long chain alkenone patterns in the baltic sea an ocean freshwater transition two different patterns of long chain alkenones are found in surficial sediments of the baltic sea which is the largest brackish water body on earth one pattern occurs in surficial sediments from the western baltic sea where surface water salinitiy is in excess of 7 7 psu it corresponds to the pattern produced by the marine coccolithophorid emiliania huxleyi with a suite of c37 di to tetra unsaturated methyl ketones and c38 di and tri unsaturated methyl and ethyl ketones a second pattern resembling that found in lake sediments in lacking c38 methyl ketones and having distinctly higher c37 4 methyl ketone concentrations dominates in surficial sediments of the eastern and northern baltic sea where salinities are lower than 7 7 psu correspondence of sea surface temperature sst estimates from the u37 and u379 indices using marine calibrations with mean sst in the euphotic zone from july august the main haptophyte growth season is poor thus these indices are not applicable as sedimentary thermometers in surficial sediments of the baltic sea the different patterns may either reflect the salinity dependent occurrence of specific alkenone producers or changes in the alkenone biosynthesis due to physiological stress caused by salinity variations furthermore advection of saline and oxygenated north sea water may transport marine algal material characterized by a marine e huxleyi like alkenone pattern into the western baltic sea thus covering the signature of the local alkenone producers with a baltic sea pattern copyright 2000 elsevier science ltd

an effect of dissolved nutrient concentrations on alkenone based temperature estimates the ratio of 37 carbon diunsaturated to diunsaturated and triunsaturated alkenones uk 37 produced by some haptophytes is widely used as a proxy for past sea surface temperatures however our isothermal culturing experiments with emiliania huxleyi clone ccmp372 show uk 37 values to also vary with nutrient availability and cell division rate these results provide a reasonable explanation for large isothermal variation in uk 37 values of single coccolithophorid strains grown in culture they also suggest that alkenone based estimates of past sea surface temperatures may have been influenced by dissolved nutrient concentrations as well as by temperature

recent environmental changes recorded in anoxic barsnesfjord sediments western norway abstract four high quality gravity cores and five box cores up to 2 3 m long from the land locked silled and anoxic barsnesfjord in western norway contained three different sediment sequences these were alternating thick dark and light layers fine scaled laminated sections and grayish brownish layers dominated by minerogenic grains accurate sedimentation rates over the last 150 years were determined using three different techniques 137 cs dating occurrence of historically documented slide slump events and counting of seasonal sediment layers bulk sediment and organic carbon accumulation rates in the outer and inner fjord basin decreased by over 30 when values of the last century pre 1904 are compared with those of this century 1904 1986 this significant change is attributed to the damming of the hafslovatn in 1904 no significant change in these values was observed after regulation of the veitastrondsvatn in 1982 and after the 2nd damming of the hafslovatn in connection with the construction of the aroy electrical power plant in 1983 zn and cu accumulation over the same time periods remained constant

organic carbon burial in fjords terrestrial versus marine inputs abstract fjords have been identified as sites of enhanced organic carbon oc burial and may play an important role in regulating climate change on glacial interglacial timescales understanding sediment processes and sources of sedimentary oc are necessary to better constrain oc burial in fjords in this study we use fiordland new zealand as a case study and present data on surface sediments sediment down cores and terrestrial end members to examine dynamics of sediments and the sources of oc in fjord sediments sediment cores showed evidence of multiple particle sources frequent bioturbation and mass wasting events a multi proxy approach stable isotopes lignin phenols and fatty acids allowed for separation of marine soil and vascular plant oc in surface sediments the relationship between mass accumulation rate mar and oc contents in fjord surface sediments suggested that mineral dilution is important in controlling oc content on a global scale but is less important for specific regions e g new zealand the inconsistency of oc budgets calculated by using mar weighted oc and oc accumulation rates ar 6 vs 21 31 tg oc yr 1 suggested that sediment flux in fjords was likely underestimated by using end member models we propose that 55 to 62 of total oc buried in fjords is terrestrially derived and accounts for 17 12 of the octerr buried in all marine sediments the strong correlation between mar and oc ar indicated that oc flux will likely decrease in fjords in the future with global warming due to decrease in sediment flux caused by glacier denudation

a 400 year record of environmental change in an euxinic fjord as revealed by the sedimentary biomarker record a 400 year sedimentary record of the euxinic kyllaren fjord was investigated using organic biogeochemical geochemical and sedimentological approaches accumulation rates of a suite of biomarkers and in some cases their stable carbon isotopic composition were determined biomarkers were separated into three different groups terrestrial derived general aquatic marine derived and aquatic marine derived but related to high primary productivity variations in bulk sediment parameters and biomarker accumulation rates with depth were used to interpret the sedimentary record we infer that in the first half of the 19th century an environmental change occurred caused by a change in either the precipitation regime vegetation and or land use the data also show that in the last century and especially in the last decades a distinct increase in primary productivity occurred most likely this is caused by a natural eutrophication due to the transformation of the fjord from an open to a confined system by the building of a partially open dam in 1954 possibly combined with anthropogenic eutrophication a concurrent shoaling of the fjord chemocline may have had a mediating effect in the change towards a higher productivity by enhancing nutrient and carbon recycling enhanced carbon recycling is reflected by decreased 13c values of several biomarkers

