geologic evolution of the iraqi zagros and its influence on the distribution of hydrocarbons in the kurdistan region whereas the vast majority of discovered hydrocarbon reserves in iraq reside in cretaceous and cenozoic reservoirs numerous oil and gas fields have been discovered recently in deeper jurassic and triassic reservoirs in the kurdistan region of iraq this study presents a middle upper jurassic thermal maturity map for the kurdistan region of iraq and demonstrates that regional first order trends in jurassic source rock maturity show a close correlation to the spatial distribution of oil gravities within the overlying jurassic and cretaceous reservoirs this distribution is consistent with compartmentalization of the active source rock kitchens due to zagros folding resulting in relatively short distance migration and charge of the anticlinal structures from the adjacent synclinal lows the thermal maturity map confirms relatively low maturity over the mosul high where the cretaceous and cenozoic section overlying the source rock interval is relatively thin and increasing maturity to the southeast as the thickness of the cenozoic foredeep sediments increases toward the depocenter located in the southeastern iraqi zagros and the adjacent iranian zagros the correlative trend in oil gravities is exemplified by the recent jurassic discoveries low to medium gravity oils 14 27 api in shaikan and atrush to the northwest light oil 39 47 api in mirawa and bina bawi and gas condensate 55 api in miran west to the southeast understanding thermal maturity patterns and hydrocarbon fluid type distributions will help to guide risk assessment for remaining prospectivity and future exploration drilling within the kurdistan region of iraq

multi proxy evidence of holocene climate variability in volhynia upland se poland recorded in spring fed fen deposits from the komarow site radiocarbon dated spring fed fen deposits from the komarow site volhynia upland se poland with its multi proxy data macrofossils molluscs geochemistry pollen stable isotopes of oxygen and c

chronology and directions of late glacial paleoenvironmental changes a multi proxy study on sediments of lake slone se poland the article presents the results of a multi proxy study on sediments of lake slone chelm hills located in the northern peripheral area of the lublin upland se poland the area remained in the periglacial zone with permafrost present in the geological substrate during the last glaciation this paper represents an attempt to determine the directions and intensity of changes in environmental conditions during the late glacial it also attempts to reconstruct lake development conditions within the area unaffected by the extent of the ice sheet the aim of the study was to investigate bottom sections of two sediment profiles representing the period of late glacial lake mire sedimentation occurring in varying thermal and humidity conditions conditions were indicated by lithological variations in the sediments and the content of micro and macrofossils the latter were identified based on palynological and malacological analyses as well as by subfossil ostracoda and cladocera analysis the chronology of the identified paleoenvironmental changes was determined based on the results of paleobotanical analysis in correlation with radiocarbon dating conventional and ams of the selected sediment layers the results were compared to other sites from north central europe and to the well dated laminated sediments sequences from the nearest late glacial site at perespilno it was estimated that the development of lake slone probably had its origin in the older dryas the development of the lake basin in turn is associated with specific processes of disappearance of permafrost in the upper cretaceous bedrock

thermal evolution of the kuh e asmari and sim anticlines in the zagros fold and thrust belt implications for hydrocarbon generation abstract mixed layer clay minerals vitrinite reflectance and geochemical data from rock eval pyrolysis were used to constrain the burial evolution of the mesozoic cenozoic successions exposed at the kuh e asmari dezful embayment and sim anticlines fars province in the zagros fold and thrust belt in both areas late cretaceous to pliocene rocks show low levels of thermal maturity in the immature stages of hydrocarbon generation and early diagenetic conditions r0 i s and ro values

palaeoclimate change recorded in upper cretaceous albian cenomanian kazhdumi formation borehole spectral gamma ray logs south pars gas field persian gulf abstract th u and th k data from spectral gamma ray logs obtained from outcrop successions have been used as a rapid and inexpensive proxy for determining possible episodes of humid arid palaeoclimate change such outcrop based measurements have never been tested using spectral gamma ray data obtained from wireline logs in subsurface boreholes th k and th u ratios have traditionally been used to decipher sequence stratigraphic patterns at outcrop and in borehole the possible influence of palaeoclimate on such ratio changes has yet to be proven especially from borehole data in this work we compare borehole derived th k and to a lesser extent th u to palaeoenvironmental changes inferred from palynology and deduce that both sea level and changing hinterland weathering regimes caused discrete fluctuations observed in the spectral gamma ray logs this is the first time such subsurface information has been used in this way interpretation of wireline logs in terms of palaeoclimate as well as sea level may now be considered and the use of such logs in palaeoclimate reconstruction is strengthened

hydrocarbon reserves of gachsaran oilfield sw iran geochemical characteristics and origin abstract biomarkers and carbon isotope data were used to depict geochemical properties and to delineate source of the crude oils from asmari and bangestan reservoirs of the giant gachsaran oilfield sw iran despite the distinct horizons of the reservoirs and severe petrophysical heterogeneity inside each reservoir all oil samples show an identical level of thermal maturity furthermore similar source related parameters reflect identical source rock for both reservoirs they indicate carbonate marl source deposited in a marine environment under anoxic suboxic conditions strong marine organic matter signatures of predominantly algal origin along with evidence of a terrigenous angiosperm plant contribution were detected geochemical evidence suggests that the gachsaran field asmari and bangestan oils being sourced from a mix of organic rich kazhdumi and pabdeh source rocks of albian and middle eocene early oligocene ages respectively carbon isotope composition and v ni ratio signatures indicate kazhdumi formation as the main source rock meanwhile significant presence of oleanane and less than unity values of c 29 c 30 hopanes ratio demonstrate a partial contribution of pabdeh formation this contradiction could be explained by two scenarios 1 incorporating very immature non expelled pabdeh oils into the mature kazhdumi oils during migration or 2 partial charge form low maturity pabdeh oils that is insufficient to impact a typical mixed signature over the geochemical fingerprint of the reservoired oils additionally geochemical similarities give rise to an assumption of reservoir and trap inter connection for this giant field

2d basin modeling study of the binak trough northwestern persian gulf iran abstract the northwestern part of the persian gulf is one of the most prominent hydrocarbon exploration and production areas oilfields are located in structural highs formed around the cenomanian depression known as binak trough to evaluate the highly variable source rock maturity timing of hydrocarbon generation as well as migration pattern and the remaining hydrocarbon potential of the early cretaceous source rocks burial and thermal histories were constructed for four production wells and one pseudo well in addition two cross sections covering the depression and the structural highs around the trough were investigated by 2d basin modeling to provide a better regional overview on basin evolution the modeling results indicate that whereas the cretaceous source rocks are immature or early mature at the location of oilfields they reached sufficient maturity to generate and expel considerable amounts of hydrocarbons in the binak depression the main phase of oil generation and expulsion from the cretaceous source rocks is relatively recent and thus highly favorable for the conservation of hydrocarbon accumulations trap charging occurred through the late miocene to pliocene after the zagros folding 2d models predict that the albian source rock still has significant hydrocarbon generation potential whereas the lower neocomian source rock has reached already a high transformation ratio within the deep kitchen area oil migration occurs in both lateral and vertical directions this migration pattern could explain the distribution of identified oil families in the northwestern part of the persian gulf

environmental changes during the holocene climatic optimum in central europe human impact and natural causes abstract the priority programme changes of the geo biosphere aimed to reconstruct the environmental history of central europe with emphasis on the time interval from 9000 to 5500 cal bp time slice ii coinciding with the holocene climatic optimum during this period the onset of human activities such as settlement agriculture and animal husbandry caused environmental changes studies of different landscape units in germany were carried out to identify these anthropogenically induced changes and to distinguish them from natural effects on the environmental system the investigated archives included laminated lake sediments fluvial sediments colluvia and soils speleothems peat and coastal sediments the different archives were examined using refined research methods including a variety of sedimentary and geochemical analyses together with pollen analysis and dating methods for the establishment of a reliable chronology the results of the various research groups are summarised and critically discussed based on these results the climatic optimum can be subdivided into three periods 1 the early atlantic from 9000 to 7500 cal bp with negligible human impact and stable environmental conditions 2 the late atlantic during early and middle neolithic from 7500 to 6300 cal bp with pollen evidence for vegetation changes but only negligible changes detectable in other proxy records and 3 the late atlantic during the younger neolithic jungneolithikum after 6300 cal bp with human impact observed in many archives and proxy records especially in the pollen record but also in lacustrine and fluvial sediments during the whole climatic optimum natural causes such as minor shifts of temperature did not induce substantial environmental changes though some changes such as temporary droughts may have facilitated and amplified the observed human impact

shear deformation of dry polycrystalline olivine under deep upper mantle conditions using a rotational drickamer apparatus rda abstract shear deformation experiments on dry hot pressed polycrystalline san carlos olivine have been conducted at 4 9 9 6 gpa 1300 1870 k and strain rates of 0 6 7 4 10 5 s 1 using a rotational drickamer apparatus rda at a synchrotron facility the stress was measured from the orientational dependence of lattice spacing for the 1 3 0 1 3 1 1 1 2 1 2 2 1 4 0 and 2 4 1 planes as well as from the dislocation densities based on the mechanical and microstructural observations we infer that deformation occurs by power law creep involving dislocation glide and climb under high temperature conditions whereas deformation is due to exponential creep through the peierls mechanism at relatively low temperatures in both regimes the strength of olivine at steady state deformation at these pressures is much larger than those at lower pressures the activation volumes v is estimated to be 15 20 10 6 m 3 mol for the power law creep combined with the previous results under wet conditions we present the recommended values of flow law parameters on olivine for power law creep constrained by high pressure deformation experiments

petrophysical characterization of low permeable carbonaceous rocks comparison of different experimental methods abstract pore structure and gas transport properties of fourteen samples from the jurassic sargelu and the cretaceous garau formations in lurestan province southwest iran were studied under the aspect of shale gas exploration and production porosity was determined by helium pycnometry and water saturation archimedes principle low pressure adsorption of n2 was used to determine total pore volumes specific surface areas and microporosity high pressure mercury intrusion porosimetry mip was applied to assess pore size distributions permeability measurements were performed with helium and methane at confining pressures of 40 to 10 mpa using steady state and non steady state methods permeability and porosity values determined by the different methods are in a good agreement for low permeable samples less than 1 microdarcy 10 18 m2 the constant downstream pressure technique is the most efficient method for slip flow evaluation klinkenberg plot yielding apparent permeability coefficients over a wide range of reciprocal mean pressures 1 pmean in one single run a positive correlation was found between toc content porosity and permeability coefficients samples displaying clear signs of recrystallization tend to exhibit higher permeability none of the parameters determined in this study however showed a correlation with mineralogy the relationship between klinkenberg corrected permeability coefficients and confining pressure could be expressed by an exponential decay function stress sensitivity was typically higher for low permeable samples samples containing highly recrystallized carbonates exhibited lower stress sensitivity indicating an increase in rigidity due to recrystallization no correlation was found between methane helium permeability ratios sorption capacity and toc contents thus gas transport properties of this sample set were not affected by sorption and or swelling of organic matter

