depositional environments of late eocene lignite bearing strata east central texas late eocene lignites in the brazos river valley area occur in parasequence scale cycles containing mostly marine sediments lignite is present at the base of the marine interval and forms the base of the cycle in a majority of cases less frequently lignite is underlain by a thin interval of nonmarine deposits that form the base of the cycle in both situations the lignite is part of a thin transgressive interval cycles are separated by an exposure surface usually marked by plant rooting and or development of a paleosol in the top of the underlying sediments peat accumulated on top of these exposure surfaces and lignite is preserved where marine flooding allowed ocean waters to cover the peat deposits with fine grained sediments producing high ash lignite horizons of great lateral extent but variable thickness and quality this strandplain model of lignite occurrence provides a better understanding of late eocene lignites in texas than the deltaic or fluvial deltaic models previously used the strandplain model of lignite occurrence is appropriate for most of the yegua jackson lignites middle late eocene of texas and should be considered when evaluating depositional conditions of paleogene lignites in the northern gulf coast region a re evaluation of late eocene stratigraphy of the brazos valley area accompanies the documentation of depositional environments

vegetation distribution across the early eocene depositional landscape from palynological analysis abstract the usefulness of palynomorphs in reconstruction of vegetation in the pre quaternary has been hampered by uncertainty in distinguishing local from transported palynomorphs analysis of palynomorph transport in modern settings suggests that the importance of transported palynomorphs in a nonmarine depositional environment depends on its geomorphologic characteristics aerial transport will be a significant source of palynomorphs only if the environment is open waterborne transport depends on the access of water to the depositional environment the importance of transported palynomorphs relative to the local palynomorphs varies among depositional environments and can be assessed in each case in the early eocene of the bighorn basin wyoming five depositional environments pond levee crevasse splay swamp margin swamp reduced floodplain contain distinct palynomorph assemblages as measured by canonical variates analysis the relative importance of transported palynomorphs is greatest in the pond and progressively decreases in the levee reduced floodplain swamp margin and swamp in the pond reworked marine dinoflagellates and bisaccate conifer pollen are high in abundance reflecting transport taxodiaceae and alnus are rare and did not inhabit the vegetation surrounding the pond corylus ulmaceous and fagaceous taxa lived surrounding the pond the levee like the pond contains marine dinoflagellates and bisaccate pollen but in lower numbers than the pond pollen of fagaceae alnus locally and pteridophyte spores reflect the levee vegetation the abundance of pteridophyte spores results from their ability to respond quickly to substrate disturbance reduced floodplains contain pteridophytes taxodiaceae platycarya and plicatopollis swamp margin and swamp palynofloras are similar and are dominated by local plants taxodiaceae alnus platycarya sparganiaceaepollenites and locally pistillipollenites the palynofloral data is consistent with the megafloral record in the same environments this supports the vegetation reconstruction from palynology

ambient vibration analysis of an unstable mountain slope summary a field experiment with small aperture seismic arrays was performed on the unstable rock slope above the village of randa in the southern swiss alps the aim of this experiment was to constrain the seismic response of a potential future rockslide using ambient vibration recordings weak seismic events were identified on the recordings and site to reference spectral ratios were calculated using a reference site located on the stable part of the slope spectral ratios of up to 30 were observed at sites located within the unstable portion of the slope a strong variation of spectral ratios with azimuth indicates a directional site effect neither amplification nor directionality were observed at sites located in the stable part of the slope furthermore time frequency polarization analysis of the ambient noise was performed to provide robust estimates of frequency dependent directions of the maximum polarization it was found that the unstable part of the slope vibrates within a narrow range of directions 130 10 for the frequency range centred around 5 hz the polarization directions estimated from ambient seismic vibrations are in good agreement with the deformation directions obtained by geodetic and in situ measurements no directionality of ambient vibrations was observed at sites within the stable part of the slope

