factors controlling the burial of organic carbon in laminated and bioturbated sediments off nw mexico implications for hydrocarbon preservation factors controlling the burial of organic carbon oc in late quaternary sediments on the nw mexican continental margin are assessed using a suite of box and piston cores strategically located on the shelf slope rise with respect to the intense oxygen minimum in this region an oc concentration maximum occurs on the mid slope below the core of an intense water column o2 minimum due to current winnowing on the outer shelf the preferential accumulation of organic matter in fine grained deposits and the offshore decrease in the settling flux of organic detritus the organic matter at all water depths is overwhelmingly marine hydrogen indices hi are higher on the slope 300 mg hc g toc than on the shelf 300 mg hc g toc where current winnowing has promoted organic matter degradation but there is no difference in hi in slope sediments accumulating under well oxygenated and o2 deficient conditions the degree of winnowing appears to be the primary factor affecting the preservational quality of organic matter deposited on this margin rates of accumulation of oc and opal are all higher in the interglacial intervals when compared with the glacial deposits over the last 140 000 yr however matrix corrected hi values in the mid and lower slope cores are invariant and are similar to values in the laminated intervals from the oxygen minimum site thus cyclic changes in organic carbon accumulation on this margin have been controlled by production variations rather than differential preservation hi values in late quaternary sediments from several continental margins including nw mexico and euxinic basins correspond to type ii kerogen irrespective of bottom water o2 concentrations therefore the preservation of oil prone kerogen in productive margin settings does not appear to be restricted to sediments deposited under conditions of low bottom water o2 concentrations as envisioned in models of petroleum source rock deposition

a late jurassic early cretaceous metamorphic core complex strandja massif nw turkey in the eastern part of the strandja massif constituting the east end of the rhodope massif the amphibolite facies basement rocks intruded by permian metagranites are juxtaposed against the greenschist facies cover metasediments of triassic middle jurassic protolith age the distinct metamorphic break between the basement and cover rocks requires a missing metamorphic section the boundary between the two groups of rocks is a ductile to brittle extensional shear zone with kinematic indicators exhibiting a top to the e ne shear sense footwall rocks are cut by weakly metamorphosed and foliated granite bodies which are clearly distinguished from the permian metagranites by their degree of deformation cross cutting relations and syn tectonic kinematic character also hangingwall rocks were intruded by unmetamorphosed and weakly foliated leucogranites 40ar 39ar data indicate that the ductile deformation from 156 5 to 143 2 ma middle oxfordian earliest berriasian developed during the syn tectonic plutonism in the footwall deformation and gradual slower cooling exhumation survived until to 123 ma barremian the mylonitic and brittle deformation in the detachment zone developed during oxfordian earliest berriasian time 155 7 142 6 ma and early valanginian aptian time 136 118 7 ma respectively our new field mapping and first 40ar 39ar ages demonstrate the existence of an extensional core complex of late jurassic early cretaceous age not previously described in the rhodope strandja massifs

increased productivity in the eastern equatorial pacific during the last glacial maximum 19 000 to 14 000 yr b p a widespread pronounced enrichment in the organic carbon content occurs at shallow depths in eastern equatorial pacific sediments the c org peak is shown by radiocarbon dating to be temporally coincident with the last stage 2 or wisconsin glacial maximum in contrast caco 3 profiles show less overall variation which appears to be partly a function of the location of the sediments relative to the lysocline consideration of the iodine c org ratio in the sediments rules out enhanced preservation as a cause of the stage 2 organic carbon enrichment the peak instead must have resulted from a significant increase in productivity during the glacial maximum

organic geochemical proxies of paleoceanographic paleolimnologic and paleoclimatic processes abstract organic matter constitutes a minor fraction of marine and freshwater sediments yet its important contribution to the sedimentary record can be used to reconstruct marine and continental paleoenvironments the organic matter content of sediments is the residue of past biota the amounts and types of organic matter present in sediments consequently reflect environmental conditions that impacted ecosystems at different past times general sources of the organic matter are inferred from bulk properties such as elemental compositions carbon and nitrogen stable isotope ratios rock eval pyrolysis data and organic petrography details of organic matter origins are refined by analyses of biomarker molecular compositions source changes are proxies for fluctuations in sea level oceanic surface currents and continental climates algal paleoproductivity rates are indicated by organic carbon mass accumulation rates and carbon and nitrogen stable isotopic compositions these parameters record past availability of nutrients and therefore are proxies of surface mixing in the oceans and amount of land runoff to lakes sea surface paleotemperatures are recorded by the number of carbon carbon double bonds in lipid biomarkers produced by marine algae larger proportions of the double bonds are proxies for the cooler surface waters that accompanied periods of global glaciation and intervals of enhanced upwelling the 13c and d values of plant organic matter record past concentrations of carbon dioxide in the atmosphere and changes in delivery of atmospheric moisture respectively diagenesis which causes the concentration and composition of organic matter in sedimentary settings to differ from those of the original biologically synthesized materials can bias organic geochemical paleoenvironmental records the magnitude of this potential source of misinformation must always be considered and evaluated comparison of multiple organic geochemical proxies of past conditions helps to compensate for the effects of diagenetic alterations and thereby to improve interpretations of paleoenvironmental change

late pleistocene holocene paleoproductivity circulation in the japan sea sea level control on δ13c and δ15n records of sediment organic material organic carbon and total nitrogen contents and their isotope ratios were determined in a sediment core recovered from the japan sea to investigate the record of organic matter resources and paleoproductivity in a semi enclosed marginal sea 13c 15n relationships show that the composition of sediment organic material resulted from the mixing of terrestrial and marine organic matter we found synchronous down core variations in the carbon and nitrogen isotope records which are explained by surface productivity control on the composition of sediment organic material moreover these variations are related to sea level changes which caused variable surface water inflows last glacial sea level lowering increased continental run off leading to water column stratification in the japan sea anaerobic conditions due to basin water stagnation led to the deposition of laminated clay sediment organic c n and isotope ratios fluctuated markedly in the transitional stage from aerobic to anaerobic conditions the fluctuations are likely to have been caused by large scale oscillations in sea level just before the last glacial maximum

surficial geology of the continental shelf northwestern vancouver island abstract the vancouver island continental margin lies along the convergent boundary between the explorer and juan de fuca plates and the america plate off northwestern vancouver island this tectonic regime is manifested in major thrust faults and folds which dislocate volcanic and sedimentary rocks of tertiary age beneath a relatively undeformed wedge of late neogene mudstones surficial sedimentation reflects both the tectonic and high latitude settings of the area predominance of lithic arenites and graywackes high wave and current energy restricting modern sedimentation to the outer shelf deeper than 110 m and resulting in the formation of large oscillation bedforms to depths of 100 110 m trapping of terrigenous sediments in fjords leading to low sediment accumulation rates on the shelf which in turn favor the formation of abundant glauconie gravel lags and extensive areas of biogenic sediments dominated by molluscs and bryozoa and the presence of pleistocene glaciomarine sandy muds and muddy sands beneath the mid and outer shelf

sea surface temperature changes in the southern california borderlands during the last glacial interglacial cycle a variety of evidence suggests that average sea surface temperatures ssts during the last glacial maximum in the california borderlands region were significantly colder than during the holocene planktonic foraminiferal 18o evidence and average sst estimates derived by the modern analog technique indicate that temperatures were 6 10 c cooler during the last glacial relative to the present the glacial plankton assemblage is dominated by the planktonic foraminifer neogloboquadrina pachyderma sinistral coiling and the coccolith coccolithus pelagicus both of which are currently restricted to subpolar regions of the north pacific the glacial interglacial average sst change determined in this study is considerably larger than the 2 c change estimated by climate long range investigation mapping and prediction climap 1981 we propose that a strengthened california current flow was associated with the advance of subpolar surface waters into the borderlands region during the last glacial

glacial interglacial variability in denitrification in the world s oceans causes and consequences the late quaternary history of water column denitrifcation of the eastern pacific margins and the arabian sea is reconstructed using sedimentary 15n measurements the 15n values in six piston cores raised from these regions show remarkably similar cyclic variations being heavy 9 10 5 during the interglacials and 2 3 lighter during the glacials this implies that denitrification in these regions decreased substantially during the glacial periods the glacial decline in denitrification is attributed to reduced upwelling and flux of organic material through the oxygen minimum zone since water column denitrification in these areas accounts for about half of the fixed nitrogen loss in the modern ocean the inferred decrease in denitrification should have increased the oceanic nitrate inventory during glacial periods because nitrate is a limiting nutrient oceanic productivity and attendant changes in co2 may therefore have been modulated on glacial interglacial timescales by variations in the oceanic no3 content

