a 4500 year proxy climate record from peatlands in the north of ireland the identification of widespread summer drought phases abstract mid to late holocene high resolution testate amoebae derived water table reconstructions from two peatlands in the north of ireland are presented the proxy climate records are dated and correlated using a combination of ams 14 c dating spheroidal carbonaceous particles and tephrochronology the reconstructions start prior to the hekla 4 tephra isochron 2395 2279 bc and thus span the last 4500 years the records are compiled by the process of tuning within chronological errors standardisation and stacking comparisons are made to existing palaeoclimate records from peatlands in northern britain and ireland and the compiled lake level record for mid latitude europe four coherent dry phases are identified in the records at ca 1150 800 bc 320 bc ad 150 ad 250 470 and ad 1850 2000 recent research has shown that peat derived water table reconstructions reflect summer water deficit and therefore the dry phases are interpreted as periods with a higher frequency and or greater magnitudes of summer drought these drought phases occur during periods of relatively low 14 c production which may add support to the hypothesis of persistent solar forcing of climate change during the holocene any relationship with the north atlantic stacked drift ice record is less clear

holocene palaeoclimates from peat stratigraphy macrofossil proxy climate records from three oceanic raised bogs in england and ireland quantified analyses of plant macrofossil remains have been made from three profiles of peat from raised bogs spanning a distance of 425 km from western ireland to northern england the reconstructed vegetation of each profile is related to changing bog surface wetness bsw and since the bogs are ombrotrophic these bsw changes are interpreted in terms of changing climate using age depth models based on a total of 49 radiocarbon dates a number of wetter and drier phases are identified and phase shifts to wetter and or cooler climates are defined prominent coincident changes to wetter conditions are dated in at least two of the profiles to ca 4400 4000 1750 1400 and 1000 cal bp and in all three profiles at 3200 2750 2350 2250 and around 700 cal bp these phases are related to proxy climate changes in other terrestrial data sets from northwest europe and a broad degree of synchroneity is demonstrated

bronze age upland settlement decline in southwest england testing the climate change hypothesis abstract the division of land on dartmoor during the bronze age by the construction of moor wide boundaries known as reaves represents a significant development in agricultural practice and land tenure previous research relating to the dartmoor reaves suggests this way of life may have continued for no longer than 200 400 years it has been suggested that their abandonment occurred as the result of a deteriorating climate although there are no published palaeoclimatic reconstructions from the area we therefore test the hypothesis that on dartmoor a marked climatic deterioration occurred in the late bronze age that can be linked to the abandonment of the reaves a palaeoclimatic reconstruction derived from testate amoebae and peat humification analyses is presented from tor royal bog central dartmoor the first such record from southwest england a major shift to a cooler and or wetter climate is inferred from ca 1395 to 1155 cal bc that is coincident with the period hypothesised as encompassing the abandonment this climatic deterioration is replicated in sites in northern britain suggesting it was a widespread event it is concluded that while the evidence supports a climatically forced retreat there are a range of other socio economic factors that must also be taken into consideration

high resolution peatland water table changes for the past 200 years the influence of climate and implications for management management of peatlands for conservation purposes is often directed at mitigation of damaging impacts of past and present human activity assessment of such impacts is often based on perspectives from short term ecological data here we test a series of hypotheses for the causes of changes in mire hydrology and vegetation on the border mires in northern england using palaeoecological data for the last 200 years ecological data suggest peatlands surrounded by plantation forestry have become drier over the last 40 years this could be caused by direct hydrological impacts of the growing trees and associated drainage or indirectly by the cessation of grazing and burning a third hypothesis is that hydrological changes are the result of recent climatic change high resolution water table reconstructions from testate amoebae analysis supported by plant macrofossil analysis and dated by 210pb spheroidal carbonaceous particles scps and pollen data demonstrate that a site outside the direct in uence of fores

holocene carbon accumulation rates from three ombrotrophic peatlands in boreal quebec canada impact of climate driven ecohydrological change understanding the processes controlling peatland carbon c sequestration is critical to anticipate potential changes in the global c cycle in response to climate change although identification of these factors may be relatively straightforward on seasonal timescales at centennial to millennial timescales complexities arise because of interactions between climate vegetation hydrology and long term ecological processes to better understand the factors controlling long term c accumulation holocene rates of c sequestration were quantified from three pristine ombrotrophic peatlands in boreal quebec northeastern canada 52 n 75 76 w bulk density and loss on ignition analyses combined with radiocarbon dating and age depth modelling were used to estimate long term apparent rates of carbon accumulation past changes in vegetation and water table depth were obtained from plant macrofossil and testate amoeba analysis earliest regional peat accumulation started 7520 cal bp with long term rates of c s

compilation of non annually resolved holocene proxy climate records stacked holocene peatland palaeo water table reconstructions from northern britain abstract the number and range of holocene palaeoclimate reconstructions from various regions of the world have increased dramatically over the last decade the data density for many regions and proxies now offers the potential of robust regional scale reconstructions that avoid the problems of records from individual sites and improve communication between palaeoclimate subdisciplines and climate modellers however there are problems with chronological uncertainties and quantification of proxies which make compilation of multiple records difficult here we explore a stacking and tuning approach to the derivation of regional records from peatland climate proxies to test its applicability to non annually resolved terrestrial records twelve individual records from northern britain based on water table reconstructions from testate amoebae analysis were divided into four regions records were detrended normalised and compared within regions to identify clear correlative events the original chronologies of the records were tuned using both these events and independent age markers the stacked record for northern britain indicates pronounced changes to wet conditions at 3600 2760 and 1600 cal yr bp with more minor changes at 3060 2050 1260 860 550 and 260 cal yr bp the main wet phases are highly correlated with mid european lake highstands wider north atlantic climate change inferred from ocean and ice core records and solar variability tuning and stacking of non annual terrestrial palaeoclimate records is a new approach to the compilation and reconciliation of individual records within coherent climatic regions and provides a tool for upscaling of palaeoclimate records for climate model data comparisons

optical characteristics of amorphous kerogens and the hydrocarbon generating potential of source rocks abstract four recurring types of amorphous kerogen are optically identified in petroleum source rock samples and are related to hydrocarbon generating potential defined here as geochemically interpreted oil prone or gas prone at this time a genetic classification is not possible the different amorphous kerogen types are distinguished on the basis of microscopic textural differences type a chunky compact masses with mottled network or weak polygonal textures type b very small dense elongate oval or rounded individual grains type c clumpswith granular fragmented or globular textures type d thin platy or rectangular individual grains geochemistry defined oil prone samples generally contain types a and or d separately or combined geochemically defined gas prone samples rarely contain type a and vary in amounts of types b c and or d the samples in this study contain dominantly one of the four types of amorphous kerogen so the geochemical analyses of the whole rock or bulk concentrated kerogen samples are assumed to be analyses of the dominant amorphous type the samples were chemically analyzed by several techniques to determine the oil or gas generating potential the establishment of relations between specific optical and chemical properties of kerogen types can make visual kerogen analyses more meaningful in predicting the hydrocarbon generation potential of source rocks

