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

the source and paleoclimatic implication of hydrogen isotopic composition of n alkanes in sediments from the yixian formation western liaoning province ne china abstract hydrogen isotopic composition of n alkanes was measured in sediments from an excavated profile of the early cretaceous yixian formation in liaoning province ne china aiming to assess the significance of the d value of n alkanes in ancient lacustrine sediments as the indicator for determining the source inputs of organic matters and paleoclimatic conditions the d values of n alkanes are in the range of 250 to 85 and display an obvious three stage variation pattern through the profile which is consistent with the distribution of the dominated n alkanes and the profile of their 13 c values the d and 13 c values of n alkanes suggest that short chain n alkanes are primarily derived from photosynthetic bacteria and algae n c 29 and n c 31 are mainly originated from terrestrial higher plants n c 28 and n c 30 may be derived from the same precursor but via the different biological mechanism of hydrogen isotopic fractionation while the source inputs of medium chain n alkanes are more complicated with n c 23 being derived from some specific algae or biosynthesized by various aquatic organisms the paleoclimatic conditions are reconstructed via two approaches the reconstructed hydrogen isotopic values of lake water and meteoric water expressed as d lw and d mw respectively were at the intervals of 51 8 to 17 0 and 118 1 to 43 5 respectively indicating a general climate transition from semi arid to arid the calculated d lw mw values vary from 37 0 to 89 1 and display a similar but a significant large scale variation trend with the d c 23 long 28 8 to 85 0 long represents long chain n alkanes and d mid long 15 4 to 43 4 mid represents medium chain n alkanes values the discrepancy may be attributed to the source input overlap for n alkanes and the uncertainties of e water lipid values the coupling of d c 23 long d mid long and d lw mw values with the paleoclimatic evidence indicates that the d values of n alkanes could be more sensitive to the change of paleoclimatic conditions

novel family of hexacyclic hopanoid alkanes c32c35 occurring in sediments and oils from anoxic paleoenvironments abstract four novel hexacyclic alkanes fairly common in crude oils and rock extracts from evaporitic series have been tentatively identified on the basis of gc ms data as c 32 c 33 c 34 and c 35 hexahydrobenzohopanes these structures only recorded in carbonate anhydrite sequences i e very anoxic paleoenvironments tend to concentrate when pristane to phytane ratios increase changes in their relative concentration to hopanes appear to be more related to variations in source and or environmental conditions than to maturity the ratio of the novel hexacylic c 35 hopane to c 35 hopane compared with other biomarker ratios suggests that hexacyclic alkanes and hopanes are byproducts of the same hopanoid precursors via different chemical reactions in addition the novel hexacyclic alkanes are bacterially resistant and may serve as a useful family to define the paleoenvironment viz very anoxic of the parent source rock of a drastically biodegraded oil

distribution and significance of novel low molecular weight sterenes in an immature evaporitic sediment from the jinxian sag north china abstract an unusual series of c 22 c 27 monounsaturated sterenes and c 24 c 30 tetracyclic terpanes 17 21 seco hopanes were detected in relatively high concentrations in an immature evaporitic marl sediment of the jinxian sag bohai bay basin north china the site of unsaturation in these novel sterenes is assigned tentatively to the d ring on the basis of mass spectral interpretation which also distinguishes them from reported unsaturated sterenes other hydrocarbon biomarker or stable isotope characteristics are indicative of microbial e g methyl hopanes phytoplankton or higher plant depleted 13 c values of isoprenoids and hopanes inputs and an anoxic carbonate depositional environment hexacyclic hopanes tetracyclic terpanes the hydrocarbon composition showed no obvious biodegradation and the relatively high concentration of unsaturated terpenoids e g gammacerene and low values of other established maturity parameters t s t m 0 23 r o 0 44 t max 417 c are consistent with sediments of low maturity the novel low molecular weight sterenes and the tetracyclic terpanes may be early diagenetic products of microbial sources in a carbonate environment

the microbial input in carbonate anhydrite facies of a sabkha palaeoenvironment from guatemala a molecular approach abstract nine representative rock samplesincluding four anhydrites an oil stained dolomite and a laminated mudstone source rock from a sabkha type palaeoenvironment la felicidad 1 well guatemala have been compared in order to tentatively characterize each facies by a geochemical signature each sample has been studied by using basic parameters toc rock eval pyrolysis yields and analyses of alkanes and aromatics by computerized gc ms the following families of compounds have been reviewed n alkanes branched and cyclic alkanes n alkylbenzenes benzohopanes monoaromatic steroids d ring aromatic 8 14 secohopanoids alkylnaphthalenes alkylphenanthrenes alkyldibenzothiophenes and triaromatic steroids despite close geochemical relationships of all the sample a more in depth investigation taking into account molecular patterns and semi quantitative data reveals significant differences among the samples anhydrites may be differentiated from carbonates which illustrates the efficiency of organic geochemistry in environmental palaeoreconstruction even in organiccarbon lean sediments toc 0 04 0 08 in anhydrites in these anoxic marginally mature sediments the strong predominance of triterpanes over steranes tt to st 20 associated with other molecular features leads to the conclusion that the main contribution to the organic matter of all facies is by bacteria several prominent components including novel families iso c23 and iso c27 alkanes tetracyclic terpanes d ring aromatic 8 14 secohopanoids 1 phenylpentadecane undecylnaphathalene and their mono and dimethylated counterparts have been interpreted as derived from halophilic bacteria these conclusions may be extended to all crude oils from the same area which may be considered as true bacterially derived petroleums the la felicidad 1 well data are discussed with reference to other palaeosabkha type sequences from the sw aquitaine basin france in which the bacterial input is less important however in these sabkha sequences 1 phenylpentadecane undecylnaphthalene and related structures have also been identified

