sediment provenance and paleoenvironmental change in the ulleung basin of the east japan sea during the last 21 kyr despite the well reconstructed paleoceanography of the late quaternary deposits in the east japan sea es provenances of terrigenous sediments and a comprehensive interpretation of their variations since the last glacial maximum remain unclear especially in regard to the mainland china and taiwan derived matter grain size conservative trace elements rare earth elements rees nd isotope and clay mineralogy of core sediments from the ulleung basin of the es were investigated for better understanding of detrital sediment provenance and transport process and then their forcing mechanisms over the last 21 kyr geochemical mineralogical multi indices in this study showed notable three phase changes in sediment provenance which can be closely related to sea level fluctuation development of the tsushima warm current as well as intermittent influence from the east asian summer monsoon climate evolution during unit 1 21 1 8 4 kyr bp when the tsushima warm current was absent in the es the paleo changjiang and the paleo huanghe mouth might be situated close to the study area and thus mainland china could have played major role in the southwestern ulleung basin sedimentation in particular the formation of rhythmic dark colored alternation in unit 1 is possibly attributable to the pulse of paleo huanghe discharge associated with centurial to millennial scale variability in the east asian summer monsoon in unit 2 8 4 7 2 kyr bp these river mouths gradually retreated to their present positions with global sea level rise leading to decreasing terrigenous sediment supply from mainland china to the study area since 7 2 kyr bp unit 3 sedimentation in the ulleung basin should still be mainly derived from mainland china meanwhile increasing chlorite kaolinite ratio but decreasing epsilon nd value revealed that terrigenous matter from taiwan might have been limitedly transported northward to the study area by the fully evolved tsushima warm current a prominent decline in chlorite kaolinite ratio together with contrast change on epsilon nd value centered at around 2 9 kyr bp 3 3 2 4 kyr bp may have been caused by the tsushima warm current suppression possibly related to the pulleniatina minimum event popularly found in the study area and nearby seas c 2014 elsevier ltd all rights reserved

geochemistry of surface sediments in the southwestern east japan sea abstract we analyzed 77 surface sediment samples collected in the southwestern east japan sea from the korea strait through the ulleung basin and the korea plateau for grain size calcium carbonate organic carbon and major na mg al fe k ca and ti and trace elements p mn sr li sc v cr co ni zn cu and pb the chemical composition of the surface sediments was found to be highly variable spatially cluster analysis of surface sediment chemical compositions indicated five major geochemical sedimentary environments basin lower slope coast and upper slope inner shelf and outer shelf continental shelf sediments were rich in shell fragments and had relict and coarse grained characteristics recent fine grained sediments were only distributed in coastal slope and basin areas concentrations of al k ca ti cr and sc were highest in the coastal and upper slope areas and decreased with water depth elemental ratios using major and trace elements indicated that coastal and upper slope detrital sediments were mixtures of sediments derived from the changjiang yangtze and nakdong rivers although the concentrations of organic carbon p mn v co ni cu and pb increased with water depth their distribution patterns indicated authigenic v cu and pb and diagenetic fe p mn co and ni origins the distribution pattern with water depth suggested that the chemical composition of surface sediment was determined by sedimentologic and geochemical processes such as the supply of detrital and biogenic materials and authigenic and post depositional diagenetic processes in sediments

metal accumulation rates in northwest atlantic pelagic sediments measurements of 230th 87sr86sr and twenty four metals were made on cores from the nares abyssal plain the sediment is characterized by slowly accumulating 0 3 0 7 g cm2 103 yr pelagic red clays and rapidly deposited grey clays transported by turbidity currents despite their colour differences and the enrichment of mn fe cu co ni zn v and to a lesser degree the rare earths in the red clays sr isotope evidence demonstrates that the clays have the same terrigenous origin the excesses of metals in the red clays have been attributed to metal removal from the water column and a comparison with the grey clays has enabled the authigenic fluxes of metals to be estimated the fluxes obtained are in the ranges 20 50 mol cm2 103 yr for mn and fe 0 1 0 4 mol cm2 103 yr for cu co ni zn v sr and ce 10 20 nmol cm2 103 yr for la and nd and 0 5 3 nmol cm2 103 yr for sm eu gd dy er and yb authigenic fluxes of y nb cr zr rb u and th were not resolvable fluxes appear to be near constant on the plain but comparison with other areas shows that they are quite variable both between and within ocean basins the chief factor controlling authigenic fluxes is the geochemical abundances of the elements but fractionation within both the transition element and rare earth series can be recognized from inter element comparisons and from differences in fluxes between atlantic and pacific red clays corresponding to the oceanic reactivities of the elements

vertical distribution of various elements in sediment cores from the japan sea abstract deep sea sediment cores ranging up to 30 000 80 000 yrs in age were taken from a southern region of the japan sea and subjected to analyses for 5 major and 11 trace elements by means of instrumental photon activation analysis with 30 mev bremsstrahlung these elements were ca fe mg na ti ba ce co cr mn nb ni rb sr y and zr additionally al was determined spectrophotometrically distribution patterns of these elements with depth in the sediment columns were derived enrichments of ca and sr by biogenous process were observed these ca maxima are well correlated with mn maxima below the holocene pleistocene boundary continuous transportation of poorly degraded continental debris which was low in metallic constituents was noted a distinct enrichment of the top layer of the sediments in mn was observed this is the result of post depositional upward migration of mn fe co and ni were also enriched in the top layers in the central part of the basin the oxidized post glacial zone appears to be a typical pelagic sediment

reconstruction of environmental changes using a multi proxy approach in the ulleung basin sea of japan over the last 48 ka based on elemental geochemical data we reconstructed the sediment provenance surface productivity and bottom water redox conditions for the last 48 ka in the ulleung basin sea of japan and inferred the factors controlling them al2o3 tio2 ratio and chemical index of alteration cia suggest that sediment provenance changed during the glacial period 48 18 ka compared to the deglacial ca 18 11 ka and holocene mass accumulation rates of total organic carbon toc caco3 phosphorus cadmium and excess barium reveal low paleoproductivity during low sea stand during 18 11 ka productivity increased due to increasing inflow of nutrient rich water masses the oyashio and the east china sea coastal water in tandem with the rising sea level maximum productivity occurred during younger dryas and pre boreal periods when sea level was at 60 m and then gradually decreased as the tsushima warm current inflow kicked off at ca 9 3 ka consistent with other paleoredox proxies which reveal the presence of anoxic bottom water during ca 12 9 ka with the changes in paleoredox proxies and their ratios toc mo u mn c s ratio and uauthigenic and mo contents we hypothesized that the redox changes were mainly ventilation driven and were superimposed on the influence of circulation induced productivity changes the global climate and sea level changes on a millennial timescale play a major role in enhancing paleoproductivity and restrict bottom water advection subsequently driving the oxygenation of bottom water in the ulleung basin copyright 2012 john wiley sons ltd

