can biomass burning produce a globally significant carbon isotope excursion in the sedimentary record negative carbon isotope excursions have been comprehensively studied in the stratigraphic record but the discussion of causal mechanisms has largely overlooked the potential role of biomass burning the carbon isotopic ratios 13 c of vegetation soil organic matter and peat are significantly lower than atmospheric carbon dioxide co2 and thereby provide a source of low 13 c co2 when combusted in this study the potential role of biomass burning to generate negative carbon isotope excursions associated with greenhouse climates is modeled results indicate that major peat combustion sustained for 1000 yr increases atmospheric co2 from 2 5 present atmospheric levels pal to 4 6 pal and yields a pronounced negative 13 c excursion in the atmosphere 2 4 vegetation 2 4 and the surface ocean 1 2 but not for the deep ocean 0 9 release of co2 initiates a short term warming of the atmosphere up to 14 4 c with a duration of 1628 yr which is consistent with the magnitude and length of an observed toarcian excursion event these results indicate that peat combustion is a plausible mechanism for driving negative 13 c excursions in the rock record even during times of elevated pco2

the pre quaternary history of fire abstract although evidence for land vegetation comes from the silurian and maybe even earlier the first record of fossil charcoal fusain is from the late devonian for this period there are only one or two isolated records not until the early carboniferous is there a record of extensive charcoal deposits mainly preserved in near shore clastic sediments which provide evidence of significant and widespread wildfires by the late carboniferous charcoal was common or abundant in a wide range of facies including tropical wetland peats wildfire played an important role in shaping the environment at this time the latest palaeozoic and early mesozoic records of charcoal are fewer whereas important deposits of late mesozoic age are found worldwide the occurrence of charcoal at the cretaceous tertiary boundary has been highlighted as evidence for a global fire following a meteorite impact but this interpretation is questionable charcoal has been widely reported from tertiary sediments and its appearance in the quaternary and recent is not solely as a result of human impact through the past 400 million years there have been major changes in atmospheric oxygen levels that affected fire intensity and frequency fire systems thus have a long history and their impact on shaping the environment is assessed

mesozoic orogenic gold mineralization in the jiaodong peninsula china a focused event at 120 2 ma during cooling of pregold granite intrusions

analysis of gases in fossil amber fossilized tree resin commonly known as amber has long served as a robust source of paleobiologic information via the preservation of embalmed invertebrates another more radical idea is that gas bubbles enclosed in fossil amber may represent ancient air trapped at the time the original resin was exuded from its host tree alternatively gas trapped in ancient amber may instead represent contamination by modern air here we analyze gaseous inclusions from ambers sampled worldwide spanning the cretaceous eocene eocene oligocene eocene miocene u oligocene miocene and modern after careful consideration of a number of possible explanations we suggest the gas inclusions may represent at least in part ancient air

orogenic gold common or evolving fluid and metal sources through time abstract orogenic gold deposits of all ages from paleoarchean to tertiary show consistency in chemical composition they are the products of aqueous carbonic fluids with typically 5 20 mol co 2 although unmixing during extreme pressure fluctuation can lead to entrapment of much more co 2 rich fluid inclusions in some cases ore fluids are typically characterized by significant concentrations of ch 4 and or n 2 common estimates of 0 01 0 36 mol h 2 s a near neutral ph of 5 5 and salinities of 3 7 wt nacl equiv with na k ca mg this fluid composition consistency favors an ore fluid produced from a single source area and rules out mixing of fluids from multiple sources as significant in orogenic gold formation nevertheless there are broad ranges in more robust fluid inclusion trapping temperatures and pressures between deposits that support a model where this specific fluid may deposit ore over a broad window of upper to middle crustal depths much of the reported isotopic and noble gas data is inconsistent between deposits leading to the common equivocal interpretations from studies that have attempted to define fluid and metal source areas for various orogenic gold provinces fluid stable isotope values are commonly characterized by the following ranges 1 18 o for precambrian ores of 6 to 11 and for phanerozoic ores of 7 to 13 2 d and 34 s values that are extremely variable 3 13 c values that range from 11 to 2 and 4 15 n of 10 to 24 for the neoarchean 6 5 to 12 for the paleoproterozoic and 1 5 to 10 for the phanerozoic secular variations in large scale earth processes appear to best explain some of the broad ranges in the o s and n data fluid rock interaction particularly in ore trap areas may cause important local shifts in the o s and c ratios the extreme variations in d mainly reflect measurements of hydrogen isotopes by bulk extraction of waters from numerous fluid inclusion generations many which are not related to ore formation radiogenic isotopes such as those of pb sr nd sm and os measured on hydrothermal minerals are even more difficult to interpret for defining metal source particularly as the low salinity ore fluids transport limited amounts of these elements and significant amounts of these may be locally added to the minerals during alteration reactions at the sites of gold deposition noble gas and halogen data are equally equivocal fluid exsolution from granitoids emplaced into the upper and middle crust metamorphism of the crust or fluids entering trans crustal fault zones from below the crust all remain as permissive scenarios associated with orogenic gold formation as the abundant geochemical data are equivocal however geological and geochronological data weigh heavily against a magmatic hydrothermal model in the upper to middle crust there is no universal temporal association between orogenic gold and magmatism and where there is an overlap in age there is no specific type of magmatism consistently associated with gold formation nor element zonation around any specific pluton a crustal metamorphic model for fluid and metal sources is very consistent with geological geochronological and geochemical data although metamorphism on a regional scale that releases these components into major fault zones can be associated with many processes along active continental margins these can include crustal thickening and radiogenic heating slab rollback and heating during crustal extension or subduction of a spreading ridge heating the base of an accretionary prism in rare examples where phanerozoic orogenic gold deposits are hosted in precambrian high grade metamorphic terranes fluids and metals must however enter a transcrustal fault system from a sub crustal source this could either be a devolatilized subducted relatively flat perhaps stalled slab and its overlying sediment or the corner of the fertilized mantle wedge that releases a fluid during a thermal event

sedimentary organic matter and δ13ckerogen variation on the southern iberian palaeomargin betic cordillera se spain during the latest pliensbachian early toarcian abstract the early toarcian oceanic anoxic event t oae is characterised by major palaeoenvironmental and palaeoceanographical changes ocean anoxia global warming ocean acidification among other and a severe perturbation of the global carbon cycle although widespread oceanic anoxia was a significant control on the occurrence of organic rich facies during the t oae in several locations of the northern tethyan margin the effects of anoxia oceanic productivity and dilution are poorly understood in other worldwide locations such as the southern tethyan and iberian margins in this study we report new geochemical total organic carbon toc total sulphur ts total carbonate content caco3 13c from kerogen isolates 13ckerogen palynofacies and thermal maturation data from the upper pliensbachian lower toarcian successions in la cerradura and fuente vidriera external subbetic domain betic cordillera se spain the obtained results indicate that these successions have low toc contents 0 3 wt with toc reaching up to 0 46 wt around the polymorphum serpentinum ammonite zone boundary in la cerradura 13ckerogen negative carbon isotope excursions cie are observed at the base of the polymorphum zone the pliensbachian toarcian event pl toa and base of the serpentinum zone t oae overall the low maturity kerogen assemblages are dominated by terrestrial om and with a minor marine component small increments in terrestrial om non opaque phytoclasts and palynomorphs are observed just before and during the t oae in the studied area during the early toarcian in the external subbetic domain accumulation and preservation of om was low and with a significant terrestrial contribution similarly to other locations around the southern margins of iberia and tethys the dominance of the opaque phytoclast subgroup the occurrence of classopollis and the relatively more positive 13c of terrestrial kerogen suggest that om was mostly sourced from an area characterised by a semi arid climate i e with pronounced arid periods during most of the polymorphum zone the t oae negative cie is accompanied by an increase in terrestrial om with a slight increase in the non opaque phytoclast subgroup and terrestrial palynomorph subgroup the increase of non opaque phytoclast and terrestrial palynomorphs are in line with the posited enhancements of the hydrological cycle and export of terrestrial om into marine environments during the t oae this study suggests a link between 13c fractionation during photosynthesis in c3 plants and climate during the early toarcian this link suggests coupling of the water and terrestrial carbon cycles before and during the t oae

late triassic charcoal from petrified forest national park arizona usa fossil charcoal has been found in the late triassic chinle formation in petrified forest national park a location that is world famous for its silicified tree trunks the material consists of charcoalified secondary wood and has sufficiently well preserved plant anatomy to show it may be described as araucarian type although it does display some minor differences from the anatomies described for the silicified gymnosperm trunks in the park the presence of the charcoal proves that on occasion natural wildfires most probably ignited by lightning must have occurred in the chinle triassic palaeoenvironments with resulting impacts on the biota of those times it is currently impossible to estimate how often these fires occurred as the incidence of charcoal here and in the whole fossil record apart from the frequency of ancient fires also reflects the preservation and burial conditions of the material there is scant mention of triassic charcoal in the literature a notable absence given the abundance of charcoal that has been recorded in the carboniferous jurassic and cretaceous periods this lack of charcoal may support the theory that atmospheric oxygen levels were lower during the triassic than in the carboniferous

water column euxinia and wildfire evidence during deposition of the upper famennian hangenberg event horizon from the holy cross mountains central poland a palynological study of the uppermost famennian section from kowala quarry holy cross mountains central poland allowed recognition of two miospore zones lv retispora lepidophyta apiculiretusispora verrucosa and ln retispora lepidophyta verrucosisporites nitidus based on palynology and sedimentology the black shale within the upper part of the section is identified as equivalent to the hangenberg black shale which is known globally this black shale contains compounds characteristic of photic zone euxinia including isorenieratane and its derivatives such compounds are absent in the organic poor marls and shales occurring below the ln zone and are present only as traces in the layers just above the black shale indicating fluctuations in the oxygen minimum zone during uppermost famennian sedimentation palynofacies show high amounts of amorphous organic matter and prasinophyte concentrations in the black shale and a subsequent significant decrease of amorphous organic matter concomitant with a rapid increase of terrestrial input mainly miospores with common tetrads in the layers above the black shale this supports the relatively rapid change in the taxonomic composition of phytoplankton caused by fluctuations of the chemocline the whole succession corresponds to one sea level rise and fall the presence of high concentrations of peri condensed polycyclic aromatic hydrocarbons and large amounts of small charcoal particles at the hangenberg event horizon indicate the occurrence of wildfires such observations suggest that atmospheric o2 levels had exceeded the critical threshold of 13 above which wildfires may occur by latest famennian time

the sukhothai zone permian triassic island arc domain of southeast asia in northern laos insights from triassic carbonates and foraminifers abstract in mainland southeast asia permian triassic successive subduction of the paleo tethyan oceanic lithosphere formed an island arc system called the sukhothai zone along the margin of the indochina block this zone has been considered to extend from northern thailand to southwestern yunnan of china but so far lacked concrete evidence from northern laos in between this makes basic geotectonic subdivision of mainland southeast asia ambiguous in this study triassic foraminifers from limestone distributed in the long area of luang namtha province northwestern laos solve this problem the relevant limestone has a kilometer sized extent and was previously assigned to the carboniferous early permian based only on lithological grounds in regional geological mapping its triassic age is demonstrated for the first time based on foraminifers we discriminated from this limestone aulotortus sinuosus a tumidus ophthalmidium danneri endotriada tyrrhenica endoteba obturata endotebanella kocaeliensis diplotremina astrofimbriata duostomina biconvexa and palaeolituonella majzoni and concluded that the fauna is referable to the carnian early late triassic cement rich reefal sediments consisting of carniphytes multisiphonatus microbial boundstone and sparse allochem bioclastic grainstone containing abundant fragments of plexoramea gracilis are common in this limestone they suggest open marine sedimentation on a shallow carbonate platform possibly comparable to a cement dominated upper slope tubiphytes reef environment found elsewhere in the triassic in neighboring mainland thailand carnian limestone with similar lithological and paleontological properties is found only in the doi long formation distributed in the sukhothai zone this evidence provides a firm basis for the tectonostratigraphic correlation of the sukhothai zone in northern laos consequently our study is critical in giving a clue to clarify the distribution and extension in northern laos of a permian triassic island arc domain the sukhothai zone which is one of the major tectonostratigraphic units comprising mainland southeast asia in this paper we also described two encrusting foraminifers having multi chambered septate shells which have been seldom documented in triassic foraminiferal literature

observations on the nature and origin of fusain abstract evidence for a wildfire origin of fusain is examined charcoal produced by natural fires and artificial charring resembles fossil fusain both in physical size and shape and in optical reflectance artificially charred leaves and naturally burnt wood are illustrated using the sem reflectance studies on modern charcoals suggest that much semifusinite may be produced by pyrolysis the ecological implications of a wildfire origin of fusain are discussed and it is concluded that fires have been a feature of terrestrial ecosystems from at least the late devonian