detection and evaluation of hydrocarbons in source rocks by fluorescence microscopy abstract in pursuing the detection of hydrocarbons in sedimentary rocks by conventional petrological methods an attempt has been made to correlate standard fluorescence parameters with the quality and quantity of hydrocarbons present in crushed rocks embedded in epoxy resin the capacity of the embedding resin commonly used in the preparation of petrographic samples to extract and physically fix hydrocarbons is recognized this phenomenon permits one to measure monochromatic fluorescence parameters i 546 and q u v 650 500 on the trapped hydrocarbons and to correlate these parameters with selected geochemical data the potential application of using these petrological parameters to evaluate oil quantities and qualities is tested using real case studies it is also shown that it is possible to directly detect the mature zone in each case

rich fen development in ce europe resilience to climate change and human impact over the last ca 3500 years here for the first time in se poland we document the long term development of a rich fen and assess its sensitivity to climate change and human impacts over the last ca 3500 years our results are based on a high resolution continuous plant macrofossil remains mollusc and pollen record complemented by geochemical mineral magnetic and physical characterisation and radiocarbon dating from bagno serebryskie rich fen located in se poland based on the palaeoecological data we distinguished five stages of wet habitat conditions 5000 3300 2800 2150 1600 1100 750 230 150 10 cal yr bp and five dry periods at ca 3300 2800 2150 1600 1100 750 230 150 10 to 64 cal yr bp the pollen and geochemistry records particularly pb show that the first human activity in the study area occurred ca 3200 cal yr bp and increased markedly from 500 cal yr bp affecting local plant development including the population size of cladium mariscus our study has shown that despite human impact drainage fire bagno serebryskie peatland has hosted rare presently protected species such as cladium mariscus for hundreds of years we conclude that in common with ombrotrophic bogs rich fen ecosystems can provide a reliable source of palaeoclimatic and palaeohydrological data our study also shows that a large peatland 376 ha can be as sensitive a palaeohydrological archive as smaller mires

assessment of peat quality by molecular and bulk geochemical analysis application to the holocene record of the chautagne marsh haute savoie france although it is primarily constituted in general from a limited variety of local plants peat is however sensitive to physicochemical changes in the medium in particular those induced by hydrological fluctuations the present study aims at confronting the information on peat quality provided by various families of biochemical components lipids lignin sugars especially in order to check the validity of a new organic matter om quality indicator the r400 index directly drawn from rock eval pyrolysis this parameter which is deduced from the sole s2 pyrolysis peak is extremely robust the chautagne marsh located between the le bourget lake and the rhone river lies in a key situation for recording lake level variations and rhone river floods all along its holocene filling the study was conducted on a 6 m long core which comprises 4 m of peat under 66 cm of pedogenetically altered om rich sediment classical rock eval pyrolysis revealed few qualitative and quantitative om changes with total organic carbon toc values close to 50 and hydrogen index values around 300 350 mg hc g 1toc in the peat the r400 parameter remains practically unchanged in the upper unit affected by pedogenesis it fluctuates however all along the peaty unit together with a progressive downward decrease ascribable to diagenesis molecular analyses show that samples with high r400 values are richer in sugars and in slightly oxidized lignin these results support the idea that the r400 parameter can be used as an indicator of om preservation since om preservation is mostly controlled by the water table in peat the chautagne marsh records hydrological fluctuations such as those of the le bourget lake water level all along the holocene

organic petrology of source rocks history and state of the art abstract the development of organic source rock petrology depended on the methods applied a procedure derived from coal petrology is the study of polished sections of the untreated rock under incident light this method combined with the fluorescence techniques is best suited to characterize and identify the discrete organic matter macerals and permits the most reliabble maturity measurements on the basis of vitrinite reflectance and of various fluorescence parameters another common method treats the rock with acids and studies strew slides of organic matter concentrates this destroys the natural texture of the rock and often some of the individual macerals as well but on the other hand it allows recognition of extremely fine particles which are not resolvable in polished sections maturity studies based on maceral colour changes as observed in strew slides are rapid and practical although they are rather subjective the relative merits of the various methods are discussed the individual organic constituents as seen in the whole rock and in organic matter concentrates are described and illustrated in two colour plates some classification systems are compared in tabular form finally the history of microscopic observations and measurements with respect to the generation of petroleum like substances in coal is briefly reviewed

variations of organo mineral microfacies of posidonia shale from the lower saxony basin and the west netherlands basin application to paleoenvironmental reconstruction abstract high resolution organic petrological analysis has been carried out on core samples of the posidonia shale from four wells two located in northwestern germany lower saxony basin and two in the western netherlands west netherlands basin the organo mineral microfacies defined by maceral composition and associated mineral matter show a wide range of variations related to the proportions of individual liptinite macerals of marine origin and of terrestrial macerals macerals of vitrinite inertinite groups and sporinite variations in organo mineral microfacies in which the organic components are sensitive to paleoenvironmental changes are considered as a potential indicator of changes in depositional conditions sedimentation of organic matter is controlled by several factors the most important in the marine environment being primary biomass productivity and influx of transported terrestrial organic matter biological degradation related to bacterial activity and the oxygen content of the bottom water the level of degradation in organic rich sediments is mainly related to oxygen availability which in turn influences the diversity of algae and the quality and quantity of the preserved organic matter these two factors can be directly linked to maceral preservation and the organo mineral microfacies in order to evaluate the relationships between different types of organic matter and paleoenvironmental conditions two indices the oxidation index and the degradation index have been proposed these indices illustrate the transition from highly degraded to well preserved macerals provide information on the types of organic matter and permit recognition of precursors for degraded amorphous organic matter aom use of these indices not only enables determination of the organo mineral microfacies but also sheds light on the aom precursors in the posidonia shale information derived from the indices can also be used to reconstruct the paleoenvironments

organic matter hosted pore system marcellus formation devonian pennsylvania the marcellus formation of pennsylvania represents an outstanding example of an organic matter om hosted pore system most pores detectable by field emission scanning electron microscopy fe sem are associated with om instead of mineral matrix in the two wells studied here total organic carbon toc content is a stronger control on om hosted porosity than is thermal maturity the two study wells span a maturity from late wet gas vitrinite reflectance ro 1 0 to dry gas ro 2 1 samples with a toc less than 5 5 wt display a positive correlation between toc and porosity but samples with a toc greater than 5 5 wt display little or no increase in porosity with a further increasing toc in a subset of samples 14 across a range of toc 2 3 13 6 wt the pore volume detectable by fe sem is a small fraction of total porosity ranging from 2 to 32 of the helium porosity importantly the fe sem visible porosity in om decreases significantly with increasing toc diminishing from 30 of om volume to less than 1 of om volume across the range of toc the morphology and size of om hosted pores also vary systematically with toc the interpretation of this anticorrelation between om content and sem visible pores remains uncertain samples with the lowest om porosity higher toc may represent gas expulsion pore collapse that was more complete as a consequence of greater om connectivity and framework compaction whereas samples with higher om porosity lower toc correspond to rigid mineral frameworks that inhibited compactional expulsion of methane filled bubbles alternatively higher toc samples may contain om low initial hydrogen index relatively unreactive that is less prone to development of fe sem detectable pores in this interpretation om type controlled by sequence stratigraphic position is a factor in determining pore size distribution