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

pleistocene evolution of the red sea coastal plain egypt evidence from uranium series dating of emerged reef terraces abstract eight emerged reef terraces i viii belonging to three cycles of reef formation were recognized along the red sea coastal plain of egypt the oldest cycle is represented by terrace viii at altitude varying between 9 and 35 m the middle cycle is represented by terraces vii v whose altitudes vary between 22 and 32 m while the youngest one is represented by terraces iv i at altitudes of 9 6 3 and 2 m respectively the three lowermost terraces i iii of the youngest cycle give 230 th 234 u ages between 72 1 2 5 and 131 2 4 4 ka bp which are distributed in three ranges 72 1 2 5 87 6 2 2 112 1 3 3 113 2 4 1 and 123 6 4 7 131 2 4 4 ka bp these age ranges coincide with the chronology of the last interglacial cycle but their correlation with the oxygen isotope substages 5a 5c and 5e respectively is not evident this suggests that the three dated terraces combined with terrace iv were built during the maximum high sea level stand of the last interglacial cycle oxygen isotope substage 5e while their surfaces are the product of short still stands during a continuously falling sea level however the comparison of the stratigraphic relations of the older terraces made up of recrystallized corals with both the oxygen isotope record and the curve for solar insolation received by the earth at latitude 65 n allowed the estimation of their minimum ages the terraces of the middle cycle were considered to have formed during oxygen isotope stage 7 170 230 ka bp while that of the oldest cycle was formed during stage 9 300 330 ka bp the present day altitudes of these terraces are the product of eustatic sea level fluctuations and differential tectonic uplift

comparisons between observations and numerical simulations of japan east sea flow and mass fields in 1999 through 2001 abstract the princeton ocean model pom as implemented for the japan east sea jes with mesoscale admitting resolution is driven by seasonal throughflow and synoptic atmospheric forcing for 1999 through 2001 temperature and salinity profiles from shipborne and palace float ctds and horizontal velocities at 800 m from palace float trajectories plus horizontal velocities at 15 m from woce surface drifters for 1988 through 2001 are used to assess the performance of the numerical simulations for a base case general agreement exists in the circulation at 15 and 800 m and the horizontal and vertical structure of the upper ocean temperature and salinity fields the mean observed flow at 15 m defines the two branches of the tsushima warm current and hints at the existence of a large cyclonic gyre over the japan basin which the simulations also produce the mean observed flow at 800 m defines a large cyclonic recirculation gyre over the japan basin that validates the simulated flow pattern variances of the observed and simulated flows at 15 and 800 m have similar patterns the main discrepancies are associated with the strength of the seasonal thermocline and halocline and the location of the subpolar front when smoother topography and smaller lateral friction are used in other cases the thermocline and halocline strengthen agreeing better with the observed values and when 80 of total outflow transport is forced to exit through soya strait the subpolar front extends along the coast to the north of tsugaru strait which is an observed feature absent in the base case

zabargad st john s island an uplifted fragment of sub red sea lithosphere zabargad is a small island located in the red sea about 50 km w of its axis between 23o and 24on the island is not volcanic but probably represents an uplifted block of upper mantle and crustal rocks and yields information on the nature of the underlying lithosphere peridotites are the main rock type consisting of exceptionally fresh spinel lherzolites which equilibrated last at a depth 30 km in the mantle other ultramafic facies some representing rocks which mixed with a basaltic melt fraction and some which underwent metasomatic exchange at depth are also present the peridotite bodies are in tectonic contact with a metamorphic formation consisting of gneissic and amphibolitic rocks similar to those outcropping in the pan african metamorphic basement of eastern egypt peridotites and metamorphic rocks are both crossed by several generations of basaltic dykes the sedimentary zabargad formation of probable cretaceous or palaeocene age consists of alternations of silicified limestones sandstones black shales and phosphoritic lenses and is overlain by evaporites probably of miocene age and by reef limestone units one probably of early pleistocene age the other probably deposited during the last interglacial various formations are affected by localized metasomatic mineralizations recrystallized large gem quality olivine cancrinite scapolite garnierite the uplift of upper mantle ultramafic bodies with fragments of crust which created the island might have occurred in connection with the early stages of development of the rift which preceded the formation of the red sea an alternative explanation that the zabargad peridotites are remnants of a pan african palaeozoic ophiolitic complex is possible but less likely

grain size and geochemistry of surface sediments in northwestern continental shelf of the south china sea eighty six surface sediments collected from the northwestern continental shelf of the south china sea scs were analyzed for grain size distribution calcium carbonate organic carbon and major and trace element compositions to investigate sediment provenance and factors controlling their geochemical composition sediments from the eastern continental shelf of hainan island have higher sand and lower clay content while the samples from the nearshore hainan island have higher contents of gravel and clay calcium carbonate contents in samples show a positive correlation with water depth in northwestern shelf of scs suggesting that it is related to biological factors however the nearshore sediments have higher contents of organic carbon compared to those of the outer shelf possibly suggesting that the terrigenous organic matter usually deposited in nearshore environments such as bays and estuaries compared with the upper continental crust the samples have relatively lower contents of sio2 and al2o3 higher than those of the pearl and red river sediments the low contents of k2o and na2o in sediments from the northwestern continental shelf are consistent with intense chemical weathering in the river basin due to the seasonally hot and humid climate regime the sediments mainly consist of three components including the gravel fraction composed of calcareous debris the sand fraction composed of quartz and the silt and clay fractions mainly composed of clay minerals the content of each component depends on grain size sediment source biogenesis and hydrodynamic conditions which finally controls the chemical composition of the sediments the distributions of co al2o3 cr al2o3 and zr sc ratios for sediments in the northwestern continental shelf suggest that source rocks are mainly composed of felsic rocks rather than mafic rocks there is a distinct difference in sediment source between eastern and western shelf sediments the eastern shelf sediments are characterized by high zr sc ratios mainly derived from the pearl river while the western shelf sediments have relatively low values of zr sc indicating a main contribution possibly sourced from the red river basin terrigenous materials from hainan island usually influence the geochemistry of sediments deposited in the nearshore area

particulate element inventory of the huanghe yellow river a large high turbidity river abstract suspended sediments from the river mouth to the upper portions of the huanghe yellow river were collected and analysed to determine their chemical composition comparison with other large world rivers indicates that trace element levels are relatively low in this high turbidity river natural weathering and erosion are of primary importance in controlling particulate element concentrations although the impact from anthropogenic activities is also visible finally input of particulate elements to the china sea is assessed from the river sediment load and compositions

slope stability change from late pleistocene to holocene in the ulleung basin east sea japan sea abstract a wide variety of mass movement deposits prevail along the entire margin of ulleung basin overlain by a hemipelagic mud unit 1 2 m thick the boundary between the lower turbidite sequence and the upper hemipelagic mud on the basin plain is distinct and approximately coincides with the well known basin wide ash layer ulleung ash of early holocene age in the absence of significant terrigenous sediment input the lithologic change from the turbidite to hemipelagic mud may reflect physical effects of glacio marine eustatic sea level change sea level lowering during the glacial period may have generated excess pore pressure within the sediments caused by reducing hydrostatic confining pressure and facilitated triggering of the deep water slope failure by earthquakes storm waves may also have affected the uppermost slope area to induce small scale slope instabilities during the lowered sea level stand these glacial factors destabilizing the slope appear to have enhanced large scale slope failures during the late pleistocene in contrast the topmost hemipelagic mud attests to a stable slope phase associated with raised sea level in the holocene consistent with the infinite slope stability analyses calculations of the sedimentation rates based on c 14 dates of several ash layers indicate that the pre holocene turbidites on the basin plain had accumulated at an average rate of 40 cm 1000 years with a minimum recurrence interval of 50 years during the late pleistocene mass flux estimations between the slumps and turbidites suggest a predominance of the nondisintegrative mode of slope failures in the ulleung basin in each event of slope failure most of the failed mass rested on the slope as slide slump blocks and only its meager portions were deposited on the basin plain as turbidite layers

