evidence for cavity dwelling microbial life in 3 22 ga tidal deposits cavities are considered plausible and favorable habitats for life on early earth in such microenvironments organisms may have found an adequate protection against the intense ultraviolet radiation that characterized the archean ozone free atmosphere however while there is clear evidence that benthic life existed in the paleoarchean the oldest traces of cavity dwelling microbes coelobionts have been found in neoarchean rocks here we present the results of a detailed investigation of early silicified cavities occurring in the oldest well preserved siliciclastic tidal deposits the 3 22 ga moodies group of the barberton greenstone belt south africa downward growing microstromatolitic columns composed of kerogenous laminae are commonly present in planar bedding parallel now silica filled cavities that formed in sediments of the peritidal zone in situ 13cpdb pdb peedee belemnite measurements of the kerogen range from 32 3 to 21 3 and are consistent with a biogenic origin scanning electron microscopy analysis of the silicified cavities shows well preserved chains of cell sized molds that are interpreted as fossil filamentous microorganisms the geological context the morphology of the microstromatolites the 13c composition of the kerogen and the presence of microfossils all suggest that a microbial community inhabited the cavities these results extend the geological record of coelobionts by 500 m y supporting the view that cavities were among the first ecological niches to have been occupied by early microorganisms

meltwater floods into the black and caspian seas during heinrich stadial 1 abstract deglaciation of the eurasian ice sheet dispensed vast amounts of meltwater laden with red brown clay into black and caspian sea s freshwater lakes between 16 350 and 15 400 calendar years bp the arriving sediment had a mineral composition and strontium neodymium isotope signatures 87sr 86sr and end consistent with the crystalline bedrock that lay beneath the ice sheet as opposed to sources from landscapes crossed by the rivers that carried meltwater to the lakes the magnitude and rapidity of the shifts of 87sr 86sr and 18o in shells of ostracods and mollusks an eight fold increase in sediment accumulation rate and a plunge of 1250 14c years in the radiocarbon reservoir age indicate a volume of meltwater sufficient to have replaced most or all of the pre existing lake water if the release of 25 000 km3 of water from the caspian into the black sea s new euxine lake was abrupt by judging the magnitude of erosion in the floor of the manych strait spillway this event qualifies as a megaflood deeply scoured furrows channel floor bars and swaths of mounds 5 20 km in length and 5 20 m in height are reminiscent of scabland landscapes the meltwater is coincident with heinrich stadial 1 when the alpine and eurasian ice sheets re advanced and temperatures of the black sea s lake surface remained cold sand grains within the red brown clay indicate they were transported by lake surface ice

oxygen and carbon isotopes in modern fresh water ostracod valves assessing vital offsets and autecological effects of interest for palaeoclimate studies abstract the isotopic composition of modern benthic ostracod and mollusc carbonate the oxygen isotope composition of lake water 18ow the carbon isotope composition of dissolved inorganic carbon 13cdic and water temperatures were monitored during a year at different water depths in two lakes ammersee and starnberger see southern germany the aim was to test whether the valves are built in isotopic equilibrium and how seasonal water temperatures are recorded in the shells we find systematic offsets between 18o of valve carbonate compared to 18o expected for a theoretical calcite formed in isotopic equilibrium offsets are higher than 2 for different species of the candona group 1 5 for cytherissa lacustris and around 0 8 for limnocythere inopinata and darwinula stevensoni they seem to be constant for all instars of a species and temperature independent mean water temperatures of the calcification period are readily reflected in the valve 18o if corrected for the offsets 13c of valve carbonate is mainly controlled by 13c of the dissolved carbonate in ambient lake water but seems to be biased by micro habitat effects and vital offsets the study provides information on the seasonality of valve formation thus potentially allowing the quantification of temporal and spatial water temperature gradients from specific 18o records

lamination of swampy rivulets rivularia haematites stromatolites in a temperate climate abstract swampy rivulets rivularia haematites d c agardh stromatolites were collected from the same site on the plateau de langres chaugey france over a seven year period specimens were studied in thin sections in culture media under varying conditions of temperature and illumination and by scanning electron microscope sem in order to investigate the processes of calcification and lamination new sem observations confirm the polycrystalline structure of the lamellae reported by the authors and show that the crystals composing these lamellae are elongate and aligned in the same direction as the filaments linked by them the lamellae were also isolated in transverse sections under sem and found to correspond to what under the light microscope appear to be honeycomb structures the diameter of alveoli can be the same as that of a false branching their walls formed by the outer sheath have a dense network of microfibrils these observations confirm the formation of calcitic lamellae at the false branching points and in contact with the microfibrils of the outer sheath confirmation of earlier hypotheses was sought through observation in thin section of the stromatolites collected over seven years micritic dark laminae are thought to form in three stages i formation of a dark lamina by formation of a false branching zone in the wet season ii initial calcification in this zone as microsparitic and sparitic lamellae during even a short dry spell and iii subsequent bacterial micritization of the lamellae during an extended warm dry season the sparitic light laminae form around the hair bearing regions lamination was first considered with regard to the annual radial growth rate of r haematites the thin section may display either a single dark lamina for two years growth or a dark lamina thicker than the annual growth rate examination of local meteorological data accounts for the first phenomenon by a wet spell of more than 13 months and the second by a warm dry period of one month it may therefore take several years for a couplet to form as growth of the cyanobacterial colony is influenced by climatic variations the different calcification phenomena were also correlated with dry spells these interpretations are consistent with results obtained by experiments

