a gradual drowning of the southwestern black sea shelf evidence for a progressive rather than abrupt holocene reconnection with the eastern mediterranean sea through the marmara sea gateway core m02 45 recovered 9 5 m of a 12 m thick transgressive succession on the sw black sea shelf the underlying transgressive unconformity a deepens toward the shelf edge so that the coresite was never isolated from the open black sea fourteen radiocarbon dates indicate sedimentation from 9 3 ka to the present with only one hiatus at 270 cm depth spanning 4 5 2 5 ka three units are present in the core unit a 0 270 cm burrowed mud with laminated silt beds and mollusc shells of mediterranean affinity accumulation rate 125 cm ky unit b 270 525 cm silty mud with shelly interbeds containing truncatella subcylindrica mytilus galloprovincialis parvicardium exiguum rissoa spp and modiolula phaseolina rate 85 cm ky unit c 525 950 cm burrowed silty mud with graded beds of silt and fine sand and shells of t subcylindrica p exiguum and dreissena polymorpha rate 360 cm ky unit c developed below storm wave base at a time when proponents of a catastrophic flood in the black sea claim that the shelf was subaerially exposed clearly it was not ostracoda of caspian affinity indicate 5 salinity until 7 5 ka dinocysts and foraminifera confirm a low but rising salinity after 8 6 ka an increase of d 34 s from 5 30 through 8 4 7 6 ka is attributed to a first pulse of sulfate rich aegean water into an already high black sea after which this sulfate was quantitatively precipitated as sulfide d 34 s then dropped at 8k a to 20 as dysoxia and water column stratification were established because of the initiation of two way flow through the bosphorus earlier water exchange with the mediterranean was likely impeded by strong black sea outflow which prevented easy access of the aegean water mass r 2006 published by elsevier ltd

sedimentary pyrite formation an update sedimentary pyrite formation during early diagenesis is a major process for controlling the oxygen level of the atmosphere and the sulfate concentration in seawater over geologic time the amount of pyrite that may form in a sediment is limited by the rates of supply of decomposable organic matter dissolved sulfate and reactive detrital iron minerals organic matter appears to be the major control on pyrite formation in normal non euxinic terrigenous marine sediments where dissolved sulfate and iron minerals are abundant by contrast pyrite formation in non marine freshwater sediments is severely limited by low concentrations of sulfate and this characteristic can be used to distinguish ancient organic rich fresh water shales from marine shales under marine euxinic conditions sufficient h2s is produced that the dominant control on pyrite formation is the availability of reactive iron minerals calculations based on a sulfur isotope model indicate that over phanerozoic time the worldwide average organic carbon to pyrite sulfur ratio of sedimentary rocks has varied considerably high cs ratios during permo carboniferous time can be explained by a shift of major organic deposition from the oceans to the land which resulted in the formation of vast coal swamps at that time low cs ratios compared to today during the early paleozoic can be explained in terms of a greater abundance of euxinic basins combined with deposition of a more reactive type of organic matter in the remaining oxygenated portions of the ocean the latter could have been due to lower oceanic oxygen levels and or a lack of transportation of refractory terrestrial organic matter to the marine environment due to the absence of vascular land plants at that time

the metagabbros orthogneisses and paragneisses of the connemara complex western ireland although now largely disappeared within the 400 ma old galway granite the syntectonic connemara metagabbro gneiss complex which crystallized at 490 ma arenig is the largest intrusion into the dalradian rocks it is part of widespread cambro ordovician volcanism and plutonic injection into continental crust in the appalachian caledonide orogenic belt being synchronous in crystallization with the widely obducted 490 ma ophiolites within the orogeny the peridotites and hornblende gabbros were injected broken up and shouldered aside by quartz diorite granodiorite granite and trondhjemite gneisses and it is shown that these orthogneisses are not the in situ differentiation products of the gabbro magma the hornblende in the metagabbros is mainly igneous but is partly metamorphic and replaces olivine fo 75 92 orthopyroxene en 65 92 clinopyroxene wo 48 5 en 50 39 fs 5 14 and plagioclase typically an 80 92 range an 50 96 an aureole at least 10 km wide in the sillimanite zone was imposed and cordierite garnet sillimanite dalradian hornfelses were partially melted at temperatures up to 1000 o c near to the gabbros at 4 5 1 kbar corresponding to c 18 km depth this suggests that the complex forms part of the root of a now eroded batholith of calc alkaline affinities the gabbros corresponding to the transition zone to a basic bottom which is often supposed to underlie many batholiths within the orthogneisses are sheets of paragneiss formed from dalradian metasediments which have been folded up from the floor and down into sides of the magma chamber which process could be illustrative of the means by which basic magma can intimately interact with crustal material the 18 o 16 o d h nd and sr isotope evidence and the existence of inherited zircons in the gneisses indicate that the gabbro and gneiss magmas were significantly contaminated with crustal possibly dalradian material both before and after intrusion with the lowest initial 87 sr 86 sr at 490 ma being 0 708 even in samples far removed from metasediment the metagabbros are tholeiitic to high alumina basalt in character but the gneisses have distinct calc alkaline geochemistry the chemistry igneous hornblende and highly calcic plagioclase match many arc plutons in the western usa the syntectonic nature and the ubiquitous gneissic fabric in the quartz diorites trondhjemites and granites is a consequence of early movements which were probably in part connected with the separation of the connemara massif and which culminated in slicing off the largely inverted complex and carrying it southwards on the mannin thrust which underlies the whole of connemara the complex is thus a fragment of a now disrupted cambro ordovician continental magmatic arc or continent island arc environment which can be traced along the se edge of the laurentian continent

occurrence stratigraphy and geochemistry of late quaternary tephra layers in the aegean sea and the marmara sea abstract several discrete tephra layers occur in 2 5 10 3 m long cores from the aegean sea whereas a single tephra is identified in 3 5 9 7 m long cores from the marmara sea major and trace element data on these tephras delineate eight distinct groups the geochemical data and multivariate statistics allow the correlation of the tephra layers with six previously described marine tephras from the eastern mediterranean sea potential terrestrial sources are suggested for the others the chronostratigraphy of the tephra layers was established using several radiocarbon dates and the oxygen isotope stratigraphy from two long piston cores four widespread tephra layers occur within the upper quaternary sediments of the aegean sea the two youngest widespread tephra layers were derived from the santorini volcano of south central aegean sea z2 the minoan eruption ca 3 6 ka and y2 the cape riva eruption ca 21 7 ka the y2 tephra is also identified in three piston cores from the marmara sea the two older widespread tephra layers originated from the eruptions which emplaced the campanian ignimbrite of the italian volcanic provinces i e the y5 tephra ca 39 3 ka and from the nisyros volcano of the southeastern aegean sea the consistent occurrence of the nisyros tephra below the y5 tephra confirms similar findings in a lake core on the island of lesbos linear extrapolations using the oxygen isotope stratigraphy suggest an age of 42 44 ka for the nisyros eruption three additional tephra layers with a limited regional distribution are identified in the aegean sea cores two of these tephras originated from the yali volcano of the southeastern aegean sea and from the aeolian islands i e x1 tephra a series of six mugearite tephra beds in the south skiros basin is interpreted as a set of redeposited turbidites

geological significance of 40ar 39ar mica dates across a mid crustal continental plate margin connemara grampian orogeny irish caledonides and implications for the evolution of lithospheric collisions1 the connemara region is a world class example of a regional scale high temperature metamorphic terrain its rock record documents formation of a bi vergent orogenic wedge and associated calkalkali

basic magmatism in connemara ireland evidence for a volcanic arc it is found by the use of pearce cann diagrams that basic magmatism during dalradian sedimentation in connemara was of a fundamentally different type to that which led to later synorogenic basic intrusions the dalradian magmatism is of a transitional within plate to divergent plate margin type whereas the synorogenic intrusions are of volcanic arc type it is suggested that the synorogenic basic intrusions of connemara tyrone and ne scotland represent the roots of a volcanic arc that developed by arenig times over a northerly directed subduction zone

the geology of sw connemara ireland a fold and thrust dalradian and metagabbroic gneiss complex sillimanite grade dalradian schists composed of pelites impure psammites quartzites and calcite marbles all containing amphibolites were intruded and hornfelsed giving hornfels sillimanite garnet and cordierite by a plutonic basic to acid igneous rock series now metamorphosed and folded important folding denoted d 2 d 3 d 4 and d 5 as been recognized with a major southward facing d 2 anticline the cashel antiform being repeatedly folded by d 3 which was a very strong phase and accompanied and followed by d 3 d 4 major ductile slides and thrusting although the meta igneous suite includes rare peridotites olivine fo 75 87 and anorthosites it is mostly hornblende augite labradorite or bytownite metagabbro and later quartz diorite or trondhjemite gneiss which has injected the earlier more basic rocks variably preserved igneous layering in the basic rocks indicates that the whole intrusive basic sheet is flat lying and inverted lying on the inverted limb of the cashel antiform about 460 ma ago the d 3 d 4 mannin thrust carried the igneous complex including the largely crystallized gneisses and the cover of dalradian metasediment over a now largely mylonitized set of acid volcanic rocks rhyolites or ignimbrites which enclose a separate suite of massive amphibolites intruded or extruded into the acid volcanic rocks before the thrusting the base of the overthrust metagabbro sheet which had cooled to albite epidote amphibolite facies conditions was ground down into a fine grained nnw lineated amphibolite the volcanic rocks the mannin thrust and the overlying basic complex were folded by d 4 and d 5 into a domed structure about 400 ma the aplopegmatitic facies of the inish granite intruded and caused hornfelsing and folding while the galway granite was intruded in the south lamprophyric sills and dykes and porphyry dykes were followed by the final phase of the inish granite the southward facing folding and thrusting of the connemara dalradian block and the gabbro gneiss emplacement are major elements in the caledonide history of the british isles it is postulated that there was a tectonic and genetic connection between the gabbro gneiss intrusion into these dalradian rocks the unusually rapid decrease in metamorphic pressure already documented for connemara and the exceptionally southern position of the connemara block

uranium and radium diffusion in organic rich sediments sapropels among the late quaternary mediterranean sapropels the s5 125 ka is one of the best preserved due to its high organic carbon content that has limited postdepositional oxidation the high uranium content in this sapropel 40 dpm g 1 makes this layer interesting for studying uranium series disequilibrium in organic rich sediments for this reason the present work provides isotopic measurements of the u decay series in a s5 sapropel by applying more precise mass spectrometric methods tims mc icpms and gamma spectrometry assuming that u in the sapropel mostly originated from seawater the 234u 238u 230th 238u 226ra 230th and 231pa 235u activity ratios show systematic deviations from the theoretical values for a closed system evolution of the u series over the 125 ka since sapropel formation the radiogenic 234urad and 226ra show clear evidence of migration in the sapropel with modeled diffusion coefficients of 7 1 1 1 10 12 cm2 s 1 and 1 6 0 2 10 10 cm2 s 1 respectively the diffusion of 234urad cannot explain the high 230th 238u and 231pa 235u activity ratios observed in the sapropel two possible mechanisms or a combination of both are proposed for explaining the irregular 230th 238u and 231pa 235u activity profiles in sapropel s5 the first one is an enhanced export flux of 230thxs and 231paxs excesses exceeding the production rate in seawater during the time of sapropel formation and the second one is diffusion of authigenic uauth in the sapropel however the ambiguous determination of 230thxs and 231paxs in the sapropel and the poorly understood processes that might lead to uauth migration in anoxic sediments still limit a final explanation for the deviation of 230th 238u and 231pa 235u activity ratios from their expected theoretical values

geochronological constraints on the magmatic metamorphic and thermal evolution of the connemara caledonides western ireland the connemara region of the western irish caledonides records the evolution of a short lived mid ordovician c 475 463 ma continental magmatic arc that intruded into dalradian metasedimentary rocks during regional ductile deformation new u pb geochronological data for intermediate intrusive phases and anatexis in southern connemara are consistent with the relative age succession suggested by field relationships calc alkaline plutons quartz diorites were emplaced into the dalradian sequence and into the connemara gabbros at about 467 2 ma coeval with anatexis which was manifested by a 467 2 ma granitic pegmatite and 468 2 ma leucosome formation in a metapelite metasomatic diopside rocks from west central connemara and a calcsilicate rock from southern connemara yield u pb titanite dates of c 462 2 ma and 463 2 ma respectively these dates postdate the metamorphic peak by at least five million years and indicate titanite crystallization at a late stage during the metamorphic history on the basis of u pb and 40 ar 39 ar geochronological data we conclude that the cooling history of southern connemara following anatexis was simple and brief at a minimum rate of 35 c ma 1 between 468 and 460 ma and 14 c ma 1 between 460 and 450 ma