from intrusion related to orogenic mineralization the wasamac deposit abitibi greenstone belt canada abstract the wasamac deposit is an example of archean greenstone hosted gold deposit located in the abitibi belt 15 km southwest of rouyn noranda the deposit is hosted by a second order ductile shear zone of the cadillac larder lake fault zone cllfz known as the francoeur wasa shear zone fwsz it regionally sits at the boundary between the orogenic gold district of noranda and the kirkland lake gold district dominated by intrusion related gold systems this specific location in between two different gold mineralization environments sets the wasamac deposit apart as a prime candidate for investigating hydrothermal processes along the cllfz within the wasamac deposit gold distribution is constrained to the altered mylonitized portion of the fwsz lode systems are absent hydrothermal alteration and associated disseminated mineralization occurs as a replacement of the blake river group metavolcanic units the hydrothermal signature displays two distinct alkaline alteration assemblages potassic and albitic each associated with specific gold characteristics 1 potassic alteration is characterized by the crystallization of microcline carbonates and quartz within this assemblage gold is associated with porous pyrite enriched in te ag au mo pb bi w deposited under oxidizing conditions such characteristics are widely described in the kirkland lake area and are found in examples of syenite related mineralization such as the beattie and malartic gold deposits 2 the albitic alteration assemblage composed of albite sericite and carbonates reflects more reduced hydrothermal conditions with mineralization characterized by free native gold this hydrothermal event is coeval with the brecciation of early gold rich pyrite reflecting a structural overprint that controlled late stage gold characteristics these alteration and structural features are common in orogenic gold deposits both worldwide and regionally particularly at the neighbouring kerr addison and francoeur deposits and in lode gold systems such as in the sigma lamaque deposit the gold mineralization at wasamac has similar characteristics to both intrusion related gold systems and structurally controlled orogenic gold deposits hydrothermal and structural crosscutting relationships at wasamac indicate that a structurally controlled hydrothermal event overprinted earlier potassic magmatic hydrothermal alteration this observation supports a multistage process of gold concentration during which new gold characteristics metal anomalies fluid conditions and alteration assemblages replaced earlier stages of gold enrichment in places completely obliterating previous signatures we propose that the wasamac deposit was originally related to an alkaline intrusion buried at depth beneath the francoeur wasa shear zone

wildfires and seasonal aridity recorded in late cretaceous strata from south eastern arizona usa lithostratigraphic and organic chemostratigraphic studies of fluvial lacustrine sediments in the late cretaceous fort crittenden formation in south eastern arizona usa reveal changes in palaeoclimate and tectonics as well as associated fluctuations in lake level the lower fort crittenden is dominated by marginal wetland to deep water lake deposits whereas the upper fort crittenden is characterized by wetland to deltaic deposits abundance of polycyclic aromatic hydrocarbons pah and reflectance of fusinite substantiate the impact of wildfires within the watershed organic geochemical evidence of wildfires is linked with sedimentological indicators of seasonal aridity suggesting that wildfires were common occurrences sedimentological evidence for seasonal aridity includes mottles and pseudoslickensides on ped structures within wetland mudstones distinct variations in pah assemblages characterized by the number of aromatic rings indicate that there were variations in the intensities of wildfires assuming no variations in the types of fuel fusinite reflectance values are consistent with combustion temperatures from 470 to 550 c observed in modern wildfires

the impacts of land plant evolution on earth s climate and oxygenation state an interdisciplinary review abstract the paleozoic emergence of terrestrial plants has been linked to a stepwise increase in earth s o2 levels and a cooling of earth s climate by drawdown of atmospheric co2 vegetation affects the earth s o2 and co2 levels in multiple ways including preferential organic carbon preservation by decay resistant biopolymers e g lignin and changing the continental weathering regime that governs oceanic nutrient supply and marine biological production over shorter time scales 1 myr land plant evolution is hypothesized to have occasionally enhanced p weathering and fertilized the oceans expanding marine anoxia and causing marine extinctions oceanic anoxia would eventually become limited by oceanic o2 uptake as oxygen accumulates in the atmosphere and surface oceans when excess organic carbon is buried in marine sediments here we review hypotheses and evidence for how the evolving terrestrial ecosystems impacted atmospheric and oceanic o2 and co2 from the ordovician and into the carboniferous 485 298 9 ma five major ecological stages in the terrestrial realm occurred during the prolonged time interval when land was colonized by plants animals and fungi marked by the evolution of 1 non vascular plants 2 vascular plants with lignified tissue 3 plants with shallow roots 4 arborescent and perennial vegetation with deep and complex root systems and 5 seed plants the prediction that land vegetation profoundly impacted the earth system is justified although it is still debated how the individual transitions affected the earth s o2 and co2 levels the geological record preserves multiple lines of indirect evidence for environmental transitions that can help us to reconstruct and quantify global controls on earth s oxygenation and climate state

a regional scale discontinuity in western sicily revealed by a multidisciplinary approach a new piece for understanding the geodynamic puzzle of the southern mediterranean the results of an integrated stratigraphic structural geophysical and geochemical study reveal the presence of a crustal discontinuity in western sicily that at present runs roughly n s along a band from san vito lo capo to sciacca svcs the boundary between the two zones of this discontinuity is nearly orthogonal to the main thrust propagation of the sicilian thrust and fold belt the different permian to tertiary sedimentary evolution recorded by the two zones appears related to this discontinuity with thick carbonate platforms in the western sector facing deep water successions in the eastern one the presence of upper triassic reefs huge megabreccias bodies and widespread submarine volcanisms along the transition zone suggest the presence of a long lasting weakness zone this zone has been reactivated episodically as transpressional and or transtensional faults in relation to the different geodynamic stress acting in central mediterranean area in different epochs we speculate that this transition zone has represented a segment of the passive margin of the ionian tethys during the maghrebian convergence a different style of deformation has affected the two sectors floored by different sedimentary multilayers the orthogonal to oblique differential convergence between the two sectors has resulted in right lateral transpressional motions leading to oblique thrusting of deep water derived thrusts onto platform derived thrusts associated with clockwise rotations the oblique convergence is still ongoing as demonstrated by the seismicity of the area by the geothermal field with high mantle derived helium fluxes and by the gps measurements collected by different authors

atmospheric gas in modern and ancient halite fluid inclusions a screening protocol abstract halite possesses great potential for hosting and storing information vital to the reconstruction of earth s ancient climate seawater chemistry and evolving atmosphere here we propose a screening protocol that not only distinguishes between primary and secondary halite but also identifies fluid inclusions that carry original gas trapped during the primary crystallization process an integrated multi analytical protocol is presented for sample preparation petrographic evaluation analytical measurements and distinguishing original gases and contents from contaminants the screening protocol starts with the visual inspection of halite for primary chevron and hopper features and or milky appearance then petrography is used to distinguish between primary and secondary diagenetic crystal fabrics and inclusions the trace element and isotope geochemistry speak directly to the composition of the depositional and or diagenetic fluids and to the formation in marine non marine or diagenetic settings furthermore rare earth elements and redox sensitive elements may address the redox conditions of the salt pan flat brines whereas microthermometry helps characterize the depositional diagenetic environment s temperature finally gas extracted by quadrupole mass spectrometer from gas bubbles in fluid inclusions is screened with concomitant ch4 co2 and ar contents to distinguish and quantify organic matter decomposition contributions and with 40ar 36ar to monitor modern atmospheric gas diffusion leakage issues and thus contamination of the primary gas contents our test case shows that halite collected from cores is well suited in maintaining its original mineralogical texture chemistry and gas content our integrated screening protocol suggests that the 815 myr old halite from the tonian browne formation of the officer basin australia formed under atmospheric conditions of about 10 9 po2 back calculation or 9 6 po2 mean calculation the coeval neoproterozoic gypsum collected in outcrop from minto inlet victoria island canada underwent some mineralogical alteration however experiments suggest that depositional gypsum from outcrop core may have potential of retaining vestiges of original gas in fluid inclusions

global fire at the cretaceous tertiary boundary cretaceous tertiary k t boundary clays from five sites in europe and new zealand are 102 104 fold enriched in elemental c mainly soot which is isotopically uniform and apparently comes from a single global fire the soot layer coincides with the ir layer suggesting that the fire was triggered by meteorite impact and began before the ejecta had settled

submarine cementation in a high energy platform reef one tree reef southern great barrier reef three major framework facies algal pavement coral heads and branching corals show varying degrees of cementation the widest distribution and greatest variety of submarine cements occur within those facies or subfacies that have extensive encrustation by coralline algae these are found beneath the windward margin and within the patch reef drilled both mg calcite and aragonite cements exhibit diverse fabrics and textures mg calcite in the dominant cement and is present as both an interskeletal and intraskeletal infill whereas aragonite cement is exclusively intraskeletal interskeletal cements are only developed within those facies capable of trapping significant quantities of fine grained internal sediment lithified crusts with either a laminated or columnar morphology are a prominent cavity infill within many of the reef framework facies organic influence during formation peloids which are the major component of the lithified crusts as well as many other cavity infillings are a particular form of mg calcite micrite and have nucleated within the interstitial waters of the reef microcrystalline rim cements around the peloids have often cemented them into a coherent mass that resembles detrital lime mudstones modified journal abstract

gas bubbles in fossil amber as possible indicators of the major gas composition of ancient air gases trapped in miocene to upper cretaceous amber were released by gently crushing the amber under vacuum and were analyzed by quadrupole mass spectrometry after discounting the possibility that the major gases n2 o2 and co2 underwent appreciable diffusion and diagenetic exchange with their surroundings or reaction with the amber it has been concluded that in primary bubbles gas released during initial breakage these gases represent mainly original ancient air modified by the aerobic respiration of microorganisms values of n2 co2 o2 for each time period give consistent results despite varying o2 co2 ratios that presumably were due to varying degrees of respiration this allows calculation of original oxygen concentrations which on the basis of these preliminary results appear to have changed from greater than 30 percent o2 during one part of the late cretaceous between 75 and 95 million years ago to 21 percent during the eocene oligocene and for present day samples with possibly lower values during the oligocene early miocene variable o2 levels over time in general confirm theoretical isotope mass balance calculations and suggest that the atmosphere has evolved over phanerozoic time

depth transect of an upper triassic rhaetian reef from gosau austria microfacies and community ecology abstract in the late triassic 235 201 3 ma scleractinian corals and hypercalcified sponges built large diverse reef ecosystems the most famous of which are the dachstein reefs this study presents a depth transect along an upper triassic lower rhaetian dachstein reef from the gosausee margin of the dachsteingebirge gosau austria the gosausee microbial sponge coral reef is a complete barrier reef with an almost continuous fore reef to lagoon transect preserved a very rare occurrence for the triassic and thus provides a window into depth zonation of dachstein type reef facies and biotic succession the gosausee reef facies exhibit strong depth control and five classic reef facies or zones are identified the fore reef reef front reef crest back reef and lagoon facies thin rare microbial fabrics and a high abundance of fine grained mud rich skeletal wackestones transported reef debris characterize the deepest fore reef as the reef shallows muddy sediments decrease in abundance and are replaced by microbial fabrics corals and cements abundant sponges microbial crusts and thick marine cements typify the reef crest whereas microbialite coated phaceloid corals are dominant in the back reef facies heavily cemented oncoids or microbial sponge bindstones are characteristic of the lagoon based on their compositional and biotic similarities the gosausee reef was likely part of the same barrier reef systems as the source reef for the gosaukamm reef breccia one of the classic norian rhaetian dachstein reefs the reef zones of the gosausee margin can be used to interpret the depth or reef zone of less well preserved reef fragments can inform models of community ecology and niche utilization in the late triassic and highlight the need for additional research into the environmental factors that controlled biotic distribution in upper triassic reefs

platy coral patch reefs from eastern panthalassa nevada usa unique reef construction in the late triassic abstract upper triassic lower norian reefal buildups near mina nevada represent some of the earliest scleractinian coral reefs from eastern panthalassa the small patch reefs 20 40 m high and 50 150 m wide obvious metre scale elevation above the surrounding sediments are from the luning allochthon and grew on an inner to middle ramp or in a deep lagoon the mina patch reefs were constructed by several different coral ecomorphotypes platy tabular domal massive and branching corals interpreted to have had zooxanthellate symbionts and record subtle coral zonation within the reefs based on modern coral ecomorphotypes platy to tabular corals at mina grew in the lower euphotic zone stressed by low light conditions and the massive or domal corals inhabited shallower water possibly above fair weather wave base and were stressed by wave energy unlike most other late triassic reef ecosystems where phaceloid branching corals or calcareous sponges constitute the principal bioconstructors the platy to tabular corals were the primary builders in the mina patch reefs the mina reefs are also unique because cryptic and cavernous internal environments epibionts cryptobionts and thick microbial crusts are rare or absent the combination of platy coral dominance with the lack of epibionts cryptobionts microbial crusts suggests that the norian reefs from mina nevada represent a unique form of scleractinian reef construction from the late triassic