a case of post depositional aerobic degradation of terrestrial organic matter in turbidite deposits from the madeira abyssal plain abstract a set of oxidized and unoxidized sediment intervals from the f turbidite identified in two piston cores from the madeira abyssal plain map was analyzed for calcium carbonate total organic carbon toc total nitrogen tn stable carbon composition of toc 13c toc total hydrolyzable amino acids thaa total neutral sugars tsug lignin phenols lig two different lipid biomarkers of marine phytoplankton origin and vascular plantwax n alkanes and n acids comparison shows changes for all properties depicting the effect of post depositional aerobic oxidation the oxidation process re mineralized approximately 80 of the toc and approximately 60 of the tn in the original deposit and left the residual organic matter depleted in 13c by 1 7 2 9 thaa and tsug account for 10 or less of the toc in all samples leaving approximately 90 of the toc chemically unidentified thaa tsug lig marine phytoplankton biomarkers and plantwax n acids were lost from the oxidized deposit to an extent as great as that for toc two non protein amino acids alanine and aminobutyric acid and plant wax n alkanes displayed much less degradation 9 37 and concentrated 3 3 4 8 times relative to toc by the oxidation process these observations show that both marine and terrestrial components contribute to the re mineralized toc fraction a binary mixing approach was used to model quantitatively the change in 13c toc and plantwax n alkane concentration results suggest that terrestrial organic carbon contributes approximately 15 to the toc content of the original turbidite its abundance increases approximately 2 4 times as a consequence of the oxidation process and approximately 40 and 90 of the terrestrial and marine component of toc in the original turbidite respectively was destroyed by the oxidation process although selective preservation of terrestrial relative to marine organic carbon is a well documented phenomenon in sedimentary processes this study represents the first attempt to assess the sensitivity of terrestrial organic matter to oxidative degradation in a sedimentary environment

sedimentary nitrogen isotopic ratio as a recorder for surface ocean nitrate utilization in two contrasting regions of the ocean the equatorial pacific and the southern ocean the 15n of core top sediments were strongly related to no3 in surface waters with distance from the equator in the equatorial pacific 15n increased from 7 to 16 as no3 decreased from 8 m to 0 1 m going from 60 to 30 s in the se indian ocean core top 15n increased from 5 to 11 as surface no3 decreased from 25 m to 0 1 m these results are strong evidence that sedimentary 15n in these regions is recording the increasing isotopic enrichment of near surface no3 with its depletion by phytoplankton in the case of the equatorial pacific 15n values for sinking particles collected at 150 m matched well the core top sediment values demonstrating little diagenetic alteration of the near surface generated isotopic signal these equatorial pacific data sets have variations with near surface no3 consistent with rayleigh fractionation kinetics for a fractionation factor u of 2 5 this value is substantially lower than previously found for temperate or polar regions perhaps as a result of differences in phytoplankton species assemblage or growth condition in the southern ocean south of the polar front comparison of 15n values for opal rich sediments south and sinking particles indicates an apparent 5 diagenetic enrichment relative to the surface generated signal that requires further investigation this exception aside our observations show that the surface water relationship of increasing 15n with increasing no3 depletion is generally transmitted to and preserved in the sediments an important requirement for further development and application of this important paleoceanographic tool

an organic geochemical assessment of oceanographic conditions at manop site c over the past 26 000 years eleven sediment samples taken downcore and representing the past 26 kyr of deposition at manop site c 0 57 2 n 138 57 3 w were analyzed for lipid biomarker composition biomarkers of both terrestrial and marine sources of organic carbon were identified in general concentration profiles for these biomarkers and for total organic carbon toc displayed three common stratigraphic features in the time series 1 a maximum within the surface sediment mixed layer 4 ka 2 a broad minimum extending throughout the interglacial deposit and 3 a deep pronounced maximum within the glacial deposit using the biomarker records a simple binary mixing model is described that assesses the proportion of terrestrial to marine toc in these sediments best estimates from this model suggest that 20 of the toc is land derived introduced by long range eolian transport and the remainder is derived from marine productivity the direct correlation between the records for terrestrial and marine toc with depth in this core fits an interpretation that primary productivity at site c has been controlled by wind driven upwelling at least over the last glacial interglacial cycle the biomarker records place the greatest wind strength and highest primary productivity within the time frame of 18 to 22 kyr b p diagenetic effects limit our ability to ascertain directly from the biomarker records the absolute magnitude that different types of primary productivity have changed at this ocean location over the past 26 kyr

molecular paleoclimatology reconstruction of climate variabilities in the late quaternary abstract lipid class compounds were studied in the deep sea surface sediments from the central pacific across a latitudinal transect at 175 e 48 n 15 s and a box core from the western tropical pacific to discuss their utility as paleoclimatological indicators higher concentrations of c25 c35 n alkanes were observed in the higher latitudes in the north pacific their latitudinal distributions are similar to the spatial distributions of the observed soil dust concentrations observed in the central north pacific atmosphere suggesting that the sedimentary c25 c35 n alkanes are atmospherically transported from terrestrial higher plants and can be used as an indicator of terrestrial input to ocean environments downcore distributions of total c25 c35 n alkanes suggest that terrestrial input doubled over the western tropical pacific at the lgm and decreased by a factor of two at the last deglaciation period in comparison with the holocene the latitudinal distributions of c17 c20 n alkanes and pristane are higher in the high latitudes and equatorial region probably reflecting the higher primary productivity in surface waters of these oceans the downcore profiles of these compounds as well as total organic carbon long chain alkenones and dinosterol suggest that biological production decreased significantly during the deglaciation period and slightly increased during the lgm compared with that of the holocene the downcore uk37 record suggests that the sst was almost constant over the last 20 000 y which agrees well with the climap results and foraminifera 18o although it disagrees with results from coral sr ca ratios and 18o records

the almacik mafic ultramafic complex exhumed sakarya subcrustal mantle adjacent to the istanbul zone nw turkey the almacik mountains in northwestern turkey expose an upper amphibolite facies complex consisting of alternating ultramafic harzburgitic and websteritic and mafic metagabbroic rock types in the eastern part of this complex are island arc meta tholeiites and transitional to calc alkaline metabasites that are chemically quite similar to those of the permo triassic cele mafic complex north of bolu and this suggests an equivalence however much of the section exposes structurally deeper and chemically different mafic and ultramafic rocks which have no equivalent in the cele mafic complex and isotopic dating has suggested that these rocks also formed during the permian period and underwent triassic and jurassic metamorphism furthermore sparse inherited ages unlike those from istanbul zone granitoids suggest a link with north african derived armorican type basement and hence the sakarya zone rather than amazonia derived avalonian basement alternating mafic and ultramafic rocks suggest structural repetition supported by the exposure of discrete high strain zones or poorly exposed shattered rock west of each outcrop of ultramafic rocks the high grade of metamorphism and the absence of either extrusive lavas or sheeted dyke rocks suggests that the almacik complex was not an ophiolite but formed instead as subcontinental lower crust and subjacent mantle dominantly calc alkaline geochemistry suggests that it formed the basement to an active continental margin bounding the north side of the sakarya continent with s dipping subduction of palaeotethys the almacik complex was uplifted as a late result of compression against the southern margin of the istanbul zone in the jurassic period lack of coeval high grade metamorphism in the istanbul zone indicates that the latter was overthrust southwards over the sakarya margin and that there was therefore a change of subduction polarity in the triassic period the evidence further casts doubt on the existence of a mesozoic intra pontide ocean in northwestern turkey and suggests that the latest permian magmatism with subsequent triassic and jurassic metamorphism was instead related to the closure of the palaeotethyan ocean

evidence for a younger dryas like cooling event on the british columbia coast two independent paleoclimatic records from the pacific coast of canada indicate that a late glacial warming trend was interrupted by a return to colder conditions between about 11 000 and 10 200 radiocarbon yr b p correlative with the classical younger dryas chronozone of the north atlantic region fossil benthic foramnifera from three cores from the continental shelf dated by accelerator mass spectrometry show peak abundances of the cold water indicator species cassidulina reniforme at this time fossil pollen spectra from two sites on the queen charlotte islands record a shift from forest to open herb rich vegetation after 11 100 yr b p probably in response to colder and wetter conditions identified by pollen climate transfer functions these preliminary data for a cold oscillation between ca 11000 and 10000 yr ago in the northeast pacific argue that this deglacial phenomenon was not restricted to the north atlantic but was a hemispheric and possibly global event

late glacial to holocene changes in winds upwelling and seasonal production of the northern california current system abstract a core 120 km off the coast of southern oregon was examined for changes in lithology diatoms and pollen over the past 30 000 yr primary production during the late pleistocene was about half that of the holocene evidence from diatoms and pollen indicates that summer upwelling was much weaker implying an absence of strong northerly winds early pliocene diatoms found throughout the late pleistocene section were probably derived from diatomites east of the cascades and provide evidence for strong easterly winds over a dry continental interior the findings verify predictions of a climate model based on glacial maximum conditions there is no compelling evidence for a climatic reversal corresponding to the european younger dryas chron during the early holocene 9000 7000 yr b p there may have been years when winds were insufficiently strong to support upwelling so that warm stratified waters lay closer to the coast

