large striated burrows from fluvial deposits of the neogene vinchina formation la rioja argentina a crab origin suggested by neoichnology and sedimentology abstract this study includes three aspects 1 the ichnotaxonomic treatment of large and dominantly vertical burrows ornamented with sharp bioglyphs from the fluvial neogene vinchina and toro negro formations northwest argentina 2 the description and interpretation of the sedimentary facies where these burrows occur and 3 neoichnologic observations on large ornamented burrows from seasonal wetlands of the rio pilcomayo national park argentina as possible modern analogues of the trace fossils and the sedimentary environment a new ichnogenus and ichnospecies capayanichnus vinchinensis is proposed to include the large striated burrows the new ichnotaxon is distinguished by a combination of a predominantly vertical orientation overall l shape when fully developed absence of lining and burrow bifurcation a distinct surface texture and lack of burrow enlargements the hosting sedimentary facies of the vinchina formation can be grouped into fluvial channel and splay floodplain facies associations the rivers of that unit were of two main types single channel rivers with frequent channel avulsion and overbank flow and multichannelised rivers with poorly defined margins at least some of these rivers were ephemeral or with intermittent discharge the climate was probably seasonal and semiarid as suggested by sedimentologic evidence c vinchinensis was dominantly recorded from the top of fluvial channels interpreted as abandoned channels and proximal intermediate and distal splay facies the large ornamented burrows found in an extant comparable example were constructed by freshwater crabs these burrows can be distinguished by the overall architecture the taxonomy and sex of its occupants and the environmental setting where they were found the neoichnologic signatures used in the interpretation of the fossil example include the common oval burrow cross section and the surface texture in particular the surface texture in the modern crab burrows includes abundant comma shaped marks sets of grooves oblique to burrow axis and long segmented grooves the predominantly oval cross section absence of lining and the strongly ornamented burrow surface suggest that c vinchinensis was produced by freshwater crabs the key features of the surface ornament are long sets of three four ridges whose width is in average one third of the burrow major axis other features that also point to a crab origin are a massive filling common burrow ends in a casing mudstone chevron pattern in sets of surface ridges and possible cheliped marks the new ichnotaxon is restricted in the vinchina and toro negro formations to fluvial facies and is absent in shallow lacustrine facies

sedimentary pyrite formation an update sedimentary pyrite formation during early diagenesis is a major process for controlling the oxygen level of the atmosphere and the sulfate concentration in seawater over geologic time the amount of pyrite that may form in a sediment is limited by the rates of supply of decomposable organic matter dissolved sulfate and reactive detrital iron minerals organic matter appears to be the major control on pyrite formation in normal non euxinic terrigenous marine sediments where dissolved sulfate and iron minerals are abundant by contrast pyrite formation in non marine freshwater sediments is severely limited by low concentrations of sulfate and this characteristic can be used to distinguish ancient organic rich fresh water shales from marine shales under marine euxinic conditions sufficient h2s is produced that the dominant control on pyrite formation is the availability of reactive iron minerals calculations based on a sulfur isotope model indicate that over phanerozoic time the worldwide average organic carbon to pyrite sulfur ratio of sedimentary rocks has varied considerably high cs ratios during permo carboniferous time can be explained by a shift of major organic deposition from the oceans to the land which resulted in the formation of vast coal swamps at that time low cs ratios compared to today during the early paleozoic can be explained in terms of a greater abundance of euxinic basins combined with deposition of a more reactive type of organic matter in the remaining oxygenated portions of the ocean the latter could have been due to lower oceanic oxygen levels and or a lack of transportation of refractory terrestrial organic matter to the marine environment due to the absence of vascular land plants at that time

early diagenesis in differing depositional environments the response of transition metals in pore water the cycling of fe mn ni co cu cr v and mo during early diagenesis was investigated in sediments from five different depositional environments in the california borderland dissolved o2 no3 no2 and so4 were also measured at each site to establish the position of redox boundaries pertinent to this study sites were chosen to allow the comparison of several parameters of potential importance to the cycling of these metals bottom water o2 concentration sediment redox conditions cycling of metal oxide carrier phases and the relative contribution of biogenic and terrigenous material to the detrital metal flux at 10 m oxygen and above the sequence of terminal electron acceptor utilization was typical of pelagic sediments differing only in scale under these conditions the recycling of mn oxides resulted in an enriched layer near the interface at bottom water 02 concentrations 5 m mn oxides are not recycled under these conditions fe oxides and so42 are important oxidants the depth of the zone of manganese oxidation with respect to the interface affects the efficiency of metal scavenging by manganese oxides trapping and recycling of ni and co with mn oxides results in remobilization from reducing sediments and enrichment in oxic sediments scavenging of these metals is favored by a deep oxic zone in the sediments in contrast cr v and mo appear to be transported to the sediments as reduced species and are released from the sediments by oxidation the source of the reduced species is assumed to be biogenic material the accumulation of these metals is favored by reducing conditions in the sediments cu is enriched in the sediments by transport with detrital biogenic material followed by adsorption onto sediment solids cu is released at the interface and rapidly removed onto the solids at all sites except the one pelagic site at the base of the slope the magnitude of cu released in the slowly accumulating pelagic sediment exceeds the cu binding capacity of the solids resulting in pore water cu concentrations in excess of 100 nm in general metal cycling associated with the early diagenesis of sediments was observed to decouple transport processes from burial processes for the transition metals measured in this study

extreme climatic conditions recorded in santa barbara basin laminated sediments the 1835 1840macoma event abstract the santa barbara basin sbb record of laminated sediment well known for its excellent time resolution shows the presence of an unusual once in a millenium event in the period 1835 1840 at a depth of 55 57 cm below the surface of the seafloor this macoma event is the brief flourishing of a macrofaunal community in the deep center of the sbb from which large organisms are normally excluded by the lack of oxygen shells of the pelecypodmacoma leptonoidea dall and associated fossils which congregate in a thin layer dated at 1840 provide evidence for a sudden local extinction of macrobenthos by suffocation various stratigraphic evidence suggests thatm leptonoidea colonized the basin floor for a few years prior to 1840 as a result of temporarily decreased productivity and increased oxygen content in the water spilling over the sill into the basin historical eyewitness reports indicate unusually severe winter storms from southeasterly directions during the 1830s in the sbb we suggest that coastal upwelling was severely reduced during 1835 1839 with the effect of reducing the intensity of the oxygen minimum layer themacoma event apparently is one manifestation of large scale climatic anomalies felt throughout north america and which were possibly linked to the major volcanic eruption of cosiguina nicaragua in 1835

climatically controlled marker layers in santa barbara basin sediments and fine scale core to core correlation varved sediments with annual layering can provide a detailed history of environmental conditions of marginal ocean basins and of lakes to reconstruct this history requires fine scale correlation and correct age assignment in the santa barbara basin a combination of x radiography water content profiles and microfossil stratigraphy yields correlations of the desired resolution x radiography permits identification of individual layers 1 2 mm thick that differ in porosity or pore water content and hence x ray absorption microfossils and sedimentological parameters provide the clues to the presence for el nino years e g in a d 1984 1959 and 1942 varves allowing the tie in to absolute years within this century el nino layers once identified are readily recognized on the radiographs and within the porosity profiles counting of laminae in x radiographs and core to core correlation via water content then allow establishing age scales for other cores a prominent shell layer in the first half of the 19th century is dated at a d 1838 this event macoma i is of supraregional significance

contemporaneous early diagenetic formation of organic and inorganic sulfur in estuarine sediments from st andrew bay florida usa estuarine sediment samples were collected from nine stations in st andrew bay near panama city florida usa contrasting grain size and varying concentration of organic carbon allowed a comparative study of the relationships among organic degradation processes sulfur cycling and diagenetic removal of dissolved sulfide produced by bacterial sulfate reduction abundance and sulfur isotopic composition were determined for dissolved sulfide dissolved sulfate pyrite humic acid sulfur fulvic acid sulfur and elemental sulfur presence of free dissolved sulfide and enrichment in 34s of porewater sulfate in samples from organic rich muddy sediments of st andrew bay indicate high rates of sulfate reduction and anoxic conditions below 5 mm depth such conditions are not reflected in samples from organic poor sandy near shore sediments collected from highly productive areas occupied by seagrass beds in this estuarine system pyrite and fulvic acid sulfur are the largest sinks for sulfide produced by bacterial sulfate reduction strong correlation between abundances of pyrite and fulvic acid sulfur suggests coincident formation in the uppermost 10 cm of sediment large differences in isotopic composition between these two species and consistent enrichment in 34s of the fulvic acid fraction however indicate two different reaction pathways abundance and sulfur isotopic composition of humic acid and fulvic acid sulfur suggest that organic sulfur is derived from mixing between 1 34s depleted sulfur with an unknown oxidation state that was recycled from bacterial hydrogen sulfide and 2 34s enriched sulfur interpreted as primary biosynthetic sulfur originally assimilated from dissolved sulfate samples taken from sandy sediment localities where aquatic vascular plants are rooted in the anoxic zone show a strong depletion in 34s in the fulvic acid sulfur fraction suggesting recycled hydrogen sulfide as the dominant source of organic sulfur

gravity inferred crustal attributes of visible and buried impact basins on mars 1 the impact basins of mars reveal important insights on martian tectonic evolution they involve strongly disrupted depressed regions of crust with likely enhanced porosity and permeability that may locally concentrate water and other crustal fluids hence the crustal properties of impact basins can also be important in the hunt for water and related clues for life on mars we assess the crustal details of impact basins by separating the mars global surveyor free air anomalies into terrain correlated and terrain decorrelated components the separation is based on the correlation spectrum between the free air anomalies and the gravity effects evaluated from the topography mapped by the mars orbital laser altimeter mola for topographically visible multiring basins like isidis striking circular patterns of alternating terrain correlated free air maxima and minima mark the uncompensated components of the central mantle plug and surrounding rings the first vertical derivatives of these anomalies effectively estimate the basin ring locations and a transient cavity depth to diameter ratio of 0 09 that is consistent with the ratio observed for lunar nearside multiring basins for the isidis basin we obtain an excavation depth of roughly 66 km that reflects considerably disrupted crust for concentrating local fluids since the noachian impact furthermore the related crustal terrain decorrelated free air anomalies suggest up to 2 km of high density basin fill may cap the central basin subtle quasi circular depressions in the relatively featureless mola terrain of the northern hemisphere have identified potentially buried impact basins frey et al 2002 an altimetry depression in acidalia planitia and another in utopia are also associated with ringed patterns of terrain decorrelated free air anomalies that may mark the uncompensated mass effects of buried impact basins the gravity derived transient excavation depths for these inferred basins are roughly 41 and 20 km respectively while the related ring diameters d follow the ubiquitous d rule of planetary impact basins the crust of these buried basins is likely to contain water at higher levels than the crust of the equatorial basins that was substantially dewatered with the development of the great northern basin hence analyzing surface fractures faults and other crustal discontinuities that can tap the more saturated crust of these inferred buried basins may facilitate the hunt for water on mars

early diagenetic alteration of organic matter by sulfate reduction in quaternary sediments from the northeastern arabian sea abstract hemipelagic sediments from the northeastern arabian sea off pakistan were analyzed by geochemical and microscopical methods to study the importance of bacterial degradation processes on the quantity and composition of sedimentary organic matter om on the basis of elemental analysis of total organic carbon toc and total sulfur ts the decay of om by sulfate reducing bacteria were calculated concentrations of total iron reactive iron total nitrogen tn total phosphorus tp and hydrogen indices hi were used to assess organic matter reactivity and redox conditions stable sulfur isotopic compositions provided further information about pathway timing and mechanisms of sulfate reduction microscopical observations indicate that throughout the study area om is amorphous 75 95 in almost all samples with only a small contribution of terrigenous om bacterially mediated sulfate reduction leads to continuously decreasing toc ts ratios from 0 4 m to a burial depth of 2 3 m at this depth the anaerobic oxidation of particulate organic matter ceases sulfate reduction in this narrow interval accounts for the decay of up to 70 of the om which has primarily entered the anoxic domain during the bacterially mediated diagenesis preferential consumption of nitrogen and phosphorus containing organic compounds can be observed and quantified the regeneration of up to 60 of tn and more than 50 of tp can lead to a feedback of nutrients to the seawater this recycling process may contribute to the high productivity in the northeastern arabian sea

seasonal dynamics of elemental sulfur in two coastal sediments a spectrophotometric method for elemental sulfur s0 analysis without interference from other reduced sulfur compounds was adapted for the use in reducing sediments the s0 distribution in two coastal sediments was studied regularly from summer to winter and compared to factors regulating the s0 accumulation such as redox potentials the rate of bacterial sulfide production and the general sulfur chemistry dense coatings of sulfur bacteria developed on the sediment surface of a sulfuretum which had an s0 concentration of up to 41 mol s cm 3 the 2 5 mm thick bacterial coating contained 40 of all s0 in the sediment a more typical marine sediment with a few cm thick oxidized surface layer had an s0 maximum of 1 3 mol s cm 3 at 2 4 cm depth the s0 maximum in both sediments increased from summer to winter as the sediments gradually became more oxidized the deeper layers maintained a low s0 concentration most of the s0 in the upper few mm of a laboratory sulfuretum was present inside sulfur bacteria and actively migrated up and down with the bacteria depending upon the changing light and oxygen conditions

an alkenone u 37 k quasi annual sea surface temperature record a d 1440 to 1940 using varved sediments from the santa barbara basin abstract analyses for c37 alkenones u37k and total organic carbon toc in a varved core from the depocenter of the santa barbara basin 34 13 5 n 120 01 w 590 m water depth have been made on an approximately 1 2 year basis from a d 1440 to 1940 the u37k based sea surface temperature sst record oscillates around 15 5 c with an amplitude of less than 3 c at approximately interannual decadal and centennial frequencies historical el nino southern oscillation enso events are matched only partially by warmer u37k ssts three records our sst a published pacific coral 18o and a published tree ring temperature anomaly from the california valleys show no evidence of colder temperatures during the little ice age ca 1500 to 1840 a d significantly there is a strong centennial scale cyclicity in the u37k sst record which approaches 1 c in amplitude toc burial and alkenone fluxes are largely controlled by sedimentation rate as expressed in varve thickness

occurrence of bioglyphs on ocypode crab burrows in a modern sandy beach and its palaeoenvironmental implications abstract the ichnological term bioglyph covers biogenic sculpture on burrow walls bioglyphs in the burrows of ocypodid crabs were studied in a modern unconsolidated sandy substrate looseground on irino coast southwestern japan they are seen exclusively on sides and roof of the burrow and are characteristically seen near the distal end of the burrow moist sandy substrate where sand particles are bound together by surface tension of interstitially suspended water might allow the production of such bioglyphs although bioglyphs are only partially developed in such burrows those interpreted to have formed in semi consolidated substrates firmground are known to be sculptured over the entire burrow surface such difference in the modes of bioglyph occurrence can be used as a criterion to reconstruct the substrate consistency in the rock record

sulfur enrichment of humic substances in a delaware salt marsh sediment core abstract humic sulfur operationally defined as the sulfur extracted with humic substances in 0 l n naoh solution comprises up to 51 of the total sulfur inventory in a sediment core taken from a delaware spartina alterniflora marsh pyrite sulfur is the next largest fraction except at the near surface sediments where zerovalent sulfur concentrations are significant x ray photoelectron spectroscopy indicates that the humic sulfur consists of sulfoxides or sulfones and in a more reduced state organic sulfides and or organic polysulfides a subsurface decrease in the humic acid c s atomic ratio to 56 2 suggests that the upper 4 cm of marsh sediment is the locus for humic sulfur formation s alterniflora detritus and microbial biomass cannot fully account for observed sulfur enrichment of humic c s atomic ratios therefore the enrichment of humic substances by sulfur is probably via reaction of reduced sulfur compounds with organic matter a humic sulfur formation rate of 10 6 mol s cm 3 a 1 is calculated for the surface sediments and leads to an areal production of 18 mol s cm 2 a 1 of humic sulfur humic sulfur formation and preservation is enhanced by the limited availability of iron for the rapid precipitation of iron sulfide minerals and the apparent resistance of organic sulfur compounds towards reoxidation to sulfate especially in the upper 9 cm of marsh sediment where inorganic sulfur compounds are rapidly oxidized

geochemistry of inorganic and organic sulphur in organic rich sediments from the peru margin abstract we have determined 1 the abundance and isotopic composition of pyrite monosulphide elemental sulphur organically bound sulphur and dissolved sulphide 2 the partition of ferric and ferrous iron 3 the organic carbon contents of sediments recovered at two sites drilled on the peru margin during leg 112 of the ocean drilling program sediments at both sites are characterised by high levels of organically bound sulphur obs obs comprises up to 50 of total sedimentary sulphur and up to 1 of bulk sediment the weight ratio of s to c in organic matter varies from 0 03 to 0 15 mean 0 10 such ratios are like those measured in lithologically similar but more deeply buried petroleum source rocks of the monterey and sisquoc formations in california the sulphur content of organic matter is not limited by the availability of porewater sulphide isotopic data suggest that sulphur is incorporated into organic matter within a metre of the sediment surface at least partly by reaction with polysulphides most inorganic sulphur occurs as pyrite pyrite formation occurred within surface sediments and was limited by the availability of reactive iron but despite highly reducing sulphidic conditions only 35 65 of the total iron was converted to sulphide 10 30 of the total iron still occurs as fe iii in surface sediments the isotopic composition of pyrite is similar to that of both iron monosulphide and dissolved sulphide either pyrite like monosulphide formed by direct reaction between dissolved sulphide and detrital iron and or the sulphur species responsible for converting fes to fes2 is isotopically similar to dissolved sulphide likely stoichiometries for the reaction between ferric iron and excess sulphide imply a maximum resulting fes2 fes ratio of 1 1 where pyrite dominates the pool of iron sulphides at least some pyrite must have formed by reaction between monosulphide and elemental sulphur and or polysulphide elemental sulphur s0 is most abundant in surface sediments and probably formed by oxidation of sulphide diffusing across the sediment water interface in surface sediments s0 is isotopically heavier than dissolved sulphide fes and fes2 and is unlikely to have been involved in the conversion of fes to fes2 polysulphides are thus implicated as the link between fes and fes2

subtropical hydroclimate during termination v 430 422 ka annual records of extreme precipitation drought and interannual variability from santa barbara basin abstract hydroclimate extremes are expected to become more frequent and intense with anthropogenic climate forcing but future el nino southern oscillation enso behavior is unclear understanding of extreme hydroclimate variability and magnitude prior to human influences is limited by short instrumental records however continuous sedimentary archives of past hydroclimate variability can complement and extend these records laminated santa barbara basin sbb sediment cores mv0508 33jpc 21jpc and 29jpc preserve annually resolved multi centennial scale precipitation records from termination v t v the transition from glacial marine isotope stage mis 12 to interglacial mis 11 at 424 ka these records provide insights into the subtropical hydroclimate response to warming foraminiferal 18 o variations indicate rapid warming and or salinity changes and were used to verify the t v age assignment a paleoprecipitation proxy was developed using the first principal component of scanning xrf elemental counts pc1 which has high loadings for siliciclastic sediment associated elements k ti and si sedimentary laminae couplets identified in pc1 were annually tuned to investigate t v paleoprecipitation variability as modern sbb laminae represent annual deposits extreme flooding and decadal to centennial droughts were identified with magnitudes exceeding modern observations enso like 2 7 year paleoprecipitation periodicities coincide with wetter intervals but enso variability is reduced during droughts a 1500 year arid interval may be related to poleward shifting of general atmospheric circulation as ice sheets melted such that the subtropical dry zone intersected california southern california paleoprecipitation reconstructions from past warm climates provide insight into precipitation variability and magnitude on interannual timescales and can reduce uncertainties in predictions of interannual climate including enso

origin and diagenetic transformations of c25 and c30 highly branched isoprenoid sulphur compounds further evidence for the formation of organically bound sulphur during early diagenesis abstract a number of c25 and c30 highly branched isoprenoid hbi sulphur compounds e g thiolanes 1 oxo thiolanes thiophenes and benzo b thiophenes with 2 6 10 14 tetramethyl 7 3 methylpentyl pentadecane and 2 6 10 14 18 pentamethyl 7 3 methylpentyl nonadecane carbon skeletons were identified in sediments ranging from holocene to upper cretaceous these identifications are based on mass spectral characterisation desulphurisation and in some cases by comparison of mass spectral and relative retention time data with those of authentic standards the presence of unsaturated c25 and c30 hbi thiolanes in a recent sediment from the black sea age 3 6 10 3 a strongly supports their formation during early diagenesis the co occurrence of hbi polyenes c25 and c30 and unsaturated hbi thiolanes c25 and c30 possessing two double bonds less than the corresponding hbi polyenes in this recent sediment testifies to the formation of unsaturated hbi thiolanes by a reaction of inorganic sulphur species with double bonds of the hbi polyenes furthermore a diagenetic scheme for hbi sulphur compounds is proposed based on the identification of hbi sulphur compounds in sediment samples with different maturity levels

paleoproductivity ventilation and organic carbon burial in the santa barbara basin odp site 893 off california since the last glacial biogenic burial rates and coccolith assemblage data were generated for the past 16 ka at odp site 893 in the santa barbara basin off california to determine if dysoxic events in the basin were related to changes in marine productivity coccolith abundance data show that changes in surface water conditions did indeed change in concert with oxygen levels at the sea floor however organic carbon burial rates varied independently indicating that oxygenation of the water column is related mainly to intermediate water ventilation a strong correlation of organic carbon burial rates with lithogenic and to a lesser extent with carbonate and opal accumulation rates confirms recent conclusions that the export of organic carbon from the sea surface is largely controlled by the presence of ballast minerals

organic matter preservation and sulfur uptake in sediments from the continental margin off pakistan abstract the bulk and molecular geochemical characteristics of a suite of kerogens isolated from organic matter rich sediments from the pakistan margin has been characterised by elemental analysis rock eval pyrolysis and pyrolysis gas chromatography py gc special attention was given to the geochemistry of alkylthiophenes which are thought to reflect the incorporation of sulfur into organic matter om in the context of early diagenetic sulfate reduction organically bound sulfur comprises up to 60 of total sedimentary sulfur the weight ratios for organic sulfur s org over organic carbon c org varies from 0 01 in some of the recently deposited sediments to 0 11 in older samples the results show that sulfur incorporation into organic matter occurs primarily within the upper few meters of the sediments the amount of sulfur which can be incorporated into the organic matter clearly depends on the quality of om the hydrogen index values hi which characterise the total amount of generated hydrocarbon equivalents of the pyrolysate in mg hc equiv g c org are related to the extent of reworking of organic matter either in the water column or at the sediment water interface or to remineralization processes by sulfate reduction itself which is strongly controlled by the availability of reactive iron high quality organic matter characterised by elevated hi values is capable of sequestering higher amounts of sulfur as expressed by the thiophene content which represent the organically bound sulfur of the pyrolysate in mg g c org as indicated by the ratio of thiophenes versus hi which characterises the proportion of thiophenes in the total pyrolysate sulfurisation of organic matter seems to be terminated at a ratio of 0 01

a fast and easy method to derive highest resolution time series datasets from drillcores and rock samples abstract we present a fast method to obtain highest resolution greyvalue datasets from digital core images these datasets are processed using a software package developed by us artificially introduced trends in the datasets are corrected disturbances i e cracks voids are eliminated to reduce the high level noise in data we have developed a vector filter that effectively removes such noise application of the method to odp drillcores from the santa barbara basin allowed exact correlation of two drillcores from the same basin the influence of the termination of the last glacial cold period on the flux rates in the basin are reflected in the greyvalue datasets we found a transitional period of about 3000 yr between the end of the last glacial cold period and the onset of post glacial climatic oscillation in the basin fourier analyses show that the high resolution greyvalue time series record climatic cycles with frequencies as high as 1 cycle yr varves

evolutionary changes over the last 1000 years of reduced sulfur phases and organic carbon in varved sediments of the santa barbara basin california abstract sediments from the santa barbara basin sbb of the last 1000 years were analyzed for elemental sulfur se mineral sulfide sulfur sm lipid based organically bound sulfur sx residual organically bound sulfur so total organic carbon toc and total nitrogen tn the approximate annual resolution of the time series data permitted us to evaluate the influence of oceanic variables on the benthic environment and the accumulating varved sediment in the sbb a bacterial mat community at or near the sediment surface is influencing sediment porosity and the production and distribution of se early diagenesis dampens the amplitude of environmental signals in the geochemical time series the concentrations of sm and so increase with burial depth at the expense of decreasing concentrations of sx and se at depths greater than 5 5 cm corresponding to an age of 7 years sm becomes the largest pool of reduced sulfur it requires approximately 500 years of primarily bacterially mediated diagenesis equivalent to a burial depth of 1 4 m for sbb sediments to gradually approach and finally enter the region assumed to represent typical normal marine sediments on a plot of weight percent toc vs sm

particulate iron and manganese in the santa barbara basin california abstract particulate fe and mn may be important trace metal scavengers in the water column as well as being probable indicators of biologically mediated redox processes a study has been made of suspended particulate composition in the santa barbara basin a shallow near shore basin off southern california with sub oxic conditions below sill depth observations have revealed several interesting phenomena relating to the geochemistry of fe and mn most striking is a profound enrichment of particulate fe in samples from the bottom two hundred meters these particulates have a constant fe p mole ratio of about three and may originate at the sediment water interface or may be transported to the basin from local marshes for particulate mn enrichments are observed both in the sub sill waters and near the base of the euphotic zone a consideration of particle removal rates suggests that the sub photic zone enrichment has a biogenic origin in the sub sill waters enrichment in mn is apparently due to the precipitation of dissolved mn diffusing from the anoxic basin sediments a simple mass balance suggests that most of the mn lost from the sediments is transported from the santa barbara basin in dissolved form

psilonichnus upsilon frey curran and pemberton 1984 burrows and their environmental significance in transgressive albian lower cretaceous sands of glanow stroniczki cracow upland southern poland abstract a considerable upper albian sand lithosome developed on the external margin of the albian epicontinental sea in the polish jura chain miechow synclinorium southern poland is recognized as a shallowing up sequence within the generally transgressive albian sands in particular burrows described as the ichnospecies psilonichnus upsilon frey curran and pemberton 1984 have a particular ecologic and sedimentological significance and constitute the primary focus of this paper in the glanow stroniczki section cracow upland southern poland such burrows seem to be a crucial tool in the interpretation of basin bathymetry indicating a foreshore to backshore beach facies and probably recording a temporary break in sedimentation they were infilled by sand with pebbles or pebble material potentially during hurricane or strong storm action lithification of the burrow infillings and their enveloping concretionary halos should have progressed in a beachrock mode the glanow horst composed of jurassic biohermal limestones was likely an emerged element that neigboured or was surrounded by a beach with active fauna the psilonichnus upsilon burrows in glanow stroniczki closely resemble burrows of the modern ghost crab ocypode in modern settings representatives of ocypode are encountered in extremely shallow marine foreshore intratidal and backshore supratidal to dune environments the ichnological data from glanow stroniczki suggests that fauna behaviorally similar to ocypode may have occupied the beach backshore and to a lesser extent the foreshore zone near the emerged glanow horst

from extreme rainfall to drought 250 years of annually resolved sediment deposition in santa barbara basin california abstract the mediterranean climate of southern california is marked by droughts and extreme precipitation events here we use elemental variations generated by scanning x ray fluorescence xrf to identify droughts and floods in recently deposited 1755 2008 sediments of santa barbara basin sbb from box core spr0901 04bc the first principal component pc1 of the scanning xrf elements has high loadings for elements associated with the lithogenic component of sbb laminae couplets while the second pc2 is associated with biogenic components we interpret pc1 as a proxy for river runoff and pc2 as a proxy for marine productivity high values of pc1 are associated with el nino events and positive warm phases of the pacific decadal oscillation pdo while low values of pc2 are associated with el nino events and negative cool phases of the pdo droughts such as the 1934 40 1949 56 and 1989 91 events coincide with low pc1 values in addition to distinguishing interannual and decadal variability in the elemental composition of sbb sediments several historic floods can be recognized including a gray flood layer associated with the 1861 62 flood and a peak in pc1 associated with the flood following the st francis dam disaster in 1928

trace element behavior and redox facies in core shales of upper pennsylvanian kansas type cyclothems the black shale submember of core shales of pennsylvanian kansas type cyclothems is highly enriched in redox sensitive trace elements tes relative to the overlying gray shale submember as well as to many other modern and ancient organic rich deposits controls on trace element behavior in the black shale can be inferred from trace element enrichment factors efs relative to gray shale and the relationship of tes to total organic carbon toc most tes conformed to one of two patterns 1 mo u v zn and pb exhibited moderate efs and strong covariation with toc in samples having 10 wt toc and 2 cu ni cr and co exhibited low efs and moderate to strong covariation with toc in all samples these patterns are inferred to represent different responses to benthic redox conditions the first pattern is characteristic of tes of strong euxinic affinity i e those taken up in solid solution by fe sulfide or involved in other reactions catalyzed by free h2s and resident mainly in authigenic phases whereas the second pattern is characteristic of tes of weak euxinic affinity i e those not strongly influenced by the presence of free h2s and resident mainly in the organic carbon or detrital fractions of the sediment these inferences allowed development of a multiproxy technique for assessing redox facies in black shale samples euxinic conditions were considered to have existed if at least two of four redox indicator trace elements mo u v zn showed euxinic levels of enrichment and nonsulfidic anoxic conditions were inferred otherwise the validity of the procedure is indicated by 1 agreement among all four redox indicators for a large majority of samples 69 of 185 2 among samples yielding a mixed redox signal a systematic sequence of te enrichment v zn mo u and 3 for tes of weak euxinic affinity reduced variance among samples representing each redox facies sequential enrichment may be a response to differential redox thresholds for accumulation e g v or postdepositional remobilization of trace elements e g u and may provide a basis for finer assessment of redox conditions in low oxygen paleoenvironments than permitted by simple classification schemes the multiproxy procedure for redox facies analysis developed in this study is likely to be more reliable than widely used single proxy indicators based on trace elements e g mo authigenic u or v v ni or c s fe systematics e g s toc or dop d 2004 elsevier b v all rights reserved

authigenic carbonates derived from oxidized methane vented from the makran accretionary prism off pakistan we report the first discovery and sampling of a methane hydrogen sulfide rich cold seep from the makran accretionary prism off pakistan arabian sea a variety of cm to m scale pockmarks and gas seepage structures were identified from underwater tv photo sled profiles crossing the oxygen minimum zone omz related to highresolution seismic parasound records from the seeps isotopically light bacterially formed methane is emanating that is partly oxidized to hco3 in the bacterial sulfate reduction zone this results in the precipitation of irregular dark gray to black crusts of indurated authigenic carbonates mainly cryptocrystalline magnesian calcite and ca rich dolomite near the sediment seawater interface within the omz downcore the crusts grade into hemipelagic carbonate poor silty clays with transitional lithologies in between similar to the pockmark carbonates from the oregon margin and in the north sea the authigenic carbonates are extremely depleted in 13c 13ccarbonate 40 this suggests that they were derived from bacterial methane 13cmethane 77 8 that was oxidized under anaerobic conditions the authigenic carbonates are associated with white fluffy mats of chemoautotrophic h2s oxidizing bacteria small pockmarks appear to be concentrated at small scale escarpments suggesting focussed fault controlled pore fluid expulsion due to the tectonic dewatering and degassing of the accretionary prism whereas diffuse discharge of pore fluids is inferred from the widespread occurrence of tiny gas bubble tubes

a 9000 year flood history for southern california a revised stratigraphy of varved sediments in santa barbara basin abstract the center of santa barbara basin sbb preserves annual laminations through most of the holocene providing an important locality for high resolution late quaternary paleoclimate and paleoceanography reconstructions an accurate chronology is necessary for these sediment based records and enables comparisons with more distal data time series of similar quality here we present an improved high resolution radiocarbon chronology for the last 9000 yrs based on 89 accelerator mass spectrometric ams 14c dates of mixed planktonic foraminiferal carbonate from three sediment cores collected in sbb mv0811 14jc spr0901 06kc and odp hole 893a accurate core to core correlation is demonstrated using prominent gray flood and olive turbidite layers identified in sbb and dated in multiple cores gray layer deposits were found more frequently in wetter intervals as determined by multi proxy hydroclimate records in southern california e g lake deposits and tree rings mass accumulation rates mars calculated for the sbb depocenter using the improved radiocarbon age model indicate high mars are associated with these gray layers that have been associated with floods thus sediment accumulation in sbb is largely controlled by sediment delivery via river runoff following precipitation events although mars may also be influenced by other factors that enhance erosion in river catchments folded sediment is observed within the basal core section of mv0811 14jc which stratigraphically correlates with 14c age reversals in odp hole 893a we associate this sediment slump feature with the large goleta submarine slide complex in santa barbara channel and estimate the submarine slide event occurred at 9000 200 yrs bp furthermore small olive turbidite layers identified and dated in sbb can be temporally linked with large earthquakes along san andreas fault and can therefore potentially reconstruct earthquake history in southern california

distribution and sources of polycyclic aromatic hydrocarbons pahs in laminated santa barbara basin sediments abstract the santa barbara basin sbb preserves a high resolution sediment record that is varved down to ca 1700 ce and laminated for at least 2500 years the distributions of 25 polycyclic aromatic hydrocarbons pahs were investigated in a suite of samples from sediment cores representing different depositional scenarios varves laminae terrigenous flood layers and marine turbidites the concentrations of these pahs were determined using gas chromatography mass spectrometry in selected ion mode and evaluated in terms of their distributions diagnostic ratios and loadings recognized by principal component analysis pca two biogenic pahs perylene and retene provided the greatest variation in their downcore concentration values perylene concentrations increased downcore exhibiting markedly higher abundance in sediments older than 300 ce consistent with the interpretation that perylene is formed diagenetically in reducing sediments a modest increase in perylene concentrations in sediments from the late 1960s may be associated with flood derived transport of higher amounts of degraded terrestrial organic matter from fire denudated landscapes into the coastal environment the markedly higher concentrations of retene in flood layers and turbidites relative to varves laminae suggest that these lithologies are more effective in transporting pyrogenic pahs and can be interpreted as a proxy for wildfires in sbb changes in key diagnostic ratios reveal the shift from a dominance of petrogenic pahs in older sediments to a strong pyrogenic signal beginning in the latter half of the 20th century statistical analysis using pca of the pah distributions in the samples revealed that modern sediments showed a strong positive relationship with pc1 which represents the greatest variation among the samples whereas flood layers showed a strong relationship with the second major variable pc2 thus statistical approaches provide the capability to elucidate modern anthropogenic signatures within the complex pah distributions of sbb and also establish a pah profile that characterizes the lithological signature of flood layers

ghost shrimps decapoda axiidea callianassidae as producers of an upper miocene trace fossil association from sublittoral deposits of lake pannon vienna basin slovakia numerous trace fossils are described from the late miocene sediments of the bzenec formation exposed at the gbely section the vienna basin slovakia during deposition of the sediments the area was part of the large long lived brackish to freshwater lake pannon most of the trace fossils are attributed herein to egbellichnus jordidegiberti igen et ispec nov and are interpreted as burrows produced by decapod crustaceans specifically by a ghost shrimp of the family callianassidae this interpretation is based on two independent lines of evidence environmental requirements of large bioturbators and the burrow morphology itself the new ichnotaxon is distinguished from other related ichnotaxa by a combination of typically inclined roughly at an angle of 45 cylindrical burrows absence of lining and tunnels making loops or bends at approximately right angles the burrow systems at gbely document the survival of ghost shrimp long after the closure of all seaways and the origin of lake pannon as today no ghost shrimp are known from long lived brackish lakes egbellichnus from gbely is the only although indirect record of ghost shrimp from a brackish lake environment reported so far

reactive iron in marine sediments abstract a combined field laboratory study has been undertaken to explore the mineralogy concentrations and reactivity towards sulfide of iron in marine sediments also considered is the importance of bacterial fe liberation in regulating pore water chemistry two contrasting marine environments are included one is the relatively fe poor foam site and the other is the fe rich sediment of the subaqueous mississippi delta results show that oxide minerals are the most important fe phases in early diagenetic pyrite formation however viewed separately lepidocrocite and ferrihydrite are more reactive towards sulfide than goethite and hematite when fe oxides are present in relatively high concentrations dissolved sulfide is nearly absent from sediment pore waters with concomitant high concentrations of dissolved fe even in the presence of active sulfide production by sulfate reduction a combination of experimental results and diagenetic modelling shows that in some sediments pore water fe finds it origin in the bacterial reduction of iron oxides this seems the case even though greater amounts of fe are reduced by reaction of sulfide with iron oxides it appears that distinct microenvironments may exist in marine sediments where in one microenvironment sulfide reacts with fe oxides locally precipitating fe sulfide minerals in another fe reduced and solubilized by microorganisms migrates freely into solution

separation and recovery of various sulphur species in sedimentary rocks for stable sulphur isotopic determination abstract existing methods to extract particular forms of sulphur in rocks and sediments are reviewed and evaluated for application in a chemical scheme to recover sulphur as either ag2s or baso4 precipitates for isotopic analysis the s species distinguished include acid soluble sulphides and sulphates elemental s pyrite barite and various categories of organically bound s there is no evidence of cross contamination or isotopic fractionation during the separation as applied to mixtures synthesized from internal control samples the precision obtained on repetitive extractions is equivalent to that of the measurement technique itself typically 0 2 in the 34s value the chemical separation scheme is demonstrated by application to sections of peat collected from the howards pass xy deposit in the yukon territory canada

el nino in santa barbara basin diatom radiolarian and foraminiferan responses to the 1983 el nino event abstract santa barbara basin box cores collected in august of 1985 were sub sampled and processed in search of microfossil evidence of the 1983 el nino microplankton and microbenthos indicate the presence of that el nino bounded by non el nino conditions specifically the event is recognized by an increase in diatom diversity and the presence of several warm water taxa e g coscinodiscus plicatoides hemidiscus cuneiformis nitzschia kolaczekii pseudoeunotia doliolus thalassiosira lineata thalassiosira nodulolineata an increase in polycystine radiolarian flux and the presence of the eastern tropical pacific species spongaster pentas an increase in the diversity of planktonic foraminifera and the occurrence of the warm water species globoturborotalita rubescens there is also evidence for an oxygenation of the basin during the 1983 el nino as suggested by the increase in the abundance of the benthic foraminifera bolivina vaughani and by the decrease in the preservation of phaeodarian radiolarian spines which are best preserved under anoxic conditions a new onboard procedure for sampling of box cores and freezing of subcores is described

a study of sulphur enrichment in the humic fraction of marine sediments during early diagenesis abstract the evolution of the sulphur content of humic acids extracted from a near shore sediment core was investigated special attention was taken to avoid s contamination of the humic materials during extraction the s c ratios increased continuously with depth to values which strongly suggest s addition to the humic matrix during early diagenesis by reactions between organic matter and h2s or its oxidation products their light isotopic composition supports this view however subsequent isotopic exchange has obscured the mechanism initially involved since a large fraction of the enrichment occurred above the sulphidic zone redox boundaries such as the interface of anoxic microniches within more oxidized zones or the sulphidic suboxic boundary of the sediment column must have been important sites for s addition bioturbation by increasing the contact between sedimentary zones of a different redox regime will likely enhance such processes

nitrogen cycling in the sediments of santa barbara basin and eastern subtropical north pacific nitrogen isotopes diagenesis and possible chemosymbiosis between two lithotrophs thioploca and anammox riding on a glider abstract this article presents data on the isotopic composition of pore water ammonium and n org in the anoxic sediments of the santa barbara basin and the eastern subtropical north pacific esnp region ammonium 15 n behaves differently in the two regions reflecting variability in bacterial processes of sedimentary nitrogen cycling in santa barbara basin stoichiometry of tco 2 and nh 4 production defined by pore water chemistry indicates that the only reaction influencing pore water ammonium concentration in these sediments appears to be organic matter decomposition pore water ammonium was found to be 1 3 heavier than decomposing organic matter in contrast the upper 15 30 cm of esnp pore waters have ammonium with 15 n that is more than 10 heavier than decomposing organic matter at greater depth the 15 n of deeper pore waters approaches that of decomposing organic matter mass balance calculations indicate that the observed isotopic enrichment is not due to the preferential loss of isotopically enriched organic matter pore water profiles show that the zone with heavy isotopes is characterized by a tco 2 nh 4 inputs ratio of 4 or less we attribute this to the presence of thioploca bacteria who transport no 3 to depth and reduce it to nh 4 while oxidizing sulfide based on pore water stoichiometry and reaction diffusion modeling of pore water isotopic composition we propose that the 15 n enriched ammonium is produced as the result of chemosymbiosis between thioploca and anammox like bacteria in these sediments our work provides the new insights into benthic microbial ecology and the role of coupled individual metabolic pathways in sedimentary nitrogen cycling in santa barbara basin factors which contribute to the isotopic fractionation of 1 3 between pore water ammonium and solid n org were also considered in this sediments 23 of the rain of organic nitrogen is lost to diagenesis therefore the isotopic effect of degradation on the residual n org is estimated to be small 0 7 the most likely cause of fractionation is preferential degradation of an isotopically heavier more labile marine fraction relative to an isotopically lighter more refractory terrestrial component of the organic matter but other possibilities cannot be ruled out when corrected for the observed fractionation it appears that the 15 n of these sediments may represent non steady state conditions

high resolution geochemistry and sequence stratigraphy of the hushpuckney shale swope formation eastern kansas implications for climato environmental dynamics of the late pennsylvanian midcontinent seaway abstract the hushpuckney shale member of the swope formation missourian stage eastern kansas is the core shale of a kansas type cyclothem formed during the late transgressive to early regressive phases of a late pennsylvanian glacio eustatic cycle coeval high frequency climato environmental dynamics of the midcontinent seaway are preserved in the kgs orville edmonds no 1a study core as centimeter scale variation in major components organic carbon authigenic sulfides and phosphate detrital siliciclastics organic macerals trace element redox proxies mo u v zn and ichnofabric features benthic o 2 levels declined sharply from the base of the black shale 0 cm went sulfidic at 4 cm and reached a redox minimum at 21 cm above this level redox potential gradually rose fluctuating between sulfidic and nonsulfidic conditions from 35 cm to the black shale gray shale contact at 52 cm onset of dysoxic conditions at that contact allowed establishment of a benthic community of soft bodied organisms comprised of deep tiered tracemakers tolerant of low o 2 conditions trichichnus and shallow tiered tracemakers favoring soupground helminthopsis or firmground substrates the zoophycos phycosiphon schaubcylindrichnus planolites association most geochemical records exhibit a low order cycle spanning the full 52 cm thickness of the black shale submember reflecting a dominant glacio eustatic control the base and top of the black shale submember record lateral migration of the pycnocline across the midcontinent shelf during the transgressive and regressive phases respectively the maximum flooding surface mfs is at 17 23 cm an interval containing the euxinic peak and characterized by high concentrations of illite representing a cratonic siliciclastic flux and terrestrial organic macerals the product of transient increases in humidity weathering rates and the export of coal swamp vegetation associated with the interglacial highstand of the swope cyclothem although a transgressive surface of maximum starvation sms cannot be confidently identified a phosphate rich regressive condensation surface at 28 34 cm records pycnoclinal weakening due to increased aridity associated with renewed southern hemisphere icesheet growth a correlative shift in dominance from terrestrial to marine derived organic macerals reflects increased upwelling of nutrient rich deepwaters and enhanced primary productivity penecontemporaneous paleogeographic and climatic factors e g semirestricted circulation monsoonal precipitation predisposed the midcontinent seaway toward sensitivity to high frequency climato environmental fluctuations which are preserved as 2 to 7 cm thick cycles in the study core the 52 cm thick black shale submember contains 12 such high order cycles which have an estimated average duration of 2 to 9 kyr implying a sub milankovitch band i e millennial scale climatic control the results of this study are relevant to the sequence stratigraphic interpretation of kansas type cyclothems the dynamics of gondwanan ice age glacio eustatic cycles and the development of boundary conditions for late pennsylvanian paleoclimate models

historical oceanographic events reflected in13c 12c ratio of total organic carbon in laminated santa barbara basin sediment an 1844 1987 time series of carbon stable isotope ratios from dated sedimentary total organic carbon toc from the center of the santa barbara basin sbb is compared with historical climate and oceanographic records four isotopically distinct biogeochemical sources of toc are important phytoplankton derived marine biomass macroalgal biomass from kelp forests terrigenous biomass mainly flushed into the sbb via river discharge and redeposited fossil organic carbon the significance of the latter two sources is largely limited to a few unusual flood and oil spill events whereas the combination of 13c depleted phytoplankton and 13c enriched macroalgal biomass appears to be responsible for most of the isotopic variance of the marine coastal biomass as recorded in sedimentary toc the isotopic response of marine organic carbon in sediments records strong el nino southern oscillation enso and the frequently associated severe storm and wave events in sbb varved sediments the plausible major isotopic mechanisms are 1 increased physical liberation of 13c enriched kelp carbon from locally abundant giant kelp macrocystis spp forests during times of physical and environmental stress and 2 decreased productivity of 13c depleted phytoplankton during enso events