high resolution holocene vegetation history and climate from hole 1034b odp leg 169s saanich inlet canada abstract high resolution pollen analysis of laminated marine sediments from odp hole 1034b in saanich inlet british columbia reveals changes in vegetation and inferred climate during the holocene four main pollen zones are discerned using constrained cluster analysis although the timing of major vegetation changes at the saanich inlet is similar to other study sites in the pacific northwest the composition of pollen assemblage zones is different from the mainland sites vegetation assemblages reconstructed from the pollen and spore record include a douglas fir pseudotsuga menziesii parkland with abundant grass poaceae and bracken pteridium between 11 450 and 8300 bp all ages are calibrated calendar years oak quercus savanna or parkland with high grass and bracken 8300 7040 bp a mixed deciduous coniferous forest with oak western hemlock tsuga heterophylla and douglas fir 7040 5750 bp and the development of modern coastal temperate forest with the marked expansion of cedar cupressaceae western hemlock spruce picea and douglas fir 5750 1050 bp climatic periods inferred from the cores include an early holocene warm dry interval 11 450 8300 bp a warm period with mild winters 8300 7040 bp a period of transitional mid holocene climate 7040 5750 bp and the advent of a relatively cool wet neoglacial climate after 5750 bp modern conifer forests and oak savannas became established by about 3800 bp the saanich inlet pollen record indicates that vegetation and inferred climate change was particularly rapid between 8700 and 8300 bp when grass and bracken abruptly decrease and oak becomes a significant component of the paleovegetation because neoglacial conditions have prevailed from 3800 years to present in the pacific northwest factors other than climate such as anthropogenic modification of the landscape may be responsible for the persistence of oak savannas

a review of coastal palaeoclimate and relative sea level reconstructions using δ13c and c n ratios in organic material holocene reconstructions of relative sea level rsl and environmental change in the coastal zone have become progressively more numerous since the importance of assessing possible future sea level rises has become apparent traditionally this has been achieved using a combination of biological and physical indicators e g pollen diatoms foraminifera grain size etc in some circumstances microfossils can be rare or absent from holocene sediments and in these cases carbon isotope ratios 13c and organic carbon to total nitrogen ratios c n can be used because they have the potential to provide information as to the origin of organic material preserved in coastal environments the distinction in 13c and c n of the various sources of carbon to estuarine sediments has led to its wide use as a tracer of carbon pathways and storage in estuaries more recently these techniques have been applied to holocene sediments to decipher changes in palaeocoastal environments and thus position relative to sea level and or palaeoriver discharge which have direct relevance to palaeoclimate this paper reviews the studies that have utilised this technique and explores examples from a wide range of coastal environments saltmarshes estuaries lagoons isolation basins and fjords it also discusses the potential alteration of geochemical signatures as a result of decompositional processes organic matter decomposition has been shown to change sediment 13c and c n values and thus an understanding of the processes involved is necessary in order to have confidence in the palaeoenvironmental interpretation of holocene 13c and c n decompositional shifts in c n and particularly 13c can occur over a relatively short time period however it is the direction of change in 13c and c n rather than absolute values that is key for interpreting changes in relative sea level and thus such changes are commonly preserved

δ13c values and radiocarbon dates of microbial biomarkers as tracers for carbon recycling in peat deposits this paper describes the first application of compound specific stable carbon isotope and radiocarbon isotope analyses to the investigation of microbial processes in peat deposits

uranium and molybdenum isotope systematics in modern euxinic basins case studies from the central baltic sea and the kyllaren fjord norway abstract recent investigations have revealed significant fractionation of 238u 235u between organic rich sediments of anoxic marginal seas and seawater indicating redox dependent u isotope fractionation this study explores the conditions controlling u isotope fractionation in selected modern anoxic basins baltic sea landsort and gotland deeps and the kyllaren fjord in norway and compares u with mo isotope fractionation therefore the concentrations and isotope compositions of dissolved u and mo from the water column and organic rich sediments from three currently anoxic basins have been analysed the water column samples from the kyllaren fjord display a moderate depletion of u and a strong depletion of mo with increasing depth these variations are associated with a decrease in 238u and an increase in 98mo with depth from 0 35 to 0 70 and from 2 4 to 2 6 respectively from the u isotope composition of the deep euxinic water column of the kyllaren fjord a minimum value of 238ured 0 7 for the u isotope fractionation during reduction is inferred due to the high sedimentation rate in the kyllaren fjord surface sediment samples are only moderately enriched in u and mo 4 g g and 6 g g to 37 g g respectively and display 238u and 98mo averages of 0 26 0 10 and 2 18 0 21 respectively water column samples from the baltic sea display a minor decrease in the u and mo concentrations and only negligible u and mo isotope fractionation compared to open seawater the sediment layers from the baltic sea landsort deep which were deposited under mostly anoxic conditions are moderately enriched in u up to 8 g g and highly enriched in mo up to 222 g g however u and mo isotopic compositions are significantly lighter with 238u of 0 36 0 08 and 98mo of 0 04 0 11 than those of typical organic rich sediments from anoxic basins these findings reveal that compared to mo the u isotopic composition of sediments in restricted and strongly euxinic basins like the kyllaren fjord is significantly more dependent on 1 the extent of u removal from the water column which is lower than that of mo and on 2 the sedimentation rate i e the fraction of authigenic u relative to detrital u in the sediment which is also lower compared to that of mo in more open and only temporarily euxinic basins such as the investigated basins of the baltic sea strong mo is coupled with weak u isotope fractionation between water and sediment these signatures were likely the result of isotope fractionation under weakly sulfidic conditions and the generation of isotopically light mo during frequently occurring flushing events with oxygen rich water from the open sea this implies that mo and u isotope signatures of sediments only record paleo water column redox conditions of restricted basins if the water column was permanently stratified