biomarker temperature estimates for modern and last glacial surface waters of the california current system between 33 and 42 n sea surface temperature sst estimates were made using data for c37 39 alkenones analyzed in modern and glacial age intervals of sediment cores collected along an east west 42 n from 125 to 132 w and a north south 41 33 n transect of the california current system ccs the prymnesiophyte biomarker results suggest that surface waters warmed significantly throughout this region since the last glacial maximum lgm but the magnitude of warming varied spatially stratigraphic profiles from four sediment cores along the north south transect indicate the warming period was confined to the glacial interglacial transition 15 10 ka with sst reaching a maximum value at 10 ka and maintaining a uniformly high value throughout the holocene comparison of estimates derived from analysis of modern and lgm sediment intervals indicates the magnitude of the sst change was minimal for locations south of about 36 n 1 2 c and increased significantly 3 5 c north of this latitude using a simple heat balance model we calculate from the latitudinal gradient in sst that southward flow in the california current system during the lgm was about 60 of that measured today at 36 n our findings support the conclusion of others based on pollen data that coastal upwelling in the region of the northeast pacific off northern california was significantly reduced or even completely shutdown during the lgm

biogenic sedimentation beneath the california current system for the past 30 kyr and its paleoceanographic significance a north south transect of 17 cores was constructed along the eastern boundary of the california current system from 33 to 42 n to investigate the changes in biogenic sedimentation over the past 30 kyr percentages and mass accumulation rates of caco3 corg and biogenic opal were assembled at 500 to 1000 years sample to provide relatively high resolution time space maps reveal a complex pattern of changes that do not follow a simple glacial interglacial two mode model biogenic sedimentation shows responses that are sometimes time transgressive and sometimes coeval and most of the responses show more consistency within a limited geographic area than any temporal consistency reconstructed conditions during late oxygen isotope stage 3 were more like early holocene conditions than any other time during the last 30 kyr coastal upwelling and productivity during oxygen isotope stage 3 were relatively strong along the central california margin but were weak along the northern california margin precipitation increased during the last glacial interval in the central california region and the waters of the southern california margin had relatively low productivity productivity on the southern oregon margin was relatively low at the beginning of the last glacial interval but by about 20 ka productivity in this area significantly increased this change suggests that the center of the divergence of the west wind drift shifted south at this time the end of the last glacial interval was characterized by increased productivity in the southern california margin and increased upwelling along the central california margin but upwelling remained weak along the northern california margin a sudden 300 years decrease in caco3 corg and biogenic opal occurred at 13 ka the changes suggest a major reorientation of the atmospheric circulation in the north pacific and western north america and the establishment of a strong seasonality in the central california region a carbonate preservation event occurred at 10 ka that appears to reflect the uptake of co2 by the terrestrial biosphere as the northern latitudes were reforested following retreat of the glaciers the holocene has been a period of relatively high productivity in the southern california margin relatively strong coastal upwelling along the central california margin relatively weak upwelling along the northern california margin and the northward migration of the divergence zone of the west wind drift

late cenozoic tectonics and stratigraphy of northwestern anatolia the effects of the north anatolian fault to the region in northwest anatolia there is a mosaic of different morpho tectonic fragments within the western part of the right lateral strike slip north anatolian fault naf zone these were developed from compressional and extensional tectonic regimes during the paleo and neo tectonic periods of turkish orogenic history a ne sw trending left lateral strike slip fault system adapazari karasu fault extends through the northern part of the sakarya river valley and began to develop within a n s compressional tectonic regime which involved all of northern anatolia during middle eocene to early middle miocene times since the end of middle miocene times this fault system forms a border between a compressional tectonic regime in the eastern area eastwards from the northern part of the sakarya river valley and an extensional tectonic regime in the marmara region to the west the extension caused the development of basins and ridges and the incursions of the mediterranean sea into the site of the future sea of marmara since late miocene times following the initiation in late middle miocene times and the eastward propagation of extension along the western part of the naf a block north anatolian block began to form in the northern anatolia region since the end of pliocene times the adapazari karasu fault constitutes the western boundary of this block which is bounded by the naf in the south the northeast anatolian fault in the east and the south black sea thrust fault in the north the northeastward movement of the north anatolian block caused the formation of a marine connection between the black sea and the aegean mediterranean sea during the pleistocene

the arkot dag melange in arac area central turkey evidence of its origin within the geodynamic evolution of the intra pontide suture zone abstract in northern turkey the intra pontide suture zone is represented by an east west trending belt of deformed and or metamorphic units located at the boundary between the istanbul zonguldak terrane to the north and the sakarya terrane to the south these units can be regarded as issued from the intra pontide domain whose geodynamic history is still a matter of debate along the akpinar arac bayramoren geotraverse located in central turkey an ophiolite bearing melange known as the arkot dag melange is well exposed along the intra pontide suture zone the arkot dag melange plays a key role in the interpretation of the geodynamic history of the intra pontide domain and can be described as a late santonian chaotic sedimentary deposit consisting of an up to 1000 m thick succession of slide blocks of different sizes and lithologies enclosed in a sedimentary matrix consisting of shales coarse grained arenites pebbly mudstones and pebbly sandstones the slide blocks from a few meters to hectometers in size are represented by metamorphic rocks mainly micaschists and gneisses by ophiolites peridotites gabbros iat and babb basalts and cherts and by sedimentary rocks cherts neritic and pelagic limestone marly limestone and ophiolite bearing turbidites the youngest age among the slide blocks has been provided by the ophiolite bearing turbidites where a late coniacian nannofossil assemblage has been found the cherts have provided a wide range of ages from the middle triassic to late cretaceous whereas the fossils found in the limestone indicate late jurassic to early cretaceous ages the matrix of the arkot dag melange even if unaffected by metamorphism shows deformations represented by multiple meters thick cataclastic shear zones at the boundaries of the melange slices or inside of them according to its features the source area of the arkot dag melange was most likely a continental and oceanic thrust sheet emplaced in the late cretaceous onto a continental margin the data collected from the different slide blocks suggest that the intra pontide domain was characterised by an oceanic basin opened at the latest in the early jurassic the opening of the intra pontide oceanic basin was followed by the development of a subduction zone with a subsequent opening of suprasubduction oceanic basin in the middle jurassic early cretaceous the convergence in this suprasubduction oceanic basin started at the early late cretaceous boundary by an obduction process whereas its final closure can be regarded as late paleocene in age

apatite fission track thermochronology of the western pontides nw turkey the results of apatite fission track analyses of the western pontides of nw turkey point to three discrete episodes of cenozoic exhumation correlatable with major supraregional tectonic events 1 paleocene early eocene exhumation reflected the closure of theocean 2 late eocene earliest oligocene exhumation was the result of renewed tectonic activity along thesuture 3 late oligocene early miocene exhumation recorded the onset of northern aegean extension samples collected north and south of the tectonic contact between the two terranes forming the western pontides i e and sakarya terranes record the same cooling events suggesting that such terranes were amalgamated in pre cenozoic times

the cele mafic complex evidence for triassic collision between the sakarya and istanbul zones nw turkey abstract the lowest structural levels of the istanbul zone are exposed in the sunnice massif north of bolu they comprise the greenschist facies ediacaran calc alkaline bimodal yellice metavolcanics which are intruded by the dirgine granitoid amphibolite facies mafic and subordinate ultramafic rocks of the cele mafic complex hitherto termed the cele meta ophiolite include hornblende gneisses of island arc meta tholeiitic and transitional to calc alkaline metagabbroic compositions and were previously thought to be part of the istanbul zone basement together with minor serpentinized troctolite and harzburgite lenses they are exposed in a broadly antiformal structure beneath the yellice metavolcanics although these rocks structurally underlie and on account of their higher metamorphic grade were previously thought to be older than the ediacaran cambrian rocks of the istanbul zone basement their oldest isotopic dates are permian indicating that they are instead much younger than the overlying rocks from which they must be divided by an inferred istanbul zone basal thrust instead these mafic rocks may be linked to the almacik complex and hence interpreted as the underthrust crustal base to a permo triassic active continental margin attached to the gondwana derived sakarya zone now located south of the istanbul zone triassic and jurassic metamorphic ages record compressional events marking a cimmerian event closing the palaeotethys ocean

long chain alkenones and alkyl alkenoates and the fossil coccolith record of marine sediments long chain n c37 c39 alkenones and alkyl alkenoates are biological markers for sediment inputs of algae from the class prymnesiophyceae which includes the coccolithophorids these compounds have been recognized in many recent and ancient marine sediments but in only a few living algal species notably the ubiquitous coccolithophorid emiliania huxleyi the proven value of long chain alkenones in palaeotemperature assessment prompts an evaluation of their sedimentary record especially their correspondence with coccolithophorid fossils in ancient marine sediments synthesis of available micropalaeontological and molecular data suggests that morphologically related species of the genera crenalithus dictyococcites emiliania gephyrocapsa pseudoemiliania and reticulofenestra all belonging to the family gephyrocapsaceae were potential biological sources of alkenones and alkyl alkenoates in marine sediments deposited since the eocene 45 ma the occurrence of alkenones in cenomanian and albian sediments devoid of nannofossils may be presumed to reflect contributions from ancestors of the gephyrocapsaceae although an investigation of cretaceous samples containing both coccoliths and alkenones would provide further evidence of this proposed correspondence the combination of palaeontological and molecular chemotaxonomic information offers a novel approach to the evaluation of the phylogenetic lineages that link living and extinct algae