organic geochemical investigations of brown coal lithotypes a contribution to facies analysis of seam banding in the helmstedt deposit abstract samples of light medium light and dark lithotypes from the eocene helmstedt brown coal deposit were examined by organic geochemical methods soxhlet extraction liquid and gas chromatography gc ms the study is part of a facies analysis of banded brown coals there are significant differences between the lithotypes concerning the extractable organic matter yields the composition of the extracts and the composition of the alkane fractions on average the light brown coals produce three times as much extractable organic matter as the dark ones asphaltenes and resins are the main components of the extracts of the light lithotypes hydrocarbons and n s o compounds of lower molecular weight are less abundant than in the dark lithotypes the alkane fraction of light lithotypes contains more n alkanes of high molecular weight and more saturated triterpenoids hopanes excluding homohopane but less unsaturated polycyclic compounds rearranged sterenes triterpenes and less homohopane the generally low concentrations of cyclic diterpanes norabietane norpimarane do not reveal any relationship to the three lithotypes based on these results there is no support for the conventional assumption that the light and dark brown coal lithotypes originated from different plant communities of the paleomoor the results rather suggest that the banding within the seam of the helmstedt brown coal deposit results from different biogeochemical degradation and transformation processes these processes are considered to be dependent on the environment of the paleomoor

effects of geometry on the seismic wavefield of alpine glaciers passive seismology allows measurement of the structure of glaciers and ice sheets however most techniques used so far in this context are based on horizontally homogeneous media where parameters vary only with depth 1 d approximations which are appropriate only for a subset of glaciers here we analyze seismic noise records from three different types of glaciers plateau valley and avalanching glacier to characterize the influence of the glacier geometry on the seismic wavefield using horizontal to vertical spectral ratios polarization analysis and modal analysis we show that the plateau glacier and the valley glacier can be seen as 1 d whereas the relatively small avalanching glacier shows 3 d effects due to its bed topography and the deep crevasses in principle the techniques proposed here might allow monitoring such crevasses and their depth and thus to constrain a key parameter of avalanching and calving glacier fronts

oceanographic control of diatom abundances and species distributions in surface sediments of the tropical and southeast atlantic abstract this paper is a descriptive account of the diatomaceous component of pelagic sediments from the tropical and southeast atlantic ocean geographic patterns of diatom abundances whole and fragment forms per gram major species relative abundances and diatom assemblages resolved by q mode factor analysis are presented comparisons drawn to sea surface temperature salinity and productivity distributions suggest that i diatom abundances primarily reflect surface productivity with no apparent dissolution effects due to water depth ii relative abundances of major species vary in their ecologic dependence but do reflect major oceanographic features of the surface waters and iii of the five diatom assemblages resolved four finely delineate the complexity of the low latitude oceanography these assemblages in decreasing order of statistical importance are associated with 1 warm waters of moderate to high primary productivity 2 the oceanward margin of the benguela current a region of high primary production with a maximum in austral summer 3 low salinity waters off the mouths of the zaire and niger rivers and 4 subtropical to tropical waters of lower productivity mostly in the western equatorial atlantic the fifth factor represents the equatorward advection of subantarctic to antarctic diatoms by deep ocean currents

ambient vibration classification of unstable rock slopes a systematic approach abstract in this paper we are comparing the seismic response of 25 different rock slope instabilities with diverse geological properties activity level failure mechanism fracturing and volumes we classify them according to their dynamic behaviour in the dataset we found two main classes of unstable rock slopes depth controlled sites and volume controlled sites for depth controlled instabilities the seismic wavefield is controlled by horizontally propagating surface waves in the highly fractured and weathered material at such sites surface wave dispersion curves can be retrieved and inverted into velocity profiles of the underground the lateral borders of depth controlled instabilities are not obvious and the seismic properties mainly change with depth the seismic response of volume controlled sites is dominated by the eigenvibrations of the rock mass itself such instabilities have clear lateral and vertical borders and show highly amplified ground motion in limited frequency bands the observed polarisation of the ground motion is perpendicular to deep open fractures that do not allow surface waves to propagate a special case of the volume controlled sites is represented by tower like rock masses showing strong amplification and directionality their dynamic behaviour might not only be related to the internal structure but also to their geometry that is similar to high rise buildings another type of rock instabilities is represented by block structures which are difficult to identify by the proposed ambient vibration methods a clear relation between geological properties and seismic response was not found

