monoterpenylabietenoids novel biomarkers from extant and fossil taxodioideae and sedimentary rocks abstract the presence of 7 p cymenylferruginol and its diagenetic biomarkers occurring in cenozoic fossil plants and mesozoic siltstones and coals has been studied using gas chromatography mass spectrometry both 7 and 7 p cymenylferruginol isomers were the dominant natural products with two novel minor additional isomers namely 3 and 3 p cymenylferruginol and two hydrocarbons 7 and 7 p cymenyldehydroabietane the other tentatively assigned aromatic hydrocarbons were 9 10 p cymenylretene and 9 p cymenylsimonellite which were present in upper cretaceous and lower jurassic sedimentary rocks with their further dehydrogenation products diterpenoid dimers were also tentatively identified in trace amounts with 11 and 14 ferruginylferruginol as the dominant compounds our results show that the p cymenylferruginols and p cymenyldehydroabietanes are not thermally stable and that their occurrence in sedimentary rocks is controlled by the maturity of the organic matter om also chamaecydin identified for the first time in pre paleogene strata was not detectable when the om maturity based on vitrinite reflectance was higher than 0 45 0 5 rr

heat flow strong near fault seismic waves and near fault tectonics on the central san andreas fault the main san andreas fault strikes subparallel to compressional folds and thrust faults its fault normal traction is on average a factor of 1 2 thr 1 thr2 thr where thr is the coefficient of friction for thrust faults times the effective lithostatic pressure a useful upper limit for thr of 0 6 where is 3 12 is obtained from the lack of heat flow anomalies by considering off fault convergence at a rate of 1 mm yr for 10 km across strike if the fault normal traction is in fact this high the well known heat flow constraint of average stresses of 10 20 mpa during strike slip on the main fault becomes more severe only a few percent of the total slip during earthquakes can occur at the peak stress before dynamic mechanisms weaken the fault the spatial dimension of the high stress rupture tip zone is 10 m for 3 12 and for comparison 100 m for 1 high dynamic stresses during shaking occur within these distances of the fault plane in terms of scalars fine scale tectonic stresses cannot exceed the difference between failure stress and dynamic stress plate scale slip causes stresses to build up near geometrical irregularities of the fault plane strong dynamic stresses near the rupture tip facilitate anelastic deformation with the net effects of relaxing the local deviatoric tectonic stress and accommodating deformation around the irregularities there also is a mild tendency for near fault material to extrude upward slip on minor thrust faults causes the normal traction on the main fault to be spatially variable

effects of slip slip rate and shear heating on the friction of granite the stability of fault slip is sensitive to the way in which frictional strength responds to changes in slip rate and in particular to the effective velocity dependence of steady state friction ss ln v this quantity can vary substantially with displacement temperature and slip rate to investigate the physical basis for this behavior and the possible influence of shear heating we slid initially bare granite surfaces in unconfined rotary shear to displacements of hundreds of millimeters at normal stresses n of 10 and 25 mpa and at room temperature we imposed step changes in slip rate within the range 10 2 to 103 5 m s and also monitored frictional heating with thermistors embedded in the granite the transient response of to slip rate steps was fit to a rate and state dependent friction law using two state variables to estimate the values of several parameters in the constitutive law the first 20 mm of slip shows rising friction and falling ss ln v further slip shows roughly constant friction ss ln v and parameter values suggesting that a steady state condition is reached on the fault surface at v 10 m s ss ln v 0 004 0 001 at higher rates the response is sensitive to normal stress at n 25 mpa granite shows a transition to effective velocity strengthening ss ln v 0 008 0 004 at the highest slip rates tested at 10 mpa granite shows a less dramatic change to ss ln v 0 at the highest rates the maximum temperature measured in the granite is 60 c at 25 mpa and 103 5 m s temperatures are in general agreement with a numerical model of heat conduction which assumes spatially homogeneous frictional heating over the sliding surface the simplest interpretation of our measurements of ss ln v is that the granite is inherently velocity weakening ss ln v 0 mimics velocity strengthening these results have implications for the frictional behavior of faults during earthquakes high slip rates may cause a switch to effective velocity strengthening which could limit peak coseismic slip rate and stress drop for fluid saturated faults strengthening by this mechanism may be partly or fully offset by weakening due to thermal pressurization of a poorly drained pore fluid

molecular composition and chemosystematic aspects of cretaceous amber from the amazonas araripe and reconcavo basins brazil amber occurrences in brazil are rare in this regard the molecular composition of three such fossil resin samples from brazilian cretaceous sedimentary basins has been analyzed to determine the botanical origin of the resins the samples were collected from the amazonas alter do chao formation araripe santana formation crato member and reconcavo maracangalha formation caruacu member basins the mono sesqui and diterpenoids in the extracts were used as chemosystematic markers when compared with terpenoids in extant conifers the compounds were mainly diterpenoids and their degradation products from the labdane podocarpane pimarane and isopimarane classes in addition to paraffins methoxyphenols and carboxylic acids tetracyclic diterpenoids such as phyllocladane kaurenol and kauranol were also present the biomarker compositions are certainly typical for conifers and given the absence of triterpenoids and diterpenoids such as ozic acid angiosperms can be excluded as a botanical source the absence of phenolic diterpenoids ferruginol totarol and their derivatives excludes podocarpaceous affinities for the ambers from the amazonas and araripe basins the fossil records of the embedding sediments e g araucariaceae pollen and leaves support the proposal of an araucariacae origin for these ambers but cupressaceae and cheirolepidiaceae cannot be excluded on the other hand the presence of phyllocladane and kaurane derivatives is evidence for araucariaceae or podocarpaceae origins for the amber from the reconcavo basin but cupressaceae cannot be excluded

scaling of the critical slip distance for seismic faulting with shear strain in fault zones theoretical and experimentally based laws for seismic faulting contain a critical slip distance1 5 dc which is the slip over which strength breaks down during earthquake nucleation on an earthquake generating fault this distance plays a key role in determining the rupture nucleation dimension6 the amount of premonitory and post seismic slip7 10 and the maximum seismic ground acceleration1 11 in laboratory friction experiments d c has been related to the size of surface contact junctions2 5 12 thus the discrepancy between laboratory measurements of dc 10 5m and values obtained from modelling earthquakes 10 2m has been attributed to differences in roughness between laboratory surfaces and natural faults5 this interpretation predicts a dependence of dc on the particle size of fault gouge2 breccia and wear material but not on shear strain here we present experimental results showing that dc scales with shear strain in simulated fault gouge our data suggest a new physical interpretation for the critical slip distance in which dc is controlled by the thickness of the zone of localized shear strain as gouge zones of mature faults are commonly 102 103 m thick12 17 whereas laboratory gouge layers are 1 10 mm thick our data offer an alternative interpretation of the discrepancy between laboratory and field based estimates of dc

burial of organic carbon and pyrite sulfur in sediments over phanerozoic time a new theory in present day marine sediments almost all of which are deposited in normal oxygenated seawater rates of burial of organic carbon c and pyrite sulfur s correlate positively and bear a constant ratio to one another c s 3 on a weight basis by contrast calculations based on the isotopic model of garrels and lerman 1981 indicate that at various times during the phanerozoic the worldwide burial ratio must have been considerably different than the present day value this ratio change is caused by the requirement that increases in the worldwide mass of organic carbon must be accompanied by equivalent decreases in the mass of sedimentary pyrite sulfur in order to maintain a roughly constant level of o2 in the atmosphere such apparently contradictory behavior can be explained if the locus of major organic carbon burial has shifted over time from normal marine environments as at present to non marine freshwater or to euxinic environments in the geologic past a shift to predominantly freshwater burial can help explain predicted high c s ratios in permo carboniferous sediments and a shift to euxinic environments can help explain predicted low c s ratios during the early paleozoic it is demonstrated that the three environments today exhibit distinguishably different average c s ratios

an empirical study of the distribution of earthquakes with respect to rock type and depth whether fault slip occurs seismically or aseismically depends on the frictional properties of the fault which might be expected to depend on rock type and depth as well as other factors to examine the effect of rock type and depth on the distribution of earthquakes we compare geologic models of the san francisco bay and the southern california regions to the distribution of seismicity we normalize the number of earthquakes within each rock type and depth interval by the corresponding volume to determine the earthquake density earthquake density is determined primarily by depth while whether the rock is sedimentary or basement has only a secondary depth dependent effect on the earthquake density at very shallow depths there is no difference in earthquake density between sedimentary and basement rocks the earthquake density of basement rocks increases with depth more rapidly than that of sedimentary rocks to a similar but shallower maximum

the molecular composition of cretaceous ambers identification and chemosystematic relevance of 1 6 dimethyl 5 alkyltetralins and related bisnorlabdane biomarkers abstract one of the major components of the organic solvent extractable fraction of cretaceous ambers is 1 6 dimethyl 5 isopentyltetralin a compound that has been incorrectly or not identified in previous reports on the molecular composition of cretaceous ambers here the purification and structural identification of 1 6 dimethyl 5 isopentyltetralin is reported from amber samples of the cretaceous penacerrada ii deposit at penacerrada alava basque cantabrian basin spain the structural identification of 1 6 dimethyl 5 isopentyltetralin allowed the complete identification of related compounds comprising the family of 1 6 dimethyl 5 alkyltetralins this suggests that those compounds with concentrations up to 27 of the total organic extract of amber from penacerrada are characteristic for labdane type biomarkers in cretaceous fossil resins and their distributions indicate different compositional families related to their botanical and topographic origin also the name amberene is proposed for the main molecule of this group the relative proportion of the amberene type compounds suggests three compositional families for the cretaceous spanish ambers