records of southern and central baltic sea eutrophication in δ 13 c and δ 15 n of sedimentary organic matter abstract the baltic sea catchment area has seen considerable agricultural and industrial development over the last century but observational evidence of eutrophication is ambiguous we examined organic carbon accumulation rates and the stable isotope signature of 13 c and 15 n in organic matter in four 210 pb dated short sediment cores from the southern and central baltic sea to search for sedimentary records of increased nutrient input and biological production organic carbon accumulation rates vary little through time in the cores from the oder estuary and the arkona basin but increase significantly in the bornholm basin and in the gotland deep records over the last 40 years 15 n in the sediments show distinct increases over the last 80 50 years in the oder estuary arkona basin and bornholm basin with the greatest increase near the mouth of river oder the gotland deep record shows increasing 15 n values from 1900 to 1975 and decreased 15 n values during the last 20 years the 15 n records are interpreted to trace the effects of eutrophication in nearshore and basinal sediments over the last 100 years and the magnitude of 15 n increase may be a measure for its extent the switch to lower 15 n values in the gotland basin sediment core after initially increasing values coincides with increasing abundance of summer blooms of nitrogen fixing cyanobacteria as observed in monitoring programs 13 c toc values of organic matter increase in the oder estuary over the last 80 years and over the last 30 years in the bornholm basin and gotland basin the tendency to heavier 13 c indicates decreasing isotope fractionation during massive plankton blooms that this effect is not well documented in the sediments of the arkona basin may be due to enhanced degradation processes in the permanently mixed water column a comparison of organic carbon concentrations and 13 c toc and 15 n from early litorina stage around 7 000 years bp and modern sediments from the gotland sea suggests that the trophic state of the baltic sea was comparable to that of the modern environment productivity was nitrate based in spring and based on nitrogen fixation in summer much higher organic carbon concentrations and 13 c enrichment in modern sediments are indications of enhanced productivity compared to early litorina times

a first look at paleotemperature prospects from mg in coccolith carbonate cleaning techniques and culture measurements 1 although coccolith calcite is abundant in carbonate sediments it has not been previously utilized for mg ca paleothermometry cleaning experiments with synthetic composite samples reagent caco3 powder and organic matter from noncalcifying marine algae chlorella are used to evaluate which traditional and or novel cleaning methods permit us to recover the known carbonate mg ca ratio the most effective cleaning treatment causing the least effect on carbonate chemistry and most complete and rapid oxidation of algal organic matter was oxidation in an equal volume mixture of sodium hypochlorite 2 8 and hydrogen peroxide 30 however in some organic rich samples this method may not remove sufficient noncarbonate mg to permit precise determination of carbonate mg ca mg ca ratios in small culture samples may be determined precisely relative standard deviation of 0 65 using sector field inductively coupled plasma mass spectrometry measurements of mg ca in coccoliths from several species suggest that temperature may be an important control over mg partitioning in coccolith calcite although cleaning issues are likely to be an important limitation on paleoceanographic application

long chain alkenones in qinghai lake sediments abstract long chain methyl and ethyl alkenones c 37 c 40 containing two to four double bonds have been detected in sediments from qinghai lake china this is the first report of the alkenones in lake sediments deposited under a variety of salinity conditions where the lake has not encountered any marine incursions the presence of the alkenones suggests the presence of prymnesiophyceae in the lake which may have reached the lake via eolian transportation or seabirds sediment samples from the more saline areas of the lake contained higher concentrations of the more highly unsaturated compounds widespread use of these compounds as paleotemperature indicators in marine sediments introduces the possibility of extrapolating this approach to lacustrine environments if appropriate calibrations can be undertaken

distributions of long chain alkenones and alkyl alkenoates in marine surface sediments from the north east atlantic abstract the abundances of long chain alkenones and alkyl alkenoates are reported for a suite of surface sediments from the ne atlantic 0 75 n despite the differing conditions of their biologies and differing extents of water column degradation and of early diagenesis in the sediments the degree of unsaturation of the alkenones e g the u 37 k parameter and the relative proportion of alkyl alkenoates to alkenones display linear correlations with average temperature for surface waters warmer than 5 c there is evidence that the chain length distribution of the alkenones and of the ratio between the ethyl and methyl c 38 alkenones are species dependent which would enable their use as chemotaxonomic tools

correlation of bulk sedimentary and compound specific δ 13 c values indicates minimal pre aging of n alkanes in a small tropical watershed abstract inherent to sedimentary compound specific isotopic proxies of paleoecological and paleoclimate change is the assumption that biomarkers are coeval with the surrounding sedimentary matrix compound specific radiocarbon analyses of lake and nearshore marine sediments have indicated a potential offset between the ages of terrestrial biomarkers and their surrounding sediments that could confound efforts to establish strong chronological control for compound specific isotopic data we conducted high resolution compound specific 13c analyses of n alkanes 13calkane in a well studied sediment core from laguna castilla dominican republic and compared the results to bulk sedimentary 13c 13cbulk fossil pollen and sediment geochemistry to assess potential pre aging of alkanes in the terrestrial environment prior to deposition we found significant positive correlations between 13cbulk values and 13calkane values indicating little or no temporal lag in the response of 13calkane values to vegetation change and thus little or no offset in the age of terrestrially derived compounds and the organic fraction of the sedimentary matrix while this study highlights the need for further research into the variables affecting age offsets between proxy data we propose the comparison of 13cbulk and 13calkane values as a method to assess potential age offsets between compound specific and other proxy datasets particularly in small watersheds with sediment records containing a high proportion of allochthonous organic matter this method is more available to researchers than obtaining numerous compound specific radiocarbon analyses which are costly and not a routine service offered by radiocarbon facilities

