sedimentology csfe relationships and stable isotopic compositions in devonian black mudrocks mackenzie mountains northwest territories canada abstract an integrated approach combining c s fe relationships stable isotopic compositions and lithofacies characterization was utilized to constrain the palaeoenvironmental and early diagenetic conditions of middle upper devonian eifelian frasnian mudrocks from the mackenzie mountains northwest territories canada these rocks include the hare indian formation informally subdivided into the lower bluefish member and the hare indian upper member carcajou marker and canol formation the bluefish member is dominated by black laminated organic rich shales toc 0 35 10 34 wt av 5 83 wt with moderate degrees of pyritization dop of 0 34 0 67 av 0 55 these mudrocks were deposited in dysoxic marine bottom waters that became progressively more oxygenated with time variations in toc dop and organic matter 13cpdb values 29 7 to 19 9 av 27 2 are attributed to repeated clastic dilution and increased input of terrestrial organic matter in association with shallowing upward ramp clinothem cycles pyrite 34scdt values 32 7 to 18 8 av 24 9 indicate an open system bacteriogenic seawater sulphate reduction conversely the overlying hare indian upper member characterized by clinothem facies is composed of grey to green mudstone with minor argillaceous limestones and considerably less organic matter contents toc 0 28 2 99 wt 13c 29 5 to 22 5 deposition occurred in oxic to slightly dysoxic waters dop 0 20 0 54 34s 23 0 to 20 9 depending on the palaeotopographic location along the depositional slope a rapid rise in sea level drowned the carbonate ramp member of the ramparts formation and produced the thin organic rich carcajou marker bottom water stagnation that resulted from subdued ramp palaeotopography produced anoxic sea bottom black laminated organic rich shales from the canol formation toc 1 37 6 68 wt are very similar to those of the bluefish member and are likewise basinal sediments however toc dop and organic matter 13cpdb values 29 1 to 20 8 av 26 2 do not show pronounced variations and indicate that low energy quietwater conditions persisted over relatively long uninterrupted periods of time high dop values 0 72 0 93 throughout the canol formation suggest that deposition occurred in anoxic bottom waters but as basin fill conditions continued there was a shift to a dysoxic environment dop 0 55 0 65 which grades into nearshore and offshore sequences of the overlying imperial formation in contrast with the hare indian formation much heavier 34scdt values of pyrite in canol mudrocks 11 1 to 5 3 av 3 1 point to bacterial sulphate reduction in a closed to semi closed system with respect to seawater sulphate

environmental geochemistry of core sediments from serthalaikkadu creek east coast of india the serthalaikkadu creek in muthupet mangroves region is the only e w trending coastal strip in the se coast of india and it also acts as a barrier to natural disasters natural anthropogenic signals and accumulation of elements were studied by collecting sediments from two cores textural parameters were studied in detail and carbonates caco3 organic carbon oc major si al fe na k ca mg p and trace elements mn cr cu ni co pb zn were determined textural parameters caco3 oc and al normalized pattern of elements indicate depositional events in core samples that can be directly related to natural events during the last decade the calculated enrichment anthropogenic factors and comparison of data indicate that the observed trace metals especially pb co are enriched mainly due to the anthropogenic activities in the land as well as in the coastal zone palk strait

sedimentary responses to sea level rise and kuroshio current intrusion since the last glacial maximum grain size and clay mineral evidence from the northern south china sea slope abstract we analyzed the terrigenous fraction of a sediment core from the northern slope of the south china sea to better understand the depositional history of the region since the last glacial maximum lgm temporal variations in the grain size and clay mineral composition revealed a complex set of overlapping controls approximately 90 of terrigenous sediment throughout the core ranged in size from 5 5 to 8 5 with the 5 25 6 25 size class being particularly sensitive to environmental changes the proportion of this fraction decreased during deglacial indicating a reduction in the supply of coarser grains due to coastline retreat as the sea level rose toward its present position the relative proportion of clay derived from taiwan increased however the mass accumulation rate of taiwan derived clay decreased suggesting a reduction in the westward bottom current intensity in contrast the relative contribution of clay from the pearl river decreased from 40 during the lgm to 5 when the sea level reached 70 m below its present position the pearl river contribution has remained consistently low throughout the holocene indicating that shore parallel circulation patterns on the shelf resembled their present configuration by 13 ka compared to taiwan and the pearl river the proportion of clay derived from the area east of pearl river epr was relatively minor and less variable a local peak in the relative contribution from this area occurred during a melt water pulse event mwp 1a suggesting that a reservoir of smectite rich clays residing in coastal bays was remobilized by this marine transgression spectral analysis of the relative contributions of the three major clay sources revealed a significant periodicity of 380 years which may reflect changes in solar insolation modulating the flux of clay minerals from taiwan and the pearl river to the deposition site on a centennial scale

unchanged nitrogen isotopic composition of organic matter in the south china sea during the last climatic cycle global implications the 15n of surface and down core sediments spanning the last 20 200 kyr from the entire south china sea scs ranges only from 3 0 to 6 5 with no correlation with discernible paleoclimatic oceanographic changes detailed profiles of the uppermost sediment column including fluff samples indicate a minor diagenetic overprint of 0 3 1 2 at the sediment water interface the absence of any correlation with reconstructed glacial interglacial changes in primary production terrigenous input and or sea level related basin configuration is attributed to a complete consumption of nitrate during primary production in this marginal basin during at least the last 140 000 years this in turn implies that the 15n of the nitrate used during primary production remained approximately constant during the last climatic cycle the proposed scenario infers an unchanged nitrogen isotopic composition of the western pacific subsurface nitrate between glacial and interglacial stages as well as during terminations and thus constrains proposed changes in the oceanic n inventory

glacial holocene biogenic sedimentation patterns in the south china sea productivity variations and surface water pco2 a bathymetric transect of cores in the south china sea extending from 4200 m to less than 1000 m water depth has been examined for glacial interglacial changes in carbonate and organic carbon sedimentation typical pacific carbonate cycles high carbonate content during glacials and low carbonate content during interglacials characterize cores from water depths deeper than 3500 m in contrast atlantic carbonate cycles low carbonate during glacials and high carbonate during interglacials are observed in cores from depths shallower than 3000 m as a result of increased dilution of carbonate by terrigenous material during glacial low stands of sea level glacial interglacial changes in the carbonate chemistry of south china sea intermediate and deep waters resulted in significant changes in the positions of the carbonate compensation depth ccd and the aragonite compensation depth acd during the last glacial the ccd and acd were at least 400 and 1200 m deeper respectively than at present organic carbon accumulation rates in the south china sea were approximately 2 times higher during the last glacial than the holocene carbon isotopic analyses and c n ratios of the organic matter indicate that only a small fraction of the increase in glacial organic carbon accumulation can be attributed to input of terrestrial carbon on the basis of this we conclude that surface water productivity in the south china sea was approximately 2 times higher during the last glacial maximum this is consistent with previous studies which have demonstrated that glacial productivity was higher in low to mid latitude regions of the atlantic and eastern pacific the deglacial decrease in organic carbon accumulation is accompanied by a decrease in 13corg using the relationship between 13corg and co2 aq developed by popp et al 1989 we estimate that surface water pco2 values in the south china sea during the last 25 000 years were very similar to atmospheric co2 concentrations