the isotopic composition of diatom bound nitrogen in southern ocean sediments treatment of diatom microfossils from southern ocean sediments with hot perchloric acid leaves a diatom bound n fraction which is 0 4 lower in 15n than the bulk sediment typically 3 lower in recent antarctic diatom ooze results from southern ocean surface sediments indicate that early diagenetic changes in bulk sediment n content and 15n are not reflected in diatom bound n suggesting that diatom bound n is physically protected from early diagenesis by the microfossil matrix a meridional transect of multicores from the indian sector of the southern ocean shows a northward increase in the 15n of diatom bound n suggesting that diatom bound 15n like bulk sedimentary 15n varies with nitrate utilization in the overlying surface waters the 15n of diatom bound n is 3 4 higher in glacial age antarctic sediments than in holocene sediments supporting the hypothesis previously based on bulk sediment 15n that nitrate utilization in the surface antarctic was higher during the last ice age while there are important uncertainties the inferred range of utilization changes could potentially explain the entire 80 ppm amplitude of observed glacial interglacial variations in atmospheric co2

analysis of the north anatolian shear zone in central pontides northern turkey insight for geometries and kinematics of deformation structures in a transpressional zone abstract the western part of the north anatolian shear zone at the southern boundary of the central pontides in turkey was investigated in the kursunlu arac area by means of a geological structural field study in this area the north anatolian shear zone results in a transpressional deformation zone that extends between two master faults striking parallel to the main shear direction the main systems of structures identified in the deformation zone appear to be oriented parallel to the directions predicted by riedel theoretical model nevertheless the strain partitioning is more complicated than predicted by theory the structural analysis suggests a polyphase deformation characterized by a steady component of transcurrence associated with alternance of compression and extension along each of theoretical directions the combination of double verging structures can be observed with folds and thrust surfaces root into high angle shear zones according to flower type geometries the discrepancies of directions kinematics and geometries from theoretical models are due to transpressive and or transtensive nature of the deformation according to the observed outcropping structures we propose a conceptual model for the north anatolian shear zone interpreting it as a crustal scale positive flower structure

controls on the carbon isotopic composition of southern ocean phytoplankton carbon isotopic compositions of suspended organic matter and biomarker compounds were determined for 59 samples filtered from southern ocean surface waters in january 1994 along two north south transects woce sr3 from tasmania to antarctica and across the princess elizabeth trough pet east of prydz bay antarctica along the sr3 line bulk organic matter show generally decreasing 13c contents southward which are well correlated with increasing dissolved molecular carbon dioxide concentrations co2 aq this relationship does not hold along the pet transect using concentrations and isotopic compositions of molecular compounds we evaluate the relative roles of several factors affecting the 13c of southern ocean suspended particulate organic matter along the woce sr3 transect the concentration of co2 aq plays an important role it is well described by a supply versus demand model for the extent of cellular co2 utilization and its associated linear dependence of isotopic fractionation ep on the reciprocal of co2 aq an equally important factor appears to be changes in algal assemblages along the sr3 transect with their contribution to isotopic fractionation also well described by the supply and demand model when formulated to include the cell surface volume control of supply changes in microalgal growth rates appear to have a minor effect on ep along the pet transect algal assemblage changes and possibly changes in microalgal growth rates appear to strongly affect the carbon isotopic variations of suspended organic matter these results can be used to improve the formulation of modern carbon cycle models that include phytoplankton carbon isotopic fractionation

intensification of the oxygen minimum zone in the northeast pacific off vancouver island during the last deglaciation ventilation and or export production 1 the oxygen minimum zone omz off vancouver island was more oxygen depleted relative to modern conditions during the allerod 13 5 to 12 6 calendar kyr and again from 11 to 10 kyr the timing of omz intensification is similar to that seen throughout the north pacific although the onset appears to have been delayed by 1500 years off vancouver island radiocarbon dating of coeval benthic and planktonic foraminifera shows that between 16 0 and 12 6 kyr the age contrast between surface and intermediate waters 920 m depth off vancouver island was similar to or slightly less than that today there is no evidence of an increased age difference i e decreased ventilation during the deglaciation particularly during the allerod however sedimentary marine organic carbon concentration and mass accumulation rate increased substantially in the allerod suggesting that increased organic matter export was the principal cause of late pleistocene omz intensification off vancouver island

a comparison of the geological and geoelectrical structures in the eastern marmara region nw turkey abstract northwestern anatolia contains different tectonic units which are presently bounded by the two branches of the north anatolian fault the pontide zone in the north consists of the istanbul zonguldak unit to the west and the ballidag kure unit a remnant of paleo tethyan ocean in the east the sakarya zone in the south is juxtaposed against the pontide zone due to the closure of paleo tethys the armutlu ovacik zone represents a tectonic mixture of both zones in the north and south neotectonic units such as the izmit sapanca corridor and the northern sakarya low which developed south of the istanbul zone and north of the sakarya zone respectively represent an extensional tectonic regime the relationship and continuations of these tectonic entities in the region were examined by a 90 km long nw se trending magnetotelluric profile electrical resistivity is quite low 10 ohm m beneath the northern sakarya low and the sakarya zone at a depth of 26 km compared to the northern areas this low resistivity zone may provide an indication of thinning in the total crustal thickness and a viscoelastic lower crust furthermore in the northern part of the profile the five layered conductive sequence obtained by magnetotelluric modelling may correspond to fragments of the istanbul zone and the ballidag kure unit underlying it

organic carbon accumulation over the last 16 kyr off vancouver island canada evidence for increased marine productivity during the deglacial abstract the organic carbon content of marine sediments is commonly used as a proxy for export production however in continental margin sediments a large fraction of the organic matter may be of terrestrial origin and it is necessary to correct the total organic carbon data accordingly radiocarbon dating of bulk organic carbon organic geochemistry and isotope data 13c and 15n are used here to characterize the type of organic matter present in core jt96 09 collected at a water depth of 920 m on the slope off western canada the quantities of marine and terrestrial organic carbon are then estimated using the 13c data the 16 kyr record obtained from core jt96 09 suggests that accumulation of total organic carbon was highest during the late glacial and deglacial but geochemical data indicate that as much as 70 of this carbon is terrestrial in origin when the palaeo record is corrected for this terrigenous input it is observed that accumulation of marine organic matter and presumably marine export production increased at the end of the last glacial contemporaneous with the bolling and that it peaked during the allerod data from other palaeoproductivity proxies i e bio barium opal and alkenones also indicate relatively high productivity during the deglacial these results indicate a return to modern upwelling conditions and high marine export production at 14 3 calendar kyr bp and a period of enhanced upwelling relative to the present during the allerod

ophiolite emplacement by strike slip tectonics between the pontide zone and the sakarya zone in northwestern anatolia turkey northwestern anatolia contains three main tectonic units a the pontide zone in the north which consists mainly of the istanbul zonguldak unit in the west and the ballidag kure unit in the east b the sakarya zone or continent in the south which is juxtaposed against the pontide zone due to the closure of paleo tethys prior to late jurassic time and c the armutlu ovacik zone which appears to represent a tectonic mixture of both zones these three major tectonic zones are presently bounded by the two branches of the north anatolian transform fault the two tectonic contacts follow older tectonic lineaments the western pontide fault which formed during the development of the armutlu ovacik zone since the earliest cretaceous an overall extensional regime dominated the region a transpressional tectonic regime of coniacian santonian to campanian age caused the welding of the istanbul zonguldak unit to the sakarya zone by an oblique collision in the late campanian a transtensional tectonic regime developed forming a new basin within the amalgamated tectonic mosaic the different tectonic regimes in the region were caused by activity of the western pontide fault most of the ophiolites within the armutlu ovacik zone belong to the paleo tethyan and or pre ordovician ophiolitic core of the istanbul zonguldak unit the late cretaceous ophiolites in the eastern parts of the armutlu ovacik zone were transported from neo tethyan ophiolites farther east by left lateral strike slip faults along the western pontide fault there is insufficient evidence to indicate the presence of an ocean intra pontide ocean between the istanbul zonguldak unit and the sakarya zone during late cretaceous time