coccolith sr ca as a new indicator of coccolithophorid calcification and growth rate 1 polyspecific coccolith separates from core top sediments in the eastern equatorial pacific show variations of 15 in sr ca ratios across the equatorial upwelling zone with sr ca highest at the equator and decreasing off axis these variations cannot be due to changes in the sr ca of seawater which varies by less than 2 in the surface ocean variations in sr ca of coccolith sediments are similar to variations in primary productivity and alkenone estimated coccolithophorid growth rates in overlying surface waters and to caco3 rain rates measured in sediment traps because of these relationships and because calcification rate exerts a strong control on sr ca in abiogenic calcites we suggest that the observed sr ca variations in coccoliths may be strongly controlled by coccolithophorid growth and calcification rates although temperature may also influence coccolith sr ca to a lesser degree changes in dissolution intensity and coccolith assemblages appear to exert a minor influence if any on coccolith sr ca in these sediment core tops if further work confirms relationships between coccolith sr ca and coccolithophorid productivity sr ca records of past changes in coccolithophorid productivity may be useful in reconstructing past variations in the rain ratio of organic to carbonate carbon an important control on deep ocean ph and partitioning of co2 between the atmosphere and ocean in addition coccolith sr ca might provide an independent record of past changes in coccolithophorid growth rates which in combination with data on the carbon isotopic fractionation in coccolithophorid organic matter may permit more reliable calculations of past dissolved co2 in the surface ocean

the alkenone temperature signal in western north atlantic surface waters abstract haptophyte algae derived long chain c 37 c 39 alkenones and alkyl alkenoates were analyzed in euphotic zone particulate matter collected over a 7 yr period at the oceanic flux program bermuda atlantic time series ofp bats site in the western sargasso sea surface water temperatures at the site range annually from 19 to 29 c alkenone concentrations ranged from 1 in summer to 100 ng l 1 following the passage of storms highest seasonal concentrations occurred during the late winter and spring under stratified conditions alkenone concentrations in the surface mixed layer 0 20 m were generally 2 to 4 times higher than in the deep fluorescent maximum 75 110 m consistent with emiliania huxleyi concentration profiles haidar and thierstein 2001 and indicated that alkenone production primarily occurs within the upper euphotic zone in this region alkenone compound distributions and the temperature calibrations of c 37 and c 38 methyl and ethyl alkenone unsaturation u 37 k u 38me k and u 38et k respectively were remarkably similar to that observed in an e huxleyi strain previously isolated from the same area conte et al 1998 providing strong evidence that e huxleyi is the predominant alkenone synthesizer and that characteristics exhibited by randomly isolated clones in culture are in many cases consistent with those of populations in the region of origin the bermuda calibration of u 37 k vs water temperature u 37 k 1 9835 0 2004t 0 0034t 2 r 2 0 95 n 91 is nonlinear and falls along the same trendline as euphotic zone particulates from warm 15 c waters of the eastern north atlantic conte and eglinton 1993 and mediterranean ternois et al 1997 the combined north atlantic temperature calibration u 37 k 1 1365 0 1257t 0 0018t 2 r 2 0 963 n 134 differs significantly from published coretop sediment calibrations rosell mele et al 1995 muller et al 1998 based on sea surface temperature maps levitus and boyer 1994 having a steeper slope at temperatures 24 c the reasons are not clearly apparent and manifest a need for detailed studies linking production patterns in surface waters with the signal arriving at the seafloor to fully understand the generation of the sedimentary signal

diagenesis of free and bound lipids in terrestrial detritus deposited in a lacustrine sediment recent sediments from an oligotrophic lake loch clair having uniform organic input for 2000 yr show changes in lipid abundance and composition with increasing depth attributed to diagenesis stability of free lipids decreases in the order n alkanes alkan 2 ones sterols n alkanoic acids n alkanols n alkenoic acids diagenetic loss of shorter chain homologues is complete within 400 yr stabilisation of bound relative to free lipids increases the proportion of the former with sediment age and reduces loss of shorter chain bound homologues in an eutrophic lake cross mere shorter chain free and bound sedimentary lipids show increased abundance compared with loch clair the relative importance of higher input of shorter chain lipids derived from aquatic detritus and slower initial diagenesis due to the anoxic hypolimnion as causative factors for this difference between lake types cannot yet be assessed

extended hopanoids in peat environments abstract detailed results are presented for the distributions of triterpenoid alkanes acids and alcohols of the hopane family in ten samples of peat from three environments and of contributing organisms in the case of lyne of skene scotland extended hopanoids of the and configuration appear at the very earliest stage of diagenesis such environments appear to be characterised by particular distributions of c 32 hopanoid acids and alcohols and a high preponderance of the c 31 hopane

pre and post industrial environmental changes as revealed by the biogeochemical sedimentary record of drammensfjord norway the biogeochemical sedimentary record of the anoxic drammensfjord norway was investigated on a decadal to centennial time scale over the last millennium in order to reconstruct the pre industrial fjord environment and ecosystem and human induced environmental changes the sediments were dated by a combination of 14c and 210pb analysis and varve counting analysis of the bulk sedimentary parameters and of the biomarker distribution revealed that the sedimentary organic matter of the fjord is primarily of terrigenous origin indicating that the fjord was oligotrophic or mesotrophic the fjord s bottom water has been continuously euxinic since at least 1000 ad but photic zone euxinia occurred only irregularly in the fjord the organic matter flux and composition remained virtually invariable until the 18th century after that time the flux of material derived from coniferous trees started to increase indicated by elevated concentrations of dehydroabietic acid and related compounds but also by raising levels of c24 n alcohols and fatty acids this marked the onset of sawmill activities in the hinterland after the beginning of the industrial revolution around 1850 the flux of organic waste from sawmills and paper mills increased substantially it is suggested that slow bacterial degradation of this relatively nutrient poor organic waste caused a gradual eutrophication trend which is reflected in substantial increased bacterial and moderately increased other aquatic biomarker accumulation rates after the industrial revolution this trend accelerated and was possibly enhanced by a growing population of the area with accompanying agricultural and domestic waste this promoted primary productivity and changed the phytoplankton composition in the fjord