maastrichtian oil shale deposition on the southern tethys margin egypt insights into greenhouse climate and paleoceanography abstract a comprehensive set of organic and inorganic geochemical proxies clay mineralogy and molecular fossils are presented from two biostratigraphically well dated oil shale horizons of egypt within the upper cretaceous duwi and dakhla formations the studied oil shales were deposited within intracratonic sedimentary basins in a broad northern african epeiric sea calcareous nannofossil biostratigraphy indicates that the oil shales range from early to late maastrichtian in age covering nannofossil zones uc18 uc19 and uc20 the oil shales contain smectite and kaolinite as the main clay minerals that formed by weathering of precursor basement rocks the relative abundances of clay minerals and several geochemical proxies e g c value cia ga rb rb sr and sr cu along with the occurrence of warm water nannofossil taxa demonstrate that the maastrichtian oil shales accumulated under a warm arid to humid greenhouse climate during a general maastrichtian cooling trend this episode of oil shale deposition in egypt coincided with the first potential imprint of the global warming that has been recorded during early to late maastrichtian times 70 6 67 7 ma elevated eolian terrigenous input was recorded within the duwi formation oil shales shown by high ti al si al zr al and low la lu ratios the duwi formation environment was characterized by enhanced salinity and a stratified water column compared to that of the dakhla formation shown by elevated values of the gammacerane index tetracyclic terpane carotene and sr ba ratio the caco3 content and carbonate siliciclastic ratio indicate that the dakhla formation oil shales were deposited during a relative sea level rise in a deeper marine setting than the duwi formation oil shales the data further imply a wind driven upwelling scenario of nutrient input s that simulated primary production and increased organic matter fluxes thus paleoclimate and paleoceanography had a considerable impact on organic matter enrichment

the identification of crocetane in australian crude oils abstract the c 20 irregular isoprenoid crocetane 2 6 11 15 tetramethylhexadecane has been unambiguously identified in a series of western australian crude oils from the canning ordovician devonian and perth lower triassic basins pmi 2 6 10 15 19 pentamethylicosane was found to co occur with crocetane in the same samples in addition a newly observed series of c 22 c 24 irregular isoprenoids possessing the same carbon skeleton have also been tentatively identified in each of these crude oils on the basis of gc retention times and mass spectral characteristics this may indicate a source for crocetane in the canning and perth basin crude oils from the diagenesis of pmi the stable carbon isotopic composition for combined crocetane phytane in these samples suggests crocetane is not unusually depleted in 13 c compared with all previous reports this is the first reported occurrence of biomarkers attributable to methanogenic archaea in crude oils

gravitational spreading controls rift zones and flank instability on el hierro canary islands ocean island volcanoes frequently develop local rift zones associated with flank movement and flank collapses the ocean island el hierro grew by coalescence and collapse of three volcanic edifices which are an elongated topographic ridge the southern ridge and two semi circular volcanic cones tinor volcano el golfo volcano during edifice growth and volcano coalescence eruption fissures nucleated into rift zones that developed a complex triangle pattern in scaled analogue experiments we could successfully reproduce the geometry of rift zones and unstable flanks as observed on el hierro the experimental results suggest that the rift configuration on el hierro is the result of gravitational volcano spreading over deformable basal substrata rather than of deep seated magma updoming as thought previously this paper elucidates the importance of the basal substratum and gravitational spreading and the relationship to rifting and flank instability on el hierro island and may help in understanding similar volcano architectures elsewhere

cyclic terpenoids of contemporary resinous plant detritus and of fossil woods ambers and coals abstract cyclic terpenoids present in the solvent extractable material of fossil woods ambers and brown coals have been analyzed the sample series chosen consisted of wood remains preserved in holocene to jurassic sediments and a set of of ambers from the philippines copalite israel canada and dominican republic the brown coals selected were from the fortuna garsdorf mine and miocene formations on fiji the fossil wood extracts contained dominant diterpenoid or sesquiterpenoid skeletons and aromatized species were present at high concentrations with a major amount of two ring aromatic compounds tricyclic diterpenoids were the predominant compounds in the ambers aromatized derivatives were the major components consisting of one or two aromatic ring species with the abietane and occasionally pimarane skeletons the saturated structures were comprised primarily of the abietane and pimarane skeletons having from three to five carbon c1 c2 etc substituents kaurane and phyllocladane isomers were present in only minor amounts bicyclic sesquiterpenoids as saturated and partial or fully aromatized forms were also common in these samples but only traces of sesterterpenoids and triterpenoid derivatives were found the brown coal extracts were composed of major amounts of one and two ring aromatized terpenoids with a greater proportion of triterpenoid derivatives than in the case of the woods and ambers this was especially noticeable for the german coal where the triterpenoids were predominant open c ring aromatized structures were also present in this coal steroid compounds were not detectable but some hopanes were found as minor components in the german brown coal an overview of the skeletal structure classes identified in each sample as well as the general mass spectrometric characteristics of the unknown compounds are included in the present paper it can be concluded from these structural distributions that aromatization is the main process for the transformation of terrestrial cyclic terpenoids during diagenesis constituting a general pathway for all terpenoids