a new classification of the turkish terranes and sutures and its implication for the paleotectonic history of the region abstract the turkish part of the tethyan realm is represented by a series of terranes juxtaposed through alpine convergent movements and separated by complex suture zones different terranes can be defined and characterized by their dominant geological background the pontides domain represents a segment of the former active margin of eurasia where back arc basins opened in the triassic and separated the sakarya terrane from neighbouring regions sakarya was re accreted to laurasia through the balkanic mid cretaceous orogenic event that also affected the rhodope and strandja zones the whole region from the balkans to the caucasus was then affected by a reversal of subduction and creation of a late cretaceous arc before collision with the anatolian domain in the eocene if the anatolian terrane underwent an evolution similar to sakarya during the late paleozoic and early triassic times both terranes had a diverging history during and after the eo cimmerian collision north of sakarya the kure back arc was closed during the jurassic whereas north of the anatolian domain the back arc type oceans did not close before the late cretaceous during the cretaceous both domains were affected by ophiolite obduction but in very different ways north directed diachronous middle to late cretaceous melange obduction on the jurassic sakarya passive margin senonian synchronous southward obduction on the triassic passive margin of anatolia from this it appears that the izmir ankara suture currently separating both terranes is composite and that the passive margin of sakarya is not the conjugate margin of anatolia to the south the cimmerian taurus domain together with the beydaglari domain part of the larger greater apulian terrane were detached from north gondwana in the permian during the opening of the neotethys east mediterranean basin the drifting cimmerian blocks entered into a soft collision with the anatolian and related terranes in the eo cimmerian orogenic phase late triassic thus suturing the paleotethys at that time the taurus plate developed foreland type basins filled with flysch molasse deposits that locally overstepped the lower plate taurus terrane and were deposited in the opening neotethys to the south these olistostromal deposits are characterized by pelagic carboniferous and permian material from the paleotethys suture zone found in the mersin melange the latter as well as the antalya and mamonia domains are represented by a series of exotic units now found south of the main taurus range part of the mersin exotic material was clearly derived from the former north anatolian passive margin huglu type series and re displaced during the paleogene this led us to propose a plate tectonic model where the anatolian ophiolitic front is linked up with the samail baer bassit obduction front found along the arabian margin the obduction front was indented by the anatolian promontory whose eastern end was partially subducted continued slab roll back of the neotethys allowed anatolian exotics to continue their course southwestward until their emplacement along the taurus southern margin mersin and up to the beydaglari promontory antaya mamonia in the latest cretaceous paleocene the supra subduction ocean opening at the back of the obduction front troodos type ocean was finally closed by eocene north south shortening between africa and eurasia this brought close to each other cretaceous ophiolites derived from the north of anatolia and those obducted on the arabian promontory the latter were sealed by a maastrichtian platform and locally never affected by alpine tectonism whereas those located on the eastern anatolian plate are strongly deformed and metamorphosed and affected by eocene arc magmatism these observations help to reconstruct the larger frame of the central tethyan realm geodynamic evolution

tectonostratigraphic evolution of the basins on the southern branch of the north anatolian fault system in the se marmara region turkey the lithostratigraphy of the mekece iznik corridor the geyve pamukova and the iznik basins on the southern branch of the north anatolian fault system nafs sb was investigated in detail the intra basin deposits carried by sakarya river and the drainage systems in the northern and southern elevated blocks of the iznik and geyve pamukova basins have been classified based on their lithofacies characteristics the geyve pamukova basin which has developed with a nne ssw trending transtensional strain was formed as a lazy z shaped and releasing bend or pure strike slip pull apart basin that is related to simple shear right lateral strike slip faulting the iznik basin was formed by a right lateral strike slip faulting kinematics and nne ssw trending transtension as a result of the step over of the northeast trending dirazali fault from the southern edge to the nw trending gurle fault and the western step over of this fault to the e w trending umurbey fault this strike slip setting is also supported by the nw se trending right lateral oblique normal orhangazi fault on the northern edge of the basin according to this the iznik basin can be described as a more advanced stage of a large scale pull apart basin compared with a lazy z shaped and releasing bend or transtensional strain furthermore it is defined as the former stage of an extreme or rhomboid type transtensional pull apart basin

geomechanical model of the marmara sea region i 3 d contemporary kinematics summary we investigate by means of a 3 d geomechanical model the relationship between structural elements and contemporary kinematics in the marmara sea region northwest turkey the recently imaged fault system beneath the marmara sea is incorporated into the model as frictional surfaces with varying strike and dip the main marmara fault is implemented as through going and is accompanied by mostly non vertical second order faults topography basement topography and the moho become mechanically effective through changes in density and elastic parameters across these horizons the model is subjected to gravity and kinematic boundary conditions the ultimate goal of this study is to set up a 3 d model that is consistent with both kinematic observations and stress data the stress results are presented in a complementary paper in this paper we present the modelled long term 3 d kinematics in terms of fault slip rates rotations vertical motion and sense of fault slip the model results agree with global positioning system velocities geological fault slip rates palaeomagnetic measurements and with the observed pattern of subsidence and uplift furthermore our tectonically driven vertical velocities can be linked to landscape and basin evolution and to features of sedimentation our results indicate that the main marmara fault can be interpreted as a through going fault that slips almost purely in a strike slip sense nevertheless and not contradictory to the previous statement there is significant dip slip motion at some sections of the main marmara fault the agreement of the modelled 3 d kinematics with model independent observations supports that the main structural details of the fault system are accounted for sensitivity analysis of model parameters reveals that changes in rock properties and the initial stress state have minor influence on the 3 d kinematics we conclude that the 3 d structure of the fault system is the key control of the kinematics the slip rate of the main marmara fault from our model is lower than previous estimates and shows high variability along strike 12 8 17 8 mm a 1 the latter indicates that stress accumulation is non uniform along strike

paleodeviations of radiocarbon marine reservoir values for the northeast pacific differences in the radiocarbon ages of coeval marine shells and wood from emergent glaciomarine sediments in the fraser lowland of southwestern british columbia and northwest washington indicate that a total marine radiocarbon reservoir value of 1 1 1 k y is applicable in the region this is 40 greater 300 yr than the 800 yr value currently used to correct the ages of both modern and late pleistocene marine shells from this area the glaciomarine sediments were deposited rapidly between ca 12 5 and 11 5 1 4 c k y b p paleodeviations of the marine reservoir value may illustrate that rapid environmental changes occurred during the last glacial to interglacial transition these variations are thought to have been caused by changes in both deep and surface ocean circulation and by variations in the production of atmospheric radiocarbon 1 4 c these findings may indicate a rapid reordering of oceanic atmospheric circulation in the region

barium and the late paleocene δ13c maximum evidence of increased marine surface productivity deep sea sediment ba ba al2o3 sample 15 ba aluminosilicate records show increasing values synchronous with the evolution of the late paleocene global 13c maximum reflecting an increase in marine surface primary production and biogenic barite formation at this time at two oligotrophic locations deep sea drilling project dsdp sites 384 and 527 in the north and south atlantic respectively ba increases from 160 360 ppm in the early paleocene to 1100 3000 ppm during the 13c maximum at equatorial dsdp site 577 positioned within or near the high productivity zone ba increases from 15 500 ppm in the early paleocene to 25 400 ppm in conjunction with late paleocene maximum 13c values linear fitted correlation plots of sediment ba content versus surface water 13c in all three regions support barite originating in the euphotic zone the early to late paleocene relative increase in ba illustrates how burial rates of corg relative to al2o3 accelerated by a factor of 1 8 and 6 0 in the eutrophic and oligotrophic areas respectively a tentative estimate weighing our result for the entire ocean suggests that accumulation rates of organic carbon increased by a factor of 2 during the late paleocene 13c maximum

fission track thermochronology vertical kinematics and tectonic development along the western extension of the north anatolian fault zone 1 we have investigated the low temperature history of pre neogene basement areas adjacent to the western extension of the north anatolian fault zone nafz by apatite fission track thermochronology of 33 samples taken from marmara island kapidag peninsula both in the sea of marmara samothrake island and chalkidike peninsula both in the north aegean region together with already published apatite fission track data from 30 other sampling localities of the region these data 63 in total have been evaluated mainly with regard to the transitional period from the mesohellenic orogeny eocene oligocene to the plate tectonical individualization of the aegean antolian microplate to gain a better understanding of the tectonical chronology that has led to modern east mediterranean plate tectonics apatite fission track investigations of the area under discussion reveal two major events of cooling and exhumation of pre neogene rocks a first frequency maximum of cooling ages between 35 and 25 ma late eocene to early oligocene is due to postorogenic regional erosion after the climax of the mesohellenic orogeny which was caused by continental collision of the pelagonian platform and the rila rhodope zone after the final closure of the axios vardar ocean a second frequency maximum of cooling ages between 17 and 11 5 ma early to middle miocene depicts more localized uplift and exhumation in consequence of transpressive and or transtensive movements along early structural discontinuities that gave rise to the later fault systems in the western extension of the nafz the earliest fault structures of this system have developed shortly after the orogenic collapse and crustal extension of the rila rhodope area but quasi simultaneously with the onset of subduction along the modern hellenic trench the regional distribution of fission track ages of the miocene age group 17 to 11 5 ma and corresponding thermochronological calculations based on frequency distributions of confined track lengths suggest that an early fault propagation has occurred from east to west during the miocene the onset of subduction along the hellenic trench and subsequent gravitational retreat of the subducting oceanic slab are considered as a major cause for transtension of the aegean crust especially with regard to the development of north aegean pull apart basins such early fault structures have facilitated the westward propagation of a continuous nafz that took place during the pliocene from the easternmost marmara region to the gallipoli peninsula and to the north aegean trough