late pleistocene holocene evolution of the northern shelf of the sea of marmara abstract chirp sub bottom profiling multibeam bathymetric mapping and a combination of faunal and isotopic analysis of molluscs and foraminifera in sediment cores on the northern shelf of the sea of marmara som provide evidence of sea level excursions water exchanges between the adjacent mediterranean and black seas and oscillating salinity over the last 160 ka bp during the marine isotope stages mis 2 mis 3 mis 4 and mis 6 the som disconnected from the mediterranean sea and evolved into a lake during mis 1 mis 5 and mis 7 the som reconnected and became salty once again sapropels formed shortly after each invasion of mediterranean saltwater observed in our cores concurrent suboxic dysoxic conditions prevailed over quite shallow substrates on the shelf ancient shorelines are pervasive at 85 m on the northern shelf and in the region of prince islands coincident with the elevation of the modern bedrock sill in the canakkale dardanelles strait at times when global eustatic sea level dropped below this sill the surface of the som stabilized at its outlet and freshened thus this particular shoreline is interpreted as the edge of the most recent som lake that existed from about 75 ka bp to 12 ka bp the freshening is observed in very light 6 values of 18 o measured on freshwater molluscs and the complete absence of foraminifera two brief lacustrine episodes during mis 5 suggest that the level of the canakkale outlet might have been as shallow as 50 m in the past a likelihood supported by submerged terraces along its margins bounding the modern central channel and the presence of an euryhaline biofacies in unit l4 1 corresponding to mis 5b 18 o profiles and carbon 14 dating show that salinification of the som and the blossoming of bioherms evolved rapidly after the latest connection with the mediterranean at 12 ka bp however freshening proceeded more slowly once the connection was severed

organic rich layers in the metochia section gavdos greece evidence for a single mechanism of sapropel formation during the past 10 my abstract three well developed 10 ma old sapropels from the island of gavdos greece were selected for a detailed geochemical micropaleontological and sedimentological study the sapropels are characterized by a high organic carbon and a low carbonate content productivity was higher during sapropel formation as indicated by increased ba contents and higher percentages of the planktonic foraminiferal species neogloboquadrina acostaensis enrichment of mo and v in the sapropels indicates less oxygenated bottom water conditions which is supported by the flourishing of low oxygen tolerant benthic foraminifera variation in grainsize and the ti al ratio point to an alternating dominance of fluvial sapropels and eolian derived homogeneous intervals terrigenous clastics evidence for a local origin of the enhanced fluvial input comes from the gradual replacement of the sapropels by cyclic turbidite sequences which were fed by bed load type rivers the increased fluvial input during sapropel formation increased the sedimentation rate and caused the observed carbonate depletion the results obtained for the gavdos sapropels are consistent with those of previous studies of younger sapropels and related caco 3 cycles in the mediterranean the consistency in most of the geochemical and micropaleontological characteristics indicates that all sapropels and related layers are the result of a single mechanism for at least the past 10 my namely precession induced dry wet oscillations in the mediterranean climate still the effect of this mechanism on the intensity of surface water productivity dilution and diagenetic signals may differ from site to site depending on location depositional environment and intensity of the astronomical forcing

late quaternary history of the marmara sea and black sea from high resolution seismic and gravity core studies abstract lithologic and multi proxy paleoenvironmental data from 21 dated cores have been used to define three allostratigraphic units allounits within the late quaternary successions of the marmara sea and black sea allounits are bounded by unconformities and their correlative conformities in both regions allounit a extends from the seafloor downward to a 12 11 ka sequence boundary which is a major shelf crossing unconformity in water depths less than 100 110 m in deep basins of the marmara sea the lower part of allounit a designated subunit a2 is a laminated sapropel m1 on the shelf subunit a2 consists of backstepping delta lobes and early transgressive barrier islands and sand sheets allounit b has only been recovered in marmara sea cores collected at water depths greater than 90 m and represents basinal or prodeltaic deposition during the 23 12 ka late pleistocene lowstand during the last glacial maximum the shelves surrounding the marmara sea were subaerially exposed and deltas of allounit b accumulated along the present day shelf edge following the post glacial rise of global sea level to 75 m at 12 ka the marmara sea quickly became inundated and thereafter rose in synchroneity with the mediterranean by 10 ka the black sea rose to start spilling into the marmara sea leading to establishment of a brackish water lid that has persisted to the modern day the strongest black sea outflow began at 10 ka and persisted to 6 ka promoting the accumulation of sapropel m1 in the deep marmara sea and progradation of an overflow delta just south of the exit from the bosphorus strait allounit c is a laminated sapropel m2 in basinal cores dated at 30 23 ka like m1 it is believed that m2 accumulated during a period of increased brackish water input into the marmara sea mainly from the black sea in the black sea wave erosion kept the shelf stripped of unconsolidated sediments during the falling sea level associated with the last glaciation and subsequent early stages of the post glacial holocene transgression this erosion created a major unconformity shelf edge deltas of allounit b received their sediment during the last lowstand from small rivers that likely coalesced into a single system toward the shelf edge at modern water depths of 100 to 110 m these deltas were active until 11 10 5 ka subsequently sea level in the black sea rose to 40 m by 10 ka and a set of backstepping barrier islands developed on the shelf as part of the associated transgressive systems tract once water level reached 40 m continued sea level rise stalled until 9 ka as the black sea began to spill across the bosphorus strait into the marmara sea

synthesis of staurolite in melting experiments of a natural metapelite consequences for the phase relations in low temperature pelitic migmatites we document experiments on a natural metapelite in the range 650 775 c 6 14 kbar 10 wt of added water and 700 850 c 4 10 kbar no added water staurolite systematically formed in the fluid present melting experiments above 675 c but formed only sporadically in the fluid absent melting experiments the analysis of textures phase assemblages and variation of phase composition and fe mg partitioning with p and t suggests that supersolidus staurolite formed at near equilibrium during fluid present melting reactions the experimental results are used to work out the phase relations in the system k2o na2o feo mgo al2o3 sio2 h2o appropriate for initial melting of metapelites at the upper amphibolite facies the p t grid developed predicts the existence of a stable p t field for supersolidus staurolite that should be encountered by aluminous fe rich metapelites during fluidpresent melting at relatively low temperature and intermediate pressures 675 700 c 6 10 kbar for xh2o 1 in the knfmash system but not during fluid absent melting the implications of these findings for the scarcity of staurolite in migmatites are discussed

geochemistry of dalradian pelites from connemara ireland new constraints on kyanite genesis and conditions of metamorphism whole rock and mineral analyses of dalradian pelites from w connemara show that kyanite pelites are not unusually mg rich as previously supposed their chemistry is transitional especially in ca content between overlying fe rich staurolite pelites and underlying ca rich rocks the flysch basin in which they were deposited was established relatively early in the west its sediment fill including carbonate rich influxes derived from an adjacent swell to the east which later subsided to form an enlarged basin kyanite has a very restricted spatial distribution because its development was controlled by fe deficiency associated with the carbonate rich influxes which in turn led to relatively high x mg during metamorphism p t estimates for the metamorphic peak are 650 25 c and 8kbar about 50 c and 3kbar greater than for similar rocks in the east the difference can be related to structural level with respect to regional scale folds which may have developed as a huge backfolded complex during the emplacement of the connemara allochthon

modelling of the thermal history of metamorphic zoning in the connemara region western ireland abstract the connemara region of the irish caledonides is a classic example of regional scale metamorphism of low pressure and high temperature this terrane is considered as part of a fold belt comprising metasedimentary and metavolcanic rocks that are correlated with the neoproterozoic lower paleozoic dalradian supergroup of scotland in mid ordovician time the extensive and high temperature metamorphism was superimposed on the dalradian rocks resulting in the connemara zoning the key feature of the zoning is elevated horizontal thermal gradient of ca 14 c km geological data and geochronological evidence point to a causative link between metamorphism and associated magmatic intrusions and a brief period of development for the metamorphic zoning magmatic intrusion into the middle part of continental crust is treated as a most plausible source of heat for metamorphism and other conjectures as to the origin of the zoning flow of hot fluid through the permeable rocks fracture conduit flushed by flowing magma are believed to be improbable to examine in sufficient detail the problem of the nature of heat source a series of appropriate calculations have been performed to reach the best agreement between the observed and simulated spatial distribution of maximum temperatures at different times the mathematical modelling shows that the temperature spatial structure of the connemara zoning is best explained by the model version based on mid crustal heating above the upper contact of magmatic intrusive body gently curved and tilted at an angle between 20 and 40 with an initial temperature of the magma appropriate to a basaltic melt the model estimate of total lifetime of the temperature anomaly in the crust is of the order of 5 6 ma in general this is in rather good agreement with the currently available evidence of geochronological duration of metamorphism and magmatism in connemara

determination of inorganic sulphur speciation with polarographic techniques some preliminary results for recent hypersaline anoxic sediments abstract polarographic techniques have been used to determine reduced inorganic sulphur speciation in recent anoxic marine sediments from two hypersaline basins the tyro and the bannock basins in the eastern mediterranean the following phases were determined acid volatile sulphur avs pyritic sulphur and zerovalent sulphur the determination of avs and pyrite was based respectively on the acidification and cr ii reduction of these sulphur components to h2s h2s was collected in base and the sulphide concentration was measured by polarography standard na2s and pyrite gave recoveries of 99 6 3 9 and 97 12 respectively total zerovalent sulphur in a sediment sample was measured by the reaction of sulphite with thiosulphate thiosulphate was measured directly by polarography pyrite is the main phase of inorganic reduced sulphur in the sediments from the tyro and the bannock basins and it has about the same average level 125 moles per gramme dry weight in the cores recovered from the two areas however the distribution of pyrite in the top 100 cm of the two cores differs significantly in the bannock basin a sharp increase is observed with depth whereas in the tyro basin there is a small decrease with depth the total amount of reduced inorganic sulphur is less than the total amount of sulphur in the sediments this indicates that there must be additional sulphur bearing phases one of these phases may be gypsum and indeed gypsum crystals have been observed in the bannock basin in neither basin is there a significant correlation between reduced sulphur and organic carbon the pyrite that occurs in these basins may have been formed syngenetically at the interface of the anoxic brine and oxic seawater diagenetic pyrite may have been formed within the sediments of the basins avs and total zerovalent sulphur are still observed at depth we therefore suggest that this may be due to the incomplete transformation of avs and zerovalent sulphur into pyrite

late glacial holocene paleoclimatic and paleoceanographic evolution of the aegean sea micropaleontological and stable isotopic evidence abstract late glacial to holocene paleoclimatic and paleoceanographic changes are examined using records of calcareous and organic walled marine microfossils pollen and terrestrial spores and oxygen isotope data in cores from the aegean sea basins planktic foraminiferal coccolith and dinoflagellate data show that the late glacial holocene transition in the region was associated with a large warming of surface water mediterranean based paleotransfer functions for planktic foraminifera show a 5 10 c increase in surface water temperature from 14 000 to 9600 yr b p estimates of surface water oxygen isotopic composition 18 o w derived from planktic foraminiferal oxygen isotopic and transfer function data indicate that this warming was associated with a 2 0 to 2 5 reduction in 18 o w transfer function results indicate corresponding 1 0 to 1 5 salinity reductions for this tim ca 6400 9600 yr b p throughout the aegean sea pollen dinoflagellate and isotopic data show that the early holocene excess fresh water originated from rapid melting of the northern european and siberian ice sheets supplied primarily from the black sea by the opening of bosphorus and dardanelles channels during the post glacial sea level rise and supplemented by major rivers entering the aegean sea continuous outflow of fresh water into the aegean sea provided a low salinity surface lid preventing the ventilation of the deep water benthic foraminifera shows a major turn over that indicates low dissolved oxygen however bottom waters were not anoxic sapropel level s1 resulted from a combination of stagnant deep water in isolated depressions increased terrigenous organic matter and periods of high primary productivity as indicated by pollen and dinocysts respectively the surface water temperature and salinity reached present day values at 6400 yr b p with little subsequent change despite the major deforestation onshore

the sea of marmara during marine isotope stages 5 and 6 abstract multi proxy analyses and lithology of two cores mrs cs18 and mrs cs27 from the imrali basin of the sea of marmara som provide novel information on environmental conditions relative sea level and sill depths of the straits of bosporus and dardanelles during the marine isotope stages mis 5 and 6 the fossil and multi proxy geochemical records show that lacustrine conditions prevailed in the som during most of mis 6 from 171 to 134 ka bp and that the transition to marine conditions during termination ii took place at 134 06 1 10 ka bp mis 5 interstadials a c and e witnessed the formation of three sapropels msap 2 msap 3 and msap 4 under suboxic to anoxic marine conditions whereas during stadials mis 5b 94 86 and mis 5d 112 105 ka bp lacustrine and marine conditions with deposition of sediments having relatively low toc contents the som geochemical proxy records correlate well with the regional terrestrial and marine records and the ngrip oxygen isotope record with its stadial and interstadial phases showing the common effect of the north atlantic climatic events triggered by the perturbations in the atlantic meridional overturning circulation however the amplitude of the oscillations recorded in the som during mis 6 penultimate glacial period is relatively small compared to the mis 4 to mis 2 last glacial period

