extreme change in sulfide concentrations in the black sea during the little ice age reconstructed using molybdenum isotopes the black sea is the largest and most studied anoxic basin in the modern world much of this research has focused on the redox structure of the water column specifically on the driving forces behind variations in the position stability and structure of the oxic anoxic interface chemocline however none of these studies has been able to quantify the historical sulfide concentrations associated with the changes in chemocline depth using the isotopic composition of molybdenum in sediments as a proxy we show for the first time that varying concentrations of dissolved sulfide can be fingerprinted in historical systems our molybdenum isotope data indicate that in the region of the bosporus inlet the chemocline rose more than 65 m reaching concentrations over 100 m sulfide in the bottom water ca 300 yr b p this historical shoaling of the chemocline and extreme change in bottom water sulfide concentration exceeds the modern changes that have been observed directly and attributed to anthropogenic influences on the black sea chemistry hydrology the first cold interval of the little ice age when temperature and circulation changes occurred in the black sea basins may have provided the natural trigger for this extreme rise in bottom water sulfide concentrations

orbital forcing of organic carbon burial in the proto north atlantic during oceanic anoxic event 2 the cenomanian turonian c t intervals at dsdp sites 105 and 603b from the northern part of the proto north atlantic show high amplitude short term cyclic variations in total organic carbon toc content the more pronounced changes in toc are also reflected by changes in lithology from green claystones toc 1 although their depositional history was different the individual toc cycles at sites 105 and 603b can be correlated using stable carbon isotope stratigraphy sedimentation rates obtained from the isotope stratigraphy and spectral analyses indicate that these cycles were predominately precession controlled the coinciding variations in hi oi 13corg and the abundance of marine relative to terrestrial biomarkers as well as the low abundance of lignin pyrolysis products generated from the kerogen of the black claystones indicate that these cyclic variations reflect changes in the contribution of marine organic matter om the cooccurrence of lamination enrichment of redox sensitive trace metals and presence of molecular fossils of pigments from green sulfur bacteria indicate that the northern proto north atlantic ocean water column was periodically euxinic from the bottom to at least the base of the photic zone 150 m during the deposition of the black claystones in contrast the green claystones are bioturbated are enriched in mn do not show enrichments in redox sensitive trace metals and show biomarker distributions indicative of long oxygen exposure times indicating more oxic water conditions at the same time there is evidence e g abundance of biogenic silica and significant 13c enrichment for oc of phytoplanktic origin for enhanced primary productivity during the deposition of the black claystones we propose that increased primary productivity periodically overwhelmed the oxic om remineralisation potential of the bottom waters resulting in the deposition of om rich black claystones because the amount of oxygen used for om remineralisation exceeded the amount supplied by diffusion and deep water circulation the northern proto north atlantic became euxinic during these periods both sites 105 and 603b show trends of continually increasing toc contents and hi values of the black claystones up section which most likely resulted from both enhanced preservation due to increased anoxia and increased production of marine om during oceanic anoxic event 2 oae2

diagenetic and catagenetic products of isorenieratene molecular indicators for photic zone anoxia a wide range of novel diagenetic and catagenetic products of the diaromatic carotenoid isorenieratene a pigment of the photosynthetic green sulphur bacteria chlorobiaceae has been identified in a number of sedimentary rocks ranging from ordovician to miocene compound identification is based on nmr mass spectrometry the presence of atropisomers and stable carbon isotopes atropisomers contain an axially chiral centre which in combination with other chiral centres results in two or more diastereomers that can be separated on a normal gc column chlorobiaceae use the reverse tca cycle to fix carbon so that their biomass is enriched in 13c high 13c contents of isorenieratene derivatives therefore support their inferred origins isorenieratene derivatives include c 40 c 33 and c 32 diaryl isoprenoids and short chain aryl isoprenoids with additional aromatic and or s containing rings c 33 and c 32 compounds are diagenetic products of c 33 and c 32 carotenoids formed from isorenieratene during early diagenesis through expulsion of toluene and m xylene respectively cyclisation of the polyene acyclic isoprenoid chain can proceed via an intramolecular diels alder reaction followed by aromatisation of the newly formed ring sulphurisation is also an important process during early diagenesis competing with expulsion and cyclisation sulphur bound isorenieratane is released during progressive diagenesis due to cleavage of relatively weak ss and cs bonds cleavage of c c bonds during aromatisation of newly formed rings and during catagenesis yields short chain compounds the inherent presence of a conjugated double bond system in carotenoids implies that similar diagenetic and catagenetic reactions can occur with all carotenoids chlorobiaceae live at or below the oxic anoxic boundary layer and require both light and h 2s the presence of isorenieratene or its diagenetic and catagenetic products in ancient sedimentary rocks and crude oils is therefore an excellent indication for photic zone anoxia in the depositional environment diagenetic and catagenetic products of isorenieratene are expected to find applications in reconstruction of palaeoenvironments and in oil oil and oil source rock correlation studies their presence in several petroleum source rocks suggests that anoxia is an important environmental parameter for the preservation of organic matter

nearshore euxinia in the photic zone of an ancient sea part ii the bigger picture and implications for understanding ocean anoxia abstract biomarker palaeontological and isotopic evidence suggests that the late permian carbonate seas i e the northern npb and southern spb permian basins of northern pangea were characterized by significant spatial and temporal variations in the palaeowater column redox state this is particularly the case with regard to the deposition of the lopingian zechstein cycle 2 carbonate rocks a shelf to basin reconstruction of environmental conditions was achieved by analysing nearly 400 core samples from 49 wells this allowed an evaluation of the spatial variations in facies and broad oceanographic conditions at the basin scale specifically in the lower slope and shallow basin facies of the northern margin of the spb present day northern poland and eastern germany highly variable concentrations of the green sulphur bacterial biomarkers chlorobactane and isorenieratane and their likely degradation products c 15 to c 31 2 3 6 aryl isoprenoids indicative of photic zone euxinia and homohopane indices indicative of anoxia combined with the presence of a benthic fauna and bioturbation indicate a variable but occasionally anoxic euxinic water column locally in lagoonal facies in the northern and southern margin of the spb euxinic conditions also developed but these were likely associated with localised conditions or benthic production in association with microbialites the presence of gammacerane in the eastern spb south eastern germany and eastern poland suggests elevated salinities there compatible with the restricted configuration of the basin however a lack of these signatures in basinal settings of the eastern spb indicates that strongly reducing conditions were restricted to the lower slope and shallow basin locations and restricted lagoons and were not developed in the basin centre moreover this anoxia euxinia in marginal settings is restricted to the north eastern part of the spb the south eastern part of the spb se poland in contrast is devoid of evidence for pze the southern margin of the spb is also characterized by generally oxic suboxic conditions with local anoxia limited to more restricted embayments and elevated salinities limited to restricted oxic anoxic lagoons in the western spb ne england and adjacent offshore and the npb outer moray firth offshore scotland the water columns were oxic suboxic overall it appears that high but episodic primary bioproductivity of organic matter was concentrated on or even limited to the lower slopes of the spb s north eastern margin and the restricted lagoons and shallow basin of its southern margin leading to the formation of source rocks for petroleum in these areas in addition the temporal and geographical restriction of anoxia appears to have prevented the accumulation of large and more widespread quantities of organic matter in fact toc contents exhibit a poor correlation with ecological and anoxia indicators crucially this work confirms that the strong evidence for pze observed in shelf and lower slope shallow basin facies of the north eastern spb need not be associated with widespread basin scale anoxia this conclusion has implications for organic matter burial carbon cycling and biotic crises during other times in earth history

alternative biological sources for 1 2 3 4 tetramethylbenzene in flash pyrolysates of kerogen pyrolysates of kerogens isolated from indian ocean surface sediments and from black sea unit ii contain abundant 1 2 3 4 tetramethylbenzene 1 2 3 4 tmb suggesting the presence of macromolecularly bound isorenieratane skeletons derived from isorenieratene biosynthesized by green sulphur bacteria cf hartgers et al 1994c however the 13c content of 1 2 3 4 tmb is identical to that of algal lipids excluding an origin from green sulphur bacteria the presence of 1 2 3 4 tmb in pyrolysates of stable residues of several marine algae indicates that it can also have an algal origin therefore the assessment of photic zone anoxia on the basis of the abundant presence of 1 2 3 4 tmb in the pyrolysate is not possible without determination of its stable carbon isotopic composition and comparison with those of algal lipids

organic sulfur compounds formed during early diagenesis in black sea sediments abstract sediments from units i and ii of the black sea were analyzed to assess the early diagenetic formation of organic sulfur compounds osc a series of isomeric c28 2 4 dialkylthiophenes was found at low concentrations in surface sediments osc with c25 highly branched isoprenoid rbi skeletons were not found in surface sediments even though there was a rapid decrease in the concentrations of c25 hbi alkenes in the same sediments nor were osc found which contained carbon skeletons derived from c37 c39 alkenes which are also abundant in the sediment as depth increased in unit i concentrations of the c28 2 4 dialkylthiophenes decreased while c25 and c30 hbi thiolanes appeared at the bottom of unit i and increased in concentration into unit ii treatment of macromolecular material from sediment extracts with raney nickel yielded phytane as the dominant hydrocarbon as well as series of c25 and c30 hbi hydrocarbons carotane and isorenieratane these latter two components were generally absent from the free hydrocarbon fractions these results indicate that sulfur incorporation into functionalized lipids can occur during the very early stages of sedimentary diagenesis even at the sediment water interface on the other hand the rapid loss of c25 hbi alkenes in surface sediments could not be accounted for by sulfur quenching and other potential osc precursors such as c37 c39 alkenes also apparently did not incorporate sulfur into readily analyzable material

organic petrology and geochemistry of eocene suzak bituminous marl north central afghanistan depositional environment and source rock potential abstract organic geochemistry and petrology of eocene suzak bituminous marl outcrop samples from madr village in north central afghanistan were characterized via an integrated analytical approach to evaluate depositional environment and source rock potential multiple proxies suggest the organic rich toc 6 wt bituminous marls are immature for oil generation e g vitrinite ro 1 indicating organic input from marine algae and or bacterial biomass and sterane hopane ratios are low 0 12 0 14 monoaromatic steroids are dominated by c28 clearly indicating a marine setting high gammacerane index values 0 9 are consistent with anoxia stratification and may indicate intermittent saline hypersaline conditions stable c isotope ratios also suggest a marine depositional scenario for the suzak samples consistent with the presence of marine foraminifera including abundant planktic globigerinida and rare benthic discocyclina and nummulites biomarker 2 methylhopane for photosynthetic cyanobacteria implies shallow photic zone deposition of madr marls and 3 methylhopane indicates presence of methanotrophic archaea in the microbial consortium the data presented herein are consistent with deposition of suzak bituminous marls in shallow stratified waters of a restricted marine basin associated with the southeastern incipient or proto paratethys geochemical proxies from suzak rock extracts s content high polar content c isotopes normal r c27 29 steranes and c29 c30 and c26 c25 hopane ratios are similar to extant data from paleogene oils produced to the north in the afghan tajik basin this observation may indicate laterally equivalent strata are effective source rocks as suggested by previous workers however further work is needed to strengthen oil source correlations

the stratigraphy depositional environment and dating of a possible tidal surge deposit in the beauly firth area northeast scotland the stratigraphic setting pollen and diatom content and radiocarbon age of a thin minerogenic layer predominantly composed of grey micaceous silty sand are described from two sites located near the head of the beauly firth scotland the layer resulted from a short lived incursion of marine water which flooded subtidal intertidal saltmarsh and reedswamp environments during the mid holocene comparisons with other sites in eastern scotland indicate this incursion may have been caused by a north sea storm surge event of considerable magnitude

reconstruction of changes in export productivity during pliocene sapropel deposition a biomarker approach abstract biomarkers alkenones loliolide isololiolide dinosterol and c30 1 15 diol keto ol representative of four major classes of marine primary producers haptophytes diatoms dinoflagellates eustigmatophytes respectively from three sites of an east west transect spanning the entire eastern mediterranean basin were studied for changes in phytoplankton export production before during and after deposition of a pliocene total organic carbon rich up to 27 sapropel 2 943 ma biomarker contents showed substantial differences between non sapropelic and sapropelic sediments in non sapropelic sediments small contents are observed reflecting extensive oxic degradation in oxic pore waters during deposition in the sapropels biomarker accumulation rates showed a substantial increase from the base to the centre likely resulting from increased biological productivity since the bottom waters were continuously anoxic and preservation conditions are similar the diatom biomarker loliolide isololiolide became distinctly more abundant in the sapropels indicating that the eastern mediterranean basin was enriched in nutrients this caused enhanced export production by the major phytoplankton classes leading to periods of sapropel deposition alkenone based sea surface temperature reconstructions indicated that this change in phytoplankton composition was not influenced by changes in sea surface temperature but was mainly nutrient controlled compound specific 13c measurements did not provide additional evidence for substantially increased primary production rates the 13c values of c37 2 alkenones and loliolide isololiolide showed a slightly negative shift instead of the anticipated positive shift this was probably caused by the enrichment of dissolved inorganic carbon in the upper water column caused by enhanced recycling of respired co2 due to the shallow chemocline

enhanced productivity led to increased organic carbon burial in the euxinic north atlantic basin during the late cenomanian oceanic anoxic event 1 three cenomanian turonian c t 93 5 ma black shale sections along a northeast southwest transect in the southern part of the proto north atlantic ocean were correlated by stable carbon isotope stratigraphy using the characteristic excursion in 13c values of both bulk organic matter om and molecular fossils of algal chlorophyll and steroids all three sites show an increase in marine organic carbon oc accumulation rates during the c t oceanic anoxic event oae the occurrence of molecular fossils of anoxygenic photosynthetic green sulfur bacteria lack of bioturbation and high abundance of redox sensitive trace metals indicate sulfidic conditions periodically reaching up into the photic zone before as well as during the c t oae during the c t oae there was a significant rise of the chemocline as indicated by the increase in concentrations of molecular fossils of green sulfur bacteria and mo al ratios the presence of molecular fossils of the green strain of green sulfur bacteria indicates that euxinic conditions periodically even occurred at very shallow water depths of 15 m or less during the c t oae however bottom water conditions did not dramatically change as indicated by more or less constant v al and zn al ratios at site 367 this suggests that the increase in oc burial rates resulted from enhanced primary productivity rather than increased anoxia which is supported by stable carbon isotopic evidence and a large increase in ba al ratios during the c t oae the occurrence of the productivity event during a period of globally enhanced organic carbon burial rates i e the c t oae points to a common cause possibly related to the formation of a deep water connection between north and south atlantic basins

euphotic zone bacterioplankton sources major sedimentary bacteriohopanepolyols in the holocene black sea abstract bacteriohopanepolyols bhps are lipid constituents of many bacterial groups geohopanoids the diagenetic products are therefore ubiquitous in organic matter of the geosphere to examine the potential of bhps as environmental markers in marine sediments we investigated a holocene sediment core from the black sea the concentrations of bhps mirror the environmental shift from a well mixed lake to a stratified marine environment by a strong and gradual increase from low values 30 g g 1 toc in the oldest sediments to 170 g g 1 toc in sediments representing the onset of a permanently anoxic water body at about 7500 years before present bp this increase in bhp concentrations was most likely caused by a strong increase in bacterioplanktonic paleoproductivity brought about by several ingressions of mediterranean sea waters at the end of the lacustrine stage 9500 years bp 15n values coevally decreasing with increasing bhp concentrations may indicate a shift from a phosphorus to a nitrogen limited setting supporting growth of n2 fixing bhp producing bacteria in sediments of the last 3000 years bhp concentrations have remained relatively stable at about 50 g g 1 toc the distributions of major bhps did not change significantly during the shift from lacustrine or oligohaline to marine conditions tetrafunctionalized bhps prevailed throughout the entire sediment core with the common bacteriohopanetetrol and 35 aminobacteriohopanetriol and the rare 35 aminobacteriohopenetriol so far only known from a purple non sulfur proteobacterium being the main components other bhps specific to cyanobacteria and pelagic methanotrophic bacteria were also found but only in much smaller amounts our results demonstrate that bhps from microorganisms living in deeper biogeochemical zones of marine water columns are underrepresented or even absent in the sediment compared to the bhps of bacteria present in the euphotic zone obviously the assemblage of molecular fossils in the sediments does not represent an integrated image of the entire community living in the water column remnants of organisms living in zones where effective transport mechanisms such as the fecal pellet express exist are accumulated while those of others are underrepresented our work shows a high stability of bhps over geological time scales largely uniform distributions and only minor changes in structures like an increasing prevalence of saturated over unsaturated bhps with time were observed consequently sedimentary bhp distributions are less suitable as markers for in situ living bacteria but are useful for paleoreconstructions of bacterioplanktonic communities and productivity changes

evidence of early flandrian tidal surges in lower strathearn scotland detailed stratigraphic palaeobotanical diatom and pollen and radiometric evidence from a sequence of buried estuarine deposits buried peat and overlying estuarine carse deposits at wester rhynd in lower strathearn suggests the occurrence of two brief marine incursions between the abandonment by the sea of a buried estuarine flat probably the low buried beach at about 8765 75 bp and c 8500 bp the first incursion shortly after 8565 85 bp caused bottom living marine diatoms to be thrown without clastic material onto the rapidly accumulating terrestrial peat the second bracketed by dates of 8485 80 and 8510 85 bp deposited an extremely thin 1 mm layer of fine sand that interrupts an otherwise unbroken buried peat succession covering the period 8765 75 to 7710 70 bp the marine diatom lithostratigraphic and 14c evidence together are consistent with a storm storm surge or tsunami origin for these events which are recognised principally from the diatom evidence having left no mark in the pollen record

a high resolution historical record of holocene anoxygenic primary production in the black sea i reconstruct the historical record of anoxygenic primary production in the black sea over the last 8200 years by an analysis of chlorobium carotenoids in sediments anoxygenic photosynthesis in the black sea occurs only when hydrogen sulfide containing deep water penetrates the euphotic zone the data show that the black sea has experienced large fluctuations in the extent of anoxygenic primary production and therefore the depth of the h2s chemocline throughout much of the holocene changes in the depth of the h2s chemocline also shift the dominant phytoplankton populations in the water column to noncarbonate bearing species and result in the formation of intense dark bands in sediments

holocene relative sea level changes on the margin of a glacio isostatically uplifted area an example from northern caithness scotland evidence is presented for holocene relative sea level changes on the margin of a glacio isostatically uplifted area the lower wick river valley northern caithness scotland lithostratigraphic b

black sea chemocline oscillations during the holocene molecular and isotopic studies of marginal sediments we measured d 13 c values of free and sulfur bound lipids and framboidal pyrite size distributions in three sediment cores from the southern margins of the black sea the margin cores show a marked diaerence in the occurrence of biomarkers from green sulfur bacteria compared with the deep basin cores as a result of deepening of the chemocline resulting from enhanced mixing and or decreased light penetration as a consequence of high turbidity and productivity in shelf waters quantitation of biomarkers suggests that photic zone anoxia along the shelf margin was generally absent during the deposition of unit i although occurred during the deposition of unit iib at two sites 2000 elsevier science ltd all rights reserved

molecular indicators for palaeoenvironmental change in a messinian evaporitic sequence vena del gesso italy i variations in extractable organic matter of ten cyclically deposited marl beds abstract a screening by direct desulphurization of extracts was employed for 21 immature organic sulphur rich marl samples from 10 of the 14 evaporite cycles in an italian messinian evaporitic basin vena del gesso gessoso solfifera fm the combined information retrieved from free and sulphur bound carbon skeletons enabled a detailed palaeoenvironmental reconstruction the biomarker compositions of the marls point to large variations in the composition of species in the water column e g dinoflagellates diatoms and other algae cyanobacteria methanogens green sulphur bacteria and bacterivorous ciliates and in contributions from the continent i e land plants within each marl bed and between marl beds the marl beds were deposited within a stratified lagoon where anoxic conditions extended into the photic zone for much of the time

patterns of isostatic land uplift during the holocene evidence from mainland scotland preliminary results of a lengthy and detailed investigation into middle and late holocene raised shorelines in mainland scotland indicate that three shorelines are sufficiently widely distributed to permit an examination of their extent and of the patterns of uplift which they indicate the shorelines are the storegga tsunami shoreline reached at c 7100 14c years bp at the culmination of the main postglacial transgression and the blairdrummond shoreline reached after the main postglacial shoreline at c 2000 4200 14c years bp at the time of a tsunami believed to have been caused by the second storegga submarine slide the main postglacial shoreline reached at c 5800 6850 14c years bp the main postglacial shoreline previously believed to be the highest holocene raised shoreline in scotland is now believed to be overlapped around the periphery of the uplifted area by the later blairdrummond shoreline isobase models based upon quadratic trend surface analysis of available comparable height dat

geochemical study of macromolecular organic matter from sulfur rich sediments of evaporitic origin messinian of sicily by chemical degradations abstract selective chemical degradations have been performed on sulfur rich macromolecular organic matter from sediments of the messinian of sicily upper miocene italy the biomarkers released upon different desulfurization experiments are much more abundant than the free lipids and display completely different distributions which reflect the selective trapping of poly functionalized molecules by inorganic sulfur species at an early stage of diagenesis the bound biomarker distributions reveal a dominant phytoplanktonic input originating from an upper oxic water layer and a moderate bacterial reworking of the organic matter a contribution from cyanobacteria to the organic matter cannot be excluded the presence of carotenoids typical from photosynthetic sulfur bacteria attests to a stratified water body where an anoxic photic zone occurred lialh4 hydrogenolysis of sulfur rich macromolecules revealed that polysulfide bridges contribute to a large extent in the cross linking the results of deuterium labelling experiments are discussed in terms of sulfur incorporation on functionalized lipids

organic matter production and preservation and evolution of anoxia in the holocene black sea dating of sediments collected in gravity cores during leg 1 of the 1988 r v knorr expedition to the black sea suggests that the onset of water column anoxia at 7 5 ka was virtually synchronous across the basin over a depth range of 200 2250 m a finely laminated organic carbon oc rich sapropel unit ii was produced as a result of this anoxia the trigger for increased oc production and development of anoxia was the spillover of saline waters through the bosporus that probably began at 9 0 ka and peaked between 7 0 and 5 5 ka this spillover enhanced vertical mixing and nutrient cycling and caused a short term 2 3 kyr burst in surface water productivity during the early part of unit ii deposition continued incursion of saline waters enhanced vertical stability and inhibited mixing of nutrients into surface waters thus limiting primary production and decreasing the oc flux to sediments beginning 5 5 ka concentration accumulation rate and degree of preservation of organic matter all decreased in the upper part of unit ii as a result of decreasing productivity but anoxia persisted throughout most of the water column the end of unit ii sapropel deposition was synchronous across the black sea as the result of the first blooms of the coccolith emiliania huxleyi which presumably marked an increase in surface water salinity above 11 and the beginning of unit i deposition the high coccolith carbonate fluxes that occurred during deposition of unit i diluted the oc concentration in the sediments but oc accumulation rates are about the same as those in upper part of unit ii

late devensian and holocene relative sealevel changes at loch nan eala near arisaig northwest scotland pollen diatom radiocarbon and lithostratigraphical data from isolation basins in northwest scotland are used to quantify the reference water tide level indicative range and age of differenty types of isolation and connection contacts tendencies of sea level movement and relative sea level changes from the mid lateglacial interstadial 11 8 ka bp to the late holocene are constructed from these data relative sea level fell continuously from 17 8 m od at 11 8 ka bp to ca 5 2 m od at 10 1 ka bp from an unkown minimum between 10 ka and 9 ka bp relative sea level then rose to 6 3 m od at 8 3 ka bp the maximum holocene sea level occurred within the range 6 6 m od to 9 3 m od between 6 6 ka bp and 4 0 ka bp before falling to present isobase age altitude and quantitative rebound models for northwest scotland are tested using these sealevel data but none of the published models shows close agreement with the new results

development of photic zone euxinia in the eastern mediterranean basin during deposition of pliocene sapropels abstract carotenoids were analysed in ca 1 cm thick subsamples of three laterally time equivalent sapropels from a west east transect of the eastern mediterranean basin to study euxinic periods during pliocene sapropel formation the amount of intact isorenieratene summed all trans and cis isomers ranged from non detectable at the base and top of a sapropel up to 140 g g sediment in the central parts isorenieratene accumulation rates at the central and western site are remarkably similar and increase sharply to levels of up to 3 0 mg m 2 yr 1 in the central part of the sapropel and then drop to low levels this pattern indicates an expansion of euxinic conditions reaching into the photic zone followed by deepening of the chemocline during deposition of this pliocene sapropel the sapropel from the easternmost site of the basin which contains less organic carbon shows much lower isorenieratene accumulation rates and even absence of isorenieratene in the central part of the sapropel ba al ratios indicate enhanced palaeoproductivity during sapropel formation supporting previously proposed models according to which increased productivity is the driving force for the generation of euxinic conditions

characterization of depositional conditions for lacustrine oil shales in the eocene jijuntun formation fushun basin ne china abstract the strike slip fushun basin hosts a lacustrine oil shale interval of ca 50 300 m in the eocene lutetian jijuntun formation the oil shale deposits consist of the lower lean oil shale unit losu and the upper rich oil shale unit rosu in outcrop areas the identified depositional cycles of ca 8 10 m and 5 8 m in thickness record the stacking of massive and non laminated oil shales in the losu and fine and coarse laminated oil shales in the rosu respectively depositional conditions in the paleo jijuntun lakes were synoptically reconstructed based on sedimentary features trace element and organic geochemical proxies oxic to suboxic fresh water conditions were prevailing in the paleo jijuntun lakes during deposition of the losu and then evolved into oxygen deficient fresh to mildly brackish water conditions during deposition of the rosu as revealed by the concentrations of redox and salinity sensitive trace elements e g v ni v cr ni co and sr ba ratios and boron content in the oil shales warm to cool and humid to arid climate represented by e g sr cu and rb sr ratios could result in the deepening of water column from ca 20 30 m to ca 100 m and saline stratification superposed on pre existing thermal stratification in the paleo jijuntun lakes a systematical decrease approximately one order of magnitude in the concentrations of most trace elements except for boron and co in the coaly oil shale in the lowermost losu relative to those in the other oil shales in the jijuntun formation indicates the significant change of organic matter om input from higher plant especially coaly materials to aquatic plankton this is partly consistent with the variations of om input from terrestrial higher plant and aquatic organisms type ii kerogen in the losu to lacustrine algae type i kerogen in the rosu as revealed by biomarkers the slight to significant enrichment or depletion of few trace elements i e mn and mo in these immature to low mature oil shale deposits may be associated with low to moderate productivities of aquatic plankton and or incompletely oxygen free conditions in the paleo jijuntun lakes

carotenoid diagenesis in recent marine sediments i the peru continental shelf 15 s 75 w abstract we report here the distribution of carotenoids in peru marine surface sediments including partial identification of 37 pigments 33 of which have not been previously reported to occur in marine sediments our analysis demonstrates that zooplanktonic crustacea diatoms dinoflagellates cryptomonads purple nonsulfur photosynthetic bacteria and unidentified species of photosynthetic bacteria are contributors to sedimentary organic matter fucoxanthin fucoxanthinol diadinoxanthin peridinin and peridininol the principal carotenoids of diatoms and dinoflagellates observed in sediment traps are nearly absent from our sample even though these phytoplankton are the primary source of organic matter we attribute this to the presence of 5 6 epoxides in these pigments a feature which causes rapid cleavage of the polyene and fragmentation to low molecular weight compounds