variations in the sterane carbon number distributions of marine source rock derived crude oils through geological time abstract the analysis of the sterane data of a large set of crude oils 414 derivedfrom marine carbonate 27 and siliciclastic source rocks 14 where influences of terrestrial or lacustrine derived organic matter can reasonably be excluded shows that there are increases in the relative content of c28 steranes and decreases in the relative content of c29 steranes through geological time there are no consistent variations in the relative content of c27 steranes through time with one major exception a proterozoic oil from oman palaeozolic and older crude oils are thus generally characterised by strong predominances of c29 steranes and low relative concentrations of c28 steranes significantly higher proportions of c28 steranes and lower proportions of c29 steranes occur in oils derived from jurassic and upper cretaceous source rocks these changes through time do not appear to reflect the chemical evolution of the sterols of one particular variety of marine organism the increase in c28 steranes may be related to the increased diversification of phytoplantonic assemblages in the jurassic and cretaceous possible sources of the c28 sterols necessary for the observed changes in crude oil steranes includes diatoms coccolithophores and dinoflagellates although the technique does not give an accurate means of determining the age of the source rock of a crude oil it is possible to distinguish younger crudes derived from the upper cretaceous and tertiary from palaeozoic and older crudes

the preboreal climate reversal and a subsequent solar forced climate shift accurate chronologies are essential for linking palaeoclimate archives carbon 14 wiggle match dating was used to produce an accurate chronology for part of an early holocene peat sequence from the borchert the netherlands following the younger dryas preboreal transition two climatic shifts could be inferred around 11 400 cal yr bp the expansion of birch betula forest was interrupted by a dry continental phase with dominantly open grassland vegetation coeval with the pbo preboreal oscillation as observed in the grip ice core at 11 250 cal yr bp a sudden shift to a humid climate occurred this second change appears to be contemporaneous with i a sharp increase of atmospheric c 14 ii a temporary decline of atmospheric co2 and iii an increase in the grip be 10 flux the close correspondence with excursions of cosmogenic nuclides points to a decline in solar activity which may have forced the changes in climate and vegetation at around 11 250 cal yr bp copyright c 2004 john wiley sons ltd

the holocene palaeoenvironmental changes reflected in the multi proxy studies of lake slone sediments se poland abstract multi proxy data from the lake slone sediments se poland yielded information on the holocene changes of lake slone in a karst region changes of limnological conditions and vegetation reconstructions correspond to high resolution multi proxy records from north central europe ostracods showed several small oscillations most significant changes occurred at 12300 cal yr bp younger dryas preboreal transition and between 11800 and 11100 cal yr bp preboreal oscillation lowering of the water table at around 11100 10800 cal yr bp was probably connected with abrupt warming at ca 11000 cal bp temperature and water depth fell at about 8400 8100 cal yr bp 8200 cal yr bp the atlantic period was generally warm and is divided into two parts an older one with comparatively stable water level and a second one between 7000 and 6300 cal yr bp with two phases of higher water level separated by lowering at 6800 cal yr bp at the transition from the atlantic to the subboreal 6200 5950 cal yr bp the dry period is more pronounced than changes in the second half of the atlantic since the beginning of the subboreal an increase in human activity in central europe was the main factor shaping the landscape and changing the limnic regimes

pollen based quantitative reconstructions of holocene climate variability in nw romania abstract a modern analogue technique is applied to two high resolution pollen sequences from nw romania to provide the first quantitative evidence for winter summer and annual temperatures and for precipitation across the holocene in this region the pollen based climate reconstructions allow the identification of four main intervals i an early less stable period between 11 700 and 11 200 cal yr bp ii generally stable conditions between 11 200 and 8300 cal yr bp with winter and annual temperatures and precipitation higher than at present and summer temperatures about the same iii lower winter and annual temperatures and higher summer temperatures and precipitation between 8000 and 2400 cal yr bp iv warmer winter and annual temperatures and lower precipitation for the last 2400 years whereas summer temperatures became cooler at steregoiu and remained stable at preluca tiganului the pollen based climate reconstructions at the two sites show similar patterns in annual and winter temperatures and precipitation changes during the holocene but the trends appear to be less consistent for summer temperatures our pollen based reconstructions revealed several short term climatic oscillations during the holocene the strongest of which occur between 10 300 10 100 8300 8000 6800 6400 5100 4900 4000 3600 and 3200 3000 cal yr bp

holocene climatic events linked to environmental changes at lake komořany basin czech republic former lake komo any located in northwest bohemia in central europe provides multiple proxies pollen plant macrofossils diatoms chironomids and sediment chemistry that allowed reconstruction of the development of its aquatic environment and catchment throughout the holocene in order to reconstruct the climatic forcing of this development we performed a pollen based reconstruction of climate changes using the best modern analogue method the climate reconstruction was successful for the interval of 10 0 3 2 ka bp we demonstrate that shifts in climate were coupled with biotic changes within the lacustrine environment both processes were interconnected mainly through changes in the water level status of the lake the most significant climatic and environmental changes were recorded at 9 1 6 3 4 8 4 7 3 8 and 3 5 ka bp

changes to the environment of intramontane basins in the light of malacological research of calcareous tufa podhale basin carpathians southern poland the profiles of calcareous tufa occurring in the podhale basin carpathians southern poland were subject to a detailed malacological analysis studies were carried out in 15 sites five of them represent the period of the late glacial and holocene and the remainder is tufa deposited during historical times on the basis of malacological analysis 10 faunistic assemblages were defined each developed under specific environmental and climatic conditions the observed sequences of molluscan assemblages in vertical profiles were the basis for paleoenvironmental reconstruction determining the main phases of climatic changes and the human impact on the natural environment the faunal sequence observed indicates a cold climate and the predominance of open habitats in the late glacial with progressing warming and the increasing significance of shaded habitats in the early and middle holocene as well as anthropogenic pressure in modern times the results of malacological analysis were complemented with determination of the age of deposits by radiocarbon dating and the results of palynological analyses conducted in the sites of peatbogs occurring in podhale the reconstruction indicates similarities and differences in the paleogeographic development of mountain and upland areas of central europe

first principles investigations on the elasticity and phase stability of grossular garnet 1 in order to understand the fate of subducted continental materials by means of mechanisms such as tectonic erosion and sediment subduction it is important to understand the high pressure stability and elastic properties of grossular garnet we study these questions using the first principles computation method grossular garnet was found to dissociate into an assemblage of casio3 ca perovskite pv and al2o3 corundum cor at about 23 4 gpa accompanied by remarkable jumps of compressional wave 8 0 shear wave 11 6 bulk sound 5 7 velocities and density 12 1 although pv with the grossular garnet composition was suggested experimentally after the decomposition reaction this phase was found to be less stable than an assemblage of capv and cor at pressures higher than 20 gpa this indicates that observed pv with the grossular garnet composition is metastable but can be obtained because of the slow kinetics of the garnet decomposition reaction our results imply that the dissociation of grossular garnet as well as that of jadeite included in continental materials subducted into the deep mantle increases the complexity of the 660 km discontinuity and can explain seismically observed multiple reflections we have also investigated the anisotropy of elastic velocities of grossular garnet capv and cor and found that capv is the most anisotropic mineral this implies that capv could produce seismic anisotropy in the uppermost lower mantle

a mid european decadal isotope climate record from 15 500 to 5000 years b p oxygen isotope ratios of precipitation delta18op inferred from deep lake ostracods from the ammersee southern germany provide a climate record with decadal resolution the record in detail shows many of the rapid climate shifts seen in central greenland ice cores between 15 000 and 5000 years before the present b p negative excursions in the estimated delta18op from both of these records likely reflect short weakenings of the thermohaline circulation caused by episodic discharges of continental freshwater into the north atlantic deviating millennial scale trends however indicate that climate gradients between europe and greenland changed systematically reflecting a gradual rearrangement of north atlantic circulation during deglaciation

regional stratigraphy of the zagros fold thrust belt of iran and its proforeland evolution the latest neoproterozoic through phanerozoic stratigraphy of the zagros fold thrust belt of iran has been revised in the light of recent investigations the revised stratigraphy consists of four groups of rocks each composed of a number of unconformity bounded megasequences representing various tectonosedimentary settings in the lowest group ranging in age from latest precambrian to devonian the uppermost neoproterozoic to middle cambrian rocks constitute a megasequence of evaporites siliciclastic deposits and interlayered carbonates which were deposited in pull apart basins that developed by the najd strike slip fault system this megasequence is overlain by a second one middle to late cambrian in age which consists of shallow marine siliciclastic and carbonate rocks representing deposition in an epicontinental platform the overlying shales siltstones and partly volcanogenic sandstones of ordovician silurian and devonian age are local remnants of stratigraphic units that were extensively eroded during development of several major unconformities the second group consists of two megasequences one permian and the other triassic composed of widespread transgressive basal siliciclastic rocks and overlying evaporitic carbonates of an equatorial epi pangean very shallow platformal sea the third group is composed of four megasequences formed of shallow and deep water carbonates with some siliciclastic and evaporite deposits which accumulated on a neo tethyan continental shelf during earliest jurassic through late turonian time the fourth group comprises siliciclastic and carbonate deposits of a largely underfilled nw to se trending forward and backward migrating late cretaceous to recent proforeland basin which has evolved as an integral part of the zagros orogen this last group consists of three megasequences ix x and xi with distinctive lateral and vertical facies variations which reflect specific tectonic events megasequence ix comprises uppermost turonian to middle maastrichtian prograding and retrograding siliciclastic and carbonate deposits whose accumulations reflect emplacement obduction of ophiolite slivers and subsequent collisional events in the zagros orogen megasequence x consists of uppermost maastrichtian to upper eocene siliciclastic and carbonate rocks which deposited first progradationally in front of the zagros orogenic wedge with reduced contractional tectonic activity and then retrogradationally due to intensified thrust stacking in the interior parts of the orogen megasequence xi consists of oligocene and lower miocene carbonate strata deposited retrogradationally shortly after a period of intensified late eocene thrust faulting in the deformational wedge and an overlying succession of upward coarsening northeasterly derived siliciclastic deposits of lower miocene to recent age which are composed of erosional byproducts of the southwest vergent zagros thrust sheets

the bituminous mixtures of tall e abu chizan a vth millennium bc settlement in southwestern iran abstract various bituminous artifacts were excavated from the tall e abu chizan a late prehistoric middle susiana to middle uruk settlement on the middle of the curvy plain between the karun river and the ram hormoz plain all samples dated from the vth millennium bc and cover three periods 5000 4700 bc late middle susiana 4700 4200 bc late susiana 1 and 4200 3900 bc late susiana 2 the bitumens were studied using the techniques of petroleum geochemistry and were compared both to the unaltered crude oils produced from the main oil fields in the area and to the famous mamatain oil seeps all samples are very rich in bitumen average 46 wt which has been biodegraded and oxidized despite these alteration phenomena 13 c of asphaltenes occur within a narrow range of less than 1 pdb biodegradation affected the steranes terpanes dibenzothiophenes and mono and triaromatic steroids molecular characteristics of terpanes especially the occurrence of 18 h oleanane suggest that the bitumen from tall e abu chizan is a mixture generated from cretaceous kazdhumi and eocene pabdeh petroleum source rocks in that respect bitumens from tall e abu chizan belong to the same oil family as oil from the naft safid field which is in the vicinity of the archaeological site in fact the bitumen at tall e abu chizan likely originated from oil seepages at naft safid these oil seeps have not yet been sampled or analysed

