extreme warming of tropical waters during the paleocene eocene thermal maximum the paleocene eocene thermal maximum petm ca 56 ma was a major global environmental perturbation attributed to a rapid rise in the concentration of greenhouse gases in the atmosphere geochemical records of tropical sea surface temperatures ssts from the petm are rare and are typically affected by post depositional diagenesis to circumvent this issue we have analyzed oxygen isotope ratios 18o of single specimens of exceptionally well preserved planktonic foraminifera from the petm in tanzania 19 s paleolatitude which yield extremely low 18o down to 3 c during the petm and may have exceeded 40 c calcareous plankton are absent from a large part of the tanzania petm record extreme environmental change may have temporarily caused foraminiferal exclusion

from greenhouse to icehouse organic walled dinoflagellate cysts as paleoenvironmental indicators in the paleogene abstract dinoflagellates are an important component of the extant eukaryotic plankton their organic walled hypnozygotic cysts dinocysts provide a rich albeit incomplete history of the group in ancient sediments building on pioneering studies of the late 1970s and 1980s recent drilling in the southern ocean has provided a wealth of new dinocyst data spanning the entire paleogene such multidisciplinary studies have been instrumental in refining existing and furnishing new concepts of paleogene paleoenvironmental and paleoclimatic reconstructions by means of dinocysts because dinocysts notably exhibit high abundances in neritic settings dinocyst based environmental and paleoclimatic information is important and complementary to the data derived from typically more offshore groups as planktonic foraminifera coccolithophorids diatoms and radiolaria by presenting case studies from around the globe this contribution provides a concise review of our present understanding of the paleoenvironmental significance of dinocysts in the paleogene 65 25 ma representing earth s greenhouse icehouse transition this episode holds the key to the understanding of extreme transient climatic change we discuss the potential of dinocysts for the reconstruction of paleogene sea surface productivity temperature salinity stratification and paleo oxygenation along with their application in sequence stratigraphy oceanic circulation and general watermass reconstructions

well preserved palaeogene and cretaceous biomarkers from the kilwa area tanzania we have investigated the biomarker composition of sediments ranging in age from 30 to 70 ma from the kilwa area of tanzania they are dominated by material of terrestrial n alkanols n alkanoic acids n alkanes and triterpenoids and bacterial hopanoids and a dipentadecyl glycerol diether dgd origin with only a minor contribution of marine origin crenarchaeol and some algal steroids this indicates a marine setting dominated by higher plant input which most likely stimulated sedimentary microbial activity including sulfate reduction the lipid composition specifically the presence of bacteriohopanepolyols bhps and the stereochemistry of hopanoids suggests a low degree of thermal maturity many biomarkers have still retained functionality even after 30 70 million years this is in good agreement with the exceptional preservation of foraminifera and nannofossils and can probably be attributed to the very low sediment permeability and burial depth there is a clear distinction in the biomarker distributions between the oligocene age sediments collected at the end of the peninsula near kilwa masoko and the older sediments collected from elsewhere indicating differences in depositional environment sediments from the end of the peninsula have higher branched and isoprenoid tetraether index values indicating a relatively higher terrestrial input they also contain two tentatively assigned c28 hopenes 28 30 dinorneohop 13 18 ene and 28 30 dinorhop 17 21 ene aromatic des a triterpenes des e hopenes aromatic pentacyclic triterpenoids c33 dgd archaeol and bhps which are absent from or only present in small amounts in the other sediments these differences likely reflect an evolution of the depositional area from a relative open shelf environment with substantial water depth to a shallower setting during the early oligocene

atmospheric pco2 since 60 ma from records of seawater ph calcium and primary carbonate mineralogy a 60 m y record of atmospheric p co2 has been refined from knowledge of 1 secular changes in the major ion composition of seawater particularly ca and mg and 2 oscillations in the mineralogy of primary oceanic carbonate sediments both factors have had a significant impact on the chemistry of the ocean carbonate buffer system calculated atmospheric p co2 oscillated between values of 100 300 ppm and to maxima of 1200 2500 ppm from 60 to 40 ma and varied between 100 and 300 ppm from 25 ma to the present the refined p co2 values are significantly lower than previous estimates made from seawater ph data where total dissolved inorganic carbon was assumed constant and more in line with modeling and stomatal index estimations of atmospheric p co2 for the tertiary

diagenetic and catagenetic products of isorenieratene molecular indicators for photic zone anoxia a wide range of novel diagenetic and catagenetic products of the diaromatic carotenoid isorenieratene a pigment of the photosynthetic green sulphur bacteria chlorobiaceae has been identified in a number of sedimentary rocks ranging from ordovician to miocene compound identification is based on nmr mass spectrometry the presence of atropisomers and stable carbon isotopes atropisomers contain an axially chiral centre which in combination with other chiral centres results in two or more diastereomers that can be separated on a normal gc column chlorobiaceae use the reverse tca cycle to fix carbon so that their biomass is enriched in 13c high 13c contents of isorenieratene derivatives therefore support their inferred origins isorenieratene derivatives include c 40 c 33 and c 32 diaryl isoprenoids and short chain aryl isoprenoids with additional aromatic and or s containing rings c 33 and c 32 compounds are diagenetic products of c 33 and c 32 carotenoids formed from isorenieratene during early diagenesis through expulsion of toluene and m xylene respectively cyclisation of the polyene acyclic isoprenoid chain can proceed via an intramolecular diels alder reaction followed by aromatisation of the newly formed ring sulphurisation is also an important process during early diagenesis competing with expulsion and cyclisation sulphur bound isorenieratane is released during progressive diagenesis due to cleavage of relatively weak ss and cs bonds cleavage of c c bonds during aromatisation of newly formed rings and during catagenesis yields short chain compounds the inherent presence of a conjugated double bond system in carotenoids implies that similar diagenetic and catagenetic reactions can occur with all carotenoids chlorobiaceae live at or below the oxic anoxic boundary layer and require both light and h 2s the presence of isorenieratene or its diagenetic and catagenetic products in ancient sedimentary rocks and crude oils is therefore an excellent indication for photic zone anoxia in the depositional environment diagenetic and catagenetic products of isorenieratene are expected to find applications in reconstruction of palaeoenvironments and in oil oil and oil source rock correlation studies their presence in several petroleum source rocks suggests that anoxia is an important environmental parameter for the preservation of organic matter

late eocene to early oligocene dinoflagellate cysts from the priabonian type area northeast italy biostratigraphy and paleoenvironmental interpretation abstract marginal marine late eocene through early oligocene dinoflagellate cyst successions have been studied from the type area of the priabonian stage northeast italy the results allow the recognition of dinoflagellate zones previously defined in bio and magnetostratigraphically well calibrated pelagic sequences from central italy thus providing a first order correlation of the priabonian stage to the standard chronostratigraphic scale with unprecedented precision within this detailed biostratigraphic framework successive shifts in the composition of the dinoflagellate cyst assemblages are interpreted in terms of sea level and sea surface temperature sst fluctuations the evaluation of ecologically and sedimentary controlled changes in the composition of dinoflagellate cyst assemblages in combination with sequence stratigraphic analysis allows the reconstruction of third and fourth order sea level fluctuations the third order sea level fluctuations appear to correspond to exxon cycles ta4 1 4 5 the stratigraphically and palaeoenvironmentally important late eocene dinoflagellate cyst species glaphyrocysta priabonensis sp nov is formally described

evidence for annual records of phytoplankton productivity in the kimmeridge clay formation coccolith stone bands upper jurassic dorset uk the upper jurassic kimmeridge clay formation is a c org rich sequence of mudrocks that was deposited in a dysoxic basin which served unusually to preserve primary coccolithophorid proportions strikingly contrasting within this dark coloured formation are the white coccolith stone bands which contain pristinely preserved coccolithophorid assemblages preserving potentially primary coccolithophorid abundances with minimal diagenetic alteration using methodology described herein scanning electron microscopy sem observation of mum scale laminae within selected stone bands has revealed five distinctive types of microlamina type 1 being barren clay type 2 comprising coccoliths associated with varying amounts of clay or amorphous organic matter type 3 being purely coccolithic type 4 being of putative microbial origin and type 5 containing frequent calcispheres these are all described and illustrated here illustrated sequences of these are discussed with reference to an hypothetical model sequence based on modem records representing a kimmeridgian year of coccolithophorid productivity annual signals are thus interpreted based on the observations presented here and including summaries of the palynomorph records from the stone bands we comment on watznaueriacean palaeoecology and particularly the interpretation of watznaueria fossacincta barnesiae as an opportunistic growth maximising taxon c 2004 elsevier b v all rights reserved

marked decline in atmospheric carbon dioxide concentrations during the paleogene the relation between the partial pressure of atmospheric carbon dioxide pco2 and paleogene climate is poorly resolved we used stable carbon isotopic values of di unsaturated alkenones extracted from deep sea cores to reconstruct pco2 from the middle eocene to the late oligocene approximately 45 to 25 million years ago our results demonstrate that pco2 ranged between 1000 to 1500 parts per million by volume in the middle to late eocene then decreased in several steps during the oligocene and reached modern levels by the latest oligocene the fall in pco2 likely allowed for a critical expansion of ice sheets on antarctica and promoted conditions that forced the onset of terrestrial c4 photosynthesis