petrogenesis of cretaceous adakitic and shoshonitic igneous rocks in the luzong area anhui province eastern china implications for geodynamics and cu au mineralization both adakitic and shoshonitic igneous rocks in the luzong area anhui province eastern china are associated with cretaceous cu au mineralization the shaxi quartz diorite porphyrites exhibit adakite like geochemical features such as light rare earth element lree enrichment heavy ree hree depletion high al2o3 mgo sr sr y and la yb values and low y and yb contents they have low end t values 3 46 to 6 28 and high 87sr 86sr i ratios 0 7051 0 7057 sensitive high resolution ion microprobe shrimp zircon analyses indicate a crystallization age of 136 3 ma for the adakitic rocks most volcanic rocks and the majority of monzonites and syenites in the luzong area are k rich or shoshonitic and were also produced during the cretaceous 140 125 ma they are enriched in lree and large ion lithophile elements and depleted in ti and nb and ba and exhibit relatively lower end t values ranging from 4 65 to 7 03 and relatively higher 87sr 86sr i ratios varying between 0 7057 and 0 7062 the shoshonitic and adakitic rocks in the luzong area have similar pb isotopic compositions 206pb 204pb 17 90 18 83 207pb 204pb 15 45 15 62 and 208pb 204pb 38 07 38 80 geological data from the luzong area suggest that the cretaceous igneous rocks are distributed along ne fault zones e g tanlu and yangtze river fault zones in eastern china and were likely formed in an extensional setting within the yangtze block the shaxi adakitic rocks were probably derived by the partial melting of delaminated lower crust at pressures equivalent to crustal thickness of 50 km i e 1 5 gpa possibly leaving rutile bearing eclogitic residue the shoshonitic magmas in contrast originated mainly from an enriched mantle metasomatized by subducted oceanic sediments they underwent early high pressure 1 5 gpa fractional crystallization at the boundary between thickened 50 km lower crust and lithospheric mantle and late low pressure 1 5 gpa fractional crystallization in the shallow 50 km crust the adakitic and shoshonitic rocks appear to be linked to an intra continental extensional setting where partial melting of enriched mantle and delaminated lower crust was probably controlled by lithospheric thinning and upwelling of hot asthenosphere along ne fault zones e g tanlu and yangtze river fault zones in eastern china both the shoshonitic and adakitic magmas were fertile with respect to cu au mineralization

product distributions from chemical degradation of kerogens from a marl from a miocene evaporitic sequence vena del gesso n italy abstract lithium in ethylamine li etnh 2 treatment has been carried out on sulphur rich kerogens from 10 sub samples of the cycle iv marl from the vena del gesso evaporitic sediments upper miocene italy the treatment releases after chromatography of the resulting solvent extracts up to 30 of the kerogen total organic carbon the biomarkers released are dominated by components of algal origin the concentrations of the aliphatic hydrocarbons obtained are of the same order of magnitude as the bound alkanes released upon desulphurization of polar fractions from organic extracts and show similar distributions the presence of diaromatic isoprenoids derived from chlorobiaceae indicates that photic zone anoxia occurred during the deposition of the cycle iv marl such conditions being more prevalent at the middle of the section polar material makes up by far most of the organic material released and contains in particular alcohols and amides which may result from the cleavage of ester bonds present in these immature kerogens the amides being secondary products formed by reaction with the etnh2 in the case of the alcohols however these components could also arise from cleavage of sulphide bound moieties

patterns of holocene relative sea level change in the north of britain and ireland temporal and spatial patterns of relative sea level rsl change in the north of britain and ireland during the holocene are examined four episodes each defined by marked changes in the rsl trend are identified each episode is marked by a rise to a culminating shoreline followed by a fall episode hrsl 1 dates from the younger dryas to early in the holocene hrsl 2 to hrsl 4 occurred later in the holocene there is extensive evidence for each episode and on this basis the spatial distribution of the altitude data for three culminating shorelines and a shoreline formed at the time of the holocene storegga slide tsunami ca 8110 100 cal bp is analysed ordinary kriging is used to determine the general pattern following which gaussian trend surface analysis is employed recognising that empirical measurements of rsl change can be unevenly distributed spatially a new approach is introduced which enables the developing pattern to be identified the patterns for the most widely occurring shorelines were analysed and found to be similar and common centre and axis models were developed for all shorelines the analyses described provide models of the spatial pattern of holocene rsl change in the area between ca 8100 cal bp and ca 1000 cal bp based on 2262 high resolution shoreline altitude measurements these models fit the data closely no shoreline altitude measurement lying more than 1 70 m or 1 82 m from the predicted value the models disclose a similar pattern to a recently published glacial isostatic adjustment model for present rsl change across the area indicating that the overall spatial pattern of rsl change may not have varied greatly during the last ca 8000 years

holocene spit development on a regressive shoreline dornoch firth scotland the series of raised and modern spits and beaches which characterise the dornoch firth coastline are described the beaches and spits in the inner firth are relatively small having developed during the mid holocene with little subsequent modification in the central firth large spit complexes developed on the northern and southern shorelines extending westwards during the mid holocene however during the later holocene spit growth was towards the east on the southern shore and towards the southwest on the northern shore in the outer firth spit and beach development mainly occurred during the later holocene the development of spits at the mouth of the firth changed the wave energy environment in the central section and resulted in the marked changes in spit alignment in this area the features also indicate that during the rise and culmination of the main postglacial transgression coarse clastic sediments derived from cliff erosion dominated in contrast during the later holocene when relative sea level fell sand sized material derived from the nearshore and offshore zone predominated

holocene relative sea levels and related prehistoric activity in the forth lowland scotland united kingdom abstract changes in relative sea level rsl and their effect on the distribution of human activity in the forth lowland scotland uk between ca 11 700 and ca 2000 calibrated years before present bp are examined block uplift of shorelines occurred over a longer period than previously thought continuing to at least around 4700 bp new graphs of rsl change based upon an analysis of previous work and evidence from new sites using standard morphological and stratigraphical analyses support a fall in rsl in the early holocene during which buried estuarine surfaces were formed followed by a marked reversal on a centennial perhaps even decadal scale sometime around 9900 9500 bp from a falling sequence to a rising one there may have been a short lived fluctuation in the rising rsl ca 8300 bp and the holocene storegga slide tsunami of ca 8100 bp was widespread in the lowland the rising rsl culminated at the main postglacial shoreline reached ca 7800 bp when mean high water spring tides mhws lay within the range 14 6 16 5 m british ordnance datum od in the western lowland this is the highest published holocene rsl in britain and ireland the subsequent fall in rsl stabilised at a second shoreline the blairdrummond shoreline from which regression was occurring at ca 4700 bp rsl later fell to a lower shoreline at ca 3900 bp before reaching present levels within the last three millennia comparison between the empirical evidence for rsl change in this area and glacial isostatic adjustment models indicates both similarities and differences records of archaeological sites and artefacts in the lowland and surrounding areas are discussed maps showing the evolution of the estuary are compared with the distribution of mesolithic neolithic bronze age and iron age activity evidence for mesolithic people indicates the opportunistic use of available resources as rsl rose and the estuary expanded to its maximum extent neolithic people were also attracted to the estuary building at least one platform from which to exploit resources and accumulating middens along the shoreline for over 2000 years bronze age people were present across the emerging saltmarshes and mudflats before raised peat mosses already extensive at the head of the lowland developed more widely in the iron age the area could be accessed both between the peat mosses of the western lowland and across newly emergent land in the east as rsl continued to fall

evidence for a tsunami from a mesolithic site in inverness scotland temporary excavations at castle street inverness described by wordsworth 1985 proceedings of the society of antiquaries of scotland 115 89 103 disclosed a mesolithic horizon covered by a layer of marine sand the sand layer is similar in appearance and age to a sand layer frequently found in coastal sediments in eastern scotland and recently attributed to a tsunami generated by submarine sliding on the continental slope off storegga south west norway which took place c 8000 5000 radiocarbon years bp there is some evidence that the tsunami may have affected other mesolithic sites and it may ultimately prove a useful chrono stratigraphic marker

sediment accumulation in the central western black sea over the past 5100 years the postdepositional particle flux accumulation rate over the last 5100 years was studied in the anoxic sediment units i and ii from the central western black sea deposition of unit ii sapropel in the deep black sea basin was divided further into two subunits the beginning of the deposition of the sapropel in the black sea 5100 3100 years b p subunit iib was characterized by higher organic carbon accumulation rates due largely to higher primary production accumulation rates of lithogenic matter were at a minimum compared to younger units during the subsequent 2100 years 3100 1000 years b p subunit iia organic carbon accumulation rates decreased considerably while accumulation rates of lithogenic matter increased to the present level at 1000 years b p unit i total mass accumulation rates increased by a factor of 3 this increase was largely a result of an increase in carbonate accumulation rates by a factor of 11 which was caused by the rapid appearance of emiliania huxleyi in the black sea higher carbonate accumulation rates in unit i are mainly the cause for the considerably lower organic carbon content compared to unit ii since the organic carbon accumulation rate in unit i did not decrease general correspondence of accumulation rates of lithogenic matter in different cores through time suggests overregional long term 100 year scale climatic effects on the terrigenous particle supply to the black sea

reconstructing the palaeoecosystem and palaeodepositional environment within the upper devonian lower mississippian bakken formation a biomarker approach abstract biomarkers have been used extensively to correlate oil families oil source rock relationships and source inputs and to help identify the palaeodepositional environment for a given geological sedimentary unit despite their application in characterising the bakken formation shales a number of biomarkers still appear unable to provide us a consistent understanding regarding heterogeneity in source organic matter and palaeoenvironment here we infer the palaeodepositional environment within the bakken formation shales using a biomarker suite and biomarker depth profiles we also use the occurrence and abundance of biomarkers to define organic facies and to make inferences regarding biotic interactions drawn from modern analogues the variations and co occurrence of biomarkers is explained by the existence of a proposed complex algal bacterium bacteriovore palaeoecosystem this approach not only helps explain the depth variation in occurrence and concentration of biomarkers and the molecular composition of associated organic matter but also advances the use of biomarker analysis and biomarker associations to determine a complex environment sensitive palaeoecosystem

iunconsistencies in accumulation rates of black sea sediments inferred from records of laminae and 210pb recently published estimates for the age of the unit 1 unit 2 contact in black sea sediments based on accelerator mass spectrometry ams 14c measurements jones 1990 calvert et al 1991 appear to be older than those based on the previously published chronology based on lamina couplets degens et al 1980 hay 1988 by a factor of 2 to 3 to help reconcile the differences we compare sediment accumulation rates based on the 210pb method with estimates based on lamina counts for two cores from the black sea abyssal plain accumulation rates estimated using the 210pb technique have varied little over the last 150 years from the averages of 55 and 50 g m 2 yr 1 at stations in the western and eastern basins respectively these values are about a factor of 2 lower than accumulation rates derived by counting lamina couplets over the dated intervals close examination of the laminae suggests that the discrepancy exists both because it is difficult to count the very fine laminae and because a complete couplet is not deposited every year in order to provide a useful stratigraphic horizon for future investigators studying sedimentary records of the black sea we estimate the age of a distinct black marker horizon which can be easily identified across the entire abyssal plain to be 150 8 years deposited in 1838 8 a d

identification of carotenals in sediments abstract high performance liquid chromatography with photodiode array uv vis detection and atmospheric pressure chemical ionization mass spectrometry was used to analyze sediment samples from the meromictic ace lake antarctica as well as a pliocene sapropel from the mediterranean sea and a miocene marl from the vena del gesso formation italy the ace lake samples contained intact chlorobactene isorenieratene and carotene and two series of carotenoid breakdown products the first and more abundant series was identified as aryl carotenals of increasing chain length c13 c15 c18 c20 c22 c25 c27 c30 and c32 on the basis of their uv vis and mass spectra they appear to be formed from chlorobactene through oxidative cleavage of the double bonds of the polyene chain the minor series carotenals was also identified and may be formed from carotene in a similar manner intact isorenieratene and the carotenal series were also found in the mediterranean sea sapropel only a trace of the c32 carotenal could be detected suggesting isorenieratene as the predominant source of these carotenals additionally intact carotene and c13 c30 carotenals were found in the sapropel the absence of the c32 carotenal strongly suggests these breakdown products are derived from carotene the vena del gesso marl contained both intact isorenieratene and the c13 c25 carotenals the absence of the longer chain length carotenals from this sample may indicate more advanced oxidation of isorenieratene the carotenals are likely formed during storage of samples and or extracts under non ideal conditions i e not frozen and exposed to oxygen although they may also be formed by diagenetic processes they can be relatively abundant and sometimes be an order of magnitude higher in concentration than the parent carotenoid hence not including the carotenals could lead to an underestimation of the persistence of photic zone euxinia

endeavour 26 north a porphyry copper gold deposit in the late ordovician shoshonitic goonumbla volcanic complex new south wales australia endeavour 26 north is the largest of 12 pipelike porphyry cu au deposits found near parkes in central west new south wales within the late ordovician goonumbla volcanic complex the dominant volcanic rocks of the complex the goonumbla volcanics are latitic flows and volcanic breccias which are overlain by the trachytic wombin volcanics the volcanic rocks are characterized by high k 2 o and high k 2 o na 2 o ratios which are typical of the shoshonite association as well as an enrichment in large ion lithophile elements and a low concentration of high field strength elements the nelungaloo volcanics form an early ordovician nonshoshonitic volcanic substrate to the complex which initially developed in a submarine and subsequently subaerial setting the 87 sr 66 sr epsilon nd and pb isotope data indicate the magmas were derived from mantle sources the shoshonitic magmas may be products of high pressure fractionation in the subcontinental lithosphere the porphyry deposits are associated with a gravity low which is taken to reflect a subvolcanic chamber beneath the center of the complex all deposits are located within a pronounced circular feature in the aeromagnetic data that is interpreted as the margin of a collapsed caldera dioritic to monzonitic stocks which in part define the caldera rim represent a resurgent phase of magmatism the endeavour 31 stock which was part of this phase is ringed by six porphyry cu au deposits including endeavour 26 north the deposits are centered on fingerlike quartz monzonite porphyries which cut the endeavour 31 stock at depth geochemical anomalies of cu and zn in the bedrock define the size of the alteration system associated with the stock in part the distribution of the cu au deposits is controlled by the endeavour lineament in comparison to most other volcanic and intrusive rocks of the goonumbla volcanic complex the endeavour

late devensian and holocene relative sea level changes on the isle of skye scotland uk detailed litho and biostratigraphical analyses from three coastal sites in contrasting coastal settings on the isle of skye scotland uk reveal evidence for several changes in relative sea level during the late devensian and holocene at the start of the record relative sea level in the area was high at ca 12 500 14c ca 14 800 cal yr bp but then fell reaching a low point during the younger dryas at ca 11 000 10 000 14c ca 13 000 11 600 cal yr bp when a rock platform correlated with the main rock platform was formed in the early middle holocene relative sea level was rising by ca 8000 14c ca 8800 cal yr bp and in northeast skye a lagoonal surface correlated with the main postglacial shoreline was formed at ca 6600 14c ca 7500 cal yr bp by the late holocene relative sea level was again falling but a rise registered at at least two sites began probably before ca 4000 14c ca 4500 cal yr bp and a second lagoonal surface in northeast skye correlated with the blairdrummond shoreline was formed although by ca 3000 14c ca 3200 cal yr bp relative sea level in the area had resumed its downward trend the pattern of relative sea level changes disclosed is compared with evidence elsewhere in scotland

colonization succession and extinction of marine floras during a glacial cycle a case study from the windmill islands east antarctica using biomarkers with the exception of the diatoms little is known of the extinction colonization and succession of marine floras during glacial cycles here we study both morphological and biochemical fossils in two sediment cores from the antarctic to unravel the sequence of events over a single glacial cycle the cores from the nearshore continental shelf off the windmill islands 66 s 110 e east antarctica span the period from marine isotope stage 3 or earlier to the present new high performance liquid chromatography and mass spectrometry methods were used to study fossil pigments with additional data from siliceous microfossils lithological analyses and radiocarbon dates results show two response processes first there is the large scale impact of the expanding ice sheet in removing the flora from the inner shelf primarily through the denial of light destabilization of the substratum and elimination of habitats second there are a number of glacial climate interactions that have a surprisingly strong influence on recolonization and succession these include sea ice extent and the proximity of the ice edge the annual duration of open water the stabilization of the substratum first by benthic diatoms and later by macrophyte algae and relative sea level a period of warmer climate in the mid holocene had a considerable influence on the composition and species diversity of the marine flora these are the first data on the timing of colonization and succession of marine floras over a glacial cycle based on both morphological and biochemical fossils

a high resolution biomarker study of different lithofacies of organic sulfur rich carbonate rocks of a kimmeridgian lagoon french southern jura the upper jurassic calcaires en plaquettes formation southern jura france which was deposited in a lagoonal setting reveals three lithofacies limestones with fine scale parallel laminations limestones with undulated stromatolite type laminations and massive limestones it was examined at the millimetre scale if the lithological differences are accompanied by differences in the composition of organic matter om and if microbial mats played a role in the preservation of om as suggested previously four types of laminae light parallel dark parallel light undulated dark undulated and a massive limestone sample were analysed the om in all facies is characterised by a high hydrogen index 870 970 and a variable 13c content 23 5 or to 28 1 the molecular composition of om appeared similar in all samples e g i extractable biomarkers are dominated by n alkane and hopanoid carbon skeletons predominantly in a sulfur bound form ii isorenieratene derivatives indicating anoxic conditions in the photic zone are present in relatively large amounts iii kerogen pyrolysates are dominated by organic sulfur compounds notwithstanding the overall similarity in om composition some significant differences were observed e g i low molecular weight sulfur bound hopanoids and steroids are relatively more abundant in toc lean light coloured samples than in toc rich dark coloured samples this is probably related to differences in the degree of intermolecular sulfur cross linking of the om ii the concentrations and distributions of several biomarkers in the light coloured undulated sample differ from those in the other samples these differences are attributed to the periodic occurrence of microbial mats our data indicate that om in the calcaires en plaquettes formation is predominantly composed of sulfur bound lipids formed at times that bottom waters were euxinic a periodic deepening of the oxic anoxic interface and of the light penetration depth to below the sediment surface allowed microbial mats to develop organic remains of the mats however are swamped by sulfur bound planktonic lipids

the holocene storegga slide tsunami in the united kingdom all currently known sites in the united kingdom with evidence for the holocene storegga slide tsunami are described information on the altitude distribution stratigraphical context age particle size profile and microfossil characteristics of the deposits is presented the tsunami involved a greater area than previously described reaching a coastline over 600 km long the ubiquitous sand layer which forms the main deposit associated with the event is shown to exhibit a consistent morphology and a particle size profile marked by fining upwards sequences an analysis of new and previously published radiocarbon dates indicates that from evidence in the united kingdom the event took place sometime around 7100 radiocarbon years bp 7900 calibrated years bp a new isobase model for mainland scotland and adjacent areas providing a preliminary estimate of land uplift since the tsunami is presented the model estimates contemporary sea surface level offshore at 14 m below the present day mean high water spring tides tsunami sediment run up is greatest in inlets where it reaches at least 25 m on shetland and at least 5 m along the mainland coastline to the south and run up of the tsunami would have exceeded these values the tsunami sediments identified here are considered particularly valuable as a synchronous marker horizon

the sedimentology of middle holocene tsunami facies in northern sutherland scotland uk abstract lagoonal sediments attributed to the main holocene marine transgression in strath halladale northern sutherland contain a complex coarser layer believed to have been deposited during the tsunami associated with the second storegga slide off south west norway the coarser sequence is dated at between 7590 50 and 7290 50 radiocarbon years bp 6507 6260 cal bc and 6228 6029 cal bc detailed stratigraphical analysis has determined a distinctive suite of sedimentary sub units within the coarser layer in marked contrast to the sediments which occur above and below a pronounced erosional unconformity with the underlying sediments is recorded with the base of the tsunami layer characterised by eroded material from the underlying peat the presence of a mixed diatom assemblage although fragmentary indicates a chaotic accumulation of the deposit with all habitats represented variations in particle size within the sequence disclose striking similarities with those from contemporary tsunami deposits the run up of the tsunami sediments is calculated at a minimum of 4 6 m this is the first occasion on which a deposit of the second storegga slide tsunami has been found outside the north sea basin and indicates that the area affected by the tsunami may have been larger than has been previously described

biomarker evidence for intermittent photic zone euxinia in the aptian albian organic sedimentary record from the ionian zone epirus greece new biomarker evidence is presented that constrains the conditions of deposition and preservation of sediments rich in extractable organic matter from the aptian albian sedimentary record of the ionian zone in nw greece analyses were specifically carried out on total lipid extracts from 12 organic rich samples from the vigla shale member two of which represent the regional record for the early albian paquier event of oae1b in the aliphatic fractions compound groups such as n alkanes isoprenoid alkanes steroids hopanoids and terpenoids were recognized pointing to a mixed origin from algae and prokaryotes with an additional measurable contribution from terrigenous plant matter these compounds suggest deposition of the primary organic sediments under conditions of decreased bottom water oxygen concentrations mass spectral evidence from the aromatic fractions of most samples reveal the variable presence of diagenetic and catagenetic derivatives of carotenoid pigments including some with bound sulfur that are characteristic of photoautotrophic sulfur bacteria the presence of specific biomarkers originating from photosynthetic anaerobic microorganisms similar to those in ancient and contemporary euxinic basins such as the black sea suggest that photic zone euxinic conditions were intermittently operative in the aptian albian stages of the ionian basin but were not exclusively characteristic of the black shale representing the paquier event itself

distributions of pigments in the organic matter of marls from the vena del gesso evaporitic sequence abstract the porphyrins and carotenoids of marl horizons within the messinian evaporitic cycles of the vena del gesso basin show variations in abundance and composition throughout a sequence of ten cycles significant variations are also apparent within individual marl horizons the differences in pigment distribution reflect significant changes in the environmental conditions during sediment deposition the presence of significant amounts of isorenieratene and co occurrence of an alkyl porphyrin with a c 34 skeleton provide evidence for anoxic conditions extending into the photic zone of the palaeo water column variations in the free pigment contents of the marls reflect a regressive trend both during deposition of an individual marl and over the entire sequence

geochemistry of the black sea during the last 15 kyr a protracted evolution of its hydrography and ecology the black sea is a 2200 m deep anoxic marine sea connected to the mediterranean sea via the dardanelles strait marmara sea and the 3 km wide 35 m deep bosphorus strait the biogeochemistry of sediment from the anatolia slope has recorded changes to the hydrography leading up to and following the input of mediterranean water at 9 4 ka 103 yr bp when global sea level rose to the level of the bosphorus sill and high salinity water from the mediterranean began to spill into the then brackish lake the water initially mixed little with the lake water but cascaded to the bottom where it remained essentially isolated for ca 1 6 kyr the time required to fill the basin from the bottom up at its present input rate the accumulation of mo in the sea floor sediments a proxy of bottom water anoxia increased sharply 8 6 ka when bacterial respiration in the bottom water advanced to so42 reduction by the oxidation of organic detritus that settled out of the photic zone its accumulation remained elevated to 5 6 ka when it decreased 60 only to again increase slightly at 2 0 ka the accumulation of corg a proxy of primary productivity increased 3 to 4 fold at 7 8 ka when upward mixing of the high salinity bottom water replaced the then thin veneer of the brackish photic zone in less than 50 yrs from that time onward the accumulation of corg mo and additional trace metals have reflected the hydrography of the basin and bosphorus strait controlled largely by climate

postglacial tectonics of the scottish glacio isostatic uplift centre new evidence combined with a detailed re evaluation of postglacial fault movements seismic activity and shoreline sequences suggests that the period of deglaciation and the early holocene was more seismically active than the mid to late holocene it is proposed that the large scale lateral displacements formerly proposed can not be justified rather all postglacial fault movements appear to be limited to metre scale vertical movements along pre existing fault lines in addition it is argued that the younger dryas ice advance may have produced localised crustal redepression but not the more widespread impact formerly proposed both tectonic and postglacial rebound stresses however may be needed to explain the contemporary seismotectonics of the scottish highlands

trace metal records of regional paleoenvironmental variability in pennsylvanian upper carboniferous black shales abstract regional geochemical differences within a laterally continuous cyclic pennsylvanian upper carboniferous shale in midcontinent north america are interpreted in light of models of glacioeustatic forcing and new views on water column paleoredox stability and trace metal behavior in black shale environments specifically we characterize differences in transition metal fe mn mo v ni zn pb and u concentrations in black shales of the hushpuckney shale member of the swope limestone in iowa and equivalent black shale beds of the coffeyville formation in oklahoma although c s fe systematics and uniform 34 s depleted isotope ratios of pyrite indicate pervasive euxinic deposition anoxic and sulfidic bottom waters for these shales regional variations can be inferred for the efficiency of mo scavenging and for the rates of siliciclastic sedimentation as expressed in spatially varying fe al ratios black shales in iowa show mo enrichment roughly five times greater than that observed in coeval euxinic shales in oklahoma by contrast fe al ratios in oklahoma shales are as much as five times greater than the continental ratio of 0 5 observed in the over and underlying oxic facies and in the coeval black shales in iowa recent work in modern marine settings has shown that enrichments in fe commonly result from scavenging in a euxinic water column during syngenetic pyrite formation in contrast to fe the concentrations of other transition metals mo v ni pb zn u are typically more enriched in the black shales in iowa relative to oklahoma the transition metal trends in these paleozoic shales are reasonably interpreted in terms of early fixation in organic rich sediments due to euxinic water column conditions however regional variations in 1 rates of siliciclastic input 2 organic reservoirs including relative inputs of terrestrial versus marine organic matter and 3 additional inputs of metals to bottom waters from contemporaneous hydrothermal vents are additional key controls that lead to geographic variation in the extent of metal enrichments preserved in ancient organic rich sediments

a molecular and carbon isotope biogeochemical study of biomarkers and kerogen pyrolysates of the kimmeridge clay facies palaeoenvironmental implications abstract structures and carbon isotopic compositions of biomarkers and kerogen pyrolysis products of a dolomite a bituminous shale and an oil shale of the kimmeridge clay formation kcf in dorset were studied in order to gain insight into i the type and extent of water column anoxia and ii changes in the concentration and isotopic composition of dissolved inorganic carbon dic in the palaeowater column the samples studied fit into the curve of increasing 13 c of the kerogen 13 c toc with increasing toc reported by huc et al 1992 their hypothesis that the positive correlation between toc and 13 c toc is the result of differing degrees of organic matter om mineralisation in the water column was tested by measuring the 13 c values of primary production markers these 13 c values were found to differ on average by only 1 among the samples implying that differences in the extent of om mineralisation cannot fully account for the 3 difference in 13 c toc the extractable om in the oil shale differs from that in the other sediments due to both differences in maturity and differences in the planktonic community these differences however are not likely to have significantly influenced 13 c toc either all three sediments contain abundant derivatives of isorenieratene indicating that periodically euxinia was extending into the photic zone the sediments are rich in organic sulfur as revealed by the abundant sulfur compounds in the pyrolysates the prominence of c 1 c 3 alkylated thiophenes over n alkanes and n alkenes is most pronounced in the pyrolysate of the sediment richest in toc this suggests that sulfurisation of om may have played an important role in determining the toc 13 c toc relationship reported by huc et al 1992

molecular isotopic and dinoflagellate evidence for late holocene freshening of the black sea abstract the black sea is the world s largest anoxic basin with oxygen free conditions below water depths of approximately 100 m resulting from strong density stratification the salinity of its surface water likely varied substantially over time due to variations in freshwater input from large rivers and in the saline bottom water of mediterranean origin coming across the shallow sill of the bosporus however long term reconstructions of surface water salinities are lacking the invasion of the coccolithophorid emiliania huxleyi in the black sea at approximately 2720 a responsible for a marked change in sediment composition lithology has been commonly attributed to salinity levels rising above 11 we analyzed the d values of long chain alkenones produced by haptophyte algae mainly e huxleyi in a core from the eastern basin of the black sea to reconstruct past variations in sea surface salinities and combined this with relative salinity changes generated from organic walled dinoflagellate cyst dinocyst distributions from the same core combined results indicate a substantial freshening of black sea surface waters in the last 3000 years suggesting that sea surface salinity was substantially higher than the present day salinity of approximately 18 at the time e huxleyi invaded the black sea

towards improved empirical isobase models of holocene land uplift for mainland scotland uk a new approach to modelling patterns of glacio isostatic land uplift during the holocene in mainland scotland uk is described the approach is based upon altitude measurements at the inner margin or locally highest point of raised estuarine surfaces dated by radiocarbon assay supported by microfossil analyses 2241 altitudes have been analysed by a technique new to studies of former sea levels gaussian trend surface analysis and isobase models for four holocene shorelines the holocene storegga slide tsunami shoreline abandoned rapidly circa 7900 sidereal years bp the main postglacial shoreline abandoned during circa 6400 7700 sidereal years bp the blairdrummond shoreline abandoned during circa 4500 5800 sidereal years bp and a speculative fourth shoreline the wigtown shoreline abandoned during circa 1520 3700 sidereal years bp are shown in a series of maps the implications of the shoreline patterns for glaicio isostasy in the area are discussed it is maintained that the statistical technique used enables broad estimates to be made of nearshore sea surface change

cenomanian turonian organic sedimentation in north west africa a comparison between the tarfaya morocco and senegal basins abstract the cenomanian turonian oceanic anoxic event was recognised in north western africa in various depositional settings from abyssal areas to continental shelves to derive information on environmental conditions in these different settings and define a depositional model a petrographical and geochemical study of the organic matter was performed on sediments from the tarfaya morocco and senegal basins the results obtained for these two locations were compared to those of previous studies namely from dsdp wells petrographic and geochemical data allow the differentiation of two main organofacies a shallow depositional facies continental shelf is characterised by low total organic carbon toc contents the second organofacies deposited in the deep marine environment slope and abyssal shows a high toc content 7 the predominance of fluorescing amorphous om combined with high hi values suggests good preservation conditions the s c ratio 0 36 and abundance of organic sulphur compounds support this interpretation and indicate a development of anoxic conditions to explain the organic contrast between both environments a depositional model has been developed which is based on limited water exchange between both depositional settings the main factor which has determined black shale sedimentation is the restricted water circulation related to the presence of isolated depositional environment during atlantic ocean opening compared to present upwelling zones the palaeoproductivity in the studied area was relatively moderate during cenomanian turonian and seems not to be the only determining factor of organic matter accumulation

the quaternary deposits and landforms of scotland and the neighbouring shelves a review abstract a thick sequence of quaternary sediments up to 1000 m has been deposited in the north sea basin and perhaps five major glacial episodes the first occurring prior to ca 1 8 2 1 ma bp and the last during the late devensian can be recognised between the glacial events periods of low salinity arctic marine or glacio marine sedimentation have been dominant although episodes of ameliorated climate when north atlantic drift waters had access to the north sea have been identified a number of horizons in separate boreholes have been correlated with the last interglacial oxygen isotope stage 5e and a sequence of water mass movements around the scottish coasts can be reconstructed for the last ca 125 ka on land sequences of quaternary deposits relating to several glacial and non glacial terrestrial and marine events occur in different areas but due to poor dating correlation between these sequences cannot yet be achieved in particular north east scotland has a complex glacial history with evidence for ice sheet glaciation on at least four occasions evidence from the outer hebrides north east scotland and the north sea basin indicates that the late devensian scottish ice sheet had a rather restricted extent only reaching a short distance offshore along much of the east and west coasts at this time ice free areas existed in north east scotland on the isle of lewis and probably in caithness and orkney whilst part of the outer shelf around st kilda was dry land a marine embayment extended down the east coast of scotland between the scottish and scandinavian ice sheets and independent ice caps existed on the outer hebrides and probably on shetland deglaciation of the greater part of the country took place prior to ca 13 ka bp whilst the climate was still very cold the ice retreat appears to have been orderly with stagnant ice masses being trapped only in topographically suitable locations a number of retreat stages or minor readvances occurred during the general deglaciation the firth of clyde was one of the last areas outside the highlands to be deglaciated and this occurred in a rapid possibly catastrophic fashion shortly prior to ca 13 ka bp despite the mild climate at the start of the lateglacial interstadial it is not known if there was complete deglaciation prior to the loch lomond readvance the readvance glaciers however may have started to advance during the latter part of the interstadial when declining terrestrial temperatures coincided with a period of mild marine conditions the loch lomond readvance maximum can only be dated to some time after ca 10 9 ka bp and it is likely that final ice free conditions were not achieved until the earliest holocene

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

flandrian relative sea level changes in the ythan valley northeast scotland relict flandrian estuarine deposits in the ythan valley are confined to an area in the lower valley around the present estuary they rest upon a discontinuous layer of peat over an irregular surface of sand and gravel and consist for the most part of a grey silty clay or carse deposit which forms terraces or small areas of carseland at the seaward end of the estuary the grey silty clay contains a layer of grey micaceous silty fine sand which tapers into the basal peat whilst in places the surface of the grey silty clay is covered by peat and or blown sand the vegetational context and age of these deposits have been determined at waterside near the mouth of the present estuary here the grey silty clay accumulated as the result of a marine transgression which began in the early flandrian and culminated between about 6189 95 and some time prior to 4000 80 radiocarbon years b p the carseland surface produced by this phase of accumulation is the highest flandrian estuarine surface in the valley at about 4 5 m o d and is correlated with the main postglacial shoreline elsewhere in eastern scotland withdrawal of the sea from this level may have been interrupted by the formation of a lower carseland surface before present levels were reached though this is far from certain the grey micaceous silty fine sand layer is dated at approximately 6850 140 radiocarbon years b p and is correlated with similar layers that may have been deposited following a storm surge the paper concludes with some considerations on the age and distribution of the main postglacial shoreline in eastern scotland

new aromatic biomarkers in sulfur rich coal abstract a molecular study of linear branched and isoprenyl alkylbenzene skeletons and alkenylbenzenes in the soluble fraction extracted from a sulfur rich utrillas coal was carried out using gas chromatography mass spectrometry gc ms the presence of c24 c28 diaromatic compounds not previously reported in coals suggests that photosynthetic green sulfur bacteria may have made an input of organic matter to these coals the unsaturated linear alkenylbenzenes and isoprenyl c15 and c20 alkylbenzene skeletons are also described for the first time in the soluble fraction of geological samples

contrasting sulfur geochemistry and fe al and mo al ratios across the last oxic to anoxic transition in the cariaco basin venezuela an abrupt transition from oxic to anoxic sulfidic euxinic marine bottom waters occurred in the cariaco basin in response to increasing productivity resulting from the late pleistocene post glacial rise in sea level and corresponding increase in surface water nutrient availability the microlaminated sediments of the euxinic interval which span the last f14 5 ky suggest a predominance of water column syngenetic pyrite formation based on 1 high pyrite sulfur spy concentrations in the surficial sediment layers 2 values for degree of pyritization dop that generally do not increase appreciably with increasing burial 3 ratios of total iron fet to al that are elevated above the continental baseline recorded in the underlying oxic sediments and 4 spy isotope trends that largely mimic the d 34 shsof the modern water column intermediate dop values in the microlaminated deposits and fet al ratios that are slightly above continental levels indicate an iron reservoir controlled by scavenging during syngenetic pyrite formation in combination with intermediate rates of fe bearing siliciclastic accumulation as predicted from the relative rates of siliciclastic delivery fet al and dop data lie between end member values observed in the modern black sea as viewed broadly fet al and dop relationships in euxinic sediments reflect the balance between syngenetic fe scavenging and temporal and spatial gradients in siliciclastic input pyrite concentrations are generally low in the underlying oxic marine deposits because of limitations in the supply of organic carbon corg however the upper 80 cm of the fe rich corg poor bioturbated sediment show evidence for a strong diffusional hsoverprint from the overlying fe limited euxinic marine environment this post glacial transition manifests in pyrite overprints that are strongly 34 s depleted relative to those in restricted presently euxinic marine settings elsewhere in the world such as the black sea where the sedimentary sequence spanning the last glacial interglacial transition begins with a shift from freshwater to corg poor oxic marine deposition and thus dominantly sulfate diffusion trends for mo al ratios in the microlaminated sediments suggest that mo is enriched by roughly two orders of magnitude above the continental levels recorded in the oxic deposits organic matter plays a role by enhancing hsproduction and or by providing a substrate for mo scavenging significant mo enrichment via diffusion into the upper portion of the bioturbated zone was not observed despite hs rich pore waters as recorded in the heavy iron sulfide overprint we have

on the postglacial isostatic adjustment of the british isles and the shallow viscoelastic structure of the earth summary observations of postglacial relative sea level rsl history at sites beyond the margins of the main accumulations of wu rm wisconsin devensian ice may be invoked to test the accuracy of global models of the glacial isostatic adjustment process the existing database of rsl time series for the british isles forms a continuous network of sites that sample the coasts of scotland england and wales fairly uniformly and which may be especially important in this regard not only are these 14c data for the holocene epoch of very high quality in terms of our knowledge of the coastal environment and relationship to palaeo sea level of each age measurement but they are especially numerous and relate to an island that was itself partly glaciated in the north essentially ice free in the south and located well outboard of the massive ice sheet that covered fennoscandia at the last glacial maximum lgm taken together the time series from 55 distinct locations allow us to perform a fairly stringent test of the recently formulated ice 4g vm2 global model of the isostatic adjustment process even without modification this model has been shown to fit most of the time series in the uk data set rather well in order to satisfy very recently published a priori constraints on the maximum thickness of the scottish ice sheet however we find that the lithospheric thickness the feature of the radial viscoelastic structure to which the rebound data from scotland are most sensitive must be somewhat reduced whereas the assumed thickness of the lithosphere in ice 4g vm2 was near to 120 km best fits to the scottish data require a lithospheric thickness near to 90 km this reduced value for lithospheric thickness agrees exceedingly well with the latest estimates of this earth property based on the inversion of oceanic geoid and topography data as the asymptotic thickness characteristic of the oldest ocean floor this would appear to be the best possible a priori estimate for the thickness of the cratonic lithospheres upon which the largest ice sheets of the late pleistocene are known to have rested we also demonstrate explicitly that inferences of the shallow viscoelastic structure beneath the british isles are strongly influenced by the details of the history of deglaciation at remote locations at antarctica in particular

the storegga slides evidence from eastern scotland for a possible tsunami abstract the second storegga slide on the continental slope off western norway has been dated at between 8000 and 5000 yrs b p a prominent sand layer in flandrian holocene deposits along the coast of eastern scotland and dated at approximately 7000 yrs b p may have been deposited by a tsunami generated by the slide the altitude and stratigraphy of the layer allow estimates to be made of the magnitude of the earthquake which initiated the slide

organic matter and trace element rich sapropels and black shales a geochemical comparison a distinct pliocene eastern mediterranean sapropel i 282 recovered from three ocean drilling program odp leg 160 sites has been investigated for its organic and inorganic composition this sapropel is characterized by high organic carbon corg and trace element contents and the presence of isorenieratene derivatives the latter suggests that the base of the photic zone was sulphidic during formation of the sapropel combined with evidence of bottom water anoxia preservation of laminae high redox sensitive trace element contents and the abundance and isotopic composition of pyrite this leads to the tentative conclusion that almost the entire water column may have been anoxic this anoxia resulted from high productivity and not from stagnation because an approximation of the trace element budget during sapropel formation shows that water exchange with the western mediterranean is needed entire water column anoxia has been suggested earlier for several black shales with regard to the depositional environment and the corg content however only the cenomanian turonian boundary event ctbe black shales appear to be comparable to this sapropel the proposed trace element removal mechanism of scavenging and co precipitation in an anoxic water column is thought to be similar for both types of deposits the ultimate trace element source for the sapropel however is seawater whereas it is hydrothermal and fluvial input for ctbe black shales because they have a larger temporal and spatial distribution nonetheless the corg rich eastern mediterranean pliocene sapropel discussed here may be considered to be a younger analogue of ctbe black shales

water column structure during deposition of middle devonian lower mississippian black and green gray shales of the illinois and michigan basins a biomarker approach abstract the extractable organic matter of organic rich black shales and associated organic poor bioturbated green gray shales of the illinois and michigan basins of north america is analyzed to constrain the water column structure during their deposition all black shale samples contain derivatives of the biomarker isorenieratene a diaromatic carotenoid pigment produced exclusively by the brown strain of the green sulfur bacteria chlorobiaceae chlorobiaceae are phototrophic organisms requiring euxinic anoxic and sulfidic conditions to survive and the presence of isorenieratene derivatives indicates that the middle devonian early mississippian epeiric seas of north america experienced bottom water euxinic conditions during black shale deposition analysis of green gray shales also reveals the presence of isorenieratene derivatives and in some cases isorenieratane the highly bioturbated fabric of these sediments indicates the presence of oxygen in bottom waters during their deposition thus we suggest that short term shoaling of the oxycline across the basin slope may have occurred during their deposition though they were deposited predominantly under an oxygenated water column i e above the chemocline most green gray shales contain three pseudohomologous series of branched alkanes with quaternary substituted carbon atoms baqcs which are absent in black shale samples recent studies suggest that baqcs are produced by benthic chemoautotrophs dwelling at the redox boundary separating anoxic sediments from moderately oxygenated waters comparison of the biomarker content i e regular isoprenoid baqcs between black and green gray shales indicates different sources of organic matter and suggests that phytoplanktonic productivity in the upper water column was enhanced during black shale deposition the results of this study indicate that the alternation of green gray and black shales in these basins results from the vertical fluctuations of the chemocline these fluctuations seem to be driven by changes in phytoplanktonic productivity our data when associated to previous studies of other black shales from canada and europe confirm that photic zone euxinia was a widespread feature of low latitude epeiric seas during the middle devonian lower mississippian

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

loch lomond stadial and flandrian shorelines in the inner moray firth area scotland morphological mapping and stratigraphical investigations have identified surface and buried relict marine features in the inner moray firth area the features consist of a buried gravel layer formed during the loch lomond stadial a buried beach of early flandrian age and surface beaches and estuarine flats of mid late flandrian age analysis of the altitudes of morphological features has identified two buried and five possibly six surface glacio isostatically tilted raised shorelines the steepest shoreline is associated with the buried gravel layer and slopes down towards n20 e at a gradient of 0 20m km younger shorelines have lower gradients between 0 16 0 03m km the shoreline sequence combined with published data defines relative sea level movements in the area during the last 11000 years the inner moray firth shorelines are correlated with similar features in other areas of scotland which include the main lateglacial main buried and main postglacial shorelines

late devensian and holocene relative sea level changes in northwestern scotland new data to test existing models abstract pollen diatom lithostratigraphic and radiocarbon data from five sites in northwestern scotland provide new data from an area previously devoid of reliable and precise information on late devensian and holocene sea level changes the sites cover a range of palaeoenvironments indicative of diversity in coastal evolution since deglaciation for each site and palaeoenvironment the reference water tide level indicative range age and tendency of sea level movement of all sea level index points are quantified to enable correlation of the diverse coastal environments the data record patterns of relative sea level change and tendencies of sea level movement from 12 ka bp to 1 ka bp this is the longest and most comprehensive published record of relative sea level change from the area the information is used to test the accuracy of existing models of relative sea level change the results are only broadly consistent with a quantitative rebound model and there is significant disagreement with empirical models during the late devensian and the early holocene

organic carbon as a palaeoenvironmental indicator in the marine realm recent developments in biogeochemistry have made accessible all information currently known to be present in sedimentary organic compounds i e the carbon skeleton structure the positions of functional groups and stable carbon isotope ratios this combined information has strengthened the applications of sedimentary organic compounds as biomarkers and palaeoenvironmental indicators this review summarizes the most important biomarkers and their applications in reconstructing marine palaeoenvironments and processes the marine environment is characterized by the combined presence of specific compounds such as organic sulphur compounds dinosteroids 24 n propylsteroids even in trace amounts high amounts of c hbi hydrocarbons and the absence of long chain n alkanes with odd over even predominance bicadinanes and specific higher plant triterpenoids e g oleanane furthermore palaeoenvironmental conditions such as photic zone anoxia hypersalinity microbial sulphate reducing activity algal blooming palaeo upwelling and palaeo surface seawater temperature are indicated by molecular and or isotopic characteristics biomarkers from terrestrial sources are included because land derived organic matter is an important contributor to coastal and shallow marine environments a short case study within a holocene terrestrial marine setting florida bay usa is also presented to illustrate the reconstruction of transgressive regressive trends using selected organic compounds

the altitude and age of the main postglacial shoreline in eastern scotland abstract this paper discusses the patterns of altitude and age variation of the main postglacial shoreline in eastern scotland from the firth of forth to the dornoch firth for reasons of comparability attention is confined to the carseland areas the mean altitude of the shoreline declines eastwards from 14 8 m to 6 1 m od in the forth area from 11 2 m to 8 1 m in the earn tay area and northwards up the coast from the tay area to ca 6 4 m in the montrose basin area ca 3 9 m around the ythan estuary and ca 2 0 m near fraserburgh in the beauly firth inner moray firth area it declines northeastwards from ca 9 m to 7 1 7 9 m and declines to 5 7 m in the dornoch firth the isobase pattern for eastern scotland as represented by a quadratic trend surface conceals a significant regional variation in the tay area the age of the shoreline has been investigated at 14 sites grouped in 8 locations at varying distances from the centre of uplift the ages range from ca 6800 14c years bp in the upper forth carselands to 6095 75 5700 90 bp near fraserburgh with the exception of one site the data are consistent with the hypothesis that the shoreline is measurably diachronous having been abandoned progressively later with increasing distance from the centre of uplift the implications of these findings for understanding isostatic eustatic relationships are discussed

glacial rebound of the british isles ii a high resolution high precision model summary observations of ice movements across the british isles and of sea level changes around the shorelines during late devensian time after about 25 000 yr bp have been used to establish a high spatial and temporal resolution model for the rebound of great britain and associated sea level change the sea level observations include sites within the margins of the former ice sheet as well as observations outside the glaciated regions such that it has been possible to separate unknown earth model parameters from some ice sheet model parameters in the inversion of the glaciohydro isostatic equations the mantle viscosity profile is approximated by a number of radially symmetric layers representing the lithosphere the upper mantle as two layers from the base of the lithosphere to the phase transition boundary at 400 km the transition zone down to 670 km depth and the lower mantle no evidence is found to support a strong layering in viscosity above 670 km other than the high viscosity lithospheric layer models with a low viscosity zone in the upper mantle or models with a marked higher viscosity in the transition zone are less satisfactory than models in which the viscosity is constant from the base of the lithosphere to the 670 km boundary in contrast a marked increase in viscosity is required across this latter boundary the optimum effective parameters for the mantle beneath great britain are a lithospheric thickness of about 65 km a mantle viscosity above 670 km of about 4 5 lo2 pa s and a viscosity below 670 km greater than 4 x lo2 pas

holocene land and sea level changes in great britain analysis of more than 1200 radiocarbon dated samples that constrain relative sea levels in great britain over the past 16 000 yr provides estimates of current land level changes negative of relative sea level change maximum relative land uplift occurs in central and western scotland ca 1 6 mm yr 1 and maximum subsidence is in southwest england ca 1 2 mm yr 1 sediment consolidation arising from autocompaction as the sediment accumulates and from land drainage increases the subsidence in areas with thick sequences of holocene sediments with an average effect equivalent to at least an extra ca 0 2 mm yr 1 land subsidence but more in parts of southeast england 0 5 1 1 mm yr 1 modelled changes in tidal range during the mid to late holocene in eastern england suggest that the calculated rate of land subsidence is overestimated unless such changes are quantified the effect is most significant for large coastal lowlands the fenland and humber ca 0 5 and 0 6 mm yr 1 that were tidal embayments during the mid to late holocene

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

establishment of euxinic conditions in the holocene black sea the paleoenvironmental evolution of the black sea is closely linked to the ingression of mediterranean seawater over the bosporus sill after the last glacial maximum we have reconstructed the temporal and spatial development of the black sea suboxic chemocline which divides oxic surface water from anoxic sulfi dic euxinic deep water by combining high resolution geochemical records of bulk parameters carbonate total organic carbon sulfur trace metals cu mo v and an isotopic proxy 56 fe from seven sediment cores in the black sea we generated a single composite geochemical core log that serves as a reference archive for the entire basin our proxy records refl ect the changing depositional and redox conditions of the black sea and permit us to estimate the infl ow budget of mediterranean seawater throughout the holocene our data indicate a gradual rise of the chemocline until ca 5 3 ka when suboxic waters fl ooded the shelf for the fi rst time trace metal and isotopic inventories document one major descent of the chemocline since the onset of brackish marine conditions before the present stable situation was established

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