quantifying climatic change through the last glacial interglacial transition based on lake isotope palaeohydrology from central turkey questions remain as to the nature of climatic change through the last glacial interglacial transition in the eastern mediterranean region particularly the relative contribution of evaporation and precipitation to regional water balance here changes in oxygen isotope values through this time period from eski acigol a crater lake in central turkey are investigated using hydrological and isotope mass balance models these allow changes in evaporation and precipitation to be quantified and their relative importance evaluated we show that it is the volumetric flux rate of water passing through the lake system and not the precipitation to evaporation ratio per se which controlled the stable isotope record in eski acigol early holocene precipitation is shown to be much greater than that during both the latter part of the last glaciation and the present day we test these calculated values against other records in the same region firstly with other lake records in anatolia the konya basin and lake van and secondly with isotope inferred palaeo precipitation data from soreq cave in israel this reveals a contrast between pre and post lgm precipitation values in turkey wetter and drier respectively and also suggests that during the last glacial interglacial transition there was a more marked precipitation gradient than at present between northern interior and southern coastal parts of the eastern mediterranean region

could the conventionally known abu roash g reservoir upper cenomanian be a promising active hydrocarbon source in the extreme northwestern part of egypt palynofacies palaeoenvironmental and organic geochemical answers abstract in different areas of the western desert of egypt the abu roash g member exhibits either a reservoir or source affinity thus thirteen cutting samples covering the abu roash g member were selected from the nest 1a well at matruh basin to investigate its hydrocarbon source potential palynological age dating of the section that is calibrated with foraminifera and ostracodes enabled a proper identification of the g member detailed analysis of the vertical distribution of particulate organic matter of this member shows two palynofacies types pf 1 reflects an outer middle shelf depositional environment of prevailed reducing suboxic anoxic conditions for the organic rich shales of the lower g member samples 1 8 while pf 2 reflects a minor regression that resulted in deposition of another organic rich shales of the upper g member samples 9 13 in an inner middle shelf setting under the same prevailing reducing suboxic anoxic conditions organic geochemical analysis reveals good to very good potential of the g member as a hydrocarbon source rock 1 8 2 41 avg 2 15 total organic content wt it also shows good to very good petroleum potential pp 4 8 11 avg 8 mg hc g rock pyrolsis and palynofacies analyses show kerogen type ii for the lower g member samples 1 8 which is characterized by high hydrogen index hi 396 and 329 mg hc g toc at depths 1500 and 1560 m and very high dominance of oil prone material amorphous organic matter aom marine palynomorphs and sporomorphs and very rare occurrence of gas prone material brown phytoclasts the upper g member samples 9 13 shows kerogen type ii iii which is characterized by a lower hi value of 213 mg hc g toc at depth 1340 m and it contains fewer amounts of gas prone material and relatively lower aom and marine palynomorphs in comparison to the upper g member maturation parameters t max 430 433 c production index pi 0 1 mg hc g rock and thermal alteration index tai 2 indicate the lower g member has already entered the early oil window kitchen and it is expected to produce oil the upper g member is expected to produce only oil with no gas shows because it is marginally mature t max 426 c pi 0 2 tai 2 the source potential index spi 5 3 t hc m 2 of the g member shows it as currently generating moderate quantities of oil in the area of nest 1a well consequently the organic rich shales of the g member are suggested here as a promising active oil source rock in that extreme northwestern part of the western desert of egypt however for commercial oil recovery from the abu roash g member it is highly recommended to explore the depocentre of matruh basin at about 150 km east the nest 1a well

palynological palaeoenvironmental and sequence stratigraphical analyses of a turonian coniacian sequence beni suef basin eastern desert egypt implication of pediastrum rhythmic signature abstract sixteen samples from the e to b members of the abu roash formation encountered in the beni suef basin eastern desert of egypt were palynologically analyzed for palaeoenvironmental and sequence stratigraphic investigations the integrated palynofacies and lithofacies analysis of the studied section indicates deposition of five alternating regressive and transgressive sequences in well oxygenated proximal shelf settings the abu roash e and the upper d to the lower c members were deposited during pronounced regressive phases in oxic shallow marginal marine settings the upper b member was deposited during a recurring regressive phase but of a lower magnitude in oxic shallow inner neritic conditions the lower d member was deposited during a minor transgression phase in dysoxic shallow inner neritic settings while the upper c to the lower b section was deposited during a stronger transgressive episode in a relatively deep inner neritic environment of prominent dysoxic conditions this interchange in the depositional setting was documented by the pronounced and concurrent cyclic nature of the freshwater algae peridinioid dinoflagellate cysts pteridophyte spores and reworked sporomorphs with variable intensities their increasing and conversely their diminishing trends clearly reflect alternating regressive transgressive periods of reduced and relatively normal salinity conditions respectively overall sedimentation of the studied abu roash section indicates a recurring rise in sea level which accentuated during the earliest santonian time the analogous peaking in the pediastrum signals with those of the pteridophyte spores and reworked taxa indicate a good connection between these pediastrum signals and the pronounced fluviatile influxes of terrigenous sediments during regressive phases accordingly this can be used to identify regressive sequence boundaries and hence the clastic reservoirs even with the small counts recorded herein we believe high ratios of peridinioid gonyalulacoid dinocysts are significantly paralleled by peaking signals of freshwater algae and regressive sedimentation phases this must be preliminary documented here probably future palynological studies will be able to fully interpret and address this important pediastrum rhythmic event in different sequence stratigraphic settings the palynological parameters age controlled sporomorph marker taxa lithology and gamma ray data were used to differentiate the abu roash members into three distinctive 3rd order depositional sequences ar sq1 ar sq2 and ar sq3 these sequences match well with the global stratigraphic sequences tu 3 tu 4 and co 1 and connect the local rise in sea level to the global eustatic sea level rise

late neogene and active orogenic uplift in the central pontides associated with the north anatolian fault implications for the northern margin of the central anatolian plateau turkey 1 surface uplift at the northern margin of the central anatolian plateau cap is integrally tied to the evolution of the central pontides cp between the north anatolian fault naf and the black sea our regional morphometric and plate kinematic analyses reveal topographic anomalies steep channel gradients and local high relief areas as indicators of ongoing differential surface uplift which is higher in the western cp compared to the eastern cp and fault normal components of geodetic slip vectors and the character of tectonic activity of the naf suggest that stress is accumulated in its broad restraining bend seismic reflection and structural field data show evidence for a deep structural detachment horizon responsible for the formation of an actively northward growing orogenic wedge with a positive flower structure geometry across the cp and the naf taken together the tectonic plate kinematic and geomorphic observations imply that the naf is the main driving mechanism for wedge tectonics and uplift in the cp in addition the naf zone defines the boundary between the extensional cap and the contractional cp the syntectonic deposits within inverted intermontane basins and deeply incised gorges suggest that the formation of relief changes in sedimentary dynamics and 1 km fluvial incision resulted from accelerated uplift starting in the early pliocene the central pontides thus provide an example of an accretionary wedge with surface breaking faults that play a critical role in mountain building processes sedimentary basin development and ensuing lateral growth of a continental plateau since the end of the miocene

late quaternary marine mollusca as palaeoenvironmental proxies a compilation and assessment of basic numerical data for ne atlantic species found in shallow water abstract temperature salinity and depth limits are given for selected molluscs from boreal and arctic regions of the ne atlantic and adjacent shelf seas the significance of the data for palaeoenviromental analysis is briefly discussed

palaeoclimatic evolution and vegetational changes during the late oligocene miocene period in western and central anatolia turkey abstract neogene basins are widespread in turkey and contain important lignite deposits in this study we reconstruct quantitatively the late oligocene miocene climate evolution in western and central anatolia by applying the coexistence approach to the palynofloras obtained from the published literatures and ongoing studies the coexistence approach results show that sedimentation occurred mainly under warm subtropical climatic conditions during the chattian and aquitanian period in western anatolia 16 5 21 3 c mean annual temperature mat and 5 5 13 3 c mean temperature of coldest month cmt rare occurrences of dinoflagellate cysts in the chattian and aquitanian indicates a marine influence after the regression of the sea during the burdigalian period climate becomes cooler due to a decrease of the palaeotropical arctotertiary ratio during the latest burdigalian langhian vegetation developed under terrestrial conditions which had started in the burdigalian time in western and central anatolia and continued to the early middle serravallian period the climate was subtropical in western and central anatolia during the early late serravalian 17 2 to 20 8 c for mat and 9 6 to 13 1 c for cmt besides increase of the cmt and mat values in western and central anatolia supports the latest chattian earliest aquitanian warming and middle miocene climatic optimum being also globally observed warm temperate climatic conditions are observed in the late miocene during the early middle tortonian the values are 15 6 to 20 8 c for the mat 5 5 to 13 3 c for the cmt and 823 and 1520 mm for the mean annual precipitation map they had experienced dry seasons due to lower boundary of map lying at 823 mm during the middle late tortonian the palaeotopography of central anatolia was higher compared to that of western anatolia during the middle late miocene as indicated by a rich species diversification in mountain forests this study provides the first quantitative model for late oligocene miocene palaeoclimatic evolution in western and central anatolia

lower cretaceous black shales of the western carpathians czech republic palynofacies indication of depositional environment and source potential for hydrocarbons abstract uppermost jurassic and lower cretaceous strata of the silesian nappe of the outer western carpathians contain large amounts of shale which can under favourable conditions become source rocks for hydrocarbons this study analysed 45 samples from the area of czech republic by the means of palynofacies analysis thermal alteration index tai of palynomorphs and total organic carbon toc content to determine the kerogen type hydrocarbon source rock potential and to interpret the depositional environment uppermost jurassic vendryn formation and lower cretaceous formations t sin limestone hradist and lhoty reveal variable amount of mostly gas prone type iii kerogen aptian ve ovice formation has higher organic matter content over 3 wt and oil prone type ii kerogen organic matter is mature to overmature and hydrocarbon potential predisposes it as a source of gas aptian black claystones of the ve ovice fm are correlatable with oceanic anoxic event 1 oae1