a record of late quaternary continental weathering in the sediment of the caspian sea evidence from u th sr isotopes trace element and palynological data abstract this study presents combined mineralogical chemical isotopic 87sr 86sr and u th disequilibria series and palynological analyses on bulk sediments and on distinct mineral phases carbonates and clays from a 10 m long core drilled in the southern caspian sea and containing a late pleistocene and early holocene record the data allowed identifying 1 the main variations in sedimentation 2 the processes causing these variations 3 the modification of erosion vs weathering and 4 the influence of climatic and or caspian sea level changes in the region since the late pleistocene the chemical and mineralogical results allowed the division of the sedimentary sequence into three main units and a transition zone the lower unit unit u1 primarily consists of silicate and carbonate rich detritus sedimentation characteristics including observation of detritus in secular equilibrium are relatively constant within this unit and reflect mechanical erosion in a cold climate unit u1 probably corresponds to a glacial period when the vegetation cover was sparse and wind and river transport of pollen were strong subsequently global increase in temperatures has greatly modified the sedimentation in the caspian sea south basin biogenic sedimentation is higher in units u2 and u3 and detrital inputs varied from unit u1 variations in detrital input are likely to be caused by decreasing aeolian contribution and by relative changes in river volumes and origins the study of the bulk sediments clays and carbonates reflects an increase in chemical weathering since about 10 14c ka bp ago base of unit u2 in line with an increase in the vegetation cover our results suggest an evolution of continental weathering conditions in the catchment area of the caspian sea from dominantly mechanical physical erosion during the cold period to a continuous increase in weathering since the lateglacial period as climate improved which illustrates the strong relation between climate vegetation cover and weathering processes this paper also highlights how the u th disequilibrium series proxy combined with other geochemical and palynological studies could be a useful tool to record and constrain the modification of weathering regime in response to climatic and environmental changes at regional scale

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

dendritic calcite crystals formed by calcification of algal filaments in a vadose environment abstract uncalcified and calcified algae grow on and color walls of cavities that occur in karst breccia which fills pockets in the tertiary bluff formation of grand cayman island the calcified algae are important because the calcification has been achieved through the formation of dendritic calcite crystals although common in metals such branching crystals have not been widely recognized in naturally occurring calcite the dendritic calcite crystals are exactly like most dendritic crystals in that they have a primary needle or stem with secondary and tertiary branches most dendritic calcite crystals have an open treelike form and are easy to recognize as calcification proceeds the dendritic crystals become progressively filled in and are increasingly difficult to recognize as dendritic crystals filling of the dendritic crystals can result in two dimensional sheets or three dimensional columns assuming the three dimensional columnar dendritic crystals developed planar and or curving smooth surfaces then lacking other evidence they would be indistinguishable from normal columnar calcite crystals and their dendritic origin would be hidden variables thought to control dendrite crystal formation include a creation of localized highly supersaturated solutions leading to rapid rates of nucleation and crystal growth and b impurities in the form of organic molecules and other substances algae are excellent candidates for controlling a via their metabolism and contributing to b via their decay combining these ideas with the results of this study and with the known common occurrence of algae in many speleothemic environments provides an impetus for a reexamination of the origin of subaerially formed calcite crystals

glacial hydrologic conditions in the black sea reconstructed using geochemical pore water profiles abstract chloride and 18 o compositions of interstitial water extracted from a long sediment core retrieved from the nw coast of the black sea allowed us to constrain the main hydrologic changes of the back sea during the late pleistocene and holocene prior to its reconnection with the mediterranean sea through the marmara sea at approximately 9000 calendar yr before present 9 ka cal bp the black sea has evolved as a fresh to brackish water lake at the time of reconnection hydrologic changes were drastic bottom water salinities changed from a few psu practical salinity unit to 22 psu since solutes in the interstitial water column within sediments are advected and diffused the measured concentrations do not reflect those of past bottom waters in order to reconstruct these former concentrations we used an advection diffusion model different scenarios of bottom water chloride and 18 o variations were accounted for in this model in order to simulate present day vertical profiles for concentrations of interstitial water in order to compare them to measured ones the comparison suggests that the glacial black sea was a homogeneous freshwater lake with a 18 o of 10 and a salinity of 1 psu modern hydrologic conditions would only have been reached at 2 ka cal bp concomitant with the onset of coccolith rich thin layers that characterize modern basin sediments such delayed salinization over 7000 yr in the basin may have been due to higher precipitation during the early holocene we also simulated the impact of a catastrophic reconnection and a smoother reconnection both salinity scenarios lead to undistinguishable modelled present day profiles indicating that the precise impact of the last reconnection was lost due to the advection diffusion processes

the genesis of actively growing siliceous stromatolites evidence from lake specchio di venere pantelleria island italy this study documents the attributes of siliceous stromatolites growing in the lake specchio di venere on the volcanic island of pantelleria italy in a setting characterized by very shallow cold waters and pools and by scattered hydrothermal activity which exhales mainly co2 at emission point temperatures of 34 to 58 c the saturation indexes indicate that the lake waters are saturated with respect to tridymite cristobalite chalcedony and quartz and slightly undersaturated with respect to amorphous silica common roughly laminated and poorly lithified stromatolites show scanning electron microscope sem evidence for silicified microbial mat structures including biofilms filamentous and coccoid cells and extracellular polymeric substances eps the screening of bacterial 16s rrna libraries indicates that autotrophic and heterotrophic bacterial communities colonize surface and core levels of the stromatolites locally the stromatolites show a granular non porous fabric where filaments and silica sheets are not apparent inhomogeneity in the stromatolite fabric corresponds with varying dna content and different structures of the colonizing bacterial communities non porous stromatolite levels being microbially colonized to a lesser extent based on fourier transform ft raman and ft infrared investigations the laminated stromatolite contains early diagenetic tridymite in addition to amorphous silica opal a whereas the non porous stromatolite shows an essentially amorphous character the laminated stromatolite is thought to form at relatively low rates of silica precipitation and with a possible microbial mediation in terms of microbial cells and their eps accelerating the onset of amorphous silica nucleation it is suggested that high porosity probably favoured a consistent flux of silica rich fluids that triggered the opal a to tridymite transformation thus strengthening the preservation of biosignals non porous stromatolite growth could reflect temporal or localised changes in environmental conditions that caused variations in the degree of silica saturation in the lake waters inducing abiotic silica accumulation accelerated opal a deposition could have obscured primary filamentous fabrics and limited the flux of pore fluid needed for sustaining the process of silica maturation