the cooling history of connemara western ireland from k ar and rb sr age studies k ar age determinations are reported on 26 hornblendes 17 coexisting muscovites and biotites nine muscovites and nine biotites from the dalradian connemara schists metagabbros and gneisses these are supplemented by 19 rb sr whole rock mica ages and four 40 ar 39 ar incremental heating ages on micas a long at least 75 ma and complex cooling history without a simple pattern of ages has been obtained the ages are not correlated with the grain sizes or the chemical compositions of the analysed minerals or the topographic elevation from which the samples came but there is an irregular increase of hornblende k ar ages to 480 10 ma with increase of metamorphic grade southwards towards the metagabbros and gneiss the preservation of the complex cooling pattern is ascribed to the action of syn and post metamorphic slides or faults which moved slices of the massif upwards by varying amounts closely spaced samples give results which rule out simple tilting of the massif rapid cooling c 30 ma 1 at 480 10 ma arenig llanvirn during the f3 fold phase was followed by slower cooling until 455 10 ma caradoc when renewed rapid uplift occurred possibly correlated with the southward thrusting of connemara and with synchronous renewed uplift in the scottish dalradian rocks widespread biotite k ar and rb sr ages of 440 5 ma end ordovician throughout connemara and the dalradian rocks of scotland are ascribed to the major taconic tectonic event which docked the dalradian rocks against the flanking folded ordovician successions of the midland valley and the south mayo trough biotites giving k ar ages of about 415 ma may have been reset during the late silurian folding of the cover rocks the importance of very close sampling integrated with structural studies is emphasized

glacial holocene salinity changes in the mediterranean sea hydrographic and depositional effects oxygen isotope changes as recorded by pleistocene foraminifera from open ocean sediments are primarily a function of changes in the isotopic composition of the global seawater reservoir caused by ice volume changes with a secondary temperature component1 oxygen isotope records from marginal basins such as the gulf of mexico2 the mediterranean sea3 5 and the red sea6 also exhibit the global signal but are far more complicated owing to the strong overprint of local climate conditions in particular glacial interglacial changes in continental aridity and river runoff produce significant salinity changes in these semi enclosed basins using available oxygen isotope records we estimate that glacial 18 000 yr bp salinities in the eastern and western mediterranean sea were 2 7 and 1 2 higher respectively than at present these elevated glacial salinities played an important part in preconditioning the eastern mediterranean for the eventual accumulation of organic carbon rich sediments sapropels at the end of deglaciation

the influence of microhabitats on the carbon isotopic composition of deep sea benthic foraminifera we report 13c and 18o values for rose bengal stained benthic foraminifera from a set of box cores from continental margin environments in the atlantic and pacific oceans these isotopic results are compared with foraminiferal distribution data and pore water 13c profiles to evaluate the importance of environmental microhabitat effects on the carbon isotopic composition of benthic foraminifera the 13c values of infaunal taxa are consistently lower than those of epifaunal taxa suggesting that microhabitat effects on test composition do exist the 13c differences between foraminiferal carbonate and bottom water dissolved inorganic carbon are not correlated with the 18o differences between benthic foraminifera tests and equilibrium calcite but they do correlate with variations in the chemistry of sediment pore waters however interspecific 18o differences as well as 13c differences between species with similar vertical distributions in the sediments indicate that taxon specific vital effects also influence test composition

an authigenic calcite layer in the sediments of the sea of marmara a geochemical marker horizon with paleoceanographic significance abstract three sediment cores taken from the central sea of marmara were sedimentologically and geochemically investigated all the cores show a continuous sedimentation record according to isotopic age dating measurements two of the cores cover an age range of more than 20 000 years since the sea of marmara was an isolated lacustrine system during the last glacial maximum about 20 ka bp the two cores should include the transition from lacustrine to marine environmental conditions the third core has a very high sedimentation rate 70 cm ka and therefore does not reach the transitional section in two cores however a very calcite rich layer unit c was observed carbon isotope investigations show that this calcite is not of diagenetic or biogenic origin but may represent a direct inorganic precipitate out of a deepwater layer in order to prove this hypothesis we used a geochemical model based on thermodynamic calculations this model shows that the calcite precipitation can only be explained by mixing of anoxic deep lacustrine water with oxic marine mediterranean water the necessary aqueous conditions are also obtained the model presented thus provides an important contribution to the evolution of the sea of marmara during the transition from lacustrine to marine conditions the thickness of the unit c layer indicates that this environmental change lasted approximately 1 5 ka

aspects of carbon isotope biogeochemistry of late quaternary sediments from the marmara sea and black sea abstract the marmara sea is situated between the world s largest permanently anoxic basin the black sea and an enclosed marginal sea the aegean sea which experienced quasi periodic sapropel deposition since miocene time it is connected to the black sea and the aegean sea through the straits of bosphorus and dardanelles respectively sapropel m1 which contains from 1 to 2 total organic carbon was deposited in the marmara sea between 6 and 10 5 ka we inferred the carbon isotopic composition of dissolved inorganic carbon dic in the water column of the marmara sea before during and after the deposition of sapropel m1 from the carbon isotopic composition of a planktonic foraminifera turborotalita quinqueloba and individual hexadecanoic and octadecanoic fatty acids the period of sapropel deposition is marked by a depletion of 13 c in the water column dic contrary to what may be expected if sapropel deposition represents a period of enhanced primary productivity instead we propose that both the relative 13 c depletion of dic during sapropel deposition and the absolute values we estimated 13 c 13 to 14 are consistent with enhancement of the relative contribution of 13 c depleted respired carbon to the water column dic pool such enhancement possibly resulted from density stratification that existed during sapropel m1 deposition the existence of density stratification is also argued from palynological and other lines of evidence other papers in this issue and is believed to have resulted from the encroachment of black sea water into the sea of marmara before 10 000 yr ago thus sapropel m1 appears to have formed during periods of enhanced runoff and preservation and not enhanced primary productivity

isotopic evidence of sea surface freshening enhanced productivity and improved organic matter preservation during sapropel deposition in the tyrrhenian sea multiple layers of sapropels occur widely in the sedimentary record of the mediterranean sea and record repetitions of paleoclimatic conditions that favored increased production and preservation of marine organic matter a combination of hydrogen and carbon isotope analyses of pleistocene sapropels from the tyrrhenian sea reveals new aspects of the factors leading to their deposition organic matter dd values that are significantly more negative in sapropels than in adjacent marls indicate a combination of dilution of surface waters by meteoric waters and increased burial of lipid rich organic matter during periods of sapropel deposition organic 13 c values in sapropels that are less negative than those in marls suggest periods of markedly elevated marine biological production the opposite but concordant excursions of these two isotopic parameters imply that the sapropel layers formed from increased export of marine organic matter from the photic zone to the sea floor during periods of greater fluvial delivery of continental nutrients to the mediterranean sea furthermore the isotopic evidence indicates that periods of wetter climate were widespread in southern europe at the same times as in northern africa

eastern mediterranean palaeoclimates from 26 to 5 ka b p documented by pollen and isotopic analysis of a core in the anoxic bannock basin continuous pollen and isotopic records were established for core ban 84 09 gc retrieved from the anoxic bannock basin in the eastern mediterranean on the basis of two 14c dates they document the palaeoclimate between about 25 7 ka b p and 5 2 ka b p in the northern borderlands of the ionian basin the upper half of the core has been redeposited the isotopic record displays a correlation with pollen percentages that is strong and positive for artemisia sage brush and negative for quercus oak the last glacial maximum and the deglaciation are identified by these combined taxa together with chenopodiaceae the glacial maximum around 18 ka b p which has elsewhere been dated from 20 to 15 ka b p has pollen percentages that are high for artemisia and low for quercus the climate in the pollen source area was arid cold in winter briefly warm in summer and sustained the vegetation of a semi desert the onset of deglaciation after 18 ka b p coincides with that of the decline in artemisia pollen percentage however this decline does not indicate reduced aridity because it is accompanied by a pollen percentage rise of the even more arid herbs chenopodiaceae and ephedra throughout the deglaciation from 18 to 11 ka b p the aridity progressively increases culminating at 11 ka b p this trend is briefly interrupted by a more humid event shown by a peak in artemisia pollen percentage and a smaller peak in oak these two peaks are coeval with the bolling allerod chronozone 13 11 ka b p maximum aridity occurs during the younger dryas chronozone 11 10 ka b p afterwards the oak pollen percentage begins a steady increase and its maximum value is coeval with the lowest isotopic value dated at 8760 170 yr b p this period was one of high moisture warm summers and according to altitude mild to cool winters this climate sustained forests that were mediterranean in the lowlands and warm temperate in the uplands a high pollen concentration is observed during this period and reveals the presence of sapropel s1 which is otherwise unrecognizable in this entirely black core during the following period between 8760 170 and 5200 yr b p the 180 reverts to slightly higher values and the quercus pollen percentage decreases while the pollen percentage of the wetter ostrya the oriental hornbeam increases the high pollen concentration during the deposition of sapropel s1 cannot have been caused by increased pollen input into the sea this pollen being wind borne nor by increased pollen production for all taxa both trees and herbs we conclude that it is entirely due to increased preservation of this allochtonous organic material by the deep anoxia of the bottom water below a thick anoxic water column the coincidence of sapropel deposition with warm and humid local climate as well as with the second global meltwater pulse suggests that the cessation of bottom water ventilation was due to decreased surface water density resulting from less saline incoming atlantic surface water increased local runoff and warmer winters

pollen distribution in recent marine sediments eastern canada analysis of 90 samples from coastal and continental shelf areas off eastern canada between 42 and 69 n shows that quaternary pollen and spores are present in recent marine muds throughout this region pollen and spore concentrations range from 50 000 to 100 grains per cm3 and they decrease both offshore as a function of distance from vegetation sources and northwards as a function of lower vegetation density north of the summer arctic frontal zone isopercentage contours show that maximum relative abundances of most palynomorphs occur in marine sediments adjacent to their regions of highest vegetation representation onshore however pinus and picea pollen tend to increase in percentage abundance with distance offshore presence of these tree pollen in marine sediments off baffin island implies that wind transport is an important pathway by which bisaccate pollen types enter the ocean in addition to fluvial transport q mode factor analysis shows that four major factors account for 89 of the variance amo

a hydraulic box model study of the mediterranean response to postglacial sea level rise 1 this paper quantifies the role of changing sea level in affecting mediterranean stratification using a new model of the strait basin system which allows for explicit time dependence during the last deglaciation fairbank s meltwater peak 1b leads to rapidly rising global sea levels and a freshening of the oceans and hence increasing influx of ever freshening atlantic water into the mediterranean basin owing to long residence times the salinity of the deep and intermediate water reservoirs would have decreased more slowly so that the basin was more stably stratified for a period with possible implications for sapropel formation our model is used to estimate the size of this reservoir effect in comparison to the freshwater influx from the opening of the black sea at the bosphorus it is found that this mechanism affects the stratification to a similar degree as the black sea opening other climatic mechanisms have also affected the freshwater budget of the mediterranean at this time but their sizes are more difficult to quantify

the marker bed of the mediterranean ridge diapiric belt geochemical characteristics abstract a prominent marker bed jet black in colour with a sharp basal contact and a few centimetres in thickness is ubiquitous in the mediterranean ridge crestal area where collision between the european plate and the african plate occurs and where mud diapirism is a common phenomenon the market bed is consistently recorded in the upper part of the sediment cores within the holocene pteropod foraminiferal oozes above sapropel s 1 which documents the last youngest postglacial sapropelic episode recorded in the eastern mediterranean the marker bed consists of numerous mn micronodules of bacterial origin and presents an abnormal concentration of metals especially of manganese of the 25 cores recovered during the r v gelendzhik 1993 cruise ttr 3 leg2 12 contained the marker bed but 13 did not the large majority of the latter 10 consisted of extruded mud breccia up to the core top and one consisted of pre holocene sediment eight cores of the 12 containing the marker bed had a pelagic make up the remaining ones contained the diapiric mud breccia of deep provenance seven cores were investigated geochemically for their elemental composition the new results confirm and support the previous ones and record percentages of mn within the marker bed ranging from 2 98 to 16 12 values that exceed by at least one order of magnitude those of the adjacent layers suggesting an origin independent from the local environment and dependent on an episode probably linked to the santorini bronze age eruption

timing and extent of late quaternary paleolakes in the trans pecos closed basin west texas and south central new mexico abstract the trans pecos closed basin is a hydrographically closed region covering 20 000 km 2 centered on salt basin 160 km east of el paso texas geomorphic and limnetic evidence have been used to identify four major highstands for lake king during the last glacial maximum lgm additional geomorphic features from a second recently identified paleolake lake sacramento have been found in the beargrass subbasin a nested subbasin approximately 75 km northwest of salt basin radiocarbon ages of the organic material in lake king sediments date four abrupt climate changes and rapid lacustrine transgressions during the lgm with a quasi periodicity of 2000 yr geomorphic evidence in the beargrass subbasin identifies lake cycles contemporaneous with those in lake king the dates for these transgressions correlate with the dates of freshening events identified by researchers in paleolake basins elsewhere in new mexico the quasi periodicity of the events approximates that of dansgaard oeschger events identified from greenland ice cores the contemporaneity of the trans pecos transgressions with transgressive events in other basins in the region suggests that paleolakes in the region were in phase with respect to abrupt climate changes during the latter stages of the lgm