pleistocene to holocene contrasts in organic matter production and preservation on the california continental margin organic matter in sediments from cores collected from the upper continental slope 200 2700 m off california and southern oregon shows marked differences in concentration and marine character between the last glacial interval ca 24 10 ka and either holocene time or last interstadial oxygen isotope stage 3 ca 60 24 ka in general sediments deposited during holocene time and stage 3 contain higher amounts of marine organic matter than those deposited during the last glacial interval and this contrast is greatest in cores collected off southern california the most profound differences in stage 3 sediments are between predominantly bioturbated sediments and occasional interbeds of laminated sediments the sediments are from cores collected within the present oxygen minimum zone on the upper continental slope from as far north as the oregon california border to as far south as point conception these upper pleistocene laminated sediments contain more abundant hydrogen rich type ii marine algal organic matter than even surface sediments that have large amounts of nonrefractory organic matter the stable carbon isotopic composition of the organic matter does not change with time between bioturbated and laminated sediments indicating that the greater abundance of type ii organic matter in the laminated sediments is not due to a change in source but rather represents a greater degree of production and preservation of marine organic matter the presence of abundant well preserved organic matter supports the theory that the oxygen minimum zone in the northeastern pacific ocean was more intense and possibly anoxic during late pleistocene time as a result of increased coastal upwelling that enhanced algal productivity

tunneling in squeezing rock the bolu tunnel anatolian motorway turkey abstract the bolu tunnel is subject to considerable deformation due to stress related failure in the rock mass in thrust zones and strike slip faults that transect the tunnel these deformations resulted in some serious geotechnical problems which were overcome either by flexible or extremely heavy support systems the heavy system was used to prevent or bring under control the large deformations that would take place during excavation whereas the flexible method allows the deformations to develop without restraint the heavy support system was used in thrust fault zones and in flysch zones in the bolu tunnel and produced more successful results in comparison to the flexible support system a brief explanation of the tunnel collapse in the duzce earthquake is also provided

jurassic arc volcanism on crimea ukraine implications for the paleo subduction zone configuration of the black sea region article i nfo the early cretaceous and younger opening of the black sea has obliterated much of the older record of tethyan subduction below southeastern europe the earlier mesozoic evolution was dominated by opening and closure of tethyan oceans between gondwana and laurasia with their consumption at least in part accommodated along the southern eurasian margin crimea ukraine a peninsula in the northern black sea represents the northernmost region of southeastern europe that exposes a record of a pre cretaceous tethyan active margin to shed new light on the paleosubduction zone configuration of the southeastern european margin in the jurassic we report 40

the relationship between sedimentary organic carbon isotopic composition and organic biomarker compound concentration abstract a study of organic biomarker compounds which could serve as tracers of terrigenous and marine sedimentary organic matter sources was performed on samples from a 208 7 m hydraulic piston core hole dsdp hole 619 from the hemipelagic pigmy basin in the northern gulf of mexico organic carbon normalized concentrations of total long chain c37 c39 alkenones and some individual c27 c29 desmethyl sterols were determined to be useful proportional indicators tracers of preserved marine and terrigenous organic carbon respectively the alkenones whose only known source is marine phytoplankton of the class prymnesiophyceae generally occurred in higher concentrations in interglacial isotope stages 1 and 5a b than in the intervening glacial stages sterols c27 c29 apparently of a dominantly terrigenous origin occurred in lower concentrations during interglacial stages than in glacial stages tracers of both terrigenous and marine organic matter appear to be affected by the differential diagenetic alteration of the biomarker corg ratios as indicated by a simple first order kinetic model the lack of any desmethylor 4a methylsterol which is linearly related to the proportion of marine sedimentary organic matter as scaled by 13corg indicates that either 1 1 sedimentary diagenesis has obscured the biomarker corg vs 13corg record 2 2 phytoplanktonic assemblage changes caused variations in the biomarker corg ratio of the primary input preferential preservation of terrigenous sterols may result in a biased sedimentary record of sterol input which could be misinterpreted as indicating solely terrigenous sterol sources a simple model which characterizes the effects of sedimentary diagenesis on the relationship between corg normalized biomarker ratios and 13corg demonstrates the potential problems of long term differential diagenetic skewing on those tracer records

climate induced variations in productivity and planktonic ecosystem structure from the younger dryas to holocene in the cariaco basin venezuela a high resolution molecular organic geochemical study of sediments in the anoxic cariaco basin indicates significant changes in primary productivity and planktonic community structure associated with the transition from the younger dryas to the holocene variations in climate conditions over the past 12 14c kyr have induced large scale changes in upwelling intensity which directly affected levels of primary productivity as reflected in accumulation rates of bulk productivity proxies concentrations and accumulation rates of sterol and alkenone biomarkers have been used to identify how productivity changes affected the structure of the planktonic ecosystem a shift in the dominant primary producer from diatoms younger dryas to coccolithophores holocene is identified if productivity and ecosystem variations like those identified in the tropical upwelling zone of the cariaco basin region occur throughout the tropical oceans they have the potential to affect global climate through perturbations in the biogeochemical cycle of carbon

basement types of the thrace basin and a new approach to the pre eocene tectonic evolution of the northeastern aegean and northwestern anatolia a review of data and concepts in northwestern turkey the pre eocene basement of the thrace basin consists of the strandja rhodope metamorphics in the north northwest the istanbul zonguldak paleozoic sequence in the northeast a tectonic mixture of the fragments from the sakarya continent and pre upper cretaceous ophiolites in the southeast and the uppermost cretaceous paleocene transgressive sediments the ophiolites belong to a dogger early cretaceous oceanic basin the northeastern vardar ocean between the rhodope and sakarya continents the ne trending oceanic branch closed diachronously during the early late malm to the northeast but during latest early cretaceous to late cretaceous time toward the main vardar ocean in the southwest during the final closure the suture zone acted as a strike slip fault zone the latest cretaceous paleocene transpressional to transtensional activities caused the juxtaposition of different basement types and the development of a tectonic mixed zone the biga armutlu ovacik zone between the rhodope and sakarya continents under the regional n s compression on the plate overlying the north northeastward dipping vardar subduction zone the southwestward escape of an area of crust bounding by the wnw trending balkan thrace dextral fault zone to the north and the ne trending biga armutlu ovacik sinistral zone to the southeast caused a triangular shaped and isolated depression area for the deposition of the uppermost cretaceous paleocene transgressive sediments in a transtensional setting the tectonically bounded depression area constitutes also a necessary accommodation space for the deposition of the initial deposits of early eocene age in the thrace basin

sea surface temperature changes in the northeastern pacific ocean during the past 20 000 years and their relationship to climate change in northwestern north america abstract modern ocean atmosphere interactions in the northeastern pacific ocean have a significant effect on the climate of the west coast of north america we present radiolarian microfossil based temperature reconstructions for the eastern north pacific spanning the past 20 000 yr to examine possible correlations and linkages between continental climate change and changes in sea surface temperature sst in the northeastern pacific ocean on millennial time scales the reconstructions indicate that the regional pattern of ocean circulation off the west coast of north america was further south 15 000 cal yr b p than it is today and reached its present location 13 000 cal yr b p the north pacific drift and transition zone were further south as a result of a more southerly north pacific high pressure cell prior to 13 000 cal yr b p while two continental paleoclimate records from northwestern north america show regional differences they also can be correlated to the sst changes a coastal site at 48 n shows similar patterns in summer temperatures as observed in offshore marine records of ssts however an inland continental record seems to reflect more regional scale changes in sea surface conditions showing a thermal maximum centered at 10 000 cal yr b p which is observed in the marine transect south of 42 n we conclude based on the pattern of oceanographic change as reflected in radiolarian assemblages that changes in the past latitudinal position of the north pacific drift played a significant role in controlling continental climate immediately to its east as it does in the present environment we also conclude that during the past 20 000 yr much of the evolution of oceanographic change is related to the migration of the atmospheric pressure cells the north pacific high and aleutian low of the northeastern pacific

what controls opal preservation in tropical deep sea sediments measurements of opal preservation in deep sea sediment cores have been presented in three ways the opal concentration as a fraction of total dry weight opaltot the opal concentration normalized to calcite free dry weight opalcalcite free and me opal accumulation rate opal mar it is tempting to interpret changes in these indices as indicators of rates of biological production in past oceans based on theoretical constraints we argue that in typical tropical and subtropical sediments both opalcalcite free and opal mar reflect a significant artifact of dilution by other phases thus the band of high opalcalcite free in the equatorial pacific appears to be caused in large part by the high calcite in that region rather than by high opal productivity the best candidate for a reliable paleoproductivity proxy appears to be opaltot unfortunately present day opaltot data from tropical and subtropical regions show little or no systematic trend with the rain rate of opal pore water silica concentration data reveal that the apparent pore water opal solubility is not constant but correlates regionally with the rain rate of opal to the seafloor a model that treats opal as a single homogeneous phase with a single well defined solubility product predicts a strong dependence of opal concentration on rain rate in stark contrast to the data and a constant asymptotic pore water si two models representing opal as multiple heterogeneous phases with different solubilities are able to reproduce the observed asymptotic pore water si rain rate relationship but not the lack of rain rate trend in the opal concentration data only by assuming a systematic trend in the quality of opal i e the solubility as a function of opal production can we reproduce the observed pattern of opal preservation the implication of this study is that changes in opal preservation in the geologic record cannot simply be interpreted in terms of changes in surface ocean productivity until our understanding of opal diagenesis can be improved