segmented african lithosphere beneath the anatolian region inferred from teleseismic p wave tomography summary lithospheric deformation throughout anatolia a part of the alpine himalayan orogenic belt is controlled mainly by collision related tectonic escape of the anatolian plate and subduction roll back along the aegean subduction zone we study the deeper lithosphere and mantle structure of anatolia using teleseismic finite frequency p wave traveltime tomography we use data from several temporary and permanent seismic networks deployed in the region approximately 34 000 p wave relative traveltime residuals measured in multiple frequency bands are inverted using approximate finite frequency sensitivity kernels our tomograms reveal segmented fast seismic anomalies beneath anatolia that corresponds to the subducted portion of the african lithosphere along the cyprean and the aegean trenches we identify these anomalies as the subducted aegean and the cyprus slabs that are separated from each other by a gap as wide as 300 km beneath western anatolia this gap is occupied by slow velocity perturbations that we interpret as hot upwelling asthenosphere the eastern termination of the subducting african lithosphere is located near the transition from central anatolia to the eastern anatolian plateau or arabian eurasian collision front that is underlain by large volumes of hot underplating asthenosphere marked by slow velocity perturbations our tomograms also show fast velocity perturbations at shallow depths beneath northwestern anatolia that sharply terminates towards the south at the north anatolian fault zone nafz the associated velocity contrast across the nafz persists down to a depth of 100 150 km hence our study is the first to investigate and interpret the vertical extent of deformation along this nascent transform plate boundary overall the resolved upper mantle structure of anatolia is directly related with the geology and tectonic features observed at the surface of the anatolian plate and suggest that the segmented nature of the subducted african lithosphere plays an important role in the evolution of anatolia and distribution of its tectonic provinces

empirical relationships between elevation and the stable isotope composition of precipitation and surface waters considerations for studies of paleoelevation change a compilation of 68 studies from throughout many of the world s mountain belts reveals an empirically consistent and linear relationship between change in elevation and change in the isotopic composition of precipitation along altitudinal transects the isotopic composition of precipitation decreases linearly with increasing elevation in most regions of the world except in the himalayas and at elevations 5000 m there are no significant differences in isotopic lapse rates from most regions of the world 0 28 permil 100 m except at the extreme latitudes where isotopic lapse rates are higher given information on past changes in the isotopic composition of precipitation preserved in pedogenic or authigenic minerals this global isotopic lapse rate can be used to place numerical constraints on the topo graphic development of some ancient mountain belts or plateaus there are many complicating factors that can confound interpretation of paleoel evation change based on stable isotopes and many of these are unique to specific mountain belts or time periods relevant to all stable isotope based paleoelevation change studies is the temperature dependent isotope fractionation between a pedo genic or authigenic mineral and the water from which it forms in cases where isotopic proxy minerals are sampled from localities where temperature will change simulta neously with elevation change the apparent change in the isotopic composition of precipitation may be dampened by several permil this suggests that samples taken from the rainshadow side of an emerging orographic barrier may be more likely to preserve isotopic changes resulting from mountain uplift than samples taken from atop a rising mountain range or plateau

response of benthos to stress factors in holocene arctic fjord settings maktak coronation and north pangnirtung fjords baffin island canada maktak coronation and north pangnirtung fjords are situated on cumberland peninsula baffin island canada having a common freshwater source from the penny ice cap bottom photographs were examined to identify epifaunal trails and shallow endobenthic burrow openings exposed on the seafloor surface these were compared to biogenic sedimentary structures revealed through x radiograph images and direct observations of lehigh gravity core samples intermediate and deep tier structures characterize the ichnofabrics of the glaciomarine sediments extensive bioturbation by the shallow tier and epibenthic tracemakers most notably ophiuroid echinoderms brittlestars and other organisms has destroyed much of the primary sedimentary fabric i e lamination resulting in homogenous silty clay sediments the dominant deep tier structure consisting of an open three dimensional boxwork burrow system is the most pervasive biogenic structure observed within the core samples interestingly although proximal distal trends in benthic macrofaunal composition are evident in the bottom photographs ichnofabrics remain relatively constant along the length of the fjords environmental factors influencing the biological community in these modern high latitude fjords differ from conditions described in paleozoic and cenozoic fjord environments an increasing number of recent studies are expanding significantly on the fjord ichnology database and provide the basis for the revision of the currently proposed fjord trace fossil model accommodating the complexity and diversity of fjord settings

ichnology of a glacially influenced continental shelf and slope the late cenozoic gulf of alaska yakataga formation abstract the study of trace fossils in glaciomarine strata is important because of the low preservation potential of fauna but glaciomarine settings have received little attention from ichnologists widespread biological activity is recorded by ichnofossil assemblages in glaciomarine strata of the late cenozoic 6 ma to present yakataga formation alaska glacial sedimentation began in the gulf of alaska in the miocene along a deep water active margin basin dominated by turbidity currents and debris flows later strata record progradation of the continental slope by mass flow processes and the establishment of a broad shelf influenced by repeated glaciation ice rafting of coarse debris changes in water depth and salinity storms earthquakes and high sedimentation rates yakataga formation strata show overall a limited ichnological diversity and low degree of bioturbation in relation to comparable non glacial settings although certain beds are highly bioturbated twenty four ichnotaxa are identified and grouped into nine assemblages characteristic of different depositional settings and substrate types ichnogenera and body fossil evidence shows that polychaetes arthropods molluscs and echinoderms were the dominant infaunal benthic organisms with deposit feeding being the predominant feeding strategy poorly consolidated muddy sediments excluded suspension feeders and limited the development of the skolithos ichnofacies typical of non glacial shelves characterized by clean shifting sand substrates evidence of rapid sedimentation is given by escape structures fugichnia the presence of diplocraterion and by the mass mortality of bivalves firm ground burrows typical of the glossifungites ichnofacies are associated with erosional surfaces boulder pavements and coquinas diminutive feeding traces may reflect salinities lowered by glacial meltwater inputs the downslope transport of food by turbidity currents and mass flows may explain the development of a diverse cruziana ichnofacies in water depths where in non glacial settings the nereites ichnofacies is found an ichnological summary is presented for the late cenozoic gulf of alaska continental margin similar ecological conditions obtain in the modern setting and provide valuable supportive data ichnofacies identified from the yakataga formation are probably widespread in late paleozoic and late cenozoic glacially influenced marine strata

aspects of palyno organic facies analysis comprehensive evaluation of the source rocks and age of some subsurface lower cretaceous core materials in the north western desert egypt abstract the palyno organic facies aspects of the subsurface lower cretaceous core samples are extensively investigated in three wells in the northern part of the western desert of egypt these wells are burg el arab 1 and mamura 1 mersa matruh 1 bax 1 max 1 and mmx 1 respectively the study is based on the palynofacies and organic geochemical analyses the palynofacies examination includes a statistical analysis of the different classes of organic particles by cluster analysis and principal component analysis pca this analysis leads to identify 4 palynofacies types a b c1 and c2 which are dominated by various levels of terrestrial floral materials the paleoenvironmental settings that are attributed to these palynofacies types are the distal suboxic oxic proximal oxic transitional oxic and highly distal oxic the principal component analysis pca differentiates between these palynofacies types mathematically by the biplot of components 1 and 2 the component 1 corresponds to distance from the terrestrial floral sources the identification of quantity type quality and thermal maturity of organic matter is discussed depending on the palynofacies and organic geochemical analyses the thermal maturity is assessed digitally by measuring the rgb color channels in the spore images and their corresponding thermal alteration index tai incorporated with values of tmax these measures are integrated in burial history models with geothermal gradient and depositional history the study reveals that most of the core samples represent generally fair to good enriched sources of gas prone type iii kerogen and less mixed gas oil type ii iii kerogen additionally some occasional high levels of organic conversions are recorded the burial history models indicate that oil expulsion window initiated in the cretaceous the examinations indicate mature oil sources in the alam el bueib formation in mmx 1 well the organic geochemical parameters are correlated versus the component 1 and sum of all components of pca the correlation coefficients r2 pointed to good correlation between the oxygen index oi toc and s2 and lower correlation with hydrogen index hi

late miocene surface uplift of the southern margin of the central anatolian plateau central taurides turkey the timing and pattern of surface uplift of miocene marine sediments capping the southern margin of the central anatolian plateau in southern turkey provide a first order constraint on possible mechanisms of regional uplift nannofossil ostracod and planktic foraminifera biostratigraphy of the basyayla section mut ermenek basin within the mut and koselerli formations suggests a tortonian age for marine sediments unconformably capping basement rocks at 2 km elevation the identification of biozone mmi 12a 7 81 8 35 ma from planktic foraminifera in the upper part of the section provides the tightest constraint on the age which is further limited to 8 35 8 108 ma as a result of the reverse polarity of the collected samples chron 4r 1r or 4r 2r this provides a limiting age for the onset of surface uplift at the margin of one of the world s major orogenic plateaus from which an average uplift rate of 0 24 0 25 mm yr can be calculated subhorizontal beds of the uppermost marine sediments exposed throughout the mut ermenek basin suggest minimal localized deformation with just minor faulting at the basin margin and broad antiformal deformation across the basin this implies that the post 8 ma uplift mechanism must be rooted deep within the crust or in the upper mantle published pn wave velocity data for the region are compatible with topography compensated by asthenosphere across the southern margin of the plateau showing a close match to the highest topography when elevations are filtered with a 100 km wide smoothing window uplift along the southern margin of the central anatolian plateau is also reflected by the pattern of miocene marine sediments capping the margin which form an asymmetric drape fold over the topography these observations together with tomographic evidence for slab steepening and break off beneath the eastern anatolian plateau suggest that at least some of the 2 km of post 8 ma uplift of the southern central anatolian plateau margin is compensated by low density asthenospheric mantle that upwelled following slab break off

the south american retroarc foreland system the development of the bauru basin in the back bulge province abstract the aim of this research is to understand the tectonic setting of the bauru basin this basin in central eastern south america has been classified as intracratonic but the basin fill geometry the involved subsidence mechanisms and the age of the deposits are poorly understood in this work the ranges of the fossil taxa are analyzed and ages are proposed for the lithostratigraphic units isopach maps were used to reconstruct the stratigraphic intervals of the basin fill the stratigraphy of the bauru basin is compared with that of the adjacent basins and the data are integrated with the available information on south american geodynamics the fossil record indicates that sediment accumulated from the cenomanian to early paleocene beginning after the mochica phase of the andean orogeny the basin fill geometry demonstrates migration of the depocenter through time which occurred simultaneously with migration of the andean basin and immediately after the orogenic events of the peruvian phase we propose that the bauru basin is a component of a retroarc foreland system developed during the early stages of the andean evolution and that it was developed in the back bulge province of this system the andean basin constitutes the foredeep depozone of this foreland system including the potosi oriente acre and maranon basins in addition the upper cretaceous of the parecis and solimoes basins were likely also developed in the back bulge province the thickness of the bauru accumulation indicates that other mechanisms might have overlapped the flexural subsidence in this back bulge province

carbonate oxygen isotope paleoaltimetry evaluating the effect of diagenesis on paleoelevation estimates for the tibetan plateau carbonate oxygen isotope paleoaltimetry is based on analysis of the d 18 o value of carbonate precipitated from surface water deciphering the diagenetic history is important for establishing whether particular carbonates are accurate recorders of paleosurface waters which reflect paleoelevation this study provides examples from southern east central and northeastern tibet of approaches aimed at evaluating the diagenetic history of lacustrine micrites and pedogenic carbonates the most desirable technique for avoiding erroneous interpretations related to diagenetic overprinting is to analyze carbonates that are known to be primary such as aragonitic shell material in rocks that do not contain shell material we have compared lacustrine micrites and pedogenic carbonates to diagenetic carbonate phases to determine the effects of diagenesis on the isotopic composition of primary carbonates where the potential effects of diagenesis are subtle or ambiguous we have evaluated the fidelity of the carbonate record from systematic trends in c and o isotopes that agree with other interpretations of paleoenvironment such as high frequency covariance in c and o that corresponds with changes in the mg concentration of carbonates using these strategies we have determined that diagenesis has not affected the isotopic composition of carbonates in the late miocene pliocene thakkhola graben in southern tibet and the oligocene to pliocene linxia basin in northeastern tibet in the case of paleogene basins in east central tibet however ambiguity in data precludes the determination of diagenetic effects d 2004 elsevier b v all rights reserved

integrated palynological organic geochemical and sequence stratigraphic analyses of the middle to upper cenomanian hydrocarbon reservoir source abu roash g member a depositional model in northwestern egypt abstract the current investigation provides further insight into the petroliferous characteristics of the abu roash g member which is regarded as an important rock unit for the egyptian oil industry forty seven samples covering the g member were selected from the bed 14 1 and bed 2 4 wells in the abu gharadig basin and from the abu tunis 1x well in the matruh basin both of which are located in the north western desert an independent dating of the g rocks of bed 2 4 by benthic foraminifera and ostracods in addition to palynological dating suggests a middle late cenomanian age and provides the biochronostratigraphic framework for the sequence stratigraphic analysis analysis of the vertical distribution of particulate organic matter defines three palynofacies types pf pf 1 represents the basal g where shales of the bed wells and calcareous shale of abu tunis 1x were deposited during a relative sea level rise in an outer middle shelf environment that experienced a notable high primary productivity prevailing reducing suboxic anoxic conditions supported preservation of very high amounts of amorphous organic matter aom in pf 1 pf 2 is equated to shales of the middle g of bed 14 1 and bed 2 4 and to calcareous shales and limestone of the upper g in abu tunis 1x pf 2 was deposited during a relative sea level fall in an inner middle shelf setting under better developed suboxic anoxic conditions pf 3 corresponds to the upper g of bed 14 1 and bed 2 4 and represents the shallowest setting where sandy and silty shales were deposited during a pronounced sea level fall in an inner shelf environment the same suboxic anoxic conditions were prevailing during deposition of pf 3 three bioevents were recorded which could be of palaeoecological and or biostratigraphic significance these are senegalinium aenigmaticum dinopterygium cladoides peak dinopterygium cladoides dinopterygium alatum peak and an acme of classopollis brasiliensis sequence stratigraphy of a transect of the four studied sections was carried out to understand the response of the particulate organic matter distribution and depositional system to the sea level changes three third order depositional genetic sequences were recognized and correlated with the global sea level curve kce 2 kce 3 and kce 4 the early highstand systems tract ehst of the genetically related kce 3 in all wells is characterized by relatively rich organic matter where combined remarkably low water circulation and insignificant dilution of organic matter with coarse terrigenous material probably supported good preservation of organic matter spatial distribution of the g rocks shows lateral facies changes this was inferred from sedimentation of an organic poor avg 0 8 toc wt coarse clastic sandy shales facies in the studied area in abu gharadig basin sedimentation changes laterally into a northeast and northwest organic rich finer clastic shale calcareous shales and argillaceous limestone facies in the western matruh basin the robust anoxic conditions and very low dilution of organic matter by terrigenous influx enhanced the organic richness avg 2 4 toc wt of these rocks which resulted in the formation of promising hydrocarbon source rocks thus for a successful hydrocarbon exploration in the north western desert the promising source section of the g member would be associated with shales calcareous shales and argillaceous limestone lithologies its depositional environment is mainly confined to outer middle and inner middle shelf settings that have widespread suboxic anoxic conditions and show ehst pattern in contrast the regressive intervals that are denoted by the lowstand systems tract lst and or the late hst lhst typify the relatively coarse clastics as good quality reservoir rocks that are characterized by poor organic richness due to dilution with terrigenous influx

miocene recent evolution of the western antalya basin and its linkage with the isparta angle eastern mediterranean abstract interpretation of 9500 km of multichannel seismic reflection profiles showed the presence of two major tectonic histories in western antalya basin spanning from the miocene or older to the pliocene quaternary a prominent fold thrust belt affects the miocene succession in the offshore the thrusts swing from a nw se strike with sw vergence in the northeast of the mapped area to a more northerly strike with westerly vergence at the western shelf edge of the deep basin the miocene deformation appears to continue offshore from the westerly directed thrusting seen onshore that characterizes the eastern edge of the isparta angle the contraction is consistent with the counterclockwise miocene rotation of the western side of the isparta angle determined from paleomagnetic studies the thrust belt forms the western extremity of the wider regional aksu kyrenia misis oroclinal culmination the tectonic activity experienced a period of relative quiescence across the western antalya basin during the messinian a major kinematic change occurred in the pliocene when the regional strain was partitioned into three spatially localized tectonic domains an extensional domain confined to the pliocene quaternary unit 1 occupied the northeastern portion of the study area a predominantly extensional domain with a few re activated pre existing miocene contractional structures occupied the southern and central portion of the study area and an extensional and or transtensional domain occupied the continental shelf and slope in the westernmost antalya basin these complexities relate to strike slip motions as the crustal block within the isparta angle moved northwards relative to the blocks to the north

magma generation by slab steepening and breakoff beneath a subduction accretion complex an alternative model for collision related volcanism in eastern anatolia turkey 1 eastern anatolia is regarded as one of the best examples of continental collision represented by a 2 km high plateau it displays shallow and diffuse seismicity indicating that the crust is still being actively deformed perhaps the most striking aspect of eastern anatolia is the volume and compositional variability of collision related volcanic products erupted during the neogene and quaternary time a number of models have been proposed for the genesis of this volcanism in the region however recent geophysical studies have revealed that a mantle lithosphere is almost completely absent beneath a greater portion of the region which makes us question the validity of the previous models in this paper we propose a new model for magma genesis slab steepening and breakoff beneath a large subduction accretion complex this model holds that a northward subducting oceanic lithosphere beneath the eastern anatolia accretionary prism gets steepened and eventually detached from the continental lithosphere of the bitlis poturge massif following the continent accretionary complex collision this brings the asthenospheric mantle in contact with the accretionary complex at shallow depths e g around 50 km resulting in rapid regional uplift and extensive melting which leads to collisional volcanism

paleo oceanographie isotopique des mers post glaciaires du quebec abstract the main hydrological characteristics of the post glacial seas of quebec the gold thwait champlain iberville tyrrell seas and the gulf of laflamme have been investigated by a determination of the isotopic composition 14 c 13 c 18 o of the fauna and sediments of their basins the carbonates are generally depleted in 18 o specially shallow water mollusks which show isotopic compositions as low as pdb 18 o 15 the depletion in heavy isotopes is mainly related to the influx of continental waters particularly glacial meltwater in such basins the isotope geochemistry differs from what is observed in open environments and therefore the standard isotopic paleotemperature technique may not be used directly new data on the isotopic composition of glacial lakes and melting water of the laurentide ice sheet compared with data from present arctic environments have enabled us to calibrate a linear 18 o salinity relationship and to evaluate salinity changes in time and space it is concluded that the present marginal basins of quebec do not show any large differences in either salinity or temperature from the post glacial basins more brackish water has characterized the surficial layers since deglaciation shoaling of the basins due to glacio isostatic rebound later induced local variations in the temperature and salinity the water becoming progressively warmer and more brackish in these basins the geochemistry of carbon is more complex the in situ biological production of co 2 caused large variations in the 13 c content of the carbonates independently of any direct continental influence the observed anomalies in 14 c activity of fossil mollusks are believed to be related to the old water effect and to local influx of dead carbon originating from dissolution by ice meltwater of surrounding carbonate bearing bedrock