early diagenetic partial oxidation of organic matter and sulfides in the middle pennsylvanian desmoinesian excello shale member of the fort scott limestone and equivalents northern midcontinent region usa a process of early diagenetic partial oxidation of organic matter and sulfides has altered the chemical composition of the middle pennsylvanian excello shale member of the fort scott limestone and equivalents in the northern midcontinent region this process was identified by comparison of organic carbon contents rock eval hydrogen indices organic carbon 13c and element compositions of core and surface mine samples of the excello shale member with analyses of three other underlying and overlying organic matter rich marine shales offshore shale lithofacies from southern iowa northern missouri eastern kansas and northeastern oklahoma the end product of the partial oxidation process is shale with relatively low contents of hydrogen poor c13 enriched organic matter lower contents of sulfur and sulfide forming elements and relatively unchanged contents of phosphorus and many trace elements e g cr ni and v however because of lower organic carbon contents element organic carbon ratios are greatly increased the partial oxidation process apparently took place during subaerial exposure of the overlying marine carbonate member blackjack creek member of the fort scott limestone following a marine regression when meteoric waters percolated down to the level of the excello muds allowing oxidation of organic matter and sulfides this hypothesis is supported by earlier workers who have identified meteoric carbonate cements within and soil horizons at the top of the blackjack creek member the period of oxidation is constrained in that organic matter and sulfides in the little osage shale member of the fort scott limestone and equivalents immediately overlying the blackjack creek member appear unaltered similar alteration of other shales in the middle and upper pennsylvanian sections may be local to regional in extent and would depend on the extent and duration of the marine regression and be influenced by local variations in permeability and topography the partial oxidation process has likely led to a redistribution of sulfur and sulfide forming elements into other organic rich lithologies in the section the altered oxidized shales are nongenerative with respect to hydrocarbon generation

time dependent changes for midcontinent pennsylvania black shales u s a abstract three types of midcontinent north american black shale types have been recognized based on metal content organic carbon contents sulfur isotopes and various other sedimentological and paleontological characteristics that may reflect fluctuations in bottom water oxygenation during deposition near shore middle pennsylvanian black shales exemplified by the mecca quarry shale member of indiana typically yield degree of pyritization dop values near 0 65 the highest measured in the study consistent with relatively but not fully anoxic conditions of sedimentation dop values for heebner type shales most prevalent in the upper pennsylvanian average 0 27 0 35 barely in the dysaerobic range which is difficult to reconcile with an origin for black shale dependent upon upwelling bottom water positive correlations exist between dop metal values and total organic carbon toc in black shale units through the pennsylvania these changes can be related to organic carbon production and published sea level fluctuations suggesting a change in black shale character in the midcontinent from the middle to late pennsylvanian consistently decreasing values for dop and toc through time suggest the likelihood of a progressive ventilation or improved bottom water oxygenation accompanied by a reduced rate of input from terrestrial organic matter during this time interval

rare earth elements and yttrium in pennsylvanian coals and shales in the eastern part of the illinois basin abstract the objective of this study was to evaluate rare earth elements and yttrium rey concentrations in pennsylvanian coal bearing strata in the eastern part of the illinois basin indiana specifically targeting coals and marine shales associated with the coals samples were collected from several coal mines and three boreholes in total 105 samples were analyzed using inductively coupled plasma optical emission spectrometry icp oes including 69 coals 31 shales and 5 paleosols concentrations of rey in the coals vary from less than 200 ppm to more than 3000 ppm on ash basis indirect evidence including rey versus ash relationships rey distribution patterns and rey content in raw coal compared to that in washed coal suggests that the organic association may be an important mode of rey occurrence in these coals the lower block and the upper block coal members of the brazil formation and some coals of the staunton formation have the highest rey concentrations among those studied concentrations of rey in marine shales range from less than 200 to 800 ppm on ash basis the majority of shale samples studied vary little from the rey values of the continental crust but some show enrichments our results suggest that while post combustion coal ash of the high rey coals are a potential source of these elements significant efforts and resources are needed to make the studied shales a viable rey resource

frictional properties of shale reservoir rocks 1 we performed laboratory friction experiments on shale samples from three hydrocarbon reservoirs to assess compositional controls on fault slip behavior accompanying hydraulic stimulation the samples span a range of clay and total organic content from 10 to 60 by weight and demonstrate fine scale heterogeneity within each reservoir friction measurements demonstrate strong dependence of strength and rate state constitutive properties on shale composition shale samples with clay and organic content above 30 by weight show coefficient of friction 0 4 and consistently velocity strengthening behavior while those below this threshold show increased strength and velocity weakening behavior this transition in frictional strength and stability suggests a change in the shale grain packing framework from rigid clast supported to clay mineral and organic matter supported measurements of gouge dilatancy further support these relationships showing a negative correlation with clay and organic content critical slip evolution distance exhibits similar dependence on composition implying common micromechanical mechanisms for the observed transition in frictional behavior we performed microstructural characterization of the experimental samples and observe changes in the gouge load bearing framework and shear localization features consistent with these mechanical data while these results can be applied generally to infer slip stability on faults in clay bearing sedimentary rock we employ the experimental data to place constraints on microearthquake magnitudes and the occurrence of slow shear slip on preexisting faults during hydraulic stimulation in shale reservoirs

a modern vs permian black shale the hydrography primary productivity and water column chemistry of deposition the sediment currently accumulating in the cariaco basin on the continental shelf of venezuela has an elevated organic carbon content of approximately 5 is accumulating under o2 depleted bottom water conditions so42 reduction is composed dominantly of foraminiferal calcite diatomaceous silica clay and silt and is dark greenish gray in color upon lithification it will become a black shale recent studies have established the hydrography of the basin and the level of primary productivity and bottom water redox conditions these properties are used to model accumulation rates of cd cr cu mo ni v and zn on the seafloor the model rates agree closely with measured rates for the uppermost surface sediment the model is applied to the meade peak phosphatic shale member of the phosphoria formation a phosphate deposit of permian age in the northwest united states it too has all of the requisite properties of a black shale although the deposit is a world class phosphorite it is composed mostly of phosphatic mudstone and siltstone chert limestone and dolomite it has organic carbon concentrations of up to 15 is strongly enriched in several trace elements above a terrigenous contribution and is black the trace element accumulation defines a mean primary productivity in the photic zone of the phosphoria basin as moderate at 500 g m 2 year 1 organic carbon comparable to primary productivity in the cariaco basin the source of nutrient enriched water that was imported into the phosphoria basin upwelled into the photic zone and supported primary productivity was an o2 minimum zone of the open ocean the depth range over which the water was imported would have been between approximately 100 and 600 m the mean residence time of bottom water in the basin was approximately 4 years vs 100 years in the cariaco basin the bottom water was o2 depleted but it was denitrifying or no3 reducing rather than so42 reducing

on the mechanical role of smectite in subduction zones smectites a group of hydrated phyllosilicate minerals are often a main component of sediments entering a subduction zone they are common in hemipelagic sediments and consist of an authigenetic component that arises from the alteration of volcanic ash intercalated in the sediment and a detrital component smectite rich strata are structurally weak retain water and are highly porous a review of sediment lithology in subduction zones around the world suggests that decollement zones may preferentially form in smectite rich horizons one consequence of this observation is that the assignment of high frictional resistance to materials in a decollement may be unwarranted at deeper structural levels smectite is transformed to illite a mechanically stronger mineral estimates of the depth of this transition coincide with the depth at which earthquakes are first detected along plate interfaces i speculate that the smectite illite transition in subduction zones may be an important component of sediment consolidation processes that trigger interplate seismicity

frictional behavior of materials in the 3d safod volume 1 we report on frictional properties of rocks within the 3 d crustal volume surrounding the san andreas fault observatory at depth safod samples include lithologies adjacent to the san andreas fault saf in the subsurface safod borehole rocks and synthetic fault gouge composed of talc serpentinite and quartz granodiorite arkosic sandstone and siltstone samples from the safod borehole are frictionally strong 0 56 0 66 sand and clay rich lithologies from outcrop exhibit friction in the range 0 56 0 68 natural serpentinite thought to abut the saf at depth exhibits low friction 0 18 0 26 our results indicate that 1 serpentinite exhibits low strength but is not weak enough to completely satisfy weak fault models 2 all other samples are consistent with a strong fault and crust and 3 if the saf is weak 0 2 due to the presence of serpentinite or talc these minerals would likely need to constitute over 50 by weight of the shear zone

the nature and fate of natural resins in the geosphere iv middle and upper cretaceous amber from the taimyr peninsula siberia evidence for a new form of polylabdanoid of resinite and revision of the classification of class i resinites abstract analysis of three amber resinite samples collected from middle and upper cretaceous sediments in the taimyr peninsula siberia indicates that these materials are based on copolymers of biformene i and communol ii these resinites represent a previously undescribed form of class i polylabdanoid resinite definitions of the sub classes of class i resinites have been revised generalized to recognize the general relation between these samples and other class ib resinites and to facilitate classification of polylabdanoid resinites which do not necessarily incorporate communic or ozic acids