neoproterozoic early cambrian biota and ancient niche a synthesis from molecular markers and palynomorphs from bikaner nagaur basin western india abstract the time frame of present study is neoproterozoic early cambrian an enigmatic and consequential time in the history of earth the present study elucidates the terminal proterozoic biota and palaeoenvironment by characterizing the soluble and insoluble fractions of organic matter extracted from sediment core samples recovered from marwar supergroup bikaner nagaur basin western india the normal alkanes range from c15 to c33 wherein c19 to c21n alkanes predominate and carbon preference index ranges from 1 12 to 1 19 pristane phytane ratio varies between 0 9 and 1 2 the kerogen matter occurs as homogenous laminae and discrete organic remains which are mostly derived from microbial mat triterpenoids include cheilanthanes and hopanes which are confirming evidences of microbial input algal presence has also been confirmed from palynological data green algae evolved to be a major biota during the neoproterozoic early cambrian time and this is validated by the appreciable abundance of c29 steranes in the bitumen fraction the amorphous pieces of kerogen residues lack any visibly distinct internal features however a very few simple ornamented acritarchs like micrhystridium sp lophosphaeridium sp and leiosphaeridia sp are observed in the organic residues micro ftir spectroscopy of the amorphous organic particles reveals the presence of long chain aliphatic components and unusually high c c aromatic ring stretching band the organic remains were deposited in restricted marine water and elevated saline condition as indicated by several salinity biomarkers the present study clearly demonstrates a microbial mat dominated niche with significant eukaryotic green algae that had been capable of surviving in the high salinity of the terminal proterozoic oceans

geochemical characterization of the devonian mississippian woodford shale from the mcalister cemetery quarry criner hills uplift ardmore basin oklahoma abstract it has been estimated that technically recoverable reserves from shales in the continental u s are believed to be approximately 24 billion barrels of oil bbo and 750 trillion cubic feet tcf of gas in oklahoma the most important hydrocarbon source rock is the woodford shale proposed to be the source of some 70 of the state s liquid hydrocarbon reserves such a regionally widespread source rock provides potential for both academic study and industrial opportunities in this study representative samples of the woodford shale from the mcalister quarry outcrop have been characterized by a variety of geochemical techniques toc values range from 0 07 to 15 6 wt and based on rock eval pyrolysis most of the samples plot within the type i ii kerogen range with several low toc samples plotting in the type iii kerogen range toc and biomarker parameters suggests that two sections of the upper woodford are immature paleosols having been subaerially exposed due to abrupt episodes of sea level fall during the late devonian evidence for these zones of paleoweathering includes highly depleted toc increased oxygen index oi values loss of n alkanes decreases in the aryl isoprenoid ratio air sesquiterpenoids cheilanthanes hopanoids and decreases in many of the polycyclic aromatic hydrocarbons pahs the values of several paleoenvironmental proxies for samples immediately following the frasnian famennian f f stage extinction boundary within the upper woodford suggests that a large influx of weathered terrigenous material occurred at that time the presence of pyrogenic compounds implies that paleowildfires were widespread throughout the middle and late devonian in the north american midcontinent it is possible that these influxes of weathered terrestrial organic material stimulated algal blooms that led to the anoxic water column conditions often attributed to the f f stage extinction event investigation of the stratigraphic framework of these source rocks assists in evaluating their potential as hydrocarbon producers and or unconventional reservoirs integration of geochemical data adds another powerful dimension to this approach it has been proposed that the woodford shale was deposited during a 2nd order depositional sequence the lower member represented the transgressive systems tract tst the upper member the highstand systems tract hst and the middle member bridging the transition between the two numerous 3rd order parasequences were also identified as being part of the overall 2nd order sequence and could be correlated to the devonian sea level curve the major objectives of the study were while this study focuses locally on the mcalister quarry samples it is also of regional importance the woodford is a prolific source rock throughout the anadarko basin and has been the subject of extensive exploration and production efforts particularly in the past decade with the development of horizontal drilling and hydrofracturing techniques continued investigation of the heterogeneity of the shale will greatly enhance the ability to predict more productive facies within the formation throughout the basin

novel aromatic hydrocarbons of probable bacterial origin in a jurassic lacustrine sequence novel series of aromatic hydrocarbons apparently bacterially derived were detected by gc ms analysis of an oil and three samples of its source rock in addition to high levels of known bacterial marker compounds hopanes benzohopanes and d ring monoaromatic 8 14 secohopanoids all samples exhibited a new series of aromatic secohopanoids which appeared to comprise pairs of c28 c31 demethylated counterparts of the regular d ring monoaromatic 8 14 secohopanoids lacking either the c 27 or more probably the c 28 methyl group further new series appeared to be composed of c28 c30 analogues of the regular and demethylated monoaromatic secohopanoids with an additional c c bond in the e ring alkylnapthalene distributions in the rock samples were dominated by 1 1 5 6 tetramethyl 1 2 3 4 tetrahydronaphthalene 1 2 5 trimethylnapthalene and 1 2 5 6 tetramethylnapthalene deriving from degradation of aromatic 8 14 secohopanoids three prominent phenanthrene analogues of these napthalene derivatives appeared to be present exhibiting similar relative abundance trends in the rock samples which suggests common bacterially derived precursors

stable hydrogen isotopic composition of hydrocarbons in torbanites late carboniferous to late permian deposited under various climatic conditions we measured the stable hydrogen isotopic composition d of selected aliphatic compounds in torbanites from scotland and australia covering the late carboniferous to the late permian the torbanites contain organic matter predominantly from a single algal source botryococcus braunii and are of similar thermal maturity the d values of n alkanes in the extracts appear to reflect the depositional palaeoclimate of each torbanite in response to the typical d values of meteoric waters the d values of n alkanes in torbanites deposited at high latitude under glacial conditions are depleted in deuterium by up to 70 relative to n alkanes in a torbanite deposited at low latitude under a tropical climate regime torbanites deposited in mid latitude regions under cool temperature conditions contain n alkanes with d values between those of n alkanes in tropical and glacial sediments a saw toothed profile of d values obtained for the n alkanes in the australian torbanites is attributed to a dual source system perhaps a predominant b braunii input with a second minor contribution from land plants pristane and phytane from two australian torbanites are significantly depleted in deuterium relative to n alkanes in the same samples and a significant difference between the d values of pristane and phytane is suggested to be caused by different sources for the two isoprenoids or isotope effects associated with their derivation from a common phytol precursor the offset between the d of values of n alkanes and isoprenoids is similar to that found in modern biological samples indicating that their indigenous d signatures may have been preserved for at least 260 280 million years

source rock characterization of the cretaceous sarvak formation in the eastern part of the iranian sector of persian gulf cenomanian middle sarvak rock samples were collected from various parts of the eastern iranian sector of the persian gulf and analyzed for quantity quality maturity and depositional environment of the organic matter by rock eval pyrolysis gas chromatography gc gas chromatography mass spectrometry gc ms pyrolysis gas chromatography mass spectrometry py gc ms kerogen stable carbon isotopic signatures elemental composition and petrography the results indicate that the organic matter has mainly good to very good hydrocarbon generation potential corresponding to kerogen types i ii and ii s the maturity increases from immature in the western section to early mature in the eastern section of the study area in addition biomarker parameters indicate a marine carbonate depositional environment for the middle sarvak formation and deposition under anoxic condition according to hydrocarbon potential maturity and oil source rock correlation the middle sarvak is the main source rock charging the late cretaceous upper sarvak ilam reservoirs of south eastern part of the persian gulf

stratigraphic distribution of macerals and biomarkers in the donets basin implications for paleoecology paleoclimatology and eustacy abstract more than one hundred and thirty coal seams and coaly layers occur in the donets basin donbas twenty eight 52 samples of them ranging in age from serpukhovian late mississipian to gzhelian late pennsylvanian 33 clastics and three limestones were studied in terms of maceral composition sulphur contents and biomarker distribution diterpanes are used to estimate the contribution of different groups of plants and the height of the water table in the swamp hopanes are a measure of bacterial activity in the peat and steranes indicate the relative input of wood and algae stratigraphic trends in these parameters are discussed in relation to paleoenvironment climatic changes and eustacy a tropical climate prevailed in the donbas from serpukhovian to kasimovian times nevertheless periods with drier and wetter conditions can be distinguished based on maceral and biomarker data relatively dry conditions are observed during serpukhovian and vereian times whereas wetter climates with a maximum of coal deposition occurred during the late bashkirian most of the moscovian and the earliest kasimovian no economic coal seams are hosted in upper kasimovian and gzhelian deposits a result of a change to an arid climate our data also suggest climatic changes during sequences of different order for the second order third order and fourth order sequences relatively dry or wet conditions occurred during coal deposition in the lowstand systems tract an intermediate climate during the transgressive systems tract and the maximum flooding and a wet climate during the highstand systems tract the results for high frequency sequences support the cecil s paleoclimatic model an intermediate paleoclimate during lst sandstone and levee siltstone a wet climate during early tst coal and a dry climate during late tst limestone mfs claystone and hst deltaic siltstone coals deposited during maximum flooding periods are more enriched in c27 steranes derived from algae and contain lower proportions of c29 steranes derived from the wood of higher plants