organofacies composition of upper jurassic lowermost cretaceous source rocks danish central graben and insight into the correlation to oils in the valdemar field abstract the organic rich marine shales of the upper jurassic lowermost cretaceous farsund formation are the main hydrocarbon source rocks for the cretaceous chalk reservoir of the valdemar field danish north sea geochemical analyses of oil extracts from core samples across the greater valdemar field show substantial heterogeneity of the reservoir oils suggesting contribution from kitchen areas with source rocks of variable organofacies and thermal maturity in order to better understand the source rock facies that charged the field a refined organofacies characterization of the upper jurassic lowermost cretaceous marine shale source rock succession farsund formation in the danish central graben was established this organofacies characterization is based on integration of petrographic and geochemical data and demonstrates large variations in both the regional and local distribution of the organofacies at the sequence level in the shales within the danish central graben in addition the organofacies characterization shows that the respective sequences in the succession may be represented by several organofacies at the same time part of the explanation to the heterogeneity in the oil types accumulated within the valdemar field may lie in the presence of different organofacies within the uppermost sequences vol 3 to ryaz 1 in the three kitchen areas each organofacies presumable generates different types of oils and the variation in the relative proportions of the different organofacies likely determines the composition of the generated oils one dimensional 1 d maturity modelling at three pseudo well locations each representing a potential farsund formation kitchen shows that all kitchens are in the main oil window and that mainly oil was expelled from the volg 3 to ryaz 1 sequences modelling indicates that i average values of toc hi thickness and the kinetic model are the main controls on generation and expulsion of hydrocarbons and ii by increasing these parameters expulsion could also occur from the lower part of the succession

a 5500 year proxy climate and vegetation record from blanket mire at talla moss borders scotland a monolith of peat taken from an upland blanket mire at talla moss southern scotland was sub jected to peat humification and pollen analyses to produce both a proxy climate record and a vegetational history covering the last 5500 years while the peat showed little visible stratigraphy with no intimation of major peat humification changes colorimetric data indicate a markedly oscillatory climate record which is apparently largely independent of or out of phase with major vegetational changes the raw data imply particular wet shifts in climate at c 3455 bp c 2600 bp c 1930 bp c 1095 bp with a markedly wet or cool and wet episode commencing at c 540 bp these are central age estimates and should not be regarded as precise dates for the inferred climate shifts other wet shifts apparently date from c 3070 bp c 2265 bp and c 1700 bp although the first of these corresponds with pollen evidence for significant prehistoric human activity in the locality spectral analysis of the peat h

comparing regional and supra regional transfer functions for palaeohydrological reconstruction from holocene peatlands abstract testate amoebae based transfer functions are commonly used in peatland palaeoclimate studies these models have been developed in several regions of the world and are sometimes used for palaeohydrological reconstruction from fossil data in locations where no transfer functions exist limitations of this approach may include missing modern analogues and problems associated with site specific or regional factors in testate amoebae ecology and biogeography this study presents new testate amoebae hydrology transfer functions based on data from six peatlands in northern england transfer functions were generated for water table depth and moisture content using weighted averaging tolerance downweighted regression with inverse deshrinking and model performance was assessed using leave one out jacknifing cross validation to examine the robustness of applying transfer functions extra regionally we performed a number of spatially independent cross validation sicv tests using contemporary testate amoebae and environmental data from established northern ireland and accrotelm transfer functions inferred water table depths were consistent with observed values in terms of position along the hydrological gradient however magnitudes varied we then applied the three independent transfer functions to fossil data from a peatland in northern england to compare the reconstructions the results show that the direction of the reconstructions is consistent in terms of wet dry shifts however variation in the magnitudes of the reconstructed water tables is apparent this probably reflects the sampling regime including temporal seasonal effects and differences in testate amoebae ecology between regions and individual sites

a delayed climatic response to solar forcing at 2800 cal bp multiproxy evidence from three irish peatlands multiproxy palaeohydrological records from three raised bogs in northern ireland indicate that a major shift to wetter cooler climatic conditions postdated the rapid decrease in solar activity at 2800 cal bp by 100 years this event is bracketed by two wiggle match radiocarbon dated cryptotephra layers in each profile enabling a high degree of chronological precision these replicated data corroborate previous findings based on irish peat humification profiles and may indicate spatial complexity in the climatic response to solar activity between oceanic and continental areas

evolution of porosity and pore geometry in the permian whitehill formation of south africa a fe sem image analysis study abstract since the advent of technologically efficient exploitation of economic hydrocarbon reservoirs in shales increasingly more research has been devoted to identifying and characterizing pore systems within shales however only a handful of these studies focused on the development of porosity in thermally mature unconventional reservoirs in this study the evolution of porosity and pore geometry in the permian whitehill formation is addressed with the aid of ultrathin sections 2 3 cm 10 20 m thick and field emission scanning electron microscopy fe sem on samples with mean random vitrinite reflectance values ranging from 1 03 to 4 07 ro we document a strong positive covariation of porosity and total organic carbon content toc in all localities however for samples with vitrinite reflectance values greater than 2 88 ro porosity per unit toc decreased by over 25 relative to samples with lower thermal maturities the positive covariation of thermal maturity and total porosity recorded here is unsurprising and have been documented previously in many gas shales however the dramatic decrease in porosity restricted to samples from localities that experienced advanced maturation ro 2 88 is viewed as an evidence that porosity decrease is directly related to late thermal decarboxylation of organic matter this is supported by the presence of pores and micro fractures infilled by fibrous grains including carbonates clays silicates and phosphates and residual fluid inclusions these grains were likely generated from re precipitation of framework grains previously dissolved by organic acids carboxylic phenolic that were generated during thermochemical decarboxylation of the om our findings do not only fill important gaps in the understanding of organic pore development including processes that create preserve and destroy porosity the porosities described here are also key to gas transfer from shale matrix to induced fractures during fracture stimulation programs

evaluating long term regional climate variability in the maritime region of the st lawrence north shore eastern canada using a multi site comparison of peat based paleohydrological records this study presents paleohydrological reconstructions from ombrotrophic peatlands bogs along the north shore of the estuary and the gulf of st lawrence in eastern canada past water table depths were reconstructed based on testate amoebae analyses within four peatlands from two maritime ecoclimatic regions boreal and subarctic using a new transfer function the comparison of multiple peat based paleohydrological records was used to distinguish climate driven changes from variations related to site specific factors coherence between the water table reconstructions at the regional scale suggests a common climatic influence on bog paleohydrology but there are inconsistencies which also suggest an influence of non climatic factors e g internal peatland processes and feedbacks the surface drying and increased hydrological variability after 3000 cal a bp in the studied bogs coincide with the transition from the holocene climatic optimum to the neoglacial cooling documented by proxy climate records in eastern canada the bogs of havre st pierre have experienced major drying during the late holocene indicating important annual to centennial water deficits at the peatland surface regional differences in the magnitude of the hydrological fluctuations may result from distinctive climatic conditions or could indicate that bog surface wetness in the gulf of st lawrence was more sensitive to past climate changes copyright 2014 john wiley sons ltd