palaeoproductivity and post depositional aerobic organic matter decay reflected by dinoflagellate cyst assemblages of the eastern mediterranean s1 sapropel abstract in the reconstruction of bioproductivity in surface waters the extent to which a proxy has been diagenetically altered is often a matter of debate here we investigate how organic and calcareous walled dinoflagellate cysts can be used for separately estimating bioproductivity and oxygen related diagenesis this is achieved by studying the cyst content of the most recent eastern mediterranean sapropel s1 that is thought to have been deposited under conditions of increased primary production in surface waters and possible anoxia in the bottom waters based on chemical evidence it has been shown that the visible sapropelic layer represents only the residual lower part of what was initially a much thicker sapropel as a result of post depositional decay of organic matter related to oxygen penetration into the sediments the effect of aerobic organic matter decay on the cyst associations is studied through the comparison of the unaffected lower part of the initial sapropel and the oxidised upper part comparing the unaffected sapropelic sediments with pre and post sapropelic material gives insight into the relationship between fossil cysts assemblages and palaeoproductivity impagidinium aculeatum impagidinium patulum operculodinium israelianum polysphaeridium zoharyi and probably impagidinium spp impagidinium paradoxum and nematosphaeropsis labyrinthus are very resistant against aerobic decay and their accumulation rates appear to be primarily related to productivity in surface waters protoperidinium and echinidinium species on the other hand are shown to be very sensitive and can be used to recognise oxygen related decay the calcareous walled dinoflagellate cysts seem to be unaffected by oxic organic matter decay in mediterranean sediments

oxygen and carbon isotopic composition and biogeographic distribution of planktonic foraminifera in the indian ocean five planktonic foraminiferal assemblages were encountered along a north south transect in the indian ocean with the following dominant species globorotalia truncatulinoides in the southern subtropical assemblage globigerinoides ruber globigerinella aequilateralis and globorotalia menardii in the northern subtropical assemblage globigerinoides sacculifer and pulleniatina obliquiloculata in the tropical assemblage neogloboquadrina dutertrei and globigerina bulloides in the tropical upwelling assemblage and globigernoides conglobatus in the tropical arabian sea assemblage oxygen and carbon isotopic analyses were performed on three surface dwelling species of planktonic foraminifera in tropical and subtropical waters 22 30 c the 18o of globigerinoides ruber and g sacculifer varies with surface water temperature and the slope of the isotope temperature regression line is similar to that of epstein et al 1953 for marine molluscs however foraminiferal 18o values are significantly lighter than those of molluscs indicating isotopic disequilibrium comparison between plankton tows taken within and below the mixed layer at the same stations shows that g ruber has similar low 18o values in both sets suggesting that it secretes its shell within the mixed layer by contrast g sacculifer has slightly higher 18o values below than within the mixed layer because it continues to secrete calcite below the thermocline no significant 18o variations with shell size were found on the other hand 13c values were strongly size dependent i e the smaller the size the lighter the 13c comparison of living g ruber and g sacculifer with recent specimens from the surface sediment shows that the living foraminifera are generally lighter in 18o than the fossils supporting independent observations that the latter have secreted additional calcite during gametogenesis when the organisms settle freely from the euphotic zone for about 12 h and pass through waters lower in temperature than the epipelagic waters where the foraminifera form the bulk of their shells

role of sea level forced sedimentary processes on the distribution of organic carbon rich marine sediments a review of the late quaternary sapropels in the mediterranean sea abstract the 124 ka to present sapropel s5 s1 series in the eastern mediterranean sea correspond to the last glacial interglacial period and permit detailed investigation of 5th order sedimentary frequencies the sapropel layers are clustered in high frequency milankovian cycle that occur within sequence stratigraphic 4th order cycles of late pleistocene holocene sea level oscillations the sea level changes had an amplitude exceeding 120 m and have been correlated to the glacial interglacial cycles modulated by the 100 ka eccentricity using published data we examined occurrences of the complete s5 s1 series in the mediterranean sea and then we focussed on two stratigraphic sequences in the central adriatic shelf and middle adriatic depression where sapropels s5 and s1 were deposited during periods of sea level rise recorded by the transgressive systems tract marine isotopic stage 5 and 1 respectively sapropels s4 and s3 were deposited during the highstand systems tract that developed throughout mis 5 of the late pleistocene sequence sapropel s2 should have been deposited during the warm mis 3 3 and followed the mis 4 sea level drop when sediment supply was enhanced during the late highstand and falling stage of sea level of the late pleistocene sequence the pronounced mis 2 cold stage led to a lowstand and to the regional erosional surface sequence boundary we also compared the adriatic sapropel s5 s2 sequence 4th order to the mid pliocene cluster o sequence 3rd order in both cases sapropels are well formed before the increase of sediment supply due to progradation of the shelf wedge that occurs in the late high stand and initial falling stage in sea level finally we considered the influence of sea level lowering which could cause a weakening of north adriatic deep water formation therefore influencing the mediterranean deep water circulation this condition would favour oxygen depletion but it does not correspond to a well developed sapropel as in the case of s2 based on the assumption that productivity increases related to insolation play a dominant role in their sedimentation sapropel s2 is the result of low amplitude insolation maxima that were unable to generate a productivity increase leading to the burial of conspicuous amount of organic matter therefore in the adriatic sea the absence of the s2 sapropel is correlated to the high sedimentation rate diluting the signal whereas in the eastern mediterranean basin this sapropel is virtually absent because of a weak orbital forcing combined with oxidation that erased its record

late glacial to holocene benthic foraminifera in the marmara sea implications for black sea mediterranean sea connections following the last deglaciation benthic foraminifera were studied from four gravity cores that penetrated holocene marine sediments in the marmara sea morphogroup and assemblage analyses reveal that the holocene sea level rise did not result in a catastrophic flooding event as proposed by w b f ryan and others whereby well oxygenated saline mediterranean waters rapidly inundated a low lying low salinity black sea lake at v7 15 ka popularly known as the noah s flood hypothesis rather the benthic foraminiferal data confirm the hypothesis that the dardanelles sill was breached by the mediterranean at v12 ka allowing saline waters to penetrate the marmara sea these saline waters reached the level of the bosphorus sill at v9 5 ka but were unable to penetrate into the black sea until after v9 1 ka because of the persistent strong outflow of brackish to fresh water from the black sea the initial colonisation of the marmara sea by benthic foraminifera is essentially synchronous with the re establishment of marine connections through the dardanelles strait at v12 ka by v10 ka ammonia dominated faunas developed on the strait exit delta v1 at the southern end of the bosphorus and at v9 1 ka the appearance of fully marine species documents the establishment of a more stratified water column over v1 finally the increase in abundance of planktonic foraminifera at the southern exit of the bosphorus after v6 1 ka reflects a decreased volume of outflow water from the black sea quantitative analysis of benthic foraminiferal morphogroups reveals that the oxygen content of subhalocline water was low below v1 5 ml l throughout the holocene and the occurrence of sapropel sediment in the deeper part of the basin suggests bottom waters may have been anoxic at times after v4 5 ka an increase in benthic foraminiferal oxic morphotypes suggests a reduction in black sea outflow and weakening of the halocline the strong and persistent stratification of the water column in the marmara sea throughout the holocene is entirely incompatible with the noah s flood hypothesis 2002 elsevier science b v all rights reserved

late postglacial paleoenvironmental change in the northeastern mediterranean region combined palynological and molecular biomarker evidence three gravity cores collected from the ne mediterranean nemr across a transect from the northern aegean sea north skyros basin to the south cretan margin scm were investigated for pollen and terrestrial biomarkers derived from epicuticular waxes of vascular plants during the last 20 ky pollen data show diversified mixed temperate forest in the northern borderlands and enhanced mediterranean vegetation in the southern areas documenting an n s climatic trend terrestrial plant biomarkers and their diagnostic geochemical indices exhibit latitudinal patterns which are interpreted in terms of the different delivery pathways fluvial runoff vs atmospheric transport resulting from the climate conditions during different periods during the late glacial and early deglaciation periods 20 14 ka bp relatively increased humidity h index is recorded in the north aegean sea while in the south drier climate was the limiting factor for vegetation development during this interval terrestrial n alkanes showed increased accumulation rates suggesting massive transport of terrestrial organic matter through runoffs and rivers followed by weaker input after 14 ka bp after 11 ka bp a major expansion of forest cover is evidenced in the nemr accompanied by a higher h index because of the climatic amelioration the forest vegetation exhibited regionally different characteristics with cool temperate taxa being more abundant in the aegean cores while the scm record is being featured by mediterranean elements at the onset of the holocene and throughout the holocene climatic optimum the delivery of terrestrial biomarkers increased and became more significant in the aegean sites compared to the scm site within the holocene the average chain length acl of long chain n alkanes exhibits lower values in the northern aegean than in the southeastern aegean and scm indicating the predominance of warmer species southwards finally the h index records a conspicuous humidity increase between 5 4 and 4 3 ka bp in the south aegean that coincides with an increase in the terrestrial biomarker supply and the deposition of a distinct sapropel like layer smh sapropel mid holocene similar trends in t temperature and h indices are slightly delayed and attenuated in the northern aegean and are accompanied by an increase in the acl index a noticeable increase in the accumulation rates ars of terrestrial biomarkers and the hpa index values during this period are clearly recorded in all three cores indicative of enhanced terrigenous inputs of organic matter along with higher in situ preservation

mediterranean quaternary sapropels an immediate response of the african monsoon to variation of insolation abstract in the subsurface of the east mediterranean sea eleven discrete basin wide organic rich black sapropels were deposited during the last 465 000 years they are dated by oxygen isotopic chronostratigraphy the most recent sapropel has been shown to be the consequence of heavy nile river summer floods due to increased monsoonal summer precipitation over ethiopia and not of scandinavian ice sheet meltwater influx into the east mediterranean sea as was previously believed while most sapropels were deposited during interglacials two thick sapropels formed during glacial periods as shown by their position in the oxygen isotopic stratigraphy and by their pollen record in core rc9 181 the new evidence presented here is that the sapropel sequence in this core including the two glacial sapropels correlates on a one to one basis with the highest values of an index of insolation on top of the atmosphere the concept of this index derives from an analysis of the african monsoon process the index variation is computed for the last 465 000 years from the caloric northern summer insolation in the tropical latitudes controlled by variations of the earth s orbital parameters it is conjectured that this index might be linked through the climate system to the monsoonal precipitation which in africa produces the nile river summer flood

metamorphic conditions in central connemara ireland metamorphic conditions have been estimated for an area in central connemara that includes cashel and lissoughter hill pressures lie in the range 3 0 6 0 kbar temperatures increase from 625 675 c on the n slopes of lissoughter hill to 650 700 c on the s slopes to 700 750 c in the migmatized metasediments n of the cashel ultrabasic intrusion before increasing sharply towards the contact away from the area adjacent to the intrusion a horizontal thermal gradient of between 30 c and 40 c km may be inferred differences in the relative spatial position with increasing temperature of the staurolite out muscovite and quartz out and beginning of partial melting isograds imply that the rocks exposed at the eastern end of the steep belt at maam cross were metamorphosed at a lower pressure than those farther w at recess similarly the stable co existence of muscovite and quartz in the recess area may indicate that the second sillimanite isograd dips towards the s a condition that would be consistent with sub vertical isotherms associated with a thermal anticline centred on the cashel volcanic arc

u pb and rb sr geochronology of magmatism and metamorphism in the dalradian of connemara western ireland new geochronological data which clarify the timing of syn orogenic magmatism and regional metamorphism in the connemara dalradian are presented u pb zircon data on four intermediate to acid foliated magmatic rocks show important inherited components but the most concordant fractions demonstrate that major magmatism continued until 465 ma whereas the earliest basic magmatism has been dated previously at 490 ma a fine grained fabric cutting granite contains discordant zircons which also appear to be 465 ma old arc magmatism in connemara therefore spanned a period of at least 25 ma recent u pb data on titanite from central connemara which gave a peak metamorphic age of 478 ma are supplemented by u pb data on titanite and monazite from metamorphic veins in the east of connemara which indicate that low p high t regional metamorphism continued there to 465 ma i e at least 10 ma later than in the central region dated previously new rb sr data on muscovites from coarse grained segregations in different structural settings range from 475 to 435 ma in part this range probably also reflects differences in age from west to east with three ages close to 455 ma from the eastern area which is also the site of the lowest pressure metamorphism thermal modelling indicates that at any one locality the duration of metamorphism was probably as little as 1 2 ma the new dates emphasize the complexity in the spatial and temporal distribution of high level regional metamorphism caused by magmatic activity the relatively simple overall distribution of mineral appearance isograds revealed by regional mapping masks the complexity of a prolonged but punctuated metamorphic history related to multiple intrusions primarily in the southern part of connemara the later stages of magmatic activity followed progressive uplift and erosion after the onset of magmatism and were localized in the eastern part of the region