unusual distributions of long chain alkenones and tetrahymanol from the highly alkaline lake van turkey long chain c37 to c40 alkenones with di tri and tetra unsaturation are very abundant in sediment trap material and holocene to late pleistocene core samples from the earth s largest soda lake lake van turkey thus the known distribution range of these typical biomarkers for haptophyte microalgae is extended to highly alkaline environments the observed unsaturation patterns differ strikingly from those found in open marine haptophytes and sediments by an enhanced relative abundance of the tetra unsaturated compounds especially the c37 4 methyl ketone their preponderance is suggested to be a facies marker pattern for lacustrine and marginal marine areas of sedimentation using published u37k calibrations no reliable absolute temperatures were obtained for the lake van samples accordingly marine sea surface temperature determinations based on long chain alkenones should be applied with caution when a contribution of these compounds from coastal or nonmarine sources can not be excluded the presence of tetrahymanol and gammacer 3 one in the lake van materials is attributed to organic matter contributions of ciliates the relative abundance of long chain alkenones and of tetrahymanol gammacer 3 one is considered to reflect changes in the environmental conditions in particular in the hydrological setting we suggest that times of pronounced stagnation are recognised by very high tetrahymanol gammacer 3 one concentrations together with drastically increased stanol stenol ratios and intervals of enhanced convection or of high freshwater input are characterised by high alkenone contributions

the biogeochemistry of ellesmere lake u k i source correlation of leaf wax inputs to the sedimentary lipid record abstract analyses of the free lipid distributions from ellesmere lake sediments taken from two depths and comparison with leaf wax lipid distributions from six deciduous tree species around the lake were made in order to assess lipid sources close correlations of aliphatic lipid distributions in the carbon number range c 20 c 50 were seen c 28 and c 29 sterols were observed in both sediment and leaf waxes but c 27 sterols were only present in the sediments and were thus assigned a nonleaf wax source unsaturated steroidal ketones were observed both in the sediment and in certain leaf waxes and were assigned specific sources alkan 2 ones were not present in the leaf waxes but were present in the sediment samples with an almost identical distribution to the sediment n alkanes indicating a microbially mediated source c 20 c 30 n aldehydes which have not previously been widely reported in free lipid distributions of freshwater lacustrine sediments were prominent in the surface sediment and in the leaf waxes examined

redox and paleoenvironmental conditions of the devonian carboniferous sappington formation southwestern montana and comparison to the bakken formation williston basin abstract the sappington formation outcrops in southwestern montana and spans the upper devonian lower mississippian transition it consists of two carbonaceous shale intervals one upper and one lower and a middle dolomitic siltstone and silty sandstone it was deposited in a relatively small basin with the central montana uplift separating the sappington basin from the williston basin to the east which contains the economically important bakken formation previous biostratigraphic and lithostratigraphic comparisons have identified the sappington and bakken formations as depositionally contemporaneous and due to the subsurface nature of the bakken the sappington has emerged as a useful outcrop analogue this study presents new geochemical data from the sappington formation providing a comparison to the bakken and insight into paleo redox conditions during the devonian carboniferous on the western laurentian margin geochemical signals in the sappington formation outcrop samples are partially obscured by oxidative weathering but similar to the lower bakken shale the lower sappington shale appears to record dominantly euxinic conditions albeit with intervals when the water column was suboxic to ferruginous and with an absence of organic or inorganic geochemical evidence for photic zone euxinia the upper sappington shale appears to have been deposited in ferruginous to dysoxic conditions thus the sappington appears to be an excellent analogue to the bakken on a lithostratigraphic level but the geochemical environment for black shales source rock deposition appears less reducing closer proximity to the open ocean and consequent lower levels of restriction may have been responsible for these redox differences however sappington core samples and an increased focus on integrating geochemical data into the regional stratigraphic record will be necessary to further understand paleoceanographic and biogeochemical drivers

distribution and significance of long chain alkenones as salinity and temperature indicators in spanish saline lake sediments abstract we investigated relationships between sedimentary solvent extractable long chain alkenone lca concentration and composition and environmental factors in a suite of endorheic lakes from inland spain lcas were found in 14 of the 54 lakes examined with concentrations comparable with those from previously published lacustrine settings the composition of lcas in our sites however contrast from the majority of those previously reported from lake environments in our study the tri unsaturated component is the most abundant component at most sites where lcas are detected and c38 3 is the most abundant lca in the majority of sites lca occurrence appears to be restricted to brackish hypersaline sites and c37 lcas are absent above a salinity of 40 g l 1 suggesting a salinity control on lca producing organisms in these sites low concentrations of c37 lca components means u 37 k and u 37 k temperature indices are generally not applicable instead we find good relationships between c38 components and in particular mean autumn temperature and the strongest lca temperature relationships are found when using a combination of all c37 and c38 compounds we propose a new alkenone temperature index for lakes with elevated salinity and where the c38 components dominate the lca distributions this is expressed as u 3738 k 0 0464 mautat 0 867 r2 0 80 n 13 in this paper we provide the first account of sedimentary lca distributions from lakes in inland spain extending the range of environments within which these compounds have been found and highlighting their significance as indicators of both salinity and temperature in saline endorheic lake environments this has important implications for extending the potential role of lcas as palaeoclimatic indicators in lacustrine environments

underestimation of the authigenic fraction of cu and ni in organic rich sediments abstract there are two possible techniques to estimate the degree of authigenic or non lithogenic metal enrichment in sediments first the authigenic metal fraction can be calculated according to m auth m total m al background al total while m is the metal of interest and al is aluminum second a metal enrichment factor ef is calculated according to ef m al total m al background both techniques rely on the appropriate use of the m al ratio of the lithogenic background for the latter the m al ratio of average shale or crust is widely applied as lithogenic background in marine geochemistry however as we show here the lithogenic background based on average shale or crust is too high for cu and ni as a consequence the authigenic fraction of cu and ni in sediments and suspended particulate matter spm is significantly underestimated as shown for examples from various environments upwelling areas of peru chile and the gulf of california the norwegian kyllaren fjord and the german wadden sea by correlating cu al and ni al with toc in the samples the apparent m al ratio of the background can be estimated a prerequisite for this technique is high linearity and high quality of correlation r 2 0 8 otherwise the lithogenic background cannot be exactly determined the resulting higher authigenic level of cu and ni may promote their use as productivity indicators while the status of cu and ni may shift from moderately to highly enriched when the enrichment is assessed via efs

topsoil c n ratios in the qilian mountains area implications for the use of subaqueous sediment c n ratios in paleo environmental reconstructions to indicate organic sources abstract sediment carbon nitrogen c n ratios can play an important role in reconstructing lacustrine and coastal paleo environments because significantly different c n ratios result from aquatic phytoplankton versus organic matter derived from terrestrial plants however researchers have not yet taken into account the fact that topsoil organic matter is another important terrestrial organic source for lacustrine and coastal sediments a study of topsoil c n ratios from the heihe and shiyang river drainage basins located in the qilian mountains on the northeast margins of the tibetan plateau shows that topsoil c n ratios can be as low as those of subaqueous sediments 80 4 of total topsoils in the heihe river drainage basin and 67 7 of total topsoils in the shiyang river drainage basin have c n ratios below 12 while 18 8 of all samples in the heihe river drainage basin and 29 2 of all samples in the shiyang river drainage basin possess c n ratios between 12 and 20 traditionally researchers have considered that low c n ratios indicate subaqueous deposition however these sediments are terrestrial and most of the organic matter is derived from land plants furthermore topsoil c n ratios from both the heihe and shiyang river drainage basins correlate significantly with altitude and local vegetation our results indicate that not all c n ratios of terrestrial organic matter including plants and soil organic matter equal 20 or more nor can one distinguish subaqueous sediment organic sources solely on the basis of c n ratios low subaqueous sediment c n ratios may not simply result from a greater proportion of aquatic plants versus terrestrial organic matter but also from low end member terrestrial organic matter c n ratios which are lowered by the addition of soil organic matter with its own low c n ratios

forecasting the path of a laterally propagating dike an important aspect of eruption forecasting is predicting the path of propagating dikes we show how lateral dike propagation can be forecast using the minimum potential energy principle we compare theory to observed propagation paths of dikes originating at the bar arbunga volcano iceland in 2014 and 1996 by developing a probability distribution for the most likely propagation path the observed propagation paths agree well with the model prediction we nd that topography is very important for the model and our preferred forecasting model considers its in uence on the potential energy change of the crust and magma we tested the in uence of topography by running the model assuming no topography and found that the path of the 2014 dike could not be hindcasted the results suggest that lateral dike propagation is governed not only by deviatoric stresses but also by pressure gradients and gravitational potential energy furthermore the model predicts the formation of curved dikes around cone shaped structures without the assumption of a local deviatoric stress eld we suggest that a likely eruption site for a laterally propagating dike is in topographic lows the method presented here is simple and computationally feasible our results indicate that this kind of a model can be applied to mitigate volcanic hazards in regions where the tectonic setting promotes formation of laterally propagating vertical intrusive sheets

early holocene decadal scale ocean variability recorded in gulf of california laminated sediments scanning electron microscope examination of holocene laminated sediment from guaymas basin gulf of california resolves up to five depositional events per year each lamina sublamina of an early holocene section of continuously laminated sediment was recorded from backscattered electron imagery photomosaic analysis diatom mat laminae composed predominantly of thalassiothrix longissima are associated with early winter mixed diatom flora laminae mats are probably brought into the gulf with pacific water during the summer concentrated at the surface or at the pycnocline and then rapidly deposited in the early winter as water column stratification breaks down time series analysis of one 300 year section from piston core jpc56 revealed significant periodicities in the deposition of mat laminae at 50 years 11 years and 22 24 years an 50 year cycle in fish populations has been related to changing north pacific ocean atmosphere circulation these pacific wide changes in circulation affect the currents dominant at the mouth of the gulf when the california current is dominant fewer diatom mats are imported into the gulf and when the north equatorial pacific gyre is dominant more are imported the 11 year 22 to 24 year and 50 year cycles are all suggested to be influenced by solar cycles

holocene changes in marine productivity and terrestrial organic carbon inputs into an icelandic fjord application of molecular and bulk organic proxies this study examines the dynamics of organic carbon contributions from different sources to the sediments of a 39 m core from isafjar ardjup fjord northwest iceland throughout the holocene furth

early diagenesis of bacteriohopanoids in recent sediments of lake pollen norway abstract the distribution of free bio and geohopanoids were studied in a short 46 cm core from recent sediments of lake pollen norway bacteriohopanepolyols are abundant components of the sediments totalling up to 321 g g dry sediment 7485 g g toc being dominated by c 32 33 34 35 tetrafunctionalised hopanoids significantly bacteriohopanetetrol only accounts for between 7 to 62 of these 24 on average indicating that composite bacteriohopanoids are more abundant sedimentary constituents and thus more important precursors of geohopanoids than previously recognised downcore profiles of bio and geohopanoid abundance show maxima at ca 25 to 30 cm with a marked decrease in abundance above this depth which coincides with a well documented change in environment from fjord to isolated lake a second maximum in biohopanoid abundance occurs at ca 5 to 12 cm depth specific biohopanoids were affected to different extents by the change in environment suggesting that they have at least partly different sources our data thus indicate that biohopanoids and their geohopanoid products may be sensitive to changes in depositional environment and that they have potential to act as markers for environmental conditions