formation processes of framboidal pyrite abstract pyrite framboid formation may be the result of four consecutive processes 1 nucleation and growth of initial iron monosulfide microcrystals 2 reaction of the microcrystals to greigite fe 3 s 4 3 aggregation of uniformly sized greigite microcrystals i e framboid growth and 4 replacement of greigite framboids by pyrite the uniform morphology uniform size range and ordering of the microcrystals in individual framboids as well as the range of observed framboid structures from irregular aggregates to densely packed spherical aggregates and polyframboids are consequences of these processes using dlvo theory derjaguin landau verwey and overbeek we have evaluated the stability of colloidal iron monosulfide suspensions with ionic strengths typical of marine and lacustrine waters in addition to van der waals attractive and double layer repulsive forces a term is included to account for the ferrimagnetic properties of greigite numerical models predict that magnetically saturated greigite particles 0 1 m in diameter will rapidly aggregate in either marine or fresh water the aggregation model is in agreement with the sequence of greigite formation followed by pyrite framboid formation established in a previous experimental study sweeney and kaplan 1973 and is consistent with the occurrence of framboids composed of other magnetic minerals e g greigite magnetite and magnesioferrite based on the temperature dependent magnetic properties of greigite and aging experiments in hydrothermal solutions this mechanism for framboid formation via precursor greigite could operate to temperatures of 200 c consistent with the occasional occurrence of pyrite framboids in the paragenesis of metalliferous ore deposits

unusual mixed silica carbonate deposits from magmatic hydrothermal hot springs savo solomon islands abstract the volcanic island of savo solomon islands hosts an active hydrothermal system discharging unusual alkaline ph 7 8 sulphate rich chloride poor fluid with variable admixtures of ca mg hco 3 rich fluid hot springs and their outflow streams precipitate a variety of deposits including travertine silica sinter and unusual mixed silica carbonate rocks travertine fabrics are dominated by ray crystal calcite associated with rapid abiotic precipitation from a supersaturated solution sinter is produced by evaporation of thermal waters and downstream samples contain preserved traces of micro organisms which potentially acted as templates for precipitation trace element chemistry of sinters and travertines includes anomalously high levels of te indicating a magmatic origin for a component fluid in the hydrothermal system springs are close to or at saturation with both calcite and amorphous silica increased contributions from the ca mg hco 3 end member favours calcite formation this fluid is of low temperature origin and as such is favoured by high rainfall mixed samples show cyclical changes between silica and carbonate precipitation potentially as a result of seasonal variation in rainfall supplementary material a spreadsheet of water and deposit chemical analyses is available at www geolsoc org uk sup18495

evolution of a dynamic paleo hydrothermal system at mangatete taupo volcanic zone new zealand abstract recent quarrying and active faulting at mangatete taupo volcanic zone tvz new zealand illuminate a rare spatial and temporal window on a dynamic late quaternary geothermal system detailed geological mapping stratigraphic logging ams 14 c dating and textural and mineralogical analyses were used to construct a complex history of hydrothermal volcanological and tectonic activity from 36 to 2 ka extinct surface hydrothermal manifestations occur over a 2 km 2 area and include in situ siliceous sinters distributed on normal fault terraces an inferred hydrothermal eruption breccia heb containing acid etched sinter blocks another probable heb that was bathed in silicifying thermal fluids and sinter clasts that were entrained in a debris flow associated with a volcanic ash event preserved sinter textures typical of near neutral ph alkali chloride spring discharge channels aprons terraces and affiliated marshes comprise plant rich palisade tufted bubble mat and domal stromatolitic fabrics in addition a packed fragmental sinter facies is shown herein to constitute silicified microbial mats that were broken transported and deposited as point bar deposits in thermal spring fed streams moreover four unusual siliceous sinter fabrics vuggy globular spongy scalloped and arcuate wavy layered are interpreted to have formed from local acid sulfate chloride thermal springs possibly associated with paleo fumaroles the reconstructed history of paleo hydrothermal activity indicates that the oldest sinters 36 ka at mangatete developed in alkali chloride hot springs but then underwent post depositional alterion overprinting by acid sulfate steam condensate and were dismembered possibly by a hydrothermal eruption low ph hot spring discharges forming the unusual inferred acid sinter fabrics were localized in the same area a shift in paleo hydrology is evidenced by unaltered alkali chloride sinters dated between 22 and 3 ka a cluster of sinter dates between 22 7 and 20 7 ka denote thermal fluid emissions around the time of the okareka eruption 22 1 ka an 11 kyr gap in sinter ages followed which overlaps with a time of relative quiescence in local fault movement in between the rotorua and rotoma eruptions as determined from previous paleo seismicity studies on the whirinaki fault in the mangatete area at 9 4 ka hot spring activity in thermally fed streams slightly post dated the rotoma eruption 9 5 ka the locations and ages of the youngest post 9 4 ka alkali chloride sinters and silicified paleosols in relation to whirinaki fault movements indicate an overall westward migration of siliceous spring discharge dated charcoal 1 8 kyr in ash at the base of a locally extensive volcaniclastic debris flow containing sinter blocks of a range of ages and mineralogical maturity suggests its affiliation with the taupo eruption mangatete sinters occur along sw ne striking faults parallel to the regional trend of the tvz which dissect the topography into stepped terraces inferred basement cross faults in the study area i e structural lineaments orthogonal to this trend may have served as fluid pathways at depth initiating and maintaining hydrothermal activity at mangatete for more than 30 kyr within the larger ngakuru graben 150 km 2 the ages and distributions of sinters and hydrothermal eruption breccias including those at mangatete show that significant hydrothermal activity occurred for more than 60 kyr in an area lacking such activity today thus mangatete retains a rare stratigraphic record within the tvz sinter archive of changing geothermal fluids resulting from shifts in paleo phreatic water levels moreover although limited the presented age data imply a relationship among seismic activity volcanic ash fall events and the occurrence of permeable pathways for upward migration of thermal fluids finally whereas currently active tvz geothermal fields appear to be stable over tens of thousands of years or more the fossil hydrothermal systems in the wider mangatete area demonstrate the possibility of much greater temporal variability in the lateral expression of local surface manifestations of thermal fluid discharge through time