late quaternary dinoflagellate cysts from the black marmara and aegean seas variations in assemblages morphology and paleosalinity abstract the link between sea surface salinity sss and dinoflagellate cyst morphology was studied quantitatively in cores of late quaternary mud from the black marmara and aegean seas where oxygen isotopic and planktonic foraminiferal data show salinities of about 5 19 15 22 and 36 39 ppt respectively in the black sea late glacial muds contain low diversity assemblages of the cruciform species spiniferites cruciformis and pyxidinopsis psilata with most s cruciformis cysts having expanded septal membranes form 1 circular outline form 2 irregular the assemblage is associated with surface salinities of in the northeast aegean core stenohaline species and morphotypes are rare occurring only as low percentages of s cruciformis forms 3 and 4 and o centrocarpum var truncatum in a mid holocene sapropel that was deposited during a period of high runoff and black sea water outflow marmara sea cores record surface salinities of 14 18 ppt during late glacial sapropel deposition and 20 22 ppt for the overlying marine sediments the sapropel is dominated by s cruciformis forms 1 and 2 and by p psilata with common l machaerophorum clavate and normal forms in surface sediments l machaerophorum is co dominant with o centrocarpum normal and truncate forms brigantedinium and spiniferites spp percentages of s cruciformis five forms and l machaerophorum two forms plotted against proxy salinity data however show no clear correlation indicating that morphological variation is not a simple function of salinity

late pleistocene holocene sedimentation in the nw aegean sea a palaeoclimatic palaeoceanographic reconstruction sedimentological particle size organic carbon calcium carbonate clay mineralogy and radiocarbon dating and micropalaeontological investigation of 9 cores from the nw aegean sea eastern mediterranean have enabled five main lithological units to be identified the units cover a period from the late pleistocene to the present day on the basis of these results and reference to other studies a palaeo reconstruction is presented for the area the reconstruction takes into account the increase in sea level during the period the decrease in fluvial inputs issuing to the area from the north mediterranean coastline and the possible influence of water issuing from the black sea it is concluded that the sedimentological and oceanographic regimes of the area were strongly influenced by a fluvial component during the late pleistocene and early holocene whereas today the sedimentary record is more indicative of an open oceanic environment

holocene sedimentation in the tectonically active tekirdag basin western marmara sea turkey abstract the effects of various depositional conditions and active tectonics on the late holocene sedimentation in the tekirdag basin west of the marmara sea were investigated in 11 gravity cores and on 3 seismic profiles representing shelf to slope to deep basin floor environments except for the two coarser grained avg 60 sand and gravel and calcareous avg 25 caco 3 shelf cores sediments in the slope and basin floor cores constitute low calcareous avg 12 caco 3 and terrigenous mud 90 silt and clay the occurrences of relatively higher total organic carbon contents in sediments from the southern slope 1 14 1 38 compared to that from the northern slope 0 37 1 2 indicate significant input from the southern rivers the presence of silty sandy laminations within the mud matrix of the cores and chaotic and mounded reflection configurations on the seismic profiles from the slope and basin floor environments all suggest the effects of gravity mass movements of sediments slides slumps turbidites most likely due to seismotectonic events earthquakes however it was difficult to establish a basin wide correlation between the historical earthquake events in the region and the positions of silty sandy laminations in dated deep sea sediment cores due to complicated other events such as repeated river run off and floods increased sediment load and slope failure the water contents of sediments from the basin floor avg 10 30 are significantly lower than those from the slope sediments avg 32 46 the former can be explained by the influences of synsedimentation with tectonics and compaction between the north and south boundary sub faults of the naf system whereas the latter shows fluidization of slope sediments during sliding and slumping radiocarbon dated base sections from three cores revealed that sediment deposition at these sites commenced about 4700 bp when the late holocene depositional conditions changed from the formation of upper sapropels to the present state the increases of organic carbon contents at or near the base sections of the cores support this contention

seasonal salinity changes during mediterranean sapropel deposition 9000 years b p evidence from isotopic analyses of individual planktonic foraminifera using stable isotopic analyses of individual tests of planktonic foraminifera with different seasonal and depth habitats we have investigated temporal variations in surface water salinities in the eastern mediterranean during the past 13 000 years low oxygen isotopic values document the presence of anomalously low salinity conditions in the eastern mediterranean at about 13 000 years b p 4000 years before the deposition of the youngest sapropel by 11 000 years b p during the deposition of presapropel sediments low salinity surface waters were more pervasive but were restricted to summer months and only affected the surface of the water column at the onset of sapropel deposition about 9000 years b p surface salinities in the eastern mediterranean had decreased by almost 4 and had extended to depths of at least 75 m the low salinity surface lens was not however a permanent feature of the eastern mediterranean during sapropel deposition low salinity surface conditions occurred in the fall and winter seasons but normal sea surface salinities returned during spring months on a seasonal and or interannual basis thus a low salinity surface lens could have existed continuously for months or decades at a time but would have been interrupted intermittently by a return to normal conditions any triggering mechanism proposed for mediterranean sapropels must account for the seasonal fluctuations and ephemeral nature of low salinity conditions in the eastern mediterranean despite normal salinities returning occasionally during spring months a low salinity surface lens may have greatly inhibited the production of levantine intermediate water prevented the formation of adriatic deep water and consequently reduced ventilation of the eastern mediterranean

conditions of high grade metamorphism in the dalradian of connemara ireland in e connemara ireland dalradian metasediments were initially metamorphosed to kyanite staurolite grade at pressures above 7kbar the subsequent emplacement of basic to intermediate magmas accompanied by uplift and erosion produce a steepening of the geothermal gradient and led to the formation of migmatitic garnet cordierite sillimanite gneisses in the highest grade regions in the s cation exchange equilibria between coexisting mineral pairs suggest that partial melting took place under high temperatures 750 c and moderate pressures 4 5 6 kbar fluid inclusion studies and andalusite occurrences from migmatite leucosomes suggest that crystallization of the melts occurred at lower pressures

dinoflagellate cysts freshwater algae and fungal spores as salinity indicators in late quaternary cores from marmara and black seas abstract seismic profiles and mollusks have been used to suggest that from 12 500 to 7000 yr bp the black sea was an isolated freshwater lake containing potable water and implying a surface salinity of 24 and that spiniferites cruciformis spiniferites inaequalis peridinium ponticum polykrikos spp and quinquecuspis concreta characterize the lower salinity of the marmara and or black seas the core top data and correlatable down core assemblage changes in time equivalent sapropelic and brown muds show that there is no evidence for differential aerobic decay of dinocysts in the study area the main acritarchs are sigmopollis psilatum concentricystes cf c rubinus and cf acritarch 8 of traverse 1978 all of which are absent from the aegean sea and decrease in abundance with increasing salinity the first two taxa have been reported previously as freshwater species fungal remains show a similar distribution pattern to the freshwater acritarchs indicating their origin from terrestrial environments freshwater chlorococcales are almost confined to the black sea but they have rare occurrences in the aegean indicating long distance transport microforaminiferal linings are abundant in the marmara sea but are absent in deep water of the black sea in the marmara sea mid late holocene assemblages

organic geochemical evidence of late glacial holocene climate instability in the north aegean sea sedimentary molecular biomarker compositions organic carbon and caco3 concentrations and bulk organic 13c and total 15n values document a series of paleoclimatic changes that have affected organic matter production and sedimentation in the north aegean sea from the termination of the latest glacial maximum through the middle holocene continental environmental conditions have been inferred from land plant biomarkers paleoproductivity patterns of diatoms prymnesiophytes dinoflagellates and nannoplankton were discerned from marine derived biomarkers although organic matter is predominantly marine variations in the proportion of marine and land contributions and in its general preservation are evident rapid changes in the eastern mediterranean thermohaline circulation evidently occurred in parallel to sea surface temperature oscillations enhanced deep water ventilation accompanied cold intervals in the late last glacial the younger dryas and during an interruption of deposition of the s1 sapropel probably in response to strengthening of north winds over the region in contrast decreased thermohaline circulation occurred during the warm interval associated with the s1 sapropel during this period increased freshwater inputs diminished ventilation of deep water masses and enhanced organic matter production and preservation intriguing fluctuations in sea surface temperatures and the concentrations of marine and terrestrial biomarkers within the sapropelic layer most prominently in the interruption from 8 2 to 7 8 calibrated radiocarbon conventional kyr bp support the hypothesis that several distinct events of deep water reoxygenation occurred in the north aegean sea during deposition of the s1 sapropel these events reflect centennial excursions to the more common low productivity and well ventilated conditions of the mediterranean that may possibly be related to north atlantic oscillation cycles

distribution of biogenic silica and quartz in recent deep sea sediments all available quartz and biogenic silica concentrations from deep sea surface sediments were intercalibrated plotted and contoured on a calcium carbonate free basis the maps show highest concentrations of biogenic silica opal along the west african coast along equatorial divergences in all oceans and at the polar front in the southern indian ocean these are all areas where upwelling is strong and there is high biological productivity quartz in pelagic sediments deposited far from land is generally eolian in origin its distribution reflects dominant wind systems in the pacific but in much of the atlantic and indian oceans the distribution pattern is strongly modified by turbidite deposition and bottom current processes

palynological evidence for climatic change anthropogenic activity and outflow of black sea water during the late pleistocene and holocene centennial to decadal scale records from the black and marmara seas abstract previous marine palynology studies of pollen and dinoflagellate cysts dinocysts in the black sea mediterranean corridor were made on short cores allowing only millennial century scale reconstruction of past climates we now describe pollen accumulation rates for 5 cores with eleven 14c ages over 30 000 years and new decadal scale data for a holocene core with fourteen 14c ages pollen influxes show pinus abies quercus forest steppe and deteriorating climate from 29 8 24 kyr bp then colder drier pre and post lgm conditions with artemisia cheno ams and ephedra that lasted through the bolling interstade deciduous oak returns by the younger dryas and rapidly expands followed by pistacia by 9 3 kyr bp foraminiferal 18o shows 4 c cooler than present late glacial summers and rapid holocene warming by 9 bp influxes from quercus cerris tilia fagus castanea ulmus shade ferns aquatics swamp plants and 18o indicate warm winters 5 c or more and year round precipitation 600 1000 mm not the dry conditions that would be required for black sea drawdown there is mid holocene expansion of carpinus evergreen quercus and pistacia walnut olive and cereal pollen suggest early cultivation attempts but no sustained farming before 4 5 kyr bp dinocyst assemblages show major changes traceable throughout the corridor variability in process length marks low diversity n 13 pleniglacial early holocene spiniferites cruciformis assemblages suggesting fluctuating salinity like the modern caspian sea with brackish to saline conditions 5 16 distributions of euryhaline cysts spiniferites mirabilis and spiniferites bentorii show the aegean and marmara seas were connected by 11 kyr bp and linked to black sea by 9 3 kyr bp there is no palynological evidence of either freshwater salinity

late pleistocene variability of the carbon isotopic composition of organic matter in the eastern mediterranean monitor of changes in carbon sources and atmospheric co2 concentrations the organic carbon isotopic record of the sapropels s1 and s3 s10 and intercalated marl oozes has been determined in a 12 m piston core from the eastern mediterranean the 13corganic values are systematically lighter mean 21 0 0 82 in all sapropels and heavier mean 18 8 1 07 in the marl oozes these differences are not due to variable marine and terrestrial organic matter mixtures because all values are heavier than modern plankton in the mediterranean there is no relationship between the corganic n ratios and the isotopic values and published information on the abundance and distribution of organic biomarkers shows that terrestrial material constitutes a minor fraction of the total organic matter temperature effects on isotope fractionation are also discounted because the change in 13corganic values between glacial and interglacial horizons is in the opposite sense diagenesis which can produce relatively small changes in the carbon isotopic composition of sedimentary organic matter under certain circumstances is unlikely to have caused the observed differences because this mechanism would cause an enrichment in 12c implying that all values were even heavier originally and there is no secular trend in the 13corganic record the observed differences in 13corganic between the two lithologies are probably produced by changes in the isotopic composition and the concentration of dissolved co2 first freshwater flooding during the formation of the sapropels caused the isotopic composition of the dissolved inorganic carbon in the surface waters of the mediterranean to become lighter because of the 13c deficiency in fresh waters hence photosynthesis would have produced isotopically lighter organic material second changes in atmospheric pco2 between glacial and interglacial periods as shown by the vostok ice core caused marked changes in the concentration of free dissolved co2 in the mixed layer lower values during glacial maxima caused a smaller fractionation of the carbon isotopes by phytoplankton whereas levels were less limiting during the interglacials concentrations of dissolved co2 could also have been much higher during the deposition of the sapropels because of the supply of regenerated co2 to the mixed layer by upwelling and this could have further lightened the 13corganic values in the sapropels themselves carbon isotope records may provide an alternative method for estimating atmospheric pco2 levels over longer time periods than can be obtained from ice cores