new metallogenic model of telescoped eocene miocene au u epithermal mineral deposit in the placer de guadalupe district chihuahua mexico abstract the chronological repartition of mineral deposits in mexico and the southern usa coincides with the distribution of the three main volcanic pulses of the sierra madre occidental these pulses are eocene to early miocene in age suggesting that a broad migration occurred from northwest to southeast where the last ignimbrite flare up occurred the most fertile event occurred from 36 to 28 ma and produced all of the largest ag au mining districts the placer de guadalupe au u district contain a unique association of metals with high variations in their u au ratios that are not common worldwide the uraninite population dated by wells 1930 yielded an age of ca 36 ma which is comparable to that of the volcanic intrusions and dykes dated in the district yielding ages of ca 36 ma altered uraninite cemented by gold sheets provide an age of 21 ma which is interpreted to be the age of the gold epithermal event studies of fluid inclusions in the quartz and calcite cements formed in the gold event indicate the presence of immiscible magmatic brines and co2 homogenization temperatures by halite melting range from 268 c to 305 c and 266 6 c to 283 c with salinities ranging from 35 9 to 38 9 and 36 0 to 37 5 wt eq nacl in the quartz and calcite stages respectively c o isotopic compositions of u and au calcite cements suggest a trend of low temperature alteration caused by hydrothermal fluids these c o isotopes suggest that during the gold event water rock interaction processes occurred between magmatic fluids and the carbonate host rock ree enrichment in the u calcite cement suggests that la ce enriched carbonatite volcanic formations participated in the mineralizing process the u mineralization event was controlled by 1 a metal and heat source in this case late eocene volcanism and in particular a carbonatite volcanic event 2 an efficient transport mechanism for the large scale input of meteoric water which was channeled heated and u enriched into reactivated crustal eocene faults from a deep u source to a shallow sedimentary chemical trap 3 an effective trap which is represented in this study by the presence of an organic matter rich sedimentary formation the gold mineralization event was characterized by the miocene extensional peak coupled with asthenospheric upwelling which facilitated the melting metamorphism of the lower crust and the expulsion and transport of large amounts of co2 bearing fluids to a shallow crustal level through the reactivated crustal laramide thrust faults the fluids interactions with the entire stratigraphic column from the grenvillian to the late triassic basement favored the leaching of gold and the enrichment of co2 bearing fluids gold deposition appears to be related to boiling but was ultimately favored by water rock interaction with u mineralization and the upper plomosas shale study of the au u placer de guadalupe deposit reveals evidence of a new miocene metallogenic event in central and northern mexico its genetic relationship with the basin and range bnr and rio gande rift rgr in usa and its transition from post orogenic to miocene intraplate extension in mexico provides a new perspective regarding the exploration of miocene gold epithermal deposits in northern mexico and the southern usa

the climatic significance of late ordovician early silurian black shales the ordovician silurian transition approximate to 455 430ma is characterized by repeated climatic perturbations concomitant with major changes in the global oceanic redox state best exemplified by the periodic deposition of black shales the relationship between the climatic evolution and the oceanic redox cycles however remains largely debated here using an ocean atmosphere general circulation model accounting for ocean biogeochemistry mitgcm we investigate the mechanisms responsible for the burial of organic carbon immediately before during and right after the latest ordovician hirnantian 445 444ma glacial peak our results are compared with recent sedimentological and geochemical data we show that the late katian time slice approximate to 445ma typified by the deposition of black shales at tropical latitudes represents an unperturbed oceanic state with regional organic carbon burial driven by the surface primary productivity during the hirnantian our experiments predict a global oxygenation event in agreement with the disappearance of the black shales in the sedimentary record this suggests that deep water burial of organic matter may not be a tenable triggering factor for the positive carbon excursion reported at that time our simulations indicate that the perturbation of the ocean circulation induced by the release of freshwater in the context of the post hirnantian deglaciation does not sustain over sufficiently long geological periods to cause the rhuddanian approximate to 444ma oceanic anoxic event input of nutrients to the ocean through increased continental weathering and the leaching of newly exposed glaciogenic sediments may instead constitute the dominant control on the spread of anoxia in the early silurian

paleoecology of the fire clay coal bed in a portion of the eastern kentucky coal field vertically continuous increment samples of the fire clay coal bed mid middle pennsylvanian late westphalian b collected from a portion of the central appalachian basin were studied palynologically petrographically and geochemically in order to partially reconstruct the paleoecology and processes associated with peat formation in the ancient fire clay paleomire results indicate that four compositional groups can be identified they are 1 a lycospora vitrinite dominant group characterized by high percentages of lycospora and vitrinite macerals and generally low but variable ash yields and sulfur contents 2 a mixed palynoflora high vitrinite group that petrographically is similar to group 1 except that it contains a more diverse palynoflora 3 a mixed palynoflora moderate low vitrinite group characterized by various admixtures of lycopsid fern and calamite miospores increased percentages of liptinite and inertinite macerals and low ash yields and sulfur contents and 4 a mixed palynoflora high ash yield group characterized by high percentages of small lycopsid fern and occasionally calamite and cordaite miospores high liptinite and inertinite contents high ash yields and moderate to high sulfur contents the fire clay coal bed contains a distinctive flint clay parting of probable volcanic origin that naturally divides the bed into two benches these two benches upper and lower are highly disparte in occurrence appearance and composition in the study area the lower bench generally is thin 0 5 m laterally discontinuous and mainly composed of dull mainly durain coal lithotypes ash yields typically are high sulfur contents generally are moderate to high compositional group 4 the mixed palynoflora high ash yield group defines all of the increments examined from the lower bench in contrast the upper bench is thick 0 75 m laterally continous and mainly comprised of bright mainly clarain coal lithotypes overall ash yields and sulfur contents for this bench are generally low although vertical variation is apparent all of the compositional groups occur in the upper bench in some columns notably those that are thick and uninterrupted by clastic partings groups 1 and 4 often occupy basal coal layers and groups 2 and 3 occur in higher layers other columns especially those taken in areas of thin 0 5 m fire clay coal are dominated by groups 1 and 4

fingerprinting multiple gold mineralization events at the dome mine in timmins ontario canada trace element and gold content of pyrite abstract the dome mine is host to over 16 moz of orogenic gold deposited during a period of up to 25 ma through multi stage enrichment the earliest economic stage of veining is an extensive set of ankerite veins which were historically considered barren except where overprinted by subsequent veining events gold in these veins is intimately associated with pyrite mineralization and three stages of pyrite growth have been identified py1 2 3 the trace element content of each stage of pyrite growth determined by dynamic secondary ion mass spectrometry and synchrotron radiation x ray fluorescence reveals that there were three auriferous fluid events each with a unique gold and trace element fingerprint which can be related to deposits wide mineralization events early ankerite vein forming fluids were auriferous lower temperature 200 250 c and deposited py1 enriched in gold metals and metalloids as cu ni zn py2 growth is related to deposit wide quartz tourmaline and quartz fuchsite veining based on trace element geochemistry au ag and associated mineral assemblages this deposited ni enriched pyrite tellurides galena and gold with anomalously high au ag ratios there is also evidence for remobilization of early gold and trace elements from py1 pyrite during the py2 forming event the final stage of gold endowment in the ankerite veins is related to a deposit and camp wide quartz veining event py3 growth is trace element as ni cu and au poor with respect to py1 and py2 however this veining event contributed the bulk of the ankerite vein gold endowment the remobilization of gold and trace elements from sieve textured py1 in addition to overprinting py2 and py3 and their associated gold endowments helps explain the difficulty in applying bulk rock trace element vectors to gold at the dome mine the work also provides conclusive evidence for the auriferous nature of early ankerite veining at the dome mine and reveals that the system was fertile for a period of over 7 to 25 ma a key component for the formation of a world class deposit

timing of triassic tectonic division and postcollisional extension in the eastern part of the jiaodong peninsula abstract the jiaodong peninsula is a key region for researching the interaction between the north and south china plates tectonic relationships between collision exhumation of ultra high pressure uhp slabs strike slip faulting and gold mineralization are still ambiguous the eastern part of the jiaodong peninsula eastern jiaodong which includes triassic intrusions and is less affected by the tan lu fault zone is a key area to examine exhumation dynamics in detail systematic field mapping and zircon u pb dating of triassic intrusions establishes that 1 the uhp wedge in the eastern part of the jiaodong peninsula can be divided into the lateral and frontal ramps of a thrust and nappe system dating of samples from donglinghou 244 7 4 2 ma and qingyutan 233 8 8 1 ma areas indicates that the collision happened at or before the middle triassic 2 postcollisional extension intrusions including the shidao granitoid 216 2 2 4 ma and the chengshantou granitoid cut by a dolerite dyke dated at 210 5 1 0 ma generally strike ne and occurred in a metamorphic core complex below the upper jiashan xiangshui detachment u jsxs 3 regional faults in the jiaodong peninsula exploited syncollisional foliations of the uhp wedge which resulted in faults dipping towards the nw and se the reactivation of the lower jiashan xiangshui shear zone l jsxs and its overprinting upon the tan lu fault system may have caused another major episode of exhumation of the syncollisional wedge and could have been responsible for an extensional environment that favored gold mineralization

charcoal recognition taphonomy and uses in palaeoenvironmental analysis abstract charcoal predominantly the product of wildfires is abundant in many sedimentary rocks deposited in a wide range of environments from terrestrial to marine it also occurs in some volcanic rocks this paper outlines aspects of charcoal formation both natural and experimental and briefly considers the taphonomic processes leading to a final assemblage this is done using examples from recent fires and through experimentation the ways in which charcoal assemblages are recognized in the field and extraction in the laboratory are also considered methods of charcoal identification are presented the range of charcoalified plant organs that can be found is discussed and a wide range of study methods outlined including light microscopy dark field light microscopy reflectance microscopy scanning electron microscopy and synchrotron radiation x ray tomographic microscopy emphasis in this paper is on the study of macro and meso charcoal above180 m finally there is a consideration of the broad use of charcoal from plant evolution studies fire history studies vegetation studies anatomical studies climate and atmospheric studies and the wider importance of charcoal for the earth and biological sciences charcoal is information rich but yet is an under utilized resource

maturity estimation of phytoclasts in strew mounts by micro raman spectroscopy abstract in order to evaluate the potential for petroleum generation of a sedimentary rock it is important to establish the thermal maturity of its organic matter in rocks with low total organic carbon the kerogen has to be isolated by acid maceration and the traditional maturity assessment via vitrinite reflectance is sometimes hampered by the small amount of vitrinite exposed on polished plugs this study presents an additional route of maturity estimation via raman spectroscopy that is advantageous especially when only a small amount of vitrinite is available previous studies for maturation assessment based on raman spectroscopy were mostly carried out on organic rich rocks prepared as whole rock blocks in this work we developed a maturity assessment based on raman spectra obtained on isolated kerogen dispersed on strew mounts as prepared for palynofacies analysis and spore coloration index rendering additional information without further preparation these strew mounts display a wider area for analysis per gram of isolated kerogen when compared to polished plugs increasing the probability to find phytoclasts in scarce populations the proposed method was developed regarding oil prospection calibrating the raman spectrometer with organic matter from rocks with vitrinite reflectance between 0 3 and 2 1 a set of raman parameters was combined using multilinear regression cross validation of the proposed regression showed that the spectral parameters of translucent phytoclasts resulted in a maturity estimate that correlated well with the vitrinite reflectance

thermochronologic constrains on the processes of formation and exhumation of the xinli orogenic gold deposit jiaodong peninsula eastern china abstract the xinli orogenic gold deposit with gold resources of 40 t located in the northwestern part of the giant jiaodong gold province eastern china is controlled by the sanshandao fault and is one of a few deposits hosted by the early cretaceous 129 128 ma guojialing granitoid soon after intrusion the granitoid underwent ductile shearing at 400 500 c marked by recrystallized quartz ribbons and bending of plagioclase lamellae with rapid cooling from zircon crystallization temperature of 750 800 c at 129 128 ma u pb to closure temperature of 300 50 c for biotite 40ar 39ar method at 124 1 ma the ductile deformation lasted 4 million years mineralization was associated with subsequent brittle reactivation of normal movement on the fault indicated by a se plunging downdip lineation on the fault a hydrothermal sericite 40ar 39ar age of 121 ma inferred to date the alteration associated with gold mineralization has been previously obtained for the adjoining cangshang gold deposit also controlled by the sanshandao fault at the xinli deposit the 121 5 1 3 ma and 120 5 1 2 ma 40ar 39ar plateau ages of weakly fractured igneous k feldspar record closely the time of normal faulting and cooling within the range of mineralization temperatures 350 250 c two zircon fission track zft ages of 91 4 ma and 90 3 ma constrain the time of cooling through 240 50 c unimodal distribution of apatite fission track aft lengths with a slightly negative skew and mean fission track lengths of 12 3 0 2 m indicate relative slow continuous cooling through 125 60 c at 60 6 ma the slight acceleration of cooling around 90 ma constrained by the 40ar 39ar zft and aft data and thermal modelling may have resulted from the late normal reactivation of the sanshandao fault in summary extension and normal faulting not only created the channelways for the mineralizing fluids but also gave rise to the subdued topography and post mineralization exhumation that preserved the deposit

paradigm shift in determining neoproterozoic atmospheric oxygen acknowledgments we thank the geological survey of australia for permission to sample the empress 1a and lancer 1 cores the natural sciences and engineering research council of canada for financial support grant 7961 15 of u brand and the national natural science foundation of china for support of f meng and p ni grants 41473039 and 4151101015 we thank m lozon brock university for drafting and constructing the figures we thank the editor brendan murphy as well as three reviewers steve kesler erik sperling and an anonymous reviewer for improving the manuscript into its final form

the formation of inertinite rich peats in the mid cretaceous gates formation implications for the interpretation of mid albian history of paleowildfire abstract image analysis and standard point count petrographic data are used to interpret the amount source and variation of inertinite in coal seams of the mid cretaceous gates formation rocky mountain foothills northeastern british columbia inertinite on average is abundant between 40 60 by seam by volume and higher in some zones and within seams fluctuates cyclically the inertinite is interpreted to be almost exclusively fire derived suggesting that fire was a relatively common occurrence in the original peat forming wetlands inertinite enrichment in the gates coals appears to have resulted from preferential destruction of vitrinite precursors by either low temperature decomposition processes or burning rather than by formation of inertinite by a microbial process the position of the gates formation depositional setting east of the rising canadian cordillera is interpreted to have resulted in overall drier conditions in the region and periodic drought in the wetland settings cyclic variation in inertinite vitrinite composition within some of the seams is primarily attributed to climatic variations although variation in subsidence rates could also have been responsible

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

a holistic model for the origin of orogenic gold deposits and its implications for exploration the term orogenic gold deposits has been widely accepted but there has been continuing debate on their genesis early syn sedimentary or syn volcanic models and hydrothermal meteoric fluid models are now invalid magmatic hydrothermal models fail because of the lack of consistent spatially associated granitic intrusions and inconsistent temporal relationships the most plausible models involve metamorphic fluids but the source of these fluids is equivocal intra basin sources within deeper segments of the hosting supracrustal successions the underlying continental crust subducted oceanic lithosphere with its overlying sediment wedge and metasomatized lithosphere are all potential sources several features of precambrian orogenic gold deposits are inconsistent with derivation from a continental metamorphic fluid source these include the presence of hypozonal deposits in amphibolite facies domains their anomalous multiple sulfur isotopic compositions and problems of derivation of gold related elements from devolatilization of dominant basalts in the sequences the phanerozoic deposits are largely described as hosted in greenschist facies domains consistent with supracrustal devolatilization models a notable exception is the jiaodong gold deposits of china where ca 120 ma gold deposits are hosted in precambrian crust that was metamorphosed over 2000 million years prior to gold mineralization other deposits in china are comparable to those in the massif central and elsewhere in france in that they are hosted in amphibolite facies domains or clearly post date regional metamorphic events imposed on hosting supracrustal sequences if all orogenic gold deposits have a common genesis the only realistic source of fluid and gold is from devolatilization of a subducted oceanic slab with its overlying gold bearing sulfide rich sedimentary package or the associated metasomatized mantle wedge with co2 released during decarbonation and s and ore related elements released from transformation of pyrite to pyrrhotite at about 500 c although this model satisfies all geological geochronological isotopic and geochemical constraints and is consistent with limited computer based modeling of fluid release from subduction zones the precise mechanisms of fluid flux are model driven and remain uncertain from an exploration viewpoint the model re emphasizes the ubiquitous occurrence of orogenic gold deposits in subduction related orogenic belts and importance of continental scale lithosphere tapping fault and shear zones to focus large volumes of auriferous fluid it confirms the importance of the consistent spacing between world class deposits broadly equivalent to the depth of the moho as derived from empirical observations

foraminiferal fauna recovered after the late permian extinctions in iberia and the westernmost tethys area abstract the mass extinction at the end of the permian has long been recognized as the greatest in the history of life foraminifers were common throughout the permian triassic p t interval and provide one of the best and certainly the most informative fossil records of the p t crisis this study addresses the recovery of foraminiferal faunas during the triassic after the late permian extinction in the western tethys and particularly in iberia through the analysis of evolution rates both at the species and genus level for the tethys area in general a rapid recovery of these faunas during the olenekian is reflected by high rates of appearance of new taxa along with the reappearance of many lazarus taxa these taxa became stabilized throughout the anisian and ladinian with a reduction in the rates of origination of new taxa and the presence of associations that were highly diversified comprising large numbers of species the first foraminifers in the triassic of iberia can be observed at two different levels the first of these is in the upper anisian while the second level corresponds to the upper ladinian longobardian lower carnian the triassic associations of the basins of iberia show paleobiogeographic characteristics that are generally tethyan most of these associations being well known for the alpine triassic for the ladinian some associations from ne iberia ne iberian basin catalonian basin and pyrenean basin also show germanic affinities finally also for the ladinian there is some evidence of the possible southward movement of faunas from the sephardic domain to the betic basin this point however requires further investigation with the exception of faunas associated with the reefs of the ladinian catalonian basin communities are usually of low diversity and typical of unstable shallow marine facies

blue fluorescing amber from cenozoic lignite eastern sikhote alin far east russia preliminary results abstract blue and greenish yellow in addition to ordinary yellow orange amber has recently been found in a lignite seam in the zerkal nenskaya depression primorsky krai russia the amber is associated with abundant charcoal and fusain fragments in the host rocks its ftir spectra indicate the presence of significant quantities of volatile matter including free hydroxyl groups and carbon dioxide both co 2 and oh contents are greater in the greenish yellow and blue hard varieties suggesting rapid heating possibly from a wildfire followed by rapid cooling in water as a causative agent of amber hardening and extreme polymerization this process and the following amber deposition in the reduced environment might produce the fluorescent aromatics that have been previously suggested and confirmed by this study as the blue glow main cause

pyritization a palaeoenvironmental and redox proxy reevaluated abstract pyrite as a proxy for the redox states of bottom waters was evaluated in the context of modern salt marsh sediments two sites 40 m apart with very different physicochemical properties were sampled seasonally the sites differed from each other in 1 the amount of tidal flushing 2 vegetation 3 redox condition below the sediment water interface 4 carbon content and 5 solid phase iron oxyhydroxide and iron sulfide content of the sediment the calculated degree of pyritization dop varies between 0 44 and 1 0 depending on the site and the season different dop values were obtained for the same samples when different techniques were applied for extraction of reactive iron framboidal pyrite was dominant however other textural forms of pyrite were also observed the size distribution of the individual pyrite crystals and the framboids was fairly narrow with the majority of them having diameters

the descriptive nomenclature and classification of growth fabrics in fossil scleractinian reefs abstract framework sensu stricto is a concept originally relating to modern reefs and is defined by structural ecological and sedimentological criteria however in the geological literature the term framework has come to be applied to almost any organically influenced in situ accumulation including non calcareous non rigid facies associated with sea grasses this drastic departure from the original meaning is misleading and scientifically unhelpful the concept of wave resistance is integral to that of framework but in the geological record it is not easy to evaluate and the term may be of little comparative use between reef environments it is suggested that the term growth fabric be generally applied as a descriptive term for the presence of aggregated in situ corals or other organisms in growth position within a facies the term growth fabric should be used as an alternative to framework as a purely descriptive term the term framework should be restricted to its original definition and used only where the criteria for framework can be clearly demonstrated two end member types of scleractinian growth fabric genesis are recognised termed superstratal and constratal terms adapted from gili e masse j p skelton p w 1995 rudists as gregarious sediment dwellers not reef builders on cretaceous carbonate platforms palaeogeogr palaeoclimatol palaeoecol 118 245 267 in a superstratal growth fabric the constituent organisms collectively projected decimetres to metres above the substratum creating positive topographic relief in contrast constratal growth is where vertical organic accretion occurred at a similar rate to sediment accumulation hence the majority of the skeletal material remained continuously embedded in the sediments and only a small proportion of the skeleton projected centimetres above the sediment surface the architectural palaeoecological sedimentological and diagenetic implications of different types of growth fabric genesis is discussed a review of the classification of reef fabrics suggests that there is currently no adequate system to describe fossil scleractinian growth fabrics the most commonly used classification of reefal fabrics is that of embry and klovan 1971 embry a f klovan j e 1971 a late devonian reef tract on northeastern banks island northwest territories bull can pet geol 33 730 781 there are a number of shortcomings in this scheme which may be grouped into three categories 1 the interpretative nature of the classification 2 problems in interpreting biological effect from form and 3 insufficient categories to adequately describe mesozoic and cenozoic growth fabrics moreover there appears to be a lack of a standardised nomenclature for growth fabrics which has hindered meaningful comparisons of scleractinian growth fabrics through time and space a descriptive system based on a modification and expansion of the embry and klovan system 1971 is proposed and a revised nomenclature for growth fabrics presented the system is designed to be flexible in its application it can be used simply to describe a growth fabric or through the use of genetic and non genetic modifiers to imply types of reef building processes and growth fabric heterogeneity although the concepts and terminology discussed in this paper relate to scleractinian growth fabric they are equally applicable to fabrics comprising other organisms

link between gold provinces low salinity high temperature 200 degrees c reducing fluids are poorly represented in ore forming processes yet appear to account for 90 percent of the primary gold mined to date such fluids have been implicated in the formation of many archcan greenstone witwatersrand slate belt and epithermal gold deposits these low salinity auriferous fluids occur in variable time space lithological sequence and tectonic settings and are most easily explained by metamorphic devolatilization of mafic and or graywacke successions metamorphism of chlorite calcite albite quartz assemblages e g mafic or graywacke at the greenschist amphibolite facies boundary occurs around 480 degrees or 20 degrees c for 3 5 kbars and produces large volumes of low salinity h 2 o co 2 fluid similar in composition to those recorded in many gold deposits widespread pyrite in the above assemblage typically leads to elevated levels of dissolved sulfur such conditions are ideal for gold transport as a molecular au s complex and can lead to deposits rich in gold relative to silver and base metals deposition of gold occurs in the temperature range of 250 degrees to 400 degrees c and can be facilitated by lower temperature lower sulfur activity and changes in oxygen activity lower sulfur activity is most readily achieved by fluid interaction with fe rich host rocks with the formation of pyrite or pyrrhotite whereas lower oxygen activity is readily achieved by interaction with carbonaceous metasediments low salinity fluids produced by metamorphic devolatilization provide a common theme embracing the formation of many archcan greenstone slate belt witwatersrand and potentially epithermal gold deposits it involves the common features of high geothermal gradient low salinity fluid high au ag high au base metals and broad synchroneity with metamorphism it also accounts for the considerable variability in hosting structures detailed timing relations host rocks alteration assemblages and geologic age of different deposits interestingly the similarities are explained by deeper processes the differences by processes at or near the depositional sites