uranium enrichment in lacustrine oil source rocks of the chang 7 member of the yanchang formation erdos basin china abstract the oil source rocks of the chang 7 member of the yanchang formation in the erdos basin were deposited during maximum lake extension during the late triassic and show a remarkable positive uranium anomaly with an average uranium content as high as 51 1 g g uranium is enriched together with organic matter and elements such as fe s cu v and mo in the rocks the detailed biological markers determined in the chang 7 member indicate that the lake water column was oxidizing during deposition of the chang 7 member however redox indicators for sediments such as s 2 content v sc and v v ni ratios demonstrate that it was a typical anoxic diagenetic setting the contrasted redox conditions between the water column and the sediment with a very high content of organic matter provided favorable physical and chemical conditions for syngenetic uranium enrichment in the oil source rocks of the chang 7 member possible uranium sources may be the extensive u rich volcanic ash that resulted from contemporaneous volcanic eruption and uranium material transported by hydrothermal conduits into the basin the uranium from terrestrial clastics was unlike because uranium concentration was not higher in the margin area of basin where the terrestrial material input was high as indicated by correlative analysis the oil source rocks of the chang 7 member show high gamma ray values for radioactive well log data that reflect a positive uranium anomaly and are characterized by high resistance low electric potential and low density as a result well log data can be used to identify positive uranium anomalies and spatial distribution of the oil source rocks in the erdos basin the estimation of the total uranium reserves in the chang 7 member attain 0 8 10 8 t

thin widespread pennsylvanian black shales of midcontinent north america a record of a cyclic succession of widespread pycnoclines in a fluctuating epeiric sea

biomarkers of holocene buried conifer logs from bella coola and north vancouver british columbia canada abstract the biomarker compositions of a holocene seep oil liquefied resin originating from a buried log of douglas fir pseudotsuga menziesii from bella coola bc canada and a holocene pine wood pinus sp sample from north vancouver bc canada were analyzed using gas chromatography mass spectrometry gc ms the total extract of the bella coola sample contains the sesquiterpenoid derivative calamenene and diterpenoids of the labdane abietane pimarane and phyllocladane classes a novel series of successively degraded labdane derivatives labdan 15 oic acid norlabdanoic acids drimenoic acid was detected in the polar fraction and a diagenetic pathway is proposed aromatic abietanes are the major components in the neutral fraction the neutral fraction of the pine wood contains two sesquiterpenoids calamenene cadalene diterpenoids of the abietane pimarane isopimarane and kaurane classes and a series of steroids 18 norabieta 8 11 13 triene dehydroabietin is the major component among the predominantly aromatic abietanes based on the compositions of the terpenoids it is concluded that the diagenesis of the pine and douglas fir logs probably occurred under anaerobic conditions leading to reductive reactions such as decarboxylation of resin acids with concurrent oxidation reactions to form the aromatic derivatives

vanadium accumulation in carbonaceous rocks a review of geochemical controls during deposition and diagenesis abstract published data relevant to the geochemistry of vanadium were used to evaluate processes and conditions that control vanadium accumulation in carbonaceous rocks reduction adsorption and complexation of dissolved vanadium favor addition of vanadium to sediments rich in organic carbon dissolved vanadate v v species predominate in oxic seawater and are reduced to vanadyl ion v iv by organic compounds or h 2 s vanadyl ion readily adsorbs to particle surfaces and is added to the sediment as the particles settle the large vanadium concentrations of rocks deposited in marine as compared to lacustrine environments are the result of the relatively large amount of vanadium provided by circulating ocean water compared to terrestrial runoff vanadium rich carbonaceous rocks typically have high contents of organically bound sulfur and are stratigraphically associated with phosphate rich units a correspondence between vanadium content and organically bound sulfur is consistent with high activities of h 2 s during sediment deposition excess h 2 s exited the sediment into bottom waters and favored reduction of dissolved v v to v iv or possibly v iii the stratigraphic association of vanadiferous and phosphatic rocks reflects temporal and spatial shifts in bottom water chemistry from suboxic phosphate concentrated to more reducing euxinic conditions that favor vanadium accumulation during diagenesis some vanadium organic complexes migrate with petroleum out of carbonaceous rocks but significant amounts of vanadium are retained in refractory organic matter or clay minerals as carbon in the rock evolves toward graphite during metamorphism vanadium is incorporated into silicate minerals

amber and organic matter from the late oligocene deep water deposits of the central western carpathians orava podhale basin abstract the occurrence of amber in the central carpathian paleogene basin is reported here for the first time the amber has been analyzed by means of optical microscopic methods infrared spectroscopy gas chromatography mass spectrometry and pyrolysis gas chromatography mass spectrometry to understand the amber composition origin taphonomy alteration and diagenesis organic petrographic and reflectance analyses of organic matter from amber bearing sediment was carried out to get information about paleoenvironment and maturity of sedimentary rock analyses confirmed polylabdane structure associated with class ib type of amber and its possible origin from the conifer family araucariaceae it is characterized by a high degree of maturity where both temperature and exogenic processes have participated in its conversion heterogeneity of reflectance values in the resinite suggests that amber was not redeposited from an older and more mature sedimentary unit the discrepancy between the maturity of the amber and amber bearing sedimentary rock along with abundant char and inertinite macerals indicates a probability of thermal alteration of the amber under the influence of heat from a wildfire and increased maturity occurring before its ultimate burial in a deep sea environment the assemblage of terrigenous macerals and numerous char and inertinite particles which were found in amber bearing sediment as well as in the amber crust suggest forest swamp type vegetation affected by wildfires the presence of amber and predominantly terrigenous organic matter besides mud rip up clasts derived from freshwater sediments in deep marine deposits indicates a direct connection of terrestrial environments to the deep water depositional system

frictional strengths of talc serpentine and talc quartz mixtures 1 talc is a constituent of faults in a variety of settings and it may be an effective weakening agent depending on its abundance and distribution within a fault we conducted frictional strength experiments under hydrothermal conditions to determine the effect of talc on the strengths of synthetic gouges of lizardite and antigorite serpentinites and of quartz small amounts of talc weaken serpentinite gouges substantially more than predicted by simple weight averaging in comparison mixtures of quartz and talc show a linear trend of strength reduction at talc concentrations 15 wt and enhanced weakening at higher concentrations all of the strength data are fit by a modified version of the reuss mixing law that allows for the dominance of one mineral over the other the difference in the behavior of serpentinite talc and quartz talc mixtures at low talc concentrations is a reflection of their different textures lizardite antigorite and talc all have platy habits and displacement within gouges composed of these minerals is localized to narrow shears along which the platy grains have rotated into alignment with the shear surfaces the shears in the mixed phyllosilicate gouges maximize the proportion of the weaker mineral within them when mixed with a strong rounded mineral such as quartz some minimum concentration of talc is needed to form connected pathways that enhance strength reductions the typical development of talc by the reaction of si rich fluids with serpentinite or dolomite would tend to localize its occurrence in a natural fault and result in enhanced weakening

sedimentary corg p ratios paleocean ventilation and phanerozoic atmospheric po2 the corg p ratios of organic rich facies tocn1 exhibit considerable variation through the phanerozoic from b10 1 in the permian phosphoria formation to n1000 1 in some devonian black shales relative to the composition of phytoplankton c p 106 1 which provide the bulk of organic c and p to organic rich marine sediments the range of phanerozoic sedimentary corg p ratios largely reflects the influence of benthic redox conditions on diagenetic pathways of c and p remobilization enhanced preservationoforganiccatlowerredoxpotentials combinedwithenhancedsedimentaryretentionofremineralizedorganicpathigher redox potentials results in a strong relationship between benthic redox conditions and sedimentary corg p ratios the strong secular coherence of the phanerozoic corg p record i e limited variation within narrow time slices suggests that these ratios are controlled primarily by factors influencing benthic redox conditions on a global scale such as atmospheric po2 inversion and scaling of the phanerozoic corg p record yields a new atmospheric po2 model that has strong similarities to existing models based on elemental and isotopic mass balances yet differs in some potentially significant respects in particular the new model suggests that atmospheric po2 wasmarkedlylowerduringtheearlytomiddlepaleozoicthanpreviouslyinferred duringmostofthedevonian atmospherico2levels mayhavebeensufficientlylow b13 astopreventthesustainedcombustionofplantmaterial thisfeatureofthemodelmayaccount for ananomalous gapinthefossilcharcoalrecordduringthedevonian theredox dependentburialofpintheoceanresults inpositive and negative feedback mechanisms that tend to stabilize atmospheric oxygen concentrations on geologic timescales temporal variations in the burial of p relative to c suggest that the strength of these feedback mechanisms varied over the phanerozoic 2007 elsevier b v all rights reserved