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

source rock distribution and maturation in the zagros orogenic belt provenance of the asmari and bangestan reservoir oil accumulations abstract the zagros orogenic belt of iran is one of the most prolific petroliferous areas accounting for approx 12 of proven global reserves correlation techniques reveal that a majority of the oils variously reservoired in asmari oligo miocene and bangestan group upper cretaceous anticlinal structures share a common provenance oils of the n e khuzestan fields are an exception showing a conspicuously different origin candidate source potential for the crucial central zagros embayment and contiguous areas was assessed on field survey and from well materials collected during the decade from 1968 onwards although varying locally in vertical and lateral distribution attractive sources occur throughout the section included were silurian shales the sargelu middle jurassic garau gadvan lower cretaceous kazhdumi albian gurpi upper cretaceous and pabdeh paleogene fms maturation of these source units was essentially controlled by the foredeep subsidence related to the zagros orogeny being a neogene event hydrocarbon generation and migration are very recent and essentially synorogenic consolidation of this information with the real distribution of candidate sources application of carbon isotope based source oil assignments and biomarker results successfully differentiated the provenance of the generic oil groupings over much of khuzestan the kazhdumi was recognised as the major contributor elsewhere the pabdeh fm yields isotopically distinctive oils in n e khuzestan evaluation of this basin allowed identification of prolific source rocks in low energy euxinic argillaceous lime mudstones similarly it provided an early application of pyrolysis techniques carbon isotopic correlations and subsidence history maturation migration modelling approaches now routinely employed in basin evaluation

were abrupt lateglacial and early holocene climatic changes in northwest europe linked to freshwater outbursts to the north atlantic and arctic oceans during the lateglacial and early holocene abrupt millennial scale climatic variations are recorded in a wide range of high resolution proxy records from marine and terrestrial archives in nw europe our review of the evidence for these rapid climate events do not show an apparent link to possible forcing factors such as long term orbitally induced variations in solar radiation short term variations in solar activity as inferred from 14 c atmospheric carbon dioxide concentration or volcanic sulphate as recorded in the gisp2 ice core record there is however a remarkable degree of similarity with the number duration and timing of episodes of increased e ux of fresh water to the north atlantic and arctic oceans from the laurentide ice sheet and from the baltic ice lake in sw sweden these freshwater outburst events occurred when continental runoff from the laurentide ice sheet was rerouted from the mississippi river to the hudson river st lawrence river hudson strait and along the mackenzie river to the atlantic and arctic oceans and when the baltic ice lake in sw sweden drained to skagerrak periods of increased freshwater e ow to the north atlantic and arctic oceans may thus provide a mechanism to explain the abrupt and signie cant lateglacial and early holocene climate events in nw europe the idea that freshwater outbursts might drive abrupt climate events is not new but previous work may have underestimated the extent of support from proxy data and overestimated the ine uence of the laurentide ice sheet

subduction versus accretion of intra oceanic volcanic arcs insight from thermo mechanical analogue experiments we perform thermo mechanical laboratory experiments designed to explore the behaviour of the volcanic arc during intra oceanic arc continent collision following oceanic subduction and subsequent back arc opening the overriding oceanic lithosphere is made of two layers representing the oceanic crust and the lithospheric mantle this lithosphere carries a volcanic arc and is thinned and weakened beneath both the arc and the back arc basin the subducting plate contains three parts one layer oceanic and two layer crust and mantle continental lithosphere with a continental margin between them when the continental margin reaches the trench and starts subducting the overriding plate undergoes growing horizontal compression and finally fails in the vicinity of the back arc spreading centre which is the weakest part of this plate the failure can result in subduction of the whole arc plate comprised between the trench and the back arc spreading centre during subduction of the arc plate the mantle part of this plate subducts completely while the behaviour of the arc crust depends on its thickness and strength which is a function of composition and temperature we tested four cases with different arc crust thicknesses and composition rheology with total lithosphere thickness in the arc being constant three types of tectonic evolution have been obtained complete arc subduction complete arc accretion and partial arc subduction accretion the result is largely controlled by the crustal thickness of the arc a thin arc thickness equivalent to v16 km in nature made of the same strong material as the oceanic crust subducts completely without leaving any trace at the surface on the contrary a thick arc equivalent to v26 km in nature made of the same material is scraped off and accreted to the overriding plate the lower crust of such an arc is hotter therefore its strength at moho depth and coupling between crust and mantle are small in addition the thick arc has a high isostatic relief and hence a greater mechanical resistance to subduction therefore the arc is scraped off if the arc is made of a weaker continental like material or contains a weak layer low friction interface it is completely or partially scraped off even if it is small when there is no back arc opening before collision no thin and weak lithosphere in the rear of the arc the overriding plate fails in the arc area which may result in a complete fore arc block subduction with the volcanic arc remaining at the surface the obtained models are compared with mountain belts with nearly no trace of arc activity oman with accreted arc kohistan and with small remnants of subducted arc southern tibet 2003 elsevier science b v all rights reserved

mire development pathways and palaeoclimatic records from a full holocene peat archive at walton moss cumbria england plant macrofossil data have been used to identify the successive mire communities occupying both central and marginal locations in the walton moss peatland complex during the last 10 500 years the reconstructed pathways of mire development indicate that early holocene fen and fen carr communities were succeeded by species indicative of deep mire water tables and oligotrophic conditions the character of the fen bog transition fbt is compared with similar records of peatland development from britain and scandinavia and with independent climate data for the early holocene the pseudohochmoor of central europe is suggested as an approximate modern analogue for the dry pioneer oligotrophic mire type and alternative explanations for its presence are explored the first major increase in ombrotrophic sphagna occurred at c 7800 cal bp overlying sphagnum peats provide a continuous record of climate change inferred from fluctuations in raised mire surface wetness the proxy palaeoclimate record reconstr

instabilities from phase transitions and the timescales of mantle thermal evolution we have investigated the effects of mantle phase transitions on the earth s thermal evolution by numerical modelling our results show that the tendency of layering grows with increasing vigor of convection a self consistent model which couples the convective dynamics of the mantle to the secular cooling of the core is constructed for a temperature dependent effective viscosity we found that the thermal history of the earth is characterized by two timescales one is associated with layered convection in the early period which is followed by a transition period with dramatic overturns as the rayleigh number decreases sufficiently low whole mantle convection prevails and a faster cooling timescale ensues

continental crust crustal underplating and low q upper mantle beneath an oceanic island arc a detailed structural model of the crust subducting slab and underlying upper mantle across the northern izu ogasawara bonin island arc system is derived from a marine seismic reflection and ocean bottom seismographic refraction survey and subsequent forward modeling combined with tomographic inversion the model indicates that the crust is thickest beneath the presently active rift zone and a granitic crust may have formed in the mid crust a highly attenuative mantle that is one with low quality q seems to be confined mainly beneath the presently active rift zone in contrast high p wave velocity persists in the lower crust between the forearc and eastern margin of the back arc basin suggesting a large scale magma input responsible for the arc formation

atmospheric circulation upwelling and organic rich rocks in the mesozoic and cenozoic eras abstract by using the basic principles of atmospheric circulation and analogies from present circulation patterns it is possible to construct qualitative atmospheric circulation models on paleogeographic maps the wind patterns predicted by these models then serve as the basis for predicting the locations of ancient upwelling zones atmospheric circulation and upwelling models for seven geologic stages in the mesozoic and cenozoic were constructed and the distribution of the upwelling zones compared with the distribution of organic rich rocks for all time periods together the correlation was statistically significant when the individual time periods were analyzed separately the following pattern emerged significant correspondence between upwelling zones and organic rich rocks in the triassic middle early cretaceous to late cretaceous and middle paleogene to neogene no significant correspondence was found for the intervening times upwelling does not account for all organic rich rocks so called anoxic oceanic events and transgressions play an important role in their deposition it is suggested that upwelling contributes significantly to the pattern of organic rich rock distribution and is important in determining organic facies

contrasting patterns of hydrological changes in europe in response to holocene climate cooling phases the quantitative reconstruction of climatic parameters from pollen and lake level data obtained at saint jorioz lake annecy eastern france gives evidence for cooler and wetter conditions during the 8 2 ka cold event a comparison of these regional data with other hydrological records reconstructed in europe for the same period suggests as a working hypothesis that mid latitudes between ca 50 and 43 underwent wetter conditions in response to the cooling whereas northern and southern europe were marked by drier climate in the latter case leading to an interruption of the sapropel 1 formation in the mediterranean a similar hydrological tri partition of europe can be observed during other holocene cooling phases associated with north atlantic ird events data indicate that the middle zone characterised by wetter climate conditions could have had a more extended latitudinal amplitude during phases of climate cooling weaker than the 8 2 ka event the differences in expansion of the wet mid european zone depending on holocene climate cooling phases could reflect variations in the strength of the atlantic westerly jet in relation with the thermal gradient between high and low latitudes