examining possible effects of seawater ph decline on foraminiferal stable isotopes during the paleocene eocene thermal maximum 1 a large body of paleoceanographic data for the paleocene eocene thermal maximum petm is based on foraminiferal stable carbon and oxygen isotope composition 13c and 18o however the proxy records could be biased due to a ph effect on stable isotopes during times when the ocean became more acidic as has been demonstrated for modern planktonic foraminifera in this paper we calculate the possible ranges of the ph effect on 13c and 18o during the petm based on the relative ph decline ph from the preperturbation steady state simulated by a carbon cycle model and the empirical relationships obtained from culture experiments with planktonic foraminifera the model is configured with eocene paleogeography and simulates ph for surface intermediate and deep water in the major ocean basins in response to various carbon input scenarios 2000 to 5000 pg c for an array of scenarios the modeled ph of the surface ocean ranges from 0 1 to 0 28 units this suggests that 13c of planktonic foraminifera may be increased by up to 2 1 and 18o may be increased by up to 0 7 corresponding to over 3 c error in paleotemperature estimate under conditions in which the model best simulates the global caco3 dissolution pattern we find marked differences in the deep sea ph between the atlantic 0 4 and pacific oceans 0 1 this would imply that the magnitude of the negative 13c and 18o excursions of benthic foraminifera in the atlantic ocean was dampened by up to 2 8 and 0 9 at maximum respectively relative to a constant ph scenario

reevaluation of the oxygen isotopic composition of planktonic foraminifera experimental results and revised paleotemperature equations cultured planktonic foraminifera orbulina universa symbiotic and globigerina bulloides nonsymbiotic are used to reexamine temperature 18o relationships at 15 25 c relationships for both species can be described by linear equations equations for o universa grown under low light ll and high light hl share a slope of 4 80 0 21 c 1 with a hl ll offset of 0 33 due to symbiont photosynthetic activity the effect of co32 on o universa is 0 002 mol 1 kg 1 and is insensitive to temperature for g bulloides ontogenetic effects produce size related trends in temperature 18o whereby larger shells are enriched in 18o relative to smaller specimens the o universa temperature 18o relationships are more accurate than previously published equations for describing plankton tow data our equations do not explain planktonic core top data with the same precision but provide a good fit to benthic cibicidoides data below 10 c temperature 18o relationships for g bulloides provide good agreement with field data for this species from the northeast pacific

permeability measurements in mudrocks using gas expansion methods on plug and crushed rock samples abstract permeability is an important parameter relative to the production of hydrocarbons in shale oil gas plays however the measurement of permeability in these nano to microdarcy rocks remains a challenge results from different methods or from different laboratories are not consistent and reasons are not fully understood in the present study permeability is measured for both plug and crushed rock samples with different plug diameter or crushed sample particle size to systematically investigate the permeability measurement to better understand and apply the measured results a modified gas expansion mge method which can measure permeability for plug samples under confining pressures was established and applied to several eagle ford and barnett shale mudrock samples permeability results from this method are in fair agreement with those from the pulse decay method the traditional gas research institute gri method was applied to crushed rock eagle ford shale samples the results were comparable to reported permeability for an eagle ford shale sample particle or plug size has significant influence on permeability measurement in general permeability increases with increasing particle or plug size for crushed sample with gri method the reason of increasing permeability is related to the limitation of the gri technique and the data analysis method estimate of the permeability based on kozeny carman equation was conducted and the results were used to evaluate the gri permeability measurement particle size of 2 4 mm 5 10 meshes is considered as an appropriate size for gri permeability measurement for plug sample larger permeability with larger plug diameter is most likely caused by the artificial fractures higher confining pressure can reduce the influence of the fractures but cannot fully remove it a range of permeability defined by the gri permeability with 2 4 mm particles as the lower boundary and permeability of 1 in plug under high confining pressure 5000 psi as the upper boundary can be a more reliable measures to represent the shale matrix permeability the range of the permeability also highlights the uncertainty in matrix permeability measurement for shale

laboratory characterization of the porosity and permeability of gas shales using the crushed shale method insights from experiments and numerical modelling gas production from shale resource plays has transformed the usa energy market despite the knowledge gained from the analysis of large amounts of shale core appraisal of shale gas resource plays requires a large number of wells to be drilled and tested ideally core analysis results would provide an indication of both the gas filled porosity and permeability of shale resource plays which could then be used to reduce the number of wells needed during appraisal a combination of laboratory experiments numerical modelling and a round robin test have been conducted to assess the validity of the crushed shale method csm which has been widely used in industry to assess the porosity and permeability of shale the results suggest that the csm can provide reasonably precise estimates of porosity measured at ambient stress if a standard sample cleaning method is adopted although a reliable method to correct these values to subsurface conditions needs to be developed the csm does not however appear to provide useful information on shale permeability a round robin test shows that differences of up to four orders of magnitude in permeability were provided by different laboratories when analysing the same sample these huge differences seem to occur due to a combination of errors in calculating permeabilities from pressure transients differences in the way that permeability is calculated as well as uncertainties regarding the effective size of crushed shale particles however even if standardized the csm may not be particularly useful for characterizing the flow capacity of shale because it is insensitive to the presence of high permeability zones that would control flow in the subsurface

similarities between planktonic and larger foraminiferal evolutionary trends through paleogene paleoceanographic changes abstract the paleogene evolutionary records of planktonic foraminifera and larger benthic foraminifera show parallel patterns in development that may in part reflect changes in nutrient flux to surface waters following the terminal cretaceous extinctions faunas were dominated by a few cosmopolitan opportunistic species more specialized k strategists in both groups diversified during the paleocene dominating into the early eocene consistent with he globally mild climatic regime and probable limited rates of nutrient flux to surface waters high latitude cooling intensified in the middle eocene promoting diversification of less specialized taxa characteristic of cooler and deeper waters higher latitudes meridional upwelling zones and boundary currents geographic ranges of warm water taxa diminished and fragmented yet many species survived thus global diversities during the middle eocene were the highest in the cenozoic as cooling and increased rates of nutrient flux further intensified in the late eocene extinction rates of warm water planktonic and larger benthic species exceeded origination rates of cooler water and less specialized forms so diversity dropped to intermediate levels where it remained through the late eocene and oligocene previous observations that planktonic foraminiferal faunas dominated by warm water taxa are often replaced by cool water faunas even though oxygen isotopes only recorded relatively minor cooling can be reconciled by the explanation that the biotic communities responded to changes in trophic resources and euphotic habitats that accompany the temperature reduction as well as to temperature change itself

a novel proxy for terrestrial organic matter in sediments based on branched and isoprenoid tetraether lipids we propose a novel tracer for terrestrial organic carbon in sediments based on the analysis of tetraether lipids using high performance liquid chromatography mass spectrometry hplc ms analysis of terrestrial soil and peats shows that branched tetraether lipids are predominant in terrestrial environments in contrast to crenarchaeol the characteristic membrane lipid of non thermophilic crenarchaeota which is especially abundant in the marine and lacustrine environment based on these findings an index was developed the so called branched and isoprenoid tetraether bit index based on the relative abundance of terrestrially derived tetraether lipids versus crenarchaeol this bit index was applied to surface sediments from the angola basin where it was shown to trace the outflow of the congo river furthermore analyses of particulate organic matter from the north sea showed relatively higher bit indices in water column particulate organic matter near large river inputs a survey of globally distributed marine and lacustrine surface sediments shows that the bit index in these environments correlates with the relative fluvial input of terrestrial organic material making this index generally applicable the new proxy allows the rapid assessment of the fluvial input of terrestrial organic material in immature sediments up to 100 ma old

estimating permeability of shale gas reservoirs from porosity and rock compositions it is challenges for effectively estimating the permeability of shale gas reservoirs by traditional models however the study on this area is lacked and deficient we proposed a method for predicting permeability of shale gas reservoirs from porosity and rock compositions including mineralogy and organic matter content which is applicable to laboratory data and downhole measurements first two sets including 38 samples from the longmaxi formations were tested for porosity permeability grain density total organic carbon toc content mineralogical compositions and low temperature nitrogen adsorption we used the kozeny s equation to calculate the specific surface area which was viewed as the effective specific surface in shale formations through comparing with the specific surface from low temperature nitrogen adsorption further the effective specific surface was found to be positively correlated with clays pyrite and toc contents while negatively with quartz feldspar and carbonates then an

response of larger benthic foraminifera to the paleocene eocene thermal maximum and the position of the paleocene eocene boundary in the tethyan shallow benthic zones evidence from south tibet

abrupt deep sea warming palaeoceanographic changes and benthic extinctions at the end of the palaeocene a remarkable oxygen and carbon isotope excursion occurred in antarctic waters near the end of the palaeocene 57 33 myr ago indicating rapid global warming and oceanographic changes that caused one of the largest deep sea benthic extinctions of the past 90 million years in contrast the oceanic plankton were largely unaffected implying a decoupling of the deep and shallow ecosystems the data suggest that for a few thousand years ocean circulation underwent fundamental changes producing a transient state that although brief had long term effects on environmental and biotic evolution