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

taphonomy of insects in carbonates and amber abstract the major taphonomic processes that control insect preservation in carbonate rocks limestones travertines and nodules are biological insect size and wingspan degree of decomposition presence of microbial mats predation and scavenging environmental water surface tension water temperature density and salinity current activity and diagenetic authigenic mineralisation flattening deformation carbonisation the major taphonomic processes that control the preservation of insects in fossil resins amber and copal are different but can be considered under the same headings biological presence of resin producers size and behaviour of insects environmental latitude climate seasonality resin viscosity effects of storms and fires soil composition and diagenetic resin composition insect dehydration pressure carbonisation thermal maturation reworking oxidation these taphonomic processes are geographically and temporally restricted and generate biases in the fossil record nevertheless where insects occur they may be abundant and very diverse taphonomic processes may impact on phylogenetic and palaeobiogeographic studies in determining the timing of the origin and extinction of insect groups and in identifying radiations and major extinctions taphonomic studies are an essential prerequisite to the reconstruction of fossil insect assemblages to interpreting the sedimentary and environmental conditions where insects lived and died and to the investigation of interactions between insects and other organisms

novel phenolic biomarker triterpenoids of fossil laticifers in eocene brown coal from geiseltal germany abstract novel phenolic triterpenoids were tentatively identified with known mono tri and tetraaromatic oleanane ursane and lupane hydrocarbons and natural product precursors amyrone amyrin in the extract of eocene fossil laticifers called affenhaar from the geiseltal lignites germany the novel phenolic terpenoids are mono and triaromatic hydroxytriterpenoids oh at position 1 2 or 3 of the oleanane ursane and lupane classes hydroxy 24 25 dinoroleana 1 3 5 10 12 tetraene hydroxy 24 25 dinorlupa 1 3 5 10 triene hydroxy 24 25 dinorlupa 1 3 5 10 19 22 tetraene hydroxy 24 25 26 27 tetranorursa 1 3 5 7 9 11 13 heptaene hydroxy 24 25 26 27 tetranoroleana 1 3 5 7 9 11 13 heptaene and hydroxy 24 25 26 27 tetranorlupa 1 3 5 7 9 11 13 heptaene the structures of the novel compounds were proposed based on the interpretation of the gas chromatography mass spectrometry data of the underivatized and silylated total extract

guidelines for evaluating petroleum source rock using programmed pyrolysis rock eval pyrolysis is used to rapidly evaluate the petroleum generative potential and thermal maturity of rocks accurate conclusions require programs every 30 60 ft 9 18 m understanding of interpretive pitfalls and supporting data such as visual kerogen vitrinite reflectance and elemental analyses the generative potential of coals is commonly overestimated by pyrolysis and is best determined by elemental analysis and organic petrography most coals show high s2 s3 5 and low hi values 300 mg hc g toc migrated oil and mud additives which alter rock eval data can sometimes be removed by special processing for immature rocks bimodal s2 peaks and pi values over 0 2 indicate contamination pyrolysis downgrades organic poor clay rich rocks which show lower hi and higher tmax values than isolated kerogen because of adsorption of pyrolyzate on the clays tmax values for small s2 peaks 0 2 mg hc g toc are unreliable tmax is affected by maturation organic matter type contamination and the mineral matrix s3 is sensitive to inorganic and adsorbed carbon dioxide and to instrumentation problems acidification of carbonate rich samples and proper maintenance improves s3 measurement constant sample weights 100 mg are recommended below a threshold weight tmax increases by up to 10 c and other parameters decrease organic rich samples which overload the detector can be diluted with carbonate detector linearity is determined by pyrolyzing various weights of an organic rich rock

terpenoids in extracts of lower cretaceous ambers from the basque cantabrian basin el soplao cantabria spain paleochemotaxonomic aspects the composition of terpenoids from well preserved cretaceous fossil resins and plant tissues from the amber bearing deposits of el soplao and reocin in cantabria northern spain have been analyzed using gas chromatography mass spectrometry and the results are discussed using the terpenoid composition of extant conifers as a reference amber is present at many horizons within two units of coastal to shallow marine siliciclastics of albian and cenomanian age the fossil resins are associated with black amber jet and abundant well preserved plant cuticle compressions especially those of the extinct conifer genus frenelopsis cheirolepidiaceae we report the molecular characterization of two types of amber with different botanical origins one of them is characterized by the significant presence of phenolic terpenoids ferruginol totarol and hinokiol and pimaric isopimaric acids as well as their diagenetic products the presence of phenolic diterpenoids together with the lack of abietic and dehydroabietic acids excludes both pinaceae and araucariaceae as sources for this type of amber the biological diterpenoid composition is similar to that observed for extant cupressaceae the second type of amber is characterized by the absence of phenolic terpenoids and other specific biomarkers some terpenoids with uncertain structure were detected as well as the azulene derivative guaiazulene our results suggest that the amber from cantabria could be fossilized resin from frenelopsis and other undetermined botanical sources the biological terpenoid assemblage confirms a chemosystematic relationship between frenelopsis and modern cupressaceae

applying a three dimensional velocity model waveform cross correlation and cluster analysis to locate southern california seismicity from 1981 to 2005 we compute high precision earthquake locations using southern california pick and waveform data from 1981 to 2005 our latest results are significantly improved compared to our previous catalog by the following 1 we locate events with respect to a new crustal p and s velocity model using three dimensional ray tracing 2 we examine six more years of waveform data and compute cross correlation results for many more pairs than our last analysis and 3 we compute locations within similar event clusters using a new method that applies a robust fitting method to obtain the best locations satisfying all the differential time constraints from the waveform cross correlation these results build on the relocated catalogs of hauksson and shearer 2005 and shearer et al 2005 and provide additional insight regarding the fine scale fault structure in southern california and the relationship between the san andreas fault saf and nearby seismicity in particular we present results for two regions in which the seismicity near the southern saf seems to align on dipping faults

induced seismicity in the geysers geothermal area california a simultaneous inversion for hypocenters velocities and station delays was performed from the p arrival times of 55 microearthquakes and four explosions distributed throughout a 90 by 100 km region centered at the geysers geothermal area in northern california the resulting one dimensional layered model shows velocity increasing with depth from 4 4 km s at the surface to 5 9 km s at 8 km and deeper we relocated 7215 earthquakes which occurred between may 1975 and february 1982 using the new velocity model these relocations show a significant spatial clustering near production wells in the steam field that was not apparent in earlier studies we infer from the spatial and temporal pattern of seismicity that the seismicity at the geysers is induced by geothermal production activities with the expansion of power production by approximately 70 in 1979 1980 seismic activity has developed near the new production areas seismicity has also expanded northwestward of the present production area although there are no active steam wells in this area statistical cross correlations between the number of earthquakes per month and both steam withdrawal per month and injection volume per month were calculated for the wells studied we find no consistent pattern of correlation between injection and seismicity likewise we find little or no correlation between steam withdrawal and seismicity for steam wells in production longer than 7 years two mechanisms remain plausible for inducing seismicity at the geysers volumetric contraction due to mass withdrawal may perturb the stress field and cause faulting in reservoir rock already near failure due to the regional stress field alternatively aseismic deformation due to regional tectonic stress may be converted to stick slip seismic deformation due to an increase of coefficient of friction along fault surfaces such as could occur from exsolution of dissolved silica into fractures neither mechanism would be likely to show strong correlation between production and seismicity rates however we expect seismicity to continue in the geysers and for seismicity to appear in areas where new production occurs

generic dependence of the frequency size distribution of earthquakes on depth and its relation to the strength profile of the crust 1 we explore the idea that the relative size distribution of earthquakes quantified using the so called b value is negatively correlated with differential stress because the maximum possible differential stress increases linearly in the brittle upper crust we expect to find a decrease of b with depth we test this expectation for seven continental areas around the world each of which is described by a regional earthquake catalog we find a monotonic decrease in b value between 5 and 15 km depth the decrease stops near the brittle ductile transition we specifically focus on the high quality catalogs of earthquakes in california to perform a sensitivity test with respect to depth uncertainty we also estimate the probability depth gradient for the occurrence of a target magnitude event and study the behavior of b with depth in near and off fault zones we also translate the observed b depth gradients into b differential stress gradients our findings suggest that b values are negatively correlated with differential stress and hus have the potential to act as stress meters in the earth s crust

the paleogene vegetation and petroleum system in the tropics a biomarker approach abstract the present study investigates the biomarker signatures of sediments and crude oils to infer the paleovegetation from the two petroleum systems of assam basin eastern india they are classified as the paleocene middle eocene and the middle eocene oligocene petroleum systems the sediments are oil and gas prone with an early catagenetic stage of thermal evolution here we report tricyclic diterpanes such as rimuane pimarane rosane and isopimarane along with tetracyclic diterpanes ent beyerane phyllocladane kaurane from paleocene eocene coal bearing sediments and crude oils these diterpane biomarkers attest dominant contribution from conifers possibly from podocarpaceae and araucariaceae however diterpanes are not detected in oligocene sediments and oils crude oils from both paleocene eocene and oligocene reservoirs and organic rich sediments contain angiosperm biomarkers such oleanane and related triterpanes along with bicadinane a biomarker specific for the dipterocarpaceae family of angiosperms the equatorial position of india during early paleogene along with the presence of angiosperm signatures including dipterocarpaceae and gymnosperms reflect the emergence of tropical rainforest elements in eastern india absence of diterpenoids in oligocene samples and difference in angiosperm parameters from paleocene eocene samples suggests a change in source vegetation and organofacies

brachiopod geochemical records from across the carboniferous seas of north america evidence for salinity gradients stratification and circulation patterns abstract stable isotopic analyses of 100 well preserved carboniferous brachiopod shells representing two time slices from across north america reveal systematic regional changes in environmental conditions for both of the time slices studied the chesterian latest mississippian and the virgilian latest pennsylvanian 18o and 13c show a stepwise decrease moving across the continent from modern day west to east higher 18o in the west reflects greater water depths less freshwater input and more direct upwelling influence from cool open marine waters than in the east modelling based on these regional isotopic data indicates salinity reductions on the order of 1 4 psu in the appalachian basin relative to the midcontinent basin for the virgilian time interval over a range of reasonable thermal gradient and 18ofw assumptions the magnitude of this gradient is similar to those of modern day hudson bay and the panama bight which exhibit permanent haloclines driven by freshwater discharge considering existing paleoecological evidence for freshening the lack of more dramatic benthic freshening suggests that the depth of a regional halocline was shallower than the depths inhabited by thick shelled stenotopic brachiopods although other lines of evidence are necessary to verify the strength of the halocline estimated 18o temperatures for appalachian basin brachiopods are 3 5 c cooler than those of coeval conodonts due to either slightly warmer fresher surface waters or uncertainty in the phosphate 18o paleothermometer despite discrepancies in calculated temperatures the magnitude of the regional isotopic gradient derived from brachiopod and conodont proxies is similar after making appropriate glacioisotopic and water depth corrections a decreasing 13c trend toward the east southern paleolatitude likely reflects greater restriction and terrestrial influence near the sea s tropical shoreline trace element trends are less consistent and are affected by species and metabolism erratic variations in mg ca concentrations even among pristine samples of the same genera with similar 18o values and unrealistic mg ca derived temperatures justify continued caution in applying existing mg ca thermometer equations to paleozoic brachiopods

