neutral carbohydrate geochemistry of particulate material in the central equatorial pacific abstract neutral carbohydrate compositions were determined for particulate samples from plankton net tows shallow floating sediment traps mid depth and deep moored sediment traps and sediment cores collected along a north south transect in the central equatorial pacific ocean during the u s jgofs eqpac program total neutral carbohydrate depth profiles and patterns along the transect follow essentially the same trends as bulk and organic carbon oc fluxes attenuating with depth high near the equator and decreasing poleward oc normalized total aldose tch 2 o yields along the transect and with depth do not show any consitent patterns relative to a planktonic source neutral carbohydrate compositions in sediment trap and sediment core samples reflect preferential loss of ribose and storage carbohydrates rich in glucose and preferential preservation of structural carbohydrates rich in rhamnose xylose fucose and mannose there is also evidence for an intermediately labile component rich in galactose it appears that compositional signatures of neutral carbohydrates in sediments are more dependent upon their planktonic source than on any particular diagenetic pathway relative to other types of organic matter neutral carbohydrates are better preserved in calcareous oozes from 12 s to 5 n than in red clays at 9 n based on oc normalized tch 2 o yields due to either differing sources or sorption characteristics weight per cent glucose generally decreases with increased degradation of organic material in the central equatorial pacific region based on weight per cent glucose comparisons of samples between survey i el nion and survey ii non el nino indicate that during survey i organic material in the epipelagic zone in the northern hemisphere may have undergone more degradation than organic material in the southern hemisphere

molecular and stable carbon isotopic compositions of saturated fatty acids within one sedimentary profile in the shenhu northern south china sea source implications abstract this study examined the distributions and stable carbon isotopic compositions of saturated fatty acids safas in one 300 cm long sedimentary profile which was named as site4b in shenhu northern south china sea the concentrations of total safas in sediments ranged from 1 80 to 10 16 g g g fa g dry sediment and showed an even over odd predominance in the carbon chain of c12 to c32 mostly with n c16 and n c18 being the two major components the short chain fatty acids scfas n c12 to n c18 mainly from marine microorganisms had average 13c values of 26 7 to 28 2 whereas some terrigenous sourced long chain fatty acids lcfas n c21 to n c32 had average 13c values of 29 6 to 34 1 the other lcfas n c24 n c26 n c28 average 13c values are 26 1 to 28 0 as well as n c19 and n c20 safas average 13c values are 29 1 and 29 3 respectively showed a mixed signal of carbon isotope compositions the relative bioproductivity calculation marine vs terrigenous demonstrated that most of organic carbon accumulation throughout the sedimentary profile was contributed by marine organism the high marine productivity in shenhu south china sea may be related to the hydrocarbon seepage which evidenced by diapiric structures interestingly there is a sever fluctuation of terrigenous inputs around the depth of 97 cm below the seafloor bsf probably resulting from the influence of the dansgaard oeschger events and the younger dryas event as revealed by 14c age measurements

a new mechanistic model for organic carbon fluxes in the ocean based on the quantitative association of poc with ballast minerals abstract in simulation studies of the ocean s role in the global carbon cycle predicting the depth distribution for remineralization of particulate organic carbon poc is of particular importance following sarmiento et al global biogeochemical cycles 7 1993 417 most simulation models have the power law curve of martin et al deep sea research 34 1987 267 for this purpose the martin et al curve is an empirical fit to data most of which is from shallow floating sediment traps using such a fit implies that all the information necessary for prediction is contained in the carbon flux itself so that the organic carbon flux f oc z at any depth z can be predicted from the flux of organic carbon f oc z 0 at some near surface depth z 0 here we challenge this basic premise arguing that fluxes of ballast minerals silicate and carbonate biominerals and dust determine deep water poc fluxes so that a mechanism based model of poc flux must simultaneously predict fluxes of both poc and ballast minerals this assertion is based on the empirical observation that poc fluxes are tightly linked quantitatively to fluxes of ballast minerals in the deep ocean here we develop a model structure that incorporates this observation and fit this model to us jgofs eqpac data this model structure plus the preliminary parameter estimates we have obtained can be used to explore the implications of our model in studies of the ocean carbon cycle

fatty acid composition as an indicator of the trophic position of abyssal megabenthic deposit feeders in the kuril basin of the sea of okhotsk abstract this study examines the fatty acid fa composition in eight species of deposit feeders including holothurians echiurans sipunculan polychaete and bivalve mollusc from the kuril basin of the sea of okhotsk most of the fas in the species studied have been described previously for abyssal deposit feeders but 20 2 n 12 22 4 n 8 and 22 5 n 5 were new among megabenthic invertebrates principal component analysis indicated sample separation of the deposit feeders into three groups the first group included subsurface deposit feeders and the other two consisted of surface deposit feeders all groups differed in the ratio of 20 5 n 3 to 20 4 n 6 this ratio was 0 2 0 4 in the subsurface deposit feeder molpadia musculus risso 1826 group i and 0 6 0 9 in the surface deposit feeding echiuran pseudoikedella achaeta zenkevitch 1958 and the elasipodid holothurian psychropotes raripes ludwig 1893 group ii in the second group of surface deposit feeders group iii this ratio was a little larger in the polychaete travisia sp 1 3 and was much larger 2 1 2 5 in the echiuran alomasoma nordpacificum zenkevitch 1958 the sipunculan golfingia margaritacea sars 1851 and the holothurian peniagone dubia d yakonov and savel eva in d yakonov et al 1958 unlike previous data we found that the most abundant megabenthos species in the basin are subsurface deposit feeders and two groups of surface deposit feeders

identifying the reworking and stratigraphic provenance of bones by exploring multivariate geochemical relationships with the perio spot technique abstract erosional processes often rework materials of different ages into the same sedimentary facies producing time averaged deposits such reworking is common at archaeological sites and researchers must consider the resulting time averaging effects when using natural stratigraphy to situate artifacts and remains in time at scladina cave a neandertal site in belgium we developed a method for identifying reworked facies and the stratigraphic provenance of mammal bones based on their post mortem trace element characteristics and crystallinity we collected sixty two faunal remains from throughout the site s sedimentary sequence and analyzed them for trace element concentrations and crystallinity with laser ablation inductively coupled plasma mass spectrometry and raman spectroscopy our novel approach the perio spot technique quantifies the trace element characteristics and crystallinity from the most diagenetically altered part of a bone with high spatial resolution trace element concentrations rare earth element patterns and crystallinity of perio spots correlate throughout the scladina sedimentary sequence based on stratigraphic trends in bone chemistry and crystallinity we subdivide the scladina sequence into two successive periods of early diagenesis a period of later diagenesis and a transitional period between the early and later diagenesis periods the period boundaries also correspond to major climatic fluctuations identified in the site s stratigraphy by other means e g palynology and heavy mineralogy the stratigraphic provenance of nine cave bear femora support the confinement of reworking to within each of the diagenetic periods the provenance of two indeterminate faunal remains that visually resemble the taphonomic alteration of the scladina neandertal taphonomic proxies suggest that the individual may be significantly older than previously hypothesized evaluating the temporal integrity of exhumed assemblages and the original sedimentary context of bones with our method is thus a valuable addition to archaeological analyses especially beyond the temporal range of radiocarbon dating or in contexts with very low preservation potential of organic materials

dynamics of sinking particles in northern japan trench in the western north pacific biogenic chemical components and fatty acids biomarkers abstract biogenic opal was predominant component and had strongly positive correlation with organic carbon in both traps the average atomic ratios of biogenic opal and calcium carbonate caco 3 were also large 7 1 and 11 in the shallow and deep trap respectively and the highest ratio was found in may 1995 when the biogenic opal proportion to the total particle flux and c org c inorg ratio increased concomitantly however transient switching of the biogenic opal and caco 3 ratios 0 6 and 0 8 was observed in winter 1995 which seems to be related to a warm core ring developed in the northwestern pacific downward fluxes of fatty acids as molecular markers were determined and compared with major biogenic chemical components in sinking particles as a diatom index of fatty acids the 16 1 n 7 16 0 ratio is positively related to biogenic opal contribution to the sinking particles in the shallow and deep traps 20 5 n 3 proportion was also correlated with opal content in sinking particles in the 1 km trap in addition a major source of sinking fatty acids in the western north pacific might be characterized by algal fatty acids as a diatom marker 16 1 n 7 comparing to a zooplankton fatty acid 18 1 n 9 in the central north pacific and fecal pellets and coccolithophores in the eastern north pacific respectively also pufa index a measure of polyunsaturated fatty acids contribution to the total fatty acids correlated well with chl a inventory in surface 0 50 m water these results suggest that undegraded diatomaceous fatty acids are present in sinking particles and the composition of fatty acids is useful to understand the origin of sinking organic particles