late glacial holocene palaeoceanography of the sea of marmara timing of connections with the mediterranean and the black seas abstract stratigraphic analysis of late quaternary sediments of the sea of marmara basin smb indicates that it was a freshwater lake during the late glacial to ca 12 000 yr bp depositing sediments with a neoeuxinian fauna characteristic of the black sea basin at ca 12 000 yr bp it was inundated by the mediterranean waters and gradually converted into a marine realm as indicated by the presence above the neoeuxinian sediments of a mixed layer containing both marine and freshwater fauna a sapropelic sediment layer was deposited between 10 600 and 6400 yr bp under suboxic bottom water conditions this layer roughly corresponds in time to s1 sapropel unit of the eastern mediterranean suggesting a common origin its presence in the smb therefore supports the hypothesis that a large influx of freshwaters from the black sea was an important factor in sapropel formation in the eastern mediterranean a second sapropelic layer formed in the smb during 4750 to 3200 yr bp the earliest known record of mediterranean water in the bosphorus is at ca 5300 yr bp suggesting a later marine inundation than the 7150 yr bp event suggested by ryan and co workers an abrupt drowning of black sea shelf at 7 5 kyr bp geo eco marina 2 proc int workshop on fluvial marine interactions mainas romania 1 7 october 1997 pp 115 125 and ryan w b f pitman iii w c major c o shimkus k moskalenko v jones j a dimitrov p gorur n sakinc m yuce h 1997b an abrupt drowning of black sea shelf mar geol 138 1997 119 126 this implies that either earlier marine connections with the black sea were through a different waterway or the earlier marine record in the strait has been eroded the present two layer flow system was established at 4000 yr bp

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

further evidence of abrupt holocene drowning of the black sea shelf a 1999 survey of the black sea continental shelf off the north central turkish seaport of sinop using a side scan sonar small remotely operated vehicles and a series of dredge lowerings located inspected and sampled an exposed high energy paleoshoreline at a depth of 155 m radiocarbon dating of mollusk shells collected from this ancient beach revealed that the marine flooding of the black sea took place between 7460 and 6820 yr b p all ages are reported in radiocarbon years not calendar years without correction for reservoir age or dendro calibration changing it from a lacustrine to marine environment this relic surface remained in contact with the bottom waters of the black sea for a long period of time before being draped by a thin layer of sapropel mud wood samples recovered from this same location were very well preserved and yielded dates as old as 3580 yr b p q 2000 elsevier science b v all rights reserved

depositional facies and diagenetic alteration in a relict siliceous hot spring accumulation examples from yellowstone national park u s a abstract siliceous precipitates from portions of an 11 m long core drilled through a relict yellowstone hot spring deposit provide valuable insights into the diagenetic facies in this hydrothermal environment most of the core consists of relatively low temperature siliceous sinter containing abundant plant diatom and microbial fossilized remains derived from the distal debris apron and discharge channel flowpath of the hot spring a few intervals contain stromatolitic horizons analogous to modern siliceous pool margin and discharge channel flowpath facies despite the abundance of silicified microbial remains e g silicified stromatolitic horizons as well as individual filamentous microbes diatoms distinctive organic biomarkers are not preserved in the core the apparent lack of distinctive organic biomarkers is attributable to pervasive diagenetic alteration in the presence of high temperature chemically reactive fluids numerous diagenetic features have been superimposed on the siliceous sinter especially considering the relatively shallow depths of burial the uppermost interval 0 to 1 2 m consists of highly porous siliceous sinter opal a and interbedded travertine amorphous manganese oxides and sparry calcite cements are present and are irregularly distributed throughout this interval below is a diagenetic facies 4 8 to 5 3 m that consists of opal ct and minor chalcedony the most pervasive diagenetic alteration in the core is the 6 8 to 11 2 m depth interval where abundant zeolites mordenite heulandite bladed cristobalite lepispheres chalcedony cements and calcite veins are present judging by the assemblage of plant and diatom remains most of this pervasive alteration is superimposed on relatively low temperature siliceous sinters and is likely the result of migration of hot waters through this interval the paragenesis of all these intervals is very complex involving numerous episodes of mineral precipitation and dissolution this diagenetic alteration is facilitated by the porous nature of the siliceous sinter thermal convection of superheated fluids or steam strongly oxidizing spring waters and fluctuating hydrochemical regimes rapid dissolution and or replacement of organic matter indicates that standard morphological means e g petrographic identification of body fossils may be the best method by which to identify that organisms were previously present in ancient hot spring accumulations