4 1 5 c abrupt warming 11 270 yr ago identified from trapped air in greenland ice nitrogen and argon isotopes in air trapped in a greenland ice core gisp2 show two prominent peaks in the interval 11 800 10 800 b p which indicate two large abrupt warming events the first abrupt warming 10 4 c is the widely documented event at the end of the younger dryas here we report on the second abrupt warming 4 1 5 c which occurred at the end of a short lived cooler interval known as the preboreal oscillation 11 270 30 b p a rapid snow accumulation increase suggests that the climatic transition may have occurred within a few years the character of the preboreal oscillation and the subsequent abrupt warming is similar to the dansgaard oeschger d o events in the last glacial period suggestive of a common mechanism but different from another large climate change at 8 200 b p in which cooling was abrupt but subsequent warming was gradual the large abrupt warming at 11 270 b p may be considered to be the final d o event prior to the arrival of the present stable and warm epoch

oleanane or lupane reappraisal of the presence of oleanane in cretaceous tertiary oils and sediments nonpolar gc columns are normally used for gc ms analysis of saturate fractions from crude oils under these conditions lupane coelutes with oleananes and some minor c30 compounds of non terrigenous origin having lupane like mass spectra because any peak eluting fractionally earlier than 17 21 h hopane in the m z 191 mass chromatogram is routinely assigned to oleanane the presence of lupane may sometimes have been overlooked lupane and oleananes are easily separated using reverse phase hplc triterpane concentrates from 10 crude oils known to contain oleananes were hplc separated lupane was unambiguously identified in six of the oils by full scan gc ms analysis of fractions having the hplc retention time of authentic lupane gc separation of lupane and oleananes is possible using polar gc columns having a polyethylene glycol stationary phase organic geochemistry 23 1995 21 allowing estimation of the lupane lupane oleanane ratio high ratios were measured in the marraat oil west greenland 0 8 and the amauligak oil from the beaufort mackenzie delta 0 26 the results suggest that lupane may be more frequently occurring than previously thought and that this compound is preferably associated with high latitude samples high concentrations of 28 nor and 24 28 bisnortriterpanes oleananes lupanes and taraxastanes were detected in the marraat oil

izu bonin arc subduction under the honshu island japan evidence from geological and seismological aspect abstract the izu bonin intra oceanic arc with 20 35 km thick continental crust is being subducted under the honshu presumably since 17 ma tomographic image clearly demonstrates that the whole izu bonin arc is subducting under the honshu arc geologic cross section and the thickness of continental crust do not support the accretion of thick crust in spite of the continued subduction over 17 ma

correlation and synchronisation of lateglacial continental sequences in northern central europe based on annually laminated lacustrine sediments abstract the present study focusses on correlation and synchronisation of weichselian lateglacial varved lake sediments from western germany meerfelder maar eifel region northern germany hamelsee lower saxony central poland lake go ci a z and eastern poland lake perespilno by using varve chronology tephrochronology palynostratigraphy and stable isotopes comparison of the several independent time scales shows that biotic and abiotic parameters respond abruptly and quasi synchronously within the errors of the different chronologies during the younger dryas preboreal transition moreover there is a consensus about the length of the younger dryas cold stage of 1100 1150 varve years in the allerod the prominent laacher see tephra 12 880 varve years bp can be used to fix floating varve chronologies the relative duration of this biozone has been determined in meerfelder maar and hamelsee at between 625 and 670 varve years in the meerfelder maar a combination of continuous varve counting and biostratigraphy has been possible for the almost entire lateglacial the comparison between continental limnic sequences and greenland ice core records should be made on the basis of independent chronologies in both archives it is more practicable to develop regional stratotypes on the continental regions instead of simply using ice cores as stratotypes for the lateglacial for terrestrial european records in this respect annually laminated lacustrine sequences have a great potential

past hydrological events reflected in holocene history of polish rivers abstract a database of 335 radiocarbon dates from holocene fluvial sediments in poland has been compiled each sample is characterized by 25 parameters all samples were grouped into one of 7 regions characterized by hydrological regime and one of 8 depositional environments statistical analysis was used to enhance the palaeoenvironmental data and 17 phases may be distinguished 10 of which have a distinct sharp peak abandoned paleochannels 149 dates clearly reflect the major wetter phases of the holocene an opposite picture is presented by overbank aggradation 86 dates connected mainly with expansion of agriculture preliminary correlations are made on peat bog records changes in vegetation lake water level rates calcareous tufa and speleothems growth landslides phases and debris flow phases these show many convergences explained by climatic fluctuations during the holocene

holocene environmental changes in northern poland recorded in alkaline spring fed fen deposits a multi proxy approach abstract spring fed fen deposits peat tufa sequences from northern poland were investigated for holocene environmental reconstruction climate and hydrology using multi proxy analysis lithofacies molluscs pollen plant macrofossils geochemistry and stable oxygen and carbon isotopes the main aims of these studies were 1 comparison of several similar sites with the same type of groundwater supply and sedimentation on a widespread space scale 2 detailed reconstruction of their long term development assessing their sensitivity to climate change 3 verification of the synchronicity of the record of different proxies in distant sites in the context of holocene climate changes in relation to specific well known global and or regional climate events so called bond events and 4 discussion on permafrost degradation as a driver of spring fed fens development based on our palaeogeographical data we have distinguished an asynchronicity of the beginning of the development of spring fed fens in the eastern and western parts of the studied region that is associated with different times of ascending groundwater supply unblocking after complete permafrost degradation therein asynchronicity of permafrost degradation was brought about by multiple climatic geological and structural conditions our results also indicate significant differences in the trends of succession ecological and lithological caused by the geographical location of the studied sites asynchronicity of the occurrence of wet and dry phases as well as significant differences in their duration were noted this depended upon the influence of oceanic western part or continental climates eastern part warm and humid oceanic climate promoted the domination and longer duration of wet phases especially in the eo and early mesoholocene while the harsh continental climate promoted the more frequent occurrence of dry phases with short episodes of increased humidity from the middle mesoholocene this marked regional diversification becomes less pronounced results also allowed for the recognition of several palaeoclimatic events on a regional scale four main cold episodes bond events 8 5 during lg h transition 11 5 ky cal bp eo 10 25 ky cal bp 9 4 ky cal bp and at the beginning of the mesoholocene 8 2 ky cal bp are well documented by multiple proxies at all study sites other cold episodes bond events 4 0 are slightly less documented and are not clear for interpretation the results of our study demonstrate the importance of spring fed fen deposits for detailed palaeoenvironmental reconstruction on a regional scale

early holocene climatic oscillations recorded by lake level fluctuations in west central europe and in central italy abstract on the basis of lake level data the period of the preboreal oscillation pbo at 11 300 11 150 cal yr bp as defined by the grip oxygen isotope record appears to correspond to wetter climatic conditions in west central europe and to a marked drying in north central italy additional short lived phases of higher lake level have been identified before the pbo at ca 11 450 11 400 and 11 350 cal yr bp in west central europe and at ca 11 500 cal yr bp in italy such multiple climatic oscillations around the pbo have been observed in various records in northwestern europe on the basis of various proxies a map of changes in moisture over western europe during the pbo indicates a mid latitude zone between 58 and 43 n characterised by wetter conditions while a drier climate developed in southern and northern europe this wet middle zone shows a larger extension and suggests a more meandering weaker atlantic westerly jet during the pbo than during the 8 2 kyr event a comparison of lake level records in west central europe with 1 outbursts from north american and north european proglacial lakes and 2 variations in solar activity as reflected by 14 c and the 10 be records supports the hypothesis that the pbo was a response to successive meltwater pulses at 11 300 11 250 11 200 and 11 170 cal yr bp and to a sudden decrease in solar activity at 11 250 cal yr bp this study points to the necessity of developing integrated multi proxy approaches to construct more robust regional event stratigraphies and of better documenting palaeohydrological changes in the mediterranean area

lower silurian hot shales in north africa and arabia regional distribution and depositional model abstract lowermost silurian organic rich hot shales are the origin of 80 90 of palaeozoic sourced hydrocarbons in north africa and also played a major role in petroleum generation on the arabian peninsula in most cases the shales were deposited directly above upper ordovician peri glacial sandstones during the initial early silurian transgression that was a result of the melting of the late ordovician icecap deposition of the main organic rich shale unit in the north african arabian region was restricted to the earliest silurian rhuddanian stage acuminatus atavus and probably early cyphus graptolite biozones during this short period 1 2 m y a favourable combination of factors existed which led to the development of exceptionally strong oxygen deficiency in the area in most countries of the study area the post rhuddanian silurian shales are organically lean and have not contributed to petroleum generation the distribution and thickness of the basal silurian hot shales have been mapped in detail for the whole north african region using logs from some 300 exploration wells in libya tunisia algeria and morocco in addition all relevant accessible published and unpublished surface and subsurface data of the lower silurian shales in north africa and arabia have been reviewed including sedimentological biostratigraphic and organic geochemical data the lowermost silurian hot shales of northern gondwana are laterally discontinuous and their distribution and thickness were controlled by the early silurian palaeorelief which was shaped mainly by glacial processes of the late ordovician ice age and by pan african and infracambrian compressional and extensional tectonism the thickest and areally most extensive basal silurian organic rich shales in north africa occur in algeria tunisia and western libya while on the arabian peninsula they are most prolific in saudi arabia oman jordan and iraq the hot shales were not deposited in egypt which was a large palaeohigh at that time the depositional model presented may help in better understanding the source potential of the basal silurian shales in less explored regions of north africa and arabia including morocco northern niger and the kufra basin in southeast libya

the preboreal oscillation around the nordic seas terrestrial and lacustrine responses the occurrence of an early preboreal climatic cooling oscillation pbo in lacustrine and glacial records from northwest europe iceland and greenland is reviewed and documented the often subtle response of the proxy records to this oscillation in combination with its short duration make it difficult to detect owing to its chronostratigraphic position between the 10 000 9900 and 9600 9500 14 c plateaux c 11 300 11 150 calendar yr bp it is also difficult to 14 c date with precision we find that the vegetation response to the pbo varies between sites and regions in contrast to the pioneer vegetation in iceland and southern sweden the expanding birch pine forest in germany denmark was more susceptible to deteriorating growing conditions the combined lacustrine tree ring and glacial records imply that the pbo was characterised by cool and humid conditions throughout northwestern and central europe this is documented by vegetation changes decreased aquatic production increased soil erosion increased 2 h and 13 c content in tree rings readvances or stillstands of the ice sheet in norway and finland and ingression of brackish water into the baltic icelandic proxy records from lake sediments and glacial moraines imply cooler conditions than during the previous preboreal period but not as extreme as during the younger dryas greenland records suggest that the early preboreal was characterised by ice readvances as an effect of cool climate and increased precipitation in relation to the younger dryas it was not until the end of the pbo that climate was warm enough to melt the land based ice sheet this preboreal oscillation found on both sides of the nordic seas is interpreted as an effect of increased freshwater forcing on the thermohaline circulation in the nordic seas which is implied by a simultaneous and distinct rise in the atmospheric 14 c 12 c ratio a slow down of the thermohaline circulation may tempor arily have pushed the polar front further south 1997 by john wiley sons ltd preboreal oscillation thermohaline circulation lacustrine records glacial records chronology

tectonics versus eustatic control on supersequences of the zagros mountains of iran abstract at least 12 km of strata ranging in age from the latest precambrian to the recent are exposed in the zagros mountains of iran this sedimentary cover is characterized by distinct stratal packages separated by major unconformities forming twelve supersequences they are informally named as 1 late precambrian cambrian hakhamanesh supersequence 2 ordovician kourosh supersequence 3 silurian camboojiyeh supersequence 4 devonian darioush supersequence 5 mississippian pennsylvanian khashayar supersequence 6 permian triassic ashk supersequence 7 jurassic farhad supersequence 8 early cretaceous mehrdad supersequence 9 late cretaceous ardavan supersequence 10 paleocene oligocene sassan supersequence 11 oligocene miocene ardeshir supersequence and 12 miocene pleistocene shapour supersequence these supersequences and their correlatives in neighboring areas have been used to infer tectonic events the dominant interpretation has been that local or regional epeirogenic movements were responsible for the formation of these supersequences unconformities are considered as indications that epeirogenic movements associated with tectonic events affected the area the present investigation provides an alternative to the established view of the phanerozoic supersequences of the zagros mountains a good correlation exists between the lithofacies of supersequences in the zagros mountains and the second order eustatic sea level changes deposition of deep water marine shales occurred during periods of eustatic sea level rise platform wide unconformities coincided with eustatic sea level lows in fact supersequences of the zagros mountains are nearly identical to those described from the north american craton and the russian platform suggesting that these stratal packages are global these observations suggest that supersequences of the zagros mountains formed by second order eustatic sea level changes and not by local or regional epeirogenic movements although tectonic events did not produce supersequences of the zagros mountains they influenced regional lithofacies patterns through the formation of intrashelf depressions such as the hormoz salt basin during the precambrian and the dezful embayment and the lorestan basin during the mesozoic tectonic events also affected sedimentation during the tertiary collision of arabia and the central iran microplate through uplift erosion and the formation of the zagros foreland basin the results of this investigation necessitate a re evaluation of the role and the significance of pre tertiary tectonic events commonly used to interpret the geological evolution of the zagros mountains