the palaeocene eocene carbon isotope excursion constraints from individual shell planktonic foraminifer records the palaeocene eocene thermal maximum petm is characterized by a global negative carbon isotope excursion cie and widespread dissolution of seafloor carbonate sediments the latter feature supports the hypothesis that the petm and cie were caused by the rapid release of a large mass greater than 2000gt c of 12c enriched carbon the source of this carbon however remains a mystery possible sources include volcanically driven thermal combustion of organic rich sediment dissociation of seafloor methane hydrates and desiccation and oxidation of soil sediment organics a key constraint on the source s is the rate at which the carbon was released fast rates would be consistent with a catastrophic event e g massive methane hydrate dissociation whereas slower rates might implicate other processes the petm carbon flux is currently constrained by high resolution marine and terrestrial records of the cie in pelagic bulk carbonate records the onset of the cie is often expressed as a single or multiple step excursion extending over 10 4 years individual planktonic shell records in contrast always show a single step cie with either pre excursion or excursion isotope values but no transition values benthic foraminifera records which are less complete owing to extinction and diminutive assemblages show a delayed excursion here we compile and evaluate the individual planktonic shell isotope data from several localities we find that the most expanded records consistently show a bimodal isotope distribution pattern regardless of location water depth or depositional facies this suggests one of several possibilities i the isotopic composition of the surface ocean atmosphere declined in a geologic instant 500yr ii that during the onset of the cie most shells of mixed layer planktonic foraminifera were dissolved or iii the abundances or shell production of these species temporarily declined possibly due to initial ph changes

conflicting isotopic and biotic evidence for tropical sea surface temperatures during the tertiary abstract the biotic evidence from a varied group of shallow water organisms including mangroves zooxanthellate corals mainly reefal and larger foraminifera suggests that sea surface temperatures at low latitudes during the tertiary from at least the early eocene to the middle miocene were subtropical to tropical in nature and similar to temperatures prevailing at low latitudes at the present day 20 28 c in a recent paper shackleton 1984 the suggestion is made on the basis of oxygen isotope studies of foraminiferal shells that low latitude sea surface temperatures during the palaeogene and much of the neogene were invariably lower than those in similar regions today with a stable temperature of around 18 c this paper discusses the conflicting evidence for sea surface temperatures obtained from palaeontological and isotopic sources and suggests that palaeotemperatures derived from some isotopic studies are too low to account for the distribution and diversity of many tertiary tropical and subtropical biotas

development of organic porosity in the woodford shale with increasing thermal maturity abstract using a combination of focused ion beam milling and scanning electron microscopy we describe the evolution of secondary organic porosity in eight woodford shale late devonian early mississippian samples with mean random vitrinite reflectance values ranging from 0 51 ro to 6 36 ro organic porosity was observed to be absent in samples with vitrinite reflectance values of up to 0 90 ro with the first appearance of secondary pores starting with the 1 23 ro sample porosity in the organic matter was unexpectedly absent in a sample with a vitrinite reflectance of 2 00 ro however organic pores were again found in samples with higher thermal maturities porosity when present did not appear to be uniformly distributed among the organic matter that was within less than a micron of each other suggesting important differences in composition of the organic matter thin regions of organic matter were observed between grains raising the possibility that small amounts of the deposited organic matter were compacted between grains to form thin layers and or the structures are part of the secondary organic matter interpreted to be post oil bitumen which was left behind as a residue during oil migration through the shale some regions of porous organic matter appeared to be grain protected whereas others did not which indicates that these non protected porous organic regions may be stress supporting with porosity intact under in situ reservoir conditions these observations suggest that thermal maturity alone is insufficient to predict porosity development in organic shales and other factors such as organic matter composition complicate porosity development

experimental investigation of matrix permeability of gas shales predicting long term production from gas shale reservoirs has been a major challenge for the petroleum industry to better understand how production profiles are likely to evolve with time we have conducted laboratory experiments examining the effects of confining stress and pore pressure on permeability experiments were conducted on intact core samples from the barnett eagle ford marcellus and montney shale reservoirs the methodology used to measure permeability allows us to separate the reduction of permeability with depletion because of the resultant increase in effective confining stress and the increase in permeability associated with knudsen diffusion and molecular slippage also known as klinkenberg effects at very low pore pressure by separating these effects we are able to estimate the relative contribution of both darcy and diffusive fluxes to total flow in depleted reservoirs our data show that the effective permeability of the rock is significantly enhanced at very low pore pressures because of the slippage effects we use the magnitude of the klinkenberg effect to estimate the effective aperture of the flow paths within the samples and compare these estimates to scanning electron microscopy image observations our results suggest effective flow paths to be on the order from tens of nanometers in most samples to 100 200 nm in a relatively high permeability eagle ford sample finally to gain insight on the scale dependence of permeability measurements the same core plugs were crushed and permeability was again measured at the particle scale using the so called gas research institute method the results show much lower permeability than the intact core samples with very little correlation to the measurements on the larger scale cores

reconstruction of sea surface conditions at middle to high latitudes of the northern hemisphere during the last glacial maximum lgm based on dinoflagellate cyst assemblages abstract a new calibration database of census counts of organic walled dinoflagellate cyst dinocyst assemblages has been developed from the analyses of surface sediment samples collected at middle to high latitudes of the northern hemisphere after standardisation of taxonomy and laboratory procedures the database comprises 940 reference data points from the north atlantic arctic and north pacific oceans and their adjacent seas including the mediterranean sea as well as epicontinental environments such as the estuary and gulf of st lawrence the bering sea and the hudson bay the relative abundance of taxa was analysed to describe the distribution of assemblages the best analogue technique was used for the reconstruction of last glacial maximum lgm sea surface temperature and salinity during summer and winter in addition to sea ice cover extent at sites from the north atlantic n 63 mediterranean sea n 1 and eastern north pacific n 1 three of the north atlantic cores from the continental margin of eastern canada revealed a barren lgm interval probably because of quasi permanent sea ice six other cores from the greenland and norwegian seas were excluded from the compilation because of too sparse assemblages and poor analogue situation at the remaining sites n 54 relatively close modern analogues were found for most lgm samples which allowed reconstructions the new lgm results are consistent with previous reconstructions based on dinocyst data which show much cooler conditions than at present along the continental margins of canada and europe but sharp gradients of increasing temperature offshore the results also suggest low salinity and larger than present contrasts in seasonal temperatures with colder winters and more extensive sea ice cover whereas relatively warm conditions may have prevailed offshore in summer from these data we hypothesise low thermal inertia in a shallow and low density surface water layer

effective stress history and the potential for seismicity associated with hydraulic fracturing of shale reservoirs the influence of effective stress history on reservoir stability and the response to hydraulic fracturing are simulated for two hypothetical shale reservoirs it is numerically demonstrated that the effective stress history influences the present day stability of faults and natural fractures any assumption of a homogeneous stress state is shown to be unrealistic in the majority of fractured shale reservoirs the simulations demonstrate that depending upon the effective stress history shear displacements can be induced by stress changes associated with stimulation without a change of fluid pressure in the destabilized fractures elastoplastic shale and other fractured reservoirs are shown to have a memory of past geomechanical states these numerical findings demonstrate the value of interpreting reservoir effective stress history when planning fluid injection a previous case history is summarized to illustrate the overwhelming dependence of stress history analyses on a wide spectrum of earth science disciplines it also illustrates the application of stress history analyses to activities other than hydraulic fracturing the current inexperience of effective stress history description means that new approaches must be identified to optimize the necessary multidisciplinary investigations supplementary material details of the simulations are available at www geolsoc org uk sup18743

eocene circulation of the southern ocean was antarctica kept warm by subtropical waters 1 near the eocene s close 34 million years ago the climate system underwent one of the largest shifts in earth s history antarctic terrestrial ice sheets suddenly grew and ocean productivity patterns changed previous studies conjectured that poleward penetration of warm subtropical currents the east australian current eac in particular caused eocene antarctic warmth late eocene opening of an ocean gateway between australia and antarctica was conjectured to have disrupted the eac cooled antarctica and allowed ice sheets to develop here we reconstruct eocene paleoceanographic circulation in the tasmanian region using 1 biogeographical distributions of phytoplankton including data from recently drilled ocean drilling program leg 189 sites and 2 fully coupled climate model simulations we find that the eac did not penetrate to high latitudes and ocean heat transport in the region was not greater than modern our results do not support changes in thermal isolation as the primary driver of the eocene oligocene climatic transition

the trace metal content of recent organic carbon rich sediments implications for cretaceous black shale formation organic carbon rich sediments are enriched in several redox sensitive and stable sulfide forming trace metals tm and form an important sink in global tm cycles in today s ocean such sediments are deposited in coastal upwelling areas like those in the gulf of california off peru or off the namibian coast and euxinic basins like the black sea in an attempt to distinguish both environments by their specific tm patterns some important conclusions may be drawn 1 the tm enrichment seen in both environments broadly is rather similar 2 upwelling sediments are often enriched in cd and p and depleted in co and mn 3 sapropels have a tendency towards higher enrichments in ba and mo s re as cu ni sb and fe reflecting the strong sulfidation in an anoxic water column 4 upwelling systems cover a broad range of environmental settings where the steepness of the slope the proximity of h2s to the sediment seawater interface and the intensity of bio accumulation and regeneration play an important role for tm accumulation 5 the tm content of anoxic basins is mainly controlled by tm availability in the water column and sedimentation rate 6 enhanced bio productivity is the main switch turning an oxygenated into an anoxic environment cretaceous black shales oae 2 exhibit tm signatures of both coastal upwelling areas and sapropels the strong enrichments in cd mo tl v cu ni bi and sb demonstrate that bio accumulation and presence of h2s in the water column and associated sulfidation processes persisted during this time interval in large parts of the proto atlantic the usefulness of ba as a paleoproductivity proxy is obscured by diagenesis the extreme accumulation in ag and zn requires either an additional tm source for instance hydrothermal input or a different tm seawater composition during the cretaceous the geochemical data suggest that the major driving force for the widespread occurrence of c t black shales seems to be the increase in volcanic activity and associated co2 input throughout the cretaceous the ocean atmosphere system operated in a mode different from today during this time interval after conversion of the nutrient co2 into organic matter the system switched back into the normal operational mode