geochemistry of core sediments from mullipallam creek south east coast of india the mullipallam creek in muthupet mangroves region is the only e w trending coastal strip in the se coast of india and is very important as the mangrove acts as a barrier to natural diasters natural anthropogenic signals and accumulation of elements were made by collecting sediment samples at various depths in a core all sediments were analyzed for carbonates caco3 organic carbon oc major si al fe na k ca mg p and trace mn cr cu ni co pb zn normalization with al values has been done for all the major and trace elements and enrichment factors have been calculated the calculated enrichment factors and comparison indicate that the trace metals especially pb are enriched mainly due to the external anthropogenic activities in the land as well as in the coastal zone palk strait

opaline and al si phytoliths from a tropical mire system of west malaysia abundance habit elemental composition preservation and significance abundant and unique opaline and al si phytoliths and opaline bioliths have been discovered in holocene peat deposits of tropical tasek bera in peninsular malaysia these are secreted mainly by plants higher plants and algae and incorporated in the sediment cycle during the rapid biomass turnover many wetland plants have entire skeletons secreted the study shows that differing plant parts of same species as well as same parts of differing plant species incorporate different amounts of elements whilst deciduous trees of the swamp forest have phytoliths enriched in al most phytoliths of palms sedges and grasses of the littoral swamp are composed of opaline silica incorporation of al and many other elements into relatively stable phytoliths is the result of high evapotranspiration rate and ample plant available elements and can serve to detoxify the soil solution because of the abundance of such opaline and al si structures spongillid and algal remains in acid peat accumulating environments tropical peatlands represent repositories of si and al which together with variable amounts of other elements could provide the prime material for silicate neoformation during later diagenetic processes neoformation of minerals from bioliths would explain the scarcity of biogenic remains in carboniferous and tertiary coal deposits furthermore incorporation of major elements in phytoliths may limit the rate of leaching of these elements in an environment where biomass turnover is rapid thus reducing the loss of nutrients and other plant essential elements most nutrients of tropical peats are recycled by plants within the top 150 cm and an upward migration of plant essential elements such as mg ca or p but also of si and al occurs during peat accumulation such elemental cycling strongly influences the geochemical composition of the peats during mire evolution utilizing al for normalization of major and minor elements of tropical peats for paleoclimatic and paleodepositional analyses may thus result in incorrect interpretations

the late pleistocene history of surface water δ13c in the sulu sea possible relationship to pacific deepwater δ13c changes a reconstruction of late pleistocene surface water carbon isotopic 13c variability is presented from ocean drilling program odp site 769 in the sulu sea in the western tropical pacific the sulu sea is a shallowly silled back arc basin with a maximum sill depth of 420 m site 769 was drilled on a bathymetric high in 3643 m of water and has average late pleistocene sedimentation rates of 8 5 cm kyr the oxygen isotope record 18o of globigerinoides ruber at site 769 shows a strong correlation with the specmap stacked 18o record attesting to the continuity of sediment archive at the site surface 13c displays consistent glacial interglacial variability which averages 0 9 and has varied from 0 75 to 1 1 over the last 800 kyr comparison to surface water 13c records in the south china sea and western tropical pacific suggests that the glacial interglacial surface 13c variability is regional in scale planktonic 13c data from odp site 677 in the eastern pacific is also coherent with the site 769 additionally we have found that the site 769 surface 13c record is coherent at periods of 100 and 41 kyr with deepwater 13c records from the pacific the highest correlation occurs with the deep eastern pacific where benthic 13c data from cores rc13 110 and odp site 677 closely match the sulu sea surface water record we evaluate several possible controls of surface water 13c in the sulu sea that may explain the coherent timing with pacific deepwater 13c records these include variations in terrestrial organic matter flux to the basin the upwelling of subsurface water and productivity changes and the influx of western pacific intermediate water to the sulu sea our preferred explanation involves a region of upper intermediate water upwelling in the far western pacific which has been shown to outgas co2 from subsurface waters into surface waters upwelling also occurs in the area of panama basin site 677 these equatorial upwelling zones could potentially provide a route by which pacific intermediate water can modulate the 13c composition of certain pacific surface water locations future reconstructions of late pleistocene surface water 13c variability in the western pacific and indonesian seas will be required to further evaluate the source of the glacial interglacial surface water 13c change

calcareous nannofossils in surface sediments of the eastern and western south china sea abstract a detailed interbasinal study of calcareous nannofossils in surface sediments and their environmental preferences was conducted across the south china sea from the upwelling area off vietnam to the non upwelling area off luzon philippines emiliania huxleyi florisphaera profunda and gephyrocapsa oceanica are the dominant taxa in all the stations comprising 72 100 of the total nannofossil assemblage in the shallow coastal waters and nearshore environments in the western portion the dominant taxa are e huxleyi and g oceanica offshore towards the central abyssal portion of the scs f profunda dominates the nannofossil assemblage distribution patterns observed in this study as well as the results of the principal components analysis confirmed and established environmental preferences not only of the three major taxa but of several minor taxa as well based on these results and cluster analysis of the samples three assemblages were recognized in the study area a upwelling b oceanic and c deep basin assemblages the upwelling assemblage is associated with the vietnam and sunda shelves upwelling areas and is dominated by e huxleyi and g oceanica the oceanic assemblage encompasses the outer shelf to slope environments and is characterized by the common occurrence of f profunda and e huxleyi western study area and f profunda and g oceanica eastern study area the deep basin assemblage includes the abyssal portion of the scs below the inferred lysocline and calcite compensation depth and is dominated by f profunda 80 it is proposed in the present study that f profunda is resistant to dissolution

oxygen minimum expansion in the sulu sea western equatorial pacific during the last glacial low stand of sea level the sulu sea in the western equatorial pacific is presently a shallowly silled dysaerobic deep marine basin deep waters in the sulu sea are ventilated through a single sill at 420 m depth which connects it to the china sea benthic and planktonic foraminiferal oxygen and carbon isotope records benthic and planktonic foraminiferal census data and total organic carbon measurements have been used to evaluate changes in water mass conditions in the sulu sea between the last glacial maximum 18 000 yrs b p and the present day an increase in the abundance of the planktonic foraminiferaneogloboquadrina dutertrei and relatively light planktonic foraminiferal 18o values suggest that during the last glacial maximum surface water salinities were reduced in the sulu sea enhanced isolation of the basin due to glacio eustatic lowering of sea level and reduced surface salinities resulted in stagnation of deep water and an expansion of the mid water oxygen minimum layer increased organic carbon preservation at mid water depths occurs at this time benthic carbon isotope data and an increase in the abundance of benthic foraminiferal species considered to prefer low oxygen environments support the conclusion of an oxygen minimum expansion at mid water depths during the last glacial maximum at water depths greater than 4000 m bottom waters appear to have maintained some degree of oxygenation during the last glacial maximum stronger pacific ocean trade winds at this time may have caused the influx of denser celebes sea surface water into the southern part of the sulu sea the slow sinking of this water would have then ventilated bottom waters in this part of the basin at the transition from glacial to interglacial conditions rising sea level caused denser water to flow over the deepest sill into the sulu sea vertical circulation increased resulting in a greater downward flux of oxygen and a dissipation of the oxygen minimum continued post glacial sea level rise caused periodic ventilation of deep water until the present dysaerobic conditions were established