subduction of continental crust and terrigenous and pelagic sediments an experimental study abstract an important role for the recycling of terrigenous sediments in the mantle was proposed by armstrong 1 2 aspects of this hypothesis have been tested via an experimental study of phase equilibria in a composition similar to that of average upper continental crust over the pressure interval 6 24 gpa this composition is sufficiently close to those of the principal argillaceous and siliceous classes of pelagic sediments to use the results to interpret the behaviour of these latter sediments in addition to terrigenous sediments during subduction the subsolidus phase relationships displayed by lithologies derived from these materials are complex with major roles being played by k hollandite garnet na clinopyroxene and stishovite continentally derived lithologies achieve densities similar to or greater than surrounding mantle at depths greater than 200 km the geodynamical implications of these buoyancy relationships are discussed a reconnaissance study has also been made to assess the melting and element partitioning behaviours in the subducted continental crust lithologies during partial melting at relatively low pressures 5 10 gpa orthoclase wadeite and k hollandite are eliminated near the solidus whereas the stability field of na clinopyroxene extends to temperatures well above the solidus liquids formed by small to moderate degrees of partial melting of subducted continentally derived lithologies in this pressure interval have high k na ratios and high sio2 contents at higher pressures 16 24 gpa the stability fields of k hollandite and stishovite extend towards the liquidus whereas sodium bearing phases are eliminated much closer to the solidus resultant partial melts consequently possess relatively low k na ratios and sio2 contents lead possesses a high crystal liquid partition coefficient in k hollandite whereas uranium is excluded the broad stability field of k hollandite during partial melting of these lithologies at pressures above 15 gpa therefore has the capacity to cause fractionation of lead from uranium the petrological and geochemical implications of these results are discussed in the context of the partial melting of terrigenous materials during subduction and the interactions of the partial melts with the surrounding mantle

regional and local changes inferred from lacustrine organic matter deposited between the late glacial and mid holocene in the skaliska basin north eastern poland abstract the article presents the results of a combination of isotopic 15 n and 13 c geochemical toc tn c n and palaeobotanical investigations they were carried out on organic matter om that had been deposited from the younger dryas to the subboreal chronozone in palaolake sediments north eastern poland om from the late younger dryas consists only a small amount of toc and tn which together with the lack of aquatic macrophyte macrofossils confirm low primary production in the then reservoir the higher values of c n ratio 18 27 and 13 c ca 26 suggest that om was mainly terrestrial in origin during the preboreal chronozone 11 450 10 150 cal bp there was a probable deepening of the reservoir through the melting of dead ice this might have been intensified by an increase in precipitation and a fall in evapotranspiration during the preboreal oscillation from the early preboreal chronozone ca 11 345 cal bp a mixed source of om is indicated by c n ratio from 8 to 13 at the same time significant increase in toc and tn probably registered a rise in primary production in the palaeolake from the older part of the boreal chronozone ca 9865 cal bp algae productivity increased the c n ratio dropped to ca 8 and was then constant at the beginning of the atlantic chronozone ca 8650 cal bp a probable increase in the water level caused the partial relocation of om from the reed swamp belt and or the adjacent alder carr into deeper sections of the palaeolake an increase in toc and tn in the late atlantic chronozone ca 6965 6650 cal bp toc and tn decreased while 13 c had high values which probably reflected a more distinct stratification of the water column with anoxic bottom waters next in the late atlantic and early subboreal chronozone ca 6650 5205 cal bp the amount of om in palaeolake sediments was still rising the 13 c values dropped suggesting an intensification of processes of water mixing these processes were simultaneous with the constant shallowing of the palaeolake and the disappearance of habitats suitable for submerged macrophytes the topmost part of the profile is characteristic of a strong decomposition of peat causing a release of carbon dioxide and therefore the depletion of the carbon pool in the peat a drop in the c n ratio the concurrent upward trend of the 15 n curve is probably the effect of a greater anthropogenic impact on the palaeolake mire and its catchment and or more recent human interference in the topmost peat layers

petrological model of the northern izu bonin mariana arc crust constraints from high pressure measurements of elastic wave velocities of the tanzawa plutonic rocks central japan abstract ultrasonic compressional wave velocities vp and shear wave velocities vs were measured with varying pressure up to 1 0 gpa in a temperature range from 25 to 400 c for a suite of tonalitic gabbroic rocks of the miocene tanzawa plutonic complex central japan which has been interpreted as uplifted and exposed deep crust of the northern izu bonin mariana ibm arc the vp values of the tonalitic gabbroic rocks increase rapidly at low pressures from 0 1 to 0 4 gpa and then become nearly constant at higher pressures above 0 4 gpa the vp values at 1 0 gpa and 25 c are 6 3 6 6 km s for tonalites 56 4 71 1 wt sio2 6 8 km s for a quartz gabbro 53 8 wt sio2 and 7 1 7 3 km s for a hornblende gabbro 43 2 47 7 wt sio2 combining the present data with the p wave velocity profile of the northern ibm arc we infer that 6 km thick tonalitic crust exists at mid crustal depth 6 1 6 3 km s vp overlying 2 km thick hornblende gabbroic crust 6 8 km s vp our model shows large differences in acoustic impedance between the tonalite and hornblende gabbro layers being consistent with the strong reflector observed at 12 km depth in the ibm arc the measured vp of tanzawa hornblende bearing gabbroic rocks 7 1 7 3 km s is significantly lower than that vp modeled for the lowermost crustal layer of the northern ibm arc 7 3 7 7 km s at 15 22 km depth we propose that the ibm arc consists of a thick tonalitic middle crust and a mafic lower crust

transportation of h2o beneath the japan arcs and its implications for global water circulation abstract in order to understand the transportation and circulation of h2o in subduction zones geological and seismological observations and the corresponding quantitative modeling are reviewed and consolidated with a special emphasis on the japan arcs the japan arcs are ideal for such a study in that 1 they are very active magmatically and seismically with abundant high quality observations and 2 subduction parameters change significantly along the japan arcs allowing one to investigate how the variations of input parameters affect the resultant structures and processes first numerical models for the transportation of h2o and melting are introduced the generation and migration of aqueous fluid its interaction with the convecting solid and melting are considered based on the realistic phase relationships of the peridotitic and basaltic systems application of the models to the japan arcs and comparison between the model results and the observations distribution of volcanoes and seismic structures along the japan arcs are then discussed the three cases from the ne central and sw japan arcs clarify the following points first an aqueous fluid released from the subducting oceanic crust forms a serpentinite layer in the mantle wedge just above the subducting slab maintaining a condition close to equilibrium in terms of hydration dehydration reactions during aqueous fluid migration second most of the h2o is subducted to a depth where serpentine and chlorite in the serpentinite layer break down this depth depends on the thermal structure of the slab and is greater for the older plate beneath the japan arcs as a consequence aqueous fluid and melt are in general not supplied straight upward to the volcanic front this result is rather different from the conventional view finally based on the understanding obtained from the japan arcs the global budget and circulation of h2o are discussed even after the completion of dehydration of major hydrous mineral phases in the subducting materials especially at the base of the mantle wedge just above the subducting slab nominally anhydrous phases of the upper mantle assemblage i e olivine pyroxenes garnet can carry a significant amount of h2o 1 1 1011 to 7 8 1011 kg yr 1 into the deep mantle the minimum estimate is comparable to the outflow of h2o from the mantle at mid ocean ridges and hotspots while the maximum estimate greatly exceeds it the large estimated range is mainly due to the uncertainty of the maximum h2o contents in the nominally anhydrous minerals of the upper mantle which controls the net influx of h2o into the deep mantle through subduction zones water subduction magmatism global circulation

july mean temperature and annual precipitation trends during the holocene in the fennoscandian tree line area pollen based climate reconstructions july mean temperature and annual precipipation during the last 9900 cal yr bp were recon structed from pollen assemblages preserved in a sediment core from northern finland quantitative recon structions were performed using a modern pollen climate calibration model based on weighted averaging partial least squares regression the predictive ability of the model was evaluated against modern meteoro logical data using leave one out cross validation the prediction error for july mean temperature is c 1 0 c and for annual precipitation 340 mm the july mean temperatures during the earliest holocene were low c 1 1 0 c and annual precipitation was high c 600 800 mm between 8200 and 6700 cal yr bp july mean temperatures reached their maxima 12 5 13 0 c which are c 1 4 1 7 c higher than at present at the same time precipitation decreased during the late holocene july mean temperatures declined and the last 2000 years have been the coolest since the early holocene precipitation has slightly increased the spatial coherence between our results and of several other climate reconstructions from northern europe indicates that the holocene climate was strongly influenced by north atlantic oceanic and atmospheric circulation patterns we propose that the distinctly oceanic climate of the early holocene was due to enhanced westerly latitudinal airflow which was replaced at c 8200 cal yr bp by a more meridional flow pattern and by the development of predominantly anticyclonic summer conditions

vegetation responses to the 8200 cal bp cold event and to long term climatic changes in the eastern alps possible influence of solar activity and north atlantic freshwater pulses subfossil pollen from two bogs in temperature sensitive high altitude regions were analysed in order to reconstruct early to mid holocene summer temperature fluctuations in the eastern alps the p

a chironomid based holocene summer air temperature reconstruction from the swiss alps we developed a quantitative chironomid july air temperature inference model based on surface sediments from 81 swiss lakes and applied it to the holocene subfossil chironomid record of hinterburgsee a small subalpine lake in the northern swiss alps present day mean july air temperature of 11 3 c after smoothing to reduce the high between sample variability of inferred temperatures the reconstruction indicates july air temperatures of 10 4 10 9 c at the end of the younger dryas of 11 9 12 8 c during the early and mid holocene 11500 4000 cal bp and slightly lower temperatures of 11 5 12 0 c during the late holocene 3500 1000 cal bp a warming trend inferred for the past millennium is most likely an artifact of human impact on hinterburgsee s chironomid fauna rather than a genuine temperature signal the most prominent climatological events during the holocene were two periods of lower temperatures at c 10700 10500 cal bp and 8200 7700 cal bp and an abrupt shift to a cooler late holocene cl