response of antarctic odp site 690 planktonic foraminifera to the paleocene eocene thermal maximum faunal evidence for ocean climate change 1 high resolution study of antarctic planktonic foraminiferal assemblages ocean drilling program site 690 weddell sea shows that these microplankton underwent a stepwise series of changes during the paleocene eocene thermal maximum petm initiation of this response coincides with the onset of the carbon isotope excursion cie but precedes the benthic foraminiferal mass extinction the top to bottom succession in the biotic response indicates that the surface ocean atmosphere was affected before the deep sea the earliest stage of the faunal response entailed a conspicuous turnover within the shallow dwelling genus acarinina and a succession of stratigraphic first appearances the genus morozovella large 180 m biserial planktonics and a wilcoxensis are all restricted to the lower cie within this petm section acarininid populations crashed as the ocean climate system ameliorated during the cie recovery reflecting atypical surface water conditions this transient decline in acarininids is paralleled by a marked increase in carbonate content of sediments it is postulated that this interval of carbonate enrichment and its unusual microfauna reflects enhanced carbon storage within reservoirs of the global carbon cycle other than the marine carbonate system sensu broecker et al 1993 ravizza et al 2001

changes in the hydrological cycle in tropical east africa during the paleocene eocene thermal maximum the paleocene eocene thermal maximum petm at ca 55 8 ma is one of the most studied instances of past greenhouse gas induced global warming as such it provides a rich opportunity to examine the impact of such global change on local climates the effects of increased continental and sea surface temperatures on local precipitation and humidity during the petm remain poorly constrained and studies reveal complex regional differences whilst some localities appear to experience a net increase in humidity others exhibit the opposite crucially there are few records of hydrological change from tropical regions recent onshore drilling expeditions in tanzania have yielded expanded sedimentary sections deposited in a marine environment that span much of the late cretaceous and paleogene and show exceptionally good preservation of both calcareous microfossils and organic matter the petm interval has previously been constrained by both biostratigraphy and carbon isotopic records and spans ca 7 m of section lipid distributions including various terrestrial marine and bacterial biomarkers and their hydrogen isotopic compositions as well as mineralogy were used to examine east african vegetation and hydrological responses to the global change occurring at the petm although total organic carbon contents decrease the concentrations of both higher plant n alkanes n alkanoic acids and soil bacterial glycerol dialkyl glycerol tetraethers biomarkers increase dramatically at the onset of the petm negative carbon isotope excursion cie suggesting an increased discharge of fluvial sedimentary organic matter similarly mineralogical indicators of terrestrial input including ti al and si al ratios quartz contents and notably the proportion of kaolinite also increase at the onset of the cie however higher plant leaf wax n alkanes c27 c29 and c31 become more deuterium enriched throughout the same interval suggesting a more arid and or hotter rather than a more humid environment this evidence collectively suggests an east african early petm climate characterised by overall hot and arid conditions punctuated by intense perhaps seasonal precipitation events these data match observations from other locations at mid latitudes suggesting that the humid climate often suggested for the petm was not globally widespread

synchronous tropical and polar temperature evolution in the eocene palaeoclimate reconstructions of periods with warm climates and high atmospheric co2 concentrations are crucial for developing better projections of future climate change deep ocean1 2 and high latitude3 palaeotemperature proxies demonstrate that the eocene epoch 56 to 34 million years ago encompasses the warmest interval of the past 66 million years followed by cooling towards the eventual establishment of ice caps on antarctica eocene polar warmth is well established so the main obstacle in quantifying the evolution of key climate parameters such as global average temperature change and its polar amplification is the lack of continuous high quality tropical temperature reconstructions here we present a continuous eocene equatorial sea surface temperature record based on biomarker palaeothermometry applied on atlantic ocean sediments we combine this record with the sparse existing data4 6 to construct a 26 million year multi proxy multi site stack of eocene tropical climate evolution we find that tropical and deep ocean temperatures changed in parallel under the influence of both long term climate trends and short lived events this is consistent with the hypothesis that greenhouse gas forcing7 8 rather than changes in ocean circulation9 10 was the main driver of eocene climate moreover we observe a strong linear relationship between tropical and deep ocean temperatures which implies a constant polar amplification factor throughout the generally ice free eocene quantitative comparison with fully coupled climate model simulations indicates that global average temperatures were about 29 26 23 and 19 degrees celsius in the early early middle late middle and late eocene respectively compared to the preindustrial temperature of 14 4 degrees celsius finally combining proxy and model based temperature estimates with available co2 reconstructions8 yields estimates of an eocene earth system sensitivity of 0 9 to 2 3 kelvin per watt per square metre at 68 per cent probability consistent with the high end of previous estimates11

on the duration of the paleocene eocene thermal maximum petm 1 the paleocene eocene thermal maximum petm is one of the best known examples of a transient climate perturbation associated with a brief but intense interval of global warming and a massive perturbation of the global carbon cycle from injection of isotopically light carbon into the ocean atmosphere system one key to quantifying the mass of carbon released identifying the source s and understanding the ultimate fate of this carbon is to develop high resolution age models two independent strategies have been employed cycle stratigraphy and analysis of extraterrestrial helium heet both of which were first tested on ocean drilling program odp site 690 these two methods are in agreement for the onset of the petm and initial recovery or the clay layer main body but seem to differ in the final recovery phase of the event above the clay layer where the carbonate contents rise and carbon isotope values return toward background values here we present a state of the art age model for the petm derived from a new orbital chronology developed with cycle stratigraphic records from sites drilled during odp leg 208 walvis ridge southeastern atlantic integrated with published records from site 690 weddell sea southern ocean odp leg 113 during leg 208 five paleocene eocene p e boundary sections sites 1262 to 1267 were recovered in multiple holes over a depth transect of more than 2200 m at the walvis ridge yielding the first stratigraphically complete p e deep sea sequence with moderate to relatively high sedimentation rates 1 to 3 cm ka where a is years a detailed chronology was developed with nondestructive x ray fluorescence xrf core scanning records on the scale of precession cycles with a total duration of the petm now estimated to be 170 ka the revised cycle stratigraphic record confirms original estimates for the duration of the onset and initial recovery but suggests a new duration for the final recovery that is intermediate to the previous estimates by cycle stratigraphy and heet

the ocean circulation in the southern hemisphere and its climatic impacts in the eocene abstract opening of southern ocean gateways may have had a controlling influence on the evolution of global climate the largest step in the history of cenozoic climate from an eocene greenhouse toward the modern glaciated state is correlated with opening of a deep water connection between the southern indian and southern pacific oceans this study synthesizes results from previous work assesses the possibility that ocean heat transport was much greater than modern during the globally warm eocene and explores the sensitivity of polar climate to large changes in ocean heat transport the magnitudes of these sensitivities are compared with those due to greenhouse gas concentration changes we find that ocean heat transport was unlikely to have been sufficiently greater than modern during the eocene to explain the change in the climate specifically in order to have significantly affected antarctic climate ocean heat transport changes would have had to change by an order of magnitude much greater than the largest change produced in our simulations in coupled climate model simulations changes in co2 concentrations from 1120 to 560 ppm supported by proxy records lead to significant antarctic responses in the absence of ocean heat transport changes the results show that antarctic snow accumulation is primarily controlled by changes in summer temperature not precipitation and that snow did not remain on antarctica during summer months in eocene even at low greenhouse gas concentrations greenhouse gas concentration changes and subsequent processes such as ice albedo and weathering feedbacks were more likely to have been the primary cause of antarctic glaciation than ocean heat transport changes

interpretation by numerical modelling of changes of fracture system hydraulic conductivity induced by fluid injection distinct element modelling of naturally fractured reservoirs is used to investigate changes of hydraulic conductivity induced by fluid injection general conclusions are drawn relating to the effects of uniform changes of pore pressure on conductivity anisotropy in connected joint systems the influence of cross cutting discontinuous joints on the conductivity of the joints against which they terminate is emphasized results from a two dimensional model are related to the observed performance of a granitic geothermal reservoir on emploie le modele a elements distincts des reservoirs fractures de facon naturelle pour etudier les changements dans la conductivite induits par l injection de fluide des conclusions generales sont tirees concernant les effets de changements uniformes de pression interstitielle dans des systemes de joints relies sur l anisotropie de conductivite on accentue l influence exercee sur la conductivite des joints par des joints discontinus transversaux des resultats obtenus a parti