astronomical forcing of the east asian monsoon mirrored by the composition of pliocene south china sea sediments abstract high precision major and minor element records of pliocene core intervals from ocean drilling program odp site 1145 located in the northern part of the south china sea were generated at a 5 cm approximately 2 kyr resolution from the geochemical data distinct proxies those indicating changes in detrital matter provenance as well as those indicating productivity variations could be derived both the terrigenous input to the northern south china sea k si and variations in productivity ba al show a response to insolation forced monsoon variability while the fluvial input k si responds to changes in the summer monsoon productivity increases as documented by ba enrichments seem to reflect variations in winter monsoon intensity a stronger winter monsoon may have increased nutrient availability via dust input and or upwelling phenomena according to our geochemical proxy records summer and winter monsoons are approximately 180 out of phase this may imply forcing of the winter monsoon through southern hemisphere summer insolation maxima the k si ratio shows a linear correlation with the la90 1 0 5 northern hemisphere summer insolation record and has therefore been used to create an astronomical timescale for the investigated sediments of odp site 1145 carbonate contents and corresponding color reflectances display 41 and 100 kyr cycles we propose that these do not reflect glacial cycles but are rather the result of an interference signal of dilution by fluvial and eolian terrigenous material and carbonate production burial flux a sudden onset of gradual changes in sediment composition occurs after 3 0 ma this is also documented by an increase in sedimentation rates and may be caused by enhanced fluvial input from the pearl river due to intensified weathering rates on the asian continent this may be linked to tectonic processes around the himalayan tibetan complex and its consequences regarding land sea heating and atmospheric circulation

old iodine in fluids venting along the central american convergent margin focused fluid expulsion at cold vents is a common feature of subduction zones serving as an important backflux of water and volatile elements to the oceanic reservoir the strong enrichment of iodine in fluids collected from mounds along the central american convergent margin allowed the determination of 129i i ratios for age calculations in order to determine potential source formations in this active erosional margin the majority of the determined iodine ages are between 40 and 20 ma because these ages are older than the age of host sediments and underthrust sediments on the oceanic plate 18 ma a major contribution of iodine must come from old organic rich sources in the upper plate both the iodine concentrations and ages determined for the mounds in this study are similar to reported values for hydrate fields at accretionary margins indicating that iodine and associated organic carbon cycling at both erosional and accretionary margins may occur on similar time scales

correction to west antarctic ice streams draining into the ross ice shelf configuration and mass balance by sion shabtaie and charles r bentley

two phase structure of tropical hydroclimate during heinrich stadial 1 and its global implications abstract previous studies have proposed that the two phase structure of heinrich stadial 1 hs1 is a ubiquitous feature however few studies have focused on the internal structure of hs1 over a tropical domain thus the interhemispheric ocean atmosphere teleconnections during hs1 are poorly defined here we present high resolution sedimentological geochemical and palaeoceanographic records from the core cg2 in the southern south china sea scs off the northern sunda shelf the core continuously spans 9 0 22 0 ky bp the records suggest two episodes of increased monsoon rainfall during the pre hs1 19 0 18 0 ky bp and in the early hs1 17 5 16 1 ky bp along with a weaker monsoon rainfall during the late hs1 16 1 14 7 ky bp in contrast a lower precipitation over the flores sea occurred during the early hs1 off the southern sunda shelf followed by an enhanced precipitation runoff during the late hs1 muller et al 2012 notably these two different precipitation phases characterise a southward intertropical convergence zone itcz shift over the sunda shelf during hs1 these changes are also consistent with other monsoon records as well as other available data from the tropical to high latitudes of both hemispheres supporting the global scope of the twofold hs1 we propose that the two episodes of intense monsoon rainfall over the northern sunda shelf during the pre hs1 and the early hs1 observed in our study are closely linked to two different melting events associated with european ice sheet eis retreat we further propose that the subsequent maximum atlantic meridional overturning circulation amoc reduction and the migration of the itcz to its southernmost position during the late hs1 are tightly connected with the destabilization of the marine terminating ice streams of the laurentide ice sheet lis in the north atlantic tropical positive feedbacks during hs1 in turn should have played an important role in sustaining the amoc reduction and northern hemisphere nh stadial conditions by continuously lowering the salinity of the low latitude currents in the atlantic ocean in addition the tropical itcz appears to have been a key bridge in promoting interhemispheric climate connections by which north atlantic cooling was rapidly linked to increased southern ocean surface westerlies this in turn drove upwelling and co2 ventilation from the southern ocean and thereby facilitated deglacial warming finally these findings show that tropical climate variation is an important component of deglacial climate changes understanding how it responds to millennial events like hs1 may help us better understand global teleconnections

trace metal cycling in the deep water of the south china sea the composition sources and fluxes of sinking particles moored sediment traps were deployed for 1 yr at depths of 120 600 and 3500 m in the water column to investigate the trace metal m al ti v cr mn fe co ni cu and zn composition sources and fluxes of deep water sinking particles vertical transport for most of the metals at 120 m was strongly associated with organic matter production and the major part of many of the metals in the sinking particles was of anthropogenic origin although the lithogenic fraction in deeper waters greatly increased with depth significant proportions of the nonlithogenic and nonintracellular fractions were still observed when using m al or m p ratios as indicators particularly for zn cu ni co and mn because particles from horizontal transport and sediment resuspension are known to be lithogenic in the deep basin the trace metals in sinking particles in the twilight zone and deep water which feature significantly elevated m al ratios originate from the downward transport of anthropogenic or authigenic origins with increasing inputs from anthropogenic aerosols over large oceanic regions globally the coupling and transport of some trace metals originating from anthropogenic aerosols such as zn cu co and ni with sinking organic particles has become an important pathway for trace metal cycling not only in the euphotic zone but also in the twilight zone and deeper waters

enrichment of trace metals in surface sediments from the northern part of point calimere se coast of india this study deals with the geochemical nature of distribution enrichment of total trace metals fe mn cr cu ni co pb zn cd in bulk sediments and its association with sediment texture carbonates and organic carbon sixty surface sediment samples were collected during two different seasons in 2002 and 2003 along the coastal regions in three transects from nagapattinam town north of point calimere in southeast coast of india the sediments are mostly sandy silt and are dominated by the carbonate content organic carbon distribution indicates that they are brought in by the minor river input enrichment of trace metals is clearly identified by the domination of pb zn cd with high values than the average crustal values and comparison of trace metals from other coastal regions in the southeast coast of india statistical analysis clearly indicates that fe and mn control the distribution of trace metals and are concentrated in the finer particles and organic carbon fraction the increase in concentration signifies the need for regular monitoring of the offshore coastal region in southeast coast of india which was recently destroyed by the 2004 december tsunami event and which is also located near the sethu samuthram ship canal project