reconstructing holocene water tables in new zealand using testate amoebae differential preservation of tests and implications for the use of transfer functions testate amoebae analysis is used to provide the e rst quantitative reconstruction of holocene surface wetness changes from a southern hemisphere ombrogenous bog water table depth and surface moisture are the dominant environmental factors ine uencing testate amoebae species composition in a modern training set of 62 surface samples from 19 bogs in new zealand a transfer function based on partial least squares pls performed well in cross validation of modern samples but produced unrealistic predictions of water table depth and moisture for fossil samples this resulted from poor overlap of species composition between modern and fossil samples peat humie cation data is used to examine decay related species diversity trends and ordination is used to explore the differences between modern and fossil assemblages poor overlap can be explained by differential preservation in the fossil assemblages of those taxa with more robust tests this enhances their abundance and reduces the overall diversity of the fossil assemblages human activities over the last 150 years have also ine uenced the surface environments and hydrology of the sampled bogs in this situation weighted average wa and tolerance downweighted weighted average wa tol models were more robust than pls and were applied along with semi quantitative scoring to reconstruct more realistic holocene surface wetness changes selection of the best model for reconstruction of surface wetness changes should be based on the characteristics of the fossil data rather than the predictive power of the model in cross validation of the modern data alone

testing the integrity of fine spatial resolution palaeoecological records microcharcoal data from near duplicate peat profiles from the north york moors uk microcharcoal data which cover the millennium preceding the ulmus decline from near replicate peat profiles 30 cm apart are presented from north gill an intensively studied upland spring head site in north east england with an established detailed palaeoecological record the ulmus decline at this site has been consistently dated to ca 4700 14c years bp the microcharcoal records from these two very closely adjacent points which must have had virtually identical microcharcoal source areas are assessed for their degrees of similarity and variability at 1 cm vertical sampling intervals in an investigation which parallels a previous comparative pollen study of the two profiles the major trends and frequency peaks and troughs of the twin microcharcoal curves were found to correspond well suggesting that microcharcoal records from small peat mires within forested catchments have fine spatial integrity are reproducible and can be interpreted securely as reliable records of fire history in their small source areas much variation occurred at the level of individual spectra within coeval zones which must record the same fire history and ecology however producing differently shaped microcharcoal curves while the record of major trends will be accurate therefore too precise an interpretation of microcharcoal data at this temporal scale may not be justified micro spatial variations in frequencies of fungal spores associated with local burning are also presented and evaluated

review and update of the applications of organic petrology part 1 geological applications abstract organic petrology developed as coal petrology at the beginning of the 20th century dedicated mainly to the study of coals because of their utilization in industry coal petrology was then considered a branch of coal science later with the development of specialized nomenclature classification of coal components and the standardization and improvement of analytical microscopical methods this discipline expanded in interests and name becoming organic petrology organic petrology carries a broader context being as well a tool applied in the study of dispersed organic matter in sedimentary rocks due to its importance in exploration for fossil fuel resources at present organic petrology is a discipline widely recognized for its role in fundamental and applied research with respect to both coal utilization and in geosciences throughout the 20th century several important monographs have been published on the discipline of organic petrology including stach s textbook of coal petrology 1st edition 1935 2nd 1975 3rd 1982 updated as the more general organic petrology by taylor et al 1998 more recently the text applied coal petrology the role of petrology in coal utilization was published by suarez ruiz and crelling 2008 this review is the first in a two part review series that describes and updates the role of organic petrology in geosciences a second part complementing this one and focused on the applications of organic petrology to other scientific fields will follow

peat stratigraphy and changes in peat formation during the holocene in latvia mires represented by raised bogs fens and transitional mires cover approximately 10 of latvia they started to form towards the end of the last glacial period and the beginning of the holocene under varying geological and palaeoecological conditions the aim of the study was to evaluate how the results of peat palaeobotanical investigation can reveal changes in the conditions of peat formation and allow a subdivision to be made of the holocene according to the scheme suggested by the intimate group walker et al 2012 records from 21 mires have been evaluated to find evidence of changes in mire vegetation and peat formation and to discover whether these records define boundaries allowing the holocene deposits to be subdivided into the early holocene middle holocene or the holocene thermal maximum htm and the late holocene information from earlier studies and data from recent investigations are used for the revision of peat stratigraphy revision peat accumulation and fen formation during the early holocene took place in the oldest mires which started to develop by the infilling of shallow lake depressions during the second part of the early holocene before 9500 cal yr bp the climate became warmer and less humid and the eutrophic plant species were gradually replaced by mesotrophic species at the end of the early holocene parts of fens gradually turned to transitional mires and the first layers of raised bog peat started to form the boundary between the early and middle holocene or the htm can be established at the interval of 8100 to 8000 cal yr bp based on sharp changes in peat formation conditions the further development of raised bogs and fens including coastal areas where ground paludification and bog development in the depressions caused by groundwater rise because of water level rise due to transgression of the baltic sea littorina sea stage took place the boundary between the htm and the late holocene in this study is established at 4200 cal yr bp as suggested by the intimate group during the late holocene the bog plant phytocenoses were formed essentially of sphagnum and cotton grass which on decay produced slightly decomposed sphagnum magellanicum sphagnum fuscum and sphagnum cotton grass peat an intensive accumulation of peat occurred all over followed by intensive development of bog cupolas after the regression of the littorina sea stage of the baltic sea terrestrialisation processes and peat formation were initiated in the former lagoonal areas the interdune mires started to form in the north western coastal area of latvia before 3500 3000 cal yr bp this study shows that pollen nonpollen and the botanical composition of peat in mire deposits together with 14c dating can yield valuable information about environmental conditions during peat accumulation and provide insights into peat stratigraphy which help to understand the development of mires and mire ecosystems the findings of this study and comparison with earlier work enable us to conclude that peat stratigraphy and the subdivision of the holocene in latvia can generally use the scheme suggested by the intimate group walker et al 2012 however the local peculiarities of mires should also be taken in account

the performance of single and multi proxy transfer functions testate amoebae bryophytes vascular plants for reconstructing mire surface wetness and ph peatlands are widely exploited archives of paleoenvironmental change we developed and compared multiple transfer functions to infer peatland depth to the water table dwt and ph based on testate amoeba percentages or presence absence bryophyte presence absence and vascular plant presence absence data from sub alpine peatlands in the se swiss alps in order to 1 compare the performance of single proxy vs multi proxy models and 2 assess the performance of presence absence models bootstrapping cross validation showing the best performing single proxy transfer functions for both dwt and ph were those based on bryophytes the best performing transfer functions overall for dwt were those based on combined testate amoebae percentages bryophytes and vascular plants and for ph those based on testate amoebae and bryophytes the comparison of dwt and ph inferred from testate amoeba percentages and presence absence data showed similar general patterns but differences in the magnitude and timing of some shifts these results show new directions for paleoenvironmental research 1 suggesting that it is possible to build good performing transfer functions using presence absence data although with some loss of accuracy and 2 supporting the idea that multi proxy inference models may improve paleoecological reconstruction the performance of multi proxy and single proxy transfer functions should be further compared in paleoecological data