vascular plant biomarker distributions and stable carbon isotopic signatures from the middle and upper jurassic callovian kimmeridgian strata of staffin bay isle of skye northwest scotland the molecular and stable carbon isotopic composition of higher plant biomarkers was investigated in middle to upper jurassic strata of the isle of skye northwest scotland aromatic hydrocarbons diagnostic of vascular plants were detected in each of nineteen sedimentary rock samples from the early callovian to early kimmeridgian interval a succession rich in fossil fauna including ammonites that define its constituent chronozones the higher plant parameter hpp and higher plant fingerprint hpf calculated from the relative abundance of retene cadalene and 6 isopropyl 1 isohexyl 2 methylnaphthalene ip ihmn exhibit several large fluctuations throughout the skye succession studied these molecular profiles contrast with both 1 the more uniform profiles previously observed in jurassic successions putatively of the same age from other palaeogeographical settings including the carnarvon basin western australia and 2 the steady rise in global sea level during this interval this suggests that the hpf profiles of jurassic marine successions may not be reliable indicators of global climate change our results indicate that other factors such as local tectonism resulting in changes to the relief and landscape of the hinterland likely influenced the palaeoflora and the mode of transport of its detritus into adjacent marine depocentres however the skye succession showed similar 13c profiles of total organic carbon toc comprising mainly fossil wood the vascular plant biomarker retene and a predominant phytoplanktonic biomarker phytane the apparent isotopic relationship between terrigenous and marine derived biomarkers supports a strong coupling of the atmosphere and ocean the maximum isotopic excursion occurs in the cardioceras cordatum ammonite biozone of the early to middle oxfordian which may be indicative of changes in atmospheric and oceanic levels of co2

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

hydrocarbon generation potential of triassic mudstones in the junggar basin northwest china triassic mudstones in the junggar basin of northwest china especially those of the upper triassic baijiantan formation which formed during a lake flooding event are the most important set of cap rocks in the basin these mudstones presumably have hydrocarbon generation potential although this potential has not been documented here we provide new organic geochemical and geological background data on these mudstones and discuss their hydrocarbon generation potential geochemical analyses were performed on available samples collected from more marginal shallow lake facies in the central basin area these analyses indicated that these rocks contain about 1 0 total organic carbon toc the organic matter type is predominantly type iii kerogen derived mainly from terrestrial higher plants the organic matter underwent maturation in uplifted areas and reached higher maturity levels in depressions within the basin thus the triassic mudstones may have a potential for hydrocarbon generation during the lake flooding period especially for gas and hence deserve attention in future exploration more research needs to be conducted on the generation potential of these units including oil besides gas as few deep lake facies samples from depressions in the basin are currently available for investigation

molecular and stable carbon isotopic composition of monomethylalkanes from one oil sand sample source implications abstract unusually abundant long chain monomethylalkanes mmas c 25 c 36 and their short chain homologues c 14 c 22 have been tentatively identified in a late triassic oil sand sample from the lunnan oilfield tarim basin nw china molecular distributions and stable carbon isotopic compositions of these compounds have been determined to investigate their bio and or geosynthetic sources the results show that the most abundant isomers of short chain mmas were 4 methyl m z 70 5 methyl m z 84 6 methyl m z 98 and 7 methyl m z 112 alkanes whereas in long chain mmas there is a clear predominance of the 9 methyl and 10 methyl isomers combined with the compound specific stable carbon isotopic analysis it is concluded that short chain mmas and long chain mmas must have different sources the similar isotopic compositions of mmas and n alkanes in this sample suggest that they may share the same sources the short chain mmas as previously suggested are probably related to a cyanobacterial origin while the long chain mmas may be mainly associated with microorganisms or heterotrophic bacteria rather than cyanobacteria

geochemical study on a well in the western canada basin relation of the aromatic distribution pattern to maturity of organic matter abstract thirty one rock samples from a western canada basin well have been analysed for aromatics using glass capillary gas chromatography with simultaneous flame ionization and sulfur selective flame photometric detection a uniform aromatic distribution pattern with a marked predominance of di and tricyclic aromatic hydrocarbons was observed throughout a depth interval of 3000 meters comprising cretaceous and jurassic sediments the very high relative abundance of sulfur aromatics at two narrow intervals in the triassic and mississippian is attributed to a major change in facies gradual changes with increasing depth have been observed for a series of compound ratios which had been calculated from the isomers of methyl and dimethylphenanthrene and their parent compounds these changes reflect the increasing thermal maturation of the sedimentary organic matter a methylphenanthrene index mpi has been introduced which exhibited a very good correlation with vitrinite reflectance data the mpi is the first maturity parameter which is based on a series of aromatic hydrocarbons this hydrocarbon internal maturity parameter permits the recognition and definition of maturity levels in extracts which can be compared to the maturity e g vitrinite reflectance of source rocks

a model for atmospheric co 2 over phanerozoic time a new model has been constructed for calculating the level of atmospheric co sub 2 over phanerozoic time which is much simpler mathematically than the blag model but more complex geologically and biologically results suggest that there has been a notable pattern of varying atmospheric co sub 2 level over the past 570 my with high levels during the mesozoic and early paleozoic and low levels during the permo carboniferous and late cenozoic sensitivity analysis shows that within reasonable limits of the principal governing parameters this qualitative trend of varying co sub 2 is relatively insensitive to the actual values chosen for these parameters causes of the co sub 2 variation are multiple and no single geological or biological process can be called upon to explain all co sub 2 variation for all time the calculated trend of co sub 2 over time agrees well with independent estimations of paleoclimates thus the greenhouse theory of paleoclimate on a long geological time scale is supported by the results of the present study

glacial interglacial environmental changes inferred from molecular and compound specific δ13c analyses of sediments from sacred lake mt kenya abstract molecular stratigraphic analyses including lipid distributions and compound specific 13c measurements have been performed at 15 levels in a sediment core from sacred lake mt kenya a high altitude 2350 m a s l freshwater lake with a record extending from the last glacial 40 000 cal yr bp through the present interglacial terrestrial and aquatic organic matter sources were independently assessed using source specific biomarkers 13c values of long chain n alkyl lipids from terrestrial higher plants exhibit large glacial to interglacial shifts those from the last glacial maximum lgm 20 to 18 indicate a terrestrial vegetation dominated by c4 grasses or sedges whereas those from the early holocene 34 to 27 reflect recolonization of the catchment area by c3 plants consistent with a rapid rise in the upper treeline specific algal biomarkers including five unsaturated hydrocarbons of novel structure ascribed to the microalga botryococcus braunii were abundant as confirmed by scanning electronic microscopy sem an extreme 13c shift of over 25 is displayed by the algal biomarkers an elevated value of 5 1 at the last glacial maximum lgm contrasting with a minimum value of 30 3 at the beginning of the holocene a major change in the molecular distributions of the algal biomarkers parallels this large 13c shift with acyclic isoprenoid hydrocarbons dominating the last glacial and cyclic isoprenoid hydrocarbons the holocene the low atmospheric partial pressure of co2 pco2 at the lgm would favour photosynthetic organisms possessing co2 concentrating mechanisms including terrestrial c4 grasses and freshwater green algae hence glacial interglacial changes in pco2 and in the co2 o2 ratio in particular had a significant impact on both terrestrial and aquatic ecosystems on mt kenya in addition to the effects of climate and local environmental factors

macrocyclic alkanes a new class of biomarker a new class of cyclic hydrocarbon biomarker macrocyclic alkanes and their methylated analogues have for the first time been unambiguously identified in a botryococcus braunii rich sediment torbanite the compounds consisting of a homologous series of macrocyclic alkanes ranging from c15 to c34 and their methylated derivatives ranging from c17 to c26 were identified by using authentic standards and gc ms techniques

assessment of the difference between mid and long chain compound specific δdn alkanes values in lacustrine sediments as a paleoclimatic indicator abstract previous studies have proposed that the difference between compound specific hydrogen isotopic composition of n alkanes d n alkanes of possible terrestrial origin and aquatic origin in lacustrine sediments is an indicator of hydroclimatic conditions for a lake environment e g terrestrial evapotranspiration of the lake drainage area or evaporation inflow ratio for the lake sachse d radke j gleixner g 2004 hydrogen isotope ratios of recent lacustrine sedimentary n alkanes record modern climate variability geochimica et cosmochimca acta 68 4877 4889 sachse d radke j gleixner g 2006 d values of individual n alkanes from terrestrial plants along a climatic gradient implications for the sedimentary biomarker record organic geochemistry 37 469 483 mugler i sachse d werner m xu b q wu g j yao t d gleixner g 2008 effect of lake evaporation on d values of lacustrine n alkanes a comparison of nam co tibetan plateau and holzmaar germany organic geochemistry 39 711 729 and this proposed indicator has been applied to a paleoclimatic study of koucha lake kcl on the northeastern tibetan plateau netp however the application was not very successful due to an apparent discrepancy between the reconstructed possible hydroclimatic variation based on the proposed indicator and precipitation amount variation based on pollen in the same lake aichner b herzschuh u wilkes h vieth a bohner j 2010a d values of n alkanes in tibetan lake sediments and aquatic macrophytes a surface sediment study and application to a 16 ka record from lake koucha organic geochemistry 41 779 790 we report new compound specific d n alkanes data for sediments since the last glacial from hurleg lake klk and genggahai lake ggh both also on the netp ca 300 km apart together d n alkanes data from the three lakes were analyzed to assess the difference between mid chain and long chain compound specific d n alkanes values in the sediments as a paleoclimatic indicator our results indicate that mid chain n c 23 and n c 25 and long chain n c 27 n c 29 and n c 31 n alkanes as compounds representative of aquatic and terrestrial origins respectively were valid only for klk correspondingly the use of differences between mid chain and long chain compound specific d n alkanes as a possible paleoclimatic indicator was feasible only for this lake hence our results emphasize the complex relationship between the chain length of lacustrine n alkanes and their actual origins and suggest that the correlation analysis of d n alkanes data for different chain length could be part of the possible evaluation method for the application of lacustrine compound specific d n alkanes data in paleoclimatic studies

paleomagnetism and age of three canadian rocky mountain diatremes paleomagnetic results and age estimates derived from them arc presented for three diatremes using as a basis of comparison the combined apparent polar wander apw path for north america and europe of van der voo the cross diatreme of the front ranges of the canadian rocky mountains has yielded a radiometric age of 241 ma earliest triassic and is hosted by the flat lying pennsylvanian tunnel mountain formation it has normal polarity magnetization and yields a paleopole correctly placed according to its radiometric age on the apw path the blackpool diatreme for which no radiometric age is available which is located in the main ranges of the rocky mountains is known to be post late ordovician because it is hosted by rocks of that age it also has magnetization of normal polarity and yields a paleopole that when calculated with respect to present horizontal is coincident with the latest cretaceous to paleocene paleopole for north america the paleopole when calculated with respect to bedding

stable carbon isotopic correlation of individual biolipids in aquatic organisms and a lake bottom sediment abstract isotope ratio monitoring gc ms irm gcms analyses of individual hydrocarbons isolated from the surface sediment of a small eutrophic lake priest pot u k and a phytoplankton tow sample from the upper water column have been undertaken in order to assign sources of sedimentary lipids the 13c values for the sedimentary n alkanes showed no clear distinction between lower molecular weight components c17 c19 of presumed algal origin and higher members c23 c33 of presumed higher plant origin thus indicating a limitation to the use of compound specific isotope analysis in the freshwater system studied in contrast the 13c values of sedimentary hopenes were markedly depleted by over 20 compared with those in the phytoplankton sample from the upper water column hop 22 29 ene in the surficial sediment had a 13c value of 55 2 which contrasts witht he value of the phytoplankton component 32 7 attributed to cyanobacteria these values indicate that a highly 13c depleted source provides a major contribution to the sedimentary component it is proposed that the sedimentary hopenes originate in part from methanotrophic bacteria demonstrating the presence of a bacterial methane cycle in this environment

paleoclimate reconstruction from petrography and biomarker geochemistry from permian humic coals in sydney coal basin australia abstract the character of the coal in tomago and greta coal measures are similar to other coals from the sydney coal basin with variation from vitrinite rich to inertinite rich coal a type iii organic matter om linked to continental higher plants and a perhydrous type iii similar to type ii were found by rock eval analysis the coexistence of inertinite with algae botryococcus in the greta coals explains the high hi in the perhydrous type the gangamopteris flora that is reported in the greta coal measures grew after plants in a taiga like the recent birch forests in russia retallack 1980 the glossopteris flora that is reported in the tomago coal measures grew in a swamp forest based upon the botanic zonation this flora was located in the cold temperate biome that was located in gondwanaland except for antarctica which was in the glacial biome diterpane analysis results reveal alternation of wet and dry periods existed during the deposition of lewis coals in the greta coal measures during the kungurian and an increase of dryness is noted from upper donaldson to beresfield in the tomago coal measures during the capitanian based on analysis of aromatics and diterpanes the same periods of dryness and wetness alternate during the coal deposition in the sydney coal basin these climatic changes correspond to high frequency cycles n alkanes naphtalenes and phenanthrenes and does not alter the paleoenvironmental and paleoclimatic interpretation the comparison between biomarkers from coals and isotopes from marine birgenheier et al 2010 and terrestrial retallack et al 2011 deposits allow us to identify precise dry wet climate and glacial interglacial periods during the permian

the significance of 24 norcholestanes 4 methylsteranes and dinosteranes in oils and source rocks from east sirte basin libya abstract the present paper involves a detailed evaluation of specific steroid biomarkers by gas chromatography mass spectrometry gc ms and gc metastable reaction monitoring mrm analyses of several crude oils and source rocks from the east sirte basin 24 norcholestanes dinosteranes 4 methyl 24 ethylcholestanes and triaromatic steroids have been identified in both source rocks and crude oils of the east sirte basin diatoms dinoflagellates including those potentially associated with corals and or their direct ancestors are amongst the proposed sources of these biomarkers these biomarker parameters have been used to establish a mesozoic oil source correlation of the east sirte basin hydropyrolysis of an extant coral extract revealed a similar distribution although immature of dinosteranes and 4 methyl 24 ethylcholestanes also observed in the sirte oils and source rocks this is consistent with the presence of dinoflagellates present during the deposition of the mesozoic aged east sirte basin formations a good data correlation for the rock extracts revealed a similar distribution of 3 24 dimethyl triaromatic steroids 3 methyl 24 ethylcholestanes 4 methyl 24 ethylcholestanes and 2 methyl 24 ethylcholestanes observed in one of the oil families and associated source rocks for the east sirte basin