paleoenvironmental changes in the east japan sea during the last 48 ka indications from high resolution x ray fluorescence core scanning paleoceanographic changes in the east japan sea during the late quaternary based on high resolution elemental variations particularly correlations between dark light laminations and millennial scale climatic changes have remained poorly understood because of the lack of the high resolution proxies the recent application of micro x ray fluorescence xrf core scanning provides the potential for high resolution study on the laminations deposited in the east japan sea in this study we present a geochemical study by using micro xrf core scanning on a 730 cm core recovered from the east japan sea elemental variations and factor analysis indicate that the sedimentary environment changed from anoxic to suboxic conditions from marine isotope stage mis 2 3 to mis 1 which is induced by increased contribution of high salinity sea water from the open ocean due to the rising sea level the dark and light laminations during mis 2 3 were correlated with dansgaard oeschger cycles and summer monsoon proxy with dark colored sediments related to higher terrigenous concentration corresponding to warm moist and enhanced summer monsoon period during the interstadial period more terrigenous sediments were transported to the east japan sea via the strengthened fluvial discharge from the surrounding continents caused by enhanced monsoon rainfall thus the development of the east asian summer monsoon and consequent variations in fluvial discharge would have significantly affected the paleoceanographic conditions in the east japan sea during the mis 2 3 sea level lowstand copyright 2012 john wiley sons ltd

geochemical characteristics of the recent sediments from the sea of marmara abstract six box cores one boomerang core and one hundred sixty six surface sediment samples recovered in the sea of marmara were analyzed in an attempt to establish the main controls on distribution and origin of trace metals within the oxic to suboxic basin of this sea surface and downcore data indicate that the abundance and distribution of the total metal concentrations for fe ni zn cr co cu and pb can largely be explained by the variable admixtures of terrigenous components in response to textural variations and biogenic calcareous components poor in metal contents the distribution of cr and ni seems to be controlled in part by a contribution from the weathering of basic ultrabasic sources on the coastal hinterland a small but significant amount of cu zn and pb in sediments from the northeastern sea of marmara probably suggests a pollution effect from the northerly located golden horn estuary that is known as one of the most polluted coastal regions of turkey looking at the data it seems that the mn concentrations are unusually high in the deep water sediments 4498 9127 ppm carbonate free along the east west trending marmara trough but low in sediments from the adjacent shallow waters 307 2059 ppm carbonate free the mn enrichment in deep water relative to shallow water marmara sediments is further indicated by the fe mn ratios being on average 11 23 in deep waters and 34 69 in shallow waters the contents of other metals fe ni zn cr co cu pb in both shallow and deep water sediments fall nearly within the same range as those found in average crustal and sedimentary rocks suggesting no significant enrichment of these metals in the deep marmara basins the downcore changes in the color from reddish brown at the surface top 2 5 cm to greenish gray in the subsurface 5 cm together with the occurrence of high mn concentrations in the surface sediment layers in cores can be attributed at least in part to the diagenetic mn enrichment within the sediment column the usually low organic carbon contents and biogenic components present in sediments reflect that the well known biogenic mechanism for the enrichment of mn seems to be of minor importance in the deep marmara waters the generally low mn concentrations contained in the surface grab and core sediments from the black sea and aegean sea approaching those of the sea of marmara do not provide any conclusion to support significant mn contribution from these two adjacent seas particularly from the so called manganese pump zones in the shallow black sea waters comparison with other deep sea sediments which have been deposited under the influences of hydrothermal activities worldwide suggests mn enrichment in deep water relative to shallow water sediments of the sea of marmara mainly as a result of hydrothermal contributions from this seismically active marine region based on the average fe mn ratios obtained in cores which tend to increase gradually from 11 in the deep central basin to 67 69 in the northeastern and southwestern shelves the central basin of marmara trough can be considered as a possible potential source for hydrothermal solutions leading to the enrichment of mn in the deep marmara waters however this remains to be further investigated

the role of fracture zones during early red sea rifting structural analysis using space shuttle radar and landsat imagery the structural pattern of the red sea region an area where continental lithosphere is cut by a young oceanic rift was studied by means of satellite and space shuttle radar imagery the space shuttle mission 2 made two passes over the red sea bracketing a region transitional between the southern red sea where true seafloor spreading started about 5 ma bp and the northern red sea where crust is probably continental though thinned and stretched structures on these passes define bands of shearing in the african and arabian margins parallel to the dead sea fracture zone 000 020 combinations of these data with landsat information reveal four shear bands along the margins of the red sea and one oblique to the gulf of suez we have named the northern three red sea shear zones detected on the sir a data the brothers dead sea fracture zone the zabargad fracture zone and the shagara fracture zone two sets of normal faults were also detected trending 330 340 parallel to the northern red sea coastline and 310 320 parallel to the axial deeps in the red sea a map of the 310 320 faults bordering the red sea resembles a v shaped wedge narrowing to the north near the gulf of suez these faults may have formed as a result of the most recent push of seafloor spreading if this is so then there may be a propagating tectonic wedge moving from south to north which thins the continental crust up to distances of 300 km from the axis of spreading following continental deformation oceanic crust may be emplaced in 9hot points9 along the rift axis these 9punctiform9 oceanic spreading centres should propagate in the same direction as continental rifting during this episode palaeo shear zones probably act as barriers 9locked zones9 to the axial propagation one such case is at the zabargad fracture zone where the oblique impact of the propagating rift against the palaeo shear may have placed the red sea9s western side under compression and uplift while the eastern side may have been subject to oblique extension with the formation of pull apart basins the space shuttle imagery allows integration of some of the northern red sea morphotectonic features with structures on the continent

geochemistry of large river suspended sediments silicate weathering or recycling tracer this study focuses on the major and trace element composition of suspended sediments transported by the world s largest rivers its main purpose is to answer the following question is the degree of weathering of modern river borne particles consistent with the estimated river dissolved loads derived from silicate weathering in agreement with the well known mobility of elements during weathering of continental rocks we confirm that river sediments are systematically depleted in na k ba with respect to the upper continental crust for each of these mobile elements a systematics of weathering indexes of river borne solids is attempted a global consistency is found between all these indexes important variations in weathering intensities exist a clear dependence of weathering intensities with climate is observed for the rivers draining mostly lowlands however no global correlation exists between weathering intensities and climatic or relief parameters because the trend observed for lowlands is obscured by rivers draining orogenic zones an inverse correlation between weathering intensities and suspended sediment concentrations is observed showing that the regions having the highest rates of physical denudation produce the least weathered sediments finally chemical and physical weathering are compared through the use of a simple steady state model we show that the weathering intensities of large river suspended sediments can only be reconciled with the silicate derived dissolved load of rivers by admitting that most of the continental rocks submitted to weathering in large river basins have already suffered previous weathering cycles a simple graphical method is proposed for calculating the proportion of sedimentary recycling in large river basins finally even if orogenic zones produce weakly weathered sediments we emphasize the fact that silicate chemical weathering rates and hence co2 consumption rates by silicate weathering are greatly enhanced in mountains simply because the sediment yields in orogenic drainage basins are higher hence the parameters that control chemical weathering rates would be those that control physical denudation rates

st john s island red sea a new geophysical model and its implications for the emplacement of ultramafic rocks in fracture zones and at continental margins abstract new gravity and magnetic data from the northern red sea reveal the extent of the large gravity anomaly 164 mgal and the presence of significant magnetic anomalies over st john s island spectral transformation and three dimensional potential field modelling delineate the surface configuration and vertical extent of the causative body and the enormous density contrast required 1 2 g cm 3 suggests that it is composed of unserpentinised peridotite density 3 4 g cm 3 to a depth of at least 8 km st john s island is uniquely located not only at a passive continental margin but also within a fracture zone at the transition from plate separation by seafloor spreading to extension by lithospheric attenuation this precludes several suggested mechanisms for the emplacement of ultramafic bodies in fracture zones thermal contraction serpentinite diapirism and changes in the poles of rotation do not seem possible mechanisms in this tectonic environment and the emplacement is most probably related to the spreading readjustment necessary to create a continent to continent fracture zone a post mesozoic age of emplacement associated with the onset of continental rifting and the rejuvenation of a pre existing continental fracture seems most probable