southern hemisphere forcing of pliocene δ18o and the evolution of indo asian monsoons monsoon phase relationships consistent with direct orbital forcing across the entire indo asian region including marine and terrestrial proxies from the chinese loess plateau the south china sea and the arabian sea strong pliocene summer and winter monsoons were in phase with one another strengthened at obliquity minima and precession minima the summer monsoon was also strengthened at precession maxima yielding a semiprecession spectral signal strong pliocene monsoons at orbital extremes indicate a direct response to fast physics processes including sensible heating and cooling of the asian landmass and for the summer monsoon the export of latent heat from the southern indian ocean as northern hemisphere ice volume grew into the pleistocene the timing of strong winter and summer monsoons drifted apart becoming influenced by the combined effects of fast physics and slow physics ice volume variables the phase of strong winter monsoons shifted toward ice maxima and the phase of strong summer monsoons shifted toward ice minima

a critical review of marine sedimentaryδ13corg pco2 estimates new palaeorecords from the south china sea and a revisit of other low latitude δ13corg pco2 records in an attempt to understand better the local biogeochemistry of the south china sea scs and to unravel the contribution of this marginal low latitude basin to changes in atmospheric co2 concentrations we analyzed the carbon isotopic composition of organic matter 13corg in four sediment cores from throughout the scs covering the last 220 kyr higher values around 19 5 to 20 5 mark glacial stages while lower values around 21 to 22 5 are characteristic of interglacials following well established procedures the 13corg records are converted to local pco2 estimates on the basis of these and other low latitude 13corg pco2 estimates from the literature we present a critical evaluation of the use of 13c of bulk sedimentary organic matter to hindcast past changes in local co2 aq three crucial pitfalls are identified 1 given the present inability to quantify precisely the time varying amount of terrigenous corg input to marine sediments absolute values of pco2 estimates based on bulk sedimentary corg are questionable 2 none of the low latitude sedimentary 13corg pco2 records shows the expected correlation between temporal changes in upwelling intensity and co2 estimates most likely due to the antagonistic influences of co2 aq and phytoplankton growth rate on 13corg 3 a detailed comparison of marine 13corg pco2 records with the vostok co2 record reveals significant differences in phasing specifically at the end of the last deglaciation and during the oxygen isotope stage 5 4 transition however in areas where equilibrium between oceanic and atmospheric co2 occurs for example the scs and the mediterranean the timing of changes in 13corg should agree with the co2 record from ice cores if 13corg is a reliable proxy for changes in co2 aq taken together the compilation of records presented here cautions the use of 13corg as an unambiguous tracer of dissolved molecular co2 in the surface ocean and calls for a re evaluation of the role of the low latitude ocean on temporal changes in atmospheric co2

bromine and iodine in peru margin sediments and pore fluids implications for fluid origins at the peruvian convergent margin two distinct pore fluid regimes are recognized from differences in their cl concentrations the slope pore fluids are characterized by low cl concentrations but elevated br and i concentrations due to biogenic production the shelf pore fluids exhibit elevated cl and br concentrations due to diffusive mixing with an evaporitic brine in the slope pore fluids the br i and nh4 concentrations are elevated following bacterial decomposition of organic matter but the i concentrations are in excess of those expected based on mass balance calculations using nh4 and br concentrations the slope sediment organic matter which is enriched in iodine from oxidationreduction processes at the oxygenated sediment water interface is responsible for this enrichment the increases in dissolved i and the i enrichments relative to nh4 and br correlate well with sedimentation rates because of differential trapping following regeneration the pore fluid i br ratios suggest that membrane ion fiitration is not a major cause of the decreases in cl concentrations other possible sources for low cl water including meteoric water clathrate dissociation and or mineral dehydration reactions imply that the diluting component of the slope low cl fluids has flowed at least 1 km through the sediment the low bottom water oxygenation in the shelf is responsible for the low if any enrichment of iodine in the shelf sediments fluctuations in bottom water oxygen concentrations in the past however may be responsible for the observed variations in the sediment ibr ratios comparison of na cl and br cl molar ratios in the pore fluids shows that the shelf high cl fluid formed from mixing with a brine that formed from seawater concentrated by twelve to nineteen times and probably was modified by halite dissolution this dense brine located below the sediment sections drilled appears to have flowed a distance 500 km through the sediment

temporal and spatial patterns of sediment deposition in the northern south china sea over the last 50 000 years abstract sediment depositional patterns along the upper continental slope of the northern south china sea scs have been studied using two sediment cores geob16601 6 20 09 07 n 116 14 38 e 1012 m water depth and geob16602 4 18 57 12 n 113 42 64 e 951 m water depth recovered during rv sonne cruise so 221 invers sediment cores were analyzed for bulk sediment element composition by x ray fluorescence xrf core scanning and clay mineral assemblage by x ray diffraction xrd the bulk sediment element and the clay mineral compositions of the two cores suggest similar depositional patterns between 50 kyr bp and 29 kyr bp and 14 kyr bp to present but a clear difference in depositional patterns during the last glacial and deglacial 29 14 kyr bp when sea level was below 90 m between 29 14 kyr bp a higher kaolinite percentage in core geob16602 4 in comparison to core geob16601 6 is interpreted to reflect a higher contribution of clay supplied by the pearl river to core site geob16602 4 in contrast core geob16601 6 received less pearl river supplied clayey material during the same period when the sea level was below 90 m during the last glacial lowstand the detrital fine grained materials supplied by the pearl river were mostly transported by coastal currents to the southwest resulting in a higher contribution of pearl river discharged material at site geob16602 4 than at site geob16601 6 we suggest that sea level induced modifications of the land ocean distribution together with changes in the palaeo physiographic conditions such as the proximity of the palaeo rivers to the individual core sites might be responsible for the different sediment depositional patterns in the study area thus the overriding control of sea level induced changes on the sediment depositional environment might mask climate related changes in sediment depositional pattern in the northern scs

the influence of humic substances on the geochemistry of iodine in nearshore and hemipelagic marine sediments iodine is characteristically enriched at the surface of hemipelagic and nearshore sediments deposited under oxygenated conditions in such sediments bulk i corg ratios usually decrease with depth to values which are characteristic of anoxic sediments reflecting a preferential release of i during early diagenesis there is some debate as to whether sedimentary i is associated with the iron oxyhydroxide phase or with the organic fraction and whether the decrease in i corg with depth is due to the dissolution of the iron oxyhydroxides or the decomposition of labile organic matter it is shown that in a surficial hemipelagic sediment sample and in a nearshore sediment core i is mainly associated with the organic fraction and moreover that humic substances are involved in the surficial iodine enrichment laboratory experiments on the uptake and release of i by and from sedimentary humic substances also suggest a mechanism whereby humic materials reduce iodate at the sediment water interface to an electrophilic i species which further reacts with the organic matter to produce iodinated organic molecules during burial this excess i could be displaced from the organic matrix by nucleophiles such as sulphide ions or thiosulphate thus providing a possible explanation for the decrease in i corg ratio with depth observed in many nearshore and hemipelagic sediments

