sedimentary facies and radiocarbon dates of the nam dinh 1 core from the song hong red river delta vietnam abstract the song hong red river delta which is located on the western coast of the gulf of bac bo gulf of tonkin in the south china sea is characterized by three morphological systems that are clearly distinguished spatially fluvial tidal and wave dominated we obtained a 70 m long core of sediments the nam dinh 1 core from the central part of the delta in 1999 this paper presents the first detailed description of sedimentary facies with high resolution radiocarbon dating for the latest pleistocene holocene sediments of the song hong delta the core sediments were divided into three units on the basis of the sediment facies in ascending order unit 1 fluvial sediments consisting of fining upward gravels to clay unit 2 coarsening upward marine clay to shelly sand and unit 3 coarsening upward marine clay and laminated sand twenty one radiocarbon dates showed that the core succession was deposited after the last glacial maximum lgm the ages were 15 11 cal kyr bp for unit 1 11 9 cal kyr bp for unit 2 and 8 0 cal kyr bp for unit 3 these data indicate that sediments were deposited in transgressive fluvial estuarine to regressive deltaic environments formed in the central delta plain of the song hong after the lgm in response to sea level changes

quartz cementation in late cretaceous mudstones northern north sea changes in rock properties due to dissolution of smectite and precipitation of micro quartz crystals abstract late cretaceous mudstones from two wells located in the northern north sea and the norwegian sea have been examined with respect to quartz cement two different types of quartz cement type 1 and type 2 have been identified using sem eds cl analysis of drill bit cuttings at depths 2370 2670 m 80 85 c type 1 appears as relatively large aggregates 30 100 m of depth temperature related crypto or microcrystalline to macrocrystalline irregular quartz cement formed by local re crystallization of biogenic silica the cl responses of type 1 quartz cement give a clear indication of an authigenic origin type 2 quartz cement represents relatively high amounts of extremely fine grained micro sized 1 3 m crystals embedded as discrete short chains or small clusters nests within the illitized clay matrix the cl responses of micro quartz crystals indicate an authigenic origin the micro quartz is most probably sourced from silica released during the smectite to illite dissolution precipitation reaction the petrographic evidence indicates that most of the silica released by the smectite to illite reaction has not been exported out of the mudstones the silica released produce a subtle inter connected micro quartz network interlocked with aggregates of micro quartz and authigenic clay crystals this micro quartz cementation process causes a significant and sharp change in the mudstone stiffness at the onset of the chemical compaction regime this is indicated by an abrupt increase in well log velocity vp and change in seismic facies close to 2500 m 80 85 c

modelling of hydrocarbon generation in the cenozoic song hong basin vietnam a highly prospective basin abstract the cenozoic song hong basin situated on the northern part of the vietnamese shelf has been only sporadically explored for hydrocarbons a review of the results of the exploration efforts so far shows that the distribution of potential source rocks and their time of hydrocarbon generation are the critical risks for finding commercial amounts of hydrocarbons in the song hong basin including the hanoi trough the rocks most likely to have source potential are 1 oil prone eocene lower oligocene lacustrine mudstones and coals 2 oil and gas prone middle miocene coal beds 3 gas prone upper oligocene lower miocene coals and 4 gas and oil prone miocene marine mudstones to assess the time of hydrocarbon generation from these units relative to the formation of traps the generation history was modelled at 32 well and pseudo well locations the modelling demonstrates that the two first mentioned source rock units are especially important in the northern and northeastern part of the basin and along its western margin traps may have been charged by eocene lower oligocene source rocks in the hanoi trough the excellent middle miocene coal beds have probably generated hydrocarbons within the last few million years thus the huge and still underexplored song hong basin provides attractive areas for further exploration

middle to late holocene decreased fluvial aggradation and widespread peat initiation in the ishikari lowland northern japan this study investigated the influence of sea level and climate changes on the decreased fluvial aggradation and subsequent widespread peat initiation in the middle to late holocene in the ishikari lowland which is a coastal floodplain formed in response to the postglacial sea level change by introducing a new approach to separately evaluate the rates of organic and clastic sediment input we demonstrated that the peat began to form when the fluvial sedimentation rate was significantly decreased less than 0 6 mm yr while plant macrofossil analysis suggested that lowering of water level is also important to the peat initiation such changes in sedimentary environment may be associated with the abrupt abandonment of crevasse splays the concentrated ages of the peat initiation around 5600 5000 4600 4300 and 4100 3600 cal bp suggest that an allogenic control promoted the abandonment of crevasse splays and different onset ages can be explained by different fluvial responses of the ishikari river and i

transport of clay minerals and anthropogenic compounds into the german bight and the provenance of fine grained sediments se of helgoland a large mud body 500 km 2 and up to 21 m thick se of helgoland has been investigated using geochemical mineralogical and sedimentological methods the analysis of 27 sediment cores from this area revealed that overlying older fine grained sediments there is a 9cake9 of muddy polluted sediments up to 3 m thick which has accumulated over the last 100 years it is assumed that human activities like dredging and dumping are responsible for this rapid rate of deposition generally it has been estimated that all of this mud has been supplied by rivers entering this part of the north sea but analyses of sediments from the ems weser and the elbe rivers show that under normal conditions the river sediments do not enter the open sea but are trapped in the estuaries it may therefore be concluded that much of the underlying unpolluted sediments of the mud area were derived from elsewhere or were laid down during an earlier period one possibility is that the lower sediments were deposited when the german bight was a sheltered area protected by a barrier of morainic sediments in the north between helgoland and schleswig holstein this barrier must have been breached more than 2000 years ago

late quaternary sedimentary environments and landforms in the ganges delta abstract late quaternary sediments deposited since the lowest stand of sea level during the last glacial maximum in the ganges delta and its surrounding region were classified into five units according to their sedimentary facies these are the lowest unit of sandy gravels the lower unit of sand with a few gravels and the middle upper and uppermost units consisting mainly of sand and silt with occasional peat layers the contact between the lower and middle units is fairly sharp and the upper part of the lower unit is oxidized in some places this suggests a period of subaerial exposure after the deposition of the lower unit during the low stand of sea level about the time of the last glacial maximum rivers in the ganges delta and its surrounding region dissected the surfaces of the region and deposited the lowest unit on the valley floors the lower unit was deposited over the lowest unit during an early stage of the post glacial transgression between ca 12 000 yr bp and 10 000 yr bp the surface of the delta was slightly dissected and the top of the lower unit was weathered and oxidized following this period the middle and upper units of alluvial or deltaic sand and silt with occasional peat were deposited the coastline in the early holocene retreated towards the central part of the present ganges delta in the middle and late holocene the silt and clay with occasional peat layers of the uppermost unit indicate that the lowland gradually became marshy and poorly drained as the rate of transgression became slower

sources sinks and storage of river sediment in the atlantic drainage of the united states the history of sediment and its movement in the atlantic drainage demonstrate some of the difficulties of modeling sediment on a river basin scale soil erosion was accelerated by a factor of at least 10 when european settlers cleared forests and planted crops although increasing soil conservation practice and decreasing crop farming have since reduced the rates of erosion large quantities of eroded material are still stored on hillslopes and in stream valleys where they continue to augment the sediment loads of the rivers the sediment from this episode of erosion that is largely past can be expected to emerge from storage for many decades and perhaps even several centuries to come the reservoirs that have been built on many of the major rivers trap significant portions of the moving sediment which in some places may be remobilized by large floods essentially all the river sediment that reaches the atlantic coastal zone is trapped in estuaries and coastal marshlands probably less than 5 is deposi

dispersal concentration and deposition of suspended matter in the north sea suspended matter comes into the north sea from the atlantic ocean from the channel rivers seafloor erosion coastal erosion the atmosphere and from primary production the contribution of the last source is temporarily large when phytoplankton growth is abundant but is soon decomposed mineralized or consumed so that over the year the net effect is small accumulation and deposition of suspended matter occurs predominantly in only a few areas the waddensea the german bight the skagerrak norwegian channel the remainder of the north sea floor consists of pleistocene and early holocene relict deposits and of reworked sands and gravels the mechanisms resulting in accumulation and deposition are discussed there are strong indications that the amount of suspended matter flowing out from the north sea into the norwegian sea along the norwegian coast is only little more or the same as the amount coming in from the north atlantic although its composition may be different

clay mineral provinces in tidal mud flats at germany s north sea coast with illite k ar ages potentially modified by biodegradation abstract mineralogical studies chemical analyses and k ar dating were carried out on clay fractions from tidal mud flats along the lower saxony coast and its bays to identify material sources and sedimentary processes at this dynamic interface between air land and sea from the coast into the bays sediments are enriched in fine grained smectite relative to the coarser grained illite chlorite and kaolinite due to the weakening of the tidal current energy in the bays in addition the study area can be divided into two provinces on the basis of the illite k rb ratios and mg contents to the west schiermonnikoog dollart ley bay up to norderney island longshore currents carry suspensions from the belgian and dutch coasts to the east from langeoog island jade bay to the helgoland mud area suspensions from the elbe and weser rivers are mixed with submarine reworked glacial sediments whereas the portion of longshore current suspensions from the west decreases becoming negligible in the helgoland mud area off the elbe and weser estuaries the illite k ar data vary considerably and fail as source indicators due to differential settling and mixing of the clay material and probably to ar loss from illite by biodegradation during digestive processes only further offshore outside the zone of dynamic sediment dispersion do the k ar data fit provenance patterns

rapid flooding of the sunda shelf a late glacial sea level record the increase in sea level from the last glacial maximum has been derived from a siliciclastic system on the tectonically stable sunda shelf in southeast asia the time from 21 to 14 thousand calendar years before the present has been poorly covered in other records the record generally confirms sea level reconstructions from coral reefs the rise of sea level during meltwater pulse 1a was as much as 16 meters within 300 years 14 6 to 14 3 thousand years ago

the red river fault system in the tonkin gulf vietnam abstract the red river fault system in the tonkin gulf offshore haiphong was studied using seismic profiles calibrated by deep wells well characterised left lateral strike slip occurred continuously within a narrow 30 km wide zone southwest of the vinh minh fault between 30 ma and 5 5 ma however the corresponding amount of offset probably does not exceed a few tens of kilometres no sign of post 5 5 ma right lateral motion can be detected prior to 30 ma there is a widespread extension in a wider 100 km wide zone which could be related to a significant amount of left lateral motion the motion of the fault splays to the northeast of the vinh minh fault prior to 30 ma was absorbed in the rifting of the gulf of beibu a 15 5 ma unconformity separates the transtensional regime from a later transpresional regime this 15 5 ma date coincides with the cessation of sea floor spreading in the south china sea

a reappraisal of kerogen formation abstract comparative microscopical and chemical studies of recognizable entities in kerogen and their extant counterparts suggest a new and simple mechanism of kerogen formation which clarifies the interrelationships between extant biomass kerogen and fossil fuels

sea level changes in the tectonically stable malay thai peninsula abstract the malay thai peninsula is part of sundaland a geological region of relative crustal stability therefore the positions of old shorelines of the past 20 000 years or so can be considered to indicate positions of actual past sea levels over 200 shoreline indicators at positions below as well as above present sea level have been radiocarbon dated these dated positions indicate that prior to 6 ka the sea rose from at least 90 m below present sea level at rates that initially amounted to 15 mm year and later became 6 mm year at ca 6 ka the rising sea surpassed its current position and at ca 5 ka it reached 5 m during this maximum marine inundation the peninsula was narrower since the low coastal plains did not yet exist in the period following this maximum transgression the available shoreline data indicate that regional sea level subsided through a series of fluctuations that were characterized by amplitudes of 2 m and periods of about 2000 years the peaks and troughs of the fluctuations became progressively lower the latest peak was at about 1 7 m or 0 7 m above present high tide a few hundred years ago the cause of these fluctuations is not yet known but the trend suggests that in the near future regional sea level may subside at annual rates between 1 5 mm and 2 mm this rate of descent is 25 to 30 of the estimated rate of sea level rise that may result from global warming in other words for the malay thai peninsula the effect of sea level rise on account of manmade greenhouse gases will be partly compensated by actual subsidence of regional sea level

delta progradation and chenier formation in the huanghe yellow river delta china abstract to clarify holocene development of the huanghe yellow river delta and the relationship between delta progradation and chenier formation detailed sediment analyses and high resolution radiocarbon dating were done on borehole samples taken from two sites on the present huanghe h9601 latitude 37 40 5 n and longitude 118 28 7 e with an altitude of 5 5 m and h9602 lat 37 47 8 n and long 118 54 3 e 4 8 m downcore changes of sediment facies and accumulation rate show that delta progradation occurred at least twice during ca 2 6 1 2 c 14 yrbp and 1855 present at the two borehole sites these phases of progradation correlate with superlobes 6 and 7 and superlobe 10 respectively of ten superlobes composing the holocene huanghe delta shown by c xue historical changes in the yellow river delta china marine geology 113 321 329 1993 the boundary of these sediments at h9602 is sharp and erosional and correlates with cheniers located between borehole sites on the delta plain the diastem period between these phases of progradation almost coincides with the periods when the river mouth of the huanghe was located in the northwestern part of the bohai sea during 1048 1128 ad superlobe 8 and the jiangsu region facing the yellow sea during 1128 1855 superlobe 9 this suggests that chenier formation and delta progradation are linked and controlled by sediment supply and river course shifts of the lower reaches of the huanghe

initiation of the mekong river delta at 8 ka evidence from the sedimentary succession in the cambodian lowland abstract modern deltas are understood to have initiated around 7 5 9 ka in response to the deceleration of sea level rise this episode of delta initiation is closely related to the last deglacial meltwater events and eustatic sea level rises the initial stage of the mekong river delta one of the world s largest deltas is well recorded in cambodian lowland sediments this paper integrates analyses of sedimentary facies diatom assemblages and radiocarbon dates for three drill cores from the lowland to demonstrate holocene sedimentary evolution in relation to sea level changes the cores are characterized by a tripartite succession 1 aggrading flood plain to natural levee and tidal fluvial channel during the postglacial sea level rise 10 8 4 ka 2 aggrading to prograding tidal flats and mangrove forests around and after the maximum flooding of the sea 8 4 6 3 ka and 3 a prograding fluvial system on the delta plain 6 3 ka to the present the maximum flooding of the sea occurred at 8 0 0 1 ka 2000 years before the mid holocene sea level highstand and tidal flats penetrated up to 20 50 km southeast of phnom penh after a period of abrupt 5 m sea level rise at 8 5 8 4 ka the delta progradation then initiated as a result of the sea level stillstand at around 8 7 5 ka another rapid sea level rise at 7 5 7 ka allowed thick mangrove peat to be widely deposited in the cambodian lowland and the peat accumulation endured until 6 3 ka since 6 3 ka a fluvial system has characterized the delta plain and the fluvial sediment discharge has contributed to rapid delta progradation the uppermost part of the sedimentary succession composed of flood plain to natural levee sediments reveals a sudden increase in sediment accumulation over the past 600 1000 years this increase might reflect an increase in the sediment yield due to human activities in the upper to middle reaches of the mekong as with other asian rivers

smectite dehydration its relation to structural development and hydrocarbon accumulation in northern gulf of mexico basin a comparison of clay diagenesis data obtained from a study of tertiary shales from the brazos colorado river system of texas the mississippi river system of louisiana and the niger river system of nigeria illustrates significant differences in temperature intervals over which smectite diagenesis occurs the threshold temperature required to initiate diagenesis ranges from about 160 f 71 c in mississippi river sediments to more than 300 f 150 c in the niger delta water expelled from smectite into the pore system of the host shale during the process of diagenesis may migrate out of the shale early or may be totally or partially trapped and released slowly through time in either situation the water can act as a vehicle for hydrocarbon migration p ovided hydrocarbons are present in a form and in sufficient quantities to be transported observations from the northern gulf of mexico basin indicate a close relation between buildup of high fluid pressure and the smectite illite transformation process abnormal pressures exert partial control on the type and quantity of hydrocarbons accumulated because pressure potential determines the direction of fluid flow and overpressuring partly controls the geometry of growth faults and related folds in basins where shale structures are the dominant type formed the depths to which growth faults can penetrate and the angle of dip that these faults assume at depth are largely dependent on fluid pressure in the sedimentary section at the time of faulting dips of some faults in texas have been observed to change abruptly within the interval of smectite diagenesis and some faults formed in the overpressured miocene and younger sections become beddingplane types at depths where the temperature is near that required for thermal generation of petroleum although these faults may be important for fluid redistribution in shallow sandstone shale sections they are a minor factor in moving hydrocarbons out of shale below the faults in much of the texas offshore area fluid movement upward through microfracture systems in the deeply buried overpressured section overlying and extending upward from fault trends in the sub tertiary section is proposed as a mechanism for flushing hydrocarbons from the deeper portion of the northern gulf of mexico basin this flushing process would be enhanced by smectite diagenesis because water derived from smectite that was trapped during basin subsidence would cause the flushing process to continue for longer periods of time and to extend to greater depths than could be attained if only remnants of original pore water were present shale tectonism is also the primary mechanism for structural development in the tertiary section of the niger delta however seismic data indicate that the rate of dip change of seaward dipping listric growth faults is commonly less than that observed in texas where dips as low as 10 15 can occur at depths as shallow as 10 000 15 000 ft 3 048 4 572 m syndepositional faults in nigeria are formed in sandstone shale sections where the clay composition of shale is primarily kaolinite and where little water of smectite diagenesis has been added to the pore system of the host sedimentary section subtle differences in structural styles in the tertiary sections of texas and nigeria are probably the result of differences in clay composition of the shaly sections being deformed

what is a fluvial levee abstract fluvial levees are elevated partitions between channels and floodplains because of their character and position levees may provide critical controls on and insights into geomorphic processes that determine the distribution of water and sediment within river systems few studies have analysed the character distribution sedimentology and processes that form levees in modern depositional environments characterisation of levee deposits from the mississippi river continues to form the basis for most levee interpretations from the rock record this discussion paper assesses the reliability of interpretations of levee deposits in numerous examples from the rock record and their associated inferences for river style this uncertainty reflects the lack of definitive sedimentological attributes for levee deposits their limited preservation potential and the fact that levee identification in the rock record is inhibited by the reliance on geometric descriptors or indirect associations between channel and floodplain facies given these concerns it is suggested that geomorphologists and sedimentologists need to recognise the limitations of our present knowledge of levees and work towards a more systematic understanding of these significant fluvial landforms in the full spectrum of modern and ancient river settings

natural levee evolution in the rhine meuse delta the netherlands during the first millennium ce this paper presents reconstructions on natural levee development in the rhine meuse delta the netherlands during the first millennium ce covering the full delta plain it is the first study that performs this on a delta scale which allows seeing the delta wide trends on levee forming controls and their feedbacks we mapped the levee morphology and elevation by combining lidar imagery lithological borehole data soil mapping radiocarbon dates archaeological data and gis reconstruction techniques from the detailed levee reconstructions we quantified natural levee dimensions and evaluated the temporal changes therein the dimensions and the changes therein were then linked to external forcings increasing suspended sediment load variable flooding intensity and to natural preconditions e g delta plain width flood basin configuration we show that natural preconditions are an important control on levee shape this is demonstrated for the upper delta where the relatively narrow delta plain combined with strong compartmentation i e the occurrence of many alluvial ridges and enclosed flood basins caused the flood levels to be amplified allowing the natural levees to grow relatively high compartmentation also seems to have stimulated trapping of coarse grained overbank sediments explaining the clear downstream trend in levee width this effect was probably further aided by the clearance of the riparian forests mainly in the upstream and central delta which caused the coarser fraction of the suspended load to be further dispersed into the flood basin leading to wider levees in the first millennium ce several new river courses formed that avoided the areas of natural levee relief of abandoned alluvial ridges on these fossil alluvial ridges the topographical expression gradually reduced because of widespread flood basin trapping of overbank sediment which led to topographic levelling the natural levees that formed during this period along the new courses appear to be relatively high compared to precursor generations in the upper and central delta this is most likely related to the increased suspended sediment supply and intense flooding regime during their formation the hypotheses generated with this new delta wide overview help to better understand the controls in the development of levees which are important elements in river landscapes and in fluvial sedimentary records 2017 elsevier b v

role of minerals in thermal alteration of organic matter ii a material balance pyrolysis experiments were performed on green river and monterey formation kerogens types i and ii respectively with and without calcite illite or montmorillonite at 300 c for 2 to 1 000 hours under dry and hydrous conditions pyrolysis products were identified and quantified and a material balance of product and reactants resulted significant differences were found in the products generated by pyrolysis of kerogens with and without minerals both illite and montmorillonite adsorb a considerable portion up to 80 of the generated bitumen the adsorbed bitumen is almost exclusively composed of polar compounds and asphaltenes that crack to yield low molecular weight compounds and insoluble pyrobitumen during prolonged heating montmorillonite shows the most pronounced adsorptive and catalytic effects with calcite however the pyrolysis products are similar to those from kerogen heated alone and bitumen adsorption is negligible applying these results to maturation of organic matter in natural environments we suggest that a given type of organic matter associated with different minerals in source rocks will yield different products furthermore the different adsorption capacities of minerals exert a significant influence on the migration of polar and high molecular weight compounds generated from the breakdown of kerogen therefore the overall accumulated products from carbonate source rocks are mainly heavy oils with some gas whereas light oils and gases are the main products from source rocks that contain expandable clays with catalytic and adsorptive properties

influence of minerals and iron on natural gases generation during pyrolysis of type iii kerogen abstract pyrolysis experiments in a closed system were conducted on kerogen isolated from a low mature coal sample either in the presence or absence of clay minerals iron bearing minerals transition metal and their mixture respectively the generated gases were collected and analyzed for chemical compositions by using gas chromatography and mass spectrometer the solid residues were also quantitatively collected and analyzed for iron species using mossbauer spectroscopy these experiments revealed that the hydrocarbon gases generation from kerogen was significantly increased by catalysis of minerals and transition metal iron the generation of hydrocarbon gases could be potentially increased by 0 1 1 5 times in the presence of minerals and iron and the catalytic efficiency was in the order of kerogen mixed catalysts kerogen pyrite kerogen smectite kerogen iron kerogen the dryness ratios including ethene ethane propene propane isobutane n butane and isopentane n pentane were all decreased due to the catalysis of smectite pyrite and mixed catalysts and slightly increased with iron addition the conversion of pyrite into pyrrhotite and elemental sulfur started at 300 c during the experiments for which pyrite might be as an inducer indirectly via sulfur and thus enhance the free radical formation and improve the hydrocarbon yield

holocene evolution of the song hong red river delta system northern vietnam abstract the song hong red river delta located on the western coast of the gulf of bac bo tonkin in the south china sea formed as a result of the song hong sediment discharge throughout the holocene the river s sedimentary basin upstream from the delta plain is not large the delta plain comprises emerged tidal mangrove flats formed during the sea level highstand at 2 3 m 6 4 cal kyr bp and a beach ridge strandplain with straight to lobate beach ridges on the landward and seaward sides of the delta plain respectively the delta affords us the opportunity to examine river mouth morphodynamics comprehensively in relation to sediment discharge and sea level changes in this paper we describe the holocene evolution of the song hong delta system and the river mouth morphodynamics on the basis of seven sediment cores each 30 70 m long taken from the delta plain during 1999 2001 and 101 radiocarbon dates obtained from the core sediments sediments from the seven cores consisting of incised valley fills since the last glacial maximum can be divided in ascending order into fluvial sediments composed of gravelly sand and mottled clay tide influenced estuarine sediments containing shell and wood fragments and deltaic sediments composed of tide influenced sand and mud deposits in which the contents of sand and wood fragments increase upward by applying sequence stratigraphic concepts a transgressive surface can be identified at the gravelly sand mottled clay boundary and the maximum flooding surface can be identified at the estuarine deltaic sediments boundary the lowstand systems tract transgressive systems tract and highstand systems tract record 15 15 9 and 9 0 cal kyr bp respectively during the past 9 kyr the majority of the sediment discharged by the song hong accumulated in the incised valley and enhanced progradation at the river mouth the river mouth prograded from the bay head toward the gulf and its morphology changed from funnel shaped 9 6 cal kyr bp to straight 6 2 cal kyr bp and finally to lobate 2 0 cal kyr bp the morphological change from a funnel shaped to straight coast is interpreted to have been closely related to a hydrologic regime shift from a tide dominated bay head setting to a wave influenced open coast setting the cessation of the sea level rise at 6 cal kyr bp may have played only a small role in the change of river mouth morphology because the progradation rate decelerated from 22 to 4 m yr instead of accelerating at that time the river mouth morphodynamic change from straight to lobate was largely caused by an increase in the song hong sediment discharge from 17 27 9 2 cal kyr bp to 49 million t yr 2 0 cal kyr bp as a result of anthropogenic deforestation along the upper reaches of the song hong

sources of ca2 in the major carbonate cements in eocene sandstones and conglomerates evidence from sr isotopes sr ca ratios and rare earth elements abstract different sources of calcium have important effects on the formation and distribution of carbonate cements on the basis of identifying all possible sources of calcium comprehensive quantitative analyses of sr c and o isotopic values and trace elements including rare earth elements were conducted to determine the ca2 sources and their changes in the same type of carbonate cements at different vertical positions in the same reservoirs ferroan calcite and ankerite were the major types of carbonate cements ca2 in ferroan carbonate cements in the sandstones near the mudstone sandstone m s interfaces was derived primarily from diagenetic fluids mixed with ca2 originating from the transformation of smectite to illite and from original sedimentary water in the adjacent mudstones however ca2 in the ferroan carbonate cements in the sandstones away from the m s interfaces originated from the transformation of smectite to illite the dissolution of carbonate minerals and original sedimentary water in source rocks the gradual change of ca source of the same type of ferroan carbonate cements indicates the diversity of migration direction of diagenetic paleo fluid in the same period during the transformation of smectite to illite concentration gradients were created from mudstones to sandstones ca2 mg2 fe2 and other cations in the mudstones diffused to the adjacent sandstones and provided sources of ferroan carbonate cements at the edge of the sandstones pore water with ca2 mg2 fe2 co32 and other cations in the source rocks was collectively charged into sandstones during oil emplacement and promoted the precipitation of ferroan carbonate cements in residual pore water due to oil emplacement and material supplied by the adjacent mudstones the content of ferroan carbonate cements in the sandstones was lower and the reservoir porosity was higher at a greater distance from the m s interfaces however in thick bedded sandstones due to lack of material supply from the adjacent mudstones ca2 mg2 fe2 and co32 in the ferroan carbonate cements were mainly derived from source rocks as a result no significant changes were observed in the content of ferroan carbonate cements and reservoir porosity in the vertical direction

tracing holocene channels and landforms of the nile delta through integration of early elevation geophysical and sediment core data intensification of anthropogenic activities and related processes have altered the morphology of modern deltaic systems as a result mapping of geomorphic features such as paleochannels using re

song hong red river delta evolution related to millennium scale holocene sea level changes abstract the song hong red river delta occurs on the northwest coast of the south china sea its evolution in response to holocene sea level changes was clarified on the basis of sedimentary facies and 14 radiocarbon dates from the 40 m long duy tien core from the delta plain and using previously reported geological geomorphological and archaeological data the delta prograded into the drowned valley as a result of early holocene inundation from 9 to 6 cal kyr bp as sea level rise decelerated the sea level highstand at 2 3 m from 6 to 4 cal kyr bp allowed widespread mangrove development on the delta plain and the formation of marine notches in the ha long bay and ninh binh areas during sea level lowering after 4 cal kyr bp the former delta plain emerged as a marine terrace and the delta changed into the present tide and wave influenced delta with accompanying beach ridges delta morphology depositional pattern and sedimentary facies are closely related to holocene sea level changes in particular falling sea level at 4 cal kyr bp had a major impact on the evolution of the song hong delta and is considered to be linked to climate changes

holocene floodplain evolution in the shiribeshi toshibetsu river lowland northern japan abstract the influence of sea level and climate changes on the evolution of coastal floodplains is an important problem in fluvial geomorphology and geology however few studies have constructed detailed chronologies of floodplain evolution and the influence of sea level and climate changes at submillennial time scales is not clear this study investigated the holocene evolution of the floodplain in the shiribeshi toshibetsu river lowland hokkaido northern japan based on 13 auger cores 15 radiocarbon ages and 2 cross sections made using existing columnar sections in the study area peat beds 3 6 m thick in the uppermost holocene sediments are underlain by fluvial sediment that mainly consists of sand beds resulting from crevassing or progradational avulsion age elevation plots of the bases of these peat beds suggest that fluvial aggradation was continuous until peat formation began which in turn suggests that peat beds began to form with the cessation of fluvial deposition the chronology of floodplain sediments based on radiocarbon ages indicates that peatlands began to develop locally before ca 6500 cal bp and became moderately widespread before 5600 cal bp peatlands then became more extensive after two periods of rapid expansion during ca 5300 5000 and 4100 3900 cal bp comparison with sea level and regional climate changes suggests that the initiation of these peat beds before 5600 cal bp was associated with the deceleration of sea level rise at ca 7000 cal bp the two later periods of peatland expansion may have been strongly influenced by reduced fluvial activity due to decreased precipitation from a weakened east asian summer monsoon this interpretation suggests that floodplain evolution was controlled by sea level and climate changes and that the response to climate change occurred at submillennial time scales a comparison with the ishikari lowland on hokkaido showed that the two floodplains have slightly different histories possibly because of differences in internal characteristics of the fluvial systems such as the number and size of tributary rivers water discharge and sediment supply although their responses to sea level and climate changes were similar the fluvial response to sea level and climate changes revealed in this study has implications for studies of the holocene evolution of other coastal floodplains

illitizing fluids as precursors of hydrocarbon migration along transfer and boundary faults of the jeanne d arc basin offshore newfoundland canada abstract illite content in mixed layer illite smectite i s and the degree of ordering in the fine fraction

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

delta initiation and holocene sea level change example from the song hong red river delta vietnam abstract delta initiation and subsequent delta growth were investigated by using radiocarbon dated borehole cores from the song hong red river delta vietnam the sediments underlying the present delta plain record three depositional systems since the last glacial maximum fluvial estuarine and deltaic in ascending order the landward part of the initial delta was characterized by an active tide influenced accumulation of sandy sediments the seaward part of the initial delta is composed of muddy prodelta and seafloor sediments that accumulated slowly radiocarbon ages of molluscan shells and organic materials suggest that the transition from estuary to delta occurred at approximately 8500 cal years bp the transition was induced by deceleration of the postglacial sea level rise which was coeval with the delta initiation the stacking pattern of the delta system is very different from that of the estuary system the sediments of the estuary that developed during the rapid rise in sea level between 11000 and 8500 cal years bp display a retrogradational stacking pattern forming a thick transgressive systems tract on the other hand aggradational as well as progradational stacking with clinoform architecture characterized the delta system between 8500 and 6500 cal years bp as the sea level continued its slow rise progradation has been dominant during the last 6500 years because the cessation of sea level rise resulted in little accommodation being added the results of this study are similar to those for other major delta systems such as the changjiang and the ganges brahmaputra deltas despite large differences in sediment discharge tectonics basin size and coastal environment this implies that the postglacial sea level rise and the change in the rise rate markedly influenced the evolution of depositional systems at river mouths

stratigraphy and holocene evolution of the mud dominated chao phraya delta thailand abstract the central plain of thailand was formed over the last 8 7 kyr mainly by the deltaic processes of two major rivers the chao phraya and the mae klong the delta plain is the third largest delta plain in southeast asia after that of the mekong and the irrawaddy on the basis of sedimentological and paleontological analyses of samples from three boreholes and an open pit survey the evolution of the delta was clarified with high resolution 14 c dating after the maximum transgression at between 8 and 7 cal kyr bp the delta system migrated southward into the paleo gulf of ayutthaya a large mud shoal the sananivate mud shoal formed near the mouth of the paleo gulf between 7 and 3 cal kyr bp and facilitated its infilling as a result the delta has prograded rapidly particularly during the last 2 kyr deltaic sediment volume for the last 7 5 0 5 kyr shows that the average rate of sedimentation was 23 1 3 6 million t yr which is nearly the same as the present total sediment discharge from both rivers the comparatively wide delta plain relative to sediment discharge resulted from the stable sea level the shallow paleo gulf acting as a receiving basin and effective sediment trapping because of the mud shoal

clay mineral and heavy metal distributions in the northeastern north sea abstract clay mineralogy and heavy metal distribution of surface sediments of the northeastern north sea have been analysed in order to show the origin and transport pathways of fine grained sediments the distribution patterns of clay minerals largely reflect regional current patterns fine material enriched in smectite derived mostly from the german bight sector in the south is transported by the jutland current parallel to the west coast of denmark into the skagerrak where a decreasing proportion of smectite indicates the increasing influence of the central and northern north sea currents illite and chlorite have identical distribution patterns in the northeastern north sea which suggests a common origin for both clay minerals this origin is located in pleistocene relict sediments of the northern north sea rather than in a contribution from the north atlantic zinc cadmium copper and lead in surface sediments of the north sea when compared to background values are significantly enriched sediments of the inner german bight are in comparison with other north sea sediments highly polluted a zone of high heavy metal contents zn cd and cu is found along the german and danish coasts comparable to the smectite distribution indicating the transport of fine grained polluted sediments to the north further to the north these sediments are diluted by less polluted sediments finally in the skagerrak and the norwegian trench a relatively low stage of pollution is reached

heterogeneities of organic matter and its occurrence forms in mudrocks evidence from comparisons of palynofacies abstract mudrocks buried at different depths in a single well exhibiting different sedimentary environments and lithologies were collected from the dongying sag of the jiyang depression of eastern china to investigate the heterogeneities of organic matter om and its occurrence forms in this study both bulk rocks and their organo clay composites i e

sediment flux and the anthropocene data and computer simulations are reviewed to help better define the timing and magnitude of human influence on sediment flux the anthropocene epoch impacts on the earth surface processes are not spatially or temporally homogeneous human influences on this sediment flux have a secondary effect on floodplain and delta plain functions and sediment dispersal into the coastal ocean human impact on sediment production began 3000 years ago but accelerated more widely 1000 years ago by the sixteenth century societies were already engineering their environment early twentieth century mechanization has led to global signals of increased sediment flux in most large rivers by the 1950s this sediment disturbance signal reversed for many rivers owing to the proliferation of dams and sediment load reduction below pristine conditions is the dominant signal today a delta subsidence signal began in the 1930s and is now a dominant signal in terms of sea level for many coastal environments overwhelming even the global warming imprint on sea level humans have engineered how most water and sediment are discharged into the coastal ocean hyperpycnal flow events have become more common for some rivers and less common for other rivers bottom trawling is now widespread suggesting that even continental shelves have received a significant but as yet quantified anthropocene impact the anthropocene attains the level of a geological climate event such as that seen in the transition between the pleistocene and the holocene

influence of igneous intrusions on thermal maturity and optical texture comparison between a bituminous marl and a coal seam of the same maturity abstract the impact of a 120 cm thick dike on dispersed organic matter in the triassic marry harbour mh bituminous marl in the raanes peninsula ellesmere island arctic canada was studied using reflected light microscopy and rock eval pyrolysis results were compared to a coal seam of similar maturity that was thermally altered by an igneous intrusion the mh bituminous marl is mature and within the oil window ro 0 94 whereas the coal is high volatile b bituminous rank ro 0 80 thermal alteration impacted differently the organic rich marl than the coal seam most of the heat generated by the intrusive emplacement in contact with coal is spent transforming coal to coke in the plastic layer zone similar to the process that coal undergoes in industrial coking operations in contrast the thermal alteration of sedimentary rocks occurs over longer distances as a result of the absence of a plastic layer zone the impact zone of the 120 cm thick igneous intrusion was greater in the mh bituminous marl which became thermally altered ro 2 34 at 190 cm from the contact with the dike on the contrary the coal became thermally altered ro 5 0 by a 240 cm alkali basalt intrusion twice the thickness of the mh dike and its impact zone was only 65 cm heat and hot volatile matter produced by the thermal decomposition of organic matter and minerals carbonate dehydration of clay minerals in contact with the igneous intrusion body is transferred through the sedimentary rock matrix by convection through fractures this transformation is evident by the occurrence of the pyrolytic carbon at various distances in the fractured mh marl from contact the hydrogen index hi shows a similar trend to that of the remaining source potential s2 both parameters decrease systematically toward the dike and go through a minimum at 20 cm from the dike contact as the indigenous organic matter is converted to hydrocarbons or devolatilized at the dike contact both s2 and hi have higher values these trends are similar to those of the volatile elements h and cl in the intruded coal seam the free hydrocarbons s1 showed a slightly different trend than s2 and hi it increased initially from 300 cm and reached a maximum at about 190 cm from the dike contact before decreasing continually and reaching a minimum at 20 cm from the contact at the dike contact the s1 increased slightly similar to the hi and s2 the presence of oil droplets trapped in carbonate concretions in combination with the highest value of oil expelled from the source rock based on s1 toc at distance of 190 cm from dike is an indication of the influence of contact metamorphism on oil generation locally furthermore it indicates that intrusion of igneous dikes into the bituminous mh marl resulted in an increase of organic matter maturation locally and in hydrocarbon generation

cenozoic plate reconstruction of the south china sea region abstract reconstructions of the south china sea region at 60 ma 40 ma 30 ma 20 ma 10 ma and 5 ma are presented we have attempted to place the south china sea basin in a regional tectonic framework the tectonic evolution of the major blocks surrounding the south china sea were analyzed as well as the relative motions of the indian and australian plates we have tried to correct the tectonic models available in this region a 3 d graphics terminal was used to derive rotation poles for the different tectonic blocks and our model was then tested to determine its self consistency when the model conflicted with previous interpretations the input data were evaluated for alternative explanations at least two and possibly three stages of extension can be recognized in this region the earliest one active in the late cretaceous to eocene involved nw se extension the second one active from the late eocene to early miocene involved north south extension the third stage of extension which probably trended nw se can be dated as post oligocene the first extensional event produced the ne sw trending proto south china sea and a series of sedimentary basins along the south china margin following the southeastward extrusion of indochina the proto south china sea was mostly consumed at the palawan trough renewed north south extension in the south china continental margin started the present day south china sea spreading in the oligocene the southeastward extrusion of indochina blocked by sundaland resulted in the nw se trending opening of the south china sea basin in the early miocene collision of the north palawan microcontinental block with the west philippines block stopped the opening of the south china sea at the end of early miocene spreading activity switched to the sulu sea basin in the middle miocene but collision between the sulu ridge and the west philippines at mindanao halted the opening of the sulu sea at the end of the middle miocene in the late miocene greater india continued its northward path and seems to have ripped open the andaman sea in the pliocene subduction along the northern manila trench placed the north luzon arc on a collision path with the east asia continental margin at taiwan our reconstructions along with detailed geological and geophysical information may be used as a predictive tool for basin evolution models and block interactions in this region the development of the south china sea basin the gulf of thailand the malay basin and the central thailand basins are the result of collision induced extensional forces the sulu celebes and sumatra basins were formed as a consequence of prolonged subduction the opening of the pearl river mouth west natuna south china sea sulu and possibly celebes basins were terminated by various plate collisions during the course of plate reorganizations major boundary faults have changed their slip senses during different stages of evolution

natural levees and human settlement in the song hong red river delta northern vietnam the song hong red river delta northern vietnam is characterized by huge natural levees in an area of the delta plain known as the west floodplain where fluvial sedimentation predominates the natural levees along the day river a major distributary of the song hong are comparable in size with those of the main course of the song hong the day river levees are 3 8 km wide and rise 2 5 m above the adjacent backswamps and have played an important role in human settlements since the late metal age we discussed the relationships among the natural levees of the day river delta progradation and the distribution of archaeological sites on the delta plain during the early holocene the accumulation of sediment discharged by the song hong enhanced both aggradation of the floodplain and river mouth progradation within the drowned valley of the song hong radiocarbon dates from cores trench exposures and archaeological sites record a dramatic slowing of aggradation when sea level stabilized during 6 4 cal

authigenic minerals related to wettability and their impacts on oil accumulation in tight sandstone reservoirs an example from the lower cretaceous quantou formation in the southern songliao basin china abstract oil accumulation being difficult and complicated is an important issue in petroleum exploration researches authigenic minerals such as carbonate cements and chlorite can in certain reservoirs alter the wettability of some pore spaces from water wet to oil wet generally these oil wet pore spaces are favorable for oil accumulation the alteration of reservoir wettability induced by authigenic minerals and the impacts on oil accumulation in tight sandstone reservoirs were investigated using a suite of mineralogical and geochemical characterization techniques including thin section observation sem eds xrd qemsem cl quantitative grain fluorescence qgf fluorescence spectral analysis contact angle measurement and sealed coring oil saturation testing on the fourth member of the lower cretaceous quantou formation k1q4 in the southern songliao basin china the study shows that the tight sandstone reservoirs are compositionally immature with detrital grains distributed homogeneously quartz carbonates and clay minerals that show heterogeneous distribution characteristics are the major authigenic minerals in some parts of the intergranular pores the detrital mineral assemblage suggests that the reservoir rocks at deposition and before diagenesis had characterized by strong water wet properties with the development of authigenic minerals carbonate cements and authigenic chlorite tend to alter the wettability of some parts of the existing pore spaces from water wet to oil wet in the k1q4 sandstone reservoirs oil prefers to accumulate in the cemented residual pore spaces around carbonate cements and chlorite reservoirs containing about 4 5 carbonate cements are suggested to be more preferable to oil accumulation these reservoirs are mainly located between sandstone mudstone interfaces and central parts of the sand bodies chlorites have mainly two effects on one hand chlorite alters the wettability of existing pore spaces and provides preferential accumulation sites for oil in the tight sandstone reservoirs on the other hand it can reduce the adhesion of oil through forming clay oil flocs and promote further migration consequently the reservoirs with moderate amount of carbonate cements or chlorite always show relative high oil saturation in the k1q4 tight sandstones

smectite illitization difference of source rocks developed in saline and fresh water environments and its influence on hydrocarbon generation a study from the shahejie formation dongying depression china abstract samples of argillaceous source rocks from three sub members of the shahejie formation es in the dongying depression china were collected to investigate the differences in hydrocarbon generation among the sub members which developed in fresh es32 es33 and saline es41 water environments pyrolysis xrd and thermo xrd analyses were used to compare the characteristics of organic matter om clay minerals and om occurrences total organic carbon and hydrocarbon potential proxies suggest that the samples from es33 were much better than the other two intervals which agrees with previous studies the characteristics of clay minerals suggest that the samples from es41 have the most abundant illite with a maximum illite percentage in mixed layer illite smectite i sm and the best crystallinity of i sm with a main stacking mode of r1 5 however the stacking modes of i sm in es32 and es33 were primarily r0 and r1 respectively and the crystallinity was relatively poor thus the smectite illitization process was faster in es41 than in the other two intervals and a saline environment was a primary cause for the acceleration of the process moreover om occurrence indicates that the samples from es41 had the lowest amount of interlayer om whereas es33 had the largest amount therefore the rapid illitization in es41 caused abundant interlayer om to be desorbed and discharged which in turn caused the amount of residual interlayer om in es41 to be less than that in the other two intervals thus the source rocks of es41 made a more significant contribution to hydrocarbon generation than those of the other two units in conclusion the inconsistent illitization among these intervals was a major cause of the differences in hydrocarbon generation

roman and early medieval habitation patterns in a delta landscape the link between settlement elevation and landscape dynamics settlement locations in delta landscapes change through time because of cultural and natural dynamics we assessed the impact of natural landscape dynamics on settlement location shifts for the rhine meuse delta in the netherlands during the roman and early medieval periods 12 bce 450 ce and 450 1050 ce respectively during this time interval major landscape and cultural changes occurred in this area with river avulsions and changes in flooding frequency coinciding with changing settlement patterns in the delta plain the relatively high and dry alluvial ridges of abandoned or active rivers were most favourable for habitation settlement location and elevation patterns were reconstructed in these landscape units using a high resolution elevation map of the alluvial ridges by integrating high resolution palaeo environmental and archaeological datasets for this period we were able to spatially analyse the trends and to assess the effect of environmental changes on habitation results show that settlements progressively shifted towards higher areas between 250 and 750 ce on average by 20 cm over this period deltawide which was coeval with an increased frequency of severe rhine floods the observed spatial differences demonstrate that this trend is most notable in the least elevated segments of the study area in areas where new large river branches developed settlements show a strong shift towards higher elevated parts of the landscape or even became completely abandoned the river probably caused floods to be more frequent and more severe in these areas despite the clear link between changing settlement positions and floods during the studied time interval floods do not seem to have caused long term abandonment of major parts of the study area

holocene delta plain development in the song hong red river delta vietnam abstract holocene delta plain development was investigated based on three sediment cores analyzed in detail from the song hong red river delta plain in vietnam two cores da and pd from the western delta plain showed both the landward limit of the transgressive estuarine system in the valley incised during the last glacial maximum and floodplain evolution since the middle holocene on the other hand a core tl from the eastern delta plain revealed a pleistocene terrace buried under the deltaic sediments and a slow accumulation rate compared with that in the west at 8 cal ky bp the shoreline migrated very close to the present hanoi city area and the sedimentary environment changed to tidal flat or salt marsh hanoi city marks the northern limit of shoreline transgression the mangrove swamp expanded from 8 to 5 cal ky bp to the landward limit of the delta plain subsequently the shoreline migrated seaward as a result of delta progradation and sea level lowering from 5 cal ky bp the emerged area evolved into a floodplain and natural levees formed along the abandoned river channels on the western delta plain but at 2 cal ky archeological sites indicate that the holocene terrace in the eastern delta plain was still inundated

protection of organic matter by mineral matrix in a cenomanian black shale abstract three types of pathways degradation recondensation natural sulphurization and selective preservation are commonly considered for the formation of kerogen dispersed in sedimentary rocks a fourth pathway has been recently put forward however from studies on recent marine sediments the so called sorptive protection mechanism this pathway is based on the adsorption of otherwise labile organic compounds onto minerals thus preventing their diagenetic degradation and promoting their subsequent condensation into kerogen the main results of the present study are derived from a combination of microscopic and pyrolytic methods applied on a cenomanian kerogen they provide i evidence on an ancient material for a crucial role of the mineral matrix both in organic matter om preservation during kerogen formation and in kerogen stability once formed ii indications that the dominant protective process likely involves physical protection by minerals resulting from alternation of organic and clay nanolayers of approximately 100 nm in thickness rather than om adsorption as molecular monolayers and iii observations of the relatively poor stability of an isolated kerogen contrary to the inertness commonly assumed for fossil macromolecular organic matter

the influence of shale depositional fabric on the kinetics of hydrocarbon generation through control of mineral surface contact area on clay catalysis abstract accurately assessing the temperature and hence the depth and timing of hydrocarbon generation is a critical step in the characterization of a petroleum system clay catalysis is a potentially significant modifier of hydrocarbon generation temperature but experimental studies of clay catalysis show inconsistent or contradictory results this study tests the hypothesis that source rock fabric itself is an influence on clay mineral catalysis as it controls the extent to which organic matter and clay minerals are physically associated two endmember clay organic fabrics distinguish the source rocks studied 1 a particulate fabric where organic matter is present as discrete 5 m particles and 2 a nanocomposite fabric in which amorphous organic matter is associated with clay mineral surfaces at sub micron scale high resolution electron imaging and bulk geochemical characterisation confirm that samples of the miocene monterey formation california are representative of the nanocomposite source rock endmember whereas samples from the permian stuart range formation south australia represent the particulate source rock endmember kinetic experiments are performed on paired whole rock and kerogen isolate samples from these two formations using open system non isothermal pyrolysis at three different heating rates 0 7 2 and 5 k min to determine the effects of the different shale fabrics on hydrocarbon generation kinetics extrapolation to a modelled geological heating rate shows a 20 c reduction in the onset temperature of hydrocarbon generation in monterey formation whole rock samples relative to paired kerogen isolates this result is consistent with the monterey formations s nanocomposite fabric where clay catalysis can proceed because reactive clay minerals are intimately associated with organic matter by contrast there is no significant difference in the modelled hydrocarbon generation temperature of paired whole rock and kerogen isolates from the stuart range formation this is consistent with its particulate fabric where relatively large discrete organic particles have limited contact with the mineral matrix and the clay minerals are mainly diagenetic and physically segregated within pores while heating rate may have a control on mineral matrix effects this result shows that the extent to which organic matter and clay minerals are physically associated could have a significant effect on the timing of hydrocarbon generation and is a function of the depositional environment and detrital vs diagenetic origin of clay minerals in source rocks

optical description of amorphous kerogen in both thin sections and isolated kerogen preparations of precambrian to eocene shale samples abstract this paper presents a limited study of precambrian kerogen and compares it to phanerozoic kerogen in both cases most of the kerogen is amorphous while the specific biological precursors of kerogen may be significantly different between the precambrian and phanerozoic the mode of degradation and preservation in shales may be similar and that is what is found in the description of the amorphous kerogen it is suggested that similar methods of sample prepagation description and classification can be applied to all sedimentary organic matter regardless of age kerogen disseminated organic matter of sedimentary rocks that is insoluble in nonoxidizing acids bases and organic solvents hunt 1979 occurs in many forms when observed with a microscope structured kerogens include spores pollen unicellular algae cuticle and cellular tissue of plants and coal fragments the majority of kerogens have no structures relatable to precursor organisms and are called amorphous this paper describes optical comparisons of various preparations of organic rich sedimentary rocks and the information that can be derived from them optical descriptions of organic matter in particular the amorphous fraction in sedimentary rocks help us to understand the bulk chemical or petroleum generating properties as well as paleodepositional environments there is no universally accepted method of preparing samples for optical study nor is there a unified set of terms to describe the observations ideally more information about the origin or preservation of organic matter can be obtained when it is studied in situ in the rock matrix in thin section revealing relationships to depositional fabric and clues from mineralogy and microfossils however it is often necessary to physically concentrate the organic matter for study because it is too dispersed throughout the rock matrix to be seen in thin section the concentrated or isolated organic matter is prepared either as polished mounts or strewn slides for optical study more confident kerogen identifications can be made if the different preparations are examined with more than one microscopic lighting condition doubly polished thin sections of whole rock can be viewed with three common microscope lighting conditions transmitted reflected white and reflected blue light or fluorescence visual kerogen strewn slides which can also be viewed with the three lighting conditions contain the isolated organic matter following acid removal of most of the mineral matrix and provide detailed morphological information about the kerogen itself polished mounts of isolated kerogen or whole rock similar to polished coal plugs can only be viewed with reflected white or blue light and are somewhat limited in the information they convey despite their relative ease to prepare examples of amorphous kerogens from a variety of samples are shown including thin section documentation of the occurrence of oil prone amorphous kerogen in laminae of the eocene green river formation in stylolites of cretaceous carbonates from dubai thin section illustration of solid bitumen rather than amorphous kerogen in paleoreservoir rocks from the permian of svalbard norway detailed unicellar algal morphologies in strewn slides of devonian samples from russia strewn slide details of gas prone amorphous kerogen textures from silurian bolivian samples and the occurrence of oil prone amorphous kerogen in the precambrian nonesuch formation more precambrian organic rich rock need to be studied optically by the methods suggested here to verify the hypothesis that precambrian kerogens are mostly amorphous the best way to completely describe amorphous kerogens is to use both isolated kerogen strewn slides and whole rock polished thin sections

kerogen origin evolution and structure kerogen commonly defined as the insoluble macromolecular organic matter om dispersed in sedimentary rocks is by far the most abundant form of om on earth this fossil material is of prime importance as the source of oil and natural gas moreover kerogen can provide essential information on major topics such as past environments climates and biota this review reports the main advances in kerogen studies since the comprehensive synthesis edited by durand durand b ed kerogen insoluble organic matter from sedimentary rocks editions technip paris 1980 it is organized into eight sections the first two are concerned with the successive definitions of kerogen and the definition used here the different techniques used for kerogen isolation without loss or degradation and basic kerogen analysis the third and fourth focus on sedimentary om sources and preservation processes in relation to depositional environment including sedimentation conditions favourable for kerogen accumulation and extrapolation to past geological time great strides have been made in the latter topics over the last 25 years owing to a combination of classical studies in organic geochemistry and studies in other domains such as biogeochemistry oceanography hydrology and soil science along with the development of powerful analytical tools the next two sections deal with the different kerogen classifications by type and kerogen evolution and maturation upon burial in sediments structural modelling of coal and kerogen based on physical and or chemical structural analysis is described in the following section although only statistical the models thus derived provide a synthetic view of the main structural resemblances and differences among various samples in relation to source maturity or physicochemical properties finally the last section explores some of the advances in kerogen understanding expected for the near future the review includes a list containing about 500 references

holocene variability of the kuroshio current in the okinawa trough northwestern pacific ocean abstract cores 255 and b 3gc from the southern and northern okinawa trough respectively were studied for determining the variability of the kuroshio current on centennial scales during the holocene based on detailed ams 14 c dates stable isotope and planktonic foraminiferal distribution the main flow of the kuroshio current was inferred to re enter the okinawa trough at 7 3 calendar cal kyr bp leading to abrupt changes in sedimentation rate remarkably increased abundance of the kuroshio current indicator pulleniatina obliquiloculata increased sea surface temperature sst and depth of thermocline dot during 4 6 2 7 cal kyr bp the abundance of p obliquiloculata sharply decreased corresponding to a decreases in sst and dot implying that the influence of the kuroshio current weakened at that time possibly as a result of the intensified winter monsoon significantly the kuroshio current proxies e g the difference in sst between the southern and northern okinawa trough display periodicities of 1500 yr and 700 800 yr ascribed to the second harmonic of the 1500 yr cycle in oceanic thermohaline circulation during the holocene the holocene events at 0 6 1 7 3 3 4 6 5 9 8 1 9 4 cal kyr bp in the okinawa trough appear to be the most recent manifestation of the millennial scale climate cycle recorded in the north atlantic arabian sea marine sediment cores and greenland ice cores suggesting global climatic tele connections

did changes in antarctic ice volume influence late holocene sea level lowering abstract there has been great debate over the last few decades on the magnitude and causes of relative sea level lowering during the late holocene the principal attributed causes are geodynamic rather than glacio eustatic an alternative partial cause is an increase in antarctic ice volume glaciological and glacial geological field evidence indicates that during the late holocene the antarctic alpine glaciers ice sheet margins and outlet glaciers have expanded and the ice sheet interior has thickened this is attributed to i an ice thickening in central east antarctica throughout the holocene which was caused by the 50 higher holocene snow accumulation rates than those during the glacial stage coupled with the slow reaction time for ice sheet velocities to respond to the increased accumulation and temperature and ii increased ice volume supplied by higher than mean holocene accumulation rates associated with a warmer climatic period between 4000 to 2500 years b p it is estimated that these effects could account for 1 0 0 2 m of the interpreted sea level lowering on mid oceanic islands with 0 7 0 1 m of lowering occurring between 4000 and 2500 years b p

varied pathways of river borne clay minerals in a near shore marine region a case study of sediments from the elbe and weser rivers and the se north sea abstract the the results outline significant systematic changes in the proportions of clay minerals in the k rb ratios the k ar data and in the heavy metal contents at the fluvial estuarine transition and towards the marine environment these changes result from a progressive mixing of suspended fluvial material with reworked pleistocene sediments at the bottom of the north sea near shore the proportion of reworked pleistocene sediment amounts only 20 30 the mixture is distributed within a 100 km wide zone mainly by currents parallel to the coast it is also transported during flood tide into the estuaries where it is mixed further with suspended fluvial material the k rb ratios and k ar dates obtained from illite prove to be particularly useful for modeling the mixing of the clay minerals as well as their distribution patterns and origin

spillage sedimentation on large river floodplains active deposition across the floodplains of large rivers arises through a variety of processes collectively these are here termed spillage sedimentation three groups of 11 spillage sedimentation styles are identified and their formative processes described form presences on large river floodplains show different combinations of active spillage styles only some large floodplains have prominent levees some have coarse splays many have accessory channel dispersion and reworking while still water sedimentation in lacustrine environments dominates some lower reaches infills are also commonly funnelled into prior and often linear negative relief forms relating to former migration within the mainstream channel belt 2016 the authors earth surface processes and landforms published by john wiley sons ltd shuttle radar topography mission srtm and landsat 8 data are used to map spillage form types and coverage along a 1700 km reach of the amazon that has an active floodplain width of up to 110 km with a systematic character transformation down valley spillage forms associated directly with mainstream processes rarely account for more than 5 of the floodplain deposits there is a marked decrease in floodplain point bar complexes pbc over 1700 km downstream from 34 to 5 and an increase in the prevalence of large water bodies 2 to 37 and accompanying internal crevasses and deltas 0 to 5 spillage sedimentation is likely within the negative relief associated with these forms depending on mainstream sediment laden floodwater inputs 2016 the authors earth surface processes and landforms published by john wiley sons ltd spillage style dominance depends on the balance between sediment loadings hydrological sequencing and morphological opportunity down river form sequences are likely to follow gradient change prior up river sediment sequestration and the altered nature of spilled loads but also crucially local floodplain relief and incident water levels and velocities at spillage times considering style distribution quantitatively as a spatially distributed set of identifiable forms emphasizes the global variety to spillage phenomena along and between large rivers 2016 the authors earth surface processes and landforms published by john wiley sons ltd

case study river training and its effects on fluvial processes in the lower yellow river china more than 50 years river training practices in the lower yellow river provide valuable experience in river management for flood control in rivers having rapid flow changes silting beds and active channel migrations and are of importance in understanding the fluvial processes in regulated rivers with high sediment loads planned channel alignments for river training in the lower yellow river usually consist of a series of consecutive moderate bends representing the natural tendency of flows flow guide works namely spur dikes were constructed on the concave banks of the planned bends to protect the channel against scouring and migration by deflecting the current away from bends and further guiding the main flow from one bend to the next one as a result well planned flow guide works can play a crucial role in limiting channel shifting and migration and in establishing a relatively stable channel enough flow guide works on both sides together reaching about 80 of the channel length may change the transitional and braided channel patterns to a confined meandering pattern

towards an understanding of the role of clay minerals in crude oil formation migration and accumulation this article reviews progress in the understanding of the role of clay minerals in crude oil formation migration and accumulation clay minerals are involved in the formation of kerogen catalytic cracking of kerogen into petroleum hydrocarbon the migration of crude oil and the continued change to hydrocarbon composition in underground petroleum reservoirs in kerogen formation clay minerals act as catalysts and sorbents to immobilize organic matter through ligand exchange hydrophobic interactions and cation bridges by the mechanisms of maillard reactions polyphenol theory selective preservation and sorptive protection clay minerals also serve as catalysts in acid catalyzed cracking of kerogen into petroleum hydrocarbon through lewis and bronsted acid sites on the clay surface the amount and type of clay mineral affect the composition of the petroleum bronsted acidity of clay minerals is affected by the presence and state of interlayer water and displacement of this water is a probable driver in crude oil migration from source rocks during crude oil migration and accumulation in reservoirs the composition of petroleum is continually modified by interaction with clay minerals the clays continue to function as sorbents and catalysts even while they are being transformed by diagenetic processes the detail of chemical interactions and reaction mechanisms between clay minerals and crude oil formation remains to be fully explained but promises to provide insights with broader application including catalytic conversion of biomass as a source of sustainable energy into the future