influence of oxygen on heterotrophic reworking of sedimentary lipids at the pakistan margin abstract oceanic oxygen minimum zones omzs are thought to be regions of enhanced organic carbon burial with high organic matter om quality preservation resulting from low oxygen concentrations and faunal biomass both in the water column and at the seafloor here we use the pakistan continental margin to assess the controls on om deposition and quality along a transect through the omz from water depths of 140 1850 m we sampled five sites spanning the omz during the inter and late monsoon seasons to address the role of a oxygen b the benthic fauna and c seasonality on the composition and quality of om using lipid biomarkers organic carbon concentrations were highest within the omz and lipid biomarkers revealed that om at the pakistan margin was primarily of marine origin oxygen concentrations in bottom waters played an indirect role in controlling om quality by influencing faunal community composition and biomass both in the water column and at the seafloor benthic fauna appear to influence om quality via molecular filtration of certain compounds lipid biomarkers for example foraminifera that peak in the omz core 300 m 122 individuals 10 cm 2 0 11 ml l 1 4 91 m efficiently removed polyunsaturated fatty acids from the sediments whilst at the lower omz boundary suspension feeding pennatulids 1200 m 108 individuals hm 2 0 35 ml l 1 15 62 m stripped labile lipids from the water column particulates leading to the deposition of lipid poor om in the surficial sediments low infaunal and epifaunal biomass at the fully oxygenated deep site led to the persistence of phytodetritus and subsequently labile lipids in the sediments seasonal changes in om quality and composition were noted at 140 300 and 1850 m and were attributed to both particulate fluxes and faunal feeding patterns finally lipid biomarker indices demonstrated that the om at the pakistan margin was of low quality when compared to other similar environments

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

a case of post depositional aerobic degradation of terrestrial organic matter in turbidite deposits from the madeira abyssal plain abstract a set of oxidized and unoxidized sediment intervals from the f turbidite identified in two piston cores from the madeira abyssal plain map was analyzed for calcium carbonate total organic carbon toc total nitrogen tn stable carbon composition of toc 13c toc total hydrolyzable amino acids thaa total neutral sugars tsug lignin phenols lig two different lipid biomarkers of marine phytoplankton origin and vascular plantwax n alkanes and n acids comparison shows changes for all properties depicting the effect of post depositional aerobic oxidation the oxidation process re mineralized approximately 80 of the toc and approximately 60 of the tn in the original deposit and left the residual organic matter depleted in 13c by 1 7 2 9 thaa and tsug account for 10 or less of the toc in all samples leaving approximately 90 of the toc chemically unidentified thaa tsug lig marine phytoplankton biomarkers and plantwax n acids were lost from the oxidized deposit to an extent as great as that for toc two non protein amino acids alanine and aminobutyric acid and plant wax n alkanes displayed much less degradation 9 37 and concentrated 3 3 4 8 times relative to toc by the oxidation process these observations show that both marine and terrestrial components contribute to the re mineralized toc fraction a binary mixing approach was used to model quantitatively the change in 13c toc and plantwax n alkane concentration results suggest that terrestrial organic carbon contributes approximately 15 to the toc content of the original turbidite its abundance increases approximately 2 4 times as a consequence of the oxidation process and approximately 40 and 90 of the terrestrial and marine component of toc in the original turbidite respectively was destroyed by the oxidation process although selective preservation of terrestrial relative to marine organic carbon is a well documented phenomenon in sedimentary processes this study represents the first attempt to assess the sensitivity of terrestrial organic matter to oxidative degradation in a sedimentary environment

an organic geochemical assessment of oceanographic conditions at manop site c over the past 26 000 years eleven sediment samples taken downcore and representing the past 26 kyr of deposition at manop site c 0 57 2 n 138 57 3 w were analyzed for lipid biomarker composition biomarkers of both terrestrial and marine sources of organic carbon were identified in general concentration profiles for these biomarkers and for total organic carbon toc displayed three common stratigraphic features in the time series 1 a maximum within the surface sediment mixed layer 4 ka 2 a broad minimum extending throughout the interglacial deposit and 3 a deep pronounced maximum within the glacial deposit using the biomarker records a simple binary mixing model is described that assesses the proportion of terrestrial to marine toc in these sediments best estimates from this model suggest that 20 of the toc is land derived introduced by long range eolian transport and the remainder is derived from marine productivity the direct correlation between the records for terrestrial and marine toc with depth in this core fits an interpretation that primary productivity at site c has been controlled by wind driven upwelling at least over the last glacial interglacial cycle the biomarker records place the greatest wind strength and highest primary productivity within the time frame of 18 to 22 kyr b p diagenetic effects limit our ability to ascertain directly from the biomarker records the absolute magnitude that different types of primary productivity have changed at this ocean location over the past 26 kyr

surface area control of organic carbon accumulation in continental shelf sediments the relationship between organic carbon oc and grain size found in most continental shelf sediments is here reinterpreted in terms of the surface area of the sediments cores from many north american shelf environments show downcore decreases in oc to similar refractory background concentrations if expressed relative to the surface area of the sediments this consistent concentration is 0 86 mg oc m 2 which is equivalent in concentration to a monolayer of organic matter coating all mineral surfaces a more global collection of sediment water interface samples show that this relationship is even more extensive with exceptions occurring in areas of very high riverine sediment input organic pollution or low oxygen water columns density separations indicate that organic matter is largely adsorbed to mineral grains the microtopography of surfaces was examined with n2 sorption and most surface area was found to be inside pores of 10 nm width these data lead to a hypothesis that organic matter is protected by its location inside pores too small to allow functioning of the hydrolytic enzymes necessary for organic matter decay such protection would likely work in concert with other protection mechanisms such as humification this consistent surface area correlation with oc concentration may explain control of spatial and temporal variations in oc burial rates by sedimentation rates the pore protection hypothesis provides a causal mechanism for this observed control

rapid bioturbation in equatorial pacific sediments evidence from excess 234th measurements in order to evaluate bioturbation in equatorial pacific sediments profiles of excess 234th were measured in cores collected during november and december 1992 at six abyssal sites along the jgofs equatorial pacific 140 w transect from 5 s to 9 n excess 234th half life 24 1 days was detected at all sites mean inventories ranged from a low of 0 25 dpm cm 2 at 9 n to a high of 2 6 dpm cm 2 at 2 n eddy diffusive models of the excess 234th profiles suggest that on 100 day timescales particle mixing is slow at 5 s and 2 s eddy diffusion coefficient db 0 4 cm2 year 1 faster at 0 and 2 n db 0 34 4 8 cm2 year 1 and fastest at 5 n db 4 7 11 cm2 year 1 at 9 n 234th is found almost entirely in the upper 5 mm of the seabed and db values are 0 1 cm2 year 1 db values generally increase as poc flux increases although the linear relationship r2 0 334 p 0 365 displays considerable scatter however if the only sites included in the regression are those where 234th profiles were measured in at least two core sets i e 0 2 n 5 n and 9 n the linear regression improves substantially r2 0 754 p 0 0012 these results suggest that measurements on a single core may not fully characterize the sediment mixing regime in a particular region and highlight the need for multiple samples from an individual site thorium 234 db values at 5 s 2 s and 9 n are in rough agreement with published db values calculated from the profiles of intermediate half life radioisotopes such as 210pb and 137cs in open ocean abyssal sediments however at 0 2 n and 5 n 234th db values are as much as an order of magnitude greater than published 210pb db values this phenomenon has been observed in other marine environments and may result from age dependent mixing non steady state mixing or a combination of the two processes particle mixing in cores collected at 5 s and 5 n appears to be best described as a largely eddy diffusive process however in cores collected at 2 s 0 2 n and 9 n non local mixing processes appear to affect 15 30 of the excess 234th inventory at these sites non local mixing appears to transport recently deposited material at least 3 4 cm below the sediment water interface within 100 days of its arrival at the seafloor the combination of rapid biodiffusive mixing and non local transport allows recently deposited reactive biogenic debris to be rapidly mixed into the seabed this may affect a wide range of diagenetic processes including oxygen consumption dissolution of biogenic debris and organic carbon remineralization models of early diagenesis in deep sea sediments may need to incorporate both non diffusive transport terms and rapid biodiffusive mixing of recently deposited particles