influence of the kuroshio current intrusion on depositional environment in the northern south china sea evidence from surface sediment records the influence of the kuroshio current kc intrusion on the depositional environment of the northern south china sea scs is discussed based on multi proxies of surface sediments including planktonic foraminifera clay minerals and geochemical elements the results reveal that four typical planktonic foraminifera globigerinoides ruber g sacculifer neogloboquadrina dutertrei and pulleniatina obliquiloculata can be used to trace the kc flow route in the northern scs globigerinoides ruber is mainly distributed in shallower water than the south china sea branch of the kuroshio scsbk flow route while p obliquiloculata is mostly distributed in deeper water than the scsbk flow route there are high percentages of g sacculifer and n dutertrei at the scsbk flow route along the 1000 m isobath where bottom sediments consist of clayey silt and silty clay the scsbk also affects sediment distribution of various sources taiwan sourced sediments characterized by high illite and chlorite contents are transported southwestward into the deep sea environment by the scsbk and or deep water current the pearl river sediments characterized by high kaolinite and titanium ti contents are mostly transported southwestward to be distributed in the sea environment between the pearl river mouth and southeast of hainan island but hardly entered the abyssal basin the luzon island sediments characterized by high smectite content are generally deposited at the northwest of luzon island under the effect of an eddy west of luzon island these sediments were hardly transported northwestward onto the northern shelf of the scs throughout the scsbk flow route the sedimentary environment at the northwest of luzon island is relatively oxidized and higher in salinity than the northern scs which is probably connected with the kc intrusion through the luzon strait

active thrusting in the inner forearc of an erosive convergent margin pacific coast costa rica 1 structural and geomorphic analyses of the fila costena thrust belt in southwest costa rica indicate active thrusting within the inner forearc the fila costena exposes three major thrust faults that imbricate the late tertiary forearc basin sequence of the terraba basin the frontal thrust of the fila costena marks the boundary between an uplifting inner forearc and a subsiding outer forearc with only local uplift astride the indenting cocos ridge on the basis of surface constraints a cross section across the thrust belt suggests that all three thrusts flatten into parallelism with a low angle decollement horizon near the contact between the basement and the cover sequence of the terraba basin this decollement lies at a depth of 4 km the minimum shortening recorded by restoration of fault related folds is 17 km or 45 observations of late tertiary marine sediments tilted and faulted late quaternary fluvial terraces and raised holocene marine terraces indicate that fila costena uplift was likely initiated in the quaternary and is ongoing given that the coastal mountains are separated from the talamanca range by a valley the decollement that delaminates the forearc basin from the underthrusting forearc must continue as a flat beneath the valley but must link with the plate boundary along a crustal scale ramp system a structural geometry that has resulted in uplift of the talamanca range the highest peaks in central america the dichotomy between uplift in the inner forearc and subsidence in the outer forearc is explained in terms of the response of an arcward thickening wedge to rough subducting crust index terms 8150 tectonophysics plate boundary general 3040 8123 tectonophysics dynamics seismotectonics 8010 structural geology fractures and faults 8015 structural geology local crustal structure 8005 structural geology folds and folding

geochemistry of the surface sediments of the sulu and south china seas abstract the chemical and mineralogical composition of the surface sediments of the sulu sea a deep hydrographically restricted basin in the indonesian archipelago and the neighbouring area of the south china sea have been examined the aim of the study was to characterize the geochemistry of the sediments of the isolated oxygen deficient basin and to compare them with sediments at equivalent water depths outside the basin as a prelude to a further study of the response of the composition of the sediments to oceanographic changes including possible anoxia during the last glacial maximum the concentrations of most of the chemical constituents in the surface sediments along four transects change markedly with water depth in the sulu sea ss and the south china sea scs thus caco 3 decreases from around 60 by weight in the shallowest samples 800 1000 m to around a few percent in the deepest sample at 4203 m in the scs where the ccd lies at around 4000 m in the ss however the ccd lies much deeper so that the caco 3 contents are still approximately 40 at 4500 m depth organic c also decreases with depth in both basins from values of around 1 2 in the shallowest samples to less than 1 in the deepest samples the ratios of si mg na k co cr cu ni pb rb y zr and zn to al all decrease with increasing water depth because of the change in mineralogy and sediment texture with water depth the p al is higher in shallower water in both areas because of the higher abundance of detrital phosphorite or phosphatized limestone in these sediments the sr al ratio is also higher in shallower water reflecting the supply of aragonitic shell debris from the shallow banks and shelves around the basin the ba al ratio has a maximum at 2000 m depth in the scs due to higher primary production in overlying surface waters whereas it is uniformly low in the ss manganese is also enriched at intermediate water depths in both the ss and the scs because of the presence of oxyhydroxides and this also produces a slight enrichment in mo in the same samples because of their association in this authigenic phase the concentration of i and the i c organic ratio decreases with water depth in both areas due to the higher abundance of fresh marine organic matter at the shallow water sites which scavenges proportionally more i from sea water finally the 13 c organic values tend to decrease irregularly with increasing water depth probably reflecting a higher contribution of terrestrial organic matter in deeper water a discriminant analysis of the full data set reveals that compared with the scs samples the oxygen deficient ss sediments have higher caco 3 contents lower n and s contents and lower i c organic ba al fe al k al pb al rb al ti al v al y al and zn al ratios these contrasts are brought about by the different depths of the ccd differences in the nature of the organic matter and different types of aluminosilicate detritus in the two areas although the i c organic ratios are slightly but significantly lower in the ss which may be due to the low dissolved oxygen contents of the waters of this basin the mn and mo contents and other minor elements that respond significantly to ambient bottom water oxygen levels are not significantly different in the ss and the scs moreover the organic c contents are also indistinguishable in the two areas hence the low bottom water oxygen levels in the ss do not lead to higher organic carbon contents in the surface sediments the composition of sediments in contact with waters having even lower oxygen concentrations should be evaluated in order to conduct a more definitive test of the effect of low oxygen conditions on carbon preservation comparison of glacial interglacial sediment sections from this area must take particular care to separate the effects of source variations on those potentially caused by low oxygen levels

evaluation of elemental enrichments in surface sediments off southwestern taiwan surface slices of 20 sediment cores off south western taiwan and bed sediment of river kaoping were measured for major and trace elements al as ca cd cl cr cu fe k mg mn na ni p pb s si ti v and zn to evaluate the geochemical processes responsible for their distribution including elemental contamination major element al ratio and mean grain size indicate quartz dominated coarse grained sediments that likely derived from sedimentary rocks of taiwan and upper crust of yangtze craton bi plot of sio2 versus fe2o3 suggests the possible iron enrichment in sediments of slag dumping sites highest concentrations of cr mn p s and zn found in sediments of dumping sites support this correlation analysis shows dual associations detrital and organic car bon for cr p s and v with the latter association typical for sediments in dumping sites normalization of trace elements to al indicates high enrichment factors 2 for as cd pb and zn revealing contamination factor analysis extracted four geochemical associations with the principal factor accounted for 25 1 of the total variance and identifies the combined effects of dumped iron and steel slag induced c s fe relationship owing to authigenic precipitation of fe mn oxyhydroxides and or metal sul fides and organic matter complexation of fe mn ca cr p and v factors 2 3 and 4 reveal detrital association ti al ni pb cu and v effect of sea salt cl mg na and k and anthropogenic component as and zn carbonate link respectively in the investigated sediments