palaeoclimate interpretation of stable isotope data from lake sediment archives the isotope composition of authigenic and biogenic carbonates and diatom silica are commonly used as palaeoclimate proxies from lake sediments this article reviews the controls on the isotope composition of lacustrine skeletal and non skeletal deposits and illustrates how stable isotope studies contribute to an understanding of changes in temperature precipitation patterns evaporation and the carbon cycle it highlights the differences in the palaeoclimate potential of a wide range of lakes ranging from open to closed lake basins a large number of the case histories but not all are drawn from studies of temperate lakes from europe large closed lake systems in the tropics and elsewhere lose water predominantly through evaporation and contain sediments with variable and generally high 18o values fluctuations in the isotope composition of authigenic or biogenic minerals are mainly a function of long term changes in the precipitation evaporation ratio in contrast small open lakes which have a degree of through flow typically contain sediments with 18o values that vary by no more than a few these variations are generally ascribed to variations in temperature or the isotope composition of precipitation p from which either an annual or seasonally specific signal can be gained these types of lakes are common in northern europe and at high altitudes the interpretation of isotope data from a lacustrine succession requires a knowledge of the local processes that might control and modify the signal their effects need to be quantified and a robust calibration using the modern lake system is necessary to establish the relationship between the measured signal the isotopic composition of the host waters and climate

surface expression of eastern mediterranean slab dynamics neogene topographic and structural evolution of the southwest margin of the central anatolian plateau turkey 1 the southwest margin of the central anatolian plateau has experienced multiple phases of topographic growth including the formation of localized highs prior to the late miocene that were later affected by wholesale uplift of the plateau margin our new biostratigraphic data limit the age of uplifted marine sediments at the southwest plateau margin at 1 5 km elevation to 7 17 ma and regional lithostratigraphic correlations imply that the age is 6 7 ma single grain ca tims u pb zircon analyses from a reworked ash within the marine sediments yield dates as young as 10 6 ma indicating a maximum age that is consistent with the biostratigraphy our structural measurements within the uplifted region and fault inversion modeling agree with previous findings in surrounding regions with early contraction followed by strike slip and extensional deformation during uplift focal mechanisms from shallow earthquakes show that the extensional phase has continued to the present broad similarities in the change in the tectonic stress regime after 8 ma and the onset of surface uplift after 7 ma imply that deep seated process es caused post 7 ma uplift the geometry of lithospheric slabs beneath the plateau margin pliocene to recent alkaline volcanism and the uplift pattern with accompanying normal faulting point toward slab tearing and localized heating at the base of the lithosphere as a probable mechanism for post 7 ma uplift of the southwest margin considering previous work in the region there appears to be an important link between slab dynamics and surface uplift throughout the anatolian plateau s southern margin

the pliocene quaternary tectonic evolution of the cilicia and adana basins eastern mediterranean special reference to the development of the kozan fault zone abstract a grid of high resolution multi channel seismic reflection profiles allows the detailed mapping of the kozan fault zone in the cilicia and adana basins the zone is delineated by an arcuate zone consisting of several ene wsw and nne ssw striking closely spaced high angle extensional faults which define an 300 km long and 15 20 km wide lazy s shaped structure along the southeastern fringes of the taurus mountain and along the northwestern margins of the cilicia and adana basins in the cilicia basin the zone consists of several high angle faults which exhibit small dip separations on the m reflector and have tip points situated mainly in the lower and middle portion of the pliocene quaternary succession in the adana basin a family of northeast striking and southeast dipping extensional faults occurs along the western and northwestern margin of the basin the faults cut down with relatively steep dip into the 700 ms thick tortonian and older miocene successions multi channel seismic reflection profiles show that three prominent seismic markers divide the uppermost messinian recent successions in the cilicia and adana basins into three subunits the uppermost messinian lower pliocene subunit 1c between the m and a reflectors the upper pliocene subunit 1b between the a and p reflectors and the quaternary subunit 1a between the p reflector and the seafloor prominent delta lobes are identified in the seismic profiles that are correlated with the ancestral goksu river isopach maps constructed using depth converted seismic reflection profiles show clear temporal and spatial variations of the delta lobes of the goksu river during the latest messinian recent the uppermost messinian lower pliocene delta lobe is situated furthest to the northeast whereas the youngest quaternary lobe is situated furthest to the southwest with 20 35 km displacement along a northeast southwest line which suggests a conservative estimate of 0 43 0 75 cm yr sinistral slip for the kozan fault zone

late cretaceous to paleocene oroclinal bending in the central pontides turkey 1 the turkish pontide fold and thrust belt formed since the paleozoic and is an important element in the africa eurasia convergence and the resulting closure of the neo tethys ocean it has a peculiar arc shaped geometry in its central part along the black sea coast which may have resulted from oroclinal bending we have determined the vertical axis rotation history of this area using paleomagnetism on cretaceous to eocene rocks from 47 sites and critically analyzed previously published data we applied the same reliability criteria to all data our results show that late cretaceous sites have clockwise and counterclockwise rotations perpendicular to the structural trend in the central pontides in the eastern pontides they show only local rotations paleocene to eocene rocks in the central and eastern pontides show no rotation we conclude that the central pontide northward arc shaped geometry results from oroclinal bending in latest cretaceous to earliest paleocene times the timing and scale of geological processes that occurred in the region make it likely that orocline formation resulted from neo tethys closure between the pontides and the metamorphic promontory of the anatolide tauride block earlier studies on the southerly located cankiri basin reveal that clockwise and counterclockwise rotations occurred in eocene oligocene times this implies that the entire region underwent continuous deformation from late cretaceous to eocene caused by convergence of the pontides and the anatolide tauride block with a southward moving deformation front deformation was first localized in the northern part of the central pontides until the paleocene resulting in oroclinal bending and from at least eocene times it shifted toward the cankiri basin region

palynofacies and geochemical analysis of the triassic yanchang formation ordos basin implications for hydrocarbon generation potential and the paleoenvironment of continental source rocks abstract the petroliferous basins that have formed in china since the mesozoic are characterized by non marine organic matter input a characteristic that is significantly different from that of marine organic sources the triassic yanchang formation in the ordos basin is a suite of typical intra continental lacustrine sediments that comprise the most important source rocks for the triassic oil reservoirs the yanchang formation is divided into ten subsections from top to bottom chan 1 to chan 10 three borehole successions in the southern ordos basin located in the huachi zhidan and yichuan areas cross the chan 4 5 to chan 10 subsections and have been studied using the palynofacies method combined with organic geochemistry data palynofacies analysis indicates that the sediments are rich in amorphous organic matter aom and phytoclasts the aom content in all of the samples positively correlated with the hydrogen index hi in contrast the transparent ligno cellulosic fragments tlf opaque particles op content are negatively correlated with the hi values additionally the gelified particles gp content has no linear correlation with the geochemistry data based on the quantitative composition of the particulate organic matter three palynofacies types are identified reflecting depositional settings in a distal dysoxic anoxic deep basin a shelf to basin transition zone and a proximal suboxic shelf the palynofacies total organic carbon toc and rock eval data together indicate that type i and ii kerogen are abundant in the d48 and w22 wells in the zhidan and yichuan areas respectively these kerogen types are uncommon in the l94 well in the huachi area which suggests low hydrocarbon generation potential in detail the chan 7 and chan 9 subsections of the three wells contain abundant type i and ii kerogen indicating that these layers are likely the two primary source rocks in the southern ordos basin

role of the westerlies in central asia climate over the cenozoic abstract there remains substantial debate concerning the relative roles of tectonics and of global climate in pacing the evolution of aridity in central asia over the cenozoic tibetan plateau uplift variable monsoonal strength paratethys retreat and reduced moisture transport from the north atlantic have all been hypothesized to drive aridity in central asia distinguishing between these mechanisms requires knowledge of moisture transport pathways to central asia through time presently central asia receives recycled high 18 o moisture that has been transported across eurasia by the westerlies while southern tibet receives low 18 o moisture distilled by passage over the himalaya here we reconstruct the spatial distribution of oxygen isotopes in precipitation since the early eocene using a compilation of 18 o data from 2750 sedimentary carbonate samples across asia the spatial distribution of paleo precipitation 18 o remains remarkably similar through time with low 18 o values in the lee of the himalaya in southern tibet constant high 18 o values in central asia and intermediate values on the central plateau despite independent evidence for substantial changes in both topography and climate through time these results suggest that a long standing topographic feature has continuously blocked southerly moisture and subsequent progressive uplift of the tibetan plateau has had little impact on central asian climate in turn southerly monsoonal moisture has never persistently extended northward of the central plateau as a result the westerlies have remained the dominant moisture source in central asia since at least the early eocene therefore sedimentary aridity indicators in central asia such as loess deposition are controlled by the trans eurasian westerly moisture flux rather than tibetan plateau uplift