low salinity surface water incursions across the strait of sicily during late quaternary sapropel intervals abstract sapropel layers black organic rich sediments in the deep eastern mediterranean basin are indicators of anoxic conditions that occurred intermittently during the pleistocene during these times of deep water stagnation the surface waters were marked by changes in planktonic foraminiferal assemblages indicative of reduced salinity previous work has established a strong link between low salinity surface waters and glacial meltwater inflow into the eastern mediterranean via the black sea discriminant analysis was applied to foraminiferal abundance data from the sapropelcontaining core lynch ii 3 collected in 2400 m water depth approximately 80 km east of the strait of sicily the function produced is 98 effective at distinguishing the faunal assemblages in non sapropel sediments from those associated with four sapropel layers in this core the most distinctive characteristic of the sapropel faunas is a high percentage of neogloboquadrina dutertrei the discriminant function has been applied to a suite of cores from the strait of sicily that lack sapropels because the strait maximum depth of 1700 m has remained continuously aerated this analysis has distinguished planktonic foraminiferal assemblages and associated sediments coeval with sapropel formation in the deeper eastern basin these correlations are supported by planktonic foraminiferal biostratigraphy and a distinctive ash layer in core lynch ii 3 and two cores from the strait existence of the sapropel assemblage in core tr171 11 from the western entrance of the strait indicates that low surface salinities extended through the strait a condition requiring a surface water flow from east to west a reversal of the present day circulation pattern

thermal modelling in low pressure high temperature metamorphic belts abstract low pressure high temperature metamorphic belts occur throughout the world they display a characteristic metamorphic style which has remained unchanged with time they are found in disparate tectonic settings including magmatic arcs regions of extension regions of thickened crust in continent continent collision zones and accretionary wedges they are commonly characterized by an abundance of granitoid plutons pressures of metamorphism are primarily less than or equal to that of the aluminosilicate triple point approximately 4 kbar while temperatures are in the range 500 750 c with rare exceptions inferred ptt paths are nearly isobaric and recrystallization was rapid and prograde metamorphic thermal gradients are commonly in the range 60 150 c km these conditions necessitate the presence of a large component of advective heat transfer and or anomalously high basal heat flow during metamorphism the large magmatic fluxes associated with the formation of magmatic arcs provide an adequate heat source for low pressure metamorphism lpm lithospheric extension is likely to produce lpm only if the degree of thinning is large 3 and there is additional heat from magmas the generation of lpm by crustal thickening requires either a large component of advective heating by magmas anomalously high basal heat flow or pre thickening lithospheric extension lpm in this environment must necessarily be accompanied by plutonic activity advection of heat by aqueous fluids may provide a significant contribution to the thermal budget but acting along is unlikely to produce lpm regional lpm induced by advective sources rarely occurs along a geotherm which increases monotonically with depth or synchronously across the region at a given depth it occurs over time as a series of overlapping temporally separate and spatially localized thermal events

deltas south of the bosphorus strait record persistent black sea outflow to the marmara sea since 10 ka at the southern exit of the bosphorus strait in the northeastern marmara sea high resolution seismic profiles reveal two lobate progradational delta lobes in modern water depths of v40 65 m the younger delta was active from v10 to 9 ka based on radiocarbon dates of equivalent prodelta deposits and the elevation of its topset to foreset transition the topset to foreset transition climbs in the seaward direction because the delta prograded into a rising sea low abundances of marine fauna and flora in the 10 9 ka interval support a deltaic interpretation there are no rivers in the area that could have fed the delta instead all evidence points to the strait itself as the source of sediment and water when this outflow was strongest v10 6 6 0 ka sapropels accumulated in basinal areas of both the aegean and marmara seas benthic foraminiferal and dinoflagellate cyst data from contemporary deposits elsewhere in the marmara sea point to the continual presence through the holocene of a surface layer of brackish water that we ascribe to this same outflow from the black sea through the bosphorus strait by v9 1 8 5 ka two layer flow developed in the bosphorus strait as global sea level continued to rise and the sediment supply to the younger delta was cut off because the outflowing black sea water ceased to be in contact with the floor of the strait the older delta lobe lies below a prominent lowstand unconformity and is tentatively interpreted to have formed from v29 5 to 23 5 ka oxygen isotopic stage 3 when the marmara sea stood at v355 m and a second sapropel accumulated in deep basinal areas crown copyright 2002 elsevier science b v all rights reserved

pollen stratigraphy of late quaternary cores from marmara sea land sea correlation and paleoclimatic history marine pollen analysis is an important tool for paleoclimatic reconstruction of regions like the eastern mediterranean and near east where few onshore sites provide long pollen records first a compilation was made of core top data from the eastern mediterranean to blackseas to map regional variations in modern marine pollenspore concentrations these data show a strong linkbetween pollen spore concentrations and sea surface salinity with minima of 5 grains g in the southern mediterranean and maxima of 160 000 grains g in the blacksea despite under representation of some forest and herbaceous vegetation indicators e g fagus and pistacia variations in species composition of the marine assemblages correspond closely with the distribution of regional vegetation zones and can be used as proxies for spatial differences in seasonal and total temperature and rainfall pollen spore assemblages in five cores from the marmara sea with multiple ages ranging from 33 550 to 1990 yr bp and one holocene core from southeastern blacksea were used to compile a late quaternary marine pollen stratigraphy these data were then compared with eastern mediterranean onshore reference sites in order to reconstruct a vegetation and paleoclimate history for the blacksea aegean corridor from the pleniglacial interval to present five marine pollen zones are recognized pz 5 v33 6 24 ka corresponds to the late wu rm pleniglacial pz 4 v24 13 ka spans the late glacial maximum lgm pz 3 v13 10 2 ka includes the allero d younger dryas glacial interglacial transition pz 2 10 2 4 ka marks the early holocene interglacial warm wet interval and pz 1 covers the latest holocene colonization phase which may also have been cooler and drier using the steppe forest index of traverse 1975 it is shown that the only intervals of severely dry conditions occurred briefly during the lgm and its transition during most of the pleniglacial and all of the postglacial time precipitation versus evaporation rates were sufficiently high to permit persistence of oro mediterranean forest vegetation furthermore there is no evidence for environmental conditions in the blacksea marmara region that would have encouraged pastoral or agricultural settlement in the littoral region prior to the bronze age commencing 4600 years ago crown copyright a 2002 elsevier science b v all rights reserved

paleo environmental controls on cold seep carbonate authigenesis in the sea of marmara abstract the factors controlling fluid emission dynamics at ocean margins are poorly understood in particular there are significant uncertainties on how fluid seepage at cold seeps may have responded to abrupt environmental changes in the geological past this study reports on a detailed geochemical investigation of seafloor carbonate crusts sampled at cold seeps along the submerged part of the north anatolian fault system in the sea of marmara an inland sea which has experienced major paleo environmental changes over the last deglaciation period we also analyzed a series of authigenic carbonate concretions recovered from two sediment cores at the western high ridge an active fluid venting area the ages of seafloor carbonate crusts derived from isochron u th dating cover the last 7 kyr suggesting that fluid activity along the fault system remained continuous over that time interval in the sediment cores carbonate concretions are concentrated at the lacustrine to marine transition which corresponds to the period when mediterranean waters flowed into the marmara basin about 12 14 kyr ago u th isotopic data indicate that most of these concretions formed later during the holocene around 9 10 kyr ago a period coinciding with an important anoxic event that led to the deposition of a sapropel layer in the sea of marmara based upon these results we suggest that the absence of carbonate concretions in the lacustrine sediment unit indicates that dissolved sulfate concentrations in the marmara lake pore waters during glacial time were too low to promote significant anaerobic methane oxidation thereby preventing sedimentary carbonate authigenesis in contrast the progressive inflow of mediterranean waters into the glacial marmara lake after 15 ka provided a source of dissolved sulfate that allowed anaerobic oxidation of methane to proceed within the anoxic sediment importantly the synchronism between the main phase of authigenic carbonate precipitation at the studied sites average 9 4 1 8 ka n 16 and the regional anoxic sapropel event support the idea that the drop in bottom water dissolved oxygen content was probably a key factor to enhance microbial activity and associated carbonate precipitation at that time overall these results provide straightforward evidence that fluid emission dynamics and hydrocarbon oxidation at cold seeps can be directly related to changing environmental conditions through time

paleoclimatic and paleoceanographic conditions leading to development of sapropel layer s1 in the aegean sea abstract sapropel s1 occurs as 25 35 cm thick black weakly laminated muds in aegean sea cores s1 was deposited between 9600 and 6400 yr b p during a period of isotopically depleted and relatively cool surface waters micro faunal and floral data indicate a major reduction in surface waters salinity during the deposition of s1 and oxygen isotopic data show a northerly fresh water source relatively light 13 c org and high pollen spore concentrations in s1 suggest increased influx of terrestrial organic carbon probably supplied by major rivers draining into the northern aegean sea benthic foraminifera indicate high nutrient low oxygen bottom waters for s1 and together with silt sized hematite and manganese coatings suggest that during the deposition of s1 surface sediments were oxic visual and xrd evidence of pyrite in s1 together with enrichments in s cu zn as ni cr and fe suggest that subsurface conditions were sufficiently reducing for so 4 2 reduction to occur probably by diffusion from surface oxic into subsurface anoxic sediments palynomorphs in s1 show large increases in terrestrial pollen and spores with the floral assemblage indicating significant influx from northern european rivers and minor african components associated with increased summer monsoonal rain abundance of dinoflagellates and amorphogen suggests some increase in primary productivity in response to increased influx of humic compounds however there is no evidence of upwelling the clay fraction in s1 shows notable decreases in smectite and kaolinite and reciprocal increases in illite and chlorite the combined data suggested that the evolution of s1 in the aegean sea largely resulted from stagnation of the surface waters during the final disintegration of the continental ice sheets rather than an increase in primary productivity and higher preservation of organic carbon on the sea floor

geochemistry of eastern mediterranean sediments primary sediment composition and diagenetic alterations abstract two cores recovered in the eastern mediterranean were analysed for major minor and trace elements the primary chemical composition of the sediment is different at each location probably because the lithological sources and the relative biogenic contributions differ carbonates are important for the concentration of ca mg and sr whereas aluminosilicates determine the concentration of si al k li y and be and to a lesser extent that of fe cr ti mg zn and zr in sapropels organic carbon and sulphur seem to be closely related bromine mo p fe v cu zn co ni and cr are closely associated with organic and sulphidic compounds the concentration versus depth profile for organic carbon in two sapropels points to a rapid establishment of conditions that gave rise to sapropel formation followed by a gradual transition back to normal conditions the primary composition is overprinted by diagenetic processes sulphate reducing conditions occurred during and just after sapropel deposition a progressive oxidation front mechanism which became active after sapropel deposition is responsible for additional major geochemical changes this diagenetic phenomenon has strong implications for the chemistry of fe mn ni co zn cu cr v u as and sb

structural age of the connemara gabbros western ireland a d2 age of intrusion for the connemara gabbros is rejected the gabbros were intruded 490 ma ago probably just prior to the d3 deformation and together with younger members of the metagabbro and gneiss complex were responsible for a widespread sillimanite grade contact metamorphism which overprinted the regional d2 gamet staurolite kyanite metamorphism and the major d3 folds comparison with the ne scotland gabbros is thereby strengthened supporting the idea that they were both part of a coeval magmatic arc developed at the margin of the caledonian fold belt

organic geochemical and palynological evidence for terrigenous origin of the organic matter in aegean sea sapropel s1 abstractorganic geochemistry and micropaleontology are used to determine the origin of sapropel s1 in the aegean sea low molecular weight c 15 c 17 and c 19 n alkane data show that net primary productivity npp increased from 14 000to 10 000 yr bp at the glacial interglacial transition but the onset of s1 at 9600 yr bp marks a sharp decline in npp whichremained low until 8200 yr bp the start of sapropel deposition is marked by increased total organic carbon toc and pollen spore concentrations together with increased high molecular weight c 27 c 29 c 31 and c 33 n alkanes pollenassemblages show large in ux of tree pollen from central northern european forests increases in high molecular weightn alkanes suggest greater in ux of fresh vascular plant material at the start of s1 although the amount is small comparedto other insoluble organic matter palynological studies showed that most of this insoluble organic matter are ocksof dark brown amorphous kerogen typical of terrigenous humic compounds from 8200 yr bp to the top of s1at 6400 yr bp there is a decline in high molecular weightn alkanes and terrigenous kerogen and an increase inlow molecular weightn alkanes suggesting that npp recovered during the later deposition of s1 in the aegean sea theincrease in low molecular weightn alkanes coincides with the recovery of coccolithophores and dino agellates suggestingthat these phytoplankton are primarily responsible for the low molecular weightn alkane variations these data from theaegean sea support the model for sapropel deposition resulting from increased in ux of toc during times of stagnantbottom water but disagree with mediterranean models prescribing a large increase in marine productivity 1999 elsevierscience b v all rights reserved keywords sapropel s1 aegean sea fatty acids n alkanes palynology