diagenetic barium cycling in black sea sediments a case study for anoxic marine environments high resolution sedimentary records of major and minor elements al ba ca sr ti total organic carbon toc and profiles of pore water constituents view the mathml sourceso42 ch4 ca2 ba2 mg2 alkalinity were obtained for two gravity cores core 755 501 m water depth and core 214 1686 m water depth from the northwestern black sea the records were examined in order to gain insight into the cycling of ba in anoxic marine sediments characterized by a shallow sulfate methane transition smt as well as the applicability of barite as a primary productivity proxy in such a setting the ba records are strongly overprinted by diagenetic barite baso4 precipitation and remobilization authigenic ba enrichments were found at both sites at and slightly above the current smt transport reaction modeling was applied to simulate the migration of the smt during the changing geochemical conditions after the holocene seawater intrusion into the black sea based on this sediment intervals affected by diagenetic ba redistribution were identified results reveal that the intense overprint of ba and baxs ba excess above detrital average strongly limits its correlation to primary productivity these findings have implications for other modern and ancient anoxic basins such as sections covering the oceanic anoxic events which ba is frequently used as a primary productivity indicator our study also demonstrates the limitations concerning the use of baxs as a tracer for downward migrations of the smt due to high sedimentation rates at the investigated sites diagenetic barite fronts are buried below the smt within a relatively short period thus relict barite fronts would only be preserved for a few thousands of years if at all

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

formation pathways of light hydrocarbons in deep sediments of the danube deep sea fan western black sea abstract we report on the geochemistry of light hydrocarbons and pore water in sediments down to 147 m below seafloor mbsf at two sites within the gas hydrate stability field of the danube deep sea fan black sea sediments were drilled with marum mebo200 and comprise the transition from limnic to the recent marine stage stable c n ratios mean 5 1 and 5 6 and 13c corg values mean 25 8 v pdb suggest relatively uniform bulk organic matter compositions in contrast pore water 2h and 18o values varied considerably from approx 120 to 30 v smow and from 15 to 3 v smow respectively these data pairs plot close to the global meteoric water line and indicate paleo temperature variations depletions of pore water in 2h and 18o below 40 mbsf indicate low temperatures and likely reflect conditions during the last glacial period s methane was much more abundant than the only other hydrocarbons found in notable concentrations ethane and propane c1 c2 c3 20 000 relatively constant 13c ch4 70 v pdb and 13c c2h6 52 v pdb values with depth indicate that methane and ethane are predominantly of microbial origin and that their formation was not limited by carbon availability in contrast 2h ch4 values varied in a large range approx 310 to 240 v smow with depth and positively correlated with trends observed for 2h h2o isotope separations 13c ch4 co2 2h ch4 h2o substantiate that microbial carbonate reduction cr is the prevalent methanogenic pathway throughout the sediments irrespective of their geochemical history remarkably in 13c ch4 2h ch4 diagrams widely used samples characterized by 2h ch4 values more negative than approx 250 plot out of the field assigned for pure cr we conclude that assignments of microbial methanogenic pathways based on classical interpretations of 13c ch4 2h ch4 pairs can lead to misinterpretations as severe 2h depletions of methane formed through microbial cr can result from 2h depletions of the pore water generated during low temperature climatic periods

first high resolution marinopalynological stratigraphy of late quaternary sediments from the central part of the bulgarian black sea area abstract spores pollen and dinoflagellate cysts of late pleistocene and holocene sediments were analyzed from giant gravity core 18 from the black sea continental slope recovered from a water depth of 971 m the investigated length of the core is 203 5 cm it includes 3 lithological units light grey clay sapropels and coccolith bearing ooze the core was sampled at 5 10 cm intervals sampling of the interval 141 5 126 cm was carried out at every cm ams radiocarbon dating of bulk organic carbon was performed on 18 selected sediment layers this chronological data allowed the first high resolution pollen stratigraphy of late quaternary sediments from the western black sea area to be presented the percentage spore pollen diagram is divided into 6 local pollen assemblage zones the trends in the vegetation dynamics and climate changes and the early history of migration of the majority of the arboreal taxa that nowadays occur in the eastern balkan range were traced out the palynological record suggests that open oak forests were spread in the eastern balkan range at the beginning of the holocene and shows early migration of the major temperate arboreal species such as quercus ulmus tilia and carpinus betulus this vegetation palaeosuccession continues with the spreading of mixed oak forests from 8950 until 2620 cal bp 8650 40 until 3120 35 14c bp followed by destructive changes due to human impact and climate deterioration a cooling of holocene climate that is well known in the north atlantic region as the 8200 yrs cold event is identified for the first time in marine records from the bulgarian black sea area the assemblages of dinoflagellate cysts and acritarchs were investigated to provide a reconstruction of surface seawater salinity and surface seawater temperature changes two main dinoflagellate cyst assemblages one dominated by fresh to brackish water species such as spiniferites cruciformis and pyxidinopsis psilata and a subsequent one that is characterized by euryhaline marine mediterranean species such as lingulodinium machaerophorum spiniferites belerius spiniferites bentorii operculodinium centrocarpum and acritarchs cymatiosphaera globulosa testified a change in sss from low salinity

ice dammed lakes and rerouting of the drainage of northern eurasia during the last glaciation during the quaternary period ice sheets centred over the barents and kara seas expanded several times onto mainland russia and blocked northflowing rivers such as the yenissei ob pechora and mezen large ice dammed lakes with reversed outlets e g toward the caspian sea formed south of these ice sheets some lakes are reconstructed from shorelines and lacustrine sediments others mainly from ice sheet configuration ice dammed lakes considerably larger than any lake on earth today are reconstructed for the periods 90 80 and 60 50 ka the ages are based on numerous optically stimulated luminescence osl dates during the global last glacial maximum lgm about 20 ka the barents kara ice sheet was too small to block these eastern rivers although in contrast to the 90 80 and 60 50 ka maxima the scandinavian ice sheet grew large enough to divert rivers and meltwater across the drainage divide from the baltic basin to the river volga and that way to the caspian sea climate modelling shows that the lakes caused lower summer temperatures on the continent and on the lower parts of the ice sheet the final drainage of the best mapped lake is modelled and it is concluded that it probably emptied within few months we predict that this catastrophic outburst had considerable impact on sea ice formation in the arctic ocean and on the climate of a much larger area c 2003 elsevier ltd all rights reserved less

late glacial to holocene climate and sedimentation history in the nw black sea abstract gravity cores from the continental slope in the northwestern black sea were studied using high resolution stable isotope grain size and xrf scanning data the measurements provide a 30 000 years ams 14c dated record of variations in the hydrological regime of the black sea and give insight into changing paleoenvironments in the surrounding areas stable climatic conditions during the last glacial maximum were followed by a series of meltwater pulses most likely originating from the scandinavian ice sheet between 18 000 and 15 500 yr bp 1 this meltwater input rose the level of the caspian sea to a point that caspian water could spill into the black sea via the manych depression north of the caucasian mountains high frequency oscillations in the xrf data during this period suggest a probable link to the arctic climate regime later during the bolling allerod and the early holocene prevailing high temperatures led to authigenic calcite precipitation through increased phytoplankton activity interrupted by the younger dryas and the 8200 yr bp cold event with dominant clastic sedimentation

late glacial to holocene paleoenvironmental evolution of the black sea reconstructed with stable oxygen isotope records obtained on ostracod shells high resolution stable oxygen isotope d 18 o on ostracod shells xrf scanning and bulk grain size data obtained on a transect of 6 gravity cores from the continental slope in the northwestern black sea give new insight into the hydrological evolution of the black sea since the last glacial maximum lgm stable climatic conditions during the lgm were followed by a series of meltwater pulses between 18 and 15 5 kyr bp that resulted in temporary isotopic depletion of the black sea waters subsequently steadily increasing d 18 o values in all cores are mainly caused by isotopically enriched precipitation at the onset of the allerod bolling warm period a comparison of the major trends in d 18 o at different water depths suggests evaporation driven deep water formation since 14 5 kyr bp while the two shallowest cores from 168 and 465 m water depth were under the influence of increased warming in the upper water column since 14 5 and 12 5 kyr bp respectively the core from 168 m depth seems to be additionally influenced by freshwater input of the danube this core provides a high resolution record from the younger dryas allerod boundary and suggests that a nao like climate mode was governing the interannual variability in the run off of the danube which implies that this climate mode has been a persistent climatic feature over central europe the inflow of saline mediterranean waters occurs between 9 and 8 kyr bp where a merging of all d 18 o records signals an initial homogenisation of the water column

hydrological changes in eastern europe during the last 40 000 yr inferred from biomarkers in black sea sediments the black sea is connected to a large drainage area including the european russian plain part of the alps and southeastern europe to study the hydrological changes in this basin over the last 40 000 years we measured specific terrigenous biomarkers for wetland vegetation in well dated sediments from the northwestern black sea spanning the last glacial period lacustrine phase and the holocene marine phase low abundances of these biomarkers are observed during the north atlantic ice melting and cooling events known as heinrich events 4 to 2 the last glacial maximum and the younger dryas event increased biomarker inputs characterize the mild climate phases known as dansgaard oeschger interstadials the bolling allerod and preboreal warmings indicating increased erosion due to permafrost degradation higher primary productivity and or wetland extension in the drainage basin the final retreat of the fennoscandian ice sheet from the russian plain occurs during the early part of heinrich event 1 and is characterized by increased biomarker concentrations in a typical series of four deglacial clay layers for the last glacial period the correspondence in timing between the biomarker records and the atmospheric ch4 record from ice cores suggests an important ch4 contribution due to boreal permafrost thawing and wetland emission

a post younger dryas black sea regression identified from sequence stratigraphy correlated to core analysis and dating the north western black sea shelf is the widest continental shelf of the black sea where the danube delta prodelta system includes important records on the black sea water level fluctuations this study integrates newly acquired high resolution single channel seismic reflection profiles and calypso piston cores recovered along a transect extending from the danube delta deep into its deep sea fan the correlated results provide information on the late quaternary architecture of the danube black sea shelf and on the role of global glacio eustatic fluctuations on the building of the danube delta prodelta the sedimentary sequences in the black sea are strongly affected by water level changes for the whole duration of late glacial holocene period the level of the black sea was controlled by the regional climate modifications rather than the global eustatic changes the seismic sequences recognized on a very high resolution seismic profile were dated by two calypso piston cores based on the obtained data during the last glacial maximum the black sea was a land locked lake with the level below 120 m in the course of the deglaciation the lake level rose up to 40 m which is confirmed by occurrence of the prodelta lobes formed after the rise in water level originated from the melt water following the younger dryas 11 000 8500 c 14 bp there occurred a new level lowering to the level of 100 m identified by the forced regression deposits recorded on the romanian shelf this last lowstand previously recognized by a pronounced shoreline with a characteristic beach profile and a belt of coastal dunes is also indicated by the prodelta at 100 m depth all these coastal features as well as the incised anastomosed channel system remained preserved on the shelf resulting from a rapid ultimate transgression starting immediately after 8500 c 14 bp c 2010 elsevier ltd and inqua all rights reserved

an abrupt drowning of the black sea shelf abstract during latest quaternary glaciation the black sea became a giant freshwater lake the surface of this lake drew down to levels more than 100 m below its outlet when the mediterranean rose to the bosporus sill at 7 150 yr bp 1 saltwater poured through this spillway to refill the lake and submerge catastrophically more than 100 000 km2 of its exposed continental shelf the permanent drowning of a vast terrestrial landscape may possibly have accelerated the dispersal of early neolithic foragers and farmers into the interior of europe at that time

impact of seasonal changes on the formation and accumulation of soft siliceous sediments on the discharge apron of geysir iceland abstract unconsolidated highly porous permeable siliceous sediments found in shallow water pools on the middle and distal parts of geysir s discharge apron are formed of cryogenic opal a coa opal a spheres opal a cement silicified microbes and detrital lithic grains silicified leaves and silica coated grass stems and twigs are locally present with these pool sediments and microbial mats commonly cover the sediment surface partially consolidated layers 0 5 cm thick form when the constituent grains are bound together by filamentous microbes exopolysaccharides and or opal a cement most components of the sediment can be related to processes that are controlled largely by seasonal variations low temperatures in winter promote freezing of the medial to distal discharge waters and lead to formation of coa in ice when the ice melts the released coa grains become part of the pool sediments microbial mats trap and bind sediment and provide templates for silica precipitation during spring and summer but become semi dormant during the constant darkness that iceland experiences during winter when the waters are sufficiently supersaturated opal a precipitates as spheres in the water column and cement in pool deposits in some pools seasonal changes are evident from the alternation of soft and hard partly cemented laminae elsewhere however the distinction between the different time dependent components is lost because they become superimposed on each other or as aperiodic changes in flow patterns affect different pools

depositional evolution of an extinct sinter mound from source to outflow el tatio chile siliceous sinter deposits from el tatio chile preserve a wide variety of depositional environments and biosignatures from high temperature 85 c vent proximal facies to distal deposits dominated by silicified microbial mats four cores were drilled into an el tatio sinter mound and associated distal apron to investigate changes in hydrothermal environments over geologic timescales sedimentary and geochemical analysis of multiple sinter cores records the initiation and accretion of diverse depositional features still observed today in el tatio facies adjacent to hydrothermal vents are dominated by laminated sinter crusts on the steep margins of a high temperature pool with sparse microbial preservation outer margins of the same pool contain extensive sinter columns up to ten centimeters in length precipitated during repeated cycles of pool overflow and subsequent evaporation low relief hydrothermal pools also form minor deposits within distal debris aprons and analogous pools are still active close to sampling locations debris aprons are dominated by palisade tufted and arborescent microbial fabrics with distinct mat textures revealing well preserved microfossils surficial deposits in all cores feature detrital rich and microbially influenced sinters overlying higher temperature facies indicating a relative decrease in hydrothermal activity over time geochemical proxies for hydrothermal fluids and de trital input match depositional interpretations based on sedimentary structures 14 c ages from core deposits extend the mound s history by 11 000 years recording at least three thousand years of sinter deposition on top of glacial sandstones 13 337 10 232 y cal bp importantly this work provides a detailed depositional model unavailable through surficial sedimentology alone

short term soil formation events in last glacial east european loess evidence from multi method luminescence dating here we provide a robust luminescence chronology for stayky ukraine a reference profile in european late pleistocene loess stratigraphy based on optically stimulated luminescence osl dating on quartz 4 11 m 63 90 m and post infrared infrared stimulated luminescence pir irsl on polymineral fine grains for the bug loess unit the equivalent of marine isotope stage mis 2 results are in agreement between methods demonstrating that the suite of embryonic soils previously interpreted as reflecting climate variability similar to greenland interstadials gi actually date to 29 27 15 ka with most emplaced around or after 20 ka this temporal span is further confirmed by age depth modelling of available data apart from gi 2 no interstadial type climate events are recorded in greenland ice core data for that time interval as short term pedogenetic phases are also documented in records from central western europe there is a need for more research into the european mid latitude terrestrial environments response to mis 2 hydroclimate variability the dating of vytachiv paleosol previously debatably linked to various gi events within mis 3 resulted in ages of 40 4 ka and 53 4 ka at the lower transition and 26 2 ka to 30 2 ka in the overlying loess these ages indicate that the truncated vytachiv paleosol is either not continuous or that it encompasses a broader age range within mis 3 than previously considered in both cases data would not allow for an unambiguous linking of this paleosol with specific gi events as previously attempted the pir irsl290 dating of the loams immediately underneath pryluky unit in the range of 120 ka to 168 ka and of the pryluky mollisol from 90 ka to 126 ka confirm the broad correspondence of this unit with mis 5 although poor dose recovery results open the possibility for further testing on the degree these ages provide overestimated results quartz data severely underestimate the pir irsl290 ages for these samples the application of pir irsl290 dating for the underlying dnieper till previously linked to the saalian glaciation resulted in natural signals at the level of laboratory saturation yielding minimum ages of c 700 ka for the same sample the natural sar osl signals for 4 11 m quartz were found significantly below laboratory saturation level resulting in finite ages of 250 270 ka interpreted here as underestimates while coarse quartz 63 90 m signals reached about 85 of the laboratory saturation level these data suggest extreme caution must be taken when dating such old samples using quartz osl results from our high resolution luminescence dating raises important implications for the chronological representativeness of stayky as a key loess site in eastern europe beyond mis 2

high resolution seismic profiling in the sea of marmara northwest turkey late quaternary sedimentation and sea level changes high resolution sparker seismic profiling was carried out in the sea of marmara northwest turkey to study the late quaternary tectonics and sedimentation of this important active basin at the western end of the north anatolian fault zone a sedimentary unit interpreted as the clinoforms of a prograding delta was observed in places along the outer part of the southern shelf the topset foreset transitions of the latest clinoforms cluster around 100 m below present sea level they were probably deposited during the last glacial maximum and early phase of deglaciation between 25 and 13 k y b p when the level of the aegean was below that of the dardanelles sill 60 70 m below sea level at present therefore the sea of marmara was isolated from the aegean during the last glacial maximum but it is possible that a fluvial overflow existed across the dardanelles during this time stabilizing the level of the marmara lake and allowing the delta progradation rivers that drain into the sea of marmara from the south have a much greater combined drainage basin area and sediment flux than those draining the region to the north this may explain the much broader shelf to the south half graben bounded by north dipping normal faults observed within the southern shelf would tend to trap sediment sourced from the south and subdue any sea bed morphology on the shelf

origin of annual laminations in tufa deposits southwest japan abstract laminated tufas and a tufa depositing stream in sw japan shirokawa ehime prefecture were studied monthly over a 3 yr period a series of samples from the tufa clearly reveals the pattern of annual laminations the annual layering pattern was primarily controlled by changes in the rate of calcite precipitation as calculated from water chemistry the concentration of dissolved caco 3 which correlates with the precipitation rate was high in summer autumn and low in winter spring owing to changes in the partial pressure of co 2 in underground air regular seasonal changes in underground pco 2 probably resulted from two temperature dependent processes the diffusion of soil co 2 and the ventilation of underground air these changes in addition to water temperature changes altered the precipitation rate which has a clear seasonal pattern especially in the lower stream the seasonal precipitation rate was high in summer autumn and low in winter spring which is consistent with the seasonal lamination pattern seen in the tufas the textures of collected samples show that the laminations consist of densely calcified summer autumn june october laminae and lightly calcified winter spring november may laminae we infer that the increased precipitation rate stimulated thick calcite encrustation on cyanobacterial filaments to produce the dense textures this interpretation is supported by the lowered organic inorganic carbon production ratio in summer autumn seasonal variations in cyanobacterial assemblages are present but do not reflect the seasonal lamination pattern because the relevant processes are temperature dependent the seasonal lamination pattern at shirokawa is thought to generally apply to other laminated tufas deposited in temperate climates however a reversed pattern can result from local and climatic circumstances dense laminae were deposited in winter near the source of the spring at shirokawa because calcite precipitation was high owing to low underground pco 2 in winter reversed patterns reported from northwestern europe were probably influenced by seasonal rainfall which is reflected in hydrological conditions

dynamics of the last four glacial terminations recorded in lake van turkey abstract a well dated suite of lake van climate proxy data covering the last 360 ka documents environmental changes over 4 glacial interglacial cycles in eastern anatolia turkey the picture of cold and dry glacials and warm and wet interglacials emerging from pollen organic carbon authigenic carbonate content elemental profiling by xrf and lithological analyses is inconsistent with classical interpretation of oxygen isotopic composition of carbonates pointing to a more complex pattern in lake van region detailed analysis of glacial terminations allows for the constraining of a depositional model explaining different patterns observed in all the proxies we hypothesize that variations in relative contribution of rainfall snowmelt and glacier meltwater recharging the basin have a very important role for all sedimentary processes in lake van lake level of glacial lake van predominantly fed by snowmelt was low the water column was oxic and carbonates precipitating in the epilimnion recorded the light isotopic signature of inflow during terminations increasing rainfall and significant supply of mountain glaciers meltwater contributed to lake level rise increased rainfall enhanced density gradients in the water column and hindered mixing leading to development of bottom water anoxia carbonates precipitating during terminations show large fluctuations in their isotopic composition full interglacial conditions in lake van are characterized by high or slowly falling lake level rainfall and snowmelt feed the lake but due to re established mixing the isotopic composition of authigenic carbonates is heavier and closer to that of evaporation influenced lake water than that of runoff representing snowmelt and atmospheric precipitation

postglacial connection of the black sea to the mediterranean and its relation to the timing of sapropel formation the opening of the connection between the mediterranean and black seas as sea level rose above the bosporus sill has long been associated with the formation of the most recent holocene sapropel deposit s1 in the eastern mediterranean but the mechanism has remained elusive we present a model for the opening of the black sea based on hydraulics arguments which demonstrates that increased freshwater flux out of the black sea began 500 1000 years after sea level reached sill depth and that the timescale for the increased freshwater flux that drained the freshwater reservoir of the black sea is about 2500 3500 years we argue that the increased freshwater discharge out of the black sea would lead to decreased deep water formation and higher productivity in the surface waters in the eastern mediterranean two conditions generally associated with sapropel formation the delay in increased freshwater flux after the opening of the black sea and the period of increased freshwater discharge appear to match the onset and duration of sapropel deposits in the eastern mediterranean

black sea impact on the formation of eastern mediterranean sapropel s1 evidence from the marmara sea abstract water exchange between the black sea and the mediterranean sea has been a major focus of the paleohydrography of the eastern mediterranean glacial melt water released from the black sea is a potential factor in the formation of sapropel s1 an organic rich sediment layer that accumulated during the early holocene a high resolution study done on sediments from the marmara sea the gateway between the mediterranean and the black sea sheds light on the holocene exchange processes past sea surface temperature and sea surface salinity sss were derived from stable oxygen isotope ratios 18o of foraminiferal calcite and alkenone unsaturation ratios uk 37 heavy 18o values and high sss in the marmara sea suggest absence of low salinity water from the black sea during s1 the comparison with data from the levantine basin and southern aegean sea outlines gradients of freshening in the eastern mediterranean sea whereby the major sources of freshwater were closer to the levantine basