analysis of lake ice dynamics and morphology on lake el gygytgyn ne siberia using synthetic aperture radar sar and landsat 1 a time series of more than 450 combined ers 2 radarsat 1 and landsat 7 scenes acquired between 1998 and 2001 was analyzed to develop a fairly complete picture of lake ice dynamics on lake el gygytgyn ne siberia 67 5 n 172 e this 14 km3 lake partially fills a meteorite impact crater formed 3 6 million years ago and is home to a paleoenvironmental coring project the duration of lake ice cover and the onset of lake ice breakup are important both to interpretations of the archived sediment core record and to future drilling projects that will use the ice as a stable platform ice formation snowmelt and ice breakup likely occur in late october mid may and early july respectively these data were used to validate a one dimensional energy balance lake ice model which can now be used to hindcast paleoclimate based on core proxy information synthetic aperture radar sar backscatter from the lake ice also revealed unusual spatial variations in bubble content which were found to indicate the level of biological productivity in the sediments directly beneath the ice with the highest productivity located in the shallowest 0 10 m as well as the deepest 170 175 m regions of the lake seismic data indicates that the backscatter anomaly above the deepest water is collocated with the central peak of the impact crater 500 m below the surface several hypotheses are presented to explain this anomaly regardless of cause the fact that large spatial variations in biological productivity exist in the lake has important implications for selecting the locations of future sediment cores

sedimentary structure and origin of a mud cored pseudo tidal sand ridge eastern yellow sea korea abstract using high resolution seismic profiles sidescan sonar images and piston cores we have examined an elongate ridge located off the tae an peninsula of korea in the eastern yellow sea this ridge 50 km long 30 m high and up to 12 km wide is one of many similar longitudinal ones which are approximately parallel to the direction ne sw of strong tidal currents bathymetric profiles across the ridge are all asymmetric the eastern ridge flank is narrow and dips steeply towards the adjoining rocky valley below the eastern ridge flank less steeply sloping subbottom reflectors are truncated by a seafloor parallel erosion surface on which is draped a 45 cm thick unit of muddy sand a piston core taken here indicates that the subbottom reflectors are due to interlayered coarse sediments the more gently sloping western ridge flank contains sand waves ca 100 m wavelength ene wsw trend on which megaripples 10 15 m wavelength wnw ese trend are superimposed indicating recent bottom current activity in particular the reflectors beneath the westernmost ridge show westward progradation over an acoustically transparent unit of thin sand sheets however subbottom profiles collected over the ridge crest do not show conspicuous reflectors only a few discontinuous faint reflectors are observed the lack of conspicuous reflectors below the ridge crest area may reflect more thorough bottom current generated sediment homogenization as well as poor penetration of acoustic energy due to the current scoured rippled seafloor we interpret the ridge as an early holocene tidal mud tongue blanketed by recently reworked relict palimpsest sands the pseudo tidal sand ridge has prograded westward the fine mud tongue sediments might have been derived mostly from the korean peninsula via the han river at a time when sea level was lower than present

impact processes permafrost dynamics and climate and environmental variability in the terrestrial arctic as inferred from the unique 3 6 myr record of lake el gygytgyn far east russia a review lake el gygytgyn in far east russia is a 3 6 myr old impact crater lake located in an area that has never been affected by cenozoic glaciations nor desiccation the unique sediment record of the l

on vertical advection truncation errors in terrain following numerical models comparison to a laboratory model for upwelling over submarine canyons 1 submarine canyons which indent the continental shelf are frequently regions of steep up to 45 three dimensional topography recent observations have delineated the flow over several submarine canyons during 2 4 day long upwelling episodes thus upwelling episodes over submarine canyons provide an excellent flow regime for evaluating numerical and physical models here we compare a physical and numerical model simulation of an upwelling event over a simplified submarine canyon the numerical model being evaluated is a version of the s coordinate rutgers university model scrum careful matching between the models is necessary for a stringent comparison results show a poor comparison for the homogeneous case due to nonhydrostatic effects in the laboratory model results for the stratified case are better but show a systematic difference between the numerical results and laboratory results this difference is shown not to be due to nonhydrostatic effects rather the difference is due to truncation errors in the calculation of the vertical advection of density in the numerical model the calculation is inaccurate due to the terrain following coordinates combined with a strong vertical gradient in density vertical shear in the horizontal velocity and topography with strong curvature

active moribund and buried tidal sand ridges in the east china sea and the southern yellow sea shallow seismic profiles and borehole data revealed active moribund and buried tidal sand ridges in the east china sea and the southern yellow sea the ridges consist of relatively clean well sorted sands with fairly uniform sequences the microfossil assemblage exhibits a high diversity including both euryhaline and stenohaline species the ridges are huge elongated sand bodies several kilometres wide 10 60 km long and up to 20 m thick and occur in groups with a spacing of several to 10 km normally they are parallel with each other extending in the direction of the tidal currents the field of tidal sand ridges on the east china sea shelf covers an area of 57 000 km2 tidal sand ridges in the east china sea and the southern yellow sea were formed in estuarine and shallow shelf environments where strong tidal currents reworked transported and redeposited large amounts of relict sands from older deltaic and fluvial sediments the development of tidal sand ridges in estuary mouth areas is accompanied by a net sand transport from the shelf into the estuary the evolution of tidal sand ridges is closely related to transgressions active tidal sand ridges are formed during sea level rises they show distinct morphology and active migrations in a lateral as well as in a landward direction they are generally in equilibrium with present day tidal processes and their distribution patterns are related to the flow field of the tidal currents as the sea level rises further these tidal sand ridges become moribund sand bodies with less distinct morphologies their upper surfaces are covered by a thin calcareous rich layer with very high contents of foraminifera tests reflecting a submarine hiatus condition on the shelf during the highstand period during the subsequent steady fall in sea level tidal sand ridges are often buried by fine grained shelf and prodelta sediments they have therefore a good chance of being preserved in stratigraphic records the sequential buildup during a sea level rise tr tract and a subsequent sea level fall hs and ls tract would consist of estuarine channel and tidal flat facies tidal sand ridge facies shelf mud facies delta facies and fluvial facies in an ascending order tidally dominated estuary conditions may also occur when a major distributary is abandoned such as at the northern branch of the modern changjiang river mouth where the accumulation of sand from an abandoned delta lobe and the development of tidal sand ridges have been observed the observed features have important implications for the subsurface recognition of fossil tidal sand ridges for the reconstruction of the regional palaeogeography and transgressional history and for the prediction of potential reservoir sandstones

chromium isotope anomaly in an impactite sample from the el gygytgyn structure russia evidence for a ureilite projectile the 3 6 ma 18 km diameter el gygytgyn impact structure arctic russia is unique among the currently known terrestrial impact craters in that it is the only one that was formed in acid volcanic rocks previous analyses of impactites from el gygytgyn showed minor enrichments of the siderophile elements including ir which together with distinct cr enrichments gave rise to speculation that an achondritic projectile was involved we studied the major and trace element composition in samples from the new icdp drill core obtained near the center of the structure as well as the chromium isotopic composition of an impact glass sample collected on the surface several suevitic breccias from the upper part of the suevite sequence in the drill core show higher cr and ni contents compared with felsic volcanic rocks in the lower part of the core and from surface samples however it is difficult to unambiguously establish a meteoritic component from trace element data as input from rare mafic target rocks is a possibility in contrast the cr isotopic composition of the impact glass sample yielded a nonterrestrial e 54 cr value of 0 72 0 31 2 std err this negative e 54 cr is different from known carbonaceous chondrite values e 54 cr of 0 95 to 1 65 but is nearly identical to reported values for ureilites approximately 0 77 the value is however also within analytical error of eucrites approximately 0 38 and ordinary chondrites approximately 0 42 given the chemical signatures found in previous analyses of el gytgytgyn impactites and the similarity of our cr isotopic data to ureilites we suggest that the impacting asteroid could have been an f type asteroid of mixed composition similar to the recent almahata sitta fall in sudan

stratigraphy of late quaternary deposits using high resolution seismic profile in the southeastern yellow sea abstract high resolution chirp and sparker system seismic profiles were analyzed to investigate the sequence stratigraphy of late quaternary deposits in the southeastern yellow sea approximately 1560 line km data of chirp and sparker profiles were acquired together with 11 piston cores two previous long drill cores ysdp 102 and 103 were used for comparison with seismic data high resolution seismic profiles image the holocene mud deposits and the complex sedimentary structure in this area sequence analysis of high resolution seismic profiles reveals that the shelf deposits form a succession of high frequency five order sequences consisting of one depositional sequence developed during the late quaternary the depositional sequence includes five sedimentary units each with different seismic facies and geometry 1 incised channel fill and lowstand deltaic wedge unit sy1 2 sand ridges unit sy2 3 estuarine deltaic mud unit sy3 4 redeposited mud unit sy4 and 5 recent distal mud unit sy5 based on the interpretation of high resolution seismic records and correlation with the ysdp 102 103 long cores and piston cores late quaternary deposits in the southeastern yellow sea consists of a set of the lowstand unit sy1 early transgressive unit sy2 middle transgressive unit sy3 late transgressive unit sy4 and highstand systems tract unit sy5 formed since the last glacial period the rather unusual stratigraphic architecture including three systems tracts is largely controlled by the postglacial sea level changes and regionally circulation pattern associated with sediment erosion and redeposition the results of this study present firstly clear seismic evidence that the southeastern yellow sea mud belt seysm can be divided into three stratigraphic units units sy3 sy4 and sy5 bounded by distinct bounding surfaces

complex sedimentation of the holocene mud deposits in a ria type coastal area eastern korea strait abstract the innermost shelf of the eastern korea strait is a ria type coastal sea comprising islands intervening passageways and embayments a detailed analysis of high resolution 1 10 khz subbottom profiles and core sediments from this area reveals complicated depositional and distributional patterns of the holocene mud deposits related to complex topography with varying supply of the adjacent nakdong riverine sediments sediments from the nakdong river were bifurcated around gadeok island forming two proximal systems nakdong and western gadeok systems these proximal systems prograded offshore southward by active sediment supply from the nakdong river in the early stage suspended sediments passing through the nakdong system formed the distal gadeok waterway and eastern geoje systems in the area between the northern geoje and gadeok islands these distal systems show a northwestward onshore prograding tendency to jinhae bay the biggest bay in the vicinity of the nakdong estuary in which the jinhae bay system developed in the late stage a remarkable decrease of sediment supply from the nakdong river has caused retrograding geometry of the two proximal systems however the most distal jinhae bay system has continuously prograded bayward due to the persistent supply of sediments resuspended by strong tidal currents from nearby distal gadeok waterway and eastern geoje systems these complex depositional features indicate that topography has an important influence on depositional developments of the holocene mud deposits by controlling path and intensity of sediment dispersal and resuspension processes

a review on the provenance discrimination of sediments in the yellow sea the yellow sea has been extensively studied for the understanding of dispersal patterns and limits of sediments from neighboring countries including china and korea although sedimentological mineralogical and geochemical approaches have been tried to solve the problems especially including the identification of sediment sources in and around the yellow sea the published results are not enough for understanding them suggestions on sediment origins budgets sediment accumulation rates mineralogical and geochemical compositions are not coincident to each other and sometimes even controversial for example conflicts on the distribution patterns of smectite and calcium carbonate the provenance of the southeastern yellow sea mud and sedimentation rates in there the ratios of v al and mn al in korea and china river sediments the origin of ba and pb in sandy sediments of the northeastern yellow sea and so on various geochemical indicators from the literature for the provenance discrimination in the yellow sea are reviewed here in depth and corresponding discussions are described separately research topics for the future study also are suggested for the proper access to the understanding of the origin and dispersal patterns of the yellow sea sediments especially focusing on the geochemical approaches d 2003 elsevier science b v all rights reserved

world wide delivery of river sediment to the oceans new data and new estimates from old data show that rivers with large sediment loads annual discharges greater than about 15 times 10 6 tons contribute about 7 times 10 9 tons of suspended sediment to the ocean yearly extrapolating available data for all drainage basins the total suspended sediment delivered by all rivers to the oceans is about 13 5 times 10 9 tons annually bedload and flood discharges may account for an additional 1 2 times 10 9 tons about 70 of this total is derived from southern asia and the larger islands in the pacific and indian oceans where sediment yields are much greater than for other drainage basins

partitioning of transgressive deposits in the southeastern yellow sea a sequence stratigraphic interpretation abstract the last glacio eustatic sea level fluctuation in the southeastern part of the yellow sea formed a number of unconformity bounded sedimentary sequences these sequences comprise 1 regressive to transgressive incision fills unit c 2 transgressive sand ridges and swales unit b and 3 transgressive to highstand muds lower mud unit a2 upper mud unit a1 the sequence boundary between unit c and the lower unit comprises erosional surface which can be traced for the entire study area the even and sharp boundary between the incision fills unit c and the sand ridges unit b represents a transgressive surface of erosion the depositional boundary between the lower mud unit a2 and the upper mud unit a1 suggests a change in oceanographic conditions the boundary is confined landward and correlated offshore with the top of units b and c that is exposed on the seafloor these transgressive deposits show partitioning controlled by currents tides and sediment supply as well as physiography of the seafloor

acoustic and biological characteristics of seafloor depressions in the north yellow sea basin of china active fluid seepage in shallow water seafloor abstract high resolution multibeam bathymetry revealed the occurrence of numerous craterlike depressions so called pockmarks in the sea floor of the north yellow sea basin nysb to investigate whether these pockmarks are related to any type of fluid flow or gas seepage from subsurface stratum acoustic survey and box samplings were conducted in a selected area containing several typical pockmarks this allowed for an integrated analysis of the morphology distribution and subsurface strata as well as a direct comparison of seafloor characteristics among different areas inside and outside of a pockmark additionally surface sediments were analyzed for particle structure and grain size based on the combination of multibeam bathymetry and backscatter intensity data 282 seafloor depressions were accurately identified moreover the formation of pockmark can be attributed to existence of gas chimneys and other shallow gases revealed by shallow seismic profile records in the subsurface strata sediments inside and outside the pockmark showed remarkable discrepancies in terms of grain size and benthic fauna additionally strong internal reflection area was observed inside the depressions where benthic habitats are abundant and sediments contain strawberry pyrite and carbonate cementation side scan sonar also recorded sediment plumes in the water column which indicates that the pockmarks are still active several pearl string like accumulations of pockmark were found in the study area which well agree with the distribution of buried channels and lakes these results thus provide new insights in interpreting shallow water fluid seepage with implications for our current knowledge of overall sedimentation process in offshore continental shelves

tidally incised valleys on tropical carbonate shelves an example from the northern great barrier reef australia the formation of incised valleys on continental shelves is generally attributed to fluvial erosion under low sea level conditions however there are exceptions a multibeam sonar survey at the northern end of australia s great barrier reef adjacent to the southern edge of the gulf of papua mapped a shelf valley system up to 220 m deep that extends for more than 90 km across the continental shelf this is the deepest shelf valley yet found in the great barrier reef and is well below the maximum depth of fluvial incision that could have occurred under a 120 m eustatic sea level low stand as what occurred on this margin during the last ice age these valleys appear to have formed by a combination of reef growth and tidal current scour probably in relation to a sea level at around 30 50 m below its present position tidally incised depressions in the valley floor exhibit closed bathymetric contours at both ends valley floor sediments are mainly calcareous muddy gravelly sand on the middle shelf giving way to well sorted gravely sand containing a large relict fraction on the outer shelf the valley extends between broad platform reefs and framework coral growth which accumulated through the late quaternary coincides with tidal current scour to produce steep sided locally vertical valley walls the deepest segments of the valley were probably the sites of lakes during the last ice age when torres strait formed an emergent land bridge between australia and papua new guinea numerical modeling predicts that the strongest tidal currents occur over the deepest outer shelf segment of the valley when sea level is about 40 50 m below its present position these results are consistent with a pleistocene age and relict origin of the valley based on these observations we propose a new conceptual model for the formation of tidally incised shelf valleys tidal erosion on meso to macro tidal rimmed carbonate shelves is enhanced during sea level rise and fall when a tidal hydraulic pressure gradient is established between the shelf lagoon and the adjacent ocean basin tidal flows attain a maximum and channel incision is greatest when a large hydraulic pressure gradient coincides with small channel cross sections our tidal incision model may explain the observation of other workers that sediment is exported from the great barrier reef shelf to the adjacent ocean basins during intermediate rather than last glacial maximum low stand sea level positions the model may apply to other rimmed shelves both modern and ancient

a high resolution record of rare earth element compositional changes from the mud deposit on the inner shelf of the east china sea implications for paleoenvironmental changes abstract a paleoenvironmental reconstruction of the east china sea ecs is presented using rare earth element ree analysis of sediments from core mz02 which was retrieved from the inner continental shelf s mud area the analytic results show that the total rees in the fine sediment vary between 137 76 g g and 231 53 g g with an average value of 187 69 g g obvious changes were found during the process of sedimentation by comparing with the ree compositions from the potential provenances the ratios of la sm ucc and gd yb ucc revealed that the sediments were mainly derived from river detrital outputs of the changjiang yangtze river minjiang and mountainous rivers from western taiwan island the contributions of terrestrial materials from these three main provenances were controlled by sea level change and the taiwan warm current twc chinese coastal current ccc system which is mainly driven by the east asian monsoon the high sedimentation rate during the transgression period between the late pleistocene and early holocene 13000 9800 a b p was caused by a well proportioned mixed provenance from changjiang western taiwanese rivers and minjiang sediments due to the lower sea level and the location of the foreshore nearshore face because of the stronger sediment reworking and erosion at the shelf edge during the early holocene 9800 7300 a b p the strengthening summer east asian monsoon transported the minjiang and western taiwanese river material northeastward and it became the main sediment source for fine sediments in the shallow sea region of the ecs while the changjiang provided a relatively minor amount of detrital sediment to the shelf the increasing strength of the twc might have played an important role in sediment dispersal and deposition on the ecs inner shelf during the period 7300 3500 a b p thus mountainous river material became the dominant sediment on the shelf of the ecs furthermore the results indicate that the east asian monsoon and the weakening of the twc were linked to an abrupt increase in changjiang derived terrigenous detritus material since 3500 a b p the source and sink pattern during this period is consistent with the modern sedimentation environment

spatial and temporal distributions of clay minerals in mud deposits on the inner shelf of the east china sea implications for paleoenvironmental changes in the holocene abstract we present a paleoclimatic reconstruction for the holocene by clay mineral analyses of sediments from core mz02 retrieved from the mud area of the inner continental shelf of the east china sea ecs the clay minerals mainly consist of illite 66 79 and chlorite 12 19 with minor kaolinite 7 13 and smectite 0 6 provenance analysis suggests that the illite dominated clay minerals were derived mainly from the detrital outputs of the changjiang minjiang and small rivers from taiwan island our study indicates that the sea level rise since the last glacial the strength of the taiwan warm current twc and chinese coastal current ccc have controlled the dispersal and deposition of clay minerals on the ecs that in turn determined the clay mineral compositions in the core sediments during 13 000 9500 bp due to the lower sea level and shorter distance between these three estuaries and core mz02 fine sediments on the inner shelf of the ecs were primarily supplied by mixed provenances from the changjiang taiwanese and minjiang rivers during the early holocene 9500 6200 bp stronger sediment reworking and erosion at the shelf edge was responsible for the increased lateral transport of fine sediments in the ecs which lead to a dominance of the sediment source from the changjiang while the taiwanese and minjiang rivers only provided minor components of detrital sediment to the shelf increased strength of twc might have played an important role in the sediment dispersal and deposition on the inner shelf of the ecs during 6200 2400 bp with a dominance of more than 60 sediments transported from taiwanese rivers furthermore our study implies that the asian monsoon and the weakening of twc were linked to the abrupt increase of changjiang and minjiang derived terrigenous detritus materials since 2400 bp

new insights on the post rift seismic stratigraphic architecture and sedimentary evolution of the antarctic peninsula margin central bransfield basin abstract a seismic stratigraphic study of the antarctic peninsula margin of the central bransfield basin was conducted using seismic and bathymetric data the study focused on seismic sequences and units deposited after the basin opened and yield a record of the evolution of the northern most antarctic peninsula ice sheet two seismic sequences compose the post rift stratigraphic succession on the central bransfield basin slope platforms both sequences are composed of seismic units that record glacial interglacial cycles and show evidence of the antarctic peninsula ice sheet having grounded on the continental shelf and slope platform on several occasions in the past this evidence includes glacial and glaciomarine related sedimentary and erosional features within the seismic units glacial unconformities glacial troughs till wedges prograded wedges trough mouth fans glaciomarine sheet deposits and moraines which are bounded by glacial unconformities the antarctic peninsula lower slope also registered in its eastern sector the deposition of gravity flow deposits during ice sheet retreat and interglacial stages the deposition of seismic units on the middle slope produced the present day step like profile of the margin composed of wide flat slope platforms and narrow and steep upper and lower slopes seismic units show changes in thickness and distribution that record the effect of the physiography and climatic changes on margin sedimentation these variations produced an overall change from more line sourced deposition to more point sourced deposition as ice streams evolved the stacking of units shows a change in the stratigraphic architecture through time from dominantly progradational s2 to progradational aggradational s1 this change is correlated with a change in the frequency of ice sheet grounding events which was probably driven by a higher rate of eustatic rise and fall in relation with the mid pleistocene global climatic change

el gygytgyn impact crater russia structure tectonics and morphology the 3 6 myr old el gygytgyn impact crater is located in central chukotka northeastern russia the crater is a well preserved impact structure with an inner basin about 15 km in diameter surrounded by an uplifted rim about 18 km in diameter the flat floor of the crater is in part occupied by lake el gygytgyn 12 km in diameter and surrounding terraces the average profile of the rim is asymmetric with a steep inner wall and a gentle outer flank the rim height is about 180 m above the lake level and 140 m above the surrounding area an outer ring feature on average 14 m high occurs at about 1 75 crater radii from the center of the structure el gygytgyn crater is surrounded by a complex network of faults the density of the faults decreases from the bottom of the rim to the rim crest and outside the crater to a distance of about 2 7 crater radii lake el gygytgyn is surrounded by a number of lacustrine terraces only minor remnants are preserved of the highest terraces 80 and 60 m above the present day lake level the widest of the terraces is 40 m above the current lake level and surrounds the lake on the west and northwest sides the only outlet of the lake is the enmivaam river which cuts through the crater rim in the southeast in terms of structure el gygytgyn is well preserved and displays some interesting but not well understood features e g an outer ring similar to those observed at a few other impact structures

sediment distribution dispersal and budget in the yellow sea abstract information on the surface sediment distribution in the yellow sea is newly compiled based on all available data produced by chinese and korean workers and is used to refine the dispersal patterns and budget of sediments derived from the adjoining landmass the central yellow sea is largely covered with fine grained sediments originating from the huanghe river 2 2 10 8 t yr about 20 of the total discharge thick sediment accumulation exceeding 5 mm yr occurs in the gulf of bohai and around the shandong peninsula about two thirds of the total huanghe river discharge the old huanghe delta suffers from reworking by strong tides and waves and forms a mud patch southwest of cheju island accumulation rate 2 10 7 t yr more than half of the sediments derived from the changjiang river are deposited along the coast of the east china sea the remainder accumulate on the inner shelf off the river mouth in the southeastern yellow sea the keum river dominates sediment discharge forming a holocene mud belt along the southwestern coast of korea accumulation rate 5 10 6 t yr turbid water plumes occur nearshore throughout the year and their suspended sediments are transported along the tip of the peninsula to the western coastal embayments in the south sea the nakdong river discharge of 1 10 7 t yr is responsible for the eastern nearshore mud of the south sea relict sands occur in the northern part of the yellow sea in the northern east china sea and in the korea strait

magnetostratigraphic results from impact crater lake el gygytgyn northeastern siberia a 300 kyr long high resolution terrestrial palaeoclimatic record from the arctic summary a 12 7 m long sedimentary record recovered from lake el gygytgyn located in a meteorite impact crater created 3 6 ma in late cretaceous igneous rocks on chukotka peninsula northeast siberia has been analysed for its palaeo and rock magnetic properties continuous high resolution 1 mm measurements of magnetic susceptibility yielded successions of pronounced lows and highs analyses of the rock magnetic properties by low and high temperature runs of magnetic susceptibility determination of hysteresis parameters as well as irm acquisition experiments yielded a dominance of psd pseudo single domain magnetite in intervals of high magnetic susceptibility whereas due to selective magnetite dissolution associated with anoxic lake water and or pore water conditions during times of enhanced deposition of organic matter haematite dominates within low susceptibility intervals in terms of mass percentage here however magnetic properties are still dominated by magnetite five ams accelerator mass spectromentry 14 c ages eight irsl infrared stimulated luminescense ages together with preliminary pollen data suggest that variations in magnetite content reflect climatic variability of the last 300 ka with low high susceptibilities representing cold warm climates this pattern caused by a complex system of deposition preservation or decomposition of organic matter and or magnetic minerals in turn can be correlated in detail to global climate archives such as the oxygen isotope records from greenland ice cores and marine sediments respectively thus the sedimentary sequence recovered from lake el gygytgyn represents the longest continuous terrestrial climate record now available from the arctic

distribution of suspended sediment in the korea strait and southeastern yellow sea onset of winter monsoons abstract high energy conditions in the yellow sea begin each year with the onset of monsoon winds in late october these transitional season surges of cold air initiate sediment resuspension vertical mixing of suspended sediments and a wind driven coastal current that flows to the south during the summer to winter transition suspended sediment concentrations in the southeastern yellow sea range from 5 100 mg l 1 at the surface and 5 500 mg l 1 at the bottom the highest concentrations occur off the southwest tip of the korean peninsula and the lowest occur in the central part of the korea strait the rate of transitional season destratification may depend on the timing and intensity of monsoonal surges whereas a late onset of monsoon winds allows waters to remain longer in their moderately stratified summer condition an early onset of monsoon winds tends to destratify the water column by mid november resulting in a nearly uniform high concentration of suspended sediments from surface to bottom the band of more turbid coastal water ends abruptly 25 50 km offshore as a turbidity front in waters 20 80 m deep a wind driven residual flow to the south appears to transport large volumes of this turbid water into the korea strait and perhaps as far as the sea of japan

depositional development of an isolated mound and adjacent area in the southern yellow sea during the last postglacial sea level rise abstract a detailed analysis of the chirp 2 7 khz profiles core sediments and 14c ages from an isolated mound and adjacent area in the southern yellow sea off the jiangsu coastal area reveals a highly complex development of transgressive and highstand deposits during the last postglacial sea level rise in water depths of 50 60 m the terrace consists of thin transgressive sediments directly above transgressive surface the isolated mound 40 7 km long and 29 6 km wide occurs above 40 50 m in water depth and is detached from the jiangsu and east china sea tidal sand ridges it comprises the sse ward prograding sandy unit pu and the overlying muddy flank unit fu at the outer margin the terrace with thin transgressive sediments was most likely formed when sea level rose rapidly from 58 to 45 m around about 11 6 ka as rate of sea level rise was attenuated from 45 to 36 m between ca 11 6 and 9 6 ka the nearly flat lower boundary of the pu was produced at water depths of 37 42 m by a ravinement process subsequent rapid sea level rise from 36 to 16 m between ca 9 6 and 9 1 ka created accommodation for deposition of the pu sea level rise stagnated from 16 to 10 m between ca 9 1 and 7 5 ka during which the huanghe river apparently shifted south of the shandong peninsula and discharged directly into the western yellow sea the combination of slow sea level rise and sediment supply from the early holocene huanghe delta by the southward flowing coastal currents most likely favoured the formation of the sse ward prograding transgressive sandy pu the highstand muddy fu overlying the pu was accumulated after ca 7 5 when sea level approached its present position and the huanghe river shifted back to the north development of transgressive and highstand deposits in the study area during the last postglacial sea level rise was highly variable in time and space in response to changes in rate of sea level rise together with variations in sediment supply caused by the shifting of the huanghe river

tide and wave dynamics on a sand bank from the deep shelf of the western channel approaches abstract the sedimentary response of deep shelf sediments to the interplay of tides and waves based on the example of the celtic sea sand banks is described grab samples and 1500 km of multibeam and side scan data have been collected from the 300 km2 densely surveyed kaiser bank area the bank is 140 170 m deep 30 m high and 60 km long oriented perpendicular to the shelf edge and nearly parallel to the major axis of the tidal ellipse surficial sediments of the bank consist of medium to gravely biolithoclastic sands they are swept by tidal currents that reach 0 9 m s 1 m above the seabed and under the occasional influence of waves the mobile sands are commonly bedformed and rest on a highly backscattering lag the flanks below 140 m mainly exhibit transverse tidal dunes and sand ribbons whereas the top of the bank mostly displays discontinuous sand patches and wave ripples the sand patches are interpreted as the remnants of tidal bedforms reworked by waves calculations of the threshold of motion of four modal grain sizes under various conditions at the seabed show that tidal bedforms are active during spring tides sometimes associated with waves whereas only the largest annual waves may explain the observed wave ripples as in active tidal banks there is a reversal of tidal bedload transport from one bank side to the other the sedimentation rate is very low on the kaiser bank in addition there is a loss of sediment at both bank extremities and the tidal bedload cross bank transfer is very small probably controlled by shelf residual currents and long term drift of sediment resuspended by waves however the present day action of waves at the bank top is less intense than it was at lower sea levels during the holocene as evidenced by seismic studies

dispersal of fine grained sediments in the southeastern yellow sea a steady state model a large portion of the yellow sea is floored by fine grained clastics derived largely from the hwangho and yangtze rivers in the southeastern yellow sea however coarse grained sediments prevail derived probably from the short and steep korean rivers farther east the coarse grained sediments contain substantial amounts of fine fractions near the keum estuary detrital clays such as kaolinite and chlorite are abundant in the free fractions and this trend extends for about 120 km both toward the northwest and the southwest illite appears to be dominant in the rest of the yellow sea the data suggest that the bulk of fine grained sediments in the southeastern yellow sea originates from the keum river the sediments are subsequently transported by prevailing nearshore currents both northwestward during summer and southwestward in winter the tidal currents may also play a role the close correspondance between the oceanographic data and the mineralogic evidence suggests that the dispersal of fine grained sediments in the southeastern yellow sea occurs largely under the steady state conditions

quantitative reconstruction of holocene sediment source variations in the yellow and northern east china seas and their forcings abstract sediment provenance in the yellow sea and northern east china seas yecss has long been a subject of interest but its quantification is still inconclusive here we present an improved al mg regression analysis by refining its methodological approach to strengthen quantification of sediment source to sink transports in the yecss with focus on its forcing mechanisms during the holocene our quantitative source estimates clearly depict a considerable supply of the chinese river cr sediments 50 to the southwestern korean coastal region and the korean river kr sediments 30 40 to the central yellow sea mud deposit which accounts for a good balance between the sediment supply and budget of the shelf deposit of particular note is an abrupt decline in the cr contributions around 124 e which indicates that the cr sediments do not directly reach the eastern part of the yellow sea blocked by a strong physical boundary further the observed variations in proportions between huanghe changjiang and korean river derived sediments over the last 15 kyr notably an abrupt increase of cr contribution since 7 ka followed by a sudden drop at 3 4 ka exhibit a good correspondence with other mineralogical proxy records these temporal provenance changes witnessed robust palaeoenvironmental signals which fit to major climatic and oceanographic events linked with sea level intensity of the kuroshio current inflow and the east asian monsoon this study improves understanding of what pathways and sinks exist within the yecs basin and how rates of sediment supply from adjacent rivers have changed over time

the relative importance of gravity induced versus current controlled sedimentation during the quaternary along the mideast u s outer continental margin revealed by 3 5 khz echo character abstract a detailed echo character map based on more than 50 000 km of 3 5 khz echograms reveals the relative importance of contour currents turbidity currents and mass wasting processes for the upper 50 100 m of sea floor sediments along the u s continental margin between southern georges bank and cape hatteras nineteen individual echo types are mapped and interpreted as deposits produced either by current controlled or gravity induced processes based on echo type distribution analysis of selected sediment core samples and the published results of other workers turbidity currents and mass wasting have apparently been the primary depositional agents throughout 60 of the region in contrast contour currents alone appear to have influenced only 10 of the region however combined processes i e non separable interaction between downslope and parallel to contour processes have influenced an estimated 25 of the margin the remaining 5 of the study area constitutes the outermost continental shelf echo types here reflect the influence of fluvial deltaic and shallow marine sedimentary processes changes in the relative distributions of various echo types with sea floor depth indicate that the dominant sedimentary processes change downslope and are significantly different within each physiographic province deposits formed by mass wasting dominate the continental slope where 50 of the sea floor is eroded and gullied by slides slumps and the heads of debris flows deposits developed under the influence of combined processes are most wide spread on the upper continental rise and cover 40 of the sea floor primarily in the form of deep sea channel levees modified by contour currents on the lower continental rise turbidites form more than 50 of the sea floor deposits the downslope deposits turbidity currents slumps debris flows etc were emplaced primarily during the pleistocene glacioeustatic sea level lowering moved beaches and rivers across the exposed continental shelf to the shelf edge where massive fluxes of terrigenous sediment could be delivered to the continental slope and rise by turbidity currents significant amounts of this sediment were transported through submarine canyons and leveed deep sea channels to the lower continental rise and formed the lower continental rise terrace a flat turbidite basin ponded behind the hatteras outer ridge southwest of the wilmington channel this glacially derived influx was diminished however depositional patterns indicate that downslope processes continued to be dominant at least as far south as cape hatteras where rapid deposition on the continental slope and uppermost continental rise created instabilities slope failure produced slumps slides and debris flows and provided an additional volumetrically important redistribution of sediment downslope the influence of contour currents is clearly observed only in those areas topographically shielded from the masking effects of downslope processes in particular along the seaward side of the buried chesapeake drift and the hatteras outer ridge

high resolution acoustic characteristics of epicontinental sea deposits central eastern yellow sea abstract large amounts 45390 line km of closely spaced 2 2 4 4 km high resolution subbottom profiles chirp 2 7 khz made it possible to identify detailed echo types and their distribution in an epicontinental shelf environment on the basis of seafloor morphology surface bedforms and subbottom acoustic characters 10 echo types were identified in the uppermost sedimentary sequence of the central eastern yellow sea flat seafloor with sharp bottom echoes echo types 1 1 1 2 and 1 3a transgressive sediment sheets or relict sands is widespread in the offshore area and underlain to the west by an acoustically transparent wedge echo type 1 3b highstand muds mounded seafloor with either smooth surface or superposed bedforms echo types 2 1 2 2 and 2 3 tidal ridges and flat seafloor with regularly spaced wavy bedforms echo type 1 4 large scale dunes are dominant in the eastern nearshore area large scale mounds with continuous inclined internal reflectors echo type 2 4 giant mud bank occur in the southeastern nearshore area various scale eroded seafloor echo types 3 1 and 3 2 channels and flat seafloor with regularly spaced wavy bedforms echo type 1 4 large scale dunes are present in the northern part of the sea the distribution pattern of echo types in the central eastern yellow sea reflects depositional processes and sediment dispersal systems during the holocene transgression and highstand period 1 development of tidal ridges and large scale dunes in response to strong tidal currents and waves in the eastern nearshore area 2 construction of transgressive to highstand mud bank huksan mud belt by deposition of muds derived from the keum river in the southeastern nearshore area 3 active erosion due to intensified currents in the northern part and 4 highstand mud deposition derived from the huanghe river on the transgressive sediment sheets in the offshore area

roter kamm impact crater namibia geochemistry of basement rocks and breccias abstract the roter kamm crater in the southern namib desert has previously been identified as an impact structure on the basis of crater morphology and the presence of impact melt breccias which contain shock metamorphosed quartz and lithic clasts to better define the variety of target rocks and breccias we studied the petrography and chemical composition of a new suite of twenty eight basement and breccia samples from the roter kamm crater based on chemical data for target lithologies and breccias we suggest that the crater was formed in a two layer target region an upper layer of gariep metasediments schist marble quartzite and sandstone overlying the crystalline basement of the namaqualand metamorphic complex the basement was also heavily intruded by coarse grained quartz veins and quartz and quartz feldspar pegmatites the clast population in the melt breccias indicates that impact induced melting involved mainly metasedimentary target rocks with rarely detected contributions from pegmatite and granite granodiorite three varieties of melt breccias can be defined 1 schistose 2 quartzitic melt breccias 3 true impact melt breccias these melt breccia types are chemically heterogeneous and even the impact melt breccias may have been produced in situ and not from a coherent melt body the shapes of the schistose melt breccias previously thought to be ejected impact breccias are most likely caused by erosion and these breccias are now interpreted to be locally derived the crater basement as exposed at the rim was structurally severely affected and at least locally considerable thermal energy was generated during formation of large volumes of cataclastic mylonitic and pseudotachylitic breccias analyses of mylonite and pseudotachylites from the crater rim as well as their respective host rocks show that these breccias were mainly formed from local material analyses of pseudotachylite like breccias indicate that these possible friction melts are generated by preferential melting of hydrous ferromagnesian minerals and feldspar similar to their tectonically produced counterparts although no significant fluid effects resulting from formation of mylonites or pseudotachylites are indicated several breccias compared to their host rocks do show evidence of severe chemical alteration chloritisation and sericitisation the presence of large vesicles filled with hydrothermal mineral assemblages in some schistose breccias and other petrographic and chemical data support the hypothesis of an impact induced hydrothermal event in the crater area

lithostratigraphy of the impactite and bedrock section of icdp drill core d1c from the el gygytgyn impact crater russia in 2008 2009 the international continental scientific drilling program icdp obtained drill cores from the el gygytgyn impact structure located on the chukotka peninsula russia these cores provide the most complete geological section ever obtained from an impact structure in siliceous volcanic rock the lithostratigraphy comprises a thick sequence of lacustrine sediments overlying impact breccias and deformed target rock the interval from 316 m below lake floor blf to the end of the core at 517 m depth can be subdivided into four lithological sequences at 316 m depth the first mesoscopic clasts of shocked target rock occur in lacustrine sediments the growing abundance of target rock clasts with increasing depth and corresponding decrease of lacustrine sediment components indicate the extent of this transition zone to 328 m depth it constitutes a zone of mixed reworked impact breccia and lacustrine sediments volcanic clasts in this reworked suevite section show all stages of shock metamorphism up to melting the underlying unit 328 390 m depth represents a suevite package a polymict impact breccia with considerable evidence of shock deformation in a wide variety of volcanic clasts this includes fragments with quartz that exhibit planar fractures and planar deformation features pdf in addition at three depths several centimeter sized clasts with shatter cones were detected due to microanalytical identification of relatively rare microscopic impact melt particles in the matrix of this breccia this material can be confidently labeled a suevite also in this sequence three unshocked 1 m thick intersections of volcanic blocks occur at 333 83 351 52 and 383 00 m depths the upper bedrock unit begins at 390 74 m depth has a thickness of 30 15 m and represents a sequence of different volcanic rocks an upper part with basaltic composition from 390 74 to 391 79 m depth overlying a lower rhyodacitic part from 391 79 to 420 27 m depth this parautochthonous basement unit is only very weakly affected by the impact only one shocked quartz grain with two sets of pdf was recorded at 391 33 m depth the lower bedrock unit 420 89 517 09 m depth end of core is a brittly deformed rather homogeneous welded ignimbrite that in part can be considered a cataclasite the top three meters of this section are sheared which could represent pre impact tectonic deformation a 54 cm thick injection of polymict impact breccia occurs at 471 42 471 96 m depth

recent sedimentary processes in the prestige site area galicia bank nw iberian margin evidenced by high resolution marine geophysical methods an echo character analysis of the oil tanker prestige wreck area was undertaken using high resolution marine geophysical methods topas and airgun seismic reflection profiles multibeam echosounder and tobi sidescan sonar integration and comparison of the results using all these methods is presented given some practical applications for indirect near surface and seafloor interpretations ten different echo types were identified and grouped into four main classes i distinct ii indistinct iii irregular and iv hyperbolic echo character distribution enabled us to determine recent sedimentary processes in the area two major depositional systems can be found through the identification of these sedimentary processes a a slope depositional system sds located in the eastern and central area where mass movement processes are dominant and b a turbiditic main channel depositional system tds located in the western area where channel related processes are dominant both of these interact over the half graben structure of the southwestern sector of the galicia bank where the prestige wreck is located within the sds erosive and depositional mass movement processes characterised a complex depositional system erosive processes occur on the fault scarp channels head inter lobe channels and distal part of the sedimentary lobes moreover depositional processes take place on the top of the fault scarp sedimentary wedges sedimentary lobes and on the west flank of the main channel both depositional systems interact but the sds should be more active during fault scarp reactivation periods through relief rejuvenation and new exposed deposits microearthquake activity would favour the available materials being weathered eroded and transported by mass movements in such a situation the tds acts as the main collector of eroded sediment derived from the fault scarp throughout the sds being responsible for its evacuation into the iberian abyssal plain however outside of fault reactivation periods the sds is less active such as during the present situation

echo characters of the continental margin western bay of bengal india abstract an echo character study of about 35 000 km length of 3 5 khz echograms recorded from the continental shelf slope and rise domains in the western bay of bengal reveals twenty echo types based on their distribution the analysis of sediment cores and comparison with the similar echo types reported from atlantic continental margin the echoes are interpreted to reflect variation in sediments produced by different processes the distribution of various echo types are significantly different within each physiographic province shallow marine processes have influenced the continental shelf off non deltaic areas whereas fluvio deltaic processes dominate areas off deltas deposits formed by mass wasting dominate the continental slope off puri machilipatnam and off pondicherry where the sea floor is eroded and gullied by slides slumps and debris flows the deposits developed under the influence of combined processes are most widespread on the continental rise south of kakinada the rest of the continental rise the continental slope off nizampatnam bay and cauvery river and the bengal fan are influenced by turbidity currents the bengal fan is also affected by mass wasting

holocene paleoclimatic reconstruction based on mud deposits on the inner shelf of the east china sea abstract we present a paleoclimatic reconstruction of the mid holocene by geochemical analysis of a sediment core mz01 retrieved from the mud area of the inner continental shelf of the east china sea ecs our results show that the downcore geochemical variations in the sediments of the core provide a link to historical climate changes relatively higher ratios of cia ba sr and a lower ratio of cao mgo coincide with major regional warm and humid climate episodes and vice versa therefore these geochemical indicators are useful in reconstructing the paleoclimate in eastern china using the geochemical records of core mz01 which are well constrained by ams 14c dating we found that from 8300 yr bp to 4200 yr bp the regional climate was moderately warm and humid and from 4200 yr bp to 2300 yr bp the climate was cool and dry with large fluctuations between cool dry 3700 yr bp 2850 yr bp and 2400 yr bp and warm wet 3250 yr bp and 2650 yr bp since 2300 yr bp our records indicate that the climate has gradually become warmer although a cold event centered at around 250 yr bp the little ice age lia interrupted this warming trend we also found significant 238 yr cycles in our cia records that imply a possible solar influence on the regional climate changes since the mid holocene

the 2011 expedition to the el gygytgyn impact structure northeast russia toward a new geological map for the crater area el gygytgyn is a 3 6 ma 18 km diameter impact crater formed in an approximately 88 ma old volcanic target in northeast siberia the structure has been the subject of a recent icdp drilling project in parallel to those efforts a russian german expedition was undertaken in summer 2011 to investigate the permafrost soil lake terraces and the volcanic rocks of the southern and eastern crater rim this provided the unique opportunity for mapping and sampling of the volcanic target rocks around a large part of this complex impact structure samples from 43 outcrops were collected and analyzed petrographically and geochemically the results were combined with earlier mapping outcomes to create a new geological map of this impact structure and its immediate environs at the scale of 1 50 000 compositions of our rock suites are compared with the lithologies of the 2009 icdp drill core the ignimbrite described as lower bedrock in the icdp drill core shows petrographically and chemically strong similarities to the rhyolitic and rhyodacitic ignimbrites observed on surface the suevite sequence exposed in the icdp drill core is a mixture of all observed target rocks at their respective proportions in the area in contrast to previous studies the calculated average target composition of el gygytgyn takes the contribution of the basic target rocks into consideration mafic and intermediate rocks approximately 7 5 and felsic rocks approximately 92 5

evolution of late quaternary mud deposits and recent sediment budget in the southeastern yellow sea abstract analysis of high resolution seismic reflection profiles and sediment samples has revealed the evolution and sediment budget of the southeastern yellow sea mud belt seysm along the southwestern korean peninsula the seysm up to 50 m thick over 250 km long and 20 55 km wide can be divided into three stratigraphic units a1 a2 and b from oldest to youngest unit a1 overlying the acoustic basement comprises the northern part of the seysm unit a2 comprises the southern part of the seysm much of unit a2 is exposed at the seafloor unit b completely covers unit a1 and pinches out southward 14c data suggest that evolution of each unit is closely related to the postglacial sea level changes unit a1 consists of estuarine deltaic or shallow water muds deposited during the early to middle stage of postglacial sea level rise ca 14 000 7000 yr b p unit a2 corresponds to relict muds deposited during the last deceleration stage of sea level rise ca 7000 3 500 yr b p unit b consists of shelf muds deposited during the recent sea level highstand ca very low background activities of 210pb of the surface sediment of unit a2 suggest that the present day sediment accumulation is negligible in the southern seysm on the other hand 210pb excess activity profiles in unit b yield an average sediment accumulation rate of 3 9 mm yr indicating active sediment accumulation in the northern seysm the annual sink 3 0 10 7 tons yr of fine grained sediment in unit b is about an order of magnitude greater than can be explained by the sediment input from the korean rivers alone we propose that reworking of unit a2 has provided large volumes of muds to unit b resulting in excessive sediment accumulation in the northern seysm much of unit a2 in turn is likely to have originated from erosion of unit a1 in the north this rather unique erosional depositional regime of the seysm is probably owing to the tidal and regional currents characteristic in the southeastern yellow sea

development of stratigraphy and sediment distribution in the northeastern yellow sea during holocene sea level rise abstract a succession of holocene deposits in the northeastern yellow sea were interpreted in a sequence stratigraphic context and sedimentology of each deposit was characterized based on analyses of high resolution seismic profiles and sediment cores taken along a transect thin 3 m transgressive sediments that accumulated through shoreface erosion during the rapid sea level rise in the early holocene overlie a subaerially eroded low gradient late pleistocene platform on the present day inner shelf region cores reveal marine sands over tidal estuarine sandy muds with an intervening rather indistinct ravinement surface in the deepest shelf area these early holocene tidal estuarine deposits remain exposed at the seabottom in the mid o late holocene two contrasting deposits of the highstand type deltaic clayey mud and tidal sand ridges began to accumulate in response to slower rates of sea level rise a series of tidal sand ridges in the nearshore area migrated offshore over the transgressive sand sheet and a deltaic watery mud prograded discordantly over consolidated tidal estuarine deposits in the central shelf the transgressive facies relationships present a model for macrotidal epicontinental sea settings subject to low wave energy and reduced sediment supply

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

the northwest african slope apron a modern analogue for deep water systems with complex seafloor topography the northwest african slope apron is an interesting modern analogue for deep water systems with complex seafloor topography a sediment process map of the northwest african continental margin illustrates the relative roles of different sedimentary processes acting across the entire margin fine grained pelagic and hemipelagic sedimentation is dominant across a large area of the margin and is considered to result from background sedimentary processes alongslope bottom currents smooth and mould the seafloor sediments and produce bedforms such as erosional furrows sediment waves and contourite drifts downslope gravity flows debris avalanches debris flows and turbidity currents are infrequent but important events on the margin and are the dominant processes shaping the morphology of the slope and rise the overall distribution of sedimentary facies and morphological elements on the northwest african margin is characteristic of a fine grained clastic slope apron however the presence of numerous volcanic islands and seamounts along the margin leads to a more complex distribution of sedimentary facies than is accounted for by slope apron models in particular the distribution and thickness of turbidite sands are controlled by the location of the break of slope which is itself controlled by the pre existing submarine topography

development of depositional systems in the southeastern yellow sea during the postglacial transgression this study focuses on the development of depositional systems in the southeastern yellow sea during the postglacial transgression based on the analysis of closely spaced high resolution seismic profiles chirp and piston cores transgressive deposits comprise the paralic component of estuarine channel fills seaward prograding wedge and along shore prograding mound and the marine component of sand veneer mud blanket and offshore ridge these transgressive deposits were developed through three distinctive stages in terms of possible sea level position during the early stage tidal sand ridges and sand veneer formed south of jeju island resulting from shoreface erosion associated with a relatively slow transgression the following transgression in the middle stage inundated subaerially formed interfluves along the central part of the sea and affected development of estuarine environments with increasing tidal regime in the eastern part of the sea combined with the strong tidal reworking insufficient sand supply enhanced the formation of erosional ridges short period increase in fluvial discharge affected the deposition of coastal wedge in the western part fine grained sediments from either fluvial discharge or tidal reworking were dispersed seaward to form mud blanket the late stage was characterized by the deposition of veneered sands off the jiangsu coast which was due to relatively slow rise in sea level further offshore along shore prograding mound was constructed by huanghe derived sediment influx and subsequently eroded and redeposited by wave and tide activities thus detached from the proximal source the depositional processes and variability of the transgressive deposits in the southeastern yellow sea were largely controlled by changes in rate of sea level rise during the transgression most likely related to the global flooding events triggered by melt water pulses the changes in shoreline configuration and oceanographic regime have also influenced the distribution and morphology of the transgressive deposits a short period increase in riverine discharge caused the temporal sediment progradation off the jiangsu coast

zoned facies of mass flow deposits in the ulleung tsushima basin east sea sea of japan abstract high resolution 3 5 khz reflection profiles in the ulleung tsushima basin made it possible to classify the uppermost ca 50 m thick sedimentary deposits into rock fall slide slump debris flow deposit debrite and turbidite in terms of their acoustic properties these deposits generally occur in a distinctive zonal facies slides and slumps on the slope debrites on the base of slope and turbidites on the basin floor the rock fall deposits occur along the bases of the korea plateau and ulleung and dok islands the zonal distribution of mass flow deposits suggests that they most likely are derived from a line source at the shelfbreak shelf sediments prograde toward the shelfbreak on the slope sediment masses move downslope mainly accompanied by progressive slumping upslope individual slides and slumps on the slope probably develop into debris flows on the base of slope and successively into turbidity currents on the basin floor mass flow processes on the ulleung basin slope played an important role in transporting a large volume of terrigenous sediments into the deep basin

strata sequence and paleochannel response to tectonic sea level and asian monsoon variability since the late pleistocene in the south yellow sea

holocene paleoenvironmental changes in mud area southwest off cheju island east china sea evidence from benthic foraminiferal assemblages and stable isotope records abstract a sediment core retrieved from the mud area southwest off cheju island masci was analysed for benthic foraminifera grain size and stable isotopes and constrained by ams14c dating holocene paleoenvironmental changes in this broad shallow shelf were investigated with special focus on the evolution of the masci and its related ocean eddy system the results indicate that the east china sea shelf has undergone four major environmental evolution stages during the holocene prior to 9 8 cal kyr bp the benthic foraminiferal assemblages were dominated by low salinity shallow water species ammonia beccarii linnaeus elphidium advenum cushman and cribrononion subincertum asano reflecting a near coast deposit environment a noticeable transition of the benthic foraminifera from an a beccarii dominated to ammonia compressiuscula brady dominated assemblage taking place at approximately 9 8 cal kyr bp together with a contemporaneous increase in 18o and 13c provides evidence that a rapid rise in sea level occurred at this time in the east china shelf a gradual increase in 18o between 9 8 and 6 cal kyr bp indicates a steady strengthening influence of open ocean water on the area under study a sudden increase in the abundance of benthic foraminifera along with a decrease in the coarse fraction imply that an early eddy circulation system was established since almost 6 cal kyr bp in the masci this eddy circulation system was quite weak but gradually strengthened between 6 and 3 cal kyr bp possibly due to the intrusion of the yellow sea warm current yswc a more stable mud deposition period characterised by a high sedimentation rate of fine grained sediment and lighter value of 13c starting at approximately 3 cal kyr bp indicates that the masci was formed mainly during the late holocene we believe that the strengthened yswc since 3 cal kyr bp might increase the trap efficiency of the eddy system thereby accounting for the high sedimentation rate of mud deposits during this period

origin and dispersal of recent clay minerals in the yellow sea abstract the clay minerals in the by considering the clay minerals supplied by rivers in china the old and present day huanghe river and korea the keum and yeongsan to the yellow sea continental shelf and the spatial variation in the distribution of clay minerals in the yellow sea this study indicates that the provenance of the cysm may be closely related to the old and present day huanghe river system whereas the clay minerals in the seysm seem to be largely associated with the keum and yeongsan rivers in addition smectite may be suggested as an important clay mineral in differentiating between cysm and seysm and understanding the sources of these two mud categories

el gygytgyn impact crater chukotka arctic russia impact cratering aspects of the 2009 icdp drilling project the el gygytgyn impact structure in chukutka arctic russia is the only impact crater currently known on earth that was formed in mostly acid volcanic rocks mainly of rhyolitic with some andesitic and dacitic compositions in addition because of its depth it has provided an excellent sediment trap that records paleoclimatic information for the 3 6 myr since its formation for these two main reasons because of the importance for impact and paleoclimate research el gygytgyn was the subject of an international continental scientific drilling program icdp drilling project in 2009 during this project which due to its logistical and financial challenges took almost a decade to come to fruition a total of 642 3 m of drill core was recovered at two sites from four holes the obtained material included sedimentary and impactite rocks in terms of impactites which were recovered from 316 08 to 517 30 m depth below lake bottom mblb three main parts of that core segment were identified from 316 to 390 mblb polymict lithic impact breccia mostly suevite with volcanic and impact melt clasts that locally contain shocked minerals in a fine grained clastic matrix from 385 to 423 mblb a brecciated sequence of volcanic rocks including both felsic and mafic basalt members and from 423 to 517 mblb a greenish rhyodacitic ignimbrite mostly monomict breccia the uppermost impactite 316 328 mblb contains lacustrine sediment mixed with impact affected components over the whole length of the impactite core the abundance of shock features decreases rapidly from the top to the bottom of the studied core section the distinction between original volcanic melt fragments and those that formed later as the result of the impact event posed major problems in the study of these rocks the sequence that contains fairly unambiguous evidence of impact melt which is not very abundant anyway usually less than a few volume is only about 75 m thick the reason for this rather thin fallback impactite sequence may be the location of the drill core on an elevated part of the central uplift a general lack of large coherent melt bodies is evident similar to that found at the similarly sized bosumtwi impact crater in ghana that however was formed in a target composed of a thin layer of sediment above crystalline rocks

origin of inner shelf mud deposit in the southeastern yellow sea huksan mud belt abstract a variety of previous sedimentological results together with newly obtained hydrodynamic data are summarized and reinterpreted with respect to the most likely origin of the huksan mud belt hmb in the southeastern yellow sea the hmb consists of two mud units that have similar grain texture and clay mineralogy but can be differentiated on seismic profiles because the lower unit is generally harder than the watery upper unit the hydrographic measurements together with satellite imagery clearly indicate that the suspended plume covering the hmb originates from the west coast of korea the suspended plume becomes enhanced by winter monsoon winds beginning in late fall most of the studies of clay mineralogy geochemistry and isotherm distribution also suggest that the hmb has been derived from the west coast of korea particularly from the keum river an approximate evaluation of the depositional time for the hmb based on its dimensions and the discharge rate of the keum river suggests a time duration of the order of 14 000 years hydrodynamic measurements across two transects over the northernmost hmb reveal that suspended matter travels southwest toward the main body of the hmb in a well constrained corridor ultimately connected with the keum river time series 12 5 h hydrodynamic measurements at a site over the hmb suggest that the winter season suspended plume carries concentrations of suspended matter one to two orders of magnitude higher than those of the summer silt grains of 5 6 well sorted through numerous resuspension events settle out onto the hmb forming distinctive silt laminae alternating with clay rich laminae

anomalous depressions in the northern yellow sea basin evidences for their evolution processes abstract depressions of both known and unknown origin are observed in continental margin basins and ocean floors worldwide a field of anomalous depressions with dome structures within the centers are documented for the first time using sub bottom seismic profiles multibeam bathymetry data and well data in the northern yellow sea basin they have complex seabed morphologies circular elliptical polygonal linear and crescent shapes with kilometer scale diameters and shallow depths 10 s decimeters to meters focused fluid flow pathways such as gas chimneys faults and pipes and free gas enhanced amplitude anomalies are observed within the shallow strata the depressions are interpreted as immature pockmarks possibly caused by insufficient fluid supply compared to fully developed normal pockmarks they are suspected to still be in the middle stage of pockmark evolution their formation processes are suspected to be controlled by sub seabed plumbing fluid flux and bottom currents this study is important for geologic hazard assessments in the study area and it also contributes to the full understanding of pockmark evolution

sedimentary system response to the global sea level change in the east china seas since the last glacial maximum abstract the east china seas ecs is one of the world s largest continental shelf seas based on the combination of global sea level change and sequence stratigraphy we systematically investigated the evolution of sedimentary system in the ecs since the last glacial maximum lgm we have defined the transgressive boundary layer and constructed several sedimentary models of the ecs on the sequence stratigraphy and evolution of tidal sand ridges since the lgm and sediment source to sink during the high sea level the result shows that the ecs represent a typical case for large scale continental shelf response to the global sea level change three sedimentary system tracts had been formed in the ecs since the lgm first is the lowstand system tract corresponding to the late of last glaciation and lgm 23 15 4 cal kyr b p the progressive wedge occurred along the okinawa trough slope and the paleo coastal zone pcz along the continental shelf edge second is the transgressive system tract corresponding to the last deglaciation 15 4 7 cal kyr b p a large scale transgressive boundary layer and tidal sand ridges were formed in this stage third is the highstand system tract corresponding to the high sea level since 7 cal kyr b p the eddy mud coastal current mud present tidal sand ridge delta tidal flat and beach have been accumulating since then the global sea level change after lgm can be divided into seven phases of which four rapidly rising phases rrp i ii iii iv and three slowly rising phases srp i ii iii are distinguished the tidal sand ridges were formed in the srp and transgressive boundary layer in the rrp the tidal sand ridges can be divided into three types including radicalized channel and emanative the modern circulation current system of the ecs had been built in the end of the last deglaciation the effect of sediment source to sink in the ecs is closely correlative to the current system driven by the interaction of the east asian monsoon and kuroshio the major sediment source is from the river discharge of the huanghe and changjiang river and coastal resuspension the muddy sediment in the eddy and coastal current which cover the tidal sand ridges and transgressive boundary layer is a major sediment sink in the modern ecs

shocked rocks and impact glasses from the el gygytgyn impact structure russia the elgygytgyn impact structure is about 18 km in diameter and is located in the central part of chukotka arctic russia the crater was formed in volcanic rock strata of cretaceous age which include lava and tuffs of rhyolites dacites and andesites a mid pliocene age of the crater was previously determined by fission track 3 45 0 15 ma and 40ar 39ar dating 3 58 0 04 ma the ejecta layer around the crater is completely eroded shock metamorphosed volcanic rocks impact melt rocks and bomb shaped impact glasses occur in lacustrine terraces but have been redeposited after the impact event clasts of volcanic rocks which range in composition from rhyolite to dacite represent all stages of shock metamorphism including selective melting and formation of homogeneous impact melt four stages of shocked volcanic rocks were identified stage i 35 gpa lava and tuff contain weakly to strongly shocked quartz and feldspar clasts with abundant pfs and pdfs coesite and stishovite occur as well stage ii 35 45 gpa quartz and feldspar are converted to diaplectic glass coesite but no stishovite stage iii 45 55 gpa partly melted volcanic rocks common diaplectic quartz glass feldspar is melted and stage iv 55 gpa melt rocks and glasses two main types of impact melt rocks occur in the crater 1 impact melt rocks and impact melt breccias containing abundant fragments of shocked volcanic rocks that were probably derived from now eroded impact melt flows on the crater walls and 2 aerodynamically shaped impact melt glass bombs composed of homogeneous glass the composition of the glasses is almost identical to that of rhyolites from the uppermost part of the target cobalt ni and ir abundances in the impact glasses and melt rocks are not or only slightly enriched compared to the volcanic target rocks only the cr abundances show a distinct enrichment which points toward an achondritic projectile however the present data do not allow one to unambiguously identify a meteoritic component in the elgygytgyn impact melt rocks

acoustical facies analysis at the ba lat delta front red river delta north vietnam abstract a shallow penetrating high resolution acoustic study was performed in the ba lat delta the major distributary of the red river system in northern vietnam an acoustic facies map was constructed and the various facies types were validated through analysis of bottom sediments by a study of gravity cores collected at 22 stations analysis of the acoustic profiles and gravity cores revealed the presence of an asymmetrical s to sw prograding prodelta lobe in accordance with the prevailing longshore currents to the s the southern part of this prodelta is detached from the protruding ba lat delta front the prodelta is dominated by muddy sediments with minor thin