last glacial holocene paleoceanography of the black sea and marmara sea stable isotopic foraminiferal and coccolith evidence multi proxy data and radiocarbon dates from several key cores from the black sea and marmara sea document a complex paleoceanographic history for the last v30 000 yr the marmara sea was isolated from both the black sea and the aegean sea during glacial periods when global sea level lowering subaerially exposed the shallow sills at the straits of bosphorus and dardanelles i e lake stage and reconnected through both straits during interglacial periods when rise of global sea level breached the shallow sills i e gateway stage micropaleontological data show that during the lake stage the surface water masses in both the marmara sea and black sea became notably brackish however during the gateway stages there was a low salinity surface layer and normal marine water mass beneath two sapropel layers are identified in the marmara sea cores sapropels m2 and m1 were deposited between v29 5 and 23 5 ka and v10 5 and 6 0 ka respectively micropaleontological and stable isotopic data show that the surface water salinities were reduced considerably during the deposition of both sapropel layers m2 and m1 and calculation using planktonic foraminiferal transfer functions shows that sea surface temperatures were notably lower during these intervals the presence of fauna and flora with black sea affinities and the absence of mediterranean fauna and flora in sapropels m1 and m2 strongly suggest that communication existed with the black sea during these times a benthic foraminiferal oxygen index shows that the onset of suboxic conditions in the marmara sea rapidly followed the establishment of fully marine conditions at v11 10 5 ka and are attributed to black sea outflow into the marmara sea since 10 5 ka these suboxic conditions have persisted to the present the data discussed in this paper are completely at odds with the flood hypothesis of ryan et al 1997 and ryan and pitman 1999 crown copyright 2002 elsevier science b v all rights reserved

lusi mud eruption triggered by geometric focusing of seismic waves the lusi mud eruption in indonesia has been ongoing since 2006 numerical simulations show that a parabolic shaped layer in the rock surrounding the site of the lusi eruption could have amplified and focussed incoming seismic energy from an earthquake which then triggered the mud eruption

black sea marmara sea quaternary connections new data from the bosphorus istanbul turkey abstract previous studies concluded that the bosphorus strait was formed during the quaternary by fluvial incision of a valley between the black sea to the north and the marmara sea in the south hitherto however few details of the evolution of this connection have been elucidated from the sediments deposited within the bosphorus itself we report here details of sedimentological and palaeontological evidence relating to this history obtained from five boreholes drilled into the unconsolidated sediment fill in the north central sector of the bosphorus together with nearby geophysical profiles the quaternary fill of this part of the bosphorus comprises two major facies associations yellow arkosic sands dominate the lower facies association a these are assigned a middle to late pleistocene age and the contained faunas have a lagoonal to lacustrine character and a black sea provenance paratethyan affinities the abruptly succeeding units of facies association b comprise fining and coarsening upwards units of coarse to fine shelly and clayey sands that alternate with shell bearing green clays these sediments were formed in a range of marine and coastal settings and biostratigraphic evidence and absolute dating demonstrate the mid late holocene age of this upper unit initially brackish faunal assemblages in this upper unit show an upward increase in marine and mediterranean affinities integrating these new data with previously published observations from coeval deposits in the southern bosphorus and izmit bay ne marmara sea we conclude that during the late pleistocene and early holocene a topographic barrier existed in the south central sector of the bosphorus on both sides of which estuarine and lagoonal sediments accumulated with distinctive black sea and mediterranean faunas during a significant rise in sea level between 7000 and 5300 years ago this barrier was finally submerged permitting interchange of marine waters between the mediterranean and the black sea and creating the present oceanographic situation this evolution conflicts with the cataclysmic role of the bosphorus in the early holocene as postulated in the catastrophic flood hypothesis of ryan et al mar geol 138 1997 119 126 annu rev earth planet sci 31 2003 525 554 it also contrasts with the history recorded from the gulf of izmit where intermittent connection between these two bodies of water throughout much of the quaternary is evident

the application of spinel bearing metapelites to p t determinations an example from south india metasedimentary migmatites from the archean charnockitic terrain of south india contain the five phase equilibrium assemblage spinel cordierite garnet corundum sillimanite the assemblages is a result of anatexis which has generated a silica deficient anhydrous restite peak metamorphic conditions are defined by the intersection of two divariant reactions in the a12o3 sio2 feo mgo system at which the five phases coexist these reactions are univariant and their intersection invariant if the fe mg ratio of at least one femic phase is fixed

late quaternary paleoceanography as recorded by benthonic foraminifera in strait of sicily sediment sequences at specific times during the late quaternary a widespread low salinity surface water layer was produced over the eastern mediterranean which created stagnant conditions and associated deposition of sapropelic muds in the deep basins the strait of sicily has been positioned above the anoxic deeper water masses and is therefore devoid of sapropel deposits sediment sequences in the region contain a valuable record of upper bathyal 200 1000 m benthonic foraminiferal change during times of deep basin stagnation quantitative examiniation of benthonic foraminiferal assemblages in strait of sicily quaternary cores generally reveals changes coeval with sapropels s1 s2 s4 s5 and s6 the benthonic foraminiferal expression is seen as increases in frequency ofglobobulimina affinis globobulimina pseudospinescens chilostomella mediterranensis bolivina dilatata and otherbolivina species during intervals corresponding to the episodic abyssal stagnation events some cores also display a decrease incassidulina carinata and an increase inarticulina tubulosa similar assemblage changes have been previously documented to be closely associated with the sapropel layers in the deep basins of the eastern mediterranean the actual sapropel layers usually do not contain benthonic foraminifera however in the strait of sicily area the species exhibit less drastic changes than in the deep eastern basins because of the less severe anoxic conditions in the deep eastern basins benthonic foraminifera almost totally disappeared in sapropel layers at the same time there was a general reduction in foraminiferal numbers in the shallower strait area

seismic stratigraphy of late quaternary deposits from the southwestern black sea shelf evidence for non catastrophic variations in sea level during the last 10 000 yr abstract detailed interpretation of single channel seismic reflection and huntec deep tow boomer and sparker profiles demonstrates that the southwestern black sea shelf formed by a protracted shelf edge progradation since the miocene pliocene five seismic stratigraphic units are recognized unit 1 represents the last phase of the progradational history and was deposited during the last glacial lowstand and holocene it is divided into four subunits subunit 1a is interpreted as a lowstand systems tract 1b and 1c are interpreted as a transgressive systems tract and subunit 1d is interpreted as a highstand systems tract the lowstand systems tract deposits consist of overlapping and seaward prograding shelf edge wedges deposited during the lowstand and the subsequent initial rise of sea level these shelf edge wedges are best developed along the westernmost and easternmost segments of the study area off the mouths of rivers the transgressive systems tract deposits consist of a set of shingled shore parallel back stepping parasequences deposited during a phase of relatively rapid sea level rise and include a number of prograded sediment bodies including barrier islands beach deposits and thin veneers of seismically transparent muds showing onlap onto the flanks of older sedimentary features a number of radiocarbon dates from gravity cores show that the sedimentary architecture of unit 1 contain a detailed sedimentary record for the post glacial sea level rise along the southwestern black sea shelf these data do not support the catastrophic refilling of the black sea by waters from the mediterranean sea at 7 1 ka postulated by ryan pitman major shimkus maskalenko jones dimitrov gorur sakinc yuce mar geol 138 1997 119 126 ryan pitman touchstone book 1999 319 pp and ballard coleman rosenberg mar geol 170 2000 253 261

short term climate changes in the southern aegean sea over the last 48 000 years abstract high resolution palaeoenvironmental changes corresponding to a mean time interval of 450 years covering the last 48 000 years were examined in a core from the cretan basin in the southern aegean sea the intensity and duration of the climatic and oceanographic events were determined by examining the compositional changes in the planktonic foraminifera and pollen assemblages along with the 18o signal of globigerinoides ruber a reconstruction of sea surface temperatures was attempted using the modern analogue technique mat in total 10 stadials and 6 interstadials occurred over the last 48 000 years these fluctuations in climatic conditions coincide with fluctuations documented in the western and central mediterranean and seem to be associated with dansgaard oeschger events some of these climatic fluctuations are correlated with changes in the vegetation in the surrounding land between 48 and 10 cal kyr bp the most pronounced stadials occurred at 41 cal kyr bp c69 st10 and at 13 cal kyr bp c69 st4 these events are characterized by i high positive 18o values of globigerinoides ruber ii drops in sst and iii increases in aridity these events may be correlated with the heinrich h4 event and the younger dryas event respectively two other stadials at 23 cal kyr bp c69 st6 and at 16 cal kyr bp c69 st5 which are characterized by increases in the abundance of the cold plaktonic foraminifera species and increases in aridity may be correlated with the h2 and h1 events respectively the dominant planktonic foraminiferal species during the stadials witch are correlated with the heinrich events were turborotalita quinqueloba and globorotalia scitula the most pronounced interstadials occurred between 39 5 and 38 5 cal kyr bp c69 ist6 and between 25 and 24 cal kyr bp c69 ist3 and are characterized by depletion in 18o values increases in sst and increases in humidity the former event coincides with the formation of the sapropelitic layer s2 in the holocene the most pronounced stadial occurred between 8 and 6 5 cal kyr bp c69 st2 during the interruption of s1 and is characterized by a reduction in sst and an increase in aridity the most pronounced interstadials of holocene occurred during the formation of s1a and s1b between 9 and 8 cal kyr bp c69 ist1 and between 6 5 and 5 5 cal kyr bp c69 ist2 respectively these events are characterized by depletion in 18o values increased sst and an increase in humidity as is indicated by the expansion of temperate evergreen and mediterranean taxa in the pollen record

the east java mud volcano 2006 to present an earthquake or drilling trigger abstract on may 29th 2006 a mud volcano later to be named lusi started to form in east java it is still active and has displaced 30 000 people the trigger mechanism for this the world s largest and best known active mud volcano is still the subject of debate trigger mechanisms considered here are a the may 27th 2006 yogyakarta earthquake b the drilling of the nearby banjar panji 1 gas exploration well 150 m away and c a combination of the earthquake and drilling operations we compare the distance and magnitude of the earthquake with the relationship between the distance and magnitude of historical earthquakes that have caused sediment liquefaction or triggered the eruption of mud volcanoes or caused other hydrological responses based on this comparison an earthquake trigger is not expected the static stress changes caused by the rupture of the fault that created the yogyakarta earthquake are a few tens of pascals much smaller than changes in stress caused by tides or variations in barometric pressure at least 22 earthquakes and possibly hundreds likely caused stronger ground shaking at the site of lusi in the past 30 years without causing an eruption the period immediately preceding the eruption was seismically quieter than average and thus there is no evidence that lusi was primed by previous earthquakes we thus rule out an earthquake only trigger the day before the eruption started may 28th 2006 as a result of pulling the drill bit and drill pipe out of the hole there was a significant influx of formation fluid and gas the monitored pressure after the influx in the drill pipe and annulus showed variations typical of the leakage of drilling fluid into the surrounding sedimentary rock strata furthermore we calculate that the pressure at a depth of 1091 m the shallowest depth without any protective steel casing exceeded a critical level after the influx occurred fractures formed due to the excess pressure allowing a fluid gas mud mix to flow to the surface with detailed data from the exploration well we can now identify the specific drilling induced phenomena that caused this man made disaster

seismic stratigraphy and quaternary sedimentary history of the northeast aegean sea abstract seismic profiles show that the upper quaternary recent stratigraphic architecture of the ne aegean sea is characterized by several vertically stacked depositional sequences which are developed within three ne sw trending basins the depositional sequences are separated from one another by prominent shelf crossing unconformities formed during periods of falling and low sea level and reworked further during the subsequent sea level rise by shoreface erosion each depositional sequence consists of a lower mainly parallel stratified subunit and an upper oblique to sigmoid oblique prograded subunit the lower subunit represents hemipelagic and prodeltaic deposition of the transgressive and early highstand systems tracts the upper subunit represents deltas of the forced regressive systems tract the chronology of the depositional sequences is constrained by radiocarbon and u th dates on cores an average sedimentation rate of 30 cm ka is calculated for basinal muds of the region correlations with global sea level curves based on oxygen isotope stratigraphy reveal that the seaward prograded delta sequences developed on a rapidly subsiding shelf during successive glacio eustatic sea level falls associated with late quaternary glaciations a set of paleogeographical maps shows changing basin configuration since 330 ka volumes of the depositional sequences compare well with the volumes of sediment estimated to have been eroded from the incised valleys of the tuzla karamenderes and dumbek rivers draining the biga peninsula

