average topographic gradient of the eastern flank may have been in the order of 1 3 the denudation of the caledonian mountains continued into the permian and by the end of the permian the mountain system was more or less obliterated with a gradient of the eastern flank probably continued to fall to less than 0 1 stage 2 triassic late cretaceous tectono thermal uplift of central south norway uplift of central south norway was rejuvenated in triassic times and continued throughout the jurassic and early cretaceous the gradient of the eastern flank increased to a maximum of approximately 0 15 and master structural elements like the laerdal gjende olestol fault complex again played important roles in the development stage 3 tertiary present renewed tectono thermal activity and post glacial rebound a second phase of post caledonian tectono thermal uplift of south central norway started in oligocene time again increasing the gradient of the eastern flank of south norway around 0 2

correlation of sandstones using heavy minerals an example from the statfjord formation of the snorre field northern north sea correlation of sandstones using heavy minerals is dependent on the recognition and quantification of provenance sensitive parameters suitable criteria include ratios of minerals that have similar hydraulic and diagenetic behaviour and properties of populations of individual mineral species sandstones of the statfjord formation in the snorre field display marked variations in their heavy mineral assemblages although hydraulic and diagenetic processes have played some part in generating these variations major changes in the nature of the source material can be detected on the basis of heavy mineral ratio and varietal data these changes in sand provenance can be used to produce a detailed stratigraphic breakdown of the sequence and to correlate from well to well eleven heavy mineral zones have been recognised on the basis of variations in monazite zircon garnet zircon and rutile zircon ratios on the incoming of chloritoid and on the composition of garnet populations the marked changes in provenance result from the proximity of the depositional location to the hinterland and it is considered unlikely that the detailed correlation made in the snorre field area applies to statfjord sandstones in other parts of the northern north sea however there is evidence for some degree of allogenic control on the heavy mineral variations and therefore some events may have regional significance

interaction of permo triassic and jurassic extensional fault blocks during the development of the northern north sea the main structural elements resulting from late permian early triassic extension have been resolved across the total width of the northern north sea the northern segment of the basin north of 61 n bounded to the west by the hutton fault and to the east by the norwegian mainland was occupied by four westerly tilted half grabens 25 35 km in width prior to jurassic extension the central segment of the basin 60 20 61 n exhibits a full graben beneath the jurassic horda platform flanked by half grabens tilted towards the basin margins the change in permo triassic fault block configuration defining structural domains is largely constrained by a basement discontinuity which runs diagonally ne sw across the basin maximum jurassic extension is represented by several centres of subsidence aligned nne ssw across a n s oriented and broader permo triassic basin jurassic extension was concentrated within the viking graben proper south of 60 n which in this area is represented by single westerly tilted en echelon half graben segments 20 25 km wide the area affected by jurassic extension becomes progressively wider to the north again governed by the basement discontinuity eventually encompassing the total width of the basin c 200 km north of 61 n the central segment of the northern north sea displays the greatest contrast in permo triassic and jurassic structural styles and basin geometry jurassic stretching and faulting was negligible to the east horda platform precisely the area which had been the site of maximum permo triassic stretching and fault activity it has generally been assumed that jurassic fault configuration along the eastern margin of the central segment of the viking graben to a large extent reflects the reactivation of major permo triassic faults this study demonstrates the interference of permo triassic and jurassic basin geometries in this area due to major faults of the two generations dipping in opposite directions as a consequence the e tilted oseberg fault block of jurassic origin and c 20km in width is underlain by a wider c 35 km and w tilted permo triassic fault block

structural styles and depositional architecture in the triassic of the ninian and alwyn north fields implications for basin development and prospectivity in the northern north sea abstract interpretation of well calibrated three dimensional seismic volumes sedimentological analysis and electrical well log correlations from the ninian and alwyn north fields challenge the long held view that mid late jurassic extensional faults in the east shetland basin represent a simple reactivation of older triassic fault systems restoration for the effects of the younger predominantly eastward dipping mid late jurassic structures clearly demonstrates that triassic precursors had a steep westerly dip in contrast to the eastern flank of the viking graben e g troll and oseberg areas where the west dipping triassic structures are reutilised in the mid late jurassic those of the east shetland basin have largely been dissected and rotated during the later event those west dipping faults that did see later movement appear to have simply acted as minor antithetic structures to the throughgoing east dipping ones the triassic normal fault patterns actively controlled sediment thicknesses and facies distribution within the lunde and teist formations in the basin use of seismic stratigraphic surfaces calibrated by biostratigraphy and chemostratigraphic markers provides strong evidence that the triassic depocentres are spatially offset from their mid late jurassic counterparts the combination of structural stratigraphic and sedimentary effects reveal the existence of an emergent deeper triassic play opportunity in footwall locations to the mid late jurassic normal faults which has the potential to extend the life of what is otherwise mature acreage

sediment accumulation and budget in the bohai sea yellow sea and east china sea abstract sediment accumulation and budget in the continental margins provides abundant information of source sink processes from the land to the sea including weathering human activities and sedimentary environment here we show the distribution of mud areas modern sedimentation rates and sediment budget in the bohai sea yellow sea and east china sea using grain size data of 18 000 surface sediment samples and 210 pb data from 413 sites we identify five areas with sediments mainly composed of fine grained fractions mean grain size 6 and find a relatively high sedimentation rates of 1 5 mm yr in the mud areas near the yellow and yangtze river deltas sedimentation reaches 95 0 mm yr approximately 1185 4 10 6 tons of fine grained sediment accumulate annually in the mud areas of the east china seas atmospheric deposition contributes 6 tons yr while the riverine sediment inputs account for 75 917 10 6 tons yr the remainder comes from all other sources including coastal erosion and resuspension of bottom sediments in addition 45 of the fluvial sediment supply deposits on the subaerial delta 40 50 is trapped on the subaqueous delta and shelf and the remainder

onset of asian desertification by 22 myr ago inferred from loess deposits in china the initial desertification in the asian interior is thought to be one of the most prominent climate changes in the northern hemisphere during the cenozoic era1 2 3 4 but the dating of this transition is uncertain partly because desert sediments are usually scattered discontinuous and difficult to date here we report nearly continuous aeolian deposits covering the interval from 22 to 6 2 million years ago on the basis of palaeomagnetic measurements and fossil evidence a total of 231 visually definable aeolian layers occur as brownish loesses interbedded with reddish soils this new evidence indicates that large source areas of aeolian dust and energetic winter monsoon winds to transport the material must have existed in the interior of asia by the early miocene epoch at least 14 million years earlier than previously thought3 5 regional tectonic changes and ongoing global cooling are probable causes of these changes in aridity and circulation in asia

evolution of the oseberg fault block in context of the northern north sea structural framework abstract the central segment 60 20 61 n of the northern north sea 170 km in width demonstrates contrasting basin geometries related to permo triassic and jurassic rift episodes in the oseberg area representing a part of this segment major faults of two generations dip in opposite directions as a consequence the e tilted oseberg fault block of jurassic origin ca 20 km in width is underlain by a wider ca 35 km w tilted permo triassic half graben the early jurassic thickness distribution was governed by a westerly palaeotilt mild extensional tectonics influenced early jurassic rhaetian aalenian deposition whereas the middle late jurassic main rift episode is expressed by an accelerated fault related subsidence from the late bajocian during the middle late jurassic the oseberg area evolved through a series of high frequency rift phases characterized by rotational tilt events separated by periods during which extension was less severe this allows the subdivision of the jurassic stretching episode into distinct rift phases 4 6 myrs which involved smaller scale units corresponding to rotational tilt events 1 2 myrs the large scale pattern of middle late jurassic syn rift infill is overall one of upwards fining reflecting a deepening trend as the rift evolved syn rotational sediment architecture related to a single rift phase shows systematic variations from a threefold shallow marine sandstone mudstone sandstone motif tarbert fm through a twofold shallow marine sandstone mudstone motif heather fm to a twofold deep marine conglomerate sandstone mudstone motif draupne fm the vertical stacking of these syn rotational packages reflects an inability of sediment supply to keep pace with the rift related subsidence and the temporal evolution from a sediment balanced through a sediment underfilled to a sediment starved rift basin