secular distribution of highly metalliferous black shales corresponds with peaks in past atmosphere oxygenation highly metalliferous black shales hmbs are enriched in organic carbon and a suite of metals including ni se mo ag au zn cu pb v as sb se p cr and u pge compared to common black shales and are distributed at particular times through earth history they constitute an important future source of metals hmbs are relatively thin units within thicker packages of regionally extensive continental margin or intra continental marine shales that are rich in organic matter and bio essential trace elements accumulation and preservation of black shales and the metals contained within them usually require low oxygen or euxinic bottom waters however whole rock redox proxies particularly mo suggest that hmbs may have formed during periods of elevated atmosphere po2 this interpretation is supported by high levels of nutrient trace elements within these rocks and secular patterns of se and se co ratios in sedimentary pyrite through earth history with peaks occurring in the middle paleoproterozoic early cambrian to early ordovician middle devonian middle to late carboniferous middle permian and middle to late cretaceous all corresponding with time periods of hmbs deposition this counter intuitive relationship of strongly anoxic to euxinic localized seafloor conditions forming under an atmosphere of peak oxygen concentrations is proposed as key to the genesis of hmbs the secular peaks and shoulders of enriched se in sedimentary pyrite through time correlate with periods of tectonic plate collision which resulted in high nutrient supply to the oceans and consequently maximum productivity accompanying severe drawdown into seafloor muds of c s p and nutrient trace metals the focused burial of c and s over extensive areas of the seafloor during these anoxic to euxinic periods likely resulted in an o2 increase in the atmosphere causing short lived peaks in po2 that coincide with the deposition of hmbs as metals become scarce particularly mo ni se ag and u the geological times of these narrow hmbs horizons will become a future focus for exploration

biomarker signatures of permian gondwana coals from india and their palaeobotanical significance abstract coal samples belonging to the lower permian barakar formation and the upper permian raniganj formation collected from damodar valley basin of eastern india have been analysed for understanding their organic geochemical characteristics using rock eval pyrolysis gas chromatography mass spectrometry gc ms and comprehensive two dimensional gas chromatography coupled with time of flight mass spectrometry gc gc tofms the rock eval pyrolysis parameters suggest that the coals from both the formations contain a mixture of type ii and type iii kerogen the rock eval tmax values of the analysed coals vary from 417 to 451 c n alkanes ranging from c12 to c31 predominate the aliphatic hydrocarbons present in the coal extracts the carbon preference indices cpi as well as the odd to even preference oep values of the n alkanes are 1 suggesting input from higher vascular land plants c29 steranes predominate over c27 and c28 steranes which corroborates contribution from terrestrial higher plants aliphatic diterpanes like ent beyerane isopimarane abietane phyllocladanes and ent kaurane as well as aromatic diterpanes like simonellite bisnorsimonellite retene methylretenes and tetrahydroretene which are mainly known to originate from conifers are detected in the studied coals the lower gondwana floral assemblage of peninsular india is mainly represented by glossopteris flora pteridospermatophyta however some primitive conifers have also been reported from this succession we propose that the diterpanes detected in the studied coals were possibly derived from the primitive conifers this implies that the biosynthetic pathways to produce these diterpanes had evolved in the gondwana flora during the permian period

effects of thermal maturity on biomarker distributions in gondwana coals from the satpura and damodar valley basins india abstract organic geochemistry of gondwana coals especially the distribution of molecular fossils or biomarkers is not well constrained throughout the world in this study we have therefore evaluated biomarker signatures along with bulk organic matter and petrographic characteristics in coal samples collected from two gondwana basins in india satpura basin kanhan coalfield and damodar valley basin jharia coalfield from both coalfields the samples were collected from the lower permian barakar formation which is one of the major coal bearing strata in india a significant variation in thermal maturity levels in the samples is indicated by rock eval pyrolysis and petrographic analysis with the kanhan samples generally belonging to immature to early mature stage while the jharia samples display characteristics of overmature coals this variation in the thermal maturity strongly affects the biomarker distributions especially the terpenoids hopanes and steranes were considerably degraded due to thermal maturation and were below detection limit in the overmature samples presence of aliphatic diterpanes ent 16 h kaurane 16 h phyllocladane as well as aromatic diterpanes retene methylretenes tetrahydroretene simonellite and bisnorsimonellite in low maturity samples indicate terrestrial input possibly from the primitive conifers however the aliphatic and aromatic diterpanes were below detection limit in overmature samples making it difficult to infer their source distributions of polycyclic aromatic hydrocarbons pahs are also controlled by thermal maturity levels as evident from difference in pah ratios in the low and high maturity samples

effects of simulated clay gouges on the sliding behavior of tennessee sandston abstract the effects of simulated fault gouge on the sliding behavior of tennessee sandstone are studied experimentally with special reference to the stabilizing effect of clay minerals mixed into the gouge about 30 specimens with gouge composed of pure clays of homogeneously mixed clay and anhydrite or of layered clay and anhydrite along a 35 precut are deformed dry in a triaxial apparatus at a confining pressure of 100 mpa with a shortening rate of about 5 10 4 sec and at room temperature pure clay gouges exhibit only stable sliding and the ultimate frictional strength is very low for bentonite mont morillonite intermediate for chlorite and illite and considerably higher for kaolinite anhydrite gouge shows violent stick slip at 100 mpa confining pressure when this mineral is mixed homogeneously with clays the frictional coefficient of the mixed gouge determined at its ultimate frictional strength decreases monotonically with an increase in the clay content the sliding mode changes from stick slip to stable sliding when the frictional coefficient of the mixed clay anhydrite gouge is lowered down below 90 95 of the coefficient of anhydrite gouge the stabilizing effect of clay in mixed gouge is closely related to the ultimate frictional strength of pure clays that is the effect is conspicuous only for a mineral with low frictional strength only 15 20 of bentonite suppresses the violent stick slip of anhydrite gouge in contrast violent stick slip occurs even if the gouge contains as much as 75 of kaolinite the behavior of illite and chlorite is intermediate between that of kaolinite and bentonite bentonite anhydrite two layer gouge exhibits stable sliding even when the bentonite content is only 5 thus the presence of a thin clay rich layer in a fault zone stabilizes the behavior much more effectively than do the clay minerals mixed homogeneously with the gouge this result brings out the mechanical significance of internal structures of a fault zone in understanding the effects of intrafault materials on the fault motion based on the present experimental results incorporated with some other experimental data it is argued that although the stabilizing effect of montmorillonite and vermiculite is indeed remarkable at room temperature the effect should be much less pronounced at elevated temperatures due perhaps to the dewatering of the clays in most geological environments where shallow earthquakes occur the stabilizing effect of clays is probably not so conspicuous as to completely suppress the unstable motion of a fault

identification of aryl isoprenoids in source rocks and crude oils biological markers for the green sulphur bacteria abstract a series of c13 to c31 aryl isoprenoids 1 alkyl 2 3 6 trimethylbenzenes have been identified in reef hosted oils and their source rocks from the middle and upper silurian of the michigan basin and middle devonian of the alberta basin canada their structure has been confirmed by unambiguous synthesis of the c14 member of the series their structure and isotopic composition indicate that they are derived from isorenieratene from the chlorobiaceae family of sulphur bacteria these results are consistent with geological and geochemical studies that show that the source rocks were deposited under metahaline to hypersaline sulphate and sulphide rich water columns the distribution of other biomarkers in these oils and source rocks indicates that a diverse biota contributed organic matter to the source environment in conjunction with the aryl isoprenoids they show that there is a remarkable similarity in composition between the two sets of oils and source rocks despite their great temporal and geographic separation this reflects the similarity of their environments and emphasizes the importance of sedimentary facies in controlling the composition of organic matter in source rocks and their derived oils

aromatic hydrocarbon biomarkers in terrestrial organic matter of devonian to permian age abstract this paper presents the results of a detailed study on the occurrence and distribution of alkylnaphthalenes and alkylphenanthrenes in 39 coal and sediment samples from the late palaeozoic containing predominantly terrestrial organic matter most of the samples represent the euramerian flora realm and originate from locations beyond the variscan front in eastern northern and central europe i e especially england and the moscow basin the samples are of relatively low maturity 0 32 to 1 80 rr and consist mainly of mixtures of type iii and ii kerogen quantification of the c0 to c4 naphthalenes and the c0 to c4 phenanthrenes showed that these compound classes were highly abundant in all samples aromatic hydrocarbon maturity parameters in general are in good agreement with measured vitrinite reflectance values 1 2 7 trimethylnaphthalene an assumed diagenetic product of oleanane type biomarkers was present in all investigated samples this observation provides evidence that oleanane type lipids were biosynthesised by organisms predating the evolution of angiosperms or that assumed formation pathways for 1 2 7 trimethylnaphthalene are insecure 1 2 8 trimethylphenanthrene was significantly enriched in samples from the permian and the one sample from the devonian investigated in this study the precursor s of 1 2 8 trimethylphenanthrene therefore may have been produced by organisms which were least abundant in the carboniferous depositional environments represented by our samples