ambient seismic vibrations in steep bedrock permafrost used to infer variations of ice fill in fractures abstract the behavior of ice in frozen rock masses is an important control on rock slope stability but the knowledge of the formation extent and evolution of ice filled fractures in steep bedrock permafrost is limited therefore this study aims at characterizing the site specific ambient seismic vibration recorded at the matterhorn hornligrat fieldsite over the course of more than three years the observed normal mode resonance frequencies vary seasonally with four distinct phases persistent decrease during summer phase i rapid increase during freezing phase ii trough shaped pattern in winter phase iii and a sharp peak with a rapid decay during the melting thawing season phase iv the relation between resonance frequency and rock temperature exhibits an annually repeated pattern with hysteretic behavior the link between resonance frequency fracture width and rock temperature indicates that irreversible fracture displacement is dominant in summer periods with low resonance frequency these findings suggest that the temporal variations in resonance frequencies are linked to the formation and melt of ice fill in bedrock fractures

on the fundamental difference between coal rank and coal type abstract this article addresses the fundamental difference between coal rank and coal type while theoretically settled long ago as being different aspects of coal systems science the two concepts are still often confounded in recent years this has resulted in the publication of several works stating that coal type changes with coal rank coal type refers solely to coals depositional origin and the maceral mineral admixture resulting from that origin coal types typically fall in to two categories humic coals developed from peat and sapropelic coals developed from organic mud either type may be allocthonous or autochthonous and within types further refinement of depositional environment can be made coal rank refers to the changes in geochemistry and resultant changes in reflectance caused by increasing thermal maturity of the coal thus it provides an overprint of maturity on existing coal types with proper techniques such as use of crossed polars and etching maceral forms can be differentiated even at high ranks and the original coal type determined

a 20 year varve record of siliceous phytoplankton variability in the central gulf of california abstract year to year variability in the structure of the preserved siliceous phytoplankton assemblage is reconstructed from a box core retrieved from the varved sediments along the guaymas slope of the gulf of california a 20 year record from 1953 through 1972 is obtained from interpretation of the varve stratigraphy supported by 210 pb and 228 th dating ecological time series derived from microfossil analysis show a strong coherence with interannual sea level anomalies indicating a response to large scale climatic variability associated with the el nino southern oscillation phenomenon el nino periods are generally marked by increases in preserved abundances of the total siliceous assemblage and in particular by greater numbers of individuals within species whose distribution is limited to tropical and subtropical waters

the central myanmar burma oil family composition and implications for source abstract geochemical characteristics of 31 miocene through eocene oils seeps an eocene coal and an eocene resin from the central myanmar burma basin system are examined the oils seeps vary widely in api gravity 8 52 sulfur concentration 26 3550 ppm 13 c 27 6 to 23 4 and molecular composition this variability is caused by varying amounts of biodegradation superimposed upon a single genetic oil family and the difference between aliphatic and aromatic hydrocarbon carbon isotope ratios i e 13 c arom 13 c aliph provides a useful gauge of the extent of biodegradation the projected geochemical characteristics of unaltered central myanmar oils are as follows a api gravity 35 37 b s 0 05 0 10 c 13 c aliph 27 8 to 27 6 d 24 ethylcholestanes are the dominant steranes and e 20s 24 ethyldiacholestane various bicadinanes and oleanane are present the ratio of 18 h 22 29 30 trisnorneohopane to 17 h 22 29 30 trisnorhopane t s t m is postulated as a maturity parameter and on this basis relative bicadinane concentration increases and the trans trans trans cis cis trans bicadinane ratio decreases with increasing thermal maturity in this oil set geologic arguments suggest a deep paleogene source for these oils two geochemical arguments that support this inference are a the occurrence of saturated and unsaturated c 15 and c 30 cadinane monomers and dimers in pyrolyzates of an eocene resin and the kerogen from an eocene coal and b identical compound specific carbon isotope ratios for selected isoprenoids and n alkanes in a typical central myanmar oil and the hydrous pyrolyzate expelled from an eocene coal we propose an eocene resinous shale coal source for these oils with the oldest eocene reservoirs filling first and the youngest miocene reservoirs filling last consistent with the observation that the least mature oils are present in the oldest reservoirs according to this model surface seepage and near surface oil could result from subsurface traps that are filled to spillpoint

hopane derived triterpenoids in soils the occurrence distribution and degradation pathways of hopanoid triterpenes have been studied in thirteen soil samples with varying degrees of biological activity hopanoids were shown to occur in all samples suggesting that they are not only ubiquitous in subaquatic sediments but also in soils hop 22 29 ene was generally predominant in the hydrocarbons whereas the 17 h 21 h bishomohopanoic acid c32 was the major component in the acids the concentrations of hopanes were usually rather low except in acidic peat the distribution in carbon number of hopanes and hopanoic acids showed great similarities with those of moderately oxic subaquatic sediments intact bacteriohopane tetrol widespread in microorganisms and the main precursor of geohopanoids was identified in substantial amounts in a peat exposed to groundwater oscillations

palynology and paleoecology of lignites from the manning formation jackson group outcrop in the lake somerville spillway of east central texas abstract four palynomorph assemblages whose parent plants contributed to the formation of the lignite occur in the lignite seams and associated sediments from the manning formation jackson group outcrop in the lake somerville spillway of texas the cicatricosisporites laevigatosporites fern assemblage occurs in the middle and upper seam and probably derived from a freshwater herbaceous mire community the momipites coryloides arecipites columellus liliacidites assemblage occurs in all three seams and probably derived from a freshwater mire forest with an open canopy or shrub community the momipites coryloides nyssa rhoipites angustus assemblage occurs in the lower and middle seams and probably derived from a different freshwater mire forest the cupuliferoipollenites cupuliferoidaepollenites liblarensis siltaria cf s scabriextima assemblage occurs at the top of the lower and middle seams which are overlain by marine sediments the association between cupuliferoipollenites dominance and the presence of marine diatoms and brackish or marine trace fossils in the lignite suggests that this assemblage may have derived from a mangrove i e marine or brackish mire forest however other factors may influence its distribution ailanthipites berryi possibly derived from a tree or shrub related to the tree of heaven predominates in the claystone underlying the lower lignite seam and may have colonized the coastal plain prior to the initiation of peat accumulation we can differentiate lignite samples dominated by fern spores momipites pollen and cupuliferoipollenites pollen based on gas chromatography mass spectrometry gc ms fragmentograms of triterpanes m z 191 and steranes m z 217 the lignite layers dominated by each palynomorph assemblage appear to have distinct sources and different early diagenetic pre coalification histories

anthropogenic sources stimulate resonance of a natural rock bridge the natural modes of vibration of bedrock landforms as well as the sources and effects of stimulated resonance remain poorly understood here we show that seismic energy created by an induced earthquake and an artificial reservoir has spectral content coincident with the natural modes of vibration of a prominent rock bridge we measured the resonant frequencies of rainbow bridge utah using data from two broadband seismometers placed on the span and identified eight distinct vibrational modes between 1 and 6 hz a distant induced earthquake produced local ground motion rich in 1 hz energy stimulating a 20 db increase in measured power at the bridge s fundamental mode moreover we establish that wave action on lake powell an artificial reservoir generates microseismic energy with peak power 1 hz also exciting resonance of rainbow bridge these anthropogenic sources represent relatively new energy input for the bridge with unknown consequences for structural fatigue

ambient resonance of mesa arch canyonlands national park utah we analyzed the resonance characteristics of a prominent natural arch in canyonlands national park mesa arch as measured from ambient seismic data evaluating spectral and polarization attributes we distinguished the first four resonant frequencies of the arch 2 9 6 0 6 9 and 8 5 hz as well as basic properties of the associated mode shapes we then affirmed experimental data using 3 d numerical modal analysis providing estimates of material properties and clarifying vibrational mode shapes monitoring resonant frequencies over time we searched for shifts associated with changing environmental conditions and long term progressive damage we measured 3 direct daily variation in resonant frequency associated with changing rock temperature thermal stress and stiffening of the rock matrix independent tilt data showed similar diurnal cycles associated with thermoelastic stresses and deformation of the arch we observed no permanent resonant frequency shifts related to irreversible damage of mesa arch during our study period

dynamic response of the chamousset rock column western alps france 1 this paper investigates the variation of the first resonance frequency of the chamousset limestone column 21 000 m3 vercors french alps before its collapse in november 2007 the site was instrumented with seismometers and extensometers during a 4 month period with some gaps in the measurements experimental results and numerical modeling showed that the resonance frequency of a prone to fall column can be derived from the spectra of continuous seismic noise records at the chamousset site the evolution of the resonance frequency appeared to be strongly controlled by the temperature when temperatures were positive slight resonance frequency variations correlated well with thermal fluctuations irreversible damage can occur during freeze thaw cycles and to a lesser extent during strong wind it coincided with a significant drop in resonance frequency which was interpreted as the result of rock bridge breakage this hypothesis is supported by fresh rupture observations after the collapse seismic event records and numerical modeling this study suggests that seismic noise recording could be used for assessing the potential failure of unstable columns in rigid rocks

a displaced neritic diatom delphineis karstenii in pelagic sediments of the southeast atlantic this paper documents the occurrence ofdelphineis karstenii a neritic diatom in pelagic sediments of the northern cape and southern angola basins southeast atlantic ocean maximum abundances are found in the southern angola basin although the source area appears to be the diatomaceous sediments which blanket much of the namibian continental shelf the observed pattern implies large scale displacement ofd karstenii valves first northward along the continental margin and then westward into deep waters transport evidently occurs in the surface waters of the benguela current which flow northward along the namibian coast and then turn westward away from the coast of angola and out into the angola basin these observations suggest thatdelphineis valves and perhaps other shallow water diatom valves may be displaced downslope on other continental margins failure to recognize such displacement could lead to incorrect ecological and paleoecological interpretations

aromatic hydrocarbons in the paraiba valley oil shale abstract aromatic hydrocarbon fractions extracted from different depths of a core 13 8 47 3 m deep of the paraiba valley oil shale were analysed by computerized high resolution gas chromatography mass spectrometry triterpenes derived from precursors oxygenated at position 3 such as tetracyclic ring a degraded and pentacyclic aromatic ursane oleanane and lupane derivatives were amongst the most common components indicating an important input from higher plants to the sediment this interpretation is supported by the occurrence of sesquiterpenoids cadalene calamenene in the same sediment samples on the other hand hopanoids notably the tetraaromatic derivative were also detected attesting to a significant bacterial contribution to the sedimentary biomass in contrast with the abundance of aromatic structures related to oleanane ursane and hopane no skeletons traceable to steroidal precursors could be confirmed suggesting a small algal input this study also revealed the presence of two new aromatic biomarkers one of them is a c24 monoaromatic tetracycle apparently derived via ring a degradation from a triterpenoid with the fernene skeleton the other compound is a ring a monoaromatic pentacycle with what appears to be a hopanoid structure

variability of holocene diatom assemblages in laminated sediments near walvis bay southwest africa abstract silica rich muds along the southwest african coast contain a mixture of neritic and oceanic diatoms lighter colored laminae contain a higher percentage of neritic forms and reflect strong upwelling and augmented primary productivity in contrast darker laminae indicate reduced upwelling and incursion of lower nutrient offshore waters the ratio of delphineis karstenii to the thalassiosira eccentrica group is generally higher in lighter colored laminae and thus appears to increase with increasing primary productivity the laminae are probably varves with lighter laminae forming during austral spring and summer when upwelling is most frequent and most intense and darker laminae forming in the winter months the diatomaceous muds appear to contain a detailed record of climatic change during the late holocene

production preservation and prediction of source rock facies in deltaic settings abstract this article hypothesizes that production and preservation of source rock type facies in deltaic systems both landward and seaward of a coastline is mutually exclusive time successive and related to the dynamics of relative sea level sedimentologic research in the holocene mississippi and rhone delta complexes suggests that rheotrophic peats and associated organic rich beds preferably accumulate in the accommodation space created behind landward stepping shorelines in a transgressive systems tract tst such a setting also allows for a sufficient supply of recharging fresh nutrient rich groundwater into the peat forming mires kosters e c suter j r 1993 facies relationships and systems tracts in the late holocene mississippi delta plain journal of sedimentary petrology 63 4 727 733 independently carried out quantitative paleoecological studies in the same delta systems and in addition in the orinoco and po deltas suggest that in a progradational setting highstand systems tract hst seasonally discharged nutrient and sediment laden river waters on the shelf may give rise to anoxia or dysoxia subsequent overfertilization of the shelf leads to accumulation of organic rich mud belts on the shelf vanderzwaan g j jorissen f j 1991 biofacial patterns in river induced anoxia in tyson r v pearson t h eds modern and ancient continental shelf anoxia geological society of london special publication no 58 pp 65 82 thus production and preservation of source rock type facies landward of a shoreline as peats and related sediments is preferred in a tst when accommodation space and nutrient supply are landward of the shoreline vice versa production and preservation of such facies seaward of a shoreline as organic rich shelf muds occurs preferentially in a highstand systems tract in that situation accommodation space is on the shelf where river fed nutrients are supplied as well this hypothesis suggests further potential for application of sequence stratigraphic concepts for improved understanding of the occurrence of source rock type facies

diatom taphocoenoses in the coastal upwelling area off south west africa abstract the diatom floral composition of 124 sediment samples from the south east atlantic records the influence of coastal upwelling on sediment composition off south west africa inner shelf samples between 19 and 24 s are rich in diatom valves and the patterns of diatom species distribution in these samples are related to the coastal upwelling process comparison with recent phytoplankton data shows that the sediment assemblages preserve many of the important species of the diatom biocoenoses including chaetoceros resting spores delphineis karstenii thalassiosira eccentrica and thalassionema nitzschioides delphineis karstenii a pioneer species in enriched coastal water occurs nearshore and chaetoreros resting spores are widespread with highest relative abundance values in some more offshore samples the abundance of the thalassiosira eccentrica group and of thalassionema nitzschioides in sediment samples in and near walvis bay reflects the recurrence of intense upwelling off this part of the coast an abundance of large centric species has been reported in hydrological conditions characteristic of newly upwelled waters and correspondingly actinocyclus octonarius and some large coscinodiscus species occur in the sediments in nearshore patches or belts

varves in marine sediments a review the global compilation of reported marine varved sedimentary records throughout the quaternary contains 52 sites marine varve deposition and preservation typically depend on environmental and sedimentological conditions such as a sufficiently high sedimentation rate severe depletion of dissolved oxygen in bottom water to exclude bioturbation by macrobenthos and a seasonally varying sedimentary input to yield a recognizable rhythmic varve pattern additional oceanographic factors include the strength and depth range of the oxygen minimum zone omz and regional anthropogenic eutrophication from point sources such as large polluted rivers quaternary marine varves are not only found in those parts of the open ocean that comply with these conditions but also in fjords embayments and estuaries with thermohaline density stratification and nearshore marine lakes with strong hydrologic connections to ocean water this review critically describes settings and sedimentological characteristics of marine sites where varves have been reported broader applications of marine varve records are discussed for example in terms of radiocarbon calibration on high resolution time scales constraining paleoceanographic variability and global change teleconnections diagnosing factors affecting modern fish population dynamics based on past performance detailing biogeochemical cycles and deciphering complex factors influencing marine productivity varves in saline water bodies without hydrologic connection to the global ocean are not included in this review and instead pertain to the companion review on lacustrine varves where also general and fundamental principles of varve deposition classification and dating are covered zolitschka et al 2015 the postulated occurrence of varves in pre quaternary rocks is critically discussed in this review with representative examples in the case of non evaporitic laminations in fine grained ancient marine rocks such as banded iron formations and black shales laminations may not be varves but instead may have multiple alternative origins such as event beds or formation via bottom currents that transport and sort silt sized particles clay floccules and organic mineral aggregates in the form of migrating bedload ripples

aliphatic and aromatic triterpenoid hydrocarbons in a tertiary angiospermous lignite abstract the hydrocarbon biomarker assemlage of a liptinite rich early tertiary angiospermous lignite has been characterized the biomarker fistribution for the lignite confirms the low maturity and previous paleobotanic interpretations the aliphatic hydrocarbon fraction consists predominantly of n alkanes showing a strong odd carbon predominance and numerous de a triterpenoids and triterpenoids derived from higher plants bacterially derived triterpenoids were represented primarily by homohopanes and hopenes the aromatic hydrocarbon fraction contains a series of mono di and triaromatic de a triterpenoids and mono tri and tetraaromatic triterpenoids derived from higher plants the concentration and abundance of monoaromatic triterpenoids containing one to three additonal degress of unsaturation have not seen previously observed in a single deposit as such a diagenetic scheme for angiosperm derived triterpenoids is presented which confirms and extends previous hypothesis

modal and thermal analysis of les arches unstable rock column vercors massif french alps a potentially unstable limestone column 1000 m3 vercors french alps delineated by an open rear fracture was continuously instrumented with two three component seismic sensors from mid may 2009 to mid october 2011 spectral analysis of seismic noise allowed several resonance frequencies to be determined ranging from 6 to 21 hz the frequency domain decomposition fdd technique was applied to the ambient vibrations recorded on the top of the rock column three vibration modes were identified at 6 7 5 and 9 hz describing the upper part of corresponding modal shapes finite element numerical modelling of the column dynamic response confirmed that the first two modes are bending modes perpendicular and parallel to the fracture respectively while the third one corresponds to torsion seismic noise monitoring also pointed out that resonance frequencies fluctuate with time under thermomechanical control for seasonal cycles changes in frequency are due to the variations of the bulk elastic properties with temperature at daily scale increase in fundamental frequency with temperature has been interpreted as resulting from the rock expansion inducing a closure of the rear fracture rock bridges hence stiffening the contact between the column and the rock mass conversely the rock contraction induces a fracture opening and a decrease in resonance frequency in winter when the temperature drops below 0 c a dramatic increase in fundamental frequency is observed from 6 hz to more than 25 hz resulting from ice formation in the fracture during spring the resonance frequency gradually diminishes with ice melting to reach the value measured before winter