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

calcium carbonate preservation patterns in the central north atlantic during the last 150 000 years abstract the dissolution record of the canary and eastern north american basins was examined in 15 cores spanning the last 150 000 years stratigraphic control was based on fluctuations in percent carbonate and 18 0 16 0 dissolution changes were determined based on variations in percent planktonic foraminiferal fragments and benthonic foraminifera results indicate three main dissolution events coincident with 18 0 stages 2 4 and 6 the lysocline apparently shallowed about 300 m in the canary basin at these times there is no simple linear relationship between dissolution intensity and ice volume dissolution was more intense during stage 4 than during stage 2 even though 18 0 records indicate the reverse is true for ice volume also carbonate preservation during the lower part of stage 3 is comparable to stages 1 and 5e a comparison of atlantic pacific carbonate dissolution patterns indicates a tendency for out of phase preservation patterns in 18 0 stages 1 and 2 and an in phase dissolution event during stage 4 the out of phase pattern may partially reflect variations in the production rate of north atlantic deep water the in phase dissolution peak correlates with a major cooling regression transport of organic carbon from transient shallow reservoirs into the deep sea could have contributed to formation of such a pattern however additional evidence from longer atlantic pacific records is needed before the shelf basin model can be more fully evaluated

macrofaunal palaeoecology and stratigraphy in late quaternary shelf sediments off northern norway abstract in a late pleistocene holocene glaciomarine marine sequence a minimum of 115 taxa macrofossils and trace fossils are recognized on the basis of 690 samples from gravity cores from andfjorden nine and malangsdjupet one the biostratigraphy is proposed on the basis of reconstructions of autochthonous macrofaunal assemblages a total of seven zones are defined five in the pleistocene and two in the holocene the ages of which are estimated by radiocarbon datings in ascending order the zones are mixed assemblage zone barren interzone arctinula greenlandica assemblage zone before 14 000 yr b p yoldiella intermedia assemblage zone 14 000 13 000 yr b p bathyarca glacialis assemblage zozne 13 000 yr b p bathyarca glacialis kelliella miliaris interval zone 10 000 ca 7800 yr b p and kelliella miliaris assemblage zone ca 7800 present the bathyarca glacialis zone is divided into three faunules i 13 000 12 000 yr b p ii 12 200 11 100 yr b p and iii 11 100 10 000 yr b p the palaeoecology of the faunal succession is elucidated by means of the sample frequency method two major environmental events have influenced the faunal history the first was the onset of the deglaciation of the thoughs the second the intrusion of the norwegian current bringing warm saline atlantic water into the troughs at 10 000 yr b p the pleistocene fossils demonstrate an arctic macrofaunal succession from a low order stage to a high order equilibrium stage that is in principle identical to that of a modern faunal development in fjords following a disturbance causing anoxia an estimated polychaete mollusc ratio together with changes in sediment influx depositional rates and grain size of substrate indicate the presence of different energy regimes where the inner and outer reaches of andfjorden are compared about 10 000 yr b p a major faunal change took place the previous arctic fauna was replaced by a boreal fauna which developed into the modern fauna the most important factor causing the replacement and renewed faunal succession were probably the rise in temperature and salinity as well as an increase in nutrient supply brought about by the intrusion of the norwegian current a comparison with shallower shelf areas indicates a somewhat different faunal composition in the pleistocene brought about by different depositional environments however a similar major faunal change took place at 10 000 yr b p and there are fewer discrepancies among the holocene faunas regional comparison indicates that some of the phases in the development of the fauna probably are rather local while other have a more regional nature

the rate of taphonomic loss in modern benthic habitats how much of the potentially preservable community is preserved abstract the post mortem fate of shells added by natural mortality to modern death assemblages was studied to determine the importance of taphonomic loss during the initial stages of the formation of a fossil assemblage individuals are added to the living community in pulses usually by larval settlement these input pulses usually are followed by discrete input pulses into the death assemblage the decay of these discrete input pulses in the death assemblage can be used to measure the rate of taphonomic loss as expressed by the half life of a pulse for instance if a species has a half life of 125 days and the input pulse begins with 500 individuals then the number of shells remaining after one half life 125 days is 250 shells at two sites on the texas coast the longest half lives did not exceed one year for any of the 13 species which produced input pulses during the study period little net addition to the death assemblage could be detected in spite of the transitory addition of hundreds of shells as input pulses these rapid decay rates show that death assemblages do not accumulate at the rate at which organisms die some species such as the infaunal bivalve tagelus plebeius did not decay measurably we predict that decay rates drop substantially with depth in the sediment so that individuals which die at depth or are rapidly reworked below the sediment surface have a greater chance of preservation the final composition of death assemblages is probably little related to the actual numerical input from the potentially preservable component of the living community

pyritization of tubes and burrows from late pleistocene continental shelf sediments off north norway four different types of pyritized tubes and three types of pyritized burrow fillings are described from pleistocene glaciomarine sediments in andfjorden northern norway the tubes and burrows probably originated from tubicolous and burrowing polychaetes respectively the decomposition of the organic matter in the tubes and burrows created a reducing micro environment favouring precipitation of pyrite by comparison with holocene tubes from marine sediments in andfjorden and fuglosyfjorden it is seen that pyritization commenced with isolated spherules these spherules with incipient pyrite crystals and framboids were formed mainly on the inner wall of the tube presence of a monosulphide in the holocene fugloyfjorden material suggests that the pyritization process has reached a later phase the final result would be a completely pyritized trace fossil it is shown that single pyrite crystals octahedra generally attain greater size in the burrow fillings than in the tubes the microstructure found in some of the pyritized tubes is interpreted as a reflection of the microstructure in the original wall finally the implications for the depositional environment in pleistocene in andfjorden is investigated with reference to the benthic skeletal macrofaunal assemblage in the sequence the pyritized trace fossils occur frequently in an opportunistic assemblage from a period c 14 000 13 000 yr bp characterized by some oxygen deficiency later 13 000 10 000 yr bp they play a minor role in an established assemblage under improved oxygen conditions

a new approach to stable isotope based paleoaltimetry implications for paleoaltimetry and paleohypsometry of the high himalaya since the late miocene the change in oxygen isotopic composition of precipitation is modeled using equilibrium fractionation during rayleigh distillation linked to the thermodynamics of atmospheric ascent and water vapor condensation the primary controllers of the vertical variation in isotopic composition with elevation are the low elevation temperature and relative humidity as these control the vertical distribution of condensation an empirical fit of precipitation versus model condensation based on alpine stations is derived this fit is represented in the model as the weighted mean composition of condensation within a 1000 m thick air parcel 1500 500 m above the ground surface and is used for all other regions comparison of model versus observed modern precipitation reveals a close fit particularly of more highly elevated sites comparison of modern waters in the himalayas and southern tibet with model predictions particularly as revealed by comparison of observed and predicted hypsometry provides additional support to the validity of the model finally application of this model to estimates of paleo waters in the himalayas and southern tibet reveals that this region had already achieved its present hypsometry by the late miocene about 10 ma ago fl 2001 published by elsevier science b v

late quaternary mediterranean sapropels ii organic geochemistry and palynology of s1 sapropels and associated sediments six s1 sapropel samples from the eastern mediterranean were investigated organic geochemically to study the lateral variation within this organic rich layer five of these samples were also analyzed palynologically in addition some sediment samples from below and overlying the sapropel intervals were investigated for their organic geochemical characteristics organic matter of s1 sapropels is of a mixed marine terrigenous and bacterial origin a trend of relatively increasing amounts of continentally derived organic matter towards more seaward and deeper realms can be observed from both palynological and organic geochemical data this trend is supported to some extent by 13c values of the organic matter the sapropelic intervals deposited on the nile cone are characterized by expanded thicknesses and a diluted organic carbon content due to a higher sedimentation rate the environmental conditions in terms of preservation during sapropel formation over the eastern mediterranean were probably not uniform at site 29 the conditions were favourable for the deposition of sapropel with a higher organic carbon content than at the other locations this might have been caused by better preservation conditions an increasing discharge from the river nile seems to be the driving force for formation of the s1 sapropels based on this assumption a model for sapropel formation is proposed although not all the data could be explained properly by this model most phenomena can be explained

grassland expansion as an instrument of hydrologic change in neogene western north america abstract the evapotranspiration et flux accounts for approximately two thirds of terrestrial precipitation worldwide and in grassland regions et is equivalent in magnitude to precipitation regional contributions to the terrestrial hydrologic budget however have been far from constant in the past as distribution of vegetation changed dramatically the rise of grass dominated ecosystems is one of the most profound paleoecological changes in the cenozoic why then would grassland expansion not feature prominently in the record of neogene hydrologic change despite numerous stable isotope paleoenvironmental studies in neogene north america the contributions of land cover change have been largely ignored we present a compilation of 16 oxygen isotope studies of pedogenic carbonate and smectite from western north america including 4 new records nearly all records from california the basin and range the rocky mountains and the great plains show increases in o 18 on the order of 2 6 in order to assess the role of et in the hydrologic cycle we developed an isotopic water vapor transport model wherein we manipulated et parameters along a specified air mass trajectory grasslands lead to o 18 of precipitation o p 18 values that are up to 5 greater than broadleaf and needleleaf vegetation at inland study sites these results demonstrate that changes in vegetation played a critical role in establishing the modern hydrologic regime in western north america we suggest that this isotopic increase is due to three primary reasons 1 increased evaporation and transpiration fluxes in grassland regions affect water balance 2 shallower rooting depths of grasses lead to the transpiration of soil water enriched in o 18 due to evaporation and 3 grasslands transpire o 18 rich waters during a shorter more punctuated growing season we argue that the observed isotope signals are indicative of a feedback mechanism wherein grasslands not only respond to regional and global climatic trends but also act as a driver of hydrologic change by enhancing seasonality and aridity grasslands transmit hydrologic disturbances downstream engineering climatic conditions favorable for their expansion

the impact of topography on isotopes in precipitation across the central anatolian plateau turkey paleoelevation reconstructions of mountain belts and orogenic plateaus based on stable isotope climate and precipitation records benefit greatly from present day calibrations that relate the fractionation of hydrogen d and oxygen 18o isotopes in precipitation to orographic rainfall here we establish a first order template of d and 18o of modern meteoric waters across the central anatolian plateau cap and its bordering pontic and taurus mountains we identify key regions in the plateau interior and along the plateau margins that have the potential to reliably record topography related paleotemperature and paleoprecipitation changes as recovered from stable isotope paleosol fossil teeth or lipid proxy data based on d and 18o data of more than 480 surface water samples from small catchments and springs we characterize moisture sources affecting the net isotopic budget of precipitation over the cap and analyze how orographic rainout and plateau aridity shape modern patterns of d and 18o in precipitation the taurus mountains bordering the cap to the south act as a major orographic barrier for transport of predominantly winter moisture and exhibit isotopic lapse rates of approximately 20 km for d and 2 9 km for 18o across an elevation range of nearly 3000 m the pontic mountains at the northern margin of the cap force perennial moisture to ascend and condensate revealing lapse rates of 19 km for d and 2 6 km for 18o the difference in the predominant moisture source for the southern and northern margins of the cap north african versus atlantic air masses is manifested in systematic north south differences in near sea level meteoric water compositions of dn s 20 permil and 18on s 3 permil in a swath across the central part of the plateau stable isotope data from the semi arid plateau interior with rainfall as low as 300 to 500 mm yr and mean summer temperatures attaining 23 c provide clear evidence for an evaporative regime that drastically affects surface water and runoff compositions and results in a local meteoric water line for the plateau interior that follows d 4 0 18o 29 3 strongly evaporitic conditions contrast rainfall patterns along the plateau margins including their immediate leeward flanks where d and 18o elevation relationships are reliable predictors of modern topography