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

thorium 230 normalized particle flux and sediment focusing in the panama basin region during the last 30 000 years 1 application of the 230 th normalization method to estimate sediment burial fluxes in six cores from the eastern equatorial pacific eep reveals that bulk sediment and organic carbon fluxes display a coherent regional pattern during the holocene that is consistent with modern oceanographic conditions in contrast with estimates of bulk mass accumulation rates mars derived from core chronologies two nearby sites less than 10 km apart which have different mars show nearly identical 230 th normalized bulk fluxes focusing factors derived from the 230 th data at the foot of the carnegie ridge in the panama basin are 2 in the holocene implying that lateral sediment addition is significant in this part of the basin new geochemical data and existing literature provide evidence for a hydrothermal source of sediment in the southern part of the panama basin and for downslope transport from the top of the carnegie ridge the compilation of core records suggests that sediment focusing is spatially and temporally variable in the eep during oxygen isotope stage 2 ois 2 from 13 27 ka bp focusing appears even higher compared to the holocene at most sites similar to earlier findings in the eastern and central equatorial pacific the magnitude of the glacial increase in focusing factors however is strongly dependent on the accuracy of age models we offer two possible explanations for the increase in glacial focusing compared to the holocene the first one is that the apparent increase in lateral sediment redistribution is partly or even largely an artifact of insufficient age control in the eep while the second explanation which assumes that the observed increase is real involves enhanced deep sea tidal current flow during periods of low sea level stand

magnetic susceptibility variations and provenance of surface sediments in the south china sea magnetic susceptibility ms and grain sizes of surface sediments are measured to characterize sediment sources and their distribution in the south china sea scs distribution characteristics of ms of bulk samples msb fine grained fraction msf and coarse grained fraction msc are examined to explore the factors affecting ms values in sediment transport and deposition processes affected by dilution of quartz and carbonate abundance msc is not suitable for tracing sediment sources in the region instead msf provides a good parameter for tracking transport and deposition of complex and coarse grained sediments such as those from luzon island volcanics and from the pearl and mekong rivers which often have high msf values showing a decreasing trend with water depth on the continental shelf water depth 200 m to the west of luzon island kuroshio intrusion into the scs is the predominant factor for sediment transport after high msf volcanic materials from the luzon island are discharged into the sea sediments from the pearl river are transported southwestward under the china coastal current and then deposited between the pearl river mouth and hainan island to the southwest of taiwan island in the northeastern scs where sediments are mainly derived from taiwan island and or the yangtze river both the kuroshio intrusion and the china coastal current are significant in determining sediment transport and deposition in the south most of high msf sediments from the mekong river are transported eastward under the influence of northeastward currents in summer after entering the sea and then deposited on the northern sunda shelf c 2010 elsevier b v all rights reserved

geochemistry and mineralogy of the nw aegean sea surface sediments implications for river runoff and anthropogenic impact abstract surface sediments of the nw aegean sea were analyzed for clay mineral composition 94 samples organic c and carbonate content and major and minor elements 112 samples illite is the most abundant clay mineral followed by smectite chlorite and kaolinite clay minerals are preferentially deposited within the continental shelf and slope environment due to the prevailing cyclonic circulation and the formation of flocs in the rivers pro delta areas the spatial distribution of major lithogenic elements si al ti fe is substantially biased by the presence of relict sands located in the central eastern part of the thermaikos gulf continental shelf biogenic elements ca sr are noticeably pronounced on the northern flank of the north sporades islands organic c content and minor elements cu zn as and pb are enriched markedly over the thessaloniki bay and gulf suggesting substantial human impact deriving largely from untreated or partly treated domestic and industrial effluents the terrigenous component of the elements is preferentially contributed from the axios river zn and pb the aliakmon river cr co ni cu and as and to a lesser extent from the pinios river v co ni and cu a considerable part of the metals originates in ultra mafic and volcanic formations which are abundant in the rivers catchment basins carbonate content exhibits great variability with the highest values observed in biogenic sediments of the sporades basin in the latter area mn and fe oxides and hydroxides were found as coatings on calcite the coatings were enriched in cr co ni zn as mo and pb due to adsorption or ion exchange during early diagenesis the combined influence of the river systems the thessaloniki metropolis and the diverse sedimentological background generates great patchiness in the distribution of major and minor elements

on the sedimentological origin of down core variations of bulk sedimentary nitrogen isotope ratios 1 the bulk sedimentary nitrogen isotopic composition of two cores from nearby sites on the northern slope of the south china sea site 17940 and ocean drilling program odp site 1144 differs by up to 2 during the last glacial period given their close proximity both core sites are located in the same biogeographic zone and nutrient regime and it is thus unlikely that this offset is due to a true gradient in surface ocean conditions in an attempt to resolve this offset we have investigated the possible effects of two sedimentological parameters that can affect bulk sedimentary 15n namely the variable contribution of inorganic n to bulk n in the sediment and the grain size dependence of bulk 15n we find that neither effect singly or in combination is sufficient to explain the significant 15n offset between the two down core records by elimination the most likely explanation for the observed discrepancy is a different origin of both the organic and inorganic nitrogen at each site this study adds to the growing body of evidence highlighting the complex nature and origin of the sedimentary components in sediment drifts such as odp site 1144

sediment mixing and accumulation rates in the sulu and south china seas implications for organic carbon preservation in deep sea environments abstract recent rates of carbon burial in two deep sea basins the sulu and south china seas are contrasted to determine factors influencing organic carbon preservation in deep sea sediments the sulu sea is an oxygen deficient warm water basin whereas the adjacent south china sea is more typical of open ocean conditions high resolution sea bed profiles of 14c reveal that accumulation rates for the sulu sea are 2 3 times higher than the south china sea at any given water depth e g 1 3 g cm 2 kyr 1 versus 4 3 g cm 1 kyr 1 respectively at 3000 m higher accumulation rates for the sulu sea are attributed to higher terrigenous input and better carbonate preservation in the warmer bottom waters benthic mixing rates determined using 210pb geochronology generally are lower in the sulu sea 0 004 0 254 cm2 yr 1 as compared with the south china sea 0 17 1 57 cm2 yr 1 especially at the 3000 m and 4000 m sites in the sulu sea where benthic mixing is negligible despite the higher bottom water oxygen levels in the south china sea organic carbon concentration profiles are strikingly similar for the two basins at any given water depth with similar concentration profiles higher accumulation rates in the sulu sea result in equivalently higher carbon preservation rates as primary production is thought to be similar for both basins if anything slightly higher for the south china sea the production rate can not explain the observed differences in carbon preservation in addition benthic mixing rates apparently do not play a major role in carbon preservation as extremely low rates at the deeper sulu sea would predict relatively low carbon preservation contrary to our observations we conclude that sediment accumulation rate is the dominant control on carbon preservation in this area of the western equatorial pacific