fluid disturbed hornblende k ar ages from the dalradian rocks of connemara western ireland the results of k ar age determinations and hydrogen and oxygen stable isotope measurements on hornblendes from the poly metamorphic dalradian schists of connemara western ireland indicate that the hornblende k ar systems have been significantly disturbed by low temperature fluid reaction correlations between k ar ages d values structural water contents and the occupancy of the hornblende structural a sites suggest that excess water as h 3 o occupies vacant a site positions during stable isotope exchange and displaces ar causing lowering of the k ar ages this process occurs below the normally accepted closure temperature for ar in hornblende and is not detectable by optical or x ray investigation of the mineral this process may not be unique to connemara hornblendes and so is of potential importance to geochronology in other metamorphic terranes

late quaternary tectonic and sedimentary history of outer izmir and candarli bays western turkey abstract air gun and 3 5 khz seismic profiles from the eastern aegean sea off turkey show that the continental shelf of outer izmir and candarli bays is formed by several superimposed deltaic sequences during times of lowered sea level associated with late quaternary glaciations deltas prograded seaward more than 60 km from their present positions foreset progradation ceased with the rise of sea level in interglacial and post glacial times and deltas were reestablished far inland in drowned river valleys these major transgressions resulted in unconformities within the superimposed prograded delta sequences the most recent three unconformities are correlated with the beginning of oxygen isotope stages 5 3 and 1 and provide chronostratigraphic markers for a detailed analysis of sedimentation patterns in the late quaternary the coastal shelf and basins are subsiding at an average rate of about 1 m per 1000 years this tectonic subsidence manifests itself as widespread normal block faulting which can be related to the pre miocene structural framework of the region

strike slip faulting as a trigger mechanism for overpressure release through piercement structures implications for the lusi mud volcano indonesia piercement structures such as hydrothermal vent complexes pockmarks and mud volcanoes are found in various geological settings but are often associated with faults or other fluid focussing features this article aims to investigate and understand the mechanisms responsible for the formation of piercement structures in sedimentary basins and the role of strike slip faulting as a triggering mechanism for fluidization for this purpose four different approaches were combined fieldwork analogue experiments and math

modern and late quaternary clay mineral distribution in the area of the se mediterranean sea the present day clay mineral distribution in the southeastern levantine sea and its borderlands reveals a complex pattern of different sources and distribution paths smectite dominates the suspended load of the nile river and of rivers in the near east illite sources are dust bearing winds from the sahara and southwestern europe kaolinite is prevalent in rivers of the sinai in egyptian wadis and in saharan dust a high resolution sediment core from the southeastern levantine sea spanning the last 27 ka shows that all these sources contributed during the late quaternary and that the nile river played a very important role in the supply of clay nile influence was reduced during the glacial period but was higher during the african humid period in contrast to the sharp beginning and end of the african humid period recorded in west african records 15 and 5 5 ka our data show a more transitional pattern and slightly lower nile river discharge rates not starting until 4 ka the similarity of the smectite concentrations with fluctuations in sea surface temperatures of the tropical western indian ocean indicates a close relationship between the indian ocean climate system and the discharge of the nile river

response of th u in deep labrador sea sediments odp site 646 to changes in sedimentation rates and paleoproductivities the labrador sea is a particularly suitable high latitude basin for investigating u and th behavior in deep sea sediments during the late quaternary the cyclic development and decay of huge ice sheets on adjacent land masses resulted in large amplitude changes in sedimentation rates and organic paleoproductivities the resulting magnification of u and th response is well illustrated by high resolution studies on piston cored sediments from the greenland continental rise at ocean drilling program leg 105 site 646 spanning isotopic stages 8 to 1 the results show a clear positive correlation of sup 238 u sup 232 th ratios with organic paleoproductivity indicators e g dinocyst due to u uptake in the water column and or during the early diagenesis of organic matter responding to carbon fluxes and to their climate forcing sup 230 th excesses over sup 234 u exceed the theoretical value of the sup 230 th rain from the overlying water column indicating lateral input possibly from the greenland slope and shelf because these horizontal fluxes of sup 230 th may be partly controlled by physical parameters sup 230 th excesses cannot be unequivocally correlated with sedimentation rates and or productivity as reported elsewhere in this subarctic basin characterized by low overall organic carbon burial the sup 238 u sup 232 th ratio appearsmore to be a sensible geochemical indicator of organic activity and paleoproductivity less

abnormal carbonate diagenesis in holocene late pleistocene sapropel associated sediments from the eastern mediterranean evidence from emiliania huxleyi coccolith morphology in studying the holocene late pleistocene record of the eastern mediterranean considerable emiliania huxleyi size shape variation not clearly assignable to primary or secondary calcification was observed accordingly different morphotypes were distinguished by light microscope lm a subsequent scanning electron microscope sem analysis of selected samples has indicated that emiliania huxleyi coccoliths are variably affected by carbonate diagenesis in these sediments a series of diagenetic stages were qualitatively defined comprising well preserved specimens three overgrowth og1 to og3 and one etching e1 stage comparing sem and lm observations a tentative correlation between the e huxleyi calcified lm morphotypes and e huxleyi sem overgrowth stages is proposed here our study not only indicates that emiliania huxleyi coccoliths are strongly influenced by carbonate diagenesis but also that they show effects of carbonate precipitation and dissolution much more clearly than other coccoliths the relative abundances of the different lm morphotypes were used to define an e huxleyi overgrowth index exo that qualitatively estimates carbonate precipitation dissolution on coccoliths in this sediment this resulted in definition of five diagenetic intervals d1 to d5 deposition of sapropel s1 was a time of good preservation with variable dissolution and no overgrowth of e huxleyi coccoliths whereas calcite overgrowth was high during the last glacial maximum lgm and interglacial period and to a lesser extent during the younger dryas and through the last 5 ka d 2004 elsevier b v all rights reserved

distribution patterns of dinoflagellate cysts and other organic walled microfossils in recent norwegian greenland sea sediments dinoflagellate cysts and other organic walled microfossils have been studied in recent surface sediments from the entire norwegian greenland sea more than 30 taxa have been recognized of which only few show a distinct distribution pattern and allow description of four assemblages the occurrence of most taxa is related to the relatively warmer waters of the norwegian sea algidaspaeridium minutum s 1 brigantedinium simplex and impagidinium pallidum are the only species showing a preference for colder water masses two species i pallidum and nematosphaeropsis labyrinthus are mainly restricted to the oceanic environment whereas the other species have also been reported from neritic environments in previous studies due to the limited knowledge of the ecological and sedimentological factors influencing the occurrence of dinoflagellate cysts in oceanic environments their distribution in recent sediments can be only related to surface water masses in a broad sense although the distribution of assemblages correlates with specific surface water masses comparison with assemblages recovered from sediment traps deployed basinwide in the norwegian greenland sea dale and dale 1992 revealed some major discrepancies in species composition and percentage abundances the differences cannot be explained with certainty at the moment although there is some evidence that transport of dinoflagellate cysts and other fossilizable microplankton in water masses by currents in sea ice and sediments may modify the assemblages found in recent oceanic surface sediments from the norwegian greenland sea

coccolithophore assemblages during the holocene climatic optimum in the ne mediterranean aegean and northern levantine seas greece paleoceanographic and paleoclimatic implications recent paleoceanographic findings suggest that during the holocene ne mediterranean climate was less stable than previously thought several recently generated aegean paleoceanographic records of sapropel s1 suggest that during the holocene short term potentially global cooling episodes reflecting the n atlantic climatic fluctuations and possibly related to solar variability are superimposed on the underlying regional subtropical tropical control on the hydrography and ecosystems detailed quantitative analyses of coccolithophores have been performed on the deep sea deposits of the ne mediterranean sea four gravity core records from north aegean sea sl 152 se aegean ns 14 ns 18 and south cretan continental margin northern levantine sea hcmr 2 22 respectively with a focus on the regional expression of sapropel s1 deposition in all sites higher values of florisphaera profunda helicosphaera carteri braarudosphaera bigelowii and the increase of stratification s index within sapropel intervals can be interpreted as the result of elevated marine production in the deep photic zone and enhanced inflow of fresh water input during the s1 period the stratification s index is significantly higher in the north aegean in respect to se aegean and the south cretan margin scm reflecting increased coccolithophore productivity at the lower photic zone being associated with a remarkably stratified water column the concomitant increased presence of b bigelowii indicates the prominent riverine input in the north aegean basins and possible influx of black sea waters after 9 0 ka bp consequently the increased stratification of the water column is linked to the significant freshening of the north aegean surface waters particularly during the early stages of the holocene climatic optimum s1a depositional interval a series of cooling events detected towards the end of sapropelic conditions 7 2 ka bp mostly in the north aegean site may be linked to outbursts of cold northerly air masses and relevant pulses in the deep intermediate water ventilation that caused the enhancement of surface marine productivity and the temporary cessation of s1 at 8 0 ka bp in contrast in the se aegean and the northern levantine sea the water column remains still warm and stratified influenced by moderate fresh water input for at least 1 more ky

pliocene holocene evolution of depositional conditions in the eastern mediterranean role of anoxia vs productivity at time of sapropel deposition a multiproxy geochemical study of nine sapropel layers from odp hole 964a odp leg 160 in the eastern mediterranean spanning the pliocene holocene time interval provides new insights into the evolution of sapropel deposition paleoenvironmental proxies were used for reconstruction of productivity ba derived from marine barite oxygen conditions trace metal ratios and sedimentary regime clay minerals detrital elements these proxies reveal a significant increase in river runoff relative to decreasing aeolian input during sapropel deposition over the whole time interval ba excess supports the argument that a significant increase in export productivity is the main triggering mechanism for sapropel deposition although preservation also played an important role furthermore major differences exist in depositional conditions including both oxygenation and productivity since the pliocene productivity fluctuated substantially and was higher during the pliocene and pleistocene than during the holocene at the same time decreasing oxygen availability parallels the enhanced productivity dysoxic to anoxic conditions appear to coincide with marine productivity maxima thus suggesting that oxygen depletion may be linked to greater consumption rather than restricted circulation this correspondence supports the hypothesis that productivity fluctuations resulting from climate oscillations were the main cause of enhanced organic matter contents and also a main controlling factor for reduced oxygen availability

clay mineral distribution in last glacial holocene sediment cores from the eastern marmara sea cinarcik basin izmit gulf transition nw turkey multisources and transport paths in a two way flow system abstract the regional variations in grain size xrd bulk and clay mineral distribution in 97 sediment samples from 6 gravity cores obtained from 20 to 300 m water depths have been investigated to reveal source and transportation patterns as well as the effects of climatic and sea level changes during the last 25 000 14 c bp in the eastern marmara sea ems nw turkey the major proportions of sediments in the ems consist of silt 20 83 and clay 17 90 whereas sand and gravel abundances rarely exceed 10 of the bulk minerals 10 a micas 23 55 and feldspars 17 55 dominate over quartz 10 21 and calcite 10 26 smectites 23 62 illite 18 36 chlorites 6 21 kaolinite 2 20 and 14s 14c mixed layer minerals 0 27 constitute the principal clay mineral assemblages both bulk and clay mineral assemblages in the ems are similar to those found in the izmit gulf on the southern marmara shelf at the marmara aegean approaches and the southern black sea this would suggest that there is no distinct source for mineral assemblages of the study area outside the marmara basin the concentrations of clay fractions and clay mineral assemblages tend to increase or decrease with depth in the cores but this is limited to some intervals and not to entire sections in the cores this distribution pattern therefore represents rather local sources of provenance and surrounding fluvial drainage basins together with dilution and distribution effects by current transport processes rather than the expected paleoclimatic features and sedimentary input by inflowing black sea and aegean sea water masses throughout the last glacial to holocene

the lusi mud volcano triggering controversy was it caused by drilling abstract following the yogyakarta earthquake on may 27th 2006 the subsequent eruption of a mud volcano has been closely observed and analyzed by the geological community the mud volcano known as lusi began erupting near the banjarpanji 1 exploration well in sidoarjo east java indonesia lusi offers a unique opportunity to study the genesis and development of a mud volcano for the first time this paper presents all raw and interpreted drilling data so any interested party can perform their own assessment our study suggests that lusi mud volcano was a naturally occurring mud volcano in an area prone for its mud volcanism pressure analysis done on the banjarpanji well shows that the pressure exerted at the well is lower than the fracture pressure at the last casing shoe and suggests that the well was intact and did not suffer an underground blowout this is further supported by evidence and observation made during drilling such as circulation was done on an open bop and subsequent relief wells sonan and temperature log runs this study offers a different alternative to earlier hypothesis that events at the banjarpanji well were the trigger for the lusi mud volcano more work is needed by the scientific community to study the sequence of events in order to explain and clarify the real trigger of lusi