early cenomanian hot greenhouse revealed by oxygen isotope record of exceptionally well preserved foraminifera from tanzania the search into earth s mid cretaceous greenhouse conditions has recently been stimulated by the tanzania drilling project tdp which has recovered exceptionally well preserved biogenic carbonates from subsurface pre neogene marine sediments in the eastern margin of central africa published tanzanian oxygen isotope records measured on exquisitely preserved foraminiferal tests dating to as old as 93ma provided evidence for a turonian hot greenhouse with very high and stable water column temperatures we have generated a comparable data set of exceptionally well preserved foraminifera from a lower cenomanian interval of tdp site 24 spanning 99 9 95 9ma planktonic foraminiferal thalmanninella globotruncanoides zone nannofossil corollithion kennedyi to lithraphidites eccentricus zones thereby extending the age coverage of the tanzanian foraminiferal o record back by 7 million years throughout the interval analyzed the new foraminiferal o data are consistently around 4 3 for surface dwelling planktonic taxa and 1 9 for benthic lenticulina spp which translate to conservative paleotemperature estimates of 31 c at the surface and 17 c at the sea floor upper bathyal depths considering the 40 s cenomanian paleolatitude of tdp site 24 these estimates are higher than computer simulation results for accepted normal greenhouse conditions those with up to 4x preindustrial pco2 level and suggest that the climate mode of the early cenomanian was very similar to the turonian hot greenhouse taking account of other comparable data sources from different regions the hot greenhouse mode within the normal mid cretaceous greenhouse may have begun by the latest albian but the precise timing of the critical transition remains uncertain

late paleocene arctic coastal climate inferred from molluscan stable and radiogenic isotope ratios abstract characterizing polar climates during past warm intervals is important for understanding greenhouse climate dynamics because high latitude surface temperatures and precipitation patterns are extremely sensitive to global climatic conditions model data comparisons of high latitude climates during past warm intervals cretaceous eocene pliocene are currently at odds specifically simulations of past warm climates produce polar regions characterized by sub freezing temperatures and significant seasonality whereas limited fossil proxy data indicate higher mean annual temperatures and low seasonality i e an equable climate we have constructed a data set to infer northern hemisphere polar marine temperatures during the late paleocene seasonal and mean annual temperature and the oxygen isotopic composition of precipitation are reconstructed for an arctic coastal setting during the thanetian 57 58 ma using fossil shell stable isotope profiles we estimate that coastal water temperatures varied between 10 and 15 c during the seasons of growth presumably spring summer and fall these findings support paleontological evidence implying northern hemisphere polar climates were seasonally warm during the late paleocene in addition estuarine fossil oxygen isotope profiles show periodic excursions to low values as low as 19 vpdb which indicate seasonal pulses of isotopically depleted freshwater

correlation between isotope records in marine and continental carbon reservoirs near the palaeocene eocene boundary changes in the isotope content of the large marine carbon reservoir can force shifts in that of the smaller carbon pools in the atmosphere and on land the carbon isotope compositions of marine carbonate sediments from the late palaeocene vary considerably exhibiting a sudden decrease close to the palaeocene eocene boundary which coincides with deep sea benthic extinctions1 and with changes in ocean circulation here we report that these fluctuations in the marine carbon isotope record are closely tracked by the terrestrial records provided by palaeosol carbonates and mammalian tooth enamel in using palaeosol carbonates to reconstruct the co2 content of the ancient atmosphere2 isotope shifts of this sort will have to be taken into account the sharp decrease in 13c 12c ratios in the late palaeocene provides a datum for precise correlation of marine and continental records and suggests that abrupt climate warming at this time may have played an important role in the evolution of land mammals

new chronology for the late paleocene thermal maximum and its environmental implications the late paleocene thermal maximum lptm is associated with a brief but intense interval of global warming and a massive perturbation of the global carbon cycle we have developed a new orbital chronology for ocean drilling program odp site 690 weddell sea southern ocean by using spectral analysis of high resolution geochemical records the lptm interval spans 11 precessional cycles yielding a duration of 210 to 220 k y the 13 c anomaly associated with the lptm has a magnitude of about 2 5 to 3 we show that about 2 of the excursion occurs within two steps that each were less than 1000 yr in duration the remainder developed through a series of steps over 52 k y the timing of these steps is consistent with a series of nearly catastrophic releases of methane from gas hydrates punctuated by intervals of relative equilibria between hydrate dissociation and carbon burial further we are able to correlate the records between odp sites 690 and 1051 western north atlantic on the scale of 21 k y cycles which demonstrates that the details of the 13 c excursion are recognizable between distant sites comparison of cycle records at sites 690 and 1051 suggests that sediment representing the interval 30 k y just prior to and at the onset of the lptm are missing in the latter location this unconformity probably resulted from slope failure accompanying methane hydrate dissociation within 10 k y of the start of the lptm

magnetostratigraphic calibration of eocene oligocene dinoflagellate cyst biostratigraphy from the norwegian greenland sea the presence of abundant age diagnostic dinoflagellate cysts in ocean drilling program odp hole 913b leg 151 deep sea drilling project hole 338 leg 38 and odp hole 643a leg 104 has enabled the development of a new biostratigraphy for the eocene oligocene interval in the norwegian greenland sea this development is important because the calcareous microfossils usually used for biostratigraphy in this age interval are generally absent in high latitude sediments as a result of dissolution in parallel with this biostratigraphic analysis we developed a magnetic reversal stratigraphy for these norwegian greenland sea sequences this has allowed independent age determination and has enabled the dinocyst biostratigraphy to be firmly tied into the global geomagnetic polarity timescale gpts the relatively high resolution of this study has enabled identification of dinoflagellate cyst assemblages that have affinities with those from the north sea and the north atlantic which allows regional correlation correlation of each site with the gpts has also allowed comparison of the stratigraphic record preserved in each drill hole hole 913b is the most complete and is the best preserved record of the eocene and oligocene in the northern hemisphere high latitudes and can serve as a reference section for palaeoenvironmental reconstructions of this age interval

arctic late paleocene early eocene paleoenvironments with special emphasis on the paleocene eocene thermal maximum lomonosov ridge integrated ocean drilling program expedition 302 we reconstruct the latest paleocene and early eocene 57 50 ma environmental trends in the arctic ocean and focus on the paleocene eocene thermal maximum petm 55 ma using strata recovered from the lomonosov ridge by the integrated ocean drilling program expedition 302 the lomonosov ridge was still partially subaerial during the latest paleocene and earliest eocene and gradually subsided during the early eocene organic dinoflagellate cyst dinocyst assemblages point to brackish and productive surface waters throughout the latest paleocene and early eocene dinocyst assemblages are cosmopolitan during this time interval suggesting warm conditions which is corroborated by tex86 reconstructed temperatures of 15 18 c inorganic geochemistry generally reflects reducing conditions within the sediment and euxinic conditions during the upper lower eocene spectral analysis reveals that the cyclicity recorded in x ray fluorescence scanning fe data from close to eocene thermal maximum 2 53 ma presence confirmed by dinocyst stratigraphy is related to precession within the lower part of the petm proxy records indicate enhanced weathering runoff anoxia and productivity along with sea level rise on the basis of total organic carbon content and variations in sediment accumulation rates excess organic carbon burial in the arctic ocean appears to have contributed significantly to the sequestration of injected carbon during the petm

climate model and proxy data constraints on ocean warming across the paleocene eocene thermal maximum article constraining the greenhouse gas forcing climatic warming and estimates of climate sensitivity across ancient large transient warming events is a major challenge to the palaeoclimate research community here we provide a new compilation and synthesis of the available marine proxy temperature data across the largest of these hyperthermals the paleocene eocene thermal maximum petm this includes the application of consistent temperature calibrations to all data including the most recent set of calibrations for archaeal lipid derived palaeothermometry this compilation provides the basis for an informed discussion of the likely range of petm warming the biases present in the existing record and an initial assessment of the geographical pattern of petm ocean warming to aid interpretation of the geographic variability of the proxy derived estimates of petm warming we present a comparison of this data with the patterns of warming produced by high pco2 sim ulations of eocene climates using the hadley centre atmosphere ocean general circulation model aogcm hadcm3l on the basis of this comparison and taking into account the patterns of intermediate water warming we estimate that the global mean surface temperature anomaly for the petm is within the range of 4 to 5 c

contributions to geotechnique 1948 2008 engineering geology rock mechanics and rock engineering throughout its history geotechnique has regularly published papers on the fundamentals of engineering geology the core concepts of rock mechanics and the practice of rock engineering in totality these papers provide a concise history of the development of these areas of geotechnics here a review of many of these papers is presented in terms of the specific themes of engineering geology rock slope instability behaviour of intact rock and discontinuities in rock field measurements in rock mechanics discontinuous rock masses numerical modelling and rock engineering papers covering a wide range of issues within these themes are outlined together with an indication of how they have influenced later developments the review clearly demonstrates how geotechnique has been at the forefront of rock mechanics rock engineering and engineering geology for the whole of its 60 year existence