chemoautotrophy in the redox transition zone of the cariaco basin a significant midwater source of organic carbon production during the cariaco time series program microbial standing stocks bacterial production and acetate turnover were consistently elevated in the redox transition zone rtz of the cariaco basin the depth interval 240 450 m of steepest gradient in oxidation reduction potential anomalously high fluxes of particulate carbon were captured in sediment traps below this zone 455 m in 16 of 71 observations here we present new evidence that bacterial chemoautotrophy fueled by reduced sulfur species supports an active secondary microbial food web in the rtz and is potentially a large midwater source of labile chemically unique sedimenting biogenic debris to the basin s interior dissolved inorganic carbon assimilation 27 159 mmol c m 22 d 21 in this zone was equivalent to 10 333 of contemporaneous primary production depending on the season however vertical diffusion rates to the rtz of electron donors and electron acceptors were inadequate to support this production therefore significant lateral intrusions of oxic waters mixing processes or intensive cycling of c s n mn and fe across the rtz are necessary to balance electron equivalents chemoautotrophic production appears to be decoupled temporally from short term surface processes such as seasonal upwelling and blooms and potentially is more responsive to longterm changes in surface productivity and deep water ventilation on interannual to decadal timescales findings suggest that midwater production of organic carbon may contribute a unique signature to the basin s sediment record thereby altering its paleoclimatological interpretation

molecular stratigraphy a new tool for climatic assessment variations in sea surface temperatures over the past 500 000 years are inferred from the relative abundance behaviour of two organic compounds c37 alkenones over the upper 8 metres of a sediment core from the eastern equatorial atlantic this molecular record ascribed to contributions from prymnesiophyte algae correlates well with the variations in the 18 signal for the calcareous skeletons of certain planktonic foraminifera thus providing the first demonstration of a new stratigraphical technique which may be especially valuable where methods based on carbonate 18 fail

carotenoid diagenesis in recent marine sediments ii degradation of fucoxanthin to loliolide abstract the quantitative distributions of loliolide and the major phytoplankton carotenoids fucoxanthin diadinochrome diatoxanthin and carotene in two cores of anoxic marine sediment recovered from the peru continental shelf are reported our results demonstrate that the rapid degradation of carotenoids in sediments is not a result of their high degree of unsaturation as has been previously suggested instead carotenoids exhibit a wide range of degradation rates that are proportional to the ability of specific pigments to form unstable bicyclic furanoxides carotenoid furanoxides undergo subsequent fragmentation to loliolide isololiolide dihydroactinidiolide and other as yet undetermined low molecular weight products this degradation pathway accounts for the relative rates of removal for specific carotenoids fucoxanthin fucoxanthinol diadinoxanthin diatoxanthin carotene the distribution of carotenoids reported by wpatts and maxwell 1977 and c ardoso et al 1978 in ancient sediments the occurrence of novel carotenoid transformation products in surface sediments reported by r pidout et al 1984 and the distribution of loliolides in recent sediments recovered from the namibian shelf reported by k plok et al 1984a b we predict that loliolide and isololiolide will inherit a specific stereochemistry from their carotenoid precursors but that dihydroactinidiolide will be racemic for every mole of fucoxanthin degraded in peru sediments 0 7 1 1 mole of loliolide is produced summation of fucoxanthin and loliolide at each subsurface horizon yields an estimate of the total deposition of fucoxanthin at t 0 throughout the 0 20 cm depth of our samples this parameter is remarkably constant to 16 individual horizons exhibit excursions which may reflect changes in surface productivity extrapolation of our measurements to deeper sediments may therefore be of some value in deciphering questions on environmental conditions of deposition and paleoproductivity

reconstruction of δ13c of chemocline co2 aq in past oceans and lakes using the δ13c of fossil isorenieratene abstract high abundances of the diaromatic carotenoid isorenieratene derived from photosynthetic green sulfur bacteria chlorobiaceae were found just below the chemocline in an anoxic fjord in norway throughout the annual cycle the stable carbon isotope composition of this carotenoid co varied with the 13c of co2 aq and is independent of the co2 and isorenieratene concentration this constant isotopic fractionation p of isorenieratene versus co2 4 1 was subsequently used in the reconstruction of 13c of co2 at the chemocline in ancient oceans and lakes these reconstructions indicate that 13c of co2 at the chemocline is often influenced by isotopically light co2 formed by remineralization of organic matter this process can depending on the depth and stability of the chemocline also effect the isotopic composition of the phytoplankton and thus isotopic records of sedimentary inorganic and organic carbon

organic geochemistry of the early toarcian oceanic anoxic event in hawsker bottoms yorkshire england a comprehensive organic geochemical investigation of the hawsker bottoms outcrop section in yorkshire england has provided new insights about environmental conditions leading into and during the toarcian oceanic anoxic event t oae 183 ma rock eval and molecular analyses demonstrate that the section is uniformly within the early oil window hydrogen index hi organic petrography polycyclic aromatic hydrocarbon pah distributions and tricyclic terpane ratios mark a shift to a lower relative abundance of terrigenous organic matter supplied to the sampling locality during the onset of the t oae and across a lithological transition unlike other ancient intervals of anoxia and extinction biomarker indices of planktonic community structure do not display major changes or anomalous values depositional environment and redox indicators support a shift towards more reducing conditions in the sediment porewaters and the development of a seasonally stratified water column during the t oae in addition to carotenoid biomarkers for green sulfur bacteria gsb we report the first occurrence of okenane a marker of purple sulfur bacteria psb in marine samples younger than 1 64 ga based on modern observations a planktonic source of okenane s precursor okenone would require extremely shallow photic zone euxinia pze and a highly restricted depositional environment however due to coastal vertical mixing the lack of planktonic okenone production in modern marine sulfidic environments and building evidence of okenone production in mat dwelling chromatiaceae we propose a sedimentary source of okenone as an alternative lastly we report the first parallel compound specific c13 record in marine and terrestrial derived biomarkers across the t oae the c13 records of short chain n alkanes acyclic isoprenoids and long chain n alkanes all encode negative carbon isotope excursions cies and together they support an injection of isotopically light carbon that impacted both the atmospheric and marine carbon reservoirs to date molecular c13 records of the t oae display a negative cie that is smaller in magnitude compared to the bulk organic c13 excursion although multiple mechanisms could explain this observation our molecular petrographic and rock eval data suggest that variable mixing of terrigenous and marine organic matter is an important factor affecting the bulk organic c13 records of the t oae