basaltic dykes from zabargad island red sea petrology and geochemistry abstract basaltic doleritic dykes ranging in composition from picritic to alkali basalts are found on the island of zabargad an uplifted sliver of sub red sea lithosphere the dykes were injected into mantle derived peridotite bodies and into a metagabbro gneiss unit of lower crustal origin most dykes are made of phenocrysts of zoned plagioclase from bytownite in the core to andesine in the rim and of ca rich augite in a groundmass of salite amphibole plagioclase fe ti oxides and scarce olivine clinopyroxenes are partly replaced by amphiboles ranging from ferroan pargasite to edenite and to mg hornblende in some samples marialitic scapolite developed generally at the expenses of plagioclase during seawater interaction the seawater interaction process strongly influences the cs na ratio however samples with ln cs na greater or equal to 13 75 appear relatively unaffected by seawater open system exchanges chondrite normalized rare earth elements ree abundances show flat or slightly light ree enriched patterns intermediate between afar type volcanites and morb major elements compositions and ree abundances of unaltered rocks are compatible with the hypothesis that the zabargad dykes are produced by partial melting of peridotitic materials transition elements show depletion in ni and cr relative to primitive mantle abundances as a consequence of some fractionation the abundance of elements preferentially stabilized in the liquid phase hygromagmatophiles of treuil et al 1979 in most samples is consistent with a genesis for these magmas by partial melting in a distensive area followed by fractional crystallization sr and nd isotopic compositions of unaltered samples range between 0 70328 0 70438 and 0 51292 0 51305 respectively while altered samples have significantly higher 87 sr 86 sr up to 0 7064 trace elements and isotopic data are consistent with a chemically heterogeneous mantle source involved in the genesis of zabargad dykes which represent basaltic injections related to various stages of rifting preceding the emplacement of oceanic crust and the initiation of seafloor spreading

revisiting the origin of organic matter and depositional environment of sediment in the central ulleung basin east sea since the late quaternary abstract by analyzing sedimentary geochemical data from three piston cores in the central ulleung basin east sea we discuss the origin of organic matter and the depositional environment of sediments from marine isotope stage mis 3 to 1 downcore profiles show that the values of toc total organic carbon tn total nitrogen and 13corg are the lowest values during mis 2 and the highest during mis 1 the relationship between toc tn and 13corg shows that most data fall in the region of the marine algae irrespective of mis stage which illustrates that the organic matter has been predominantly produced by a marine source rather than by a terrestrial source since the late quaternary however depleted 13corg values are discretely observed during mis 2 and mis 3 particularly in dark laminated mud dlm which appears to reflect the influence of episodic event by the east asian monsoon rather than the organic matter source changing by lower sea level previous sedimentological studies in the ulleung basin reported that the depositional environment of sediment in mis 2 was more reducing than during mis 1 and mis 3 but our geochemical data do not support this interpretation the abundance of most redox sensitive trace elements e g mn v u and mo has not significantly varied from mis 3 to mis 1 in addition the ratios of redox sensitive trace elements e g ni co v cr v ni u th and v v ni indicate a predominantly oxic or suboxic environment the bottom water condition was similarly oxic to suboxic during times of sediment deposition since the late quaternary the sedimentary layers containing tephra and foraminiferal shell fragments illustrate abnormal element al ratios suggesting that these allochthonous sediment sources are one of important factors controlling the geochemical composition of sediments in the ulleung basin

dated coral reefs of southern sinai red sea and their implication to late quaternary sea levels abstract coral reefs of sinai constitute four morphological terraces three emergent fossil reefs and one submergent modern fringing reef labeled i 28 35 m above sea level ii 13 18 m iii 5 8 m and iv 1 to 1 m four genetic reef complexes which do not necessarily correspond to the morphological terraces were identified and dated the reef terrace age relationships are as follows 1 ophira terrace i 330 290 ka 2 mureikha terraces ii and or iii 215 170 ka 3 na ama terraces ii and or iii 141 81 ka 4 umm sid terrace iv 6 5 2 5 ka the age groups correspond to the oceanic oxygen isotope stages 9 7 5e and 1 the vertical uplift of the southern sinai coast which is situated along the western margin of the dead sea transform did not exceed 28 35 m during the last 300 000 years

oxygen isotopes sea level changes and the temperature history of a coral reef environment in new guinea over the last 105 years abstract coral reef terraces consisting of an upward succession of fringing and barrier reef types are preserved on land along the raising coast of huon peninsula new guinea seven coral reef units i vii from the coast landwards spaced at about 20 kyr interval provide a rather complete record of sea levels oxygen isotopes and temperature of teh surface tropical ocean over the duration of the high sea level events of the last glacial cycle the systematic sampling of the coral reefs was restricted to the massive tridacna gigas species the giant clam which are about 0 7 0 enriched in 18o relative to calcite equilibrium value and the presence of symbionts seems to have no effect on the 18o of their aragonitic skeleton sea levels rose rapidly to 5 6 5 m above present during the last interglacial which on stratigraphic grounds and 18o compositions can be separated into an early phase whose 18o is similar to modern reef viia dated at 138 kyr and a late phase that is 0 6 0 heavier reef viib dated at 118 kyr fringing reefs vi v iv iii and ii record short lived high sea levels stands at 107 85 60 45 to 40 and 31 kyr respectively that stopped short of the present sea level 12 19 28 32 to 42 m the general decline of the high sea level stands corresponds to an average 18o enrichment of 1 7 0 measured between the early interstadials of isotope stage 5 vi and v and the late interstadials of isotope stage 3 iv iiia iiib and ii the maximum 18o enrichment of 1 7 0 relative to present was registered during a regressive phase of reef iiia stratigraphic evidence indicates that sea level lows in the range of 37 to 55 m below present have occurred in between the high sea level stands but those are unlikely to represent the lowest sea levels of the last glacial cycle sea levels and 18o ddta pair offer important clues regarding the partitioning of ice volume and temperature in 18o records the results suggest that the ice volume effect accounts for the observed 18o changes during the early interstadial culminations but only for 29 46 during the late interstadial culminations sea water cooling beyond the threshold limit of coral reef growth 18 c did not occur during the last glacial cycle the temperature of the surface tropical ocean was similar to present during the early interstadials of isotope stage 5 and cooler by 3 c below present during the later interstadials of isotope stage 3

the last interglacial high sea level in the granitic seychelles indian ocean abstract in the granitic seychelles islands widely scattered remnants of marine limestones of late pleistocene age are found over a range of elevations within about 9 m with respect to present sea level these exposures can be subdivided into coralgal buildups and rubbly conglomerates 230 th 234 u dating from corals indicates that the limestones were deposited during the last interglacial stage 140 120 kyr b p in order to understand the sea level history for this time range various fabrics related to sequences of rock forming processes i e frame building bioerosion internal sedimentation cementation other depositional and diagenetic processes have been identified and used as possible indicators of paleosea level datum at their time of formation detailed examination of the rock fabric sequences in combination with radiometric dating reveals that sea level overstepped its present position around 140 kyr ago and reached its maximum altitude 135 kyr ago before retreating there were presumably two distinct events in sea level rise separated by a gap of about 10 kyr comparison between elevations of high sea stands of a similar age on a regional scale supports the contention that the seychelles area has been relatively instable since at least the late pleistocene either hydro isostatic uplift of the seychelles granitic bank or volcanic subsidence of nearby atolls are assumed to be responsible for such differences in paleosea level records

deep flow field in the japan east sea as deduced from direct current measurements abstract the mean flows and variability in the abyssal japan east sea are investigated on the basis of direct current observation data the distribution of the mean flow vectors indicates relatively strong cyclonic circulations along the basin periphery and sluggish flows in the interior region strong mean flows of faster than 6 0 cm s 1 are found at the western edge in the yamato and ulleung basins considered to be the western boundary currents in each basin the similarity between the distributions of the mean flow vectors in the upper 400 1000 m and lower layers 1000 m bottom indicates common circulation patterns throughout the water column of the proper water progressive vector diagrams show meandering curves with clockwise and anticlockwise turns due to the passing of mesoscale eddies since a dominant background flow is absent in the basin interior the ratio of eddy kinetic energy to the mean flow kinetic energy reaches more than 50 in the interior region this indicates that the flows observed in the interior region are comparable to those in the basin periphery even though the mean flow is generally weak spectral analysis has revealed that tidal fluctuations are prevailing in the ulleung basin while they are absent in the yamato and japan basins though the inertial oscillation is dominant in all of the basins this indicates that the tidal energy from the east china sea is confined within the ulleung basin suggesting the barrier effect of the yamato rise and the oki spur significant energy peaks are also found in the 2 5 and 5 10 day period bands in the yamato basin the former variation represents the shelf wave activity trapped on the basin edge and the latter is due to eddy migrations associated with the tsushima current

post depositional redistribution processes and their effects on middle rare earth element precipitation and the cerium anomaly in sediments in the south korea plateau east sea abstract we sampled two box core sediments from the slope of the eastern south korea plateau skp in the east sea sea of japan at water depths of 1400 and 1700 m two chemical fractions of extractable hydroxylamine acetic acid and residual rare earth elements rees together with al ca fe mg mn p s as mo and u were analyzed to assess the post depositional redistribution of rees extractable fe and mn are noticeably abundant in the oxic topmost sediment layer

instability of bottom water redox conditions during accumulation of quaternary sediment in the japan sea the concentrations of cd cr cu mo ni sb u v and zn were measured in early quaternary sediment 1 32 to 1 08 ma from the oki ridge in the japan sea the elements were partitioned between a detrital fraction composed of terrigenous and volcaniclastic aluminosilicate debris and a marine fraction composed of biogenic and hydrogenous debris derived from seawater the most important factors controlling minor element accumulation rates in the marine fraction were 1 primary productivity in the photic zone which largely controlled the flux of particulate organic matter bound minor elements settling through the water column and onto the seafloor and 2 bottom water redox which determined the suite of elements that accumulated directly from seawater this marine fraction of minor elements on oki ridge recorded six periods of high minor element abundance assuming a constant bulk sediment accumulation rate each period lasted roughly 5 000 to 10 000 years with a 41 000 year cycle accumulation rates of individual elements such as cd mo and u suggest sulfate reducing conditions were established in the bottom water during the 10 000 year periods accumulation rates of cr and v during the intervening periods are indicative of less reducing denitrifying conditions interelement ratios for example cu mo v cr and sb mo further reflect bottom water instability such that bottom water redox actually varied from sulfate reducing to denitrifying during the periods of highest minor element accumulation rates it varied from denitrifying to oxidizing during the intervening periods sediment lithology supports these interpretations of the minor element distributions the sediment is finely laminated for several of the periods represented by cd mo and u maxima and weakly laminated to bioturbated for the intervening periods the geochemistry of this sediment demonstrates the unambiguous signal of mo principally but of several other minor elements as well in recording sulfate reducing conditions in bottom water the forcing function that altered their accumulation that is that altered primary productivity and bottom water redox conditions is problematic currently held opinion suggests that o2 depletion was most strongly developed during glacial advances low sea level during such times is interpreted to have enhanced primary productivity and restricted bottom water advection

early diagenetic redistribution and burial of phosphorus in the sediments of the southwestern east sea japan sea this study was carried out in order to understand the early diagenetic redistribution of phosphorus and relevant mass balance in the sediments of the east sea in two cruises during may 1993 and october 1995 11 box cores were collected in the southwestern part of the east sea dissolved phosphorus and iron were analyzed in the porewater from the cores sediment samples were analyzed for solid phase p species and solid phase fe oxyhydroxide by sequential extraction phosphorus speciation results show that organic p is the major chemical form of phosphorus in young sediments within the upper 50 cm of sediment however the authigenic fraction of total p increases with depth indicating the precipitation of carbonate fluorapatite cfa in the sediments the authigenic cfa ca5 po4 2 6 co3 0 4f was formed and buried at rates of 11 110 mol cm 2 kyr 1 the main source of dissolved phosphorus for the precipitation of cfa is organic p dissolved phosphorus released from the decomposition of organic p diffuses upward to return to bottom water or is sorbed to iron oxides in the oxidized sediments as sedimentation proceeds the iron oxide bound p is released in the reduced layer and enters the dissolved phase which contributes p to the formation of cfa in addition to that contributed by the organic p the burial flux of reactive p iron oxide bound p authigenic p organic p is 0 09 0 53 g p m 2 yr 1 that accounts for 18 58 of the reactive p arriving at the sediment water interface the burial flux of reactive p is high in the upper and lower continental margin sediment the burial flux of reactive p in the ulleung basin sediment is less than those in the continental margin sites by a factor of 6 indicating that the reactive p burial flux is mainly dependent on sedimentation rate

inorganic geochemistry of the type caradoc series sandbian to middle katian upper ordovician onny valley shropshire uk the geochemistry and petrology of the type section of the caradoc series in the onny valley indicate that it was deposited on a marginal basin continental shelf similar to the western side of the present sea of japan the lower beds form a transgressive regressive sequence in which the rocks become less mature upwards all the coarser sediments above the basal quartzites and conglomerates are greywackes in which the apparent muddy and ferrous matrix is due to the breakdown of unstable minerals and particles higher values of na 2 o and na k ratios are found in the coarser shallow water sandstones of the horderley sandstone formation and decrease markedly in the succeeding beds accompanied by an increase in k 2 o higher values of carbonate corrected and hence related other major and minor elements like sio 2 cao p 2 o 5 mno and most trace elements correlate with the transgressive systems and maximum flooding surfaces of the three sequences recognized where they are related to condensation at those horizons chemical indices of alteration cia suggest that the horderley sandstone formation underwent greater predepositional physical weathering than lower and higher beds which is compatible with the petrography and were deposited during a cool phase within overall warm sandbian katian times trace element ratios suggest an oxic to suboxic depositional environment

the distribution of 230th234u ages in corals and the number of last interglacial high sea stands abstract the 104 available 230 th 234 u analyses of unrecrystallized corals from stable emerged terraces indicate that the last interglacial period occurred approximately 125 000 yr ago an estimate is made of the exact duration of this period by accounting for the surprisingly small distribution width observed among the 80 most reliable analyses this distribution width is compared with those obtained for model populations generated by assuming various characteristic analytical errors and various lengths of the last interglacial period the results show that 1 if there was only a single rise in sea level it probably lasted no more than 12 000 yr in agreement with previous estimates and 2 if there were two separate rises of sea level the gap between them must have been less than 7500 yr and not 12 200 as proposed by some authors

punctiform initiation of seafloor spreading in the red sea during transition from a continental to an oceanic rift transition from a continental to an oceanic rift occurs in the red sea by initial emplacement of oceanic crust in regularly spaced hot points which serve as nuclei for axial propagation into segments of oceanic crust accretion and for initiation of seafloor spreading hot points develop above upwelling mantle diapirs caused by density viscosity inversion beneath continental and oceanic rifts

cenozoic epeirogeny of the arabian peninsula from drainage modeling it is generally accepted that the arabian peninsula has been uplifted by subcrustal processes positive residual depth anomalies from oceanic crust in the red sea and in the gulf of aden suggest that a region surrounding this peninsula is dynamically supported admittance calculations surface wave tomography studies and receiver function analyses all imply that regional topography is generated and maintained by some combination of mantle convective circulation and lithospheric thickness changes despite these significant advances the spatial and temporal uplift rate history of the arabian peninsula is not well known here we show that a regional uplift rate history can be obtained by jointly inverting 225 longitudinal river profiles that drain this peninsula our strategy assumes that shapes of individual river profiles are controlled by uplift rate history and moderated by erosional processes we used local measurements of incision rate to calibrate the relevant erosional parameters in our inverse algorithm uplift rate is permitted to vary smoothly as a function of space and time but upstream drainage area remains invariant we also assume that knickzone migration is not lithologically controlled implications of these important assumptions have been investigated our results suggest that the arabian peninsula underwent two phases of asymmetric uplift during the last 20 30 ma at rates of 0 05 0 1 mm a 1 the southwestern flank of the peninsula has been uplifted by 1 5 2 5 km regional stratigraphic constraints the age and composition of volcanism paleosol formation incised peneplains emergent marine terraces and thermochronometric measurements corroborate our calculated patterns of uplift progressive development of three domal swells along the western margin of the peninsula is consistent with localized upwelling of hot asthenospheric mantle

stratigraphic and tectonic implications of uranium series dated coral reefs from uplifted red sea islands abstract corals from raised reef terraces on two islands zabargad and northern brother considered to have been tectonically uplifted in connection with the red sea rifting were dated with the u series method at zabargad there are at least three systems of raised coral reefs the oldest terrace 290 000 300 000 yr b p is found at 10 to 15 m a 200 000 yr b p high sea stand is recorded by a terrace relict at 17 m on peridotite bedrock the youngest system 125 000 138 000 yr b p is very well represented around the island with terraces at about 6 to 8 m corals from northern brother yield ages of 132 000 135 000 and 204 000 yr b p suggesting the existence of two systems of interglacial raised reefs both islands appear to have been tectonically quite stable since at least 125 000 yr b p

basin wide circulation and ventilation study in the east sea sea of japan using chlorofluorocarbon tracers abstract near synoptic basin wide distributions of the chlorofluorocarbon cfc tracers were observed during the summer of 1999 in the east sea sea of japan to study its circulation and ventilation the cfcs penetrate throughout the water column and the bottom water bw cfc concentrations have increased over measurements made in 1995 and 1996 indicating a continuous weak renewal of deep waters in the east sea during this recent period the cfc 11 water column inventory estimated in 1999 2000 5500 nmol m 2 is substantially higher than that of the adjacent north pacific ocean a striking anticorrelation between the bw dissolved oxygen and cfc concentrations in the japan basin is attributed to more active vertical mixing along the basin boundary a dynamically isolated deep eastern japan basin and recent changes in deep water ventilation the bw of the eastern japan basin with the lowest cfc content is the oldest water parcel in the east sea although it is colder and contains higher oxygen concentration than the surrounding bw active entrainment of overlying deep water is inferred from the unexpectedly higher bw cfc concentrations in the yamato basin this may explain why the yamato basin bw is warmer and less oxygenated than the other basins in the east sea although it is believed to be a terminus of the ventilated dws mesoscale anticyclonic eddies which have been fused with other deeply convected waters in the northwestern east sea seem to play an important role in transferring surface water properties to depths greater than 2500 m the subsurface cfc maximum centered within the typical east sea intermediate water esiw layer is more widely distributed south of the subpolar front than previously reported the esiw consists primarily of the colder and fresher winter surface water in the northern region that has subducted below the subpolar front

the rare earth element geochemistry of surface sediments in four transects in the south china sea and its geological significance seventy five samples of surface sediment were collected from four transects in the south china sea scs for analyses of rare earth element ree geochemistry total ree abundance ree in the scs varies from 45 to 195 ppm average 128 ppm lower than that of the upper continental crust the spatial distribution of ree is strongly dependent upon the geographical location and depositional environment low ree concentrations are observed on the continental slope e g xisha and nansha islands while high ree concentrations are present in the deep basin sediments on the slope are also characterized by lower lree hree la yb n eu eu and ce ce ratios relative to deep basin sediments there is a positive correlation between al2o3 and ree and a negative correlation between cao and ree conversely the relatively insignificant fe mn oxide accumulation in the scs suggests that manganese nodules do not make a significant contribution to the bulk ree composition of sediments therefore the sediment ree geochemistry is mainly controlled by terrigenous and biogenic sources biogenic carbonate has a diluting effect on ree concentrations but a significant influence on lree hree ce ce and la yb n values is found only in sediments with especially high biogenic carbonate levels the ree geochemistry of scs surface sediments indicates that their source is mainly post archean felsic rocks in the eastern sub basin the relatively low lree hree ratios and high eu eu values of the sediments indicate that significant terrigenous materials are derived from young volcanic rocks e g rocks in the luzon arc

paleoceanographic changes in the ulleung basin east japan sea during the last 20 000 years evidence from variations in element composition of core sediments a millennial scale paleoceanographic record of the ulleung basin in the southern part of the east japan sea es for the last 20 000 years was reconstructed based on variations in the element compositions of core sediment most of the elements showed relatively wide content ranges throughout the core largely because of different sediment types their grain size spectra biological components and geochemical conditions i e redox conditions in particular biogenic components ca sr ba and caco 3 and some minor elements cu mn mo u cd zn and v revealed three distinct intervals of major paleoceanographic changes interval 1 similar to 18 9 3 kyr bp is characterized by a rhythmic alternation of dark and light colored sediment bands distinctive differences in the abundance of organic carbon carbonate and redox elements between the dark and light colored sediment layers are probably attributable to especially those associated with bottom water redox variations combined with the enhanced primary productivity and water stratification in the ulleung basin

regional spatial distribution of multiple elements in the surface sediments of the eastern tsushima strait southwestern sea of japan abstract a total of 402 coastal sea sediment samples were collected from the continental shelf slope and basin off tsushima island in the western sea of japan and were analyzed for 51 elements as part of a nationwide marine geochemical mapping project the samples were compared to potentially related sample sets and the results were considered from the viewpoint of the origin of marine surface sediments in the western sea of japan the spatial distribution of elemental concentrations in the coastal sea sediments correspond to texture grain size the presence of shells and foraminifera and the mud content of surface marine sediments most elemental concentrations increased with increasing mud content some samples located in littoral areas included sediment particles apparently supplied from nearby rivers but their contribution was limited overall the mean chemical compositions of clastic material in coastal sea sediments appear to differ from those of stream sediments in adjacent terrestrial areas in addition the geochemistry of the coastal sea sediments cannot be fully explained by the mixing of the material supplied from korean and chinese stream sediments which are the most feasible sources coastal sea sediments in the study area are well mixed by transportation processes therefore elemental abundances in these marine sediments may be homogenized to such an extent that it is not possible to determine their origin alternatively most of the clastics in the sediment may actually represent relict reworked material originally formed in the yellow sea and tsushima strait during the last glacial stage and subsequent transgression

the geochemistry of redox sensitive trace metals in sediments abstract we analyzed the redox sensitive elements v mo u re and cd in surface sediments from the northwest african margin the u s northwest margin and the arabian sea to determine their response under a range of redox conditions where oxygen penetrates 1 cm or less into the sediments mo and v diffuse to the overlying water as mn is reduced and remobilized authigenic enrichments of u re and cd are evident under these redox conditions with the onset of sulfate reduction all of the metals accumulate authigenically with re being by far the most enriched general trends in authigenic metal accumulation are described by calculating authigenic fluxes for the 3 main redox regimes oxic reducing where oxygen penetrates 1 cm and anoxic conditions using a simple diagenesis model and global estimates of organic carbon rain rate and bottom water oxygen concentrations we calculate the area of sediments below 1000 m water depth in which oxygen penetration is 1 cm to be 4 of the ocean floor we conclude that sediments where oxygen penetrates 1 cm release mn v and mo to seawater at rates of 140 260 60 150 and 5 10 of their respective riverine fluxes using the authigenic metal concentrations and accumulation rates from this work and other literature these sediments are sinks for re cd and u with burial fluxes of 70 140 30 80 and 20 40 respectively of their dissolved riverine inputs we modeled the sensitivity of the response of seawater re cd and v concentrations to changes in the area of reducing sediments where oxygen penetrates 1 cm our analysis suggests a negligible change in seawater re concentration whereas seawater concentrations of cd and v could have decreased and increased respectively by 5 10 over 20 kyr if the area of reducing sediments increased by a factor of 2 and by 10 20 if the area increased by a factor of 3 the concentration variations for a factor of 2 increase in the area of reducing sediments are at about the level of uncertainty of cd ca and v ca ratios observed in foraminifera shells over the last 40 kyr this implies that the area of reducing sediments in the ocean deeper than 1000 m 4 has not been greater than twice the present value in the recent past

geotechnical properties of deep oceanic sediments recovered from the hydrate occurrence regions in the ulleung basin east sea offshore korea abstract this study presents comprehensive geotechnical data of the natural marine sediments cored from the hydrate occurrence regions during the ulleung basin gas hydrate expedition 1 ubgh1 east sea offshore korea in 2007 geotechnical soil index properties of the ulleung basin sediments including grain size distribution porosity water content atterberg limits specific gravity and specific surface area were experimentally determined these soil index properties were correlated to geotechnical engineering parameters e g shear strength and friction angle by using well known empirical relationships by performing standard consolidation tests on both undisturbed specimens as recovered from the original core liner after hydrate dissociation and remolded specimens stress dependent mechanical and hydraulic properties e g compressibility and hydraulic conductivity were measured the experimental results provide important engineering parameters and demonstrate the effect of hydrate presence and consequential dissociation to index properties engineering parameters and innate sediment structures

geochemistry of surface sediments off the southern and western coasts of korea abstract the continental shelf off the southern and western side of the korean peninsula is part of a modern epicontinental sea and is an effective sediment trap for clastic material derived from china and korea we have analyzed 179 surface sediment samples from this shelf for al fe na k mg ca ti p mn sr ba v cr co ni cu zn organic carbon and calcium carbonate in order to determine the geochemical characteristics of these sediments results showed a wide range of element contents which are mainly related to the textural variability of sediments exceptions to this were found in the contents of ca k sr and ba the ca and sr contents were largely determined by the amounts of carbonate present the k content on the other hand appeared to be influenced by both the contents of illite and feldspar and ba of potassium feldspar for muds i e sediments deposited under present day conditions it is possible to distinguish those in the central yellow sea from those in the keum estuary the former are characterized by high contents of fe na k mg ca and v and the latter by high contents of mn ba and co these differences become more apparent when these elements are normalized relative to al in order to minimize grain size effects the distribution of v al ratios is different from that of other elements the highest v al values occur in muds from the central yellow sea derived from the huanghe the yellow river in china whereas the highest values of mn al are found in the nearshore area adjacent to the korean peninsula based on these results it is suggested that the sources of fine sediments in the yellow and south seas can be distinguished from the geochemical characteristics of the surface sediments in the yellow sea two different sources of fine grained sediments can be seen the huanghe and the keum river the former is characterized by higher v contents and the latter by higher mn contents using the v al ratio as an end member component of the two source materials the dispersal patterns of the fine sediments 6o were also derived

provenance of late quaternary sediments on the southwestern slope of the ulleung basin east japan sea the provenance of fine grained sediments deposited since the late quaternary was recovered from drill site ubgh2 1 1 on the southwestern slope of the ulleung basin east japan sea based on geochemical analyses including rare earth elements rees the fine grained sediments could be interpreted as mixtures of sediments from china via various pathways and sediments discharged from the nakdong river nrs a comparison of variations in ree fractionation factor with marine isotope stages miss indicated that the provenance of the fine grained sediments on the southwestern slope of the ulleung basin was controlled by global eustatic sea level change during glacial periods most of the fine grained sediments were supplied via the atmospheric pathway by an intensified east asian winter monsoon and sediments from chinese rivers crs transported into the ulleung basin through the korea strait were limited due to the morphological characteristics of the korea strait and low sea level during interglacial periods the crs transported into the ulleung basin through the korea strait increased with sea level rise and eolian dust inputs decreased due to attenuated east asian winter monsoon simultaneously nrs also should have been deposited when sea level was higher than 40 m relative to present sea level during mis 1 and mis 5 in particular during mis 1 signals of nrs were revealed since 11 ka thus it can be suggested that the present coastal current system around the southeastern coast of korea became established by around 11 ka

stratigraphy palaeoenvironments and model for the deposition of the abdur reef limestone context for an important archaeological site from the last interglacial on the red sea coast of eritrea stone tools discovered within uplifted marine terraces along the red sea coast of eritrea at the abdur archaeological site dated to 125 7 ka the last interglacial marine isotope stage 5e show that early humans occupied coastal areas by this time walter et al 2000 nature 405 65 69 in the present paper the stratigraphy facies types and faunal composition from 25 measured sections of the tool bearing abdur reef limestone arl are documented in detail and interpreted to provide a palaeoenvironmental context for the stone artefacts and a model for the deposition of the arl the arl represents a complex marine terrace sequence erosional surfaces indicative of interrupted sedimentation are locally observed at two levels within the arl they subdivide the complex into three subunits named 5e1 5e2 and 5e3 representing different stages of the marine isotope stage 5e sea level highstand comprising six depositional phases i vi of the arl subunit 5e1 begins with the initial transgression of the 5e sea level highstand leading to the deposition of widespread lag gravels on which rich oyster beds developed in shallow water phase i it further records rapid deepening accompanied by the deposition of low energy carbonates with scarce corals phase ii and later shoaling characterised by local development of a fringing reef tract in a sedimented environment phase iii subunit 5e1 is capped locally by a burrowed hardground that is laterally equivalent to depositional discontinuities interpreted as caused by a globally recognised mid 5e sea level low stand phase iv extensive reef build up in response to sea level rise and improved conditions for coral growth characterises subunit 5e2 phase v a possible second sea level drop during the 5e highstand is inferred from the oyster encrusted upper surface of subunit 5e2 subunit 5e3 encompasses restricted coral patches that developed on the upper surface of the underlying subunit during the last stage of the 5e marine high stand phase vi two different toolkits are found in the arl one consists of bifacial hand axes and cores of the acheulian industry typically associated with the oyster beds encrusted on the transgressive lag deposits the other consists of middle stone age msa type obsidian flakes and blades mainly found in the nearshore and beach environments alongside debris from marine invertebrates and large land mammals the distribution of these tools suggests that foraging activities of early humans varied with environmental setting the abdur archaeological site represents a late example of the acheulian msa transition seen as a benchmark for early modern human behaviour and is to date the earliest well dated example of early human adaptation to marine food resources

rare earth elements in the east sea japan sea distributions behaviors and applications abstract the distributions of rare earth elements rees were measured at 14 stations from 0 to 3365 m n 176 in the entire east sea for the first time the east sea has its own deep convection system which operates on a time scale that is approximately one tenth that of the global ocean it is also a downwind region of asian dust the vertical distributions of ree concentrations increased with depth similar to those in the north atlantic ocean however the concentrations of rees were 1 3 2 7 fold higher than those in the north atlantic ocean associated with relatively larger atmospheric depositions of dust from the asian continent in this environmental condition the removal of ce relative to the other rees was about an order of magnitude more efficient than that in the north pacific ocean as such in the deep layer below 750 m large increases of heavy rees hrees relative to light rees lrees opposite to the re mineralization trend were observed suggesting that lrees were preferentially re scavenged by sinking particles in addition the boundary scavenging of rees was also observed for all rees in the bottom layer of the east sea on the other hand the warm surface waters of rees tsushima warm water tww showed large fractionations relative to the other water masses this ree pattern traced the deep physical mixing proportions of tww up to 750 m 10 thus the unique distribution patterns of rees in this sea illustrate the geochemical scavenging characteristics of rees which are concealed in the major oceans as well as water mass mixing patterns in the upper ocean

internal gravity waves in a saturated moist neutral atmosphere abstractthis work is motivated by an unusual feature associated with the start up of a moist nearly neutral atmospheric flow over a mountain ridge that was previously observed in a full physics numerical model in that study the upstream propagation of a wave of subsidence precluded the establishment of upward displaced and saturated flow that might be expected upstream of the topography this phenomenon was hypothesized to be a consequence of the peculiar property of saturated moist neutral flow an upward air parcel displacement produces zero buoyancy while a downward displacement desaturates the air parcel and produces a positive buoyancy anomaly in the present study this hypothesis is confirmed within numerical solutions to a reduced system of equations that incorporates the saturated atmosphere property in a particularly simple manner the relatively uncomplicated nature of these solutions motivates the numerical solution of a further simplified initial value problem for both nonhydrostatic and h

particulate manganese and iron in recent sediments of the gulf of lions continental margin north western mediterranean sea deposition and diagenetic process abstract this study aims at apprehending the major forcing factors which govern the spatial and vertical mn and fe distributions in ten cores from the gulf of lions speciation by chemical leaching experiments helps understanding their chemical behaviour during the early diagenetic processes in a marine environment under strong continental influence the distribution and chemical behaviour of mn and fe differ drastically the strong dependence of mn distribution on chemical conditions is expressed by a marked solid phase mn enrichment in the oxic layers of sediment deposits this enrichment increases with decreasing sedimentation rate increasing water depth it is illustrated by an enhanced portion of total mn in the reducible phase and the precipitation of todorokite on calcareous supports in the upper part of the deepest cores as a result 65 of the margin total particulate mn is thought to be stored in slope deposits in a relatively strongly held association conversely the low chemical mobility of iron in the sedimentary column is indicated by uniform depth profiles and an exclusive location in the residual chemical phase in all the studied sites the fe distribution is largely controlled by the dispersion of particulate material on the margin from the rhone river main source a budget of mn and fe accumulation based on the average amount of total mn and fe content of sediments deposited during the last 100 yr has been made taking into account diagenetic readjustments the total mn and fe amount stored on the margin during the last century is estimated to be 1 5 106 and 54 106 t respectively these values are seven times higher than the total secular external inputs calculated on the basis of present day riverine and atmospheric fluxes this large discrepancy is mainly explained by the sharp decrease of the rhone river discharge after dam buildings between 1950 and 1958 a residual discrepancy dating before 1950 is likely to be due to seafloor erosion and gravity induced mechanisms

dating indian corals by u decay series methods abstract nine samples of corals collected from seven locations in the saurashtra coastal region of india were dated by 238 u series disequilibrium methods of the three age groups 6000 30 000 and 120 000 yr reported for this region by the earlier studies of s k gupta and b s amin 1974 marine geology 16 79 83 we could confirm only the 6000 yr group instead of a 120 000 yr group we found a scatter of ages between 118 000 and 176 000 yr there appears to be no evidence for 30 000 yr old corals from this region

multielement geochemistry of offshore sediments in the southeastern yellow sea and implications for sediment origin and dispersal abstract in total 116 surface sediments were collected from an offshore area of the southeastern yellow sea including a large mud belt southeastern yellow sea mud seysm and analyzed for grain size and geochemical composition organic carbon and 42 elements principal component analysis revealed that elemental compositions of the offshore sediments were mostly controlled by common aluminosilicate clay minerals and quartz most elements heavy minerals hf zr u th rare earth elements rees biogenic calcium carbonates ca sr feldspar and mica k ba pb and mn oxides mn oxide coatings on sand grains notably total ree concentrations may be associated with heavy minerals possibly zircon and monazite especially in silty grains even though heavy ree hrees concentrations are more strongly controlled by clay minerals in muddy sediments the diagnostic discrimination plots of geochemical compositions e g fe vs al mg vs al light ree vs hree and la lu ucc vs la y ucc suggested that the offshore sediments especially in seysm deposits were composed of a mixture of korean river derived silts and chinese river derived clays this demonstrated that chinese river sediments especially clay particles largely contributed to the formation of the giant mud belt in the korean coastal area furthermore the observed geochemical end members provide new markers of sediment provenance which can be used to track dispersal patterns and sediment limits from chinese and or korean rivers

discrimination of sediment provenance using rare earth elements in the ulleung basin east japan sea abstract in order to discriminate the origins of ulleung basin east japan sea sediments using rare earth elements rees sediments from 15 box cores and one piston core collected in the shelf slope and basin were analyzed for major elements al fe ca and mn and rees the major sedimentary components in this basin were presumed to be detrital materials from land even in the basin sediments based on al and organic contents carbon and opal post depositional recycling processes involving fe and mn were identified in the basin sediments thus the ce anomaly and the fractionation factors of light rees lrees and middle rees mrees relative to heavy rees hrees could not be used as provenance indicators in the deep basin sediments 2000 m of water depth based on a feasibility check using their covariation with fe and mn for the shelf slope and basin b sites near islands water depths of 1200 1800 m regions the eu anomaly lreen hreen and mreen hreen could be successfully used to discriminate possible provenances including nakdong river sediments nrs chinese river sediments crs ulleungdo volcanic rocks uvr and dokdo volcanic rocks dvr from the provenance indicators slope as well as the shelf sediments called the korea strait shelf mud kssm in the ulleung basin can be regarded as mixtures of nrs and crs with decreasing portions of nrs in the kssm with distance from the nakdong river basin b sediments were mixtures of uvr or dvr and crs these findings can be explained if sediments discharged from the nakdong river were transported and deposited kssm northward within the strong coastal front in normal periods and if sediment flumes from summer floods flowed out across the coastal front were carried with the tsushima warm current and then deposited in the slope area this study indicated that crs were very important detrital sediments and that ree compositions can be successfully used as a provenance indicator in even hemipelagic sediments close to land