variations in 129i 127i ratios in recent marine sediments evidence for a fossil organic component abstract the value of the pre bomb 129 i 127 i ratio in the hydrosphere is important for the use of this isotope system for dating and tracing purposes in order to determine this value and to examine spatial variability 129 i 127 i ratios were measured in 25 sediment samples from five cores taken at geographically distinct coastal areas the results indicate a pre anthropogenic 129 i 127 i ratio of 1500 10 15 in good agreement with values derived from previous sediment and groundwater studies results from shallow sediments show that the layer of bioturbation is dominated by the addition of anthropogenic 129 i the good agreement between results for this layer from different cores supports the understanding that marine iodine is isotopically homogeneous and associated with organic material which is actively remineralized at the sediment water interface lower ratios down to 354 10 15 corresponding to an age of 32 5 ma and larger variations than expected were found in sections of the cores below the layer of bioturbation these observations can be explained by the presence of refractory fossil organic material transported by rivers to the sediments from uplifted continental shales the results suggest that marine iodine is present in two forms a labile component which is isotopically homogeneous and a refractory component which is associated with kerogen or other fossil organic compounds whose 129 i 127 i ratio reflects the age of these compounds 129 i 127 i ratios can be used to identify and date fossil organic material in recent sediments the presence of which can alter the assumptions underlying models of the global carbon cycle

on the significance of sea level variations and shelf paleo morphology in governing sedimentation in the southern south china sea during the last deglaciation abstract deglacial sedimentation on the outer sunda shelf the shelf margin and slope shows a close correlation with the stages of flooding of the emerged shelf it is mainly controlled by the relationship between shelf paleo physiography and changes in sea level and sediment supply based on the sedimentological and geochemical variability at five sites along a transect across the outer shelf and the continental slope covering the last 20 000 years four intervals of significant depositional changes are identified the first reorganization in the sedimentation regime which was established during sea level lowstand is associated with the drowning of the lower course of the north sunda river between 16 5 and 14 5 ka during and following the rapid rise in sea level at 14 5 14 ka sedimentation on the slope is characterized by an accelerated decrease in the supply of terrigenous material associated with the flooding of the middle part of the paleo valley this abrupt change in sedimentation is followed by a period of gradual decrease of terrigenous supply to the slope when the surrounding plains of the river valley were flooded 14 8 5 ka the final change occurred between ca 8 5 and 6 ka when the coastline reached its modern position and modern sedimentary patterns are established this change probably marks the end of reworking by transgression given the synchroneity of sedimentological changes along the transect across the sunda shelf and into the deep sea with the environmental shifts on the central shelf sedimentation on the margin and slope appears to be mainly controlled by the interrelationship of sea level shelf paleo physiography and sediment supply moreover the records display lateral changes through time associated with stages of the deglacial transgression which mask any potential sedimentological variability due to changes in precipitation vegetation or atmospheric circulation this fact cautions the interpretation of near shore sedimentary records as unequivocal recorders of local climate change e g se asian monsoon and highlights the need to include variations in shelf physiography and sea level in future paleoceanographic studies

living deep sea benthic foraminifera from the warm and oxygen depleted environment of the sulu sea the semi enclosed oligotrophic sulu sea is characterised by warm ca 10 c and oxygen depleted 32 m from 56 samples from surface down to 5 cm the stained foraminiferal assemblages of the sulu sea comprised 285 species including 137 agglutinated and 148 calcareous species standing stock values ranged from 595 individuals 10 cm2 on the continental slope to 100 individuals 10 cm2 in the abyssal zone generally in the low productivity and low oxygen environment of the sulu sea stained assemblages are characterized by low standing stock values moderate dominance and low diversity the combination of poor rates of c org flux and low dissolved oxygen content in bottom waters are the main factors controlling the deep sea benthic fauna in the sulu sea the foraminiferal abundances in the upper bathyal zone respond to both food fluxes and oxygen concentrations most of the epifaunal oxyphilic species have their lower limit of occurrence at a water depth of approximately 2000 m dissolved oxygen 1 25 ml l in the sulu sea at constantly dysoxic 1 ml l o2 sites from the lower bathyal and abyssal zone the assemblages comprised low oxygen tolerant species and are more dependant on c org fluxes the correlations between benthic foraminiferal faunas and c org flux and dissolved oxygen values are very good with correlation coefficients of r2 0 956r2 0 956 and 0 88 respectively the living deep sea foraminiferal assemblages consisted mainly of agglutinated tests with dominant species such as lagenammina difflugiformis ammoscalaria tenuimargo various reophax species and small 70 m trochamminaceans like portatrochammina wiesneri stained individuals of the calcareous parrelloides bradyi type 2 occurred in low numbers at oxygen poor sites down to a depth of 5 cm in the sediment column the only stained calcareous infaunal species found deeper than 4000 m was valvulineria mexicana average living depth of 3 cm the general microhabitat preferences of common species were consistent with those from other studies although due to the unique combination of poor food supply and dysoxic conditions most of the infaunal species had shallower average living depths than those reported from other dysoxic locations

morphology water characteristics and sedimentation in the silled sulu sea southeast asia during 1977 rv valdivia recovered 46 cores occupied two hydrographic stations and ran eleven bathymetric profiles in the roughly rectangular sulu sea which trends northeast and covers about 250 000 km2 the sulu sea deep in the southeast is separated from the shallower palawan depression in the northwest by the northeast trending cagayan ridge the maximum sill depth between the sea and the open ocean is about 400 m and the water column is layered cutting off the deep water which is homogeneous warm 10 c and oxygen deficient 1 6 ml ml o2 from normal oceanic water the shelves are generally broad and covered with calcareous sand and gravel except in the east and southeast where they are narrow and covered with muddy sand and gravel the shelf carbonates give way to bathyal oozes and the muddy sands grade into varied silts dominated by volcanic and sedimentary debris the smooth abyssal plain of the sulu sea deep is at a depth of 4800 5000 m and northwest of it is an plain at 4000 4200 m turbidites characterize both plains the aragonite and calcite compensation depths are at about 1400 m and 4500 m respectively the turbidite beds average 5 10 cm thick with all bouma s divisions recognizable apart from a the southern turbidites station 14224 are of two types calcareous and terrigenous the calcareous turbidites characterized by shell debris including shallow water foraminifera were derived from the upper slopes flanking the broad shelves the terrigenous turbidites characterized by sedimentary and volcanic rock fragments apparently originated from the slopes off mindanao the eastern turbidites station 14233 are finer grained characterized by sedimentary rock fragments and came from the narrow muddy shelves further east off panay negros and mindanao radiocarbon dating suggests that depositional rates for the turbidite sequences ca 100 cm 1000 yr are an order of magnitude greater than the rates for bathyal oozes organic carbon contents in the surface sediments are highest between 500 m and 1200 m water depth exceeding 2 off mindanao station 14226 and reaching 1 82 on the palawan slope station 14206 the lowest contents are at the palawan shelf edge 0 11 at station 14204 where the proportion of carbonate sand is very high and in the bathyal oozes of the central sulu sea 1 where sedimentation rates are low and mineralisation of organic matter is effective contents average 1 below 4500 m in the sulu sea deep the colour of the surface sediment appears to be related to the organic carbon content olive colours above 1200 m and below 4500 m and brown colours between the surficial sediments are characterized by living shelly faunas and intense bioturbation above 150 m and by intense bioturbation and absence of a shelly fauna down to 3000 m bioturbation decreases below 3000 m and in the sulu sea deep is confined to a few zoophycos granulites and cosmorhaphe burrows the faunal changes are apparently related to bottom water oxygen concentrations