chemical molecular and isotopic differentiation of organic facies in the tertiary lacustrine duaringa oil shale deposit queensland australia abstract total organic matter extractable organic matter bitumen and pyrolysates released on low temperature sealed tube pyrolysis of kerogen were analysed chemically and isotopically based on bulk bitumen and biomarker parameters the sediments are immature to a depth of approx 1300 m within the terrestrial and lacustrine depositional environments of the tertiary duaringa basin various organic facies have been classified according to inorganic input and maceral abundances of organic matter derived from land plant and algal sources the latter derived mainly from pediastrum and with a varying botryococcus content the lacustrine upper lamosite is chemically and isotopically distinct from the lower lamosite due to a changing algal community relative contributions from allochthonous land plants and for the lower lamosite a slightly more saline and restricted lake environment the lower lamosite is associated with the highest concentrations of c 28 c 30 4 methylsteranes and 13 c depletion in toc in the upper lamosite there is a strong positive correlation between botryococcus content and 13 c enrichment the organically lean claystones have sources nearly identical to the lamosites but the organic matter is diluted due to rapid influx of siliciclastics the terrestrial facies the cannel coal and carbonaceous shales are mainly distinguished from the lacustrine facies by higher relative proportions of c 29 steranes c 30 4 methylsteranes and 13 c values for the pyrolysed hydrocarbons intermediate between the two lamosite facies the carbonaceous oil shale has a composite geochemical signature intermediate between the two end members lamosite and cannel coal oleanane and ring a degraded triterpanes derived from lupane arborane and oleanane skeletons are distributed throughout all organic facies representing both autochthonous and allochthonous higher plant inputs higher concentrations of oleanane and des a lupane are associated with the terrestrial facies hopanes dominate over steranes in all organic facies and their concentration ranges are independent of facies for the lamosites the aliphatic biopolymer algaenan is implicated as the dominant source for n alkanes from analysis of their yields homologue abundances and individual 13 c values in the terrestrial facies resinites are paraffinic and are a major source for the n alkanes released on pyrolysis compound specific analysis of extractable and pyrolysate hydrocarbons allowed deconvolution of different source inputs to free lipids and kerogen for the lamosites low molecular weight n alkanes in the bitumen are derived mainly from a pediastrum source while botryococcus is associated with waxy n alkanes however the situation is reversed in the kerogen pediastrum algeanan has a longer average alkyl chain length than botryococcus algaenan the magnitude of the isotopic differences between single n alkanes released at different temperatures is useful in determining multiplicity of sources

novel families of tetra and hexacyclic aromatic hopanoids predominant in carbonate rocks and crude oils two novel families of monoaromatic geomarkers related to hopanoids have been separated and characterized in sediments and crude oils the benzohopanes c32 c35 1 and the ring d aromatized 8 14 secohopanoids c27 c35 4 and 5 both series are particularly abundant in many carbonate samples where they amount to approximately 100 p p m per component in some crude oils but can also be detected in other environments the benzohopanes have been separated as pure compounds by high performance liquid chromatography and identified by x ray diffraction the structure of the 8 14 secohopanoids mostly relies on spectroscopic data nmr and ms and comparison with synthetic analogs both families must be formed in the subsurface from bacterial c35 hopanoid precursors but the benzohopanes seem to occur at an earlier stage of sedimentation the two series appear in varying distributions in the different samples and may therefore be potentially useful as geochemical correlation parameters

distributions and stable carbon isotopic compositions of biomarkers in torbanites from different palaeogeographical locations abstract the relative distributions and stable carbon isotopic compositions of certain aliphatic and aromatic biomarkers from 11 botryococcus braunii rich torbanites from scotland south africa and australia covering the late carboniferous to late permian were investigated the data was scrutinised for any evidence of molecular features which may be characteristic of palaeogeography the torbanites studied were selected to cover a range of age and palaeoclimatic conditions e g permian and late carboniferous when gondwana was covered by an extensive ice sheet the late permian when the climate warmed from glacial to cool to temperate and the carboniferous when laurasia was located within the equatorial zone all torbanites are composed of abundant n alkanes and novel macrocyclic alkanes which based on similar 13c values are ascribed a common origin all samples are also characterised by a high cyanobacterial input as indicated by abundant hopanoids other biomarker distributions and stable carbon isotopic compositional differences separated the torbanites into three groups which also correlate to three different palaeogeographical palaeoclimatic precincts i group a southern africa and eastern australia temi torbanites which are characterised by a high relative abundance of cyanobacterial and methylotrophic hopanoids abundant branched hydrocarbons and 13c enriched homologous series of monomethylakanes ii group b eastern australia newnes and glen davis torbanites contain relatively high amounts of drimanes and abundant 13c enriched homologous series of monomethylakanes and iii group c scottish torbanites torbane hill and westfield contain high relative amounts of cyanobacterial hopanoids methylotrophic hopanoids and abundant branched aliphatics but no 13c enriched homologous series of monomethylakanes

δ13c of polycyclic aromatic hydrocarbons to establish the facies variations in a fluvial deltaic triassic record dampier sub basin western australia abstract the 13 c of polycyclic aromatic hydrocarbons pahs was measured in a series of triassic and jurassic source rocks from the dampier sub basin carnarvon basin north west shelf of australia these sequences correspond to fluvial deltaic systems which integrate the mungaroo brigadier and legendre formations and the organic matter has been assigned as mixed terrigenous marine material the relative abundance of the pahs was plotted against the difference between 13 c values of 1 3 6 7 tetramethylnaphthalene temn and each pah we demonstrated here that samples plotting below 0 for 13 c combustion marker 1 3 6 7 temn are related to delta plain front deltaic facies or coaly fluvial deltaic facies e g samples from the mungaroo formation north rankin 5 goodwyn 9 and goodwyn 5 wells whereas the positive region for 13 c combustion marker 1 3 6 7 temn is assigned to transitional facies deposited under an estuarine lagoonal environment with a high sapropelic contribution brigadier formation and marginal marine environment legendre formation a similar separation for the samples was obtained with phenanthrene and other pahs the 13 c of pahs in combination with their distributions can be used to establish the facies type i e delta plain front deltaic from estuarine lagoonal in a dominantly fluvial deltaic record our research provides new tools to take into account for further applications in fluid source rock correlation studies which represent the main challenge in assessing petroleum systems in the sub basin