laminated sediments as palaeo indicators as society at large becomes increasingly concerned with the issues surrounding global climate change so the pressure on the scientific community to produce models and predictions of climate variability increases in many respects however that branch of science concerned with climate change is in its infancy while recent meteorological and oceanographic studies have shed light on the processes and mechanisms of atmospheric and oceanic circulation this has produced only a snapshot perspective of global change limited by the range of instrumental or historical records on the other hand palaeoclimatic and palaeoceanographic studies have been mainly on coarser millennial timescales that have a more academic and less immediate appeal the palaeorecords which have the required temporal interannual decadal resolution are limited to tree rings ice cores coral records and laminated marine or lacustrine sediments this volume is concerned with the wide ranging application of lacustrine and marine laminated sediments as palaeo indicators

nearshore euxinia in the photic zone of an ancient sea abstract evidence for photic zone euxinia pze in ancient oceans is widespread and commonly associated with global climate change and biotic events however evidence of pze in marginal settings is commonly extrapolated to infer basin scale characteristics to explore the relationship between euxinia in marginal settings and the wider basin in one palaeozoic context we have conducted a detailed spatial and temporal examination the palaeowater column redox state from the polish sector of the southern permian basin spb during deposition of the zechstein lopingian second carbonate main dolomite cycle sediments from toe of slope slope and hypersaline lagoonal settings of the northeastern margin of the spb contain abundant chlorobactane isorenieratane and their likely degradation products c 15 to c 31 2 3 6 aryl isoprenoids these indicate that part of the photic zone was euxinic during significant intervals of the main dolomite deposition further evidence for strongly anoxic conditions includes the occurrence of c 28 bisnorhopane high concentrations of pentakishomohopanes i e high homohopane indices and the occurrence of framboidal and native sulphur crystals in slope facies however a lack of these signatures in basinal settings indicates that strongly reducing conditions were restricted to the slope and toe of slope locations even in these settings however highly variable homohopane indices and concentrations of isorenieratene and chlorobactene derivatives as well as the presence of benthic fauna and bioturbation indicate that anoxia fluctuated throughout deposition of the main dolomite likely on a variety of timescales sterane distributions are also variable suggesting a dynamic ecosystem likely exhibiting a strong response to environmental forcing overall it appears that high but episodic primary bioproductivity of organic matter was concentrated on the northeastern slope and restricted lagoons leading to the formation of source rocks for petroleum however the temporal and geographical restriction of anoxia appears to have prevented the accumulation of large or more widespread quantities of organic matter and in fact toc contents exhibit poor correlation with ecological and anoxia indicators this model indicates that strong evidence for pze in shelf and slope facies need not be associated with widespread basin scale anoxia with implications for organic matter burial carbon cycling and biotic crises

effects of an oceanic anoxic event on the stable carbon isotopic composition of early toarcian carbon the early toarcian transgression is marked by the occurrence of organic carbon rich shales in large parts of western europe and in other parts of the world as well based on the positive carbon isotope excursion of pelagic limestones in the middle to upper part of the falciferum zone in several of the tethyan sections the widespread occurrence of the early toarcian shales was explained by an oceanic anoxic event oae jenkyns 1988 jenkyns and clayton 1997 the rapid burial of large amounts of organic carbon which is rich in 12 c would have led to a relative enrichment in 13 c of the global carbon reservoir and hence to an increase in delta 13 c of the limestones in southwest germany and a number of other locations both organic and inorganic carbon display a negative isotope excursion in the upper part of the tenuicostatum zone and the lower part of the falciferum zone synchronous to black shale deposition and predating the positive isotopic excursion kuspert 1982 1983 it is presently unclear what the exact cause for this widespread negative isotopic excursion is jenkyns and clayton 1997 the objective of our study was to examine if the negative carbon isotope excursion of organic matter om in the southwest german toarcian shales can be attributed to compositional changes of the om or if the excursion is related to variations in delta 13 c sub co2 aq in the photic zone to this end we analyzed the molecular and stable carbon isotope composition of om in ten samples spanning the early toarcian toc 2 5 10 5 percent hi 350 700 biomarker distributions and kerogen pyrolysates differ only slightly among the samples and delta 13 c values of primary production markers follow closely those of associated carbonate and kerogen delta 13 c sub carb toc this strongly suggests that differences in delta 13 c toc are related to differences in delta 13 c of co 2 aq in the photic zone supporting kuspert9s model of advection of isotopically light organic matter derived co 2 from anoxic bottom waters evidence for euxinic conditions extending into the photic zone was found by the presence of derivatives of carotenoids such as isorenieratane from anoxygenic phototrophic sulfur bacteria their concentrations are extremely low in black shales from the tenuicostatum zone but are significant in the falciferum and bifrons zone with a maximum in the exaratum subzone suggesting that photic zone euxinia pze was a common feature of the early toarcian sea in southwest germany our data therefore support the kuspert model of advection of isotopically light organic matter derived co 2 from anoxic bottom waters to the upper part of the photic zone resulting in a negative isotope spike the enrichment in 13 c in the middle of the falciferum zone which followed the negative spike may be attributed to the burial of isotopically light organic matter through worldwide black shale deposition