terrestrial organic carbon contributions to sediments on the washington margin elemental and stable carbon isotopic compositions and biomarker concentrations were determined in sediments from the columbia river basin and the washington margin in order to evaluate geochemical approaches for quantifying terrestrial organic matter in marine sediments the biomarkers include an homologous series of long chain n alkanes derived from the surface waxes of higher plants phenolic and hydroxyalkanoic compounds produced by cuo oxidation of two major vascular plant biopolymers lignin and cutin all marine sediments including samples collected from the most remote sites in cascadia basin showed organic geochemical evidence for the presence of terrestrial organic carbon using endmember values for the various biomarkers determined empirically by two independent means we estimate that the terrestrial contribution to the washington margin is 60 for shelf sediments 30 for slope sediments and decreases further to 15 in basin sediments results from the same geochemical measurements made with depth in gravity core 6705 7 from cascadia seachannel suggest that our approach to assess terrestrial organic carbon contributions to contemporary deposits on the washington margin can be applied to the study of sediments depositing in this region since the last glacial period

reply to discussion contribution by a elmas and e yigitbas on tectonic evolution of the intra pontide suture zone in the armutlu peninsula nw turkey by a h f robertson and t ustaomer tectonophysics 381 2004 175 209

sea surface temperatures in the subarctic northeast pacific reflect millennial scale climate oscillations during the last 16 kyrs changes of sea surface temperature sst in the subarctic ne pacific over the last 16 000 calendar years before present 16 kyr bp have been inferred from the study of c 37 alkenone unsaturation in a sediment core from the western canadian continental slope between 16 0 and 11 0 kyr three distinct cold phases 6 7 c interrupt two warmer periods 9 10 c within the 2 range of the radiocarbon based time control the observed sst oscillations correspond to the oldest dryas the bolling the older dryas the allerod and the younger dryas periods in the gisp2 18 o record these results represent the first high resolution marine paleotemperature estimates off the northern west coast of north america and imply that the climate of this region may be very strongly coupled to that of the north atlantic given the fast rates of sst change 1 c 40 80 yr such coupling must be controlled by atmospheric transmission of the climate signal

nitrogen isotope and productivity variations along the northeast pacific margin over the last 120 kyr surface and subsurface paleoceanography 1 glacial interglacial changes in sedimentary 15n over the last 120 kyr display a remarkably similar pattern in timing and amplitude in core records extending from the denitrification zone in the eastern tropical north pacific etnp where subsurface denitrification is active to the oregon margin where no denitrification occurs today low 15n values 4 6 generally characterize glacial stages 2 and 4 and higher 15n values 7 10 are representative of the holocene millennial scale periods within stage 3 and stage 5 the inferred synchroneity of 15n variations along the entire margin implies that the nitrate isotopic signal produced in the oxygen poor subsurface waters in the etnp is rapidly advected northward and recorded at sites far beyond the boundaries of the modern denitrification zone similar to 15n primary production indicators percent corg ba al and percent opal show glacial interglacial as well as millennial scale variations along the ne pacific margin with higher primary production during warm periods however the relative phasing between 15n and paleoproduction tracers within individual records changes latitudinally whereas 15n and primary production vary approximately synchronously in the midlatitudes production lags 15n in the etnp by several kiloyears this lag calls for a new understanding of the processes driving denitrification in the etnp we suggest that oxygen input by the equatorial undercurrent as well as local organic matter flux controls denitrification rates in the etnp moreover the differences in relative timing point to a time transgressive development of upwelling favorable winds along the ne pacific margin after the last glaciation with those in the north developing several kiloyears earlier

stratigraphic comparisons along the pontides turkey based on new nannoplankton age determinations in the eastern pontides geodynamic implications we compared the stratigraphic formations along the southern margin of the black sea using 196 nannoplankton ages determined in the western and central pontides and 112 new samples from the eastern pontides we inferred that the istanbul and sakarya zones were amalgamated prior to the early cretaceous extensional subsidence migrated eastwards along the pontides from the barremian to the palaeocene an eastwards younging of the cretaceous magmatism suggested that the eastern black sea basin is younger locally angular unconformities and a stratigraphic gap testify to the late albian uplift of the central pontides as the consequence of the collision of an oceanic edifice cretaceous oceanic red beds are marker beds of santonian age along the much of the pontides and are of mainly campanian age within the eastern pontides the middle campanian paleocene was a non volcanic period characterized by extensional subsidence mainly along the eastern black sea basin the end of cretaceous volcanism can be correlated with a southwards subduction jump syn compressional basins show that contraction started during the ypresian along the entire pontide belt eocene volcanism started earlier in the north lutetian than in the south bartonian of the eastern pontides this propagation of syn collisional volcanism could have resulted from slab steepening under the eastern pontides

does sedimentary organic δ13c record variations in quaternary ocean co2 aq ocean surface water co2 aq variations based on glacial interglacial changes in sediment delta 13corg are shown to compare favorably with reconstructions based on ice core co2 in particular an approximate 80 microatmospheres increase in atmospheric pco2 during the last glacial interglacial transition is calculated to correspond to a 3 4 micromolar increase in ocean surface water co2 aq at atmospheric equilibrium a widespread marine delta 13corg decrease of 1 2 accompanied this event and was not preceded by an equivalent isotopic change in surface water total dissolved inorganic carbon these observations support the hypothesis that co2 aq influences photosynthetic isotope fractionation between marine inorganic and organic carbon pools and therefore that plankton sediment delta 13corg may serve as a proxy for surface water co2 aq

the california current of the last glacial maximum reconstruction at 42 n based on multiple proxies multiple paleoceanographic proxies in a zonal transect across the california current near 42 n record modern and last glacial maximum lgm thermal and nutrient gradients the offshore thermal gradient derived from foraminiferal species assemblages and oxygen isotope data was similar at the lgm to that at present warmer offshore but average temperatures were 3 3 1 5 c colder observed gradients require that the sites remained under the southward flow of the california current and thus that the polar front remained north of 42 n during the lgm carbon isotopic and foraminiferal flux data suggests enhanced nutrients and productivity of foraminfera in the northern california current up to 650 km offshore in contrast marine organic carbon and coastal diatom burial rates decreased during the lgm these seemingly contradictory results are reconciled by model simulations of the lgm wind field which suggest that wind stress curl at 42 n and thus open ocean upwelling increased while offshore ekman transport and thus coastal upwelling decreased during the last ice age the ecosystem of the northern california current during the lgm approximated that of the modern gulf of alaska cooling and production in this region was thus driven by stronger open ocean upwelling and or southward flow of high latitude water masses rather than by coastal upwelling

a biomarker approach to the organic matter deposited in the north atlantic during the last climatic cycle abstract the study of the composition of total organic carbon toc c37 alkenones and c23 c33 n alkanes in the north atlantic ocean cores su90 08 and su90 39 has allowed the development of a model for the differentiation of marine and terrigenous toc this model gives rise to results in good agreement with inorganic markers such as magnetic susceptibility ms and non carbonate content according to this model the terrigenous toc accounts for most of the organic matter in the glacial sediments thus the higher toc of the glacial periods 0 1 0 45 vs 0 05 0 15 in the interglacials is due to the increase in terrigenous toc the changes in marine toc those associated to sea surface productivity are independent of the glacial interglacial evolution the terrigenous toc is more important at higher latitudes probably due to higher terrigenous detrital inputs associated with iceberg transport in this respect the correlation between n alkanes and ms strongly suggests that the main source of these hydrocarbons are ice rafted materials and that aeolian inputs only represent minor contributions the four peaks of reworked n alkanes in the su90 08 core that are coincident with the heinrich layers h1 h2 h4 and 115 are in agreement with this hypothesis on the other hand the abrupt marine toc peaks of su90 08 show a 23 ka periodicity indicating that the marine productivity at 43 n in the north atlantic ocean was precessionally driven the productivity maxima in this core correlate with low latitude oceanographic processes such as periods of enhanced trade wind intensity and equatorial upwelling which are also tuned to precession and independent of the global glacial interglacial evolution