temporal organic facies variations of upper jurassic lowermost cretaceous source rocks in the danish central graben north sea abstract the upper jurassic lowermost cretaceous marine mudstones of the farsund formation constitute the principal source rocks in the danish north sea sector with the uppermost bo member considered most prolific however the areal distribution of the bo member is limited and since it is thermally immature over large areas it is unlikely that this interval has generated sufficient quantities of petroleum to fill the reservoirs in the danish sector in search for additional source rocks potential we have investigated the lower part of the farsund formation using a sequence stratigraphic framework organic geochemical screening and petrographic analyses of core and cuttings samples have been performed to define the source potential and map the regional distribution of organic rich sequences in the upper jurassic succession the study outlines variations of both maturity source rock quality and kerogen quality at sequence level with an upward improvement from poor gas prone type ii kerogen in the kimm 1 and kimm 3 sequences to highly oil prone type ii kerogen in the volg 1 volg 4 and ryaz 1 sequences the kerogen is dominated by fluorescent aom and liptinite and structural alginite in form of leiosphaerida and tasmanites type telalginites throughout the entire succession with vertical and regional variations in the amount of larger tasmanites the study shows that the shales in volg 1 and 3 sequences are organic rich and oil prone with toc 4 wt and hi 340 mg hc g toc particularly the volg 1 sequence being the thickest and laterally most widespread forms a significant supplementary source for oil in the danish sector

geochemical characteristics and hydrocarbon generation modeling of the kazhdumi early cretaceous gurpi late cretaceous and pabdeh paleogene formations iranian sector of the persian gulf abstract the marls and argillaceous limestones of the early cretaceous kazhdumi late cretaceous gurpi and paleogene pabdeh formations are considered as potential source rock candidates in this area the present study characterizes hydrocarbon potential type of organic matter and thermal maturity of these three formations in the iranian sector of the persian gulf also 1d basin modeling was used to analyse the burial history and timing of hydrocarbon generation in these formations a total of 179 cutting samples from 25 wells were evaluated through rock eval pyrolysis and organic petrography average total organic carbon toc content for the samples of the kazhdumi gurpi and pabdeh formations that were analyzed for the current study is 1 2 0 9 and 1 wt respectively all three formations show lower toc contents in central part relative to eastern and western parts of the study area rock eval pyrolysis and organic petrography show that the organic matter in all three formations is mainly composed of type ii and mixed type ii iii kerogen this study shows that the kazhdumi gurpi and pabdeh formations in iranian offshore areas are not as rich as onshore areas and specifically in the dezful embayment in terms of organic matter quantity and quality thermal history modeling indicates that constant heat flow values in the range of 64 73 mw m 2 gives the best fit between measured and calculated vitrinite reflectance and bottom hole temperature the rock eval t max vitrinite reflectance and the generated models suggested that in the eastern parts of the study area the kazhdumi formation is at the last stage of oil generation and the gurpi and pabdeh formations are within the main oil generation window hydrocarbon generation began in the early eocene middle eocene and early miocene in the kazhdumi gurpi and pabdeh formations respectively in the western parts of the persian gulf the kazhdumi formation is within the main oil window with hydrocarbon generation took place during the oligocene and the gurpi and pabdeh formations are early mature and immature respectively all three formations are thermally immature in the central part of the persian gulf the kazhdumi formation shows positive correlation with the crude oils of the cretaceous and tertiary reservoirs taken from the northwestern persian gulf the pabdeh and gurpi formations show no correlation with crude oils produced in the northwestern and southeastern persian gulf

vitrinite and vitrinite like solid bitumen reflectance in thermal maturity studies correlations from diagenesis to incipient metamorphism in different geodynamic settings abstract vitrinite reflectance vr is a useful and reliable parameter to monitor the level of organic matter maturation from the immature stage to graphite additionally vr is a useful and essential tool in modelling the temperature maturation time path huminite vitrinite bearing sedimentary and meta sedimentary rocks can be used to reconstruct the thermal history of basins or orogenic terranes throughout their geological history the usefulness of vr evidently depends on the presence of huminite vitrinite phytoclasts however pre upper silurian rocks and many organic rich marine rocks e g sapropelic sediments lack of huminite vitrinite particles furthermore vitrinite is sparse in carbonate sediments however the presence of bitumen in rocks lacking type iii kerogen provides a valuable aid via its reflectance vitrinite like solid bitumen reflectance vlbr and or solid bitumen reflectance br to fulfil the above described tasks that vr enables this study presents basically a relationship between br vlbr and vr for various types of geodynamic settings and over the largest possible range of maturation levels so that vlbr may be used as a substitute for vr whereas the effort to correlate vr with br is not novel it is the first time that the vr br correlation is re judged discriminating bitumen from vlb moreover for the first time the correlation is established for various geodynamic settings the investigated geological contexts are 1 sedimentary basins e g the saar ruhr ohio west virginia and petrosani basins 2 metasedimentary terranes occurring as inverted basins in orogenic belts e g from the subalpine molasse helvetic austroalpine and danubian nappe systems and having suffered from very low to low grade metamorphism from anchizone to greenschist facies 3 metasedimentary terranes e g slates and schists from the franciscan and alpine belts that were subducted at anchizone to blueschist facies conditions and 4 metasedimentary rocks affected by contact metamorphism together the frequent geological settings are referred and most of the earth geothermal conditions and heat fluxes considered despite temperature pressure and heating time also heat flow gradient dependences cannot be ignored

a 2800 year palaeoclimatic record from tore hill moss strathspey scotland the need for a multi proxy approach to peat based climate reconstructions analyses of plant macrofossils testate amoebae and humification have been carried out on a 2800 year core from tore hill moss a raised bog in the strathspey region of scotland all three analyses were carried out at the same 4 cm intervals allowing exact correlation and the core was dated by nine accelerator mass spectrometry radiocarbon dates and the glen garry tephra layer the results have been combined and compared to present a bog surface wetness bsw record within which the limitations of each proxy method can be assessed and this has highlighted the advantages of a combined rather than a single proxy approach significant wet shifts are recorded at ca cal 560 bc 60 bc ad 430 ad 570 ad 700 ad 1090 and ad 1640 significant shifts to drier periods are also suggested ca cal ad 220 ad 500 and ad 820 some of the recorded shifts and phases are related to phases of wetter and drier climate such as the sub boreal sub atlantic transition the dark age deterioration and the romano british warm period the dark ages are notable as a period of rapid peat accumulation and frequent water table fluctuations time series analysis revealed a significant wet shift cycle of 560 years from the testate amoebae data

organic matter pores and oil generation in the tuscaloosa marine shale the upper cretaceous tuscaloosa marine shale tms is an oil play across central louisiana and southwest mississippi the lower tms is characterized by relatively high log resistivity 5 ohm m compared to the upper part and this elevated resistivity zone erz has become the primary target zone this study is to investigate the cause of variation in log resistivity based on the data of petrography mineralogy and organic matter property and porosity the results suggest that log resistivity is not controlled by mineralogy or porosity rather it is associated with oil generation during organic matter maturation total organic carbon toc content rock eval free hydrocarbon yield s1 and hydrogen index hi in the studied core increase with depth porosity within organic matter om measured by field emission scanning electron microscopy fe sem is also higher within the erz the correlated variations among toc content s1 values om porosity and log resistivity suggest that the higher log resistivity resulted from in situ oil generation and that the om pores were generated during oil generation thermal maturity varies little in the core whereas the downward increasing hi indicates an increasing abundance of oil prone type ii kerogen higher om porosity appears to be related to the greater proportion of type ii kerogen in the erz the data set demonstrates that higher contents of toc and oil prone kerogen are the combined factors for higher oil generation therefore higher log resistivity in the erz the study provides a quantitative relationship between om porosity and oil generation