time averaging taphonomy and their impact on paleocommunity reconstruction death assemblages in texas bays the death assemblages in upper copano bay and upper laguna madre texas were compared with the living communities as sampled over a two year period in order to determine how taphonomy and time averaging affect paleocommunity reconstruction the living and death assemblages were compared using taxonomic composition numerical abundance diversity biomass and trophic and habitat proportions taxonomic composition particularly adult taxonomic composition and the biomass of the death assemblage more accurately reflect the characteristics of the living community than do numerical abundance and other community attributes based upon numerical abundance such as diversity taxonomic composition and biomass are less modified by taphonomy and time averaging because they are temporally more persistent characteristics of the community community and paleocommunity attributes are not equivalent because the paleocommunity is described using time averaged data ecological theory must be supplanted by paleoecological theory that takes into account this temporal component

pn tomographic imaging of mantle lid velocity and anisotropy at the junction of the arabian eurasian and african plates an edited version of this paper was published by blackwell publishing in geophysical journal international copyright 2004 blackwell publishing see also http www blackwell synergy com doi abs 10 1111 j 1365 246x 2004 02355 x http atlas geo cornell edu middleeastnorthafrica publications al lazki2004 htm

comprehensive source rock evaluation of the kazhdumi formation in the iranian zagros foldbelt and adjacent offshore abstract the kazhdumi formation is regarded as one of the most prolific hydrocarbon sources in the zagros foldbelt and adjacent offshore rock eval pyrolysis data were collected from 2300 rock samples of the kazhdumi formation in 64 wells core and cutting including 37 oil and gas fields and five outcrops 200 vitrinite reflectance measurements were carried out to calibrate and map thermal maturity over the study area palynofacies analyses and thermal history modeling were applied on the wells located in the study area based on the total organic carbon toc map the kazhdumi formation toc values range from 0 to 11 in the central part of dezful embayment its average value is about 5 while average toc value of the kazhdumi formation is lower than 0 5 in qatar gawbandi paleo high hydrogen index hi values represented types ii and iii kerogen for central part of the dezful embayment and qatar gawbandi paleo high respectively t max ranges from 370 to 455 c in the study area the maximum and minimum values for this parameter are recorded in the central dezful embayment and central persian gulf anticlines respectively vitrinite reflectance vr r map also confirms the concluded results of t max data reconstructed burial history and thermal modeling of three wells are also in full agreement with the results of other maturity evidence t max and vr r palynofacies analyses revealed that this formation in the central persian gulf south pars field clearly represents the dominance of terrigenous elements which were resulted from a close proximity to a fluvio deltaic source however towards the northwest amorphous organic matter aom dominates in central dezful embayment indicating a distal dysoxic anoxic environmental condition

temporal variations in lake water temperature paleoenvironmental implications of lake carbonate δ18o and temperature records abstract 18 o and clumped isotope measurements of lacustrine carbonates provide important records of past terrestrial climate and paleoelevation however one of the primary challenges interpreting these data is constraining the relationship between mineral formation temperature and seasonal and mean annual climate we examined surface water temperature records from 88 lakes across the globe to develop transfer functions that relate seasonal water surface temperature to mean annual air temperature these transfer functions provide a means of reconciling proxy measures of water temperature with annual climatic conditions mean annual surface water temperature is related to mean annual air temperature maat 0 0318 t water 2 2 195 t water 12 607 r 2 0 96 independent of lake size with consistently higher mean water temperatures than air n hemisphere spring april june mean lake surface temperatures maat 0 0097 t water 2 1 379 t water 8 227 r 2 0 94 are only slightly warmer than maat for lakes in all climate zones while summer water temperatures jja maat 0 0055 t water 2 1 476 t water 18 915 r 2 0 90 may be 10 20 c warmer than maat for cold climate lakes comparison of carbonate stable isotopic data from sites with different timescales of carbonate formation such as found along latitude or elevation gradients can lead to large over or underestimates of past temperature accurate paleoclimatic interpretation of isotopic proxies or use of temperature proxy constraints i e fossil leaves to estimate lake temperature and calculate water 18 o thus requires appropriate application of water temperature air temperature transfer functions particularly when considering ancient cool high elevation lake systems

retrodeforming the arabia eurasia collision zone age of collision versus magnitude of continental subduction the arabia eurasia collision has been linked to global cooling the slowing of africa mediterranean extension the rifting of the red sea an increase in exhumation and sedimentation on the eurasian plate and the slowing and deformation of the arabian plate collision age estimates range from the late cretaceous to pliocene with most estimates between 35 and 20 ma we assess the consequences of these collision ages on the magnitude and location of continental consumption by compiling all documented shortening within the region and integrating this with plate kinematic reconstructions shortening estimates across the orogen allow for 350 km of neogene upper crustal contraction necessitating collision by 20 ma a 35 ma collision requires additional subduction of 400 600 km of arabian continental crust using the oman ophiolite as an analogue ophiolitic fragments preserved along the zagros suture zone permit 180 km of subduction of the arabian continental margin plus overlying ophiolites wholesale subduction of this more dense continental margin plus ophiolites would reconstruct 400 500 km of postcollisional arabia eurasia convergence consistent with a ca 27 ma initial collision age this younger arabia eurasia collision suggests a noncollisional mechanism for the slowing of africa and associated extension

the crustal structure of the east anatolian plateau turkey from receiver functions an edited version of this paper was published by the american geophysical union agu copyright 2003 agu see also http www agu org pubs crossref 2003 2003gl018192 shtml http atlas geo cornell edu turkey publications zor et al 2003 htm

east anatolian high plateau as a mantle supported north south shortened domal structure an edited version of this paper was published by the american geophysical union agu copyright 2003 agu see also http www agu org pubs crossref 2003 2003gl017858 shtml http atlas geo cornell edu turkey publications sengor et al 2003 htm

environmental assessment from the sedimentary record of high latitude fiords the sedimentary record of fiords at high latitude where global change may be occurring earliest and will be greatest has the potential for assessment of environmental change at both low resolution the scale of millennia and high resolution decadal to less than daily unlike the lacustrine record which has been used very successfully in these studies the sedimentary processes and thus the sedimentary deposits of fiords differ 1 in the role of salt water in inhibiting mixing and promoting flocculation and through the role of sea ice 2 in the exchange of mass and energy with the much larger ocean beyond and 3 in the role of benthic biota in the sedimentary environment the work reviewed in this paper shows that fiord sediments are being used to assess sedimentary and oceanic processes as well as glacial periglacial and geomorphic history and that they are important proxies for long term climate and hydrology recommendations for advancing this work include long term monitoring of conditions in fiords and their drainage basins so that the transfer relations can be more solidly constructed from the proxy of fiord sediment integration of results from fiords in opposite polar latitudes and among proxies especially from lacustrine and ice core records will produce valuable insights assessment of the range of conditions in fiords from the most polar to temperate regions is important to building models of their processes and understanding of the paleoenvironmental signals that can be interpreted from each type

the cenomanian turonian oceanic anoxic event in the razzak field north western desert egypt source rock potential and paleoenvironmental association abstract the western desert of egypt is one of the world s most prolific jurassic and cretaceous hydrocarbon provinces it is one of many basins that experienced organic rich sedimentation during the late cenomanian early turonian referred to as oceanic anoxic event 2 oae2 the razzak 7 oil well in the razzak field in the northern part of the western desert encountered the upper cretaceous abu roash formation this study analyzed 23 samples from the upper g f and lower e members of the abu roash formation for palynomorphs particulate organic matter total organic carbon toc and 13corg in order to identify the oae2 determine hydrocarbon source rock potential and interpret the depositional environment the studied samples are generally poor in palynomorphs but show a marked biofacies change between the lower e member and the rest of the studied samples palynofacies analysis kerogen quality and quantity indicates the presence of oil and gas prone materials kerogen types i and ii iii respectively and implies reducing marine paleoenvironmental conditions detailed carbon stable isotopic and organic carbon analyses indicate that fluctuations in the 13corg profile across the abu roash upper g f and lower e members correspond well with changes in toc values a positive 13corg excursion 2 01 believed to mark the short term global oae2 was identified within the organic rich shaly limestone in the basal part of the abu roash f member this excursion also coincides with the peak toc measurement 24 61 wt in the samples

extreme freshwater release during the late paleozoic gondwana deglaciation and its impact on coastal ecosystems abstractstrata in the paganzo tarija and parana basins of argentina and brazil provideevidence for reconstructing the effects of late paleozoic glacial retreat the depositionalenvironment of the transgressive and early highstand ne grained deposits has been con troversial with interpretations ranging from normal marine shelves to estuaries to lakes whereas their counterparts from shallow marine settings not in uenced by glaciation hostdiverse fully marine ichnofaunas these ne grained postglacial deposits are dominatedby nonspecialized grazing trails simple feeding traces arthropod trackways and shtrails they are typical of freshwater environments and represent examples of the mermia and scoyenia ichnofacies however the local presence of acritarchs indicates sporadicmarine in uence these observations suggest a new interpretation that freshwater con ditions in fjordlike settings across south america were widespread because gondwananbasins were overwhelmed by strong meltwater discharge issuing from melting of the con tinental ice masses keywords