tectonic evolution of the intra pontide suture zone in the armutlu peninsula nw turkey abstract the armutlu peninsula and adjacent areas in nw turkey play a critical role in tectonic reconstructions of the southern margin of eurasia in nw turkey this region includes an inferred intra pontide oceanic basin that rifted from eurasia in early mesozoic time and closed by late cretaceous time the armutlu peninsula is divisible into two metamorphic units the first the armutlu metamorphics comprises a precambrian high grade metamorphic basement unconformably overlain by a palaeozoic low grade mixed siliciclastic carbonate volcanogenic succession including bimodal volcanics of inferred extensional origin with a possibly inherited subduction signature the second unit the low grade iznik metamorphics is interpreted as a triassic rift infilled with terrigenous calcareous and volcanogenic lithologies including basalts of within plate type the triassic rift was unconformably overlain by a subsiding jurassic late cretaceous cenomanian passive margin including siliciclastic carbonate turbidites radiolarian cherts and manganese deposits the margin later collapsed to form a flexural foredeep associated with the emplacement of ophiolitic rocks in turonian time geochemical evidence from meta basalt blocks within ophiolite derived melange suggests a supra subduction zone origin for the ophiolite the above major tectonic units of the armutlu peninsula were sealed by a maastrichtian unconformity comparative evidence comes from the separate almacik flake further east considering alternatives it is concluded that a mesozoic intra pontide oceanic basin separated eurasia from a sakarya microcontinent with a wider northern neotethys to the south lateral displacement of exotic terranes along the south eurasian continental margin probably also played a role e g during late cretaceous suturing in addition to overthrusting

determination of the deep fault geometry along the southern branch of the north anatolian fault system by using resistivity and magnetic methods abstract the wenner lateral resistivity and magnetic dyke profiles carried out along the southern branch of the north anatolian fault system the use of magnetic dyke method indicates that the faults located in the deep parts of the continental crust were high angled and dipping towards north and the right lateral strike slip faults were the only active main fault types in the plio quaternary deposits besides a high angled strike slip fault and its secondary components form the geological contact between the basement rocks and the basin filling deposits nafs sb that is developed during plio quaternary neotectonic period is the only structural source during the formation of the deposits in the depression areas and recent times this zoning is related to nafs sb and developed depending on both the near vertical and 70 90 dipping strike slip faulting apart from the near vertical fault planes the faults dipping towards the depression areas developed due to the existence of the transtensional stresses in the strike slip faults

the early pleistocene praetiglian and ludhamian pollen stages in the north sea basin and their relationship to the marine isotope record in this paper the currently accepted correlation of the early pleistocene ludhamian stage of england with the tiglian a sub stage of the netherlands is challenged recent investigations of early pleistocene marine north sea deposits from a borehole near noordwijk the netherlands yielded evidence from molluscs dinoflagellate cysts and sporomorphs for an alternation of warm temperate and arctic intervals within the praetiglian and tiglian stages marine equivalents of the terrestrial based pollen sub stages tiglian a and b have been recognised in the upper part of the sequence a praetiglian age can be assigned to the lower part of the sequence on the basis of mollusc analysis within the praetiglian an alternation of warm and cold phases has been recognised from both the dinoflagellate cyst and molluscan records three cold phases within the praetiglian are tentatively correlated with marine isotope stages mis 96 100 the molluscan assemblages provide evidence for climate forcing of the sea level highest sea levels are reached in the warm temperate intervals within the praetiglian an interval with an acme zone of the dinoflagellate cyst impagidinium multiplexum is correlated with the ludhamian and tentatively linked to mis 97 and or mis 96 the cold molluscan assemblages from the noordwijk borehole include an acme zone of megayoldia thraciaeformis the first and only occurrence of this north pacific bivalve in the north sea basin copyright 2006 john wiley sons ltd

whole rock geochemistry zircon u pb and hf isotope systematics of the cangaldag pluton evidences for middle jurassic continental arc magmatism in the central pontides turkey abstract the central pontides turkey includes several igneous complexes which are predominantly permo carboniferous and middle jurassic in age the cangaldag pluton is one of the largest igneous bodies located in the northern central pontides whose age and tectono magmatic evaluation is important to constrain the geological evolution of the northern neotethys the pluton tectonically overlies the cangaldag metamorphic complex which represents an arc back arc complex of middle jurassic age the cangaldag pluton consists mainly of non metamorphic gabbroic diorite dacite porphyry and lesser amount of granitic rocks geochemically the various rock types are akin to volcanic arc magmas displaying th nb and light rare earth element heavy rare earth element enrichments in situ u pb age results of zircons from dacite porphyry and granite samples yield ages of 161 5 ma and 170 2 ma respectively corresponding in situ average 176hf 177hf initial ratios are 0 28287 0 00004 and 0 28213 0 00002 for the dacite porphyry and granite samples respectively these results are consistent with derivation from a subduction modified mantle source based on hf isotope compositions tdm model ages vary between 624 and 1512 ma and suggest that the arc magmatism associated with the cangaldag pluton may have involved partial melting of neoproterozoic mesoproterozoic crustal rocks a common feature in gondwana derived terranes the geochemical hf isotope and geochronological data reported here confirm the presence of a continental arc system during the middle jurassic in the central pontides and suggests that the cangaldag pluton formed during northward subduction of the intra pontide branch of the northern neotethys

paleoproductivity and carbon burial across the california current the multitracers transect 42 n the multitracers experiment studied a transect of water column sediment trap and sediment data taken across the california current to develop quantitative methods for hindcasting paleoproductivity the experiment used three sediment trap moorings located 120 km 270 km and 630 km from shore at the oregon california border in north america we report here about the sedimentation and burial of particulate organic carbon corg and caco3 in order to observe how the integrated caco3 and corg burial across the transect has changed since the last glacial maximum we have correlated core from the three sites using time scales constrained by both radiocarbon and oxygen isotopes by comparing surface sediments to a two and a half year sediment trap record we have also defined the modern preservation rates for many of the labile sedimentary materials our analysis of the corg data indicates that significant amounts 20 40 of the total corg being buried today in surface sediments is terrestrial at the last glacial maximum the terrestrial corg fraction within 300 km of the coast was about twice as large such large fluxes of terrestrial corg obscure the marine corg record which can be interpreted as productivity when we corrected for the terrestrial organic matter we found that the mass accumulation rate of marine corg roughly doubled from the glacial maximum to the present because preservation rates of organic carbon are high in the high sedimentation rate cores corrections for degradation are straightforward and we can be confident that organic carbon rain rate new productivity also doubled as confirmation the highest burial fluxes of other biogenic components opal and ba also occur in the holocene productivity off oregon has thus increased dramatically since the last glacial maximum caco3 fluxes also changed radically through the deglaciation however they are linked not to caco3 production but rather to changes in deepwater carbonate chemistry between 18 ka and now

glacial climate instability in the northeast pacific ocean recent climate records from greenland ice cores1 2 and north atlantic sediments3a 5 have challenged the long held notion that pleistocene climate fluctuates between two relatively stable states glacials and interglacials it has been appreciated for some time that the transitions from one state to another are not smooth6 but the new records indicate that the glacial and interglacial periods themselves appear to be punctuated by significant climate variability several short interstadial events punctuated the last glacial period for example but it has not been clear whether this climate instability is a global phenomenon or is peculiar to the north atlantic region here we present climate proxy records from sediment cores from the eastern margin of the north pacific ocean which indicate that climate in this region was also highly unstable during the last glaciation our observations suggest that glacial climate instability throughout the northern hemisphere might be linked to rapid changes in the size of the laurentide ice sheet and associated changes in atmospheric circulation

nitrogen isotopic variations in the gulf of california since the last deglaciation response to global climate change high resolution records of the nitrogen isotopic composition of organic matter 15norg opal content and opal accumulation rates from the central gulf of california reveal large and abrupt variations during deglaciation and gradual holocene changes coincident with climatic changes recorded in the north atlantic homogenous sediments with relatively low 15norg values and low opal content were deposited at the end of the last glacial period during the younger dryas event and during the middle to late holocene in contrast laminated sediments deposited in the two deglacial stages are characterized by very high 15norg values 14 and opal accumulation rates 29 41 mg cm 2 yr 1 abrupt shifts in 15norg were driven by widespread changes in the extent of suboxic subsurface waters supporting denitrification and were amplified in the central gulf record due to variations in upwelling vertical mixing and or the latitudinal position of the intertropical convergence zone

surface area control of organic carbon accumulation in continental shelf sediments the relationship between organic carbon oc and grain size found in most continental shelf sediments is here reinterpreted in terms of the surface area of the sediments cores from many north american shelf environments show downcore decreases in oc to similar refractory background concentrations if expressed relative to the surface area of the sediments this consistent concentration is 0 86 mg oc m 2 which is equivalent in concentration to a monolayer of organic matter coating all mineral surfaces a more global collection of sediment water interface samples show that this relationship is even more extensive with exceptions occurring in areas of very high riverine sediment input organic pollution or low oxygen water columns density separations indicate that organic matter is largely adsorbed to mineral grains the microtopography of surfaces was examined with n2 sorption and most surface area was found to be inside pores of 10 nm width these data lead to a hypothesis that organic matter is protected by its location inside pores too small to allow functioning of the hydrolytic enzymes necessary for organic matter decay such protection would likely work in concert with other protection mechanisms such as humification this consistent surface area correlation with oc concentration may explain control of spatial and temporal variations in oc burial rates by sedimentation rates the pore protection hypothesis provides a causal mechanism for this observed control