hydrocarbon habitat in main producing areas saudi arabia current hydrocarbon production in saudi arabia is from reservoirs of cretaceous and jurassic age geochemical studies of the sediments and oils suggest that the hydrocarbons were derived from two separate source rock provinces oil production from the large fields in the southern part of the area is from jurassic carbonate reservoirs most of these oils were derived from thermally mature thinly laminated organic rich carbonate rocks of jurassic age callovian oxfordian these source rocks were deposited in an intrashelf basin which is limited to the southern part of the main producing areas extensive vertical migration of oils originating in these sediments is prevented by superjacent evaporite seals deposited during the late jurassic fields in the northern producing areas appear to have derived their hydrocarbons from a source rock province on the north production from cretaceous clastic and carbonate reservoirs is limited to the northeastern part of the producing areas this distribution may be explained by limitation of thermally mature cretaceous source rocks to the northeastern areas or by the local lack of subjacent evaporite seals to separate these reservoirs from jurassic source rocks thermal maturation studies indicate that the hydrocarbons in mesozoic reservoirs migrated into the present traps during the early tertiary

supply rate of continental materials to the deep mantle through subduction channels abstract geological studies have revealed that continental materials subduct from the earth s surface via the following three mechanisms tectonic erosion sediment subduction and direct subduction of immature oceanic arcs then the continental materials are transported through subduction channels that are located between subducting slabs and mantle wedges however the depth that a subduction channel reaches and the magnitude of the flux of subducted materials at that depth are not clear here in order to estimate the supply rate of continental materials to the deep mantle we have conducted a numerical simulation of a subduction channel based on the finite difference method we have found that a sustainable thickness of the channel in the deep mantle is 2 3 km and its corresponding flux of continental materials integrated over the length of the current subduction zones is 2 2 km3 yr these results indicate that almost all of the continental material that is subducted through the channel is capable of reaching the depth of the mantle transition zone the total amount of continental materials conveyed to the deep mantle over 4 gyr is estimated to be about 1010 km3 which is greater than the volume of the present continental crust at the surface of the earth

neogene sediments and modern depositional environments of the zagros foreland basin system a sedimentological investigation of the neogene deposits of the zagros foreland basin in sw iran reveals a continuous and largely gradational passage from supratidal and sabkha sediments at the base represented by the gachsaran formation to carbonates and marine marls mishan formation with basal guri carbonate member followed by coastal plain and meandering river deposits agha jari formation and finally to braided river gravel sheets bakhtyari formation this vertical succession is interpreted to represent the southward migration of foreland basin depozones from distal foredeep and foredeep to distal wedge top and proximal wedge top respectively as the zagros fold thrust belt migrated progressively southward towards the arabian foreland this vertical succession bears a striking similarity to modern depositional environments and sedimentary deposits observed in the zagros region today where one passes from mainly braided rivers in the zagros mountains to meandering rivers close to the coast to shallow marine clastic sediments along the northern part of the persian gulf and finally to carbonate ramp and sabkha deposits along the southeastern coast of the persian gulf this link between the neogene succession and the modern day depositional environments strongly suggests that the major neogene formations of the zagros foreland basin are strongly diachronous as shown recently by others and have active modern day equivalents

organic geochemistry and petrography of kazhdumi albian cenomanian and pabdeh paleogene potential source rocks in southern part of the dezful embayment iran there are several source rock units in the zagros basin but the cretaceous kazhdumi and paleogene pabdeh formations probably have produced the majority of the commercial hydrocarbons in this area among the hydrocarbon provinces of iran the dezful embayment which is located southwest of zagros mountains is one of the most prolific regions in the middle east numerous studies have been made in the northern part of the dezful embayment but relatively few have been done in its southern part the present study focuses on organic matter characterization of two potential source rocks kazhdumi and pabdeh formations in southern part of the dezful embayment cuttings samples 114 were collected from 10 wells and evaluated using rock eval pyrolysis and organic petrography in order to characterize the content and type of organic matter and thermal maturity the results showed that the average total organic carbon toc content of kazhdumi and pabdeh formations are 2 48 and 1 62 wt respectively the highest toc contents for both formations are found in the northern compartment and decreased gradually toward the south pyrolysis data reveal that organic matter has a fair to very good hydrocarbon generation potential and are classified as type ii iii and type iii rock eval t max and vitrinite reflectance show that the majority of samples are in the early mature to mature stage of the oil generation window c 2012 elsevier ltd all rights reserved

dynamical causes for incipient magma chambers above slabs using a regional upper mantle model with an unprecedented spatial resolution of 100 m we have investigated at multiple resolutions the character of incipient magma chambers forming under oceanic arcs the magma chambers are formed from wave like structures propagating upward along descending slabs and consist of compositionally buoyant hydrated partially molten subducted crustal and mantle material these wave structures are 300 500 c colder than the mantle wedge and may have an upward velocity of 1 m yr inverted temperature structures and transitory bimodal magmatism are plausible consequences of finger like penetration of relatively cold hydrated material of the incipient magma chambers into the hot mantle wedge apart from forming and periodic feeding of the magma chambers cold waves may also transport upward thousands of cubic kilometers of subducted material and may cause the rapid exhumation of ultrahigh pressure rocks along slabs

new seismological constraints on growth of continental crust in the izu bonin intra oceanic arc the process by which continental crust has formed is not well understood though such crust mostly forms at convergent plate margins today it is thus imperative to study modern intra oceanic arcs such as those common in the western pacific ocean new seismic studies along the representative izu bonin intra oceanic arc provide unique along strike images of arc crust and uppermost mantle to complement earlier cross arc lithospheric profiles these reveal two scales 1000 10 km scale of variations one at the scale of the izu versus bonin thick versus thin arc crust the other at the intervolcano 50 km scale these images show that 1 the bulk composition of the izu bonin arc crust is more mafic than typical continental crust 2 the middle crust with seismic velocities similar to continental crust is predominantly beneath basaltic arc volcanoes 3 the bulk composition beneath basaltic volcanoes changes little at thick and thin arc segments and 4 a process to return lower crustal components to the mantle such as delamination is required for an arc crust to evolve into continental crust continued thickening of the izu bonin crust accompanied by delamination of lowermost crust can yield velocity structure of typical continental crust

reaction of the lake environment to the holocene warming depending on the distance to the maximum extent of the vistulian ice sheet abstract this study presents 1 the results of a stable isotope and subfossil cladocera analyses of lacustrine sediments from maliszewskie lake e poland and next 2 different reaction of the lake environments depending on the lake s localization maliszewskie lake is located in north podlasie lowland ca 30 km to the south of the vistulian ice sheet limit the approximately 4 80 m thick sediments maliszewo i profile are mainly comprised of calcareous gyttja covered by peat and organic detritus gyttja pollen analysis documents that the sediments accumulated from the late glacial allerod period to recent times based on the results of stable isotope and subfossil cladocera analyses of sediments the lake environmental changes were reconstructed a positive trend in 18o and 13c values documents a gradual climatic warming the fluctuations of the oxygen isotopic values suggest the multiple oscillation of water level due to a change in the evaporation precipitation ratio the subfossil cladoceran fauna in the maliszewo i profile is represented by 21 species belonging to five families three zones of cladocera development were distinguished the cladocera species indicate the initial oligotrophic status of the lake and its subsequent increase of trophic status currently maliszewskie lake is a very shallow declining reservoir the initial period of its existence probably saw its maximal depth in presented studies we compared our results with data from three other sites documenting the reaction of the lake environment during the late glacial and holocene transformation at that time we observed different reactions to the climate amelioration in the northern postglacial lakes the holocene warming at first provoked an input cold melting water characterized by more negative oxygen isotope values and then a rise in water temperature in the lakes further away from the glaciation border periglacial lakes the increase in water temperature documented by e g more positive oxygen isotopic immediately occurred the climate warming is commonly manifested by a significant increase of number of species and individuals of cladocera

palynology and petroleum potential of the kazhdumi formation cretaceous albian cenomanian in the south pars field northern persian gulf abstract the kazhdumi formation of the bangestan group is a well known source rock that has produced abundant oil in most petroleum fields in the zagros basin which stretches from northwest to southwest iran over hundreds of kilometres the formation reaches a thickness of 230 m at the type section in northwest zagros but thins out to 40 50 m in wells studied from the south pars giant petroleum field where it comprises mainly grey shales with occasional intercalations of marls and sandstones south pars best known as the iranian part of the world s largest non associated gas field contains small quantities of oil above and below the kazhdumi formation palynology has been used to assess the age and palaeoenvironment of the kazhdumi formation and to evaluate its petroleum potential a total of 68 ditch cutting samples recovered from five wells of which four are oil prone have been analyzed an age between late albian and cenomanian is established for the formation based on dinoflagellate cyst biostratigraphy and four palynofacies types have been recognized using the relative proportions of terrestrial elements marine palynomorphs and amorphous organic matter aom the ratio of terrestrial to marine elements is high in most samples indicating a nearshore sedimentary environment twenty two samples from the four oil prone wells were also selected for geochemical analysis using rock eval pyrolysis results show that the kazhdumi formation at south pars in contrast to the zagros basin is gas prone predominantly type iii kerogen thermally immature and poor in terms of hydrocarbon generation it could not have produced the oil in those oil prone wells studied

occurrence of organic matter rich deposits middle jurassic to lower cretaceous from qalikuh locality zagros basin south west of iran a possible oil shale resource abstract organic rich deposits of qalikuh locality zagros basin southwest of iran are unconventional hydrocarbon resources considered as an oil shale which is hosted within a carbonate succession with the age range of middle jurassic to lower cretaceous leco carbon rock eval vi and modified fischer assay analysis were performed on some outcrop samples of these resources to investigate the occurrence of oil shale in the studied samples mean total organic carbon toc is 17 3 wt and the average of petroleum genetic potential s1 s2 is 98 kg hc t rock furthermore toc has direct relationship with petroleum genetic potential hydrogen index hi tmax diagram indicates that the organic matter corresponds to type ii kerogen of probable marine origin with high quality of oil generation according to rock eval data and bitumen reflectance brr the samples are thermally early mature based on the studied samples oil yield of the qalikuh oil shales ranges from 6 1 to 7 9 wt mean oil gas ratio is 2 7 and mean oil yield is 56 7 l t rock according to the observations the production value of qalikuh oil shale is more or less similar in the entire studied regions whereas the total production is below the expected values the produced oil is considerably lighter higher api than that of most other known oil shales