rapid late miocene surface uplift of the central anatolian plateau margin abstract the central anatolian plateau cap turkey is bordered to its south by a steep mountain belt that emerged 8 7 ma ago from the mediterranean sea knowledge of the onset duration and rate of surface uplift and orographic barrier formation along the plateau margin is crucial for understanding the geodynamic drivers of plateau uplift we present a new comprehensive data set that includes 12 40ar 39ar ages and lacustrine carbonate 18 o data n 637 from 13 sections in upper oligocene to pliocene continental basins of the cap interior we aim at documenting the development of a rain shadow and therefore the surface uplift history of the cap and its southern margin tauride mts in the rain shadow of the tauride mts we observe a gradual 3 9 decrease of 18 o values of lacustrine carbonate between 11 and 5 ma that we interpret to originate from a similar change in 18 o values of precipitation owing to the late miocene development of an orographic barrier our stable isotope paleoaltimetry data show that by 5 ma the southern cap margin had reached similar to present elevations of 2 km surface uplift was coeval with ignimbritic magmatism forearc shortening and distributed compression we suggest that the removal of lithospheric mantle below anatolia led to surface uplift of the cap interior which was followed by surface uplift of the southern cap margin due to crustal thickening as a result of northward subduction of the african plate below central anatolia

do foraminifera mirror diversity and distribution patterns of macrobenthic fauna in an arctic glacial fjord abstract this paper compares the distribution and diversity patterns of benthic foraminifera all taxa and only calcareous forms and macrozoobenthos in an arctic glacial fjord the samples were collected at 22 stations located in hornsund west spitsbergen the activity of tidal glaciers located in the inner basins causes steep environmental gradients of turbidity organic matter supply and sediment stability clear differences in density diversity and species composition were documented for both foraminifera and macrofauna between the groups of stations located in three zones along a gradient of increasing tidal glacier impact the assemblages of both benthic compartments in the glacial bay were dominated by small opportunistic infaunal species i e cassidulina reinforme for foraminifera and cirratulid polychaetes for macrofauna which occurred throughout the fjord but showed an increase in density and or dominance when approaching the glaciers a parallel decreasing pattern from the central basin to the inner glacial bay was noted with regard to species richness and faunal density of both groups macrofaunal evenness decreased close to glaciers but this was not observed in the foraminiferal assemblages the distribution patterns of calcareous foraminifera were correlated p 0 001 both with those of all foraminifera agglutinated and calcareous taxa and with macrofauna with the spearman s rank correlation between the respective bray curtis similarity matrices ranging from 0 94 to 0 99 total foraminifera and from 0 37 to 0 67 macrofauna respectively species richness expressed as the number of species per sample and diversity expressed by the shannon wienner index of foraminifera and macrofauna were also significantly correlated pearson correlation r 0 79 r2 0 62 p

multi phased uplift of the southern margin of the central anatolian plateau turkey a record of tectonic and upper mantle processes abstract uplifted neogene marine sediments and quaternary fluvial terraces in the mut basin southern turkey reveal a detailed history of surface uplift along the southern margin of the central anatolian plateau from the late miocene to the present new surface exposure ages 10be 26al and 21ne of gravels capping fluvial strath terraces located between 28 and 135 m above the goksu river in the mut basin yield ages ranging from ca 25 to 130 ka corresponding to an average incision rate of 0 52 to 0 67 mm yr published biostratigraphic data combined with new interpretations of the fossil assemblages from uplifted marine sediments reveal average uplift rates of 0 25 to 0 37 mm yr since late miocene time starting between 8 and 5 45 ma and 0 72 to 0 74 mm yr after 1 66 to 1 62 ma together with the terrace abandonment ages the data imply 0 6 to 0 7 mm yr uplift rates from 1 6 ma to the present the different post late miocene and post 1 6 ma uplift rates can imply increasing uplift rates through time or multi phased uplift with slow uplift or subsidence in between longitudinal profiles of rivers in the upper catchment of the mut and ermenek basins show no apparent lithologic or fault control on some knickpoints that occur at 1 2 to 1 5 km elevation implying a transient response to a change in uplift rates projections of graded upper relict channel segments to the modern outlet together with constraints from uplifted marine sediments show that a slower incision uplift rate of 0 1 to 0 2 mm yr preceded the 0 7 mm yr uplift rate the river morphology and profile projections therefore reflect multi phased uplift of the plateau margin rather than steadily increasing uplift rates multi phased uplift can be explained by lithospheric slab break off and possibly also the arrival of the eratosthenes seamount at the collision zone south of cyprus

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

palaeoenvironmental analysis of a miocene basin in the high taurus mountains southern turkey and its palaeogeographical and structural significance determination of the relationships between the southern marine dominated miocene basins of south central turkey and their continental hinterland in southern turkey has traditionally been frustrated by the apparent absence of basin remnants within the taurus mountains the dikme basin which seems to be an enclave of basin remnants within the aladag mountains eastern taurides consists mainly of coarse grained continental sediments of various facies these mostly early middle miocene sediments were studied to determine the depositional environments and the factors controlling the basin formation and basin fill architecture to attempt to close the information gap between the adana basin to the south and central anatolian miocene further to the north a generally southwest flowing axial fluvial system and interfingering coarse grained marginal alluvial clastics derived from northwest and southeast were identified the marginal facies to the northwest is bounded by a n 55 e running structural lineament that starts from the ecemis fault zone and in digital elevation models extends toward the north of the study area along this lineament miocene sediments onlap steep fault line escarpments certain miocene levels are tectonically disrupted and an intraformational unconformity and boulder conglomerates are also well developed in the miocene sequence the southeast boundary is similarly defined by a ne trending fault that periodically elevated the adjacent tufanbeyli autochthon producing coarse clastics from this area this boundary fault also induced fining upwards vertical patterns and synsedimentary deformation in the marginal facies additionally the central part of the basin exhibits a distinct fault defined morphology characterized by small scale tens of metres to 150 m high valley and sill topography a thin marine interval was also encountered in the southernmost part of the basin indicating that the clastic system originating around this area debouched into a miocene sea situated further to the south the proposed palaeogeography and basin fill model suggests that the dikme basin and similar miocene remnants all controlled mainly by a northeast running extensional or transtensional fault system may have been parts of the terrestrial hinterland that supplied sediment to rapidly subsiding marine areas further south such as the adana basin

palynological palynofacies paleoenvironmental and organic geochemical studies on the upper cretaceous succession of the gptsw 7 well north western desert egypt abstract the present study of the abu roash and bahariya formations in well gptsw 7 refines our understanding of the subsurface cretaceous of the north western desert of egypt our investigations are based on the palynological analyses of 71 cuttings samples of which 24 have also been analyzed for geochemistry in addition to 3 sidewall cores analyzed for vitrinite reflectance r o four palynological zones and three subzones in addition to a poorly fossiliferous interval ranging in age from coniacian santonian to early cenomanian are proposed these include a poorly fossiliferous interval coniacian santonian dinogymnium vozzhennikovae interval zone late to middle turonian ephedripites ambiguus ephedripites multicostatus foveotricolpites giganteus foveotricolpites gigantoreticultus assemblage zone early turonian classopollis brasiliensis interval zone late to middle cenomanian and afropollis jardinus interval zone early cenomanian the succeeding subzones are afropollis kahramanensis interval subzone elaterosporites klaszii interval subzone and cretacaeiporites densimurus interval subzone all of early cenomanian age total organic carbon toc and rock eval pyrolysis and palynofacies analyses indicate that the bahariya formation and the abu roash g member are primarily of kerogen iii type and hence gas prone suggesting a strong influence of hydrogen enriched organic matter the abu roash a c e members may also be gas prone type iii kerogen and appear to contain highly oxidized terrestrial organic matter in contrast the abu roash f member has very high toc and hi values and contains a very high proportion of amorphous organic matter aom indicating a highly oil prone facies while this finding is not unexpected for anoxic black shale it contrasts with earlier studies that suggest a gas prone nature r o measurements show that the bahariya formation represents an immature early genesis dry gas phase this is also true for all investigated samples from the abu roash and bahariya formations based on their low thermal alteration index tai quantitative and qualitative analyses of both the palynoflora and palynofacies show that the abu roash a and c members b is missing both of coniacian santonian age represent oxic proximal and distal shelf environment the abu roash d and e members dated as turonian represent oxic proximal shelf whereas the cenomanian abu roash f member was deposited in a distal suboxic anoxic basin the cenomanian abu roash g member and the bahariya formation were deposited in a shallow marine and shallow marine to fluvio deltaic setting respectively the senonian palmae province is recognized in the palynoflora by the presence of proteacidites auriculiidites reticulatus ariadnaesporites gabonisporis vigourouxii on the other hand the albian cenomanian elaterates province is characterized by the presence of steevesipollenites gnetaceaepollenites elaterocolpites elaterosporites elateroplicites senegalosporites sofrepites afropollis and cretacaeiporites

animal sediment relationships on a subarctic intertidal flat pangnirtung fiord baffin island canada abstract broad boulder strewn intertidal flats border the shores of pangnirtung fiord baffin island these intertidal flats support a benthic biota dominated by bivalves sedentary polychaetes and phaeophycean algae the assemblage of organisms inhabits a variety of substrates ranging from muddy sand through gravelly sand and boulders six depositional environments defined on the basis of sediment texture primary sedimentary structures and their associated macrofauna and ichnofauna are recognized on pangnirtung fiord intertidal flats proceeding seaward these are beaches sand bars muddy sand flats macoma balthica sand flats arenicola marina sand flats and boulder barricades such sediments in outcrop may differ only subtly from their equivalents in other latitudes modern biogenic structures provide essential information for environmental reconstruction in arctic marginal marine environments their use in sedimentology is enhanced by the low preservation potential of primary sedimentary structures and shell material as a result of disturbance by drift ice bioturbation and dissolution the ichnofauna exhibiting the greatest preservation potential is characterized by vertical domichnia of bivalves and polychaetes and resembles the ichnofauna recorded on the bay of fundy intertidal flats