molybdenum and other heavy metals of the mecca quarry and logan quarry shales pennsylvanian age mecca quarry shale from illinois and indiana contains enriched values of mo and other heavy metals average values range up to 1 160 ppm mo 8 970 ppm zn 160 ppm u 320 ppm pb 250 ppm se 420 ppm cu 450 ppm ni and 5 970 ppm v for full thicknesses pennsylvanian logan quarry shale of indiana carries similar enrichments of heavy metals for both shales trace element contents correlate markedly with specific lithologies most samples were analyzed by quantitative x ray fluorescence near shore deposition in brackish waters for the indiana locations deeper more characteristically marine environment for illinois despite high trace element values in both shales e g near ore grades for mo their thinness generally less than 1 m and the fine grained dispersed nature of their host phases relegate these shales to the status of long term resources unless improved beneficiation techniques can be devised or appreciably higher grades can be found the association of these shales with subjacent minable coals however improves their economic outlook modified journal abstract

origins of metals and organic matter in the mecca quarry shale member and stratigraphically equivalent beds across the midwest samples of the middle pennsylvanian age mecca quarry shale member and stratigraphically equivalent beds from indiana illinois missouri and kansas have been analyzed for both inorganic and organic constituents trends for mo values reported by coveney and martin 1983 who found the highest tenors to be associated with the ancient shoreline in indiana have been confirmed regionally across the midwest similarly it has been found that cd v u se and sb are most concentrated near the shoreline whereas constituents such as ca and sr are richest offshore e g kansas organic matter analyses including pyrolysis gas chromatography show the eastern samples to be richest in total organic carbon and also in terrestrial organic matter unbuffered aqueous solutions containing powdered organic rich shales from indiana equilibrate to acid ph values ph 4 6 where mo is readily retained by organic matter laboratory experiments show the shales retain a capacity to fix mo from dilute solutions correlations between organic matter type and metal values such as those existing between mo and v and terrestrial organic matter in shale samples generally fit with the syngenetic model for metal fixation in near shore brackish waters proposed by coveney and martin 1983 however other evidence including the remnant activity of organic matter rich samples to fix metals suggests that nonsyngenetic agents such as basinal brines or meteoric fluids have probably augmented the metal contents of the deposits subsequent to sedimentation and diagenesis

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

early eocene amber from the pesciara di bolca lessini mountains northern italy abstract the occurrence of amber from the world famous fossil lagerstatte of pesciara di bolca verona province is here reported for the first time this amber has been carefully analysed by means of infrared spectrophotometry ftir thermogravimetric analysis tg differential thermogravimetric analysis dtg and elemental chemical analysis then the amber from bolca has been compared with other ambers of similar age among them a sample from the cava rossi quarry monte di malo vicenza province shows striking similarities in all the physical chemical characters the fossil content of the amber levels of the pesciara and cava rossi was examined with respect to the palynomorphs and larger foraminiferans this permitted to ascertain that the two amber levels are substantially isochronous within the resolution power of the larger foraminiferan biozones according to the shallow benthic biozonation the age is in both cases sbz 11 or middle cuisian early eocene moreover the fossil assemblages allowed to reconstruct the palaeoenvironments stressing they were in both case on a shallow carbonate platform relatively close to the shoreline the pesciara palaeoenvironment was very close to the continental areas and with peculiar conditions allowing the exceptional preservation of the fishes instead the cava rossi palaeoenvironment was more distal and open to marine influxes

metal organic relationships from the irish carboniferous abstract a number of metal organic relationships have been observed in the carboniferous of ireland they include metal enrichments within black shales bitumen nodules bituminous solution seams woody material vein bitumens and reservoir bitumens and the association of hydrocarbon gases and bitumens with base metal deposits the source for the metals may have been in the strata on which the carboniferous rocks were deposited or in their carboniferous erosion products both syngenetic and epigenetic mineralisation have been observed with organic material associated with both types of mineralisation the solid bitumens are residues of migrated fluid hydrocarbon which may have been produced by 330 ma late visean

conifer and angiosperm biomarkers in clay sediments and fossil plants from the miocene clarkia formation idaho usa the aliphatic lipids and terpenoids of conifer and angiosperm macrofossils and the clay sediment from a new site p 37 of the miocene clarkia formation idaho usa were analyzed to evaluate the preservation of characteristic conifer and angiosperm biomarkers in the sediment series of aliphatic lipids terpenoids and steroids similar to the biomarkers found in type locality clarkia p 33 were the predominant compounds in the sediment and in the fossils long chain aliphatic lipids were major compounds in the fossil plants and the sediment but a differentiation of angiosperm and conifer sources is not possible due to their common distribution among all vascular plants in addition to previously reported terpenoids diterpenoids of a conifer origin and several angiosperm derived polar triterpenoids of the oleanane lupane ursane and friedelane classes are reported here for the first time from the clarkia sediments the conifer shoots taxodium glyptostrobus calocedrus contained characteristic conifer biomarkers such as abietane type diterpenoids while characteristic angiosperm triterpenoids were predominant in the angiosperm leaves betula quercus lithocarpus the biomarker compositions of the taxodium and glyptostrobus shoots match the terpenoid patterns previously reported from fossil seed cones of the same genera although conifer macrofossils contribute about 45 to the flora of site p 37 characteristic conifer biomarkers occurred in the sediment in only low amounts while the angiosperm derived triterpenoids were present in comparatively higher abundances the results indicate that the conifers are under represented compared to the angiosperms according to the terpenoid composition of the sediment extract this may be due to the presence of small angiosperm derived particles leaf detritus wax in the sediment and or migration of leaf waxes from the angiosperm leaves into the sediment in contrast the diterpenoids are trapped in the resinous woody tissue of the conifers and are thus disseminated less into the sediment

ftir and statistical studies on amber artefacts from three romanian archaeological sites abstract in the present study fourier transform infrared spectroscopy in the reflectance mode ftir reflectance was performed on well preserved archaeological amber originating from three romanian archaeological sites of roman and byzantine cultures which did not allow sampling material resulting spectra were subjected to multivariate data analysis mda using principal components analysis pca in the light of the ftir reflectance bands of archaeological samples from the region 1275 to 1155 cm 1 and 900 600 cm 1 we could conclude that the samples from first two locations rosia montan and nuf ru are made from amber of baltic origin in the case of the third location isaccea we take into account the possibility of a mixture of raw materials both baltic and romanian amber these assertions are supported by statistical analysis and the historical context besides the ftir spectra comparison or other analytical data it is very important to correlate any information about the material colour conservation status historical context connections with other artefacts and the statistical analysis in order to favour safe conclusions

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

community fault model cfm for southern california we present a new three dimensional model of the major fault systems in southern california the model describes the san andreas fault and associated strike slip fault systems in the eastern california shear zone and peninsular ranges as well as active blind thrust and reverse faults in the los angeles basin and transverse ranges the model consists of triangulated surface representations t surfs of more than 140 active faults that are defined based on surfaces traces seismicity seismic reflection profiles wells and geologic cross sections and models the majority of earthquakes and more than 95 of the regional seismic moment release occur along faults represented in the model this suggests that the model describes a comprehen sive set of major earthquake sources in the region the model serves the southern california earthquake center scec as a unified resource for physics based fault systems modeling strong ground motion prediction and probabilistic seismic hazards assessment

high velocity frictional properties of gabbro high velocity friction experiments have been performed on a pair of hollow cylindrical specimens of gabbro initially at room temperature at slip rates from 7 5 mm s to 1 8 m s with total circumferential displacements of 125 to 174 m and at normal stresses to 5 mpa using a rotary shear high speed friction testing machine steady state friction increases slightly with increasing slip rate at slip rates to about 100 mm s velocity strengthening and it decreases markedly with increasing slip rate at higher velocities velocity weakening steady state friction in the velocity weakening regime is lower for the non melting case than the frictional melting case due perhaps to severe thermal fracturing a very large peak friction is always recognized upon the initiation of visible frictional melting presumably owing to the welding of fault surfaces upon the solidification of melt patches frictional properties thus change dramatically with increasing displacement at high velocities and such a non linear effect must be incorporated into the analysis of earthquake initiation processes

absolute location of 2019 ridgecrest seismicity reveals a shallow mw 7 1 hypocenter migrating and pulsing mw 7 1 foreshocks and duplex mw 6 4 ruptures

waveform relocated earthquake catalog for southern california 1981 to june 2011 we determine a new relocated catalog hys catalog 2011 for southern california from 1981 through june 2011 about 75 3 of the hypocenters are calculated with absolute and differential travel time picks and 24 7 could be relocated only by using absolute travel time picks with 3d or 1d velocity models the total catalog consists of more than 502 000 earthquakes in the region extending from baja california in the south to coalinga and owens valley in the north the catalog consists of three m 7 1 m 7 2 and m 7 3 mainshocks their foreshocks and aftershocks and background seismicity caused by tectonic and other processes in the southern california crust hypocenters in the new relocated catalog exhibit tighter spatial clustering of seismicity than does the routinely generated catalog and the depth distribution is tighter and reflects the thickness of the seismogenic zone more accurately compared to the standard catalog the relocated hypocenters are more easily related to other data sets such as mapped late quaternary faults