preboreal climate oscillations in europe wiggle match dating and synthesis of dutch high resolution multi proxy records abstract in order to compare environmental and inferred climatic change during the preboreal in the netherlands five terrestrial records were analysed detailed multi proxy analyses including microfossils e g pollen spores algae and fungal spores macroremains e g seeds fruits wood mosses etc and loss on ignition measurements were carried out with high temporal resolution to link the five preboreal records accurate chronologies were produced by ams 14c wiggle match dating the dutch records show that following the lateglacial holocene climate warming birch woodlands expanded between 11 530 and 11 500 cal bp during the friesland phase of the preboreal after the friesland phase two distinct climatic shifts could be inferred 1 around 11 430 11 350 cal bp the expansion of birch forests was interrupted by a dry continental phase with open grassland vegetation the rammelbeek phase this phase was coeval with the coldest part of the preboreal oscillation pbo as observed in the 18o record of the greenland ice core records and has been attributed to a large meltwater flux that resulted in a temporary decrease of the thermohaline circulation in the north atlantic 2 at the start of the late preboreal between 11 270 and 11 210 cal bp a sudden shift to a more humid climate occurred and birch forests expanded again a simultaneous increase in the cosmogenic nuclides 14c and 10be suggests that these changes in climate and vegetation were forced by a sudden decline in solar activity expansion of pine occurred during the later part of the late preboreal at the onset of the boreal between 10 770 and 10 700 cal bp dense woodlands with hazel oak elm and pine started to develop in the netherlands

restoration of exotic terranes along the median tectonic line japanese islands overview abstract this paper reviews recent progress on the geotectonic evolution of exotic paleozoic terranes in southwest japan namely the paleo ryoke and kurosegawa terranes the paleo ryoke terrane is composed mainly of permian granitic rocks with hornfels mid cretaceous high grade metamorphic rocks associated with granitic rocks and upper cretaceous sedimentary cover they form nappe structures on the sambagawa metamorphic rocks the permian granitic rocks are correlative with granitic clasts in permian conglomerates in the south kitakami terrane whereas the mid cretaceous rocks are correlative with those in the abukuma terrane this correlation suggests that the elements of northeast japan to the northeast of the tanakura tectonic line were connected in between the paired metamorphic belt along the median tectonic line southwest japan the kurosegawa terrane is composed of various paleozoic rocks with serpentinite and occurs as disrupted bodies bounded by faults in the middle part of the jurassic chichibu terrane accretionary complex it is correlated with the south kitakami terrane in northeast japan the constituents of both terranes are considered to have been originally distributed more closely and overlay the jurassic accretionary terrane as nappes the current sporadic occurrence of these terranes can possibly be attributed to the difference in erosion level and later stage depression or transtension along strike slip faults the constituents of both exotic terranes especially the ordovician granite in the kurosegawa south kitakami terrane and the permian granite in the paleo ryoke terrane provide a significant key to reconstructing these exotic terranes by correlating them with paleozoic granitoids in the eastern asia continent

a classification of petroleum on the basis of the ratio of sulfur to nitrogen abstract examination of the ratio of organic sulfur to organic nitrogen s n in 455 petroleums shows that individual petroleum families selected geographically stratigraphically and by source exhibit distinctive limited ranges of the value of this ratio commonly observed values in petroleums are between 1 and 20 the coefficient of variation within a family is frequently 100

stable carbon isotope compositions of crude oils application to source depositional environments and petroleum alteration the carbon isotopic composition of the c15 saturate and aromatic hydrocarbon fractions and the gas chromatographs of the c15 saturate fraction of 339 oils were geochemically and statistically evaluated results of this study show that the average isotopic compositions of the c15 aromatic hydrocarbon fractions of oils sourced from terrigenous or marine organic matter are identical the average isotopic composition of the c15 saturate fraction of oils derived from terrigenous organic sources is slightly more negative 0 9 pmil than the average for marine oils but this difference is insufficient to be used as a reliable source indicator reports in the literature stating that marine oils are isotopically more positive than te rigenous oils and that the difference can be utilized to distinguish between the two are therefore not supported by this study the isotopic differences between oils sourced from terrigenous and marine organic matter do not manifest themselves in the range of absolute values of one oil fraction but rather in the isotopic relationship between the saturate and aromatic hydrocarbon fractions the isotopic relationship is the following oils of terrigenous organic source dgr13caro 1 12 dgr13csat 5 45 oils of marine organic source dgr13caro 1 10 dgr13csat 3 75 the difference between the two equations was evaluated statistically and a statistical parameter cv the canonical variable cv 2 53 dgr13csat 2 22 dgr13caro 11 65 was used to distinguish between marine and terrigenous oils cv values larger than 0 47 indicate predominantly a terrigenous organic source for the oil whereas cv values smaller than 0 47 indicate mostly a marine organic source thermal maturity differences in oils and isotopic variations in the source beds can cause as much as 2 pmil variations in the isotopic composition of one family of oils finally stable carbon isotopes can in some situations help correlate biodegraded oils to their nondegraded counterparts

petroleum system analysis of the northwestern part of the persian gulf iranian sector abstract geochemical geological and geophysical data were used to identify and update genetic oil families potential source rocks and hydrocarbon generation kitchen as well as probable migration pathways in the northwestern part of the persian gulf rock eval analysis was performed on 52 cutting samples of prospective cretaceous tertiary source rocks according to the results most of the samples have poor to fair potential for hydrocarbon generation except for the albian formation which possesses good to excellent source rock characteristics in the study area two genetic oil families were identified based on source and age related biomarkers as well as stable carbon isotope ratios for 23 crude oil samples family i occurs in upper jurassic lower cretaceous reservoirs mainly in the surmeh hith basin whereas family ii occurs in lower cretaceous tertiary reservoirs mainly in the garau gotnia basin all attempts to correlate the identified families to prospective source rocks failed due to substantial maturity differences between the oils and rock samples inversion correlation based on detailed isotopic and biomarker analyses however confirms that the carbonates and marls of the neocomian and albian formations are the main oil generating facies for families i and ii respectively the geographical extension and composition of the identified oil families are highly affected by source rock facies distribution and migration pathways 2d cross sections provided in the region indicate the dominance of lateral and vertical migration pathways from the binak depression as the main hydrocarbon generation kitchen toward the structural highs in the study area

lateglacial and early holocene environmental changes in northeastern lithuania abstract multiproxy data pollen diatoms plant macrofossils 14c and loss on ignition measurements obtained from two cores petrasi nai and juodonys were used to reconstruct the pattern of lateglacial and early holocene environmental changes in ne lithuania the flourishing of open pinus forest and presence of light demanding taxa on poor unstable soils surrounding shallow water basins have been recorded from about 13 100 13 000 cal bp to 12 600 cal bp in the study area after 13 000 cal bp expansion of betula dominated vegetation and increased abundance of cold tolerant plants together with a simultaneous drop of water temperature indicates a short climate deterioration tentatively correlated with the gerzensee oscillation a sudden reduction of the forest cover and extensive development of grass herb dominated landscape is suggestive of a regional expression of the younger dryas cooling dated to 12 600 11 500 cal bp climate aridification resulted in a progressive lowering of the water level and subsequent overgrowth of the basins early holocene vegetation changes show a pattern of forest development with dominance of spruce shortly after 11 500 cal bp based on palynological evidence and the presence of plant macrofossils seeds and needles early holocene immigration of picea sp to juodonys 9410 310 bp vs 1433 and petrasi nai 9420 65 bp tua 6177 df2471 is indicated further development of the vegetation cover indicates multiple flourishing of predominant open birch vegetation subsequently followed by pine spruce forest development caused by preboreal climate instability the most prominent climate shift e g drop of the temperature and humidity recorded shortly before 11 100 cal bp has been correlated with the preboreal oscillation bjorck s rundgren m ingolfsson o funder s 1997 the preboreal oscillation around the nordic seas terrestrial and lacustrine responces journal of quaternary science 12 455 465 expansion of birch predominant forest around shallow water basins has been identified during the late preboreal after 11 100 cal bp

early holocene hydrology and environments of the ner river poland abstract the ner river valley central poland underwent substantial transformation during the weichselian holocene transition as a result of fluvial processes and climate changes resulting in the establishment of its present shape in the holocene a multiproxy study based on organic deposits from a palaeochannel fill lutomiersk koziowki shows that after the channel was cut off during the late glacial termination it became a shallow oxbow fed by local springs in the boreal period the oxbow lake was also fed by precipitation and became a telmatic environment overgrown by rush and swamp vegetation finally it was covered by overbank deposits the first flooding phase 9900 9600 cal bp was followed by the accumulation of overbank sediments after 9500 cal bp and flooding increased after ca 9300 9000 cal bp pollen data provide information on the regional vegetation context for local and regional changes in the atlantic period an increase in both summer and winter temperatures is inferred from the pollen data corresponding to an expansion of thermophilous deciduous forests while in general flooding phases of the early holocene are poorly recognised in eastern europe the lutomiersk koziowki site may be considered as one of the reference points for this phenomenon in the region

the temperature of europe during the holocene reconstructed from pollen data we present the first area average time series reconstructions of warmest month coldest month and mean annual surface air temperatures across europe during the last 12 000 years these series are based on quantitative pollen climate reconstructions from over 500 pollen sites assimilated using an innovative four dimensional gridding procedure this approach combines three dimensional spatial gridding with a fourth dimension represented by time allowing data from irregular time series to be focussed onto a regular time step we provide six regional reconstructed temperature time series as well as summary time series for the whole of europe the results suggest major spatial and seasonal differences in holocene temperature trends within a remarkably balanced regional and annual energy budget the traditional mid holocene thermal maximum is observed only over northern europe and principally during the summer this warming was balanced by a mid holocene cooling over southern europe whilst central europe occupied an intermediary position changes in annual mean temperatures for europe as a whole suggest an almost linear increase in thermal budget up to 7800 bp followed by stable conditions for the remainder of the holocene this early holocene warming and later equilibrium has been mainly modulated by increasing winter temperatures in the west which have continued to rise at a progressively decreasing rate up to the present day

burial history reconstruction and thermal maturity modeling for the middle cretaceous early miocene petroleum system southern dezful embayment sw iran abstract the middle cretaceous early miocene petroleum system is the most important hydrocarbon system in the zagros basin rock eval pyrolysis organic petrography and thermal 1d modeling were performed on wells located in the southern dezful embayment the results provide information on organic matter quantity and quality as well as burial and thermal histories of source rocks in the framework of the basin evolution a total of 98 cutting samples from bk 4 kk 1 si 4 and rs 2 wells were pyrolyzed by rock eval 6 also thermal maturity of organic matter derived from tmax of rock eval was interpreted in conjunction with vitrinite reflectance data 50 samples the toc values of the sequences mainly range from 0 5 to 2 5 wt the average values of tmax and vitrinite reflectance indicate that samples from the wells have reached maturities corresponding to early mid oil generation reconstruction of thermal history suggests that various steady heat flow values 62 54 50 and 56 mw m2 for bk 4 kk 1 si 4 and rs 2 wells respectively resulted in the best fit between the calculated and the observed vitrinite reflectance and bottom hole temperatures in our modeling thus values of heat flow decrease from 60 mw m2 in the southern basin margin to about 50 mw m2 along the ne of the dezful embayment and the zagros basin according to our modeling results the onset of oil generation from source rocks in the studied area occurs well after deposition of the seal rock and formation of traps ensuring entrapment and preservation of migrated hydrocarbons