regional impact of an elevated heat source the zagros plateau of iran the authors propose that a heat driven circulation from the zagros plateau has a significant impact on the climate of the middle east plain mep especially summertime winds air temperature and aridity this proposal is examined in numerical experiments with a regional climate model simulations in which the zagros plateau was assigned a highly reflective snowlike albedo neutralized the heat driven circulation and produced an extra summertime warming of 1 2 c in the mep measured relative to a control simulation and to the records of the ncep ncar reanalysis project this effect was largest in midsummer when heating on the plateau was greatest additionally simulations with high albedo on the zagros showed reduced subsidence and enhanced precipitation in the mep these sensitivities are interesting because the zagros plateau lies downwind of the mep analysis of model results indicates that the sensitivity of the upwind subsidence region to zagros albedo can be understood as a linear atmospheric response to plateau heating communicated upwind by a steady heat driven circulation that influences the thermodynamic balance of the atmosphere this regional phenomenon adds to the large scale subsidence patterns established by the hadley circulation and the asian monsoon observed patterns of vertical motion in the middle east then are a combined product of zagros induced subsidence and hemispheric scale circulations

source to sink the development of the latest messinian to pliocene quaternary cilicia and adana basins and their linkages with the onland mut basin eastern mediterranean abstract multi channel seismic reflection profiles show that there is a thick northeast southwest elongated lobe of uppermost messinian and pliocene quaternary sediments across the cilicia basin extending into the onland adana basin three prominent seismic markers divide this succession into three subunits detailed isopach maps constructed using a dense grid of depth converted seismic reflection profiles show that these three subunits display distinctive sediment distribution patterns that can be confidently related to eastward deposition from the goksu river to the west subsidence rates calculated at 95 locations within the cilicia and adana basins using osxbackstrip show that the central axis of the cilicia adana basin complex is subsiding at a rate of 10 20 mm per year the subsidence rates sharply decrease both toward the misis kyrenia fault zone in the south and east and the turkish continental margin in the west and north to values of 0 10 0 15 mm per year subsidence rates were 0 10 0 20 mm per year during the deposition of the middle and upper pliocene but decreased to 0 05 mm per year sedimentation rates calculated for the three subunits compared to the present day rate of sedimentation by the goksu river clearly show that sedimentation in the early pliocene interval was significantly greater than it is today the data show that the dramatic subsidence of the cilicia basin 2000 m since the messinian occurred in synchroneity with the rise of the mut basin nestled over the central taurus mountains the adjacency of the mut and cilicia basins suggests that there must be a common local cause for the uplift of the mut basin and the subsidence of the cilicia basin we believe that the rise of the central taurus mountains represents an additional load on the underlying asthenosphere the isostatic response of which would have caused the subsidence in the cilicia basin

calcareous nannofossil and dinoflagellate stratigraphy across the cretaceous tertiary boundary at hor hahar israel in israel the cretaceous tertiary k t boundary at hor hahar occurs within the interval from the top of the ghareb formation maastrichtian to just below the horizon of dark marl and clay within the overlying taqiye formation paleocene the studied interval contains all the calcareous nannofossil zones micula prinsii latest maastrichtian markalius inversus np1 earliest paleocene andcruciplacolithus tenuis np2 early paleocene they correlate in sequence with theabathomphalus mayaroensis p0 p1a p1b and p1c planktic foraminiferal zones the palynological assemblages consist mainly of dinocysts with only few pollen grains and spores these assemblages are used to interpret five stratigraphic phases of environmental change across the k t boundary in the hor hahar section in the latest maastrichtian there is an overwhelming dominance of the nannofossilmicula decussata which probably reflects environmental stress preceding the terminal cretaceous mass extinction a nearshore marine environment at the boundary is suggested by the increase in number of specimens of the dinocystcyclonephelium and by the predominance of terrigenous organic matter sediment there followed two episodes of transgression and regression the calcareous cyst producing dinoflagellatethoracosphaera futterer 1976 becomes dominant in two episodes at the boundary and approximately one meter above it it alternates in abundance with the organic walled dinoflagellates which suggests that different environmental parameters were operating for each group maastrichtian dinocysts decline in abundance toward the k t boundary they reach greatest abundance and species diversity at the same strata where foraminiferids recover after their mass extinction at the boundary calcareous nannofossils recover only later in the early paleocene changes in 13c and total organic carbon as as well as dinocyst and nannofossil composition indicate an episode of strong ecological stress about one meter above the boundary

δ18o and δd of streamwaters across the himalaya and tibetan plateau implications for moisture sources and paleoelevation reconstructions abstract this study presents new 18o and d data from 191 streams across the himalaya and tibetan plateau to better constrain the spatial variability of stable isotopes in modern precipitation over this region moisture penetrating into the southeastern tibetan plateau is predominantly derived from monsoonal airmasses originating from the bay of bengal and transported into the eastern himalayan syntaxis along the brahmaputra river progressive rainout during orographic lifting and cooling results in clear relationships between 18o and d and catchment hypsometric elevation on the plateau margin however monsoonal derived moisture is progressively mixed with central asian airmasses in more western and northern parts of the tibetan plateau as a result predicted isotope elevation relationships that are based on empirical lapse rates or thermodynamic models of the isotopic evolution of an airmass produce large 1 3 km misfits between measured and predicted catchment elevations for much of the tibetan plateau including some areas directly north of the central himalayan crest this suggests that changes in the 18o or d of paleoprecipitation on the central and southwestern tibetan plateau may reflect surface uplift along moisture transport pathways or changes in the penetration of monsoonally derived moisture rather than regional surface uplift histories

early holocene deglaciation of expedition and strand fiords canadian high arctic terrestrial and marine records provide the first reconstruction of past glacial events on west central axel heiberg island lateral moraines along expedition fiord define an early holocene ice margin when a trunk glacier occupied the inner half of the fiord limited sediment accumulation in the outer fiord 8 4 ka bp principally by calving of an unstable ice front to a position well upvalley of the present ice limit rapid deglaciation is evidenced by i an absence of ice marginal landforms and related marine biofacies ii a scarcity of raised marine sediments and iii exceptionally thin sediments 5 20 m in the inner fiord a transition from a hiatella arctica mya truncata macrofossil assemblage to an astarte borealis mya truncata assemblage reflects a change from moderate to low energy depositional environments at the fiord head by 7 9 ka bp the extensive ice advance into expedition fi

source rock potential and depositional environment of upper cretaceous sedimentary rocks abu gharadig basin western desert egypt an integrated palynological organic and inorganic geochemical study abstract the abu gharadig basin in the northern part of the western desert egypt is among the most important petroleum provinces in egypt here cenomanian to santonian rocks of bahariya formation and abu roash a g members from the gpt 3 well were investigated for their depositional environment kerogen quality petroleum generation potential and thermal maturity by geochemical petrological and palynological methods the sediments of the bahariya and abu roash formations excluding the abu roash f member represent variable shallow marine environments with poor preservation of marine organic matter whereas there is an excellent preservation in the abu roash f member the basal part of this member is characterized by anoxic carbonate rich depositional conditions high toc values up to 7 high hi up to 700 mghc gtoc and liptinite dominated organic matter depletion of iron leads to sulfur incorporation into organic matter which is reflected in high thiophene benzene ratios above sediments are enriched in terrestrial elements fe ti as well as k and mn this pattern and the occurrence of the fresh brackish water algae botryococcus suggests a regression phase during deposition the upper part of the abu roash f member is again characterized by fully marine suboxic conditions and a lower thiophene benzene ratio the source rock section demonstrates lower thermal maturity compared to the above and below sections based on all microscopic pyrolysis and biomarker data this indicates thermal maturity retardation suppression most likely due to a different organic facies and early diagenetic transformation of kerogen as indicated by the geochemical and palynological data the source rock heterogeneity indicates a relatively shallow marine environment where the changes in bottom water conditions are very sensitive to sea level fluctuations residual oil characterization reveals two reservoir compartments which are in the abu roash d and c members the abu roash f source rocks are compared with time equivalent sediments in the tarfaya basin in morocco which represent more distal settings the more proximal group a is characterized by s fe ratios between 0 57 and 0 67 indicating suboxic conditions it has toc and hi values not exceeding 4 and 600 mghc gtoc respectively at variable caco3 contents the more distal tarfaya sediments group b have higher toc and hi as well as high organic sulfur contents group a is higher in terrigenous element concentrations the tmax of immature source rocks ranges from 410 to 415 c in organic sulfur rich samples and from 420 to 430 c in organic sulfur poor samples revealing an important impact of organic facies on maturity parameters furthermore there is an inverse relationship between s fe and al2o3 toc which might become an important tool in paleoenvironmental reconstructions as well as petroleum source rock studies

an origin for laminated glacimarine sediments through sea ice build up and suppressed iceberg rafting laminated glacimarine sediments are observed in visual core logs and x radiographs from scoresby sund and nansen fjord east greenland they are mostly underlain and overlain by massive or stratified glacimarine diamicton dmm or dms which is a product of iceberg delivery of heterogeneous debris and in scoresby sund reworking by deep drafted iceberg keels the laminated sediments are ams radiocarbon dated to two cold periods since the last late weichselian deglaciation the younger dryas stadial milne land stadial in east greenland and the little ice age during cold climatic events multiyear shorefast sea ice sikussak formed in these fjords and trapped the icebergs fine grained laminated muds fl were deposited in scoresby sund when the flux of icebergs was suppressed but turbid meltwater continued to provide some sediment flux to the fjord systems varying through time to produce laminations in nansen fjord thinner and often massive mud layers fm resulted from shorter intervals of sea ice cover with no ice rafting stratified diamicton layers dms which alternate with mud deposition to produce a laminated unit probably represent intervening times of more open conditions with iceberg rafting in scoresby sund foraminifera are either absent from the laminated unit or begin to appear towards the end of its deposition the absence of both benthic and planktonic foraminifera also suggests that multiyear sea ice was covering the core sites there is no evidence of macrofaunal activity and bioturbation is absent from the laminated sediments satellite data show that multiyear shorefast sea ice is present in several areas of the high arctic today and this traps icebergs calved from interior ice cap drainage basins thus the process of laminated glacimarine sediment formation is likely to be applicable to a number of areas of the modern and quaternary arctic