heavy metal distribution and environmental status of doon valley soils outer himalaya india doon valley is surrounded by two major river systems ganga and yamuna on either side with a water divide passing nearly across the centre of the valley and is sandwiched between two mountain ranges in the fragile ecological systems of the himalayan foothills in total 398 soil samples were collected from the valley in a grid pattern 1 sample per 2 km2 and investigated for their heavy metal cr cu ni pb and zn abundances that are environmentally sensitive comparison of the heavy metal abundances with the contamination threshold values ctv revealed that most of these elemental abundances in doon valley soils fall well within the range of the uncontaminated to slightly contaminated category in the case of cr and ni a sizeable number of samples exceeded the ctv 250 and 100 mg kg 1 respectively with an overall background value of 109 and 52 mg kg 1 respectively sites of high cr and ni mostly occur in the ganga catchment gc sector that includes even relatively undisturbed forestland the source of this contamination is attributed to geological factors which indicate contribution from the mafic volcanics of the lesser himalaya this is also consistent with the distribution pattern of mn and fe though their abundance levels are not alarming the background concentration of pb is low 22 mg kg 1 in doon valley soils however signs of gradual pb contamination are palpable in and around the centre of the dehra dun city and along the highways aluminium normalized heavy metal ratios were found to exhibit narrow variability in the case of cu ni and cr and had good correlation with al indicating their affinity and association with the clay minerals on the other hand pb and zn seem to be associated with non silicate sources

the isotopic composition of cadmium in the water column of the south china sea abstract we determined the cd isotopic composition of seawater and sinking particles collected in the deep basin of the northern south china sea scs to investigate the controlling mechanisms on the cd isotopic composition in the water column the isotopic composition in the water column decreased with depth with e 114 110 cd values e 114 110 cd 114 cd 110 cd sample 114 cd 110 cd jmc cd munster 1 10 4 ranging from 8 7 to 9 9 in the top 80 m from 4 6 to 5 5 between 100 and 150 m decreasing from 5 5 to 3 6 at depths from 150 to 1000 m and remaining at 3 4 0 5 from 1000 to 3500 m the isotopic composition and concentrations of cd observed in the deep waters of the scs are similar to the values that were previously reported in the north pacific ocean in the thermocline the variations in the cd isotopic composition and concentrations were consistent with the relative volumetric percentages of the subsurface water the intermediate water and the deep water in the water column indicating that water mixing is the dominant process determining the isotopic composition in the thermocline comparable to the isotopic composition value in the seawater of the mixed layer the e 114 110 cd in the sinking particles collected at 30 m was 9 3 0 9 because our previous studies demonstrated that the particulate cd was predominantly biogenic organic matter the comparable isotopic composition between the surface seawater and the sinking particles indicates that net biological isotopic fractionation on cd in the surface water was insignificant the result indicates that phytoplankton do not necessarily take up relatively light cd in the oceanic surface waters it is necessary to directly and systematically investigate how marine phytoplankton fractionate cd isotopes

influence of the kuroshio current intrusion on holocene environmental transformation in the south china sea numerous studies have been conducted on the evolutionary history of the kuroshio current kc and other extensions however the history of the kc intrusion into the south china sea scs through the luzon strait has been little studied here we trace the holocene developmental history of the kc intrusion and its impact on environmental transformation in the northern scs this study involved a comprehensive analysis of planktonic foraminifera clay minerals and geochemical elements of core 05e306 sediments from the northeastern scs ams c 14 dates indicated that the sedimentation rate at the core site was most rapid 1000 cm ka before similar to 6 0 ka relatively rapid similar to 65 cm ka between 6 0 and 4 6 ka and slow similar to 24 cm ka since 4 6 ka the pulleniatina minimum event pme occurred between 4 6 and 2 7 ka together with high percentages of neogloboquadrina dutertrei and globorotalia menardii planktonic foraminifera indicated that the kc intrusion experienced three significant changes at 6 0 4 6 and 2 7 ka in turn depositional environments including input of terrigenous materials and development of biogenic materials similarly underwent three important transformations at 6 0 4 1 and 3 0 ka respectively abrupt changes in sedimentary records at the study core are contemporary with records from the tropical pacific during the holocene this indicates that development of the kc intrusion and its impact on depositional environments in the scs can be correlated with tropical factors from the low latitude oceans

late pleistocene to holocene productivity changes in the western equatorial pacific sulu sea philippines from calcareous nannofossils abstract we present a new calcareous nannofossil paleoproductivity reconstruction of the southeastern margin of the sulu sea to understand how marine productivity varied through time in one of the major fishing grounds of the philippine archipelago the study is based on two sediment cores obtained from two different hydrographic locations in the western equatorial pacific region an upwelling region off zamboanga peninsula u gc12 and a non upwelling area off panay island nu gc14 covering the past 18 000 years before present b p calcareous nannofossil assemblages in the investigated areas were of low diversity and largely dominated by gephyrocapsa oceanica and florisphaera profunda followed by small placolith bearing taxa emiliania huxleyi small gephyrocapsa and reticulofenestra minuta upwelling episodes off the zamboanga peninsula were recorded several times in the past as shown by an increase in the abundance of high productivity indicator species g oceanica small gephyrocapsa e huxleyi and of bulk sediment caco3 and a concomitant decline in the total organic carbon toc the high abundance of low surface water productivity species f profunda and umbellosphaera irregularis indicates a stratified water column with a deeper nutricline probably caused by the reduced upwelling intensity this condition was corroborated by the decrease in caco3 and an increase in toc we propose that the modern day high productivity conditions off zamboanga peninsula started at 2500 years b p whereas the low productivity off panay island was recorded from 4000 years b p and persists to the present day evidence of the younger dryas yd event was recorded from 11 100 to 10 400 years b p in u gc12 synchronous to the yd event reported from other areas in the northern hemisphere and in accordance with the timing in the sulu sea as reported from previous studies in this region this event in the sulu sea is characterized by a decrease in total nannofossil abundance and estimated primary productivity together with an increase in caco3 and a decrease in toc we interpreted that dilution caused by the increase in precipitation experienced in the southeast asian region during the yd event could have led to the decline of the total calcareous nannofossils whereas the recorded increase in caco3 is attributed to the high abundance of planktonic foraminifera during this interval

129i and 36cl concentrations in waters of the eastern clear lake area california residence times and source ages of hydrothermal fluids abstract the clear lake area of northern california is the location of hot spring activity some of which is associated with the formation of au and hg deposits we measured 129 i i and 36 cl cl ratios in nine warm springs formation springs six cold springs with elevated levels of cl and i mineral springs and five springs of recent meteoric origin dating of the i in the formation waters indicated that sources of i in these waters are formations with minimum ages between 60 and 80 ma this age range is in good agreement with the ages of the franciscan complex and the great valley sequence the dominant formations in this area because the mineral waters are essentially formation waters diluted with meteoric water i in these waters is of the same origin residence times of the waters were calculated based on the build up of129i and 36cl as a consequence of the presence of u and th in the crust the residence time of the formation waters in the great valley sequence the location for most of these springs was probably not longer than 84 000 yr the concentrations found for 36cl and 129i in the mineral waters indicate that these waters have residence times of similar magnitude in formations such as the franciscan complex or the clear lake volcanics which have slightly higher levels of u and th than the great valley sequence