p wave seismic velocity structure derived from sonic logs and industry reflection data in the los angeles basin california 1 we present a new three dimensional seismic p wave velocity model of the los angeles basin that is based on more than 150 sonic logs and 7000 stacking velocities from industry reflection profiles the model was developed using kriging techniques implemented in gocad a commercial application specializing in the construction of surfaces the analysis of spatially distributed data and the modeling or simulation of properties and is characterized by a heterogeneous spatial varying velocity gradient with maximum velocities of 5000 m s in the sedimentary section variability of the observed p wave velocities increases with depth reflecting complex structural and sedimentological controls the model contains a new representation of the basin shape as defined by the sediment basement interface which was mapped using well control and seismic reflection profiles our model differs substantially in approach and outcome from previous representations of crustal velocity structure in southern california

cementation and blackening of holocene sands by peat derived humates a case study from the great dune of pilat landes des gascogne southwestern france abstract the base sand layers of the aeolian great dune of pilat which stretches along the coast of arcachon bay have been locally impregnated with a dark brown to black amorphous organic substance of humate composition the humate cemented sand forms a well indurated horizon 40 50 cm in thickness that developed immediately beneath the holocene peaty layer p1 paleosoil the humate identified by means of ft ir and raman micro spectroscopy acted both as a cementing agent and as a coloring agent it formed thin coats and meniscus cements between individual sandstone grains which in turn caused the dark asphaltic like appearance of the sandstone field observations combined with geochemical analyses and the presence of identical geochemical compounds recognized in the peat and sandstone humate cement suggest that the peat containing low coalified rr 0 2 fragments of higher submerged and floating plants and marine algae deposited in a saline and reducing environment served as an obvious source rock for the humate the humate derived from decaying organic remains that descended from the peat into the permeable sand where it indurated irreversibly over a period shorter than 3500 years the present day actions of waves and tides contribute to the erosion of the frontal parts of the humate impregnated sandstone horizon resulting in the formation of the dark rounded sandstone slabs and pebbles that are deposited on nearby beaches this process provides a fine example of recent black pebble formation that derived from pre existing organic matter impregnated source rocks in contrast to their tropical carbonate counterparts however the humate induced blackening of the sandstone pebbles appears to be relatively unstable as the impregnated fragments bleach when exposed to air and seawater for a few seasons

organic matter composition and distribution through the aptian albian lacustrine sequences of the araripe basin northeastern brazil abstract the main characteristics and distribution of organic matter have been studied through several aptian albian lacustrine units rio da batateira crato and ipubi formations araripe basin ne brazil six main facies have been distinguished on the basis of their lithological sedimentological characteristics and the type and amount of organic matter 1 marginal lacustrine deltaic massive to coarsely laminated mudstones and sandstones found as lenticular sheet and channel infills 2 oxic marginal lacustrine massive to poorly laminated mudstones 3 oxic suboxic inner lacustrine mudstones and laminated bioclastic mudstones 4 anoxic inner lacustrine dark mudstones 5 anoxic inner lacustrine dark clay carbonate rhythmites and 6 anoxic inner lacustrine finely laminated dark micritic limestones these facies make up decimeter to several meter thick parasequences which stack up in several tens of meters thick successions water level changes and variations of the detritic sediment contribution in the basin controlled the evolution of the depositional system palynomorph associations showed that the lacustrine system evolved in an arid semiarid tropical area where the most characteristic flora consisted of conifers gnetales bennettitales and early angiosperms in facies 1 to 3 organic matter was scarce poorly preserved and mainly derived from higher land plants facies 4 is characterised by containing abundant algal bacterial derived well preserved organic matter facies 5 and 6 contained mainly branchlets and pollen debris blown by the wind or fed by lacustrine underflows the pattern of organic matter accumulation and preservation corresponds well with cyclical palaeoenvironmental changes from anoxic to oxic bottom conditions and from a fresh to saline upper water layer which affected the shallow lacustrine system the deposition of thin organic matter rich mudstones facies 4 probably occurred during higher water levels which resulted in relatively low salinity waters and low detrital contribution to the inner lacustrine zones less significant organic matter accumulation is recorded in the clay carbonate rhythmites and in the limestones facies 5 and 6 due to scarce autochthonous aquatic organic matter deposition and pervasive intense bacterial degradation caused by persistent meromictic conditions large differences in the degree and path of evolution of the humic material derived from higher land plants have been detected depending on the depositional conditions the humic material in the oxic facies underwent humification and gelification and had the highest huminite reflectances whereas it showed suppressed reflectance values in the oil shales facies 4 and in the carbonate dominated facies in the latter extensive bacterial reworking of humic material is also observed these differences are considered significant and applicable to other case studies in terms of evaluating the maturity of organic matter in ancient lacustrine systems

terpenoid composition of fossil resins from western india new insights into the occurrence of resin producing trees in early paleogene equatorial rainforest of asia abstract the terpenoid composition of well preserved fresh and oxidized fossil resins ambers from early paleogene lignite bearing sequences of india have been examined using gas chromatography mass spectrometry for determining their botanical origin the samples were collected from two sedimentary basins viz barmer akli formation and bikaner nagaur palana formation western india the total extracts of the studied ambers are represented by hydronaphthalenes sesquiterpenoids and significant occurrence of diterpenoids such terpenoid distribution is typical for gymnosperm especially conifer derived sources the diterpenoids are comprised of majorly abietane phyllocladane kaurane pimarane isopimarane and podocarpane class compounds tertracyclic diterpenoids such as 18 norkauranes ent 16 h kaurane and 16 h phyllocladane and a rearranged tricyclic diterpenoid rosane are detected in the fossil resins from barmer basin the occurrence of tetracyclic diterpenoids and rosane together with 8 13 dimethyl 16 norpodocarpa 6 ene suggests that podocarpaceae family is the possible source of the ambers however chemotaxonomic assignment at family level for the fossil resin from bikaner nagaur basin is difficult due to the absence of source specific diterpenoids previous reports had documented the occurrence of angiosperm derived dammar resins from early paleogene sediments of india dutta et al 2009 rust et al 2010 the present study suggests that the early paleogene resins of the equatorial rainforests were not always represented by the dammar resins derived from dipterocarpaceae a family of angiosperm some of them were also contributed by the conifers

terpenoid composition and botanical affinity of cretaceous resins from india and myanmar abstract fossil resins from the cretaceous sediments of meghalaya india and kachin myanmar burma were analysed using curie point pyrolysis gas chromatography mass spectrometry and thermochemolysis gas chromatography mass spectrometry to help elucidate their botanical source the major pyrolysis products and methyl esterified thermochemolysis products of both the resins were abietane and labdane type diterpenoids with minor amount of sesquiterpenoids the thermochemolysis products also included methyl 16 17 dinor callitrisate methyl 16 17 dinor dehydroabietate and methyl 8 pimaren 18 oate the latter two from just the myanmarese resin the exclusive presence of both labdane and abietane diterpenoids and the lack of phenolic terpenoids may suggest that the studied cretaceous resins were derived from pinaceae pine family conifers

comparison of organic geochemistry and metal enrichment in two black shales cambrian alum shale of sweden and devonian chattanooga shale of united states in most black shales such as the chattanooga shale and related shales of the eastern interior united states increased metal and metalloid contents are generally related to increased organic carbon content decreased sedimentation rate organic matter type or position in the basin in areas where the stratigraphic equivalents of the chattanooga shale are deeply buried and and the organic material is thermally mature metal contents are essentially the same as in unheated areas and correlate with organic c or s contents this paradigm does not hold for the cambrian alum shale formation of sweden where increased metal content does not necessarily correlate with organic matter content nor is metal enrichment necessarily related to land derived humic material because this organic matter is all of marine source in southcentral sweden the elements u mo v ni zn cd and pb are all enriched relative to average black shales but only u and mo correlate to organic matter content tectonically disturbed and metamorphosed allochthonous samples of alum shale on the caledonian front in western sweden have even higher amounts for some metals v ni zn and ba relative to the autochthonous shales in this area and those in southern sweden

geochemical relationships of late paleozoic carbon rich shales of the midcontinent usa a compendium of results advocating changeable geochemical conditions abstract previous studies have shown that pennsylvanian black shales of the midcontinent us possess a more complex geochemical history than was once thought vine and tourtelot econ geol 65 1970 253 and coveney and glascock appl geochem 4 1989 347 note that the widespread nature of metalliferous pennsylvanian black shales and the diverse geological environments across the midwestern us pose the likelihood that metals contained in the black shales are of complex origins detailed geochemical and statistical representations using characteristics of numerous black shale members have shown that water depth may not have been uniformly deep as previously inferred by numerous workers earlier suggestions that these black shales were associated exclusively with anoxic depositional conditions have been challenged by a more realistic theory of multifaceted fluctuating environmental conditions a wide range of major and trace element concentrations combined with widely varying characteristics and diverse types of organic matter indicate the presence of fluctuating geochemical settings the presumption is that numerous associated chemical reactions occurred syngenetically one geochemical index degree of pyritization dop suggests a dysaerobic to aerobic setting for many of the shales whereas some other geochemical proxies i e v v ni indicate punctuated episodes of bottom water anoxia schieber abstr programs geol soc am 33 6 2001 a102 notes that in some black shales pyrite enrichment due to intermittent organic reworking explains the high dop values once thought to equate with extreme euxinic depositional conditions it seems likely therefore that even during apparent euxinic periods as indicated by bulk geochemistry oxygen deprived events were apparently short lived the seemingly euxinic fingerprint as shown by geochemical characteristics may result through time averaging abstr programs geol soc am 33 6 2001 a102 of intermittent euxinic events providing a misleading indication of dominant euxinic conditions thus detailed microstratigraphic sampling is necessary to delineate short punctuated occurrences of intermittent sub oxic episodes the midcontinent pennsylvanian shales may reflect a complex array of bottom water oxygenation variations and water depth fluctuations in response to climatic and localized events hatch j r and leventhal j s 1992 relationship between inferred redox potential of the depositional environment and geochemistry of the upper pennsylvanian missourian stark shale member of the dennis limestone wabaunsee county kansas usa in meyers p a pratt l m nagy b eds geochemistry of metalliferous black shales chem geol 99 65 82 complicated by post depositional events appl geochem 4 1989 347 this research examines the previous exclusively anoxic origin for midcontinent pennsylvanian black shales from a geochemical perspective and offers an alternative supported by detailed statistical presentations with the hypothesis that events of anoxia were punctuated by short lived dysaerobic or even near oxic events