coal and coal macerals as source rocks for oil and gas abstract the role of coals in the generation and migration of hydrocarbons is discussed from the viewpoints of chemistry and petrology extract data and considerations of volatile matter and maturity suggests that under geochemical conditions most coals can give rise to oil as well as gas a distinction is drawn between release of absorbed oil and formation of hydrocarbons by thermal breakdown of the coal matrix itself the generation and preservation of oil require not only that suitable lipidic structures be present but that the product oil can escape before being cracked to gas exinite preferably in large discrete particles is the most oil prone maceral vitrinite can form oil but subsequent migration depends on the availability of cracks and fissures in the coal matrix the most highly reflecting forms of inertinite e g fusinite have no inherent capacity to generate oil low reflectance inertinite such as is common in many australian coals may have minor source potential a speculative attempt is made to quantify the oil generating capacity of coal macerals and mixtures as a general broad rule on a weight basis exinite can produce ten times more oil than vitrinite and a hundred times more than inertinite approximate calculations suggest that thermal maturation of coals can account for all the known oil and gas reserves in the gippsland and cooper basins of australia even if only 1 of generated hydrocarbons is trapped

the impact of hydroclimate and dam construction on terrigenous detrital sediment composition in a 250 year santa barbara basin record off southern california abstract the recurrence and magnitude of southern california hydroclimate extremes are poorly resolved due to the relatively short duration

organic geochemistry and petrography of tertiary coals and carbonaceous shales from argentina a series of eight tertiary coal and carbonaceous shale samples with vitrinite reflectance values between 0 50 and 0 58 were extracted fractionated and the saturated and aromatic hydrocarbons analysed for characteristic components by gc and gc ms additionally a microscopical study was undertaken in order to obtain a more precise picture of the samples under investigation the saturated hydrocarbon fractions displayed the typical n alkane distribution for coals of this rank with cpi values between 2 0 and 3 1 among the branched cyclic compounds pristane and homohopane were recognised as relevant components pointing to an oxic depositional environment detection of benzohopanes c32 c35 in the aromatic hydrocarbon fractions suggests that bacteriohopanetetrol was a significant constituent of the coal biomass taking into consideration the pr ph ratios ash contents and microscopical characteristics of the samples aspects of the possible degradation of hopanetetrol to homohopane are discussed resin derived diterpenoids with the phyllocladane and kaurane skeleton were tentatively identified and although minor compounds they are interpreted to be a sign of the contribution of podocarpaceae and araucareaceae to the coal swamp aromatic compounds were dominated by alkylnaphthalene derivatives presumably formed by c ring cleavage and aromatisation of higher plant derived pentacyclic triterpenois which were main components in the high boiling range of the fractions investigated angiosperms especially fagaceae are postulated as source for these polycyclic compounds and hence for some of the polyalkylated aromatic bicyclics detected

molecular indicators of diagenesis in lignite diastereomeric configuration of triterpenoid derived aromatic hydrocarbons abstract the ratio of tetramethyloctahydropicene diastereomers i and ii is shown to vary as a function of a depth b lithotype and c seam in a 100 m core of continuous coal taken from the latrobe valley victoria this is the first illustration that triterpenoid derived aromatic hydrocarbon diastereomers can be used as molecular indicators of diagenesis

biogenic and abiogenic components of laminated hemipelagic sediments in the central gulf of california abstract alternating light and dark submillimeter to millimeter thick layered sediments rhythmites are found along the slopes of the central and southern gulf of california where a strong oxygen minimum zone intersects the sediment water interface two short intervals of distinct alternations were sampled lamina by lamina from two cores in the central gulf both cores are from the slope of the guaymas basin one core is from the mainland side the other core is from the baja side each lamina sample was analyzed for its opal micro floral assemblage textural character trace metal and bulk chemical cu mn fe ni zn ca k al sio2 and c org content and mineralogy on both sides of the gulf the light laminae contain more diatom frustules up to 90 and less terrigenous and organic material than the dark laminae the sediment is predominantly silt sized the dark laminae contain more terrigenous material which is primarily clay size on both sides of the gulf the light laminae apparently represent sedimentation during the dry winter season of northwesterly winds whereas the dark laminae represent the wet summer season of southeasterly winds