mineral chemistry and sources of fluid and sulfur at the katbasu gold deposit in south tianshan nw china abstract katbasu is a gold and copper deposit located in an arc on the southern margin of the ili central tianshan micro continent an in situ method was conducted to acquire trace element concentrations to elucidate the origins and chemistry of the fluid in the katbasu deposit this included oxygen isotopes in quartz as well as sulfur isotopes and trace elements concentrations in pyrite trace elements in gold deficient veins have higher concentrations compared to those in the gold bearing veins the 18o values of gold deficient veins are between 3 9 and 8 1 which imply a magmatic oxygen isotope signature in contrast oxygen isotopes in gold bearing veins range between 1 3 and 5 8 indicating the involvement of meteoric water in the mineralization system this data combined with evidence from alteration style and metal assemblages shows that the ore forming fluids at the katbasu gold deposit is of a magmatic origin the data also indicates that meteoric water diluted the magmatic fluid and caused an oversaturation of gold causing precipitation of native gold grains trace elements in pyrite show no difference among the veins analyzed however they have distinctly different trace element patterns of pyrite from orogenic gold deposits based on the 34s values of pyrite 8 3 12 9 and the lack of coeval regional metamorphism we conclude that the enriched 34s at the katbasu gold deposit is derived from a subducted slab during the late carboniferous

clues from fluid inclusions the reconstruction of past conditions on earth involves a multitude of disciplines and techniques in his perspective goldstein highlights the potential of fluid inclusions in small halite or calcite crystals formed for example when marine waters evaporate such inclusions can provide information for example about seawater composition paleoclimatic conditions and paleobiology for example lowenstein et al have used inclusions in halite crystals to show that the chemical composition of ancient seawater was different from that of modern seawater and that plate tectonics probably controlled much of this variation

stratigraphic distribution and significance of a 15 million year record of fusain in the upper triassic chinle group southwestern usa abstract we document the occurrence of upper triassic fusain in northern arizona southern utah and northern new mexico in latest carnian to norian age alluvial strata of the monitor butte formation and the sonsela and painted desert members of the petrified forest formation chinle group the fusain identified by standard techniques of macroscopic and microscopic morphology and resistance to chemical oxidation is present at multiple stratigraphic horizons at several locations that are approximately correlative although separated by several hundred km the morphology of this fossil charcoal includes large partially charred silicified to coalified logs completely charred smaller limbs charcoal fragments reworked in fluvial deposits and particulate fusain disseminated in sediments the apparent rarity of fusain in triassic strata previously was cited as evidence for relatively low levels compared to modern of atmospheric oxygen and the consequent infrequent occurrence of wildfire during this time interval however our findings demonstrate a significantly greater abundance of fusain in upper triassic strata than previously acknowledged therefore we suggest that wildfire was not an unusual occurrence during the late triassic this conclusion supports recent experimental studies and geochemical models that indicate atmospheric oxygen levels at or above modern levels during the late triassic

the survival recovery and diversification of metazoan reef ecosystems following the end permian mass extinction event abstract the triassic period records important ecological transitions in the aftermath of the end permian mass extinction and is a key interval in the evolution of modern coral reefs there have been several critical developments in our understanding of triassic reef evolution over the past decade the timing of events and duration of stages have changed dramatically the discovery of metazoan reefs in the early triassic details about the environmental perturbations that drove the extinction the relationship between tectonic activity and platform margin reef proliferation and additional proxy evidence for the co evolution of coral reef builders and their photosymbionts here we provide an up to date synthesis of reef collapse and recovery dynamics following the end permian extinction specifically integrating recent discoveries the evolution of reef ecosystems can be divided into five phases based on their composition 1 microbial metazoan reefs represent survival communities that characterize the immediate extinction aftermath 2 the re establishment of reefs built by metazoans small sponge biostromes and bivalve buildups is observed in oxygenated settings in the olenekian early triassic 3 towards the end of the olenekian and into the anisian middle triassic low diversity tubiphytes dominated reefs formed which represent the first triassic platform margin reefs platform margin reefs however are not widespread until the late anisian 4 late anisian reefs also record a composition change and increase in species richness with sponges and tubiphytes as the main reef builders 5 the first scleractinian corals which are the main reef builder in modern marine reef ecosystems evolved during the anisian but are not reported as dominant reef builders until the late triassic the radiation of coral reefs is posited to be coupled to the acquisition of photosymbionts e g zooxanthellae there is clearly a stepwise evolution of reef types during the triassic however once each reef type appears it persists throughout the remainder of the triassic the survival recovery and diversification of reef ecosystems is therefore more complex than previously outlined particularly with respect to the earliest post extinction ecosystems these recent advances highlight the need to thoroughly document the faunal compositions of understudied reef systems as well as to continue the exploration of triassic ecosystems in underrepresented regions

reef expansion during the triassic spread of photosymbiosis balancing climatic cooling the paleoreefs database indicates that reef abundance increased profoundly during the triassic period from a pronounced low in the early triassic to a major peak in the norian this expansion is also evident when standardizing for sampling corresponding to the reef expansion is a relative increase of scleractinian corals as reef builders whereas the contribution of hypercalcifying sponges and microbes decreased during the triassic the numerical expansion of corals is paralleled by a proportional increase of morphological features that are suggestive of photosymbiosis such that the norian reef boom might be explained by the spread of photosymbiosis in corals the geographical expansion of reefs was far less pronounced especially concerning palaeolatitude late triassic reef growth was limited to more or less the same latitudinal range as modern reefs as oxygen isotope data and new modeling results indicate declining temperatures and co2 concentrations during the late triassic the lack of latitudinal expansion might be attributed to global cooling reef development during the triassic can thus be explained by the evolutionary spread of photosymbiosis balancing the effects of climatic cooling

environmental significance of microbialites in reef environments during the last deglaciation in situ microbialites occurring in reef rocks dredged between 80 and 130 m water depth on the modern fore reef slopes of tahiti and the marquesas islands yield ages ranging from 17 100 2900 to 4410 2250 years bp suggesting that they played a prominent role during the last deglacial sea level rise microbialites developed in both shallow and deep water depositional environments where they characterize various zones of the reef tracts reef crests upper reef slopes deep fore reef slopes reflecting contrasting scenarios of microbialite development involving reefal microbialites in shallow water settings and slope microbialites that formed in environments deeper than 10 20 m and extending down to more than 100 m reefal microbialites correspond to a late stage of encrustation of the dead parts of coral colonies or more commonly of related encrusting organisms red algae and foraminifers thus forming surface crusts slope microbialites generally form the ultimate stage of a biological succession indicating a deepening sequence whereby shallow water corals and associated encrusting organisms are replaced by deeper water assemblages of red algae and foraminifers before microbialite growth the precipitation of phosphatic iron manganese crusts and the deposition of planktonic micritic limestones on the microbialites characterize a deepening upward sequence the widespread development of microbialites in reef sequences from the last deglaciation characterizes a period of environmental degradation consequential on the rapid sea level rise and abrupt climatic changes of that time the reported biological succession reflects changes in water quality and especially an increase in nutrients in shallow water settings increased alkalinity and nutrient availability in interstitial waters were related to surface fluxes and terrestrial groundwater seepage while slope environments were exposed to continuous upwelling of nutrient rich deeper waters during the last deglacial sea level rise the age differences between corals and overlying slope microbialites range from 1600 to 8400 years based on high precision u series age measurements of both corals and microbialites and indicates that a significant time several thousand years elapsed between the development of the coralgal frameworks and the growth of slope microbialite crusts microbialites cannot be considered as part of the drowning event some 14 000 years ago that resulted in the demise of reef frameworks in the 90 110 m present depth range but are substantially younger

fossil charcoal as an indicator of palaeoatmospheric oxygen level charcoal results from incomplete combustion of plant material it is produced naturally by wildfire and being relatively tough and unbiodegradable it may be transported and incorporated into a variety of sedimentary environments wildfire requires adequate atmospheric oxygen for the combustion of plant fuel wood leaf litter fossil charcoal from the devonian onwards suggests that the oxygen level in the atmosphere has not fallen below 13 in this interval further the extreme flammability of even wet plant fuel at oxygen levels above 35 makes this the highest figure compatible with the occurrence of terrestrial vegetation

x ray microtomographic imaging of charcoal we assess the potential of x ray microtomography as a tool for the non destructive three dimensional examination of the internal structure of charcoal microtomographic analysis of a series of charcoals produced by the experimental pyrolysis of pine wood at temperatures from 300 and 600 c in nitrogen only and in nitrogen mixed with 2 oxygen indicates that despite substantial shrinkage observed porosity pore size and pore connectivity are all increased by pyrolysis and also by chemical oxidation analysis of a number of altered and unaltered archaeological and geological charcoals has demonstrated the capacity of the technique to identify and map the distribution of authigenic mineral contamination within charcoal fragments the results are of significance to radiocarbon dating in that they provide insights into the mechanisms by which charcoal can be contaminated by extraneous carbon in the natural environment

holocene wildfires related to climate and land use change over the weihe river basin china abstract charcoal particles preserved in the loess palaeosol profiles provide records of wildfires during the holocene total organic carbon magnetic susceptibility and charcoal analysis and osl dating were carried out in the holocene loess palaeosol profiles at two sites in the weihe river basin the analytical results show that natural wildfires occurred frequently during the last glaciation when climate was dominated by northwest continental monsoon and steppe vegetation expanded southerly to the weihe river basin wildfire occurrence decreased during climatic amelioration in the early holocene during the holocene climatic optimum between 8500 b p and 3100 b p natural wildfire occurrence was reduced greatly pedogenic alteration to the accumulated dust was intensified because of the humid warm climate brought on by southeast maritime monsoon localized fire events in connection with human activities of the neolithic occurred in several episodes over the region during the late holocene when climate become drier wildfire occurrence over the upland hills shows a pattern different from that in the guanzhong basin over the upland hills in the north charcoal concentrations show a decreasing trend in the recent loess and topsoil it indicates infrequent biomass burning during the last 3100 years this is attributable to nomadic occupation of the loess hills during the bronze age and the development of a land use pattern of livestock farming in most part of the history over the loess tableland in the guanzhong basin in the south abruptly increased charcoal concentrations in the recent loess and topsoil show very high level of biomass burning this is attributable to the increasingly intensified land reclamation for cereal cultivation from the bronze age this study provides new insights into wildfires over the semi arid and sub humid regions in connection with climate and land use change

paleogeographic trends in late triassic reef ecology from northeastern panthalassa the late triassic was a pivotal period in reef evolution but the majority of information about reef ecology during this time comes from buildups in the alps e g the tethys ocean recent studies of reefs in western north america have recognized unique ecologies along the eastern margin of the panthalassa ocean although there are numerous twenty five localities with putative reef builders only four buildups had syndepositional relief and a rigid framework i e true reefs the most paleo northern true reefs were microbial patch reefs with only a few large skeletal bioconstructors hypercalcified sponges and spongiomorphs built the mid latitude reefs with secondary microbial encrustation and branching phaceloid retiophyllia corals corals are the primary bioconstructors in panthalassa s most paleo equatorial reefs and calcareous microbes are sparse when all reefal deposits are analyzed the n s gradient is also present with microbial and bivalve deposits in the north sponge coral deposits in the mid latitudes and coral deposits near the equator this ecological gradient is not apparent in the tethys ocean tethyan reefs thrived in oligotrophic tropical waters without strong latitudinal gradients by contrast paleoceanographic considerations suggest that cool nutrient rich waters swept south along the western north american borderlands in the late triassic the eastern boundary current is interpreted to have created a strong north south differentiation of environments in northeastern ne panthalassa that was manifested in both the biotic and abiotic characteristics of eastern panthalassic reefs reefs from equatorial panthalassa are similar to tethyan reefs warm water photozoan coral reef structures whereas higher paleo latitude reefs from panthalassa are interpreted as cool water heterozoan buildups with abundant calcareous microbes diminutive biocalcifiers and few large framework building corals

modeling atmospheric o2 over phanerozoic time a carbon and sulfur isotope mass balance model has been constructed for calculating the variation of atmospheric o2 over phanerozoic time in order to obtain realistic o2 levels rapid sediment recycling and o2 dependent isotope fractionation have been employed by the modelling the dependence of isotope fractionation on o2 is based for carbon on the results of laboratory photosynthesis experiments and for sulfur on the observed relation between oxidation reduction recycling and s isotope fractionation during early diagenetic pyrite formation the range of fractionations used in the modeling agree with measurements of phanerozoic sediments by others results derived from extensive sensitivity analysis suggest that there was a positive excursion of o2 to levels as high as 35 during the permo carboniferous high o2 at this time agrees with independent modeling based on the abundances of organic matter and pyrite in sediments and with the occurrence of giant insects during this period the cause of the excursion is believed to be the rise of vascular land plants and the consequent increased production of o2 by the burial in sediments of lignin rich organic matter that was resistant to biological decomposition

a practical classification of gold deposits with a theoretical basis abstract well considered schemes that classify ore deposits can be effective contributors to exploration success understanding of deposit genesis mining geology engineering metallurgy property valuations and stock market analysis an effective classification scheme needs to be easy to apply without ambiguity and is much more powerful if based on sound scientific principles for deposits with economic gold a useful classification recognises gold only and gold plus deposits based upon whether they also have economic base metals the scheme is easy to apply and in most cases unambiguous for specific deposits and whole provinces the subdivision has a sound scientific basis that involves the chemistry of gold in relation to metal complexing salinity of ore forming fluids and redox state forward modelling from chemical principles can be integrated with inverse modelling from observations to add confidence in this classification and thus be used to create exploration opportunities the jiaodong gold province of eastern china comprises deposits mostly in granitic rocks with economic gold but low levels of base metals the inferred ore fluids are of low to moderate salinity from their gold only character several other aspects of their development can be inferred though the tectonic and metamorphic history remains unresolved the granitic host rocks appear to reflect a chemically and mechanically favourable site for deposition not a source for the gold or the ore fluid neither of which have been established yet

evidence of widespread wildfires in coal seams from the middle jurassic of northwest china and its impact on paleoclimate abstract today wildfire is an important disturbance in many continental ecosystems and it is assumed that with ongoing climate changes the frequencies and impacts of wildfires will increase in many regions one way to obtain information about the potential long term influences of wildfires on ecosystems and the climate system itself is to study palaeo wildfires a total of 140 jurassic samples including 122 coal samples and 18 rock samples from roof and floor of coal seams were collected from 4 coalfields in northwestern china the samples were analyzed by macropetrography microscopy scanning electron microscopy gas chromatography and gas chromatography mass spectrometry to study the evidences of wildfires and their impact on the paleoclimate high contents of pyrogenic inertinites charcoal natural char and natural coke particles observed in the samples which indicate that widespread wildfire events occurred in the early middle jurassic in all over northwestern china additionally high molecular weight polycyclic aromatic hydrocarbons were detected in the coal samples these aromatic compounds were formed under high temperature and provide further evidence of wildfires according to a carbon emission model for modern forest fires the total carbon and gas emissions from wildfires in peat swamps of the middle jurassic in northwest china were calculated by the data from 21 575 coal samples of number of 1567 drill core samples the total carbon released from peat swamp forest wildfires was at least 1207 gt corresponding to emissions of co2 co and ch4 of 1926 gt 163 gt and 8 8 gt respectively the huge amount of co2 released by forest fires in the peat swamp systems of the middle jurassic in northwestern china alone was equivalent to 64 20 of the total co2 in the atmosphere at present 3000gt the large amounts of greenhouse gases released by wildfires must have led to long term changes in the atmospheric composition and have caused global warming which could have the reason of affected the paleoclimate

palaeoatmospheres in the phanerozoic except in the recent geological past palaeoatmospheric composition cannot be measured but only inferred from palaeontological or geochemical observations the likely controls on atmospheric composition are reviewed and the role of organisms stressed as monitors recorders motors and moderators of palaeoatmospheric changes whereas there is a good general case for changes in po 2 and pco 2 during phanerozoic time proposals for timing and mechanism in the earlier phanerozoic are speculative at present it seems probable that the late palaeozoic spread of land plants raised o 2 and reduced co 2 levels in the atmosphere the end cretaceous crisis had a transient impact on the atmosphere whose general constancy through geological time is one of the most remarkable features of earth history

black carbon in soils and sediments analysis distribution implications and current challenges this review highlights the ubiquity of black carbon bc produced by incomplete combustion of plant material and fossil fuels in peats soils and lacustrine and marine sediments we examine various definitions and analytical approaches and seek to provide a common language bc represents a continuum from partly charred material to graphite and soot particles with no general agreement on clear cut boundaries formation of bc can occur in two fundamentally different ways volatiles recondense to highly graphitized soot bc whereas the solid residues form char bc both forms of bc are relatively inert and are distributed globally by water and wind via fluvial and atmospheric transport we summarize chronologically the ubiquity of bc in soils and sediments since devonian times differentiating between bc from vegetation fires and from fossil fuel combustion bc has important implications for various biological geochemical and environmental processes as examples bc may represent a significant sink in the global carbon cycle affect the earth s radiative heat balance be a useful tracer for earth s fire history build up a significant fraction of carbon buried in soils and sediments and carry organic pollutants on land bc seems to be abundant in dark colored soils affected by frequent vegetation burning and fossil fuel combustion thus probably contributing to the highly stable aromatic components of soil organic matter we discuss challenges for future research despite the great importance of bc only limited progress has been made in calibrating analytical techniques progress in the quantification of bc is likely to come from systematic intercomparison using bcs from different sources and in different natural matrices bc identification could benefit from isotopic and spectroscopic techniques applied at the bulk and molecular levels the key to estimating bc stocks in soils and sediments is an understanding of the processes involved in bc degradation on a molecular level a promising approach would be the combination of short term laboratory experiments and long term field trials

mineralization age and geodynamic background for the shangjiazhuang mo deposit in the jiaodong gold province china abstract the shangjiazhuang mo deposit is located on the jiaodong peninsula in eastern china which is famous for the ca 120 ma jiaodong type au deposits with total au endowment of over 3000 t in this paper we discuss the deposit geology mineralization age and geochemical features of the host granodiorite of the shangjiazhuang mo orebody using this information we aim to clarify the time and geodynamic mechanism for the mo deposit which is another constraint to understand the genesis of au deposits the mo mineralization generally occurs as quartz sulfide veins within the medium grained yashan granodiorite the alteration consists of potassic alteration silicification sericitization chloritization and carbonatization with a weak unclear zonation the ore minerals mainly include molybdenite chalcopyrite and pyrite we measured re os isotopes of molybdenite grains which yielded a weighted mean model age of 116 9 0 81 mswd 1 03 and a well constrained 187 re 187 os isochron age of 117 1 1 4 ma mswd 1 6 these ages are slightly younger than the age of au mineralization on the jiaodong peninsula rhenium contents of 5 84 29 99 ppm with an average of 16 4 ppm in molybdenites indicate a crustal source whole rock geochemical compositions show that the granodiorite is high k calc alkaline and metaluminous to peraluminous the samples show low y contents from 8 2 to 10 5 ppm and sr y ratios from 48 2 to 58 8 displaying an adakitic affinity the yashan granodiorite has high initial 87 sr 86 sr ratios of 0 7101 to 0 7104 low e nd t values of 17 6 to 16 7 and zircon e hf t values from 24 8 to 17 1 with corresponding hf model ages of 2 7 to 2 2 ga these isotopic data together with the adakitic affinity of the granodiorite indicate that the parental magma was derived from ancient crust mafic microgranular enclaves mme that are contemporaneous with the host granodiorite show sio 2 contents of 57 98 58 41 wt and depletion in nb ta the mmes show enriched initial 87 sr 86 sr ratios of 0 7102 to 0 7106 and low e nd t values of 17 3 to 16 3 the mmes are the products of mixing between the metasomatized lithospheric mantle derived mafic magma and the ancient crust derived felsic magma the early cretaceous mo mineralization 120 110 ma is slightly younger than the peak time of au mineralization 126 120 ma on the jiaodong peninsula but have a different spatial distribution which suggests different sources of au and mo the jiaodong type au deposits were probably related to the upwelling of metasomatized lithospheric mantle while the mo mineralization on the jiaodong peninsula may delineate a 120 110 ma mo metallogenic belt along the southern margin of the north china craton with the east qinling which is related to the melting of ancient crustal sources the subduction of the paleo pacific slab and accompanying asthenospheric upwelling triggered upwelling of metasomatized lithospheric mantle forming jiaodong type au deposits subsequently the ponding of mantle derived magmas resulted in partial melting of ancient crust and associated mo deposits

orogenic gold mineral systems of the western lachlan orogen victoria and the hodgkinson province queensland crustal metal sources and cryptic zones of regional fluid flow abstract orogenic gold mineral systems in the western lachlan orogen victoria and the hodgkinson province queensland produced gold provinces characterised by vastly different scales of gold endowment and strongly uneven distribution of gold mineralisation within each province the volume of hydrous pyrite bearing rocks undergoing metamorphic devolatilisation during thermo tectonic events driving orogenic gold mineral systems represents a fundamental first order constraint on the total gold endowment and its broad spatial distribution both between and within the provinces most of the largest gold deposits in both regions occur in linear richly endowed metallogenic zones oblique to the dominant regional structures and related to deep crustal domain boundaries these boundaries with only subtle surface expressions were the major regional structural controls which promoted focused near vertical flow of mineralising metamorphic fluids above the outer margins of cratonic blocks in the lower crust recognised major faults represented only more local scale and often indirect controls on the focused fluid flow particularly effective above the deep cratonic block boundaries overlain by relatively thick crustal source rocks

anatomy of a world class epizonal orogenic gold system a holistic thermochronological analysis of the xincheng gold deposit jiaodong peninsula eastern china abstract xincheng is a world class orogenic gold deposit hosted by the early cretaceous guojialing granitoid in the jiaodong peninsula eastern china a zircon u pb age of 126 1 4 ma together with previous data constrain the emplacement of the guojialing intrusion to 132 123 ma the granitoid underwent subsolidus ductile deformation at 500 c following its intrusion the small difference in age between the youngest zircon u pb age of unaltered granitoid 123 ma and the ca 120 ma 40ar 39ar ages of sericite associated with breccias and gold mineralization within it indicate initial rapid cooling from magmatic temperatures to those prevalent during brittle deformation and associated gold mineralization at 220 300 c evidence of a direct association between granitic magmatism and gold mineralization such as at least localized near magmatic depositional temperatures and metal zoning evident in undoubted intrusion related gold deposits is absent the 40ar 39ar age of 120 ma coincides with the mineralization age of many other orogenic gold deposits along the jiaojia fault sixteen zircon fission track zft ages across the ore and alteration zones range from 112 9 3 4 to 99 1 2 7 ma the long period of cooling to the 100 ma zft closure temperatures recorded here suggests that ambient temperatures for hydrothermal alteration systems lasted to 100 ma possibly because of their focus at xincheng within the young guojialing granitoid as it cooled more slowly below approximately 300 c to 220 c however the restricted number of auriferous ore stages combined with the presence of cross cutting gold free quartz carbonate veins indicate that gold itself was only deposited over a restricted time interval at 120 ma consistent with studies of orogenic gold deposits elsewhere this highlights the complex interplay between magmatism deformation and the longevity of hydrothermal systems that cause genetic controversies based on apatite fission track aft ages the xincheng gold deposit was then uplifted and exhumed to near the surface of the crust at 15 ma probably due to movement on the crustal scale tan lu fault recognition of such exhumation histories along gold belts has conceptual exploration significance in terms of the probability of discovery of additional exposed or sub surface gold ore bodies as discovery is as much a function of preservation as formation of the deposits

fluid inclusions in sedimentary and diagenetic systems abstract some of the major problems in sedimentary geology can be solved by using fluid inclusions in sedimentary and diagenetic minerals important fluids in the sedimentary realm include atmospheric gases fresh water of meteoric origin lake water seawater mixed water evaporated water formation waters deep in basins oil and natural gas preserving a record of the distribution and composition of these fluids from the past should contribute significantly to studies of paleoclimate and global change research is essential for improving understanding of diagenetic systems and provides useful information in petroleum geology applications of fluid inclusions to sedimentary systems are not without their complexities some fluid inclusions exposed to natural conditions of increasing temperature may be altered by thermal reequilibration which results in stretching or leakage and refilling of some fluid inclusions similarly overheating in the laboratory can also cause reequilibration of fluid inclusions so fluid inclusions from the sedimentary realm must be handled carefully and protected from overheating natural overheating of fluid inclusions must be evaluated through analysis of the most finely discriminated events of fluid inclusion entrapment fluid inclusion assemblages fia consistency in homogenization temperatures within a fluid inclusion assemblage consisting of variably sized and shaped inclusions is the hallmark of a data set that has not been altered through thermal reequilibration in contrast fluid inclusion assemblages yielding variable data may have been altered through thermal reequilibration if a fluid inclusion assemblage has not been altered by thermal reequilibration its fluid inclusions may be useful as geothermometers for low and high temperature systems or useful as geobarometers applicable throughout the sedimentary realm if a fluid inclusion assemblage has been altered partially by thermal reequilibration techniques for distinguishing between altered and unaltered fluid inclusions may be applied in studies of global change fluid inclusions can be used as sensitive indicators of paleotemperature of surface environments fluid inclusions also preserve microsamples of ancient seawater and atmosphere the analysis of which could figure prominently into discussions of past changes in chemistry of the atmosphere and oceans in petroleum geology fluid inclusions have proven to be useful indicators of migration pathways of hydrocarbons they can delineate the evolution of the chemistry of hydrocarbons and they remain important in understanding the thermal history of basins and relating fluid migration events to evolution of reservoir systems in studies of diagenesis fluid inclusions can be the most definitive record most diagenetic systems are closely linked to temperature and salinity of the fluid thus fluid inclusions are sensitive indicators of diagenetic environments

microbial framework in upper triassic carnian patch reefs from williston lake british columbia canada abstract the upper triassic carnian patch reefs from pardonet hill british columbia canada are the only known upper triassic reefal buildups from the craton margin of northwestern pangaea these buildups occur within the lower baldonnel formation and are characterized by a moderately diverse assemblage of corals spongiomorphs crinoids echinoderms bivalves gastropods brachiopods and microbialites despite the evidence that these buildups had a rigid structure e g brecciation and hardgrounds and relief above the seafloor visible in outcrop the exact nature and extent of the framework has previously been undetermined this study focuses on the microfacies within these patch reefs and highlights the importance of microbialites in the framework of these diminutive buildups 100 m3 to 500 m3 the pardonet hill patch reefs were mapped in outcrop to determine their structure geometry and the importance of large metazoan framework builders samples of the reefal horizons and surrounding strata were evaluated utilizing point count analyses of organisms cements lithic grains and microbial textures in thin section quantitative analysis of the microfacies in concert with traditional descriptions of reef construction and reef classification allow a more thorough understanding of organism abundance and reef structure despite the presence of corals and spongiomorphs throughout the outcrop they very rarely form a true intergrown framework except at the base of patch reef b instead cemented microbialites form a rigid framework in the core of some patch reefs detailed examination of the microfacies and reef construction demonstrates the importance of non skeletal framework builders in the structural fabric of these small buildups pardonet hill patch reef b is the first true reef with a microbial framework documented from the upper triassic of north america this microbial coral framework bears a striking similarity to some triassic and upper jurassic coral microbial reefs from the tethys although the depositional environment of the pardonet hill patch reefs is likely shallower and more energetic than the tethyan reefs

charcoalified logs as evidence of hypautochthonous autochthonous wildfire events in a peat forming environment from the permian of southern parana basin brazil abstract evidences of paleowildfires from the upper coal seam s from the faxinal coalfield have been analyzed through petrographic fluorescence and scanning electron microscopy sem specifically at the base 1 and top 2 boundaries of an interlayered tonstein bed and revealed recurrent charcoal deposition in the peat forming environment an unusual accumulation of adjacent large sized 21 8 13 4 cm and larger charred logs occurs throughout the coal seam area 1 6 km 2 beneath the tonstein bed boundary 1 reflecting an extensive wildfire event in hypautochthonous autochthonous conditions the logs display a semifusinite vitrinite semifusinite sandwich like structure sensu jones et al 1993 indicating burning in growth position and reflectance measurements below 1 ro suggest that this was a low temperature fire dryness in the peatland during the fire event was clearly detected by altered fluorescence of spores and algae corroborating previous studies the paleoecological setting can be characterized as a swamp forest based on the presence of pollen clusters and organs observed under fluorescent light and on the identification under sem of the morphogenus agathoxylon hartig as a single wood type reflecting the dominance of arborescent gymnosperms glossopterids in the peatland homogenized cell walls observed under sem ratified the recognition of the material as charcoal the reestablishment of regular conditions of peat deposition following the major fire episode is represented by alternate bands of vitrinite and semifusinite in both boundaries 1 and 2 suggesting an oscillation from dry to wet conditions in the climate pattern and the occurrence of wildfires as common and systemic events fire ignition activity and spread in the peat forming environment resulted from a combination of lightning strikes dryness fuel abundance and high atmospheric oxygen levels

an integrated mineral system model for the gold deposits of the giant jiaodong province eastern china abstract the giant jiaodong gold province with more than 5000 t of proven gold resources is unique in that its mesozoic gold deposits are hosted in a precambrian basement block there has long been debate on the source of gold the mechanism for its extreme enrichment and a holistic genetic model for these spectacular deposits in order to improve understanding of these factors a mineral system model is proposed for the jiaodong gold deposits for the first time it is based on a detailed review of the architecture and composition of the underlying mantle lithosphere the geodynamic setting at the time of gold mineralization the geological and geochemical features of the deposits themselves and mechanisms of their preservation regional geodynamic reconstructions combined with the nature of mesozoic magmatic systems show that late mesozoic breakoff of the subduction slab and rollback of the paleo pacific plate caused asthenosphere upwelling and lithosphere extension and thinning robust geochronological studies demonstrate that the jiaodong gold deposits formed at ca 120 ma during a change of subduction direction of the paleo pacific plate and the synchronous transition of tectonic regime from regional compression to transpression or transtension prior to peak extension caused by thinning of the lithosphere geophysical exploration data and hf nd isotope mapping of the jiaodong peninsula reveal a relatively simple ancient crustal structure cut by near vertical shear or fault zones including the lithosphere scale tan lu and wulian yantai faults that provided the first order architecture for emplacement of mantle magmas and sub crustal fluids in terms of fertility the significant older pre mineralization crustal metamorphism combined with sulfur lead and strontium isotope ratios indicate a dominant sub crustal source for the ore components for the jiaodong gold deposits consistent with evidence for volatile and gold fertilized metasomatized mantle lithosphere beneath the north china block helium ar and c o isotope ratios implicate mantle sources of ore fluids with contamination by crustal components en route to crustal depositional sites in terms of crustal architecture combined geophysical structural mineralogical fluid inclusion and geochemical studies show that the deeply sourced ore fluids and metals advected upwards through lithosphere scale faults to deposit gold via sulfidation and phase separation in crustal scale nne ne trending fault systems at mid to upper crustal levels preservation of disseminated to stockwork style deposits and auriferous quartz pyrite vein deposits was enhanced by deep crustal formation combined with limited uplift and exhumation of the province the jiaodong gold deposits although commonly hosted in granite intrusions clearly post date them on the basis of robust and reliable geochronology the spatial but non temporal relationships of gold deposits with granites their strong structural control and their other characteristics clearly place them in the orogenic gold group it is suggested because of their uniqueness that they be termed jiaodong type orogenic gold deposits

nature of ore forming fluid and formation conditions of bif hosted gold mineralization in the archean amalia greenstone belt south africa constraints from fluid inclusion and stable isotope studies abstract orogenic gold mineralization in the amalia greenstone belt is hosted by oxide facies banded iron formation bif hydrothermal alteration of the bif layers is characterized by chloritization carbonatization hematization and pyritization and quartz carbonate veins that cut across the layers the alteration mineral assemblages consist of ankerite ferroan dolomite minerals siderite chlorite hematite pyrite and subordinate amounts of arsenopyrite and chalcopyrite information on the physico chemical properties of the ore forming fluids and ambient conditions that promoted gold mineralization at amalia were deduced from sulfur oxygen and carbon isotopic ratios and fluid inclusions from quartz carbonate samples associated with the gold mineralization microthermometric and laser raman analyses indicated that the ore forming fluid was composed of low salinity h 2 o co 2 composition 3 wt nacl equiv the combination of microthermometric data and arsenopyrite pyrite geothermometry suggest that quartz carbonate vein formation gold mineralization and associated alteration of the proximal bif wall rock occurred at temperature pressure conditions of 300 30 c and 2 kbar thermodynamic calculations at 300 c suggest an increase in f o 2 10 32 10 30 bars and corresponding decrease in total sulfur concentration 0 002 0 001 m that overlapped the pyrite hematite magnetite boundary during gold mineralization although hematite in the alteration assemblage indicate oxidizing conditions at the deposit site the calculated low f o 2 values are consistent with previously determined high fe fe mg ratios 0 7 in associated chlorite absence of sulfates and restricted positive 34 s values in associated pyrite based on the fluid composition metal association and physico chemical conditions reported in the current study it is confirmed that gold in the amalia fluid was transported as reduced bisulfide complexes e g au hs 2 at amalia gold deposition was most likely a combined effect of increase in f o 2 corresponding to the magnetite hematite buffer and reduction in total sulfur contents due to sulfide precipitation during progressive fluid rock interaction the epigenetic features coupled with the isotopic compositions of the ore forming fluid 34 s s 1 8 to 2 3 18 o h2o 6 6 to 7 9 and 13 c c 6 0 to 7 7 at 300 330 c are consistent with an externally deep sourced fluid of igneous signature or and prograde metamorphism of mantle derived rocks

polycyclic aromatic hydrocarbons of pyrolytic origin in ancient sediments evidence for jurassic vegetation fires abstract polycyclic aromatic hydrocarbon pah distributions in an upper jurassic succession from offshore korea bay basin were consistent with a pyrolytic source being dominated by non alkylated species levels of these pahs were significantly higher in samples containing abundant fusinite macerals which are believed by some to be the product combustion the data were consistent with a pah origin from periodic conflagration throughout the upper jurassic of vegetation adjacent to a tectonically formed lake distribution of pahs exhibited some differences from those of combustion origin in recent and some ancient sediments and were characterized by the dominance of the highly peri condensed compounds benzo e pyrene benzo g h i perylene and coronene this characteristics reflects either preferential formation or preferential preservation under the prevailing sedimentary conditons of the highly peri condensed structures

geocarbsulf a combined model for phanerozoic atmospheric o2 and co2 abstract a model for the combined long term cycles of carbon and sulfur has been constructed which combines all the factors modifying weathering and degassing of the geocarb iii model berner r a kothavala z 2001 geocarb iii a revised model of atmospheric co2 over phanerozoic time am j sci 301 182 204 for co2 with rapid recycling and oxygen dependent carbon and sulfur isotope fractionation of an isotope mass balance model for o2 berner r a 2001 modeling atmospheric o2 over phanerozoic time geochim cosmochim acta 65 685 694 new isotopic data for both carbon and sulfur are used and new feedbacks are created by combining the models sensitivity analysis is done by determining 1 the effect on weathering rates of using rapid recycling rapid recycling treats carbon and sulfur weathering in terms of young rapidly weathering rocks and older more slowly weathering rocks 2 the effect on o2 of using different initial starting conditions 3 the effect on o2 of using different data for carbon isotope fractionation during photosynthesis and alternative values of oceanic 13c for the past 200 million years 4 the effect on sulfur isotope fractionation and on o2 of varying the size of o2 feedback during sedimentary pyrite formation 5 the effect on o2 of varying the dependence of organic matter and pyrite weathering on tectonic uplift plus erosion and the degree of exposure of coastal lands by sea level change 6 the effect on co2 of adding the variability of volcanic rock weathering over time berner r a 2006 inclusion of the weathering of volcanic rocks in the geocarbsulf model am j sci 306 in press results show a similar trend of atmospheric co2 over the phanerozoic to the results of geocarb iii but with some differences during the early paleozoic and for variable volcanic rock weathering lower co2 values during the mesozoic atmospheric oxygen shows a major broad late paleozoic peak with a maximum value of about 30 o2 in the permian a secondary less broad peak centered near the silurian devonian boundary variation between 15 and 20 o2 during the cambrian and ordovician a very sharp drop from 30 to 15 o2 at the permo triassic boundary and a more or less continuous rise in o2 from the late triassic to the present

p t x conditions on the genesis of orogenic au as bi ag deposit in metasedimentary rocks of the buracao area arai group brasilia fold belt brazil the orogenic au as bi ag mineralization up to 31 g t of the buracao area is hosted in the metasedimentary paleo mesoproterozoic trairas formation arai group brasilia fold belt brazil in order to discuss the p t x conditions that generated this mineralization we present mineralogical geochemical and fluid inclusion data of veins gold and wall rocks coupled with previous structural data these additional data allow us to link metamorphism and deformation with fluid migration and ore genesis the integration of fluid inclusion microthermometry with mineral geothermobarometers and structures show that rocks of the study area evolved from i syn d1a metamorphic peak 400 560 c 6 kbar through to the ii development of syn d1b type i barren veins from low salinity h2o nacl fluids during syn to late metamorphic peak and to the iii development of syn d2a type ii veins with the pyritic ore precipitation from low to high salinity h2o co2 ch4 nacl hco3 fluids during post metamorphic peak 345 285 c 2 7 1 6 kbar the high fineness gold nuggets accompanied by as bi and ag within pyrite arsenopyrite bismuthinite association in the pyritic ore allows the buracao area to be classified as a gold only orogenic ore deposit fluid inclusion compounds and the enrichment of as bi pb cu te se and ag in pyrite from the pyritic ore point out to metamorphism of carbonaceous phyllites and carbonate rocks of the trairas formation as a source for ore forming fluids we suggest that sulfur and gold in these fluids were derived by metamorphism of sedimentary rocks and conversion of pyrite into pyrrhotite in a metamorphic hydrothermal system the au hs 2 bearing fluids percolated along intrabasinal d2a regional shear zones through the trairas formation towards the buracao area where they precipitated type ii ore bearing veins within local structures the ore precipitation was induced by contrasting fo2 fs2 related to the interaction between the sulfur bearing fluid and host magnetite graphite phyllites the lithological control is represented by a series of reactions such as 2feo in silicates magnetite 4au hs 2 aq 4h aq 2fes2 s 4au s 4h2s aq 2h2o l the deposits of the buracao area and other orogenic gold deposits hosted in metasedimentary rocks in the brasilia fold belt and worldwide confirm the potential of ore genesis in zones that do not show any relation with meta igneous rocks thus expanding the exploration possibilities in metasedimentary successions

the diversification of paleozoic fire systems and fluctuations in atmospheric oxygen concentration by comparing silurian through end permian 250 million years myr charcoal abundance with contemporaneous macroecological changes in vegetation and climate we aim to demonstrate that long term variations in fire occurrence and fire system diversification are related to fluctuations in late paleozoic atmospheric oxygen concentration charcoal a proxy for fire occurs in the fossil record from the late silurian 420 myr to the present its presence at any interval in the fossil record is already taken to constrain atmospheric oxygen within the range of 13 to 35 the fire window herein we observe that as predicted atmospheric oxygen levels rise from 13 in the late devonian to 30 in the late permian so too fires progressively occur in an increasing diversity of ecosystems sequentially data of note include the occurrence of charcoal in the late silurian early devonian indicating the burning of a diminutive dominantly rhyniophytoid vegetation an apparent paucity of charcoal in the middle to late devonian that coincides with a predicted atmospheric oxygen low and the subsequent diversification of fire systems throughout the remainder of the late paleozoic first fires become widespread during the early mississippian they then become commonplace in mire systems in the middle mississippian in the pennsylvanian they are first recorded in upland settings and finally based on coal petrology become extremely important in many permian mire settings these trends conform well to changes in atmospheric oxygen concentration as predicted by modeling and indicate oxygen levels are a significant control on long term fire occurrence

nature and environmental significance of microbialites in quaternary reefs the tahiti paradox drill cores from the bamer reef edge of tahiti exhibit 85 93 m thick coralgal sequences recording at least 13 500 years of continuous reef growth in optimal environmental conditions the cored reef sequences form an overall shallowingupward succession with assemblages of branching or massive colonies of porires at the base overlain by a robust branching community acropom gr dmmi robirstn heavily encrusted by coralline algae sessile vermetid gastropods and arborescent foraminifers which grew at depths less than 6 m microbialites generally form the last stage of encrustation of coral colonies or more commonly of related encrusting organisms thus appearing as a major structural component of the reef sequence where they may locally form 809 of the rock by volume they developed in an open cavity system of the reef framework with freely circulating normal marine water microbialites include laminated crusts and clotted micritic masses commonly associated in compound crusts probably feflecting differences in the composition of the involved biological communities and in biomineralization processes that controlled the accretion of the crusts the isotopic composition of the microbialites 2 05 to 3 92 i they underwent also indivitlual processes of biominrlali2ation besicles the overall decrease in lizht and enqy conditions rttlecting progressive burial by conil growth the widespread development of microbialites within the reef framework may be related to increased alkalinity and niitrient availability in interstitial waters due to temstrial groundwwr seepage and puiodic runoffs the tlevelopment of micrubialites in the cryptic niches of the reef framework ceased about 6000 years

isotope reconstruction of plant palaeoecology case study of cenomanian floras from bohemia palaeoenvironments inferred from stable carbon isotope ratios of fossil plants collected from various environments of the cenomanian of bohemia were compared with palaeobotanical and sedimentological data to test the use of isotope ratios as a record of local palaeoenvironments and fossil plant ecology a number of isotope and biogeochemical patterns suggested that stable carbon isotope ratios in the cenomanian plants from bohemia have not been significantly affected by diagenesis stable carbon isotope ratios of the palaeoflora from one of the sections studied were used as a reference for a non stressed habitat since both sedimentological and palaeobotanical evidence suggested that the fossil flora underwent no environmental stresses that could have influenced its 13c values comparisons of 13c values of the other palaeofloras with that of the reference section allowed inference of the palaeoenvironmental stresses undergone by fossil plants these palaeoenvironmental patterns deduced from 13c 12c ratios are in agreement with the palaeoenvironments previously reconstructed by sedimentological and palaeobotanical studies combining evidence from those studies with isotope data provided detailed insights into the palaeoecology of the plants studied finally stable carbon isotope ratios allowed precise characterisation of the ecology of the best represented species of the deposits studied the ginkgoalean plant eretmophyllum obtusum and the conifer frenelopsis alata which were quite common in the salt marsh environments in europe during the cenomanian hence stable carbon isotope ratios can help in evaluating the environmental stresses undergone by fossil plants and the combination of these results with palaeobotanical and sedimentological data can provide detailed insights into fossil plant ecology

how earth s atmosphere evolved to an oxic state a status report the evolution of the earth s atmosphere is essentially the story of atmospheric oxygen virtually every realm of the earth sciences biology geology geochemistry oceanography and atmospheric science is needed to piece together an understanding of the history of oxygen over the past decade new data from these fields has shown that there were two significant increases in atmospheric o2 levels at around 2 4 2 3 and 0 8 0 6 billion years ago respectively throughout earth history oceanic sulfate concentrations appear to have increased in accord with greater o2 levels while levels of methane a strong greenhouse gas may have inversely mirrored o2 both oxic transitions occurred in eras characterized by bsnowball earthq events and significant disturbances in the carbon cycle perhaps associated with increases in o2 and losses of methane to understand what controlled the oxygenation of the atmosphere it is necessary to determine how o2 is consumed on geologic time scales through reaction with reductants released from the earth s crust and mantle there was apparently a long delay between the appearance of oxygenic photosynthesis and oxygenation of the atmosphere and a plausible explanation is that excess reductants scavenged photosynthetic o2 from the early atmosphere however a quantitative understanding of how and why o2 became abundant on our reducing planet is still lacking thus the study of the early atmosphere remains a frontier field with much to be discovered d 2005 elsevier b v all rights reserved

charcoal taphonomy and significance in geology botany and archaeology abstract charcoal occurs in the natural environment as either a result of wildfire or volcanic processes in addition people may make charcoal either for domestic or industrial use charcoal may be used as a fuel for domestic heating and cooking through a range of industrial uses such as iron smelting more recently the charcoalification process has been used to make biochar that is relatively inert and promotes atmospheric co 2 reduction with such a wide range of uses research has been published in a broad range of journals and often whole areas of study are unfamiliar to other charcoal researchers here we review a range of charcoal studies and their inter relationships we present some of the results of a major international meeting on charcoal brussels september 2008 highlighting the potential of charcoal studies as part of palaeoenvironmental investigations both in a geological and archaeological context

formation of gold deposits a metamorphic devolatilization model a metamorphic devolatilization model can explain the enrichment segregation timing distribution and character of many goldfields such as those found in archean greenstone belts slate belts and other gold only provinces in this genetic model hydrated and carbonated greenschist facies rocks particularly metabasic rocks are devolatilized primarily across the greenschist amphibolite facies boundary in an orogenic setting devolatilization operates on the scale of individual mineral grains extracting not just h2o and co2 but also s and in turn au elevated gold in solution is achieved by complexing with reduced s and by h2co3 weak acid buffering near the optimal fluid ph for gold solubility the buffering is more important than being at the point of maximum gold solubility low salinity ensures low base metal concentrations in the auriferous metamorphic fluid migration of this fluid upwards is via shear zones and or into hydraulic fracture zones in rocks of low tensile strength the geometry of the shear zones dictates the kilometre scale fluid migration paths and the degree of fluid focusing into small enough volumes to form economic accumulations of gold deposition of gold from solution necessitates breakdown of the gold thiosulphide complex and is especially facilitated by fluid reduction in contact with reduced carbon bearing host rocks and or by sulphidation of wallrocks to generate iron bearing sulphide and precipitated gold as such black slate carbon seams banded iron formation tholeiitic basalt magnetite bearing diorite and differentiated tholeiitic dolerite sills are some of the important hosts to major goldfields gold deposition is accompanied by carbonation sulphidation and muscovite biotite alteration where the host rock is of suitable bulk composition the correlation of major gold deposits with rock type even when the gold is primarily in veins argues for rock dominated depositional systems not fluid dominated ones as a consequence a general role in gold deposition for fluid mixing temperature decrease and or fluid pressure decrease and boiling is unlikely although such effects may be involved locally several geological features that are recorded at gold only deposits today reflect subsequent modifications superimposed upon the products of this generic metamorphic devolatilization process overprinting by higher grade metamorphism and deformation and or palaeo weathering may provide many of the most obvious features of goldfields including their mineralogy geochemistry geometry small scale timing features geophysical response and even mesoscopic gold distribution

three growth in the mesozoic and early tertiary and the reconstruction of palaeoclimates abstract evidence from the distribution and characteristics of fossil wood in the mesozoic and early tertiary indicates that a much warmer global climate prevailed in those times there appears to have been a broad zone of largely non seasonal climate stretching from about 32 n to 32 s palaeolatitudes in addition to this low latitude zone forest growth extended into very high palaeolatitudes where trees cannot grow at the present day a number of theories have been proposed to account for the palaeoclimate responsible for this distribution of forests most notable have been those involving changes in the amount of carbon dioxide in the atmosphere in the positions of the continents or in the obliquity of the earth s axis of rotation evidence from fossil forests indicates that a combination of the effects of an increased quantity of carbon dioxide in the atmosphere and the palaeopositions of the continents in the mesozoic and early tertiary appears at the moment to be the simplest explanation for the climate of those geological times without the need to invoke axial movement

paleoecology biogeography and evolution of reef ecosystems in the panthalassa ocean during the late triassic insights from reef limestone of the sambosan accretionary complex shikoku japan upper triassic reefs from the panthalassa ocean have been understudied in comparison to their tethyan counterparts and are therefore pivotal to understanding the global reef evolution during the late triassic to fill this gap upper triassic reef limestone from ten localities of the sambosan accretionary complex at shikoku island japan has been investigated biotic assemblages quantitative microfacies analysis and integrated biostratigraphy allow us to characterize two types of reefs those attributed to the ladinian early carnian and those attributed to the late carnian rhaetian at the regional scale our data refine the biostratigraphic framework of the upper triassic sambosan limestone at the global scale multivariate analyses support a strong paleobiogeographic affinity of the western panthalassa reef biota with those of the south tethys ocean during the ladinian carnian and norian rhaetian additionally they indicate connections with east panthalassa reefs during the norian rhaetian

the rise of fire fossil charcoal in late devonian marine shales as an indicator of expanding terrestrial ecosystems fire and atmospheric change fossil charcoal provides direct evidence for fire events that in turn have implications for the evolution of both terrestrial ecosystems and the atmosphere most of the ancient charcoal record is known from terrestrial or nearshore environments and indicates the earliest occurrences of fire in the late silurian however despite the rise in available fuel through the devonian as vascular land plants became larger and trees and forests evolved charcoal occurrences are very sparse until the early mississippian where extensive charcoal suggests well established fire systems we present data from the latest devonian and early mississippian of north america from terrestrial and marine rocks indicating that fire became more widespread and significant at this time this increase may be a function of rising o2 levels and the occurrence of fire itself may have contributed to this rise through positive feedback recent atmospheric modeling suggests an o2 low during the middle devonian around 17 5 with o2 rising steadily through the late devonian and early mississippian to 21 22 that allowed for widespread burning for the first time in devonian mississippian marine black shales fossil charcoal inertinite steadily increases up section suggesting the rise of widespread fire systems there is a concomitant increase in the amount of vitrinite preserved woody and other plant tissues that also suggests increased sources of terrestrial organic matter even as end devonian glaciation was experienced fossil charcoal continued to be a source of organic matter being introduced into the devonian oceans scanning electron and reflectance microscopy of charcoal from late devonian terrestrial sites indicate that the fires were moderately hot typically 500 600 c and burnt mainly surface vegetation dominated by herbaceous zygopterid ferns and lycopsids rather than being produced by forest crown fires the occurrence and relative abundance of fossil charcoal in marine black shales are significant in that these shales may provide a more continuous record of fire than is preserved in terrestrial environments our data support the idea that major fires are not seen in the fossil record until there is both sufficient and connected fuel and a high enough atmospheric o2 content for it to burn