distinct element modeling of hydraulically fractured lac du bonnet granite 1 the aim of this study is to better understand the mechanics of fracture development and propagation during hydraulic fracturing this paper presents some development and applications of discrete particle modeling of this problem a discontinuum modeling approach idealizes the material as separate particles bonded together at their contact points and utilizes the breakage of individual structural units or bonds to represent damage the numerical models are correlated with existing hydrofracture laboratory experiments which are presented in other publications a simulation of a laboratory scale hydrofracture experiment and the acoustic emission ae data from the experiment is used to validate the synthetic aes produced in the hydrofracture model this technique has been used to examine the mechanics of fracture initiation and time and spatial distributions of ae the modeling results demonstrate that the mechanism of hydraulically induced fracture in the lac du bonnet ldb granite core sample is predominantly tensile failure and that the shear cracks recorded in the hydrofracture experiment were due to slip on preexisting fractures numerical modeling of hydrofracture on homogeneous and heterogeneous synthetic samples seems to capture much of the behavior observed in the laboratory hydrofracture experiments

abrupt climate change and transient climates during the paleogene a marine perspective detailed investigations of high latitude sequences recently collected by the ocean drilling program odp indicate that periods of rapid climate change often culminated in brief transient climates with more extreme conditions than subsequent long term climates two examples of such events have been identified in the paleogene the first in latest paleocene time in the middle of a warming trend that began several million years earlier the second in earliest oligocene time near the end of a middle eocene to late oligocene global cooling trend superimposed on the earlier event was a sudden and extreme warming of both high latitude sea surface and deep ocean waters imbedded in the latter transition was an abrupt decline in high latitude temperatures and the brief appearance of a full size continental ice sheet on antarctica in both cases the climate extremes were not stable lasting for less than a few hundred thousand years indicating a temporary or transient climate state geochemical and sedimentolog

numerical methods in rock mechanics the purpose of this civilzone review paper is to present the techniques advances problems and likely future development directions in numerical modelling for rock mechanics and rock engineering

response of fractured rock subject to fluid injection part i development of a numerical model abstract the selection and development of a numerical model used to investigate the response of fractured rock to injection are described the distinct element method was chosen on the basis of its ability to represent explicitly the fractures and to couple the mechanical deformation to the fluid flow the numerical model was used to simulate fluid injection from a single well into each of four basic model reservoirs the results of these simulations form the basis of the interpretation given in parts ii and iii

nannoplankton malformation during the paleocene eocene thermal maximum and its paleoecological and paleoceanographic significance the paleocene eocene thermal maximum petm is characterized by a transient group of nannoplankton belonging to the genus discoaster our investigation of expanded shelf sections provides unprecedented detail of the morphology and phylogeny of the transient discoaster during the petm and their relationship with environmental change we observe a much larger range of morphological variation than previously documented suggesting that the taxa belonged to a plexus of highly gradational morphotypes rather than individual species we propose that the plexus represents malformed ecophenotypes of a single species that migrated to a deep photic zone refuge during the height of petm warming and eutrophication anomalously high rates of organic matter remineralization characterized these depths during the event and led to lower saturation levels which caused malformation the proposed mechanism explains the co occurrence of malformed discoaster with pristine species that grew in the upper photic zone moreover it illuminates why malformation is a rare phenomenon in the paleontological record

a high resolution north sea eocene dinocyst zonation abundant dinoflagellate cysts dinocysts from eocene strata of the north sea exhibit a consistent succession of events based on the analysis of 120 wells from quadrant 3 in the north to quadrants 21 and 22 in the south these events have a constant relationship with stratigraphic sequences and subsequences throughout the area eight eocene dinocyst zones and 23 subzones and the uppermost palaeocene apectodinium augustum biozone are defined by last occurrence or abundance events the north sea dinocyst succession is similar to that in denmark northwest germany belgium the netherlands and southern england permitting correlation with calcareous nannoplankton zones for sections in these areas and hence allowing correlation of north sea stratigraphy with northwest european and worldwide events

the planktonic foraminiferal response to the paleocene eocene thermal maximum on the atlantic coastal plain abstract planktonic foraminiferal assemblages in two cores from maryland and new jersey show evidence for significant changes in surface ocean habitats on the continental shelf during the paleocene eocene thermal maximum petm at both sites significant assemblage shifts occur immediately before the onset of the event these changes include the appearance of abundant triserial biserial species as well as rare excursion taxa which are limited to the interval of the carbon isotope excursion at deep sea sites the assemblage shifts signal the development of new habitats immediately prior to the onset of the petm likely involving warming surface ocean acidification increased stratification and oligotrophy a sharp increase in diversity at the onset of the event is interpreted as a further increase in stratification and warming as well as increased water depth and more eutrophic conditions finally we observe variant morphologies of several planktonic foraminifera which may also signal the response of the assemblage to environmental perturbation

influence of the water content on x ray fluorescence core scanning measurements in soft marine sediments the x ray fluorescence xrf core scanner provides bulk sediment chemistry data measured nondestructively at the split core sediment surface although this method is widely accepted there is little known about the effects of physical properties such as density and water content on xrf core scanner data comparison of xrf scanner measurements from the sediment surface and dry powder samples of sediment core geob7920 indicates strongly reduced element intensities for the lighter elements al and si we relate the lower element intensities of the measurements taken at the sediment surface to the amount of water in the sample volume analyzed by the xrf core scanner the heavier elements k ca ti and fe remain relatively unaffected by the variation of any physical property within sediment core geob7920 additionally we successfully use the elemental intensity of cl as a proxy for the seawater content in the sample volume analyzed by the xrf core scanner this enables the establishment of a correction function for the elements al and si that corrects for the radiation absorption of the water content in sediment core geob7920 off cape blanc nw africa

the paleocene eocene carbon isotope excursion in higher plant organic matter differential fractionation of angiosperms and conifers in the arctic abstract a study of upper paleocene lower eocene p e sediments deposited on the lomonosov ridge in the central arctic ocean reveals relatively high abundances of terrestrial biomarkers these include dehydroabietane and simonellite derived from conifers gymnosperms and a tetra aromatic triterpenoid derived from angiosperms the relative percentage of the angiosperm biomarker of the summed angiosperm conifer biomarkers was increased at the end of the paleocene eocene thermal maximum petm different when observed with pollen counts which showed a relative decrease in angiosperm pollen stable carbon isotopic analysis of these biomarkers shows that the negative carbon isotope excursion cie during the petm amounts to 3 for both conifer biomarkers dehydroabietane and simonellite comparable to the magnitude of the cie inferred from marine carbonates but significantly lower than the 4 5 of the terrestrial c29 n alkane m pagani n pedentchouk m huber a sluijs s schouten h brinkhuis j s sinninghe damste g r dickens and the iodp expedition 302 expedition scientists 2006 arctic s hydrology during global warming at the paleocene eocene thermal maximum nature 442 671 675 which is a compound sourced by both conifers and angiosperms conspicuously the angiosperm sourced aromatic triterpane shows a much larger cie of 6 and suggests that angiosperms increased in their carbon isotopic fractionation during the petm our results thus indicate that the 4 5 c29 n alkane cie reported previously represents the average cie of conifers and angiosperms at this site and suggest that the large and variable cie observed in terrestrial records may be partly explained by the variable contributions of conifers and angiosperms the differential response in isotopic fractionation of angiosperms and conifers points to different physiological responses of these vegetation types to the rise in temperature humidity and greenhouse gases during the petm

contrasting response of the calcareous nannoplankton communities after the eocene hyperthermal events in the tropical atlantic ocean abstract latest paleocene and early eocene hyperthermals were geologically brief profound environmental perturbations caused by massive additions of 13c depleted carbon to the ocean atmosphere system and therefore provide ancient analogs to assess the impact of modern global warming on the earth s ecosystem we document and compare population changes in calcareous nannoplankton the major primary producers in paleogene oceans across three consecutive hyperthermal episodes of differing magnitudes i e the most severe paleocene eocene thermal maximum petm the relatively mild eocene thermal maximum 2 etm2 and the least severe h2 in the tropical atlantic across all three hyperthermal events the total abundance and the abundance of the eutrophic and mesotrophic taxa decreased significantly while oligotrophic taxa increased markedly suggesting that oligotrophy prevailed in tropical atlantic surface waters a nonmetric multidimensional scaling ordination revealed that during the peak of each hyperthermal nannoplankton communities featured excursion taxa and assemblages substantially deviated from the pre event composition however during the recovery phase nannoplankton communities rapidly returned to quasi pre event compositions for the etm2 and h2 perturbations but remained distinct from the pre event composition for the petm this contrast between pre and post event compositions of nannoplankton communities may imply that the petm perturbation exceeded the resilience threshold of the tropical atlantic surface ecosystem and caused a regime shift cautioning the possible risk of an abrupt state change in oceanic ecosystem under the present situation which has a considerably faster and greater perturbation to the c cycle than during the petm

calcareous plankton evolution and the paleocene eocene thermal maximum event new evidence from tanzania the biotic response of calcareous microplankton at the paleocene eocene thermal maximum petm climate event principally comprised poleward migrations the appearance of excursion taxa and elevated turnover in calcareous nannoplankton here we examine whether this relatively muted evolutionary signal may be due to the quality of the stratigraphic and fossil record by analysing exceptionally well preserved microfossils from an expanded hemipelagic petm section in southern tanzania tdp site 14 both nannofossils and planktonic foraminifera show major abundance declines at the onset of the petm that are not explained by dilution or dissolution the petm onset is also marked by the extinction of eight nannofossil species possibly as many as 12 and the intra petm assemblages are quite distinct from background and dominated by coccolithus including the excursion taxon c bownii this biotic response is not clearly biased in favour of particular ecological groups although the nannofossil excursion taxa were all warm water favouring and there was a net diversity loss within cool water favouring eutrophic groups a shift from toweius to coccolithus dominated assemblages is suggestive of increased oligotrophy although the presence of abundant gladiolithus indicates upper photic zone oligotrophy throughout the time interval represented by the tdp site 14 section the significant plankton assemblage shifts diversity decline and possible reduction of calcareous plankton production and or export suggest the rapid onset of highly disruptive environmental change at the petm onset this change must have included rapid temperature increase and heat stress may have played a role in shaping the petm assemblage compositions causing a limited number of extinctions and favouring taxa from warmer areas of the groups ecological range however the muted evolutionary response in these plankton groups indicates that they were highly resilient to this environmental change and through adaptation to the new conditions e g the excursion taxa but probably principally through range shifts i e migration or simply the ability to acclimatize the vast majority of the biodiversity survived and thrived again once conditions returned to normal

oxygen isotope and paleobotanical estimates of temperature and δ18o latitude gradients over north america during the early eocene empirical estimates of climate parameters such as mean annual temperature mat are essential to describe both ancient climate and to ground truth climate model simulations of past climates in terrestrial settings no single proxy record is able to provide detailed temporal yet geographically widespread information and it thus becomes essential that paleoclimatic information obtained from different proxies be comparable as an example of how to compare estimates and to illustrate what can be learned by doing so we measured oxygen isotope ratios of phosphate in the tooth enamel of fossil mammals and the body scales of freshwater fish in order to estimate the mean annual temperature mat in which they lived the samples were collected from paleogene rocks of the bighorn green river and powder river basins of wyoming earliest eocene samples provide mat estimates that are similar to mat estimates for the same times and areas obtained from leaf margin analysis furthermore isotopic data from the paleocene eocene thermal maximum petm which has not yet yielded fossil floras indicate a significantly higher mat of 26 c we also used temperature estimates obtained by both methods to investigate paleoelevation and to reconstruct geographic patterns of mat over north america for the early eocene larger laramide basins have higher temperatures and lower inferred elevations compared to associated volcanic highlands where cooler temperatures are consistent with substantial elevations in turn latitudinal gradients in temperature indicate that warming centered on polar regions played an important role during the eocene hothouse lastly we show that the reconstructed eocene relation between oxygen isotope ratios of precipitation and mat is significantly different from the modern relation between these two variables because the relation has changed over time the modern correlation should not be used to estimate paleo mat from measurements of oxygen isotope ratios in fossil material

enhanced multidecadal climate variability in the seventeenth century from coral isotope records in the western indian ocean 1 the slowly growing coral diploastreaheliopora affords a novel opportunity to obtain multicentury records of paleoclimate including details of the interannual rhythms associated with the el nino southern oscillation enso system we examine climate variability in an enso teleconnected region using new oxygen isotope records from d heliopora spanning most of the twentieth 1896 1998 and seventeenth 1622 1722 centuries from the mafia archipelago tanzania the modern record demonstrates coherency with relevant instrumental and proxy time series documents twentieth century warming and displays significant power at enso periodicities the seventeenth century record lacks any trend exhibits interannual variance comparable to the modern record and displays a pronounced interdecadal signal not evident in the twentieth century that correlates with other tropical and hemispheric climate records we find no clear evidence of solar irradiance influence on interannual variability in the western indian ocean during these intervals although the mean sea surface temperature appears to vary inversely with insolation

large terrestrial and marine carbon and hydrogen isotope excursions in a new paleocene eocene boundary section from tanzania recent onshore drilling expeditions in tanzania have yielded sediments spanning much of the late cretaceous and paleogene which show exceptionally good preservation of both calcareous microfossils and organic matter the interval of the paleocene eocene thermal maximum petm was recovered at tanzania drilling project tdp site 14 in 2004 the petm interval was identified using planktonic foraminifer and nannofossil biostratigraphy carbon isotopic measurements of planktonic foraminifera from the genus subbotina show a maximum measured negative shift in 13c values of approximately 4 5 which is significantly larger than has been observed for most deep sea foraminifer records higher plant derived n alkanes yield a ca 6 5 negative shift through the same interval as carbon isotope fractionation in higher plants varies amongst taxa and is influenced by humidity it is possible that this remarkably large shift in the n alkane 13c values records environmental and vegetation changes as well as changes in the 13c value of the ocean atmosphere reservoir however dramatic increases in humidity appear to be unlikely as higher plant biomarker d values shift to higher rather than lower values taken together the records suggest that the magnitude of the carbon isotope excursion cie in the ocean atmosphere reservoir may have been larger than has generally been accepted this has important implications for the source and quantity of 13c depleted carbon released at the petm

timing and nature of the deepening of the tasmanian gateway 1 tectonic changes that produced a deep tasmanian gateway between australia and antarctica are widely invoked as the major mechanism for antarctic cryosphere growth and antarctic circumpolar current acc development during the eocene oligocene e o transition 34 33 ma ocean drilling program odp leg 189 recovered near continuous marine sedimentary records across the e o transition interval at four sites around tasmania these records are largely barren of calcareous microfossils but contain a rich record of siliceous and organic walled marine microfossils in this study we integrate micropaleontological sedimentological geochemical and paleomagnetic data from site 1172 east tasman plateau to identify four distinct phases a d in the e o tasmanian gateway deepening that are correlative among odp leg 189 sites phase a prior to 35 5 ma minor initial deepening characterized by a shallow marine prodeltaic setting with initial condensation episodes phase b 35 5 33 5 ma increased deepening marked by the onset of major glauconitic deposition and inception of energetic bottom water currents phase c 33 5 30 2 ma further deepening to bathyal depths with episodic erosion by increasingly energetic bottom water currents phase d 30 2 ma establishment of stable open ocean warm temperate oligotrophic settings characterized by siliceous carbonate ooze deposition our combined evidence indicates that this early oligocene tasmanian gateway deepening initially produced an eastward flow of relatively warm surface waters from the australo antarctic gulf into the southwestern pacific ocean this proto leeuwin current fundamentally differs from previous regional reconstructions of eastward flowing cool water e g a proto acc during the early oligocene and thereby represents an important new constraint for reconstructing regional to global scale dynamics for this major global change event

evolution of early cenozoic marine temperatures the equator to high southern latitude sea surface and vertical temperature gradients are reconstructed from oxygen isotope values of planktonic and benthic foraminifers for the following five time intervals late paleocene early eocene early middle eocene late eocene and early oligocene paleotemperatures are calculated using standard oxygen isotope temperature equations with adjustments to account for 1 variations in sea water 18o related to changes in global ice volume over time and 2 latitudinal gradients in surface water 18o these reconstructions indicate that sea surface temperatures sst of the southern oceans in the early eocene were as high as 15 c whereas temperatures during the late paleocene and early middle eocene reached maximum levels of 10 12 c by the late eocene and early oligocene high latitude sst had declined to 6 and 4 c respectively for most of the early paleogene low latitude sub tropical temperatures remained constant and well within the range of holocene temperatures 24 ndash 25 c but by the late eocene and early oligocene declined to values in the range of 18 to 22 c the late paleogene apparent decline in tropical temperatures however might be artificial because of dissolution of near surface foraminifera tests which biased sediment assemblages toward deeper dwelling foraminifera moreover according to recent plate reconstructions it appears that the majority of sites upon which the late eocene and early oligocene tropical temperatures were previously established were located either in or near regions likely to have been influenced by upwelling global deepwater temperature on average paralleled southern ocean sst for most of the paleogene we speculate based on the overall timing and character of marine sea surface temperature variation during the paleogene that some combination of both higher levels of greenhouse gases and increased heat transport was responsible for the exceptional high latitude warmth of the early eocene

orbital scale variations and timescales from the arctic ocean we investigate geochemical measurements from the arctic coring expedition to derive sedimentation rates for selected intervals in the early and middle eocene this analysis is performed by quantifying cyclical variations in physical property data and elemental concentrations derived with an x ray fluorescence xrf core scanner our results show that physical properties and xrf derived elemental concentrations are coherent and correlated to each other changes in elemental concentrations occur on depth scales from decimeters to meters and correspond to varying contributions of detrital minerals and biogenic silica we confirm and refine sedimentation rates of the order of 10 to 25 m ma 1 these rates were obtained independently through biostratigraphic and magnetostratigraphic methods we observe a strong imprint of astronomically sourced cycles particularly through climatic precession this observation allows us to test recently proposed theoretical calculations of insolation

late cretaceous neogene trends in deep ocean temperature and continental ice volume reconciling records of benthic foraminiferal geochemistry δ18o and mg ca with sea level history 1 we reconstruct trends in ice volume and deep ocean temperature for the past 108 myr resolving variations on timescales of 2 myr and longer we use a sea level record as a proxy for ice volume a benthic foraminiferal mg cabf record as a proxy for temperature and a benthic foraminiferal 18obf record as a proxy for both this allows us to construct dual estimates of temperature and ice volume variations for the interval 10 60 ma extracting temperature from 18obf by using sea level as a proxy for ice volume to constrain the 18osw component and extracting seawater 18osw which reflects ice volume from 18obf by using mg cabf to constrain the temperature component each of these approaches requires numerous assumptions but the range of plausible solutions are concordant on timescales 2 myr and within an uncertainty of 2 c temperature and 0 4 18osw the agreement between the two approaches for the last 50 myr provides empirical justification for the use of 18obf mg cabf and sea level records as robust climate proxies our reconstructions indicate differences between deep ocean cooling and continental ice growth in the late cenozoic cooling occurred gradually in the middle late eocene and late miocene pliocene while ice growth occurred rapidly in the earliest oligocene middle miocene and plio pleistocene these differences are consistent with climate models that imply that temperatures set by the long term co2 equilibrium should change only gradually on timescales 2 myr but growth of continental ice sheets may be rapid in response to climate thresholds due to feedbacks that are not yet fully understood

maceral total organic carbon and palynological analyses of ross ice shelf project site j9 cores analyses of macerals and total organic carbon indicate that the low organic content of core sediments from ross ice shelf project site j9 has been selectively reduced further probably by postdepositional submarine oxidation palynological analysis revealed a reworked paleogene dinocyst flora of low diversity the transantarctic flora this constitutes the most southerly dinocyst flora reported thus far the antarctic distribution of the transantarctic flora supports the existence of a transantarctic strait during the paleogene the j9 sporomorph assemblage also is reworked and paleogene in age

inorganic geochemistry of albian sediments from the lower saxony basin nw germany palaeoenvironmental constraints and orbital cycles abstract within the international albicore project upper albian sediments from a 245 m core kirchrode i drilled in hannover were studied by inorganic geochemical methods more than 650 samples minimum sample spacing 0 5 m were analysed for major and minor element concentrations this chemical database was used to reconstruct the depositional environment and to investigate the influence of high frequency milankovitch cycles on the chemical composition of the sediments the chemical composition of the sedimentary sequence is primarily controlled by variations in carbonate content corresponding to ca al ratios variations in both ti al and si al ratios are interpreted as fluctuations in detrital composition resulting from increases in smectite and quartz content in the upper section of the core high amounts of reactive iron but low pyrite concentrations the lack of enrichment of redox sensitive trace elements v cr and high mn concentrations indicate oxic bottom water conditions and the absence of an oxygen minimum zone for the upper albian at the kirchrode site the nutrient related trace elements ba p zn suggest a generally oligotrophic setting with slightly elevated productivity only in the uppermost upper albian only one layer was identified as containing volcanogenic material at 87 20 m this layer is characterised by elevated montmorillonite zr and nb mass balance calculations for the entire core suggest that the high mn values cannot be explained by riverine input alone therefore a coastal oxygen minimum zone south of the kirchrode site is postulated as an additional mn source cyclic variations in both carbonate content and al normalised concentrations of predominantly detrital elements like si and ti are seen in a 60 m interval 40 100 m where sedimentological palaeontological and geochemical data suggest stable depositional conditions although carbonate cyclicity cyclicity in detrital input and nutrient related element abundances do not correlate with each other three strong peaks in the results of spectral analysis of these chemical data for this interval appear to correspond to milankovitch frequencies in the eccentricity obliquity and precession bands

rapid diversification of planktonic foraminifera in the tropical pacific odp site 865 during the late paleocene thermal maximum the planktonic foraminiferal generamorozovellaandacarininarapidly in 10 k y diversified during the late paleocene thermal maximum lptm giving rise to such morphotypes asm allisonensis new species m africana anda sibaiyaensis single specimen isotopicanalysisconfirmsthatm allisonensisanda sibaiyaensisarerestrictedtothelptm carbon isotope excursion recorded at ocean drilling program site 865 equatorial pacific ocean the short lived 50 to several 100 k y excursion taxa attest to the ephemeral effectsofthelptmonthecalcareousplankton single specimenoxygenisotopedatashow that evolution of m allisonensis and a sibaiyaensis was accompanied by migration to deeper water depths ancestralm velascoensisanda soldadoensiswere extremely rare or absent during the early stages of the lptm but immigrated back into the study area to coexist with their descendants in later lptm horizons photosymbiosis may have facilitatedthemorozovellidandacarininiddiversificationsduringtheoligotrophicconditionsof the lptm

structure of the upper water column in the northwest north atlantic modern versus last glacial maximum conditions 1 during the last glacial maximum the northwestern north atlantic constituted a major conduit for labrador and greenland ice sheet meltwaters vertical density gradients in its upper water masses have been reconstructed by combining information from transfer functions based on dinocysts and from oxygen isotope measurements 18o in planktonic foraminifera transfer functions yield temperature and salinity and thus potential density for the warmest august and coldest february months in the photic zone the 18o values in different size fractions of epipelagic globigerina bulloides and mesopelagic neogloboquadrina pachyderma left coiled npl foraminifera allow us to assess gradients through the pycnocline between surface and intermediate waters based on the calibration of a versus 18o relationship from transfer function reconstructions the size and density of npl shells provide further constraints on these gradients the results show the development of a very strong pycnocline during the lgm with a difference of about 3 summer to 1 5 winter units between surface and underlying waters they indicate conditions unfavorable for vertical convection and support the hypothesis of the spreading of a shallow low salinity buoyant layer over the northern north atlantic this layer depicted a strong e w gradient with maximum seasonal contrast and minimum absolute values westward

simulation of early eocene water isotopes using an earth system model and its implication for past climate reconstruction abstract our understanding of past climate conditions largely comes from paleoclimate proxies such as oxygen isotope ratios 18 oc in marine fossils the marine 18 oc signal primarily reflects a mixture of seawater temperature and oxygen isotopic composition of seawater 18 ow at the time of calcification knowledge of 18 ow is critical for the interpretation of marine 18 oc records but remains poor for past hothouse climates here we conduct water isotope enabled simulations of the early eocene using co2 levels of 1 3 6 and 9 the preindustrial value we calculate model 18 oc using simulated 18 ow and ocean temperature and make direct comparison with proxy records model 18 oc matches the proxy values well for the early eocene and paleocene eocene thermal maximum with root mean squared errors approaching the standard error in individual records eocene 18 ow in the model exhibits strong variation depending on states of the hydrological cycle and ocean circulation differences in the mean 18 ow between regions of net evaporation and precipitation increase monotonically with the magnitude of the net atmospheric moisture transport that connects them however this relationship breaks at the regional scale due to ocean circulation changes in particular an increase in ocean ventilation brings more 18o enriched deep water into the mixed layer increasing sea surface 18 ow near the ventilation site and in certain remote regions through fast upper ocean currents 18 ow variations and the linkage to both hydrological cycle and ocean circulation bring challenges for an accurate interpretation of marine 18 oc records our study illustrates the value of using water isotope enabled simulations and model data comparison for learning past climate changes

fe co3 oh in goethite from a mid latitude north american oxisol estimate of atmospheric co2 concentration in the early eocene climatic optimum abstract measured mole fractions x and 13c values of the fe co3 oh component in pedogenic goethite from a mid latitude oxisol of early eocene age 52 ma b p range from 0 0014 to 0 0064 and 20 1 to 15 4 respectively these values of x imply that concentrations of co2 gas in the paleosol were 7400 to 34 000 ppm 13c and 1 x are correlated and define a linear soil co2 diffusive mixing line with a positive slope such positive slopes are characteristic of mixing of two isotopically distinct co2 endmembers atmospheric co2 and co2 from oxidation of soil organic matter from the intercept of the mixing line it is calculated that the 13c value of organic matter in the ancient soil was 28 0 the magnitude of the slope implies an early eocene atmospheric co2 concentration of 2700 ppm a simple model for forest soils suggests that a canopy effect may cause atmospheric co2 concentrations deduced from pedogenic minerals to underestimate the actual concentrations of atmospheric co2 if a significant forest canopy were present at the time of formation of pedogenic goethite in the ione fm the concentration of 2700 ppm calculated for atmospheric co2 could be slightly low but the underestimate is expected to be

heat transport deep waters and thermal gradients coupled simulation of an eocene greenhouse climate for the first time a coupled general circulation model with interactive and dynamical atmospheric oceanic and sea ice components is used to simulate an eocene 50 ma greenhouse climate we introduce efficient ocean spin up methods for coupled paleoclimate modeling sea surface temperatures ssts and salinities evolve unconstrained producing the first proxy data independent estimates for these eocene climate parameters tropical and extratropical model predicted ssts are warmer than modern values by 3 and 5 c respectively salinity driven deep water formation occurs in the north atlantic and tethys the zonal average overturning circulation is weaker than modern eocene ocean heat transport is 0 6 pw less than modern in the northern hemisphere and 0 4 pw greater in the southern hemisphere the model predicted near modern vertical and meridional eocene temperature gradients imply that the dominant theory for maintaining low gradients increased ocean heat transport is incorrect or incomplete and other mechanisms should be explored

response of fractured rock subject to fluid injection part iii practical application abstract the results of the distinct element modelling are used to interpret field observations of injection pressures two additional examples of the qualitative use of the model are presented the sensitivity of reservoirs to even brief periods of high rate injection and the value of using dynamic coupled models to interpret field performance are emphasised