i s precipitation in pore space as the cause of geopressuring in mesozoic mudstones egersund basin norwegian continental shelf the role of clay diagenesis in pressure ramp overpressure development is evaluated from mesozoic mudstone well cuttings in the egersund basin norwegian continental shelf major changes in the mineral assemblage over the range of increasing geopressure include 50 decrease in detrital kaolinite in bulk material and increases in the proportions of illite i s and percent of nonexpandable illite like layers in i s sem and tem observations confirm that pore space is defined primarily by intersecting clay mineral packets at the scale of tens or hundreds of nanometers 0 01 0 1 m tem data document the reactions of kaolinite and detrital mica to form i s the principal reaction that occurred over the geopressure ramp was dissolution of kaolinite and precipitation of neoformed i s in pore space of these mudstones these changes also correspond to changes in 0 1 m particle populations as determined by pt c shadowed tem measurements as well as high resolution tem lattice fringe observations the neoformed i s has dimensions similar to those of the pore space in the mudstones the results support a mineralogical model of precipitation of diagenetic clay resulting in severe permeability reduction which can be related to the observed pressure ramp these observations and results provide an integrated petrologic framework for modeling pressure ramp development which had been difficult to achieve using conventional basin models of porosity and permeability evolution based on mechanical compaction

biodegradation of clay minerals laboratory experiments and results from wadden sea tidal flat sediments laboratory experiments indicate that clay particles of the 2 um fraction can be considerably degraded by the bivalve mytilus edulis dickite kaolinite smectite chlorite and illite particles are partially dissolved and rounded by the digestive processes structural changes and a decrease in crystallinity of kaolinites dickites and illites are striking investigations of clay minerals from tidal flat sediments highly populated by marine invertebrates from marine suspensions and samples from profiles across mytilis edulis beds on the north sea coast of germany show however that these materials have a uniform mineral composition this uniformity of clay mineralogy can be explained by the hydrodynamic conditions in the nearshore area where tidal currents and waves cause a periodic resuspension and transport of sediments introduced into the wadden sea from different sources glacial fluviatile processes of bioturbation also redistribute the sedimentary material these mixing processes effectively erase any evidence of local enrichment of the biogenically degraded clays however the disordered clays should react more sensitively i e have higher adsorption capacities for organic substances hydroxides and metals in sediments than untreated materials so that biodegradation is of basic importance for clay diagenesis during these processes pb v ni and fe are dissolved from the digested particles

the significance of large sediment supply active tectonism and eustasy on margin sequence development late quaternary stratigraphy and evolution of the ganges brahmaputra delta abstract borehole data from the ganges brahmaputra delta system unveil an intriguing late quaternary history controlled by immense sediment discharge tectonics and eustasy sea level first intersected a major portion of the lowstand surface 10 000 11 000 cal yr bp marking the onset of sediment trapping and delta growth despite rapid sea level rise 1 cm yr sediment load was sufficient to maintain relative shoreline stability during this time by 7000 cal yr bp accommodation was quickly infilled with slowed sea level rise leading to upstream channel migration and widespread dispersal of sands this forced coastal progradation along the western delta front where the ganges was situated and much of the river s fine grained discharge bypassed the subaerial delta and formed a prograding deltaic clinoform on the shelf concurrently brahmaputra sediments were sequestered to an inland tectonic basin thus starving the adjacent shoreline and leading to transgression along the eastern delta by 5000 cal yr bp the two rivers had migrated or changed course to discharge along the eastern delta shoreline which began to prograde into what is now the modern river mouth estuary present delta configuration appears to have developed by 3000 cal yr bp evolution of the tectonically active ganges brahmaputra g b system reveals important similarities and differences with other deltas overall facies succession follows that of basic models progressing from an alluvial valley to coastal marine delta front to a prograding subaerial delta plain however the timing thickness and controls of these deposits differ immense sediment discharge from the ganges and brahmaputra rivers allowed initial delta growth 2000 3000 yr earlier than the global average despite debouching onto a canyon incised high energy margin subsequently a thick 50 m transgressive systems tract was formed during the early holocene phase of delta aggradation contrasting with extensive shoreline retreat documented along most margins highstand progradation of coastal and shelf sequences ensued by the middle holocene but subsiding inland basins also favored accumulation of a thick to 40 m highstand sequence in the lower floodplains unlike many other delta systems subsidence in the subaerial g b delta is not dominated by compaction but rather by plate driven tectonic processes that generate rates up to 4 mm year overall the huge sediment load tectonic subsidence major seismic events and a nearshore canyon system have led to widespread sediment dispersal and sequence formation across the subaerial delta shelf and deep sea bengal fan throughout the late quaternary

late holocene depositional environments and coastal evolution of the mekong river delta southern vietnam abstract the mekong river delta in southern vietnam is a tide dominated delta and has been formed by the mekong river system the sediments are dominantly fine grained and were deposited in the receiving basin with slight inclination of pre existing deposits in the south china sea and gulf of thailand around 6000 to 5000 yr bp maximum holocene transgression occurred and seawaves surrounded uplands of the late pleistocene terrace basement rock and weathered land in the northern parts of the delta double notches were undercut by seawaves on the limestone hill in hatien at about 4 5 and 2 5 m above present sea level marine deposits prevailed throughout the delta during the highstand and regressions of relative sea level over the last 4550 yr bp delta progradation has produced a great flat plain of 62 520 km 2 this extremely fast progradation could be due to a very high sediment supply depositing in the slight inclination of the receiving basin b neotectonic movements and relative sea level changes c widespread mangrove forests playing an important role to enhance sediment accumulation former mangrove marshy deposits were significantly developed in the plain of reeds and longxuyen quadrangle mangrove marshes have also been developing well in the camau peninsula and present coastlines moreover regressions over the last 4550 yr bp have produced many distinct sets of relict beach ridges which are useful in distinguishing the former coastlines and evolutionary history of the delta

distinguishing between natural and anthropogenic sources of metals entering the irish sea international agreements e g ospar on the release of hazardous substances into the marine environment and environmental assessments of shelf seas require that concentrations and bioavailability of metals from anthropogenic sources can be distinguished from those originating as a result of natural geological processes the development of a methodology for distinguishing between anthropogenic and natural sources of metals entering the irish sea through river inputs is described the geochemistry of stream river and estuarine sediments has been used to identify background geochemical signatures related to geology and modifications to these signatures by anthropogenic activities the british geological survey bgs geochemical database based on stream sediments from 1 to 2 km2 catchments was used to derive the background signatures where mining activity was present the impact on the signature was estimated by comparison with the geochemistry of sediments from a geologically similar but mining free area river sediment samples taken upstream and downstream of major towns were used respectively to test the validity of using stream sediments to estimate the chemistry of the major river sediment and to provide an indication of the anthropogenic impact related to urban and industrial development the geochemistry of estuarine sediments from surface samples and cores was then compared with river and offshore sediment chemistry to assess the importance of riverine inputs to the irish sea studies were undertaken in the solway ribble wyre and mersey estuaries the results verify that catchment averages of stream sediments and major river samples have comparable chemistry where anthropogenic influences are small major urban and industrial including mining development causes easily recognised departures from the natural multi element geochemical signature in river sediment samples downstream of the development and enhanced metal levels are observed in sediments from estuaries with industrial catchments stream sediment chemistry coupled with limited river and estuarine sampling provides a cost effective means of identifying anthropogenic metal inputs to the marine environment investigations of field and laboratory protocols to characterise biological impact bioaccumulation of metals in sediments of the irish sea and its estuaries show that useful assessments can be made by a combination of surveys with bioindicator species such as clams scrobicularia plana selective sediment measurements that mimic the biologically available fractions and laboratory mesocosm studies

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

clay mineral organic matter relationships in the early solar system as the solar system formed it inherited and perpetuated a rich organic chemistry the molecular products of which are preserved in ancient extraterrestrial objects such as carbonaceous chondrites these organic rich meteorites provide a valuable and tangible record of the chemical steps taken towards the origin of life in the early solar system chondritic organic matter is present in the inorganic meteorite matrix which in the cm and ci chondrites contains evidence of alteration by liquid water on the parent asteroid an unanswered and fundamental question is to what extent did the organic matter and inorganic products of aqueous alteration interact or display interdependence we have used an organic labelling technique to reveal that the meteoritic organic matter is strongly associated with clay minerals this association suggests that clay minerals may have had an important trapping and possibly catalytic role in chemical evolution in the early solar system prior to the origin of life on the early earth