high resolution stable isotope records from southwest sweden the drainage of the baltic ice lake and younger dryas ice margin oscillations benthic foraminifera in two shallow marine sediment cores from southwest sweden were analyzed for oxygen isotopes several deglaciation events previously recognized in terrestrial and lake sediments throughout the baltic region are identified and radiocarbon dated an initial baltic ice lake bil drainage at the mount billingen threshold is inferred from a distinct 2 4 18o oscillation in one of the investigated cores the estimated radiocarbon age for this event is approximately 10 900 14c years the final drainage which ended bil history occurred in two steps during the younger part of the radiocarbon plateau at 10 000 14c years biostratigraphy suggests that the final drainage took place in the climatically warm early preboreal at approximately 11 150 14c years the deglacial trend toward lighter isotopic composition was interrupted and slightly reversed and is interpreted to represent the onset of the cold younger dryas period for a few hundred years prior to the younger dryas melting of the fennoscandian ice sheet appears to have been rapid besides the dramatic drainage events and reduced melting during the younger dryas the records display several other salinity variations these variations may reflect ice margin oscillations during the younger dryas previously identified throughout scandinavia as ice marginal deposits the isotopic records suggest approximately 10 climatically induced ice margin recession readvances of the southeastern fennoscandian ice sheet during the younger dryas

accretion of japanese island arcs and implications for the origin of archean greenstone belts the present day region of arc arc collision between the izu bonin arc and mainland japan honshu arc in the western pacific called the izu collision zone or icz provides a useful kinematic model for the development of many archean greenstone belts the compositional assemblage thermal structure and structural style of the crust in the icz are very similar to those inferred for many archean greenstone belts in both cases thick young and flaky arc crust with a high heat flux is in collision with another crustal block the icz has resulted in the imbrication of very thick slices of crust and associated sediments juxtaposed against older accretionary prisms many archean greenstone belts show similar geological features and we suggest that the incremental imbrication of the crust was a common tectonic style in some archean convergent margins

environmental changes related to the 8 2 ka event and other climate fluctuations during the middle holocene evidence from two dystrophic lakes in ne poland multi proxy palaeoecological data pollen diatom cladocera about the environment during the middle holocene from suchar ii and suchar wielki dystrophic lakes in ne poland are presented fluctuations in the pollen concentration indicative of changes in pollen productivity and shifts in woodland composition document the considerable instability of the climate in ne poland between 9200 and 5750 cal yr bp the recognised colder events were dated to ca 9050 8950 8700 7800 7600 7250 7100 6600 and 6050 5900 cal yr bp all these coolings are expressed as decreases in the pollen concentration of thermophilous taxa such as corylus avellana ulmus quercus tilia cordata t and fraxinus exelsior the most pronounced was the second of these cold climatic anomalies which lasted about nine centuries and can be equated with the 8 2 ka event significant cooling at that time is confirmed by the appearance of cold water species of cladocerans and diatoms

an experimental study into the rheology of synthetic polycrystalline coesite aggregates coesite has been found as a relic in ultrahigh pressure metamorphic uhpm crust worldwide and is expected to play a major role in the mechanical behavior of continental crust at uhpm conditions we performed triaxial compression tests on synthetic polycrystalline coesitite in a solid medium apparatus at confining pressures of 3 1 to 3 7 gpa temperatures of 700 to 1160 c and strain rates betweeen 6 10 7 and 1 10 3 s 1 the problem of the limited stress resolution of the solid medium apparatus was addressed by applying two extreme friction corrections that yield lower and upper bounds to the differential stress the correlation between the mechanical data and the microstructural record of the deformed samples as a function of temperature and imposed strain rate is consistent with deformation by dislocation creep we deduced parameters of a power law as n 3 1 and q 275 50 kj mol 1 extrapolation of the experimental data to natural conditions cannot be constrained by comparison with natural microstructures due to the lack of preserved coesite other than as single crystal inclusions nevertheless the extrapolation indicates a low strength of order 10 mpa for natural strain rates at typical uhpm conditions absent deformation of the uhpm brossasco granite dora maira massif western alps thus implies low stresses deformation must have been localized in very weak shear zones during burial and exhumation

quantitative reconstruction of younger dryas to mid holocene paleoclimates at le locle swiss jura using pollen and lake level data abstract pollen and lake level data from le locle in the swiss jura were used to quantitatively reconstruct climatic parameters for the younger dryas event and the first half of the holocene period the younger dryas cold event at le locle was characterized by i a general trend toward a slight increase in summer temperature and a decrease in annual precipitation and ii a marked drying phase at ca 11 900 cal yr b p that occurred between two wetter ones further phases of major deficit in moisture occured at ca 11 500 cal yr b p younger dryas holocene transition 10 800 cal yr b p 8700 cal yr b p and 6500 cal yr b p climatic parameters reconstructed here suggest that phases of higher lake level developing at ca 12 500 12 000 11 750 11 600 11 200 10 900 synchronous with the preboreal oscillation 10 400 8900 8400 8300 possibly related to the 8200 yr event and 7800 7000 cal yr b p coincided with an increase in annual precipitation a decrease in summer temperature and a shorter growing season conversely periods of low lake level corresponded to a decrease in annual precipitation an increase in summer temperature and a longer growing season this general pattern could have resulted from alternate southward northward displacements of the atlantic westerly jet

ab initio investigation of high pressure phase relation and elasticity in the naalsi2o6 system 1 subducted crusts contain aluminous phases with incompatible elements such as sodium in order to understand the fate of subducted crusts and how they recycle within the earth it is important to investigate high pressure stability and elastic properties of host phases here we have studied naalsi2o6 jadeite a naalsio4 calcium ferrite cf type phase and sio2 stishovite by means of a first principles computation method jadeite was found to dissociate into an assemblage of the cf type phase and stishovite at about 18 gpa associated with remarkable increases of compressional wave 18 7 shear wave 26 4 bulk sound 13 3 velocities and density 15 1 proximity of this transition condition to the 660 km discontinuity in the mantle transition zone suggests that seismically observed splitting of the reflection could be related to this phase transition implying subduction of crustal materials down to the mantle transition zone

gas prospective areas in the zagros domain of iran and in the gulf iranian waters in the province of fars and in its offshore gas reserves in excess of 600tcf discovered in permo triassic carbonates well sealed by the anhydrite of the dashtak fm were originated from early llandoverian highly organic and radioactive shales the current distribution of this source rock was influenced by the pre permian erosion on a system of n s tilted blocks extensive geochemical modeling has shown that oil generation began in the middle jurassic in some areas while the onset of gas window was reached locally as early as middle cretaceous a suite of cumulative isopachs shows the evolution of the source rocks maturity through time it also provides a reliable image of the geometry of the reservoirs the long range migrations and the location of large size oil and gas accumulations on a few continuous regional highs prior to the zagros orogeny huge amounts of gas and limited amounts of light oil later re accumulated in the zagros folds formed during the late miocene and pliocene the characteristics of the dalan and kangan reservoirs and the areal extent of the dashtak fm which seals the system could be deduced from paleogeographic reconstruction distribution of facies and isopachs the distribution of the reservoirs seals surface oil and gas seepages and hydrocarbon related indications together with the location of the gas fields makes possible to select among the numerous permotriassic prospects those which are the most attractive some prospects may also contain light oil rings below gas the silurian source rocks in the zagros foothills of iran a variety of proterozoic rocks were uplifted by proterozoic salt diapirs hormuz fm but no source rocks were found in the few hormuz samples we analyzed no source rocks were found either in the cambro

paleogeographic reconstruction and origin of the philippine sea abstract our reconstruction of the philippine sea suggests that it formed by two distinct episodes of back arc spreading each of which resulted from seaward retreat of the trench in the first episode the protoizu bonin trench retreated northward and the west philippine basin formed behind the northern half of the palau kyushu ridge in the second episode the izu mariana trench retreated eastward and the shikoku and parece vela basins formed behind it during the last 17 ma the philippine sea basin has been moving northwestward with respect to eurasia shifting the ttt triple junction off central japan westward by about 50 km the motion of the philippine sea with respect to eurasia at the triple junction changed from north northwestward to west northwestward 10 5 ma ago for the period before 17 ma ago we construct two models retreating trench model and anchored slab model the izu bonin trench migrated from south to northeast rotating in a clock wise sense since 48 ma ago in the retreating trench model in the anchored slab model the trench has been fixed with respect to eurasian margin since 43 ma ago we prefer the retreating trench model because the deformation of the plate boundary along the eastern margin of eurasia during 30 17 ma ago is much simpler for this model than for the anchored slab model furthermore rotations of the bonin mariana islands are consistent with those predicted from the retreating trench model the 48 ma ages of the northern part of the palau kyushu ridge and of chichi jima of the bonin islands indicate that there was subduction beneath the northern half of the ridge beginning at least 48 ma ago from this and the subparallelism in trend between the northern part of the palau kyushu ridge and the central basin ridge we propose that the major part of the west philippine basin formed by back arc spreading in a n s direction behind the northern part of the palau kyushu ridge the pacific plate was moving northward with respect to hot spots from 48 to 43 ma ago which implies that the pacific plate is not likely to have been subducting beneath the west philippine basin during this time we speculate that another plate existed south of the pacific plate and thai it was subducting beneath both tile west philippine basin and australia the annihilation of this plate might he a cause for the sudden change of the pacific plate motion at 43 ma ago

study of hydrocarbon generation and 1d 2d modeling of hydrocarbon migration at the karanj and parsi oilfields southern dezful embayment sw iran abstract this study is a 2d basin modeling to determine the petroleum system i e cretaceous neogene play of the karanj and parsi oilfields in the southern dezful embayment sw iran this system is characterized by occurrence of source rocks of middle cretaceous late cretaceous and paleocene to eocene kazhdumi pabdeh and gurpi formation reservoirs of upper cretaceous and late oligocene early miocene ilam sarvak and asmari formations and seals of paleocene and miocene pabdeh and gachsaran formation considering temperature transformation ratio and vitrinite reflectance the maturity of source rocks kazhdumi pabdeh and gurpi formation was investigated a maturity history analysis showed that the maturity of kazhdumi pabdeh and gurpi formation started during 70 60 and 4 ma respectively generation and expulsion of hydrocarbons started 16 ma in the kazhdumi formation and 3 ma in the pabdeh formation that continued up to the present the analysis of the transformation ratio indicates transformation of significant amounts of kazhdumi source rocks for generating hydrocarbons migration of hydrocarbons from the kazhdumi formation is mainly vertically upward from pabdeh formation migration is both vertically upward to the asmari reservoir and downwards to the ilam sarvak reservoir however some local traps have formed due to the hydrocarbon accumulation above the faults our results reveal that petroleum generation migration and entrapment occurred at proper timing which facilitated the migration of hydrocarbons and their accumulation in the reservoirs