depth dependence of earthquake frequency magnitude distributions in california implications for rupture initiation statistics of earthquakes in california show linear frequency magnitude relationships in the range of m2 0 to m5 5 for various data sets assuming gutenberg richter distributions there is a systematic decrease in b value with increasing depth of earthquakes we find consistent results for various data sets from northern and southern california that both include and exclude the larger aftershock sequences we suggest that at shallow depth 0 to 6 km conditions with more heterogeneous material properties and lower lithospheric stress prevail rupture initiations are more likely to stop before growing into large earthquakes producing relatively more smaller earthquakes and consequently higher b values these ideas help to explain the depth dependent observations of foreshocks in the western united states the higher occurrence rate of foreshocks preceding shallow earthquakes can be interpreted in terms of rupture initiations that are stopped before growing into the mainshock at greater depth 9 15 km any rupture initiation is more likely to continue growing into a larger event so there are fewer foreshocks if one assumes that frequency magnitude statistics can be used to estimate probabilities of a small rupture initiation growing into a larger earthquake then a small m2 rupture initiation at 9 to 12 km depth is 18 times more likely to grow into a m5 5 or larger event compared to the same small rupture initiation at 0 to 3 km

a review of the origins of metal rich pennsylvanian black shales central u s a with an inferred role for basinal brines abstract compared to most shales even most black shales numerous thin pennsylvanian marine black shales of the u s midwest are very enriched in organic c 5 40wt and heavy elements for example instrumental neutron activation analysis of 74 samples of mostly black and dark gray pennsylvanian shales of the u s midwest average 1300 ppm zn 85 ppm u 655 ppm mo 130 ppm se and 55 ppm cd amounts sufficient to raise concerns about heavy element pollution direct precipitation of sulfides and fixation by abundant organic matter during sedimentation and early diagenesis may account for heavy metals contained by shales in most cases metal supply calculations however indicate that a special source would be needed to supply metals for a strictly syngenetic origin possible sources for such metals include submarine hot springs and pennsylvanian seas that may have been more enriched in metals than modern ocean water at least at some localities additional metal values may have been added later from basinal brines e g zn or from modern groundwaters e g mo se u the actions of modern supergene processes may fix metals mitigating detrimental effects from black shales

a constitutive law for rate of earthquake production and its application to earthquake clustering seismicity is modeled as a sequence of earthquake nucleation events in which the distribution of initial conditions over the population of nucleation sources and stress ing history control the timing of earthquakes the model is implemented using solutions for nucleation of unstable fault slip on faults with experimentally derived rate and state dependent fault properties this yields a general state variable constitutive formulation for rate of earthquake production resulting from an applied stressing history to illustrate and test the model some characteristics of seismicity following a stress step have been explored it is proposed that various features of earthquake clustering arise from sensi tivity of nucleation times to the stress changes induced by prior earthquakes the model gives the characteristic omori aftershock decay law and interprets aftershock parameters in terms of stress change and stressing rate earthquake data appear to support a model prediction that aftershock duration defined as the time for rates to return to the back ground seismicity rate is proportional to mainshock recurrence time observed spatial and temporal clustering of earthquake pairs arises as a consequence of the spatial depen dence of stress changes of the first event of the pair and stress sensitive time dependent nucleation applications of the constitutive formulation are not restricted to the simple stress step models investigated here it may be applied to stressing histories of arbitrary complexity the apparent success at modeling clustering phenomena suggests the possibil ity of using the formulation to estimate short to intermediate term earthquake probabil ities following occurrence of other earthquakes and for inversion of temporal variations of earthquake rates for changes in driving stress

sesqui and diterpenoid biomarkers preserved in taxodium rich oligocene oxbow lake clays weisselster basin germany several diterpenoids of the abietane pimarane and phyllocladane type and three cadalanetype sesquiterpenoids have been identified in the organic solvent extracts of lower oligocene clay sediments haselbach strata saxony germany the sediment contains needles and cone scales of a fossil taxodium species which represents the only conifer in the samples a clear correlation between the observed conifer biomarkers and taxodium is evident apart from diterpenoids detected previously in other sediments a new diaromatic totarane diterpenoid is reported in isolated fossil and recent taxodium needles and cone scales as well as in the haselbach clays a phenolic diterpenoid of the abietane type ferruginol has been identified the results indicate that the taxodium rich clay samples contain several diterpenoids which so far have been used as biomarkers for other conifer families and thus the chemotaxonomical use of diterpenoid biomarkers for the differentiation of fossil conifer families has to be revised

vascular plant biomarkers as proxies for palaeoflora and palaeoclimatic changes at the dogger malm transition of the paris basin france abstract vascular plant biomarkers are used here as a chemostratigraphic tool for tracing both palaeoflora and palaeoclimatic changes during the callovian and oxfordian in the paris basin the retene cadalene ratio shows low values in claystones from the middle callovian to the end of the lower oxfordian then increases drastically from the end of the lower oxfordian cordatum zone synchronously with the progressive development of the oxfordian carbonate platform the relative proportion of retene a conifer biomarker is strongly correlated with the abundance of some of its diagenetic precursors and with saturated diterpanes some of these are very common and abundant in the pinaceae family while specific markers for non pinaceae conifers are not detected thus the increase in the retene cadalene ratio around the cordatum zone reflects the rising proportion of pinaceae on the london brabant massif which was the nearest land from the locations studied as pinaceae show many morphological adaptations to dry climate compared to the other plants reported in the jurassic taphofloras of the paris basin their increasing proportion indicates an increasing aridity this climatic change is also supported by published geochemical palaeobiogeographical palynological palaeobotanical and mineralogical data a comparable increase in the relative proportion of retene was also described for the oxfordian of western australia which could be an argument for a worldwide increase in aridity at the end of the lower oxfordian

amber inorganic geochemistry new insights into the environmental processes in a cretaceous forest of france amber fossils microorganisms arthropods and plant remains provide exceptionally well preserved data about past ecosystems but amber itself was rarely used as a paleoenvironmental tool here we present geochemical analyses of mid cretaceous amber of southwestern france that demonstrate the preservation of a primary inorganic geochemical signal especially the cretaceous ocean strontium isotopic ratio our results indicate that inorganic chemical analyses present a potential to uniquely document the paleoenvironmental conditions such as processes of water extraction of amber producing ecosystems

relationship between inferred redox potential of the depositional environment and geochemistry of the upper pennsylvanian missourian stark shale member of the dennis limestone wabaunsee county kansas u s a analyses of 21 samples collected from a core of the 52 8 cm thick stark shale member of the dennis limestone in wabaunsee county kansas demonstrate four cycles with two orders of magnitude variations in contents of cd mo p v and zn and order of magnitude variations in contents of organic carbon cr ni se and u the observed variability in amounts and or ratios of many metals and amounts and compositions of the organic matter appear related to the cause and degree of water column stratification and the resulting absence presence of dissolved o2 or h2s high cd mo u v zn and s contents a high degree of pyritization dop 0 75 0 88 and high high v v ni 0 84 0 89 indicate the presence of h2s in a strongly stratified water column intermediate contents of metals and s intermediate dop 0 67 0 75 and intermediate v v ni 054 0 82 indicate a less strongly stratified anoxic water column whereas low metal contents and low v v ni 0 46 0 60 indicate a weakly stratified dysoxic water column high p contents at the top of the organic matter rich intervals within the stark shale member indicate that phosphate precipitation was enhanced near the boundary between anoxic and dysoxic water compositions relatively abundant terrestrial organic matter in intervals deposited from the more strongly stratified h2s bearing water column indicates a combined halocline thermocline with the fresher near surface water the transport mode for the terrestrial organic matter the predominance of algal organic matter in intervals deposited from a less strongly stratified water column indicates the absence of the halocline and the presence of the more generally established thermocline relatively low amounts of degraded hydrogen poor organic matter characterize intervals deposited in a weakly stratified dysoxic water column the inferred variability in chemistry of the depositional environments may be related to climate variations and or minor changes in sea level during the general phase of deeper water deposition responsible for this widespread shale member

an integrated perspective of the continuum between earthquakes and slow slip phenomena slow slip a mechanism by which faults can relieve stress was thought to be distinct from earthquakes however a global review of slow slip phenomena suggests that instead there is a continuum between the two types of event

it s a matter of size magnitude and moment estimates for microseismic data microseismic mapping is a valuable tool for assessing hydraulic fracture stimulations during a stimulation treatment borehole near surface or surface geophones record passive seismic data the microseismic events are thought to be shear failures that occur around the opening of a tensile hydraulic fracture as it grows over the past several years there has been a large growth in the number of hydraulic fracture monitoring surveys along with the number of vendors who acquire and process microseismic data here we discuss two attributes of microseismic data which are associated with the size of the passive event seismic moment and magnitude