limitations of use of organic petrographic techniques for identification of petroleum source rocks organic petrographic and organic geochemical studies have been conducted on 58 sediment samples of differing ages and depositional environments in this study interpretations of petroleum source rock potential based on data from transmitted light microscopy show a poor correlation with those derived from chemical data this lack of correlation arises from the failure to distinguish consistently between hydrogen poor and hydrogen rich amorphous organic matter and inability to detect hydrogen rich components exinite and resinite in coal fragments interpretations based on data from reflected light microscopy show a better correlation with those derived from chemical studies but difficulties still remain these difficulties arise from inability except on the basis of luorescence intensity to distinguish hydrogen rich from hydrogen poor organic matter in a finely dispersed state

a sensitive high resolution record of late holocene climatic change from a raised bog in northern england proxy climatic data in the form of plant macrofossils have been analysed from a 5 m core from bolton fell moss cumbria uk detailed analysis of peat from the upper 50 cm of this core is used to demonstrate a strong correlation between changes in the relative proportion of taxa and known climatic changes over the last 1000 years the record of changes in bog vegetation contained within the peat profile is used to reconstruct changes in bog surface wetness for the latter half of the holocene as bog surface wetness is directly controlled by the prevailing climatic conditions this reconstruction can be viewed as a proxy climate record twelve radiocarbon age estimates on the 5m core suggest that between 50 and 500 cm peat accumulated at a relatively constant rate of 12 4 yr cm 1 the regular sampling intervals thus provide a time series of past bog surface wetness spectral analyses of this series indicates that wetness changes are cyclic with a ca 800 year periodicity

replicability and variability of the recent macrofossil and proxy climate record from raised bogs field stratigraphy and macrofossil data from bolton fell moss and walton moss cumbria england replication of results is a basic tenet of science but in palaeoecology this is very time consuming and the signal is subject to noise the derivation of proxy climate signals from ombrotrophic peat was carried out originally using samples from open peat faces where the stratigraphic relationships could be easily observed now that such sections are rare and often degraded there is a need to demonstrate that data can be replicated from core profiles ten short cores taken from two adjacent bogs have been analysed for macrofossils and show a coherent series of changes which are also similar to previous profiles from the same sites it is concluded that variation between profiles is slight and less than observations of present vegetation mosaics might suggest recommendations for a standard approach to fieldwork on raised bogs that emphasises the utility of subfossil pool layers are proposed and the need for a secure chronology is stressed 1998 john wiley sons ltd

environmental change in nw iberia between 7000 and 500 cal bc abstract we review research done on environmental changes in northwest nw iberia spanning from the beginning to the late holocene 7000 500 cal bc the type of archives peat bogs lake sediments colluvium soils etc and proxies pollen element concentrations isotopes etc that were used to reconstruct changes on climate soils vegetation and atmospheric metal pollution are briefly described then we synthesize what the records suggest about the ecological history of nw iberia we identified four main phases 7000 5000 5000 3000 3000 1500 and 1500 500 cal bc each phase is determined by a set of environmental conditions a combination of changes in climate vegetation soils and human impact human activities seem to have been involved in landscape changes in nw iberia since at least 5000 cal bc with an increasing degree of anthropisation through time which accelerated by 1500 cal bc the interaction between human activities and natural changes expressed as modifications in the vegetation cover the elimination of the soil resources in many areas and its concentration in more localized control demanding sectors as well as a progressive acidification and pollution of continental ecosystems to a great extent the present landscape in nw iberia is the end product of these complex interactions a cultural landscape

paleoecology and high resolution paleohydrology of a kettle peatland in upper michigan we investigated the developmental and hydrological history of a sphagnum dominated kettle peatland in upper michigan using testate amoebae plant macrofossils and pollen our primary objective was to determine if the paleohydrological record of the peatland represents a record of past climate variability at subcentennial to millennial time scales to assess the role of millennial scale climate variability on peatland paleohydrology we compared the timing of peatland and upland vegetation changes to investigate the role of higher frequency climate variability on peatland paleohydrology we used testate amoebae to reconstruct a high resolution hydrologic history of the peatland for the past 5100 years and compared this record to other regional records of paleoclimate and vegetation comparisons revealed coherent patterns of hydrological vegetational and climatic changes suggesting that peatland paleohydrology responded to climate variability at millennial to sub centennial time scales although ombrotrophic peatlands have been the focus of most high resolution peatland paleoclimate research paleohydrological records from sphagnum dominated closed basin peatlands record high frequency and low magnitude climatic changes and thus represent a significant source of unexplored paleoclimate data

determining the sun s influence on lateglacial and holocene climates a focus on climate response to centennial scale solar forcing at 2800 cal bp abstract the influence of solar variability on the climate of the lateglacial and holocene periods has been the subject of increasing discussion during the last decade in the mid holocene several studies have identified cold wet events that occur at ca 2800 cal bp and a link with a reduction in solar activity inferred from the 14c record has been postulated we present results from a multi proxy study of peat humification plant macrofossils and testate amoebae from a raised bog at glen west northwest ireland that indicate that dry bog surface conditions were experienced in the north of ireland at the time of the solar anomaly starting at 2800 cal bp with the aid of 14c wiggle matching and tephrochronology an abrupt shift to wetter conditions is dated to ca 2700 cal bp coinciding with a 14c maximum but clearly post dating the 2800 cal bp event identified elsewhere in europe we explore the significance of this apparent lag in the irish record considering the possible role of the ocean in generating spatial and temporal complexities in the climate patterns of the north atlantic region we conclude that these complexities are likely to give rise to time transgressive climate responses around the north atlantic that will only be recognised by more critical chronological approaches

snapshots in time precise correlations of peat based proxy climate records in scotland using mid holocene tephras mid holocene tephra layers have been located and geochemically analysed from seven ombrotrophic bogs in scotland the tephras found in these scottish peats occur as stratigraphically discrete horizons not visible to the naked eye and originate from volcanic activity in iceland identifying and geochemically typing the tephra layers can enable precise correlations between sites on regional scales depending on the spatial extent of the airfall events dispersal of both the glen garry and hekla 4 tephras is excellent over scotland enabling snapshot views of the past at the time of these tephra depositions palaeoecological analyses have also been undertaken on these bogs providing detailed reconstructions of past changes in bog vegetation and surface wetness a proxy for past climates correlations between the ombrotrophic bogs at the time of the glen garry tephra revealed significant differences between the proxy climate records in the north and the south of scotland suggesting asynchronous changes between northern scotland and the rest of great britain

regional climate change from peat stratigraphy for the mid to late holocene in central ireland at the millennial scale bog surface wetness bsw records show a clear holocene climate event stratigraphy with major phases comparable with other regional climate proxies such as chironomid inferred temperature records moving towards the centennial scale however and towards the limits of chronological certainty within the records regional differences are apparent which likely reflect the more heterogeneous precipitation patterns which occur on shorter timescales the bsw data presented in this paper are reconstructed from testate amoebae assemblages from central ireland and are compared with other regional records the results suggest that this region is in phase with the north of ireland in terms of timings and durations of climate change but the comparisons are less clear with a stacked and tuned record from northern britain that shows an apparent offset compared to the irish records this may reflect variations in past regional precipitation or be a function of the tuning and stacking process the broad phases of comparison between the irish records and the extension of the central irish record back to 6000 cal bp allow comparisons with low frequency temperature reconstructions from chironomids which also show a broad level of correlation with cooler temperatures relating to wetter bsw at centennial to millennial timescales

a proxy record of late holocene climate change from may moss northeast england quantitative reconstruction of changes in mire surface wetness has been used to reconstruct proxy climate from an upland ombrotrophic blanket mire on the north york moors in northeast england may moss testate amoebae plant macrofossil and humification analyses were carried out for six peat profiles transfer functions are used to generate estimates of water table levels from the testate amoebae stratigraphy which complement the semi quantitative indications of changing surface wetness provided by plant macrofossil and humification analysis 14c dates provide the chronology for the stratigraphy differences were encountered between ams 14c dates on pure sphagnum remains and radiometric dates on bulk peat from the same horizon which perhaps arise from the heterogeneity of peat replicate palaeoecological analysis of adjacent cores identifies consistency within testate amoebae and plant macrofossil stratigraphies and reveals a strong agreement between the water table level proxies the record of hydrological changes at sites across may moss are in synchrony and so climate change is the most likely cause of the moisture fluctuations changes to a wetter or cooler climate were identified cal ad 260 540 ca ad 550 650 cal ad 670 980 ca ad 1350 1450 cal ad 1400 1620 and ca ad 1700 1800 periods with a drier or warmer climate precede all of these wet shifts with particularly dry periods between cal ad 650 860 and 690 980 and between cal ad 1290 1410 and 1400 1620 copyright 2001 john wiley sons ltd

effects of extraction protocols on the oxygen isotope composition of conodont elements abstract oxygen isotopic measurements of conodont elements can provide important paleoclimatic paleoecological and paleoenvironmental information however preparation techniques are often cited as a potential albeit poorly constrained source of error prior to isotopic measurements conodont elements are typically liberated from a calcium carbonate matrix using dilute solutions of acetic or formic acid these extraction techniques are well established for paleontological studies but the protocols were established before conodonts became a common target for isotopic analyses whereas concerns are often raised about the possibility of bias introduced through phosphate leaching especially with stronger acid empirical observations regarding error in isotopic measurements introduced due to the preparation techniques used are limited and generally anecdotal this study was designed to constrain the effects different types of acids used for carbonate digestion have on the measured oxygen isotopic compositions of bioapatite specifically conodont elements and brachiopod shells we performed parallel analyses on splits from seven late ordovician samples that were processed with both buffered and unbuffered solutions of acetic and formic acid in addition to further assess the potential for 18o alteration related to partial apatite dissolution we forced partial dissolution of isolated conodont elements by placing them in an unbuffered formic solution for varying intervals of time prior to analysis measured 18o values from conodont elements and brachiopod shell fragments show no statistically significant differences related to processing technique but isolated conodont elements with visible evidence of partial dissolution due to prolonged exposure to unbuffered formic acid record consistently offset 18o values such partially dissolved elements should be avoided in geochemical studies if specimens exhibiting apparent etching are avoided though we conclude that standard digestion protocols for conodont element extraction from carbonates do not introduce a bias either a systematic offset or an increase in variance on measured 18o values from phosphate bound oxygen in bioapatite above the limits of the resolution of this study

late holocene climatic changes in tierra del fuego based on multiproxy analyses of peat deposits a ca 1400 yr record from a raised bog in isla grande tierra del fuego argentina registers climate fluctuations including a medieval warm period although evidence for the little ice age is less clear changes in temperature and or precipitation were inferred from plant macrofossils pollen fungal spores testate amebae and peat humification the chronology was established using a 14c wiggle matching technique that provides improved age control for at least part of the record compared to other sites these new data are presented and compared with other lines of evidence from the southern and northern hemispheres a period of low local water tables occurred in the bog between a d 960 1020 which may correspond to the medieval warm period date range of a d 950 1045 generated from northern hemisphere tree ring data a period of cooler and or wetter conditions was detected between ca a d 1030 and 1100 and a later period of cooler wetter conditions estimated at ca cal a d 1800 1930 which may correspond to a cooling episode inferred from law dome antarctica

archaeological applications of testate amoebae analyses a case study from derryville co tipperary ireland the value of testate amoebae in the reconstruction of changes in surface wetness from ombrotrophic mires is well known but the potential value of such records in specifically archaeological investigations has not yet been investigated this note describes the analysis of testate amoebae for a sediment sequence from the multi period wetland archaeological site of derryville co tipperary ireland the reconstructed watertable is presented and plotted against the range of dates from excavated archaeological features in the wetland area the data demonstrate a clear association between periods of low watertable and increased anthropogenic activity as reflected by site construction the value of testate amoebae in future integrated archaeological investigations of wetland systems is discussed

proxy climate record for the last 1000 years from irish blanket peat and a possible link to solar variability recent research has shown that ombrotrophic mires can yield a proxy climate signal based on changes in the degree of peat humification 1 2 and that oceanic margin sites show the most sensitive record 3 we compare humification records for the last 1000 yr from two radiocarbon dated blanket peat profiles from western ireland and show several corresponding periods of climatic fluctuations periods favouring reduced peat decomposition suggestive of wetter and or cooler climatic conditions seem to coincide with periods of reduced sunspot activity and atmospheric14c anomalies whilst climatologists have continued to debate a link between solar variability on a century timescale and climate change the exact nature of that link remains elusive 4 7 the results from ireland demonstrate that data derived from mires could be relevant to the debate as to the extent of solar forcing in natural climatic variability and the curves shown provide a continuous record to add to previous evidence for the so called medieval optimum and little ice age 8 the record may imply that during the past millennium climatic change at the oceanic margin of the northeast atlantic largely corresponded to inferred variations in solar output

widespread drought episodes in the western great lakes region during the past 2000 years geographic extent and potential mechanisms we compared high resolution reconstructions of peatland water table depth at two raised bogs in the western great lakes region separated by 1000 km the sites included minden bog in southeastern michigan and hole in the bog in north central minnesota our objectives were to 1 determine whether large decadal to multidecadal droughts of the past 2000 yrs were spatially and temporally coherent across the region and 2 assess the underlying mechanisms of widespread droughts in the region we found a strong correlation between bog inferred records of moisture variability in the two regions r 0 53 between 2100 and 600 bp extreme drought events centered on 1850 1800 1650 1000 800 and 700 bp are recorded in both regions many of these drought events were contemporaneous with large droughts already documented at sites far to the west in the great plains and rocky mountains to identify potential modern climate analogues we used empirical orthogonal function eof analysis to reveal spatial modes of variability in drought and precipitation records of north america for the past century the first eofs of annual precipitation and palmer drought severity index pdsi were similar to each other and consistent with a pattern of widespread continental drought correlations between these eofs and annual sea surface temperatures ssts indicate strong relationships to ssts in both the atlantic and pacific basins we hypothesize that widespread droughts between 1000 and 700 bp were related to amplification of a spatial mode of moisture variability associated with an anomalously warm north atlantic a warm mid latitude north pacific and an anomalously cold tropical pacific a more extensive network of hydroclimate records developed using a consistent set of methods and proxies could be used in conjunction with high resolution records of past ssts to test this hypothesis

holocene shelf sea seasonal stratification dynamics a dinoflagellate cyst record from the celtic sea nw european shelf published records of the holocene evolution of seasonal stratification in the celtic sea nw european shelf have been based on benthic proxies notably benthic foraminifera and associated stable isotopic data we have investigated organic walled dinoflagellate cyst assemblages from a well dated holocene sequence from the central celtic sea in order to assess the signal from this planktonic proxy and to reconstruct paired bottom and surface water conditions through time this sequence has on the basis of the benthic proxies been interpreted previously as a record of the replacement of tidally mixed water by stratified water associated with tidal front migration during the early holocene interpretation of the dinocyst record has been facilitated by a parallel study of the distribution of cysts from celtic sea surface sediments and their relationship with seasonal water masses the dinocyst stratigraphy indicates mixed water conditions during the early holocene consistent with reduced water depths hence lowered sea level over the core site the first significant change in the dinocyst assemblages is recorded at around 6650 cal years bp and indicates a transition from mixed frontal conditions to seasonal stratification this interpretation of frontal migration is consistent with changes in the benthic foraminiferal assemblages and associated stable isotopes at the same core depth from 6650 to 3600cal years bp the significant occurrence of bitectatodinium tepikiense accompanied by spiniferites elongatus is attributed to strong seasonality with winter sea surface temperatures possibly below 5 c another transition at 3600cal years bp is attributed to a reduction in seasonality generated by milder winter conditions linked to a stronger influence of the thermohaline circulation over the studied area this transition is not recorded by the benthic proxies and is attributed to climate forcing rather than to any change in tidal dynamics it is notable that many mires in western britain record distinct wet shifts contemporary with this change

source rock dispersed organic matter characterization tsop research subcommittee results abstract because sedimentary organic matter consists of a diverse mixture of organic components with different properties a combination of chemcial and petrographic results offers the most complete assessment of source rock properties the primary purpose of this society for organic petrology tsop subcommittee is to contribute to the standardization of kerogen characterization methods specific objectives include 1 evaluation of the applications of different organic matter petrographic classifications and terminology and 2 integration of petrographic and geochemical results these objectives were met by completing questionnaires and petrographic geochemical and photomicrograph round robin exercises samples that were selected for this study represent different petrographic and geochemical properties and geologic settings to help identify issues related to the utilization of different classifications and techniques petrographic analysis of the organic matter was completed using both a prescribed classification and the individual classification normally used by each participant total organic carbon toc rock eval pyrolysis and elemental analysis were also completed for each sample significant differences exist in the petrographic results from both the prescribed and individual classifications although there is general agreement about the oil vs gas prone nature of the samples comparison of results from individual classifications is difficult due to the variety of nomenclature and methods used to describe an organic matter assemblage results from the photomicrograph exercise document that different terminology is being used to describe the same component although variation in toc and rock eval data exists geochemical results define kerogen type and generative potential recommendations from this study include 1 1 a uniform organic matter classification must be employed which eliminates complex terminology and is capable of direct correlation with geochemical parameters 2 2 a standardized definition and nomenclature must be used for the unstructured amorphous organic matter category subdivisions of this generalized amorphous category are needed to define its chemical and environmental properties 3 3 standardized techniques including multimode illumination types of sample preparations and data reporting will help eliminate variability in the type and amount of organic components reported

a multiproxy climate record from a raised bog in county fermanagh northern ireland a critical examination of the link between bog surface wetness and solar variability a proxy climate record from a raised bog in county fermanagh northern ireland is presented the record spans the interval between 2850 cal yr bc and cal yr ad 1000 and chronological control is achieved through the use of tephrochronology and 14c dating including a wiggle match on one section of the record palaeoclimatic inferences are based on a combination of a testate amoebae derived water table reconstruction peat humification and plant macrofossil analyses this multiproxy approach enables proxy specific effects to be identified major wet shifts are registered in the proxies at ca 1510 cal yr bc 750 cal yr bc and cal yr ad 470 smaller magnitude shifts to wetter conditions are also recorded at ca 380 cal yr bc 150 cal yr bc cal yr ad 180 and cal yr ad 690 it is hypothesised that the wet shifts are not merely local events as they appear to be linked to wider climate deteriorations in northwest europe harmonic analysis of the proxies illustrates statistically significant periodicities of 580 423 373 307 and 265 years that may be related to wider holocene climate cycles this paper illustrates how the timing of climate changes registered in peat profiles records can be precisely constrained using tephrochronology to examine possible climatic responses to solar forcing relying on interpolated chronologies with considerable dating uncertainty must be avoided if the climatic responses to forcing mechanisms are to be fully understood copyright 2007 john wiley sons ltd

multiproxy surface wetness records from replicate cores on an ombrotrophic mire implications for holocene palaeoclimate records ombrotrophic mires can provide records of palaeoclimate over the mid to late holocene in several areas of the world their potential is currently partly limited by difficulties with scaling indices based on plant macrofossils and humification and the need to account for the internal variability of the mire system this paper explores the use of testate amoebae analysis as a third technique and assesses the minimum within site variability by comparing results from two closely spaced cores reconstruction of surface wetness changes was carried out on cores from the centre of an intermediate raised blanket mire coom rigg moss northumberland by analysis of testate amoebae plant macrofossils and humification surface wetness changes were expressed as mean annual water table changes inferred from testate amoebae assemblages two separate indices based on plant macrofossils and percentage transmission of humification extracts comparisons between the proxies suggest good agreement of general trends in sphagnum peats but some differences in monocot and ericaceous peats the magnitude of surface wetness changes also differs within sphagnum peats the records from the separate cores converge over time and replicability between cores is best in the last 1000 yr changes over this period are similar to those shown by estimates based on documentary sources good agreement is obtained between a normalised plant macrofossil index and normalised reconstructed water table values and it is suggested that this approach could form the basis for improved composite multiproxy records from peatlands copyright 1999 john wiley sons ltd

a 7500 year peat based palaeoclimatic reconstruction and evidence for an 1100 year cyclicity in bog surface wetness from temple hill moss pentland hills southeast scotland analyses of plant macrofossils peat humification and testate amoebae were used to reconstruct a proxy climate record spanning the last 7500 years from an ombrotrophic bog temple hill moss in southeast scotland the plant macrofossil data were subjected to detrended correspondence analysis dca which modelled effectively the significant wet shifts within the record a mean water table depth transfer function was applied to the testate amoebae data to provide quantifiable changes the three proxy records show coherent phase changes which are interpreted as variability in past effective precipitation two tephra horizons glen garry and lairg a were used in conjunction with radiocarbon dates to construct an age depth model producing a robust geochronology from which a time series was calculated the palaeoclimatic reconstruction identified major wet shifts throughout the holocene with specific events occurring around cal 6650 5850 5300 4500 3850 3400 2800 2450 1450 1350 and 250 150 bp spectral analysis of the plant macrofossil dca and colorimetric humification data produced a millennial scale periodicity of 1100 years the same periodicity has also been found in a palaeoclimatic reconstruction from a site in cumbria walton moss and may be linked with millennial scale periodicities found in oceanic palaeoclimatic records