manganese coating of the tabun faunal assemblage implications for modern human behaviour in the levantine middle palaeolithic abstract during the taphonomic and archaeozoological reappraisal of garrod s material from tabun cave mount carmel israel a distinctive dark colouring of bones was observed in the level c and d assemblages based on several geochemical tests the presence of insoluble manganese oxides in those coatings was confirmed the origin of this mineral given the geological context could be attributed to the decomposition of large quantities of organic matter due to an intensive human occupation of the site in mis 5 this fact reinforces the hypothesis of the existence of a larger logistic mobility around more permanent residential sites among anatomically modern humans in the levantine middle palaeolithic which constitutes early evidence of a more complex economic behaviour

neoproterozoic peritidal phosphorite from the sete lagoas formation brazil and the precambrian phosphorus cycle the neoproterozoic sete lagoas formation ca 610 ma of the sao francisco basin brazil is a succession of siltstone limestone and phosphorite phosphorite forms part of a previously unrecognized 150 to 200 m thick unconformity bounded depositional sequence lithofacies stacking patterns indicate that deposition was punctuated by higher order fluctuations in base level that produced aggradational parasequences these shallowing upward cycles record the progradation of phosphate rich intertidal flats over shallow subtidal deposits as accommodation filled the presence of mudcracks authigenic chert nodules lack of coarse terrigenous clastics and the abundance of silt with fine abraded quartz grains suggests accumulation along an arid coastline with significant aeolian input delivery of phosphorus adsorbed on aeolian fe oxyhydr oxide and clay is interpreted as having stimulated phosphogenesis in peritidal environments lithofacies associations indicate that windblown phosphorus promoted the establishment of cyanobacterial communities along the coast which produced photosynthetic oxygen and the suboxic conditions necessary for the precipitation of authigenic carbonate fluorapatite as in other precambrian phosphatic systems nearshore oxygen oases were a prerequisite for phosphorite accumulation because redox sensitive phosphogenic processes were pushed into the sediment to concentrate phosphorus in more distal anoxic environments phosphorite could not form because these biotic and abiotic processes were suspended in the water column which cycled phosphorus in sea water rather than at the sediment water interface such shallow water phosphorite is unlike larger younger neoproterozoic phanerozoic phosphatic deposits inferred to have formed in deeper upwelling related environments the increasing size of phosphatic deposits through the latest precambrian is interpreted as reflecting the progressive ventilation of the oceans during the neoproterozoic oxygenation event and resultant expansion of phosphogenic environments into distal settings the widespread cycling of bioavailable phosphorus at the sea floor not only produced the first true phosphorite giants but may have also been an important precondition for the evolution of multicellular animals

diagenesis in prehistoric caves the use of minerals that form in situ to assess the completeness of the archaeological record an interpretation of the archaeological record in particular that of a prehistoric cave site is complicated by the diversity of depositional and post depositional processes that affect the material deposited here we propose to use the authigenic minerals that form in situ within the cave sediments to reconstruct the ancient chemical environments in the sediments this can be done by experimentally determining the conditions under which each of the authigenic minerals are stable although this information is not available to date for minerals formed in a prehistoric cave we present calculated stability field data for the relevant minerals the results clearly demonstrate the feasibility of this approach this information particularly if based on measurements of real authigenic cave minerals will facilitate an assessment of the completeness of the cave archaeological record this is particularly important for determining whether or not the distributions of archaeologically important materials such as bones teeth plant phytoliths charcoal and ash reflect their original burial distributions or were altered as a result of secondary diagenetic processes

stable carbon isotopic variation of long chain n alkanoic acids in the equatorial pacific sediments over the last 40 ma implications for expansion of c4 grassland in south america abstract the stable carbon isotope ratio 13 c values of sedimentary long chain c 20 n alkanoic acids from the equatorial pacific iodp sites u1331 1338 were measured for historical reconstruction of c 4 plant contribution from south america over the last 40 ma the values for c 30 and c 32 acids ranged between 36 9 and 25 4 suggesting that they likely originated from higher plant wax associated with c 3 dominated vegetation the molecular distribution of alkanoic acids in the sediments showed a marked change across the intertropical convergence zone itcz indicating a potential contribution from the northern hemisphere to the sediments located at 10 n in contrast the abundances of n alkanoic acids significantly decreased in the sediments at 13 c values suggest that the differences in the core locations possibly caused north and southward shifts of ca 1 0 n and ca 0 5 s from the equator respectively the corrected 13 c values of c 30 and c 32 acids did not cross the c 3 end member threshold until 1 7 ma despite the onset of c 4 plants in central south america at ca 7 ma this implies that vegetation in the low latitudes of south america was less affected by hydrological changes induced by the uplift of the andes during the late miocene

stratigraphical and palaeontological data from the early pleistocene pirro 10 site of pirro nord puglia south eastern italy the pirro nord palaeontological and archaeological locality has been the object of recent field research to investigate the fossil content of its early pleistocene vertebrate palaeocommunities and to understand the genesis of the karst network and related deposits that delivered the lithic industry representing the earliest human occupation of europe known so far spanning 1 7e1 3 ma the succession of the pirro 10 site has been described in terms of facies and fossil vertebrate content of the 37 distinguished sedimentary units su on the whole the succession is made of chemical and clastic sediments that include debris fall and alluvial deposits su are distinguished according to lithology colour discontinuities lamination fossil concentration and taphonomical parameters palaeomagnetic data and biochronological characteristics refer the pirro 10 site to the latest late villafranchian mammal age of the italian biochronological mammal scale the fossil content is quite homogenous common taxa are axis eurygonos hystrix refossa ursus etruscus canis mosbachensis together with small mammal remains mainly represented by chiroptera and the arvicolid microtus allophaiomys e x gr ruffoi a significant change in the taxonomic record occurs in

the dolomite nodules enclosing fossil marine vertebrates in the east pisco basin peru field and petrographic insights into the lagerstatte formation abstract the mio pliocene pisco formation peru is a world famous marine vertebrate lagerstatte several fossil specimens are wrapped up in dolomitic nodules some others lie in the sediment displaying dolomite only in bone cavities e g mesorostral canal and endocranium with the aim to understand whether the precipitation of the dolomitic nodules influenced the formation of the lagerstatte we collected field data on a high number of fossil vertebrates and conducted petrographic and mineralogical analyses on samples representative of the variable development of concretions our results revealed positive relationships between size completeness and articulation of skeletons and the presence of an external nodule clear evidence of chemoautotrophic communities that thrived on the carcasses is scarce microborings are often found in the cortical bone tissues together with iron oxides the former are left by microorganisms feeding on the carcass the latter are traces of former fe sulphides a product of organic matter degradation we suggest that an early burial of the skeletons was a determinant factor in the development of dolomite concretions since it allowed methanogenesis and anaerobic sulphate reduction exploiting the lipids in the bones and the organic matter dispersed in the sediments dolomite precipitation was driven by the same bacteria operating during the suphophilic stage of whale fall communities textural observations imply that dolomite precipitated shortly after the burial of carcasses the increase of alkalinity generated by sulphate reduction and methanogenesis caused a rapid precipitation of the dolomite within skeletal cavities and prevented the degradation of the bones and diagenetic compression of skeletons the nodules themselves prevented erosion of fossils after exhumation therefore nodule formation had a crucial role in the development of the pisco lagerstatte

stereochemical studies of acyclic isoprenoids xii lipids of methanogenic bacteria and possible contributions to sediments abstract abundant volatile lipids of methanobacterium thermoautotrophicum and methanosarcina barkeri include isoprenoid hydrocarbons c30 and c15 c20 and c25 isoprenoid alcohols m barkeri contains 2 6 10 15 19 pentamethyleicosane whose relative stereochemistry is the same as found in marine sediments indicating that it is a marker of methanogenic activity the c20 c30 and c25 alkenes in m thermoautotrophicum also have a preferred sterochemistry the latter have the 2 6 10 14 18 pentamethyleicosanyl skeleton suggesting that the alkane in marine sediments may derive from methanogens the stereochemistry of squalane in a marine sediment is also compatible with an origin in methanogens in contrast the stereochemistry of pristane in m thermoautotrophicum indicates a fossil fuel contaminant origin suggesting that this and certain other alkanes reported in archaebacteria might also be of contaminant origin there is therefore little evidence at present that the pristane in immature marine sediments originates in methanogens the c15 and c20 saturated alcohols in m thermoautotrophicum have mainly the all r configuration if this is generally true for methanogens the c20 alcohol in the messel shale may originate mainly from methanogens whereas that in the green river shale may originate mainly from photosynthetic organisms

the composition and geochemical significance of organic matters in surface sediments from the southwest sub basin of the south china sea abstract information about ocean evolution and material energy exchange between the ocean and surrounding continents can be preserved in marine sediments the southwest sub basin located among the xisha islands the zhongsha islands and the nansha islands is an ideal tectonic unit to analyze the sedimentary environments of the south china sea in this paper the distribution patterns of lipid biomarkers and their compound specific stable carbon isotopes in surface sediments from the southwest sub basin of the south china sea were analyzed lipid biomarkers are composed of different proportions of aliphatic hydrocarbons carboxylic acids alcohols and series of sterols indicating that the organic matter of the southwest sub basin was derived from marine bacteria algae and terrestrial higher plants the average concentration of total organic carbon toc in the study samples was 0 5 0 16 toc total n alkanes and total carboxylic acids tfa decreased gradually from the margins to the center of the sub basin whereas the content of total n alkanols increased the spatial distribution trends resulted from varying water depths and the contribution of terrestrial organic matter the concentration of tfa and the tfa toc revealed that the accumulation of organic matter in this area was generally low the strong correlation between toc and tfa of surface sediments in the study area may be related to a balance between the ocean production and ocean deposition rates

multiple episodes of dolomitization and dolomite recrystallization during shallow burial in upper jurassic shelf carbonates eastern swabian alb southern germany abstract the upper jurassic of the eastern swabian alb is composed of oolitic platform sands with associated microbe siliceous sponge mounds at the platform margins they are surrounded by argillaceous or calcareous mudstones and marl limestone alternations deposited in adjacent marl basins partial to complete dolomitization is predominantly confined to the mound facies six types of dolomite as well as one type of ankerite document a complex diagenetic history during shallow burial with multiple episodes of dolomite formation and recrystallization the earliest massive matrix dolomitization is ca rich has slightly depleted oxygen isotope values relative to late jurassic seawater and carbon isotopic values in equilibrium with late jurassic seawater this initial massive matrix dolomitization occurred during latest jurassic to earliest cretaceous and is related to pressure dissolution during very shallow burial at temperatures of at least 50 c hydrologic conditions and mass balance calculations indicate that burial compaction provided sufficient fluids for dolomitization mg is derived from negligibly modified seawater that was expelled from the adjacent off reef strata into the mound facies position of the mounds along the platform margins controlled the distribution of the shallow burial dolomite covariant trends between textural modification increasing stoichiometry partial changes in trace element content mn fe sr and depletion in stable isotopes as well as distinctive cl pattern illustrate two recrystallization phases of the precursor matrix dolomite during further burial at elevated temperatures strong sr enrichment of the second phase of recrystallized dolomite is ascribed to sr rich meteoric waters descending from overlying aragonite bearing reef limestones or evaporite bearing peritidal carbonates late stage coarsely crystalline dolomite cements occur as vug and fracture fillings and formed during burial ankerite associated with sulphide and sulphate minerals and saddle dolomite are assumed to have formed from hydrothermal waters that moved to higher stratigraphic levels along fracture conduit systems that developed during late cretaceous to tertiary alpine orogenesis

organic matter diagenesis in shallow water carbonate sediments muddy carbonate deposits near the dry tortugas florida are characterized by high organic carbon remineralization rates however approximately half of the total sedimentary organic matter potentially supporting remineralization is occluded in caco3 minerals intracrystalline while a portion of nonintracrystalline organic matter appears to cycle rapidly intracrystalline organic matter has an approximately constant concentration with depth suggesting that as long as its protective mineral matrix is intact it is not readily remineralized organic matter in excess of intracrystalline organic matter that is preserved may have a variety of mineral associations e g intercrystalline adsorbed or detrital in surface sediment aspartic acid contributed 22 mole and 50 mole to nonintracrystalline and intracrystalline pools respectively in deeper sediment 1 6 1 7m the composition of hydrolyzable amino acids in both pools was similar aspartic acid 40 mole like amino acids intracrystalline and nonintracrystalline fatty acids have different compositions in surface sediments but are indistinguishable at depth these data suggest that preserved organic matter in the nonintracrystalline pool is stabilized by its interactions with caco3 neutral lipids are present in very low abundances in the intracrystalline pool and are extensively degraded in both the intracrystalline and nonintracrystalline pools suggesting that mineral interactions do not protect these compounds from degradation the presence of chlorophyll a but absence of phytol in the intracrystalline lipid pool demonstrates that chloropigments are present only in the nonintracrystalline pool sedimentary chloropigments decrease with depth at similar rates in dry tortugas sediments as found in alumino silicate sediments from the long island sound suggesting that chloropigment degradation is largely unaffected by mineral interactions overall however inclusion and protection of organic matter by biominerals is a major pathway for organic matter preservation in this low organic carbon biomineral rich regime

dinoflagellate origin for sedimentary 4α methylsteroids and 5α h stanols biological marker compounds provide useful tools for evaluating the depositional environments of recent and ancient sediments and petroleums1 largely through established relationships between the organic matter of sediments and source organisms1 2 such relationships are best tested and explored by investigating the lipid components of natural populations of autochthonous biota that can be clearly recognized as contributors to underlying bottom sediments in this context we have studied the lipids of the freshwater dinoflagellate peridinlum lomnickii woloszynska order peridiniales class dinophyceae collected from the waters of priest pot3 a eutrophic lake in the english lake district its distributions of both 4 methylsterols and 4 methylstanones closely resemble those of the underlying bottom sediments demonstrating that dinoflagellates are important contributors of these sedimentary compounds the 4 methylsteroidal hydrocarbons found in ancient sediments and petroleums4 6 are presumably diagenetic products of such 4 methylsteroids and therefore reflect dino flagellate inputs to the original depositional environments furthermore the prominence of 5 h cholestan 3 ol in p lomnickii suggests that dinoflagellates may be the long sought direct biological source of sedimentary 5 h stanols

lipid biomarker fluxes in the arabian sea with a comparison to the equatorial pacific ocean abstract fluxes and distributions of organic carbon oc and lipid biomarkers were measured in the western arabian sea as a function of season depth and distance from the coast of oman during the us jgofs arabian sea process study in 1994 1995 a strong seasonal pattern in oc and lipid flux is related to the annual monsoon cycle in the western arabian sea with the highest fluxes measured during the southwest monsoon fluxes were greatly attenuated with depth in the water column and in surface sediments as remineralization effectively consumed particulate organic matter a comparison of water column fluxes with oc and lipid accumulation rates in sediments confirms that the water sediment interface is a hot spot for organic matter degradation biomarker compositions also varied seasonally and with distance offshore reflecting seasonal and spatial succession of their biological sources and their subsequent export through the water column degradation of oc and biomarkers was extremely efficient with only a tiny fraction

diagenesis of amino compounds in water column and sediment of lake baikal abstract the diagenesis of amino compounds in lake baikal was studied in sediment trap material 18 different water depths between 50 1350 m and underlying sediment 0 40 cm total hydrolysable amino acids thaa the amino acid aa composition including d and l enantiomers and amino sugars were analyzed the study provides information on early diagenesis d aa preferentially accumulated over proteinaceous l aa molar ratios of glucosamine and galactosamine decreased towards a ratio of 1 0 0 1 in the sediment similar to ratios previously reported for detrital marine organic material the general pattern of amino compound diagenesis in lake baikal resembles the pattern observed in marine systems indicating a universal character of the processes controlling diagenesis in aquatic environments

phytodetritus at the abyssal seafloor across 10 of latitude in the central equatorial pacific fresh phytoplankton detritus or phytodetritus has been reported from numerous deep seafloor sites in the temperate north atlantic and pacific oceans following seasonal phytoplankton blooms here we report the first strong evidence for abyssal accumulations of phytodetritus in the tropics in the central equatorial pacific in november december 1992 we obtained photographs and or sediment core samples from 61 abyssal stations water depths of 4280 5012 m between 12 s and 9 n along 140 w greenish flocculent material was recovered from the top of multiple core samples from 5 s to 5 n this material was most abundant from 2 s to 2 n in some areas forming continuous layers at least 5 mm thick and individual aggregates 1 cm in diameter the greenish material was clearly visible in bottom photographs as a green veneer that covered 95 of the seafloor near the equator and as individual cm scale aggregates covering 1 of the seafloor occasionally thick accumulations of cm scale aggregates occurred in biogenic pits cleared trails and feeding traces suggest that surface deposit feeding holothurians and echiurans grazed the greenish material microscopic examination of greenish material recovered from core tops and a burrow lumen revealed relatively intact diatoms including rhizosolenia sp and other microalgae with chloroplasts containing chlorophyll the greenish material was 1 12 5 organic carbon by weight i e 5 39 times richer than associated seafloor sediments it also contained high excess activities of 234th suggesting arrival from the water column in the previous 100 days samples of the greenish flocculent material from 0 and 5 n incubated at simulated environmental pressure and temperature with 14c labeled glutamate exhibited 5 fold higher rates of microbial activity than underlying sediments or brown floc from 9 n surface sediment samples which included the greenish flocculent material from 5 s to 5 n also contained significant concentrations of chlorophyll a and other chloropigments the chloropigment concentrations were roughly comparable to deep sea phytodetritus collected in the north atlantic we conclude that fresh organic rich phytodetritus was present on the seafloor from 5 s to 5 n along 140 w in november december 1992 with highest concentrations within 2 3 of the equator this material is likely to be a concentrated high quality food resource for deep sea microbes and metazoans we estimate an upper limit for the standing stock of this phytodetritus to be 2 6 mmol corg m2 this corresponds to 3 of the annual flux of organic carbon to the seafloor at these latitudes in 1992 because the degradation rate of this material appears to be very high its presence at the seafloor for several months per year could yield significant phytodetrital contributions to the annual seafloor organic carbon budget we also suggest that the phytodetrital aggregates are formed at intense convergence zones resulting from seasonal passage of tropical instability waves within 5 of the equator if so phytodetrital accumulations are likely to recur seasonally over broad areas of the abyssal equatorial pacific

factors controlling 13c contents of sedimentary organic compounds principles and evidence the carbon isotopic composition of any naturally synthesized organic compound depends on 1 the carbon source utilized 2 isotope effects associated with assimilation of carbon by the producing organism 3 isotope effects associated with metabolism and biosynthesis and 4 cellular carbon budgets these factors are reviewed and quantitative considerations summarized particularly with regard to active and passive modes of carbon assimilation by phytoplankton and the existence of discernible regularities in isotope effects associated with lipid biosynthesis it is concluded that n alkyl lipids are in general depleted in 13c by about 1 5 relative to polyisoprenoid lipids produced by the same organism the effects of biological reworking on isotopic compositions of organic carbon are examined and it is suggested that enrichment of 13c in sedimentary organic carbon may result from loss of ch4 from zooplanktonic gut communities isotopic methods for estimation of ancient co2 levels are considered and a hyperbolic form favored for the relationship between concentrations of dissolved co2 and isotopic fractionation

lipid rich ascending particles from the hydrothermal plume at endeavour segment juan de fuca ridge abstract samples of ascending and descending particulate matter from the hydrothermal plume at endeavour segment of the juan de fuca ridge were analyzed for their lipid composition to investigate the biogeochemistry of particulate matter associated with oceanic hydrothermal processes the ascending flux of lipid was up to six fold greater than the descending flux and ascending particles were significantly enriched up to 200 fold in lipid compared with descending particles the dominant fatty acids in both ascending and descending particles were c16 1 c18 1 9 c20 1 and c22 1 and the major neutral lipids were c20 1 and c22 1 fatty alcohols and cholesterol c20 1 and c22 1 alcohols constituted up to 70 of neutral lipids in ascending particles at sites directly influenced by the plume compared to 54 at the background site and 35 to 54 in descending particles comparison with zooplankton collected above the plume suggested that a large fraction of this lipid was derived from zooplankton that may be opportunistically feeding on organic matter associated with the plume the high flux of lipid moving upward in the water column in the vicinity of the vent plume is roughly equivalent to downward fluxes at similar oceanic depths and suggests an important mechanism by which particulate lipids may be dispersed in the marine water column

a three dimensional time dependent approach to calibrating sediment trap fluxes we conducted an experiment to test explicitly the accuracy of upper ocean sediment trap fluxes using the particle reactive radionuclide 234th t1 2 24 1 days two independent vertex style multitrap arrays were used for collection of sinking particles at 95 m and 97 m depths over a four day period in may 1992 at the u s joint global ocean flux study bermuda atlantic time series study bats site samples for total 234th were collected every 8 m between the surface and 96 m and immediately combined for analysis to obtain the vertically integrated activity of 234th we collected a total of 27 samples over the four day period the234th samples were collected daily at each of the two traps and every other day on a 6 6 km grid to characterize the entire source region for particles collected in the traps in situ flow sensors at one trap array indicated low horizontal shear at the trap mouth 5 10 cm s compared to normal values at bats the predicted 234th flux from the watercolumn profiles was not significantly different from zero 30 140 disintegrations per minute m2 d the measured trap 234th flux at both arrays was significantly higher 290 15 dpm m2 d we hypothesize that upper ocean traps at bermuda may overcollect during low flux periods and undercollect during high flux periods thus recording a biased signal of the true particle flux

climate induced variations in productivity and planktonic ecosystem structure from the younger dryas to holocene in the cariaco basin venezuela a high resolution molecular organic geochemical study of sediments in the anoxic cariaco basin indicates significant changes in primary productivity and planktonic community structure associated with the transition from the younger dryas to the holocene variations in climate conditions over the past 12 14c kyr have induced large scale changes in upwelling intensity which directly affected levels of primary productivity as reflected in accumulation rates of bulk productivity proxies concentrations and accumulation rates of sterol and alkenone biomarkers have been used to identify how productivity changes affected the structure of the planktonic ecosystem a shift in the dominant primary producer from diatoms younger dryas to coccolithophores holocene is identified if productivity and ecosystem variations like those identified in the tropical upwelling zone of the cariaco basin region occur throughout the tropical oceans they have the potential to affect global climate through perturbations in the biogeochemical cycle of carbon

archaeal lipids record paleosalinity in hypersaline systems abstract we present an ecologically based biomarker method for estimating past salinity especially in hypersaline conditions the relative amounts of acyclic diether and tetraether membrane lipids synthesized by archaea correlate with salinity from 0 250 practical salinity units psu in modern settings we examined the preservation of this lipid biomarker salinity relationship in ancient sedimentary organic matter using samples from two sequences of marls and diatomites deposited just prior to the messinian salinity crisis salinity estimates were consistent with expected absolute salinity as well as the amplitude of variations leading up to the messinian salinity crisis this lipid biomarker approach to salinity reconstruction complements existing paleosalinity proxies because i archaea survive and thrive over a broad salinity range well beyond that of haptophyte algae and other plankton which form the microfossil record and ii it provides fine salinity resolution for the wide range broadly defined as hypersaline with the proxy there is the potential to provide novel insights into salinity variation within desiccating basins in climatically sensitive seas e g dead sea permian delaware basin evolution of brines timing of onset of hypersaline conditions and evaporite deposition

factors controlling the flux of organic carbon to the bathypelagic zone of the ocean 1 particle fluxes measured with time series sediment traps deployed below 2000 m at 68 sites in the world ocean are combined with satellite derived estimates of export production from the overlying water to assess the factors affecting the transfer of particulate organic matter from surface to deep water multiple linear regression is used to derive an algorithm suggesting that the transfer efficiency of organic carbon defined as the settling flux of organic carbon normalized to export production increases with the flux of carbonate and decreases with water depth and seasonality the algorithm predicts 80 of the organic carbon transfer efficiency variability in diverse oceanic regions the influence of the carbonate flux suggests that the ballasting effect of this biogenic mineral may be an important factor promoting export of organic carbon to the deep sea by increasing the density of settling particles however the lack of a similar effect for biogenic opal suggests that factors other than particle density also play a role the adverse effect of increasing seasonality on the transfer efficiency of carbon to the deep sea is tentatively attributed to greater biodegradability of organic matter exported during bloom events in high latitude opal dominated regions with high f ratios and seasonality while a higher fraction of net production is exported a higher fraction of the exported organic matter is remineralized before reaching bathypelagic depths on the other hand in warm low latitude carbonate dominated regions with low f ratios and seasonality a higher fraction of the exported organic matter sinks to the deep sea

reconstructing the phytoplankton community of the cariaco basin during the younger dryas cold event using chlorin steryl esters 1 a record of the downcore distribution of chlorin steryl esters cses through the younger dryas was produced from cariaco basin sediments in order to assess the potential use of cses as recorders of the structure of phytoplankton communities through time using an improved high performance liquid chromatography method for the separation of cses we find significant changes in the distribution of cses during the younger dryas in the cariaco basin during the younger dryas enhanced upwelling in the cariaco basin caused an increase in the diatom population and therefore an increase in the relative abundance of cses derived from diatoms in contrast the dinoflagellate population and therefore cses derived from dinoflagellates decreased in response to the climate change during the younger dryas these community shifts agree well with the shifts observed in the present day on a seasonal basis that result from the north south migration of the intertropical convergence zone over the cariaco basin we also identify changes in the abundance of several cses that seem to reflect rapid warming and cooling events this study suggests that cses are useful proxies for reconstructing phytoplankton communities and paleoenvironments index terms 1055 geochemistry organic geochemistry 4267 oceanography general paleoceanography 4855 oceanography biological and chemical plankton keywords younger dryas cariaco basin chlorin steryl esters

formation of saddle dolomites in upper cambrian carbonates western tarim basin northwest china implications for fault related fluid flow abstract the saddle dolomites occur more intensely in cores closely to fault than that in cores far away from the fault in upper cambrian carbonate of western tarim basin suggesting that formation of the saddle dolomites is likely related to fault controlled fluid flow they partially fill in fractures and vugs of replacement dolomite the saddle dolomites exhibit complex internal textures commonly consisting of core and cortex in comparison with the matrix dolomites the saddle dolomites show lower sr content and 87 sr 86 sr ratios higher fe and mn content and more negative 18 o values combined with high th 100 130 c of primary fluid inclusions it is suggested that the saddle dolomites precipitated from hydrothermal fluid derived from the deep evaporite bearing middle cambrian strata and the magnesium source may be due to dissolution of host dolomite during hydrothermal fluid migration fault activity resulted in petrographic and geochemical difference of the core and cortex of the saddle dolomites the cores precipitated from the formation water mixed by deep brines at the early stage of fault activity and the cortexes precipitated from the deep fluid with higher temperatures through the middle cambrian later in summary the formation of the saddle dolomites implies a hydrothermal fluid event related to fault activity which also resulted in high porosity in upper cambrian carbonate in western tarim basin

bat guano and preservation of archaeological remains in cave sites the formation of authigenic minerals in cave sediments can be used to reconstruct the paleochemical conditions that prevailed in the past and in this way to assess the completeness of the archaeological record previous studies indicated that the major driving mechanisms for chemical diagenesis in prehistoric caves that result in the formation of authigenic minerals are the degradation of bat guano and the local hydrology we therefore investigated contemporary bat guano deposits in caves and the sediments directly below such deposits the emerging patterns show that the formation of authigenic minerals occurs under acidic conditions within tens of years the availability of phosphate al k and fe increases with increasing organic matter degradation while the availability of nitrogen and sulfur decreases insectivorous bat guano contains larger amounts of phosphate and is more acidic than fruit bat guano in the first stages of diagenesis micro chemical environments form within the degrading bat guano that result in the formation of a wide variety of authigenic minerals during advanced stages of diagenesis steady state conditions are achieved resulting in authigenic mineral assemblages being dominated by one mineral type at the same locale this is reminiscent of known distributions of authigenic minerals in prehistoric cave sediments under the acidic conditions produced by degrading bat guano deposits calcareous artifacts and bones are not expected to persist for long periods of time unless there is a lot of calcite in the sediments that could buffer the sediment water ph guano itself is not likely to be preserved periods of cave abandonment can be inferred from the presence of authigenic minerals in the sediments as it is during these times that bats mainly occupy the cave the occurrence of certain authigenic minerals in open air sites may serve as evidence for areas rich in organic matter containing phosphate i e animal enclosures latrines sewers trash pits and or bones as the degradation process is rapid the use of authigenic minerals to identify these loci is relevant to almost all archaeological as well as historical sites

biogeochemical significance of fatty acid distribution in the coastal upwelling ecosystem off concepcion 36 s chile abstract the distribution of fatty acids fas in the water column and surface sediment of the coastal upwelling ecosystem off concepcion central chile almost monthly from february 2007 to november 2008 was analyzed using gas chromatography mass spectrometry the concentration of fas in the water column ranged from 3 4 to 67 7 g l 1 and showed higher values in surface water than in bottom water and under upwelling vs non upwelling conditions the content in surface sediment ranged from 21 6 to 328 5 g g dw 1 and had a higher abundance in february 2007 and january march and june 2008 in surface water 16 0 18 0 and 16 1n 7 made up ca 47 of the fas during the study period while in bottom water 16 0 18 0 and 18 1n 9 accounted for ca 45 and in surface sediment ca 43 was accounted for by 14 0 16 0 16 1n 7 and 18 1n 7 fas seasonal variability in the relative abundance of saturated and polyunsaturated fas pufas was observed in surface water while in bottom water and surface sediment no major temporal change in fa composition was observed a negative exponential relationship between bacterial fas and pufas from surface water and sediment suggests that bacteria may be responsible for ca 80 of pufa removal during sinking we suggest that the fa composition of the surface sediment of the ocean is a consequence of rapid alteration of the fa pool by biological activity in the water column and sediment driven by the removal of the labile fraction of fas

the importance of atmospheric input of terrestrial organic material to deep sea sediments the concentrations of lipids were determined in atmospheric particle gas and rain samples collected from the tropical north pacific to assess lipid sources transport mechanisms and fluxes to the ocean surface four lipid compound classes aliphatic hydrocarbons fatty alcohols fatty acid esters and salts all unequivocally show a terrestrial vascular plant source these aerosol lipids originate from wind erosion of asian and american soils and direct emission from vegetation the major fluxes result from rain rather than dry deposition these fluxes are large enough to have a major potential impact on the inventory of terrestrially derived lipid material found in deep sea sediments this has been showm for n alkanes fatty alcohols fatty acids total lipids and for organic carbon by comparing atmospheric and sediment trap fluxes with sediment accumulation rates it is suggested that some biogenic terrestrial material is more protected from degradation than marine derived material

understanding the causes and consequences of past marine carbon cycling variability through models abstract on geological time scales the production and degree of recycling of biogenic carbon in the marine realm and ultimately its removal to sediments exerts a dominant control on atmospheric co 2 and hence variability in climate this is a highly complex system involving a myriad of inter connected biological chemical and physical processes for this reason alone linking observations often highly abstracted in the form of proxies to the primary processes involved and ultimately to explanatory hypotheses for specific geological events and transitions is challenging the past few decades have seen a progressive improvement in theoretical and process based understanding of the various components that make up the marine carbon cycle and hand in hand with this the development of numerical model representations of the complete system models have also been designed and or adapted with paleoclimate questions in mind and applied to quantitatively explore the role of the marine carbon cycle in both perturbations and long term geologic evolutionary trends in global climate and possible feedbacks between them however we must ask whether paleoclimate models incorporate sufficiently appropriate representations of the dynamics and sensitivities of the marine carbon cycle and indeed whether in the geological context we really know what these dynamics are here we provide a comprehensive overview of how marine carbon cycling and the biological carbon pump is treated in available paleoclimate models with the aim of critically evaluating their ability to help interpret past marine carbon cycle and climate dynamics to this end we first provide an overview of commonly used paleoclimate models and some of their associated paleo applications drawing from a wide range of global carbon cycle box models and earth system models of intermediate complexity emics secondly we review and evaluate the three dominant processes involved in the cycling of organic and inorganic carbon in the marine system and how they are represented in models namely biological productivity at the ocean surface remineralisation dissolution of particulate carbon within the water column and the benthic pelagic coupling at the seafloor we generate and employ illustrative examples using the model genie to show how different parameterisations of water column and sediment processes can lead to significantly different model projections our compilation reveals the prevalence of static parameterisations of marine carbon cycling among existing paleoclimate models which are commonly empirically derived from present day observations although such approaches tend to represent carbon transfer in the modern ocean well they are potentially compromised in their ability to reflect the true degree of freedom and strength of feedbacks with respect to past climate events particularly those characterised by environmental boundary conditions that differ fundamentally from today finally we discuss the importance of using models of different complexities and how questions of model uncertainty may start to be addressed

deciphering bone depositional sequences in caves through the study of manganese coatings the presence of black coloured bones in caves has been sometimes associated to the use of fire by humans but more frequently the agent responsible for black colour is the natural deposition of manganese oxides manganese coatings were not usually studied once human action was discarded however they can provide valuable information about the origin and the sequence of formation of a palaeontological or archaeological deposit in this paper we present a quantitative and qualitative study of the manganese coatings that affect most of the bones recovered in the palaeontological site of linares cave nw of iberian peninsula together with other taphonomic marks the manganese coatings are superimposed on other features previously existing on the surface of the bones in turn the coatings can be affected by other agents that modified them totally or partially the combined interpretation of the different taphonomic marks provides us with valuable information on the sequence where the different taphonomic processes were produced as for example the intervention of carnivores in the disarticulation of some elements before the burial the preservation of anatomic connections until after the burial of the carcasses and the existence of reworking processes in some parts of the infill

analysis of zooarchaelogical and taphonomical variability from maripe cave site santa cruz province argentinian patagonia abstract this paper compares two zooarchaeological sub samples each of which comes from a different area north chamber and south chamber of maripe cave site santa cruz argentina in previous papers each chamber was interpreted as a particular microenvironment based on their specific environmental and geoarchaeological features in both areas hunting gatherer society occupations were recorded since the pleistocene holocene transition to late holocene this paper investigated and discussed the different agents and processes involved in the formation of each assemblage with the aim of assessing the taphonomic variability between the two areas and discussing their integrity bone specimens of lama guanicoe guanaco the most common species on the site were analyzed the bone surfaces of specimens were studied by naked eye observations and binocular magnifying to 10 which allowed recognition of different patterns of modification the representation of guanaco anatomical units was also discussed at each chamber according to economic utility and bmd values the results indicate that while there was involvement of different natural agents and processes acted differently in each sector the main accumulating agent in both sets was human differences between both chambers are observed in the representation of anatomical units in processing marks in the conservation of specimens and in the number and intensity performed by each natural agents and process in each sector each chamber indicates a different taphonomic history the north chamber records greater conservation and archaeological integrity while the south chamber shows a more complex taphonomy

geoarchaeology and taphonomy deciphering site formation processes for late holocene archaeological settings in the eastern pampa patagonian transition argentina abstract assessing the integrity and resolution of archaeological sites in sandy environments is a key issue for understanding site formation processes in hunter gatherer s contexts a case study from the lower course of the colorado river at the eastern pampa patagonian transition argentina is presented here the studied area is characterized by a sand dune relief that is superimposed upon ancient fluvial and marine environments the sites date to between c 2000 and 250 14c yr bp late holocene and they are mostly located in eolian contexts the objective of this paper is to understand environmental dynamics and the site formation processes that operated in archaeological sites of the late holocene through the integration of geoarchaeological and taphonomic information the obtained results allowed the identification of site formation processes related to the different environmental settings coast ancient delta and inland however general patterns that relate some taphonomic effects as root action and weathering with landscape processes such as pedogenesis at an areal scale were also recognized despite the varied and highly dynamic environmental conditions of this arid semiarid area archaeological contexts with good degrees of resolution and integrity were recognized

thermal alteration of buried bone abstract burned bone is a common component of archaeological deposits traditionally associated with cremations culinary activities waste disposal fuel use and a by product of naturally occurring fires such interpretations assume responsible agents act upon bone prior to deposition or burial this sequential relationship between heating and burial is challenged by the suggestion that post burial alteration of bone is not only possible but can serve to explain the condition of burned material recovered in certain situations exposure to heat following burial incorporates several additional variables the sediment in which bone is deposited duration of exposure to a heat source and the interval between burial and burning affect the degree and extent of thermal alteration experiments have been conducted to test the hypotheses and parameters surrounding subsurface i e post burial alteration by surface fires

234th in different size classes of sediment trap collected particles from the northwestern pacific ocean abstract 234 th a surface area specific particle reactive radionuclide has been used to estimate particulate organic carbon poc export fluxes based on the poc 234 th ratio of sinking particles and the 234 th flux in the ocean the poc 234 th ratios from large particles 50 m are conventionally considered to represent sinking particles collected by sediment traps but this assumption has not been thoroughly tested more recently hung and gong 2010 separated sinking particles from the northern south china sea where diatoms are the most dominant group using different nitex screens and found that small 234 th and poc flux however the size distribution of sinking particles has seldom been measured in picoplankton dominated oligotrophic and upwelling conditions here we used nitex screens to separate sinking particles in oligotrophic and upwelling regions additionally images of selected bulk sinking particles not subject to sequential filtration were directly taken by scanning electron microscopy sem to determine the size distribution of sinking particles within the trap collected 234 th pool in the upwelling area the 1 10 and 10 50 m fractions had on average the highest amounts of 234 th while poc did not show significant variations among the different size fractions in the oligotrophic region the 10 50 and 1 10 m fractions had on average the highest amounts of 234 th while the 150 and 10 50 m had elevated shares of poc results thus demonstrate that 234 th was mainly carried by the smaller 234 th flux can be a major fraction of the total sinking flux of this isotope and thus particles smaller than 50 m cannot be ignored because the poc 234 th ratio that is often used is that of large 50 m particles obtained from pump systems not traps

initial micromorphological results from liang bua flores indonesia site formation processes and hominin activities at the type locality of homo floresiensis liang bua a karstic cave located on the island of flores in eastern indonesia is best known for yielding the holotype of the diminutive hominin homo floresiensis from late pleistocene sediments modern human remains have also been recovered from the holocene deposits and abundant archaeological and faunal remains occur throughout the sequence the cave the catchment in which it is located and the gross aggradational phases of the sediment sequence have all been subject to a great deal of scientific scrutiny since the discovery of the holotype of h floresiensis in 2003 a recent program of geoarchaeological research has extended analyses of the site s deposits to the microstratigraphic micromorphological level the stratigraphic sequence in the cave is well defined but complex comprising interstratified sediments of diverse lithologies and polygenetic origins including volcanic tephras fine grained colluvium coarse autogenic limestone gravels speleothems and anthropogenic sediments such as combustion features the sedimentological and chemical heterogeneity suggest that processes of site formation and diagenesis varied markedly through time both laterally and vertically we present initial results from samples collected in 2014 from an excavation area near the rear of the cave which yielded radiocarbon ages from charcoal that fill an important temporal gap in the chrono stratigraphic sequence of previously excavated areas of the site the results indicate marked changes in site environment and hominin activity during the late pleistocene relating primarily to the degree to which the cave was connected to the hydrogeological system and to the varying intensities of use of the cave by hominins importantly we identify anthropogenic signs of fire use at the site between 41 and 24 thousand years ago most likely related to the presence of modern humans

a methodological approach for identifying archaeological evidence of fire resulting from human activities abstract the identification of unequivocal evidence of humanly controlled fire is extremely problematic in archaeological contexts where obvious remains such as charcoal and ash have not been preserved until recently the difficulty of identification had been magnified by the lack of an established methodological approach which addressed the problem a methodological approach which can be used to identify and discriminate between archaeological evidence of fire resulting from natural processes and archaeological evidence of fire resulting from human activities is now available the approach utilizes several parameters of investigation including 1 macroscopic examinations of fire feature surfaces and profiles 2 analyses of magnetometer data 3 magnetic susceptibility studies 4 analyses of alternating field demagnetization characteristics 5 studies of isothermal remanent magnetization irm acquisition 6 analyses of coercivity of remanence characteristics and 7 palaeointensity studies the methodological approach is illustrated by comparing the results from analyses of features and samples from grass fire experiment sites isolated tree stump fire experiment sites multiple burn campfire experiment sites modern forest fire sites known archaeological hearths from modoc rock shelter illinois and known archaeological clay ovens from tell ashkelon israel for each available parameter of investigation comparisons revealed that multiple burn campfire sites exhibited basin shaped three dimensional configurations of oxidized sediments and diagnostic magnetic anomalies while multiple burn campfire samples displayed dramatic increases in magnetic susceptibility highly stable to very highly stable responses to alternating field demagnetization dramatic differences in irm acquisition and coercivity of remanence responses and diagnostic palaeointensity results when compared with the responses of adjacent unfired control samples archaeological hearth features and samples and samples from archaeological clay oven features exhibited results which were broadly consistent with the results from multiple burn campfire sites and samples the results displayed by grass fire isolated tree stump fire and forest fire sites and samples were generally found to be mutually exclusive from the results exhibited by multiple burn campfire and archaeological hearth and oven sites and samples for all parameters of investigation the results demonstrate that the methodological approach can be used to unequivocally identify archaeological evidence of humanly controlled fire resulting from multiple burn campfires fire hearths ovens and similar kinds of humanly produced fires

chemical transport to the seafloor of the equatorial pacific ocean across a latitudinal transect at 135 w tracking sedimentary major trace and rare earth element fluxes at the equator and the intertropical convergence zone we have analyzed the major trace and rare earth element composition of surface sediments collected from a transect across the equator at 135 w longitude in the pacific ocean comparing the behavior of this suite of elements to the caco3 opal and corg fluxes which record sharp maxima at the equator previously documented at the same sampling stations enables us to assess the relative significance of the various pathways by which trace elements are transported to the equatorial pacific seafloor the 1 1 high biogenic source at the equator associated with equatorial divergence of surface water and upwelling of nutrient rich water and 2 2 high aluminosilicate flux at 4 n associated with increased terrigenous input from elevated rainfall at the intertropical convergence zone itcz of the tradewinds are the two most important fluxes with which elemental transport is affiliated the biogenic flux at the equator transports ca and sr structurally bound to carbonate tests and mn primarily as an adsorbed component trace elements such as cr as pb and the rees are also influenced by the biogenic flux at the equator although this affiliation is not regionally dominant normative calculations suggest that extremely large fluxes of ba and p at the equator are carried by only small proportions of barite and apatite phases the high terrigenous flux at the itcz has a profound effect on chemical transport to the seafloor with elemental fluxes increasing tremendously and in parallel with ti normative calculations however indicate that these fluxes are far in excess of what can be supplied by lattice bound terrigenous phases the accumulation of ba is greater than is affiliated with biogenic transport at the equator while the p flux at the itcz is only 10 less than at the equator this challenges the common view that ba and p are essentially exclusively associated with biogenic fluxes many other elements including mn pb as and rees also record greater accumulation beneath the itcz than at the equator thus adsorptive scavenging by terrigenous paniculate matter or phases intimately associated with them appears to be an extremely important process regulating elemental transport to the equatorial pacific seafloor these findings emphasize the role of vertical transport to the sediment and provide additional constraints on the paleochemical use of trace elements to track biogenic and terrigenous fluxes

relationships between mineral surfaces and organic carbon concentrations in soils and sediments abstract relationships between mineral specific surface area and organic carbon oc concentration are examined for sediments and soil a horizons from throughout the world i found published elsewhere that continental shelf sediments from many different regions exhibit downcore loss of oc to a refractory background level which shows a consistent relationship with mineral surface area slope 0 86 mg m 2 oc this trend is equivalent to a monolayer of organic matter over all surfaces and is termed the monolayer equivalent me level sediments and soils from other environments are compared to this empirically derived relationship several continental slope areas show extension of this relationship to considerable depth marked excesses of oc above this trend which persist downcore were found in sediments with high carbonate mineral content or slope sediments with low dissolved oxygen concentrations in the overlying water column about half of the soils examined also adhered to this relationship while soils with high carbonate content low ph or poor drainage showed oc concentrations higher than the me level oc concentrations below the me level are found in deltaic regions and areas with low organic matter delivery such as the deep sea or arid soils the nature of mineral surfaces was examined using n2 adsorption desorption isotherms and most surface area was found to be present as pores with

labyrinth of doom a device to minimize the swimmer component in sediment trap collections a simple device used to discriminate between swimmers and nonswimmers in sediment trap collections has been developed it consists of a series of funnels which concentrate passively sinking material into a central collection tube whereas swimmers are distributed randomly between the inner and outer collection tubes the degree to which swimmer nonswimmer fractionation is achieved depends on the number and spacing of funnels and the ratio of inner to outer collection tube areas although inner collection tube samples contain a few swimmers there are considerably fewer than are collected in cod ends without this device furthermore outer tube contents are devoid of passively sinking material providing a pure swimmer fraction which can be compared to inner collection tube contents this device has been successfully deployed on many occasions in traps of the soutar conical and knauer cylindrical type as part of the vertex program in the ne pacific

compositions and transport of lipid biomarkers through the water column and surficial sediments of the equatorial pacific ocean abstract a systematic investigation of fluxes and compositions of lipids through the water column and into sediments was conducted along the u s jgofs egpac transect from l2 n to l5 s at 140 w fluxes of lipids out of the euphotic zone varied spatially and temporally ranging from 0 20 0 6 mmol lipid c m 2 day 1 lipid fluxes were greatly attenuated with increasing water column depth dropping to 0 002 0 06 mmol lipid c m 2 day 1 in deep water sediment traps sediment accumulation rates for lipids were 0 0002 0 00003 mmol lipid c m 2 day 1 lipids comprised 11 23 of corg in net plankton 10 30 in particles exiting the euphotic zone 2 4 particles in the deep egpac and 0 1 1 in sediments lipids were in general selectively lost due to their greater reactivity relative to bulk organic matter toward biogeochemical degradation in the water column and sediment qualitative changes in lipid compositions through the water column and into sediments are consistent with the reactive nature of lipids fatty acids were the most labile compounds with polyunsaturated fatty acids pufas being quickly lost from particles branchedchain c15 and c17 fatty acids increased in relative abundance as particulate matter sank and was incorporated into the sediment indicating inputs of organic matter from bacteria long chain c39 alkenones of marine origin and long chain c20 c30 fatty acids alcohols and hydrocarbons derived from land plants were selectively preserved in sediments compositional changes over time and space demonstrate the dynamic range of reactivities among individual biomarker compounds and hence of organic matter as a whole a thorough understanding of biogeochemical reprocessing of organic matter in the oceanic water column and sediments is thus essential for using the sediment record for reconstructing past oceanic environments

structurally controlled hydrothermal dolomite reservoir facies an overview structurally controlled hydrothermal dolomite htd reservoir facies and associated productive leached limestones are major hydrocarbon producers in north america and are receiving increased exploration attention globally they include multiple trends in the ordovician locally silurian and devonian of the michigan appalachian and other basins of eastern canada and the united states and in the devonian and mississippian of the western canada sedimentary basin they also occur in jurassic hosts along rifted atlantic margins in the jurassic cretaceous of the arabian gulf region and elsewhere hydrothermal dolomitization is defined as dolomitization occurring under burial conditions commonly at shallow depths by fluids typically very saline with temperature and pressure t and p higher than the ambient t and p of the host formation the latter commonly is limestone proof of a hydrothermal origin for htd reservoir facies requires integration of burial thermal history plots fluid inclusion temperature data and constraints on timing of emplacement hydrothermal dolomite reservoir facies are part of a spectrum of hydrothermal mineral deposits that include sedimentary exhalative lead zinc ore bodies and htd hosted mississippi valley type sulfide deposits all three hydrothermal deposits show a strong structural control by extensional and or strike slip wrench faults with fluid flow typically focused at transtensional and dilational structural sites and in the hanging wall transtensional sags above negative flower structures on wrench faults are favored drilling sites for htd reservoir facies saddle dolomite in both replacive and void filling modes is characteristic of htd facies for many reservoirs matrix replacive dolomite and saddle dolomite appear to have formed near contemporaneously and from the same fluid and temperature conditions the original host facies exerts a major influence on the lateral extent of dolomitization resultant textures pore type and pore volume breccias zebra fabrics shear microfractures and other rock characteristics record short term shear stress and pore fluid pressure transients particularly proximal to active faults high temperature hydrothermal pulses may alter kerogen in host limestones a process designated forced maturation basement highs underlying sandstone and or carbonate aquifers probably overpressured and overlying and internal shale seals and aquitards also may constrain or influence htd emplacement although many questions and uncertainties remain particularly in terms of mg and brine source and mass balance recognition and active exploration of the htd play continues to expand increasing use of three dimensional seismic imagery and seismic anomaly mapping combined with horizontal drilling oblique to linear trends defined by structural sags helps to reduce risk