early diagenetic transformation of higher plant triterpenoids in deep sea sediments from baffin bay abstract a sediment sequence of early miocene to holocene from ocean drilling program site 645 in central baffin bay was found to contain abundant triterpenoids of higher plant origin including monodesmethyl derivatives and other oxidative degradation products 24 nor triterpenoids of the oleanene ursene and lupane series were found in the nonaromatic hydrocarbon and alcohol fractions of the sediment extracts other diagenetic transformation products included 24 28 dinor olean 17 ene and 24 nor urs 12 en 1 1 one as well as their tentatively identified des a counterparts the identification of these novel degradation products was confirmed by synthesis of a suite of reference compounds the simple reaction sequence applied to obtain 24 nor urs 12 ene from 3 acetoxyurs 12 en 24 oic acid is likely to happen in a similar manner during early diagenesis of organic matter in nature these results have implications for the understanding of the diagenetic reaction sequence leading to the formation of other demethylated triterpenoids of terrigenous origin e g 24 28 dinor lupanes 28 30 dinor 17 hopane is sometimes the dominant hydrocarbon in the most deeply buried samples its co occurrence with higher plant triterpenoids and the low abundance of other regular hopanoids is not considered an indication however that 28 30 dinor 17 hopane is derived from a higher plant precursor molecule it is suggested that two independent sedimentary processes are responsible for the presence of the two types of demethylated triterpenoids observed in baffin bay sediments

early diagenesis of terrigenous triterpenoids and its implications for petroleum geochemistry abstract the distribution of triterpanes in sediments and crude oils is commonly used for oil oil and oil source rock correlation in petroleum geochemistry while isomer ratios of such compounds are applied as maturity parameters the triterpane pattern in terrestrially influenced geological samples is however remarkably less diverse than the triterpenoid skeletons occurring in the extant higher plant biosphere natural observations laboratory experiments and molecular mechanics calculations have revealed that acid catalysed double bond isomerization and skeletal rearrangement reactions of terrigenous triterpenoids during early diagenesis are the key to understanding the triterpane patterns in more matured geological materials examples studied in detail are the double bond isomerization of oleanenes and the subsequent hydrogenation of the products into oleanane and 18 oleanane and the transformation of taraxer 14 ene and lup 20 29 ene into oleanenes although the reactions are likely to be kinetically controlled the main products formed and ultimately preserved are the thermodynamically most stable ones the experimental results and natural observations have significant implications for the use of terrigenous triterpenoid compounds in petroleum geochemistry

paleoenvironmental settings of the sofia lignite basin insights from coal petrography and molecular indicators abstract compositions of balsha lignite sofia coal bearing basin bulgaria and carbonaceous shales are studied by petrological and geochemical proxies the macropetrographic characteristic of profiles is relatively constant the lignite is generally composed of dull matrix coal containing significant amounts of xylite fragments the typical microscopic constituents of the lignite are the ulminite and less frequently textinite lenses scattered within attrinitic groundmass the maceral composition of the organic matter in carbonaceous shales does not differ significantly from that of the lignite samples biomarker assemblages of the extractable portions are determined by gas chromatography mass spectrometry additional information for the compositions of residues after extractions is obtained by tmah thermally assisted hydrolysis methylation petrographic contents lipid assemblage and tmah thermally assisted hydrolysis methylation data imply that the original peat bog is formed in fresh water forest swamp preferably composed by gymnosperms polar diterpenoids argue for cupressaceae s l taxodiaceae as the most probable vegetation for one of the profiles appreciable angiosperm rich herbaceous type flora contribution is assumed polar oleanane triterepenoids and their aromatized derivatives argue for angiosperm input the relevance of a norfriedel 8 en 10 one friedelin ratio for groundwater level appraisal is discussed it admits long period of high water level in the paleomire high content of vanillyl structures and subordinated presence of syringyl units in products of tmah thermally assisted hydrolysis methylation are hint for gymnospermae input in the paleoswamp and angiospermae contribution to one of the profiles cinnamyl phenolic units indicating non woody angiosperm vegetation presence are registered as well flavonoids in products are considered as taxonomic markers of cupressaceae plants in the paleoswamp

bacterial and algal hydrocarbons in sediments from a saline antarctic lake ace lake capillary gas chromatography mass spectrometry c gc ms and iatroscan thin layer chromatography flame ionisation detection tlc fid were used to study hydrocarbon distributions in a sediment core from ace lake a saline meromictic lake in the vestfold hills of antarctica hydrocarbons were abundant in most core sections up to 125 g g dry wt particularly in near surface samples and the distributions were very complex major constituents were identified as phytane 2 6 10 15 19 pentamethyleicosane tetrahydrosqualene a mixture of phytenes cholesta 3 5 diene and fern 7 ene smaller amounts of sterenes and hopenes were also present the predominance of the first 3 acyclic isoprenoids in sediments buried less than 30 cm is consistent with high populations of methanogenic bacteria known to be present phytenes were abundant in all core sections and there was no relationship between their abundance and that of phytane which suggests that they were not derived from methanogenic bacteria phytadienes were minor constituents at all depths studied an unusual feature of some distributions was the high concentrations of fern 7 ene which was the major hydrocarbon in the 20 25 cm core section this alkene was only abundant in sediments which contained high concentrations of methanogen markers suggesting that it may also be indicative of anoxic depositional environments a possible source might be from purple non sulphur bacteria high concentrations of straight chain c29 and c34 alkenes were also found in these sediments but their origin has not been determined major changes in the hydrocarbon distributions with depth indicate that the depositional environment in the lake has altered dramatically since the lake was formed less than 8000 years ago the present condition of permanent anoxic bottom waters probably developed only in the last 1000 years

algal and bacterial hydrocarbons in particulate matter and interfacial sediment of the cariaco trench particulate matter samples 53 m size fractions and sediment from the sediment water interface were collected in the cariaco trench an anoxic marine basin on the continental shelf of venezuela and analyzed for hydrocarbons concentrations of hydrocarbons were highest 10 20 ng 1 in oxic surface waters 0 150 m and at the top of the anoxic zone 350 600 m and were low 3 4 ng l in the low oxygen zone above the oxic anoxic interface 150 250 m and anoxic bottom waters 600 1150 m branched c25 trienes and tetraenes dominated the hydrocarbon distributions in 53 m particles particle size and depth distributions of the hydrocarbons demonstrate the importance of algal hydrocarbons in surface waters coupled with increased abundances of bacterial hydrocarbons especially in the 53 m particles in the anoxic zone these observations illustrate the importance of oxic anoxic interfaces even in the oceanic water column as zones of intense microbial alteration of organic matter and as sources of some of the organic compounds found in sediments

organic geochemistry of the lower miocene oberdorf lignite styrian basin austria its relation to petrography palynology and the palaeoenvironment abstract in the oberdorf trough at the northwestern margin of the styrian basin austria an up to 36 m thick lower miocene ottnangian lignite seam occurs within the fluvial koflach voitsberg formation previous results indicate that the lignite originated in a topogenous mire within a wet forest swamp palaeoenvironment differences in soluble organic matter som yield of borehole samples from the lignite seam are related to free lipids present in plant waxes or resins and the presence of thermally labile polymers indicated by the contents of liptinite macerals i e resinite suberinite and liptodetrinite the n alkane distribution patterns are dominated by high molecular weight lipids with marked odd over even predominance originating from plant waxes a contribution of algae to the even numbered short chain lipids observed in considerable amounts in the footwall sediments is proposed terpenoid biomarkers characteristic for conifers and angiosperms were detected consistent with palynomorphic spectra which are dominated by forest swamp pollen taxodiaceae cupressaceae and pollen from plants living in a mixed mesophytic forest excellent relationships between higher plant biomarker composition and palynologic data indicate that the organic geochemical results reflect the varying inputs of coniferales vs angiosperms the data further imply that cuparene may be used for taxonomical differentiation of coniferales families organic geochemical data provide evidence that the content of land plant derived biomarkers is controlled by the input of resin rich conifers concentrations of hopanoids dominated by hop 17 21 ene generally increase towards the top of the lignite a section characterised by high extents of aromatisation of triterpenoid biomarkers the results suggest that the aromatisation of angiosperm derived biomarkers may be governed by the activity of anaerobic rather than by aerobic bacteria however changes in the depositional environment and palynologic facies during peat formation probably influenced the origin and fate of angiosperm derived triterpenoids the results indicate how biomarker composition may contribute to the evaluation of environmental changes cross correlations of organic geochemical parameters with palynological data and petrography based facies indicators will provide further insights in the peat forming vegetation and biogeochemical activities in the mire

carbon isotope behaviour in wood and cellulose during artificial aging abstract modern wood was subjected to an artificial decay process to investigate its behaviour with respect to the stable carbon isotope composition of wood and the corresponding cellulose four different woods were used namely oak quercus robur beech fagus sylvatica pine pinus sylvestris sequoia sequoiadendron giganteum and pure spruce cellulose the process of decay was simulated by heating samples in water at 180 c from minutes to months during the decay period the carbon content of wood increased to almost 70 while the cellulose content decreased gradually to zero the degradation proceeds according to a two stage process an initial very fast break down is followed by a rather slow degradation after a strong discrimination against 13 c during the initial phase the 13c 12c ratio increases again mostly up to its initial value the carbon isotope trend for cellulose shows a similar pattern though it is less pronounced maximum discrimination was 1 relative to the untreated wood 13c values of cellulose decreased by up to 0 3 the 13 c depletion is presumably a consequence of the preferential decomposition of cellulose as compared to lignin data on fossil trees are compared with the results obtained from this treatment of aging the 13 c decrease is in line with observations from these fossil woods but the ensuing 13 c enrichment is at most weakly to be seen

paleogeographic evolution of the late miocene lake pannon in central europe abstract the paleogeographic evolution of lake pannon within the pannonian basin is reconstructed with eight maps ranging from the middle miocene to the early pliocene the maps are based on the distribution of selected biozones and specific fossils and on complementary sedimentological and seismic information our reconstruction shows that the history of lake pannon can be divided into three distinct intervals an initial stage with low water level which resulted in isolation from the sea at about 12 ma and might have led to temporary fragmentation of the lake an interval of gradual transgression lasting until ca 9 5 ma and a long late interval of shrinkage and infilling of sediments that persisted into the early pliocene the deep subbasins of the lake formed during the transgressive interval in more basinward locations than the deep basins of the preceding sarmatian age the southern shoreline running parallel with the sava and danube rivers along the northern foot of the dinarides changed very little during the lifetime of the lake while the northern shoreline underwent profound changes

paleogeography and paleoecology of the upper miocene zillingdorf lignite deposit austria abstract the zillingdorf deposit formed during the late miocene filling of lake pannon and contains austria s largest lignite reserves two lignite seams are present and developed within frequently flooded low lying mires in near shore environments high sulphur contents are due to the influence of the brackish water body of lake pannon during peat accumulation a transgression forced the nw se trending shoreline northeastwards differences in soluble organic matter som yield and hydrocarbon content of borehole samples and woody macrofossils are related to differences in the content and composition of free lipids of microbial origin and or hydrocarbons derived from the biogeochemical degradation of plant tissue variations of pristane phytane ratios are interpreted to reflect differences in the redox conditions of the mire peatification in an acidic and aerobic environment is further reflected by the predominance of aromatic over saturated hydrocarbons the presence of an intense complex mixture in the gc traces due to biodegradation processes high ratios for diasterenes relative to sterenes and high concentration ratios of hopanes to hop 17 21 ene of the respective samples gelification of plant tissue is governed by microbial activity as indicated by the positive relationship between gelification index and hopanoids concentration the composition of terpenoid biomarkers indicates the predominance of gymnosperms over angiosperms and increasing proportions of angiosperms in the peat forming vegetation with decreasing depth in the upper seam from the sesqui and diterpenoids present in the lignite and fossil wood remnants a predominant role of species of the coniferales families cupressaceae taxodiaceae are concluded the preservation of plant tissue is governed by the presence absence of decay resistant gymnosperms a general influence of the floral assemblage on the isotopic composition of organic carbon of the lignite 13c 27 2 to 24 6 is proposed decomposition of plant tissue and biogeochemical carbon cycling is assumed to further affect the 13c values of the lignite carbon isotope data of fossil wood remnants are consistent with their chemotaxonomical classification as gymnosperms 13c between 22 5 and 24 9 and angiosperms 13c between 25 5 and 26 6 respectively the 13c data of the extracted cellulose reveal clear differences between fossil wood from gymnosperms average 13c 20 3 and angiosperms mean 13c 22 9 the higher isotopic difference of about 3 5 between cellulose and fossil wood compared to that found in modern trees is explained by the smaller effect of 13c discrimination for cellulose when compared with wood during decomposition

the organic geochemistry of coal from plant materials to coal coalification is a process that transforms plant remains under the influence of time temperature and possibly pressure to a black generally lustrous solid organic fossil fuel having a very complex chemistry although much has been learned in the past two centuries on coal chemistry we still have little knowledge of the way plant materials undergo these transformations the problem has been the existence of adequate characterization tools the advent of some new tools for structural elucidation of macromolecules has led to some revised thinking on coalification originally thought to be a process involving the full degradation of plant remains and subsequent reconstitution of these remains the general consensus today is that the process involves a selective preservation of certain resistant plant components followed by some minor reorganization of the biopolymers that survive the major components of plants do degrade and the resistant ones often constitute only a small fraction of the original mass of the plant materials this paper examines the most recent literature concerning coalification and focuses on the chemistry associated with coalification of certain recognizable plant remains that have been at the center of research activity for the past two decades thus we examine the recent knowledge of the chemistry of resistant biopolymers in extant and fossil wood cuticles resins spores and algae knowledge that has been assembled to establish the reaction pathways towards coal macromolecules

modes of orogen parallel stretching and extensional exhumation in response to microplate indentation and roll back subduction tauern window eastern alps the tauern window exposes a paleogene nappe stack consisting of highly metamorphosed oceanic alpine tethys and continental distal european margin thrust sheets in the eastern part of this window this nappe stack eastern tauern subdome etd is bounded by a neogene system of shear the katschberg shear zone system kszs that accommodated orogen parallel stretching orogen normal shortening and exhumation with respect to the structurally overlying austroalpine units adriatic margin the kszs comprises a 5 km thick belt of retrograde mylonite the central segment of which is a southeast dipping low angle extensional shear zone with a brittle overprint katschberg normal fault knf at the northern and southern ends of this central segment the kszs loses its brittle overprint and swings around both corners of the etd to become subvertical dextral and sinistral strike slip faults the latter represent stretching faults whose displacements decrease westward to near zero the kinematic continuity of top east to top southeast ductile shearing along the central low angle extensional part of the kszs with strike slip shearing along its steep ends combined with maximum tectonic omission of nappes of the etd in the footwall of the knf indicates that north south shortening orogen parallel stretching and normal faulting were coeval stratigraphic and radiometric ages constrain exhumation of the folded nappe complex in the footwall of the kszs to have begun at 23 21 ma leading to rapid cooling between 21 and 16 ma this exhumation involved a combination of tectonic unroofing by extensional shearing upright folding and erosional denudation the contribution of tectonic unroofing is greatest along the central segment of the kszs and decreases westward to the central part of the tauern window the kszs formed in response to the indentation of wedge shaped blocks of semi rigid austroalpine basement located in front of the south alpine indenter that was part of the adriatic microplate northward motion of this indenter along the sinistral giudicarie belt offsets the periadriatic fault and triggered rapid exhumation of orogenic crust within the entire tauern window exhumation involved strike slip and normal faulting that accommodated about 100 km of orogen parallel extension and was contemporaneous with about 30 km of orogen perpendicular north south shortening of the etd extension of the pannonian basin related to roll back subduction in the carpathians began at 20 ma but did not affect the eastern alps before about 17 ma the effect of this extension was to reduce the lateral resistance to eastward crustal flow away from the zone of greatest thickening in the tauern window area therefore we propose that roll back subduction temporarily enhanced rather than triggered exhumation and orogen parallel motion in the eastern alps lateral extrusion and orogen parallel extension in the eastern alps have continued from 12 to 10 ma to the present and are driven by northward push of adria

the geology and coal petrology of a miocene lignite profile at meliadi mine katerini greece abstract the present study describes vertical variations in petrographic composition of a miocene lignitebearing succession from the moschopotamus basin greece the lignite beds are described megascopically in terms of lithotypes and microscopically by maceral contents examination of lithotype variations within the seams and the distribution of facies critical macerals such as humotelinite and humodetrinite and the relatively low inertinite contents suggest a formation of the miocene lignites as reed marsh to wet forest type swamps in a lower delta plain depositional setting reflectances measured on the maceral type eu ulminite b range from 0 36 to 0 42 r random placing the meliadi coals into a transition zone from lignite to subbituminous coal

occurrence and geochemical significance of 1 2 5 6 tetramethylnaphthalene analysis of aromatic hydrocarbon fractions of selected coal and shale samples reveals the predominance of two specific polyalkylnaphthalenes which have been identified as 1 2 5 trimethylnaphthalene and 1 2 5 6 tetramethylnaphthalene the maturity of the samples is such that the source effect on the formation of individual molecules from biological precursors is expected to be recognisable these alkylnaphthalenes are thought to be diagenetically derived from pentacyclic triterpenoids via 8 14 seco triterpenoids which are also detectable in some of the samples investigated it is proposed that 1 2 5 6 tetramethylnaphthalene in the coal samples is formed by cleavage and methyl shift reactions from geminal c 4 methylated triterpenoids which contain a leaving group in position 3 for the shale samples degradation of monoaromatic secohopanoids must be considered as an alternative pathway

polar aromatic biomarkers in the miocene maritza east lignite bulgaria aromatic and polar compounds of lignite lithotype bitumens maritza east were analyzed diterpenoid phenols and ketophenols i e mainly ferruginol sugiol hinokione and products of their diagenetic transformations were identified as the dominant biomarkers a variety of sesquiterpenoids was present as well these compounds provided evidence for the assumption that members of the cupressaceae s 1 are the coal precursors polar triterpenoids i e lupeol lupenone adiantone and hopanones were present in subordinate quantities in the humoclarain sample these biomarkers support an input of deciduous angiosperm vegetation to the peat swamp source matter three diagenetic transformation schemes for the diterpenoid phenols ketophenols are proposed 1 ferruginol and or sugiol alteration through dehydrogenation demethylation and ring b cleavage 2 hinokione aromatization to simonellite and 3 7 ketototarol change through 7 ketototar 5 enol to 20 nor 3 oxo totara 5 10 6 dienol the identified diterpenoids demonstrated the presence of gymnospermae in the coal forming community furthermore the phenolic diterpenoids indicated a specific input of organic matter from conifers of the cupressaceae taxodiaceae or podocarpaceae as the most abundant trees in the coal forming swamp

exploring former subglacial hodgson lake antarctica paper ii palaeolimnology direct exploration of subglacial lakes buried deep under the antarctic ice sheet has yet to be achieved however at retreating margins of the ice sheet there are a number of locations where former subglacial lakes are emerging from under the ice but remain perennially ice covered one of these lakes hodgson lake 72 00 549 s 068 27 708 w has emerged from under more than 297 465 m of glacial ice during the last few thousand years this paper presents data from a multidisciplinary investigation of the palaeolimnology of this lake through a study of a 3 8 m sediment core extracted at a depth of 93 4 m below the ice surface the core was dated using a combination of radiocarbon optically stimulated luminescence and relative palaeomagnetic intensity dating incorporated into a chronological model stratigraphic analyses included magnetic susceptibility clast provenance organic content carbonate composition siliceous microfossils isotope and biogeochemical markers based on the chronological model we provisionally assign a well defined magnetic polarity reversal event at ca 165 cm in the lake sediments to the mono lake excursion ca 30 34 ka whilst osl measurements suggest that material incorporated into the basal sediments might date to 93 9 ka four stratigraphic zones a d were identified in the sedimentological data the chronological model suggests that zones a c were deposited between marine isotope stages 5 2 and zone a during stage 1 the holocene the palaeolimnological record tracks changes in the subglacial depositional environment linked principally to changing glacier dynamics and mass transport and indirectly to climate change the sediment composition in zones a c consists of fine grained sediments together with sands gravels and small clasts there is no evidence of overriding glaciers being in contact with the bed reworking the stratigraphy or removing this sediment this suggests that the lake existed in a subglacial cavity beneath overriding lgm ice in zone d there is a transition to finer grained sediments characteristic of lower energy delivery coupled with a minor increase in the organic content attributed either to increases in allochthonous organic material being delivered from the deglaciating catchment a minor increase in within lake production or to an analytical artefact associated with an increase in the clay fraction evidence of biological activity is sparse total organic carbon varies from 0 2 to 0 6 and cannot be unequivocally linked to in situ biological activity as comparisons of 13c and c n values with local reference data suggest that much of it is derived from the incorporation of carbon in catchment soils and gravels and possibly old co2 in meteoric ice we use the data from this study to provide guidelines for the study of deep continental subglacial lakes including establishing sediment geochronologies determining the extent to which subglacial sediments might provide a record of glaciological and environmental change and a brief review of methods to use in the search for life

biogeochemistry of the miocene lacustrine deposit at clarkia northern idaho u s a abstract the lipid preservation observed in the sediments from clarkia reflects an extremely immature thermal history many biomarkers have still retained functionality even after 17 20 million years the soluble components are predominantly higher plant and algal derived lipids and the original sources for these compounds are still preserved in the sediment thus biogeochemical data are in agreement with the associated palaeontological evidence chemical changes noted in the lipids preserved in these sediments are similar to those observed in modern fresh water mesotropic or eutrophic lacustrine sediments therefore it can be inferred that the processes that operate in modern lacustrine sediments are similar to those that took place within the sediments at clarkia 17 20 million years ago

the sources and deposition of organic matter in the late quaternary pigmy basin gulf of mexico abstract the concentration and carbon isotopic composition 13c of sedimentary organic carbon corg n c ratios and terrigenous and marine 13corg endmembers form a basis from which to address problems of late quaternary glacial interglacial climatic variability in a 208 7 m hydraulic piston core dsdp 619 from the pigmy basin in the northern gulf of mexico while interpretations of sedimentary 13corg time series records are often not unique paired analyses of 13corg and n c are consistent with the hypothesis that the corg in the pigmy basin is a climatically determined mixture of c3 photosynthetic terrigenous and marine organic matter confirming the earlier 13corg model of sackett 1964 a high resolution 1 4 2 9 ka sample 13corg record shows that sedimentary organic carbon in interglacial oxygen isotope sub stages 1 and 5a b are enriched in 13c average 1 values are 24 2 1 2 o and 22 9 0 7 o relative to pdb respectively while glacial isotope stage values 2 are relatively depleted 25 6 0 5 concentrations of terrigenous and marine sedimentary organic carbon are calculated for the first time using 13corg and corg measurements and empirically determined terrigenous and marine 13corg endmembers the net accumulation rate of terrigenous organic carbon is 4 3 2 6 times higher in isotope stages 2 4 than in sub stages 1 and 5a b recording higher erosion rates of terrigenous organic material in glacial times the concentration and net accumulation rates of marine and terrigenous corg suggest that the nutrient bearing plume of the mississippi river may have advanced and retreated across the pigmy basin as sea level fell and rose in response to glacial interglacial sea level change

stable carbon isotopes of amorphous kerogens from phanerozoic sedimentary rocks amorphous kerogens from phanerozoic sedimentary rocks may be divided into two groups on the basis of their 13c values h amorphous kerogens have isotopic values in the range of 24 to 20 per mil and l amorphous kerogens have isotopic values in the range of 35 to 26 per mil the occurrence of amorphous kerogens in the intermediate isotopic range from one rock unit in the data set suggests a weak continuum may exist between these two groups phytoplankton and to a lesser extent zooplankton and bacteria are considered to be the precursors for both kerogen types a plausible explanation for this dichotomy may be found in the source of co2 utilized by phytoplankton which is considered to be controlled by environmental factors h amorphous kerogens are expected to occur in silled basins that are overlain by expansive well circulated deep 500 m water where the prevailing source of carbon in the photic zone is atmospheric derived co2 conversely l amorphous kerogens are expected to occur in restricted basins that are overlain by stratified shallow 200 m water where the prevailing source of carbon in the photic zone may be organic derived co2

paleoenvironmental implications from biomarker and stable isotope investigations on the pliocene velenje lignite seam slovenia a pliocene lignite seam up to 160 m thick occurs in the velenje basin slovenia the seam originated in a topogenous mire and evolved within a non marine transgressive setting differences in soluble organic matter yield and hydrocarbon content of borehole samples from the lignite are related to differences in the composition of free lipids of microbial origin and or hydrocarbons derived from the biogeochemical degradation of plant tissue variations of the redox conditions within the mire are reflected by pristane phytane ratios the abundance of terpenoid biomarkers indicates the predominance of gymnosperms over angiosperms which is consistent with palynomorphic spectra dominated by pollen of the sequoia taxodium metasequoia plant community rather than by angiosperms evidence is also provided that the content of land plant derived biomarkers and the preservation of plant tissue is controlled by the input of resin rich decay resistant conifers sections of the seam characterized by a high degree of gelification of humotelinite gelification index show high contents of hop 17 21 ene but low hopane concentrations the results suggest that the gelification of plant tissue may be governed by the activity of anaerobic rather than aerobic bacteria despite the minor variation in the proportions of gymnosperms versus angiosperms in the peat forming vegetation a general influence of the floral assemblage on carbon isotopic composition of the coals 13c 25 3 to 27 0 is proposed carbon cycling during biogeochemical decomposition of plant tissue by bacteria is assumed to affect the 13c value of the lignite petrographic and geochemical data of gelified and ungelified fossil wood provide evidence that gelification may be governed by microorganisms e g anaerobic bacteria different from those responsible for decreasing cellulose contents during early diagenetic aerobic degradation of wood based on the molecular composition of terpenoid biomarkers the wood fragments are identified as derived from gymnosperms the relative proportions of saturated versus aromatic hydrocarbon fractions of fossil gymnosperms display a general tendency towards lower values in gelified wood remains this indicates that bacteria involved in gelification of plant tissue may also be involved in aromatisation of diterpenoid hydrocarbons the chemotaxonomical classification of the macrofossils as gymnosperms is corroborated by the mean carbon isotopic compositions of the macrofossils 13c 24 5 and the extracted cellulose 13c 22 0 the higher isotopic difference of about 2 5 between cellulose and fossil wood compared to that found in modern trees can most probably be explained by the smaller effect of 13c discrimination for cellulose when compared with wood during decomposition chem geol 158 1999 121 compared with the coals the 13c values of wood and extracted cellulose are affected to a minor extent by microbial activity

investigation of the inner structure of la crosa de sant dalmai maar catalan volcanic zone spain abstract la crosa de sant dalmai volcano is the largest volcanic edifice of the catalan volcanic zone ne spain it is a very well preserved maar type structure 1 5 km in diameter excavated at the contact between a hard substrate and a soft substrate formed by palaeozoic granites and pliocene and quaternary gravels respectively in order to infer the uppermost inner structure of la crosa de sant dalmai maar and to characterise its main geological and tectonic constraints we have performed a multiparametric geophysical study including gravimetry magnetometry self potential and electrical resistivity tomography the results obtained together with a field geology revision and additional geological data from two drill cores provide a detailed picture of the post eruptive maar infill sequence as well as of the uppermost part of the maar diatreme structure this information helps in understanding the origin and subsequent evolution of the volcano which included an alternation of phreatomagmatic and strombolian phases geophysical data show that the last strombolian phase which culminated with the formation of a scoria cone inside the maar was associated with a nw se trending regional fault the little erosion and degradation of the original tephra ring suggest a much younger age of la crosa de sant dalmai maar than was previously stated

revised wonoka isotopic anomaly in south australia and late ediacaran mass extinction the global late ediacaran shuram wonoka carbon isotope anomaly has been regarded as the largest and longest known isotopic anomaly in the ocean assuming that all ediacaran carbonate is marine disregarding carbonate in south australia shown here to be palaeosol or palaeokarst the synchronous marine organic carbonate excursion is only 8 for 13 c organic and 6 for 13 c carbonate and lasted less than a million years this revised magnitude and duration is comparable with perturbations across the permian triassic boundary and correlative with a global late ediacaran acritarch mass extinction like permian triassic isotopic excursions the revised organic carbonate wonoka excursion may also have been a greenhouse palaeoclimatic warm spike which terminated valley incision and glacioeustatic drawdown during the mid ediacaran fauquier glaciation and preceded chill of the late ediacaran billy springs glaciation supplementary material measured sections and tables of mineral and grain size proportions major element and stable isotope analyses are available at www geolsoc org uk sup18756

depositional environment of the late miocene hausruck lignite alpine foreland basin insights from petrography organic geochemistry and stable carbon isotopes abstract lignites and fossil wood from two boreholes in the late miocene hausruck district alpine foreland basin austria were investigated with respect to organic carbon and total sulfur contents ash yields maceral composition organic geochemistry and stable carbon isotope ratios the lignites from the two sampled profiles differ in sulfur contents and petrography based facies indicators gelification index gi tissue preservation index tpi the results point to drier and more acidic conditions in the part of the mire sampled at drill site lukasberg whereas the lignites from kalletsberg formed under near neutral conditions due to a raised ground water table the different depositional environments are supported by the paleogeographic positions of the boreholes borehole lukasberg is located within a paleo valley whereas borehole kalletsberg is located at the deeper part of a basin situated south and southwest of the hausruck area environmental changes with time within the mire are confirmed by the molecular composition of the soluble organic matter som differences in pristane phytane ratio isomerisation of hopanes at position 17 concentrations of hopanes and in the ratio of hopanes to hop 17 21 enes are related to the extent of gelification of plant tissue sulfur content and ph values caused by differences in ground water table the variable contents of individual terpenoid hydrocarbons derived from land plants indicate that angiosperms and conifers contribute to peat formation in the hausruck district in variable proportions overall angiosperm biomarkers slightly predominate the tissue preservation index tpi within the kalletsberg profile is probably governed by the proportion of decay resistant conifers as indicated by the correlation between tpi and biomarker composition of the coals correlations between 13 c values of the lignites between 24 9 and 27 4 and their non hopanoid terpenoid composition indicate the major influence of changes in peat forming vegetation on the carbon isotopic composition of the coals in the hausruck district carbon isotope data of macrofossils are consistent with their taxonomical classification as conifers 13 c between 22 7 and 25 1 and angiosperms 13 c between 25 5 and 26 6 respectively the 13 c data of the extracted cellulose reveal clear differences between fossil wood from gymnosperms average 13 c 21 0 and angiosperms mean 13 c 23 4

palaeoenvironment assessment of pliocene lom lignite bulgaria from bitumen analysis and preparative off line thermochemolysis abstract the dacian coal bearing province is located in nw bulgaria coal formation is thought to be connected with desiccation of the dacian basin during a prolonged regression in the late pontian and pliocene dacian romanian age a lom lignite sample was characterized via micropetrography bulk chemical analysis spectral methods and thermochemolysis the pollen record was poor suggesting coal formation under oxygen rich conditions during peatification straight chain alkanes alkan 2 ones alkanols des a triterpenoids aromatized triterpenoids aromatized hopane hopene hopanes and triterpenoids with a strong dominance of oleanane derived structures were present in the extracted bitumen the residue after extraction was subjected to preparative off line tetramethylammonium hydroxide tmah thermochemolysis the aliphatic products released were c22 c27 fatty acid fa methyl esters i e methoxymethyl esters c22 c28 even numbered diacids dimethyl esters with a smooth distribution and traces of i and ai c15 acid methyl esters trapped and bound fas were distinguished using tetraethylammonium acetate teaac treatment the main thermochemolysis products were phenols structurally related to lignin vanillyl and syringyl units were produced in similar amounts indicating nonwoody angiosperm vegetation as the main plant input to the palaeo swamp probably originating from marsh or grassland sources the bitumen provided unequivocal information for an angiosperm contribution to the mire while the results of the tmah pyrolysis revealed a concomitant angiosperm and gymnosperm input the biomarker assemblage makes the lom lignite unique in bulgaria all the other bulgarian neogene lignites being dominated by coniferous vegetation with only traces of angiosperm contributions

environmental history of the german lower rhine embayment during the middle miocene as reflected by carbon isotopes in brown coal stable carbon isotope investigations have been carried out on miocene brown coal from the garzweiler seam of the german lower rhine embayment material studied included fossil wood from seven different taxa and brown coal matrix isotope results from macrofossil analysis show variations of more than 6 within individual samples and reveal a general isotopic difference between angiosperm and gymnosperm wood specimens according to mean carbon isotope values found for gymnosperms angiosperms and brown coal matrix 23 3 26 0 and 25 8 the peat forming vegetation of the garzweiler seam was dominated by angiosperm taxa results from brown coal matrix establish a continuous high resolution depth profile of carbon isotope variations during the late middle miocene they show a significant and characteristic isotope pattern with distinct medium and short term cycles high frequency variations in the two main units of garzweiler seam locally split into three units the medium term 13c variations are most likely caused by varying proportions of gymnosperms within the peat forming vegetation while high frequency oscillations seem to be a direct signal of environmental changes a long term decline of carbon isotope values observed within the complete garzweiler seam from base to top is presumably due to a cooling trend in the miocene

parameters determining the carbon isotopic composition of coal and fossil wood in the early miocene oberdorf lignite seam styrian basin austria abstract petrographical and geochemical data of gelified and ungelified fossil wood from the early miocene oberdorf lignite seam styrian basin austria provide evidence that the early diagenetic aerobic degradation of wood by fungi may be followed by further decomposition under reducing conditions by the activity of anaerobic bacteria based on the molecular compositions of terpenoid hydrocarbons the wood fragments in the lignite are identified as gymnosperms this result is corroborated by the mean isotopic composition 13c 24 2 of the macrofossils the isotopic difference between fossil wood and extracted cellulose of most samples 3 9 2 5 is higher than in modern trees which can be explained by the smaller effect of 13c discrimination during decomposition of cellulose when compared with wood the mean carbon isotope values found for gymnosperms and coals 24 2 and 24 7 respectively confirm the results from biomarker analyses indicating that the peat forming vegetation of the oberdorf seam was dominated by gymnosperm taxa minor variation in the relative contributions of gymnosperms and angiosperms to coal deposition is of negligible influence on the isotopic composition of the coals cross correlations between 13c of the coals soluble organic matter yield and the proportions of liptinite macerals of higher plant origin imply that the carbon isotopic composition may be affected by the contents of plant lipids because of their 13c values ranging from 5 to 10 less than whole plant tissue values an isotopic shift of the coals towards more negative values due to the activity of prokaryotes i e anaerobic bacteria in organic matter degradation is proposed the results obtained from the early miocene oberdorf lignite indicate that the carbon isotope ratios of the coals are primarily affected by varying contributions of different parts of whole plant tissue due to their different isotopic and molecular compositions e g epicuticular leaf waxes resins wood and their different decay resistance against the early diagenetic changes involved in organic matter decomposition carbon cycling during anoxic decomposition of plant derived organic matter is assumed to affect the 13c values of coal 13c values of wood and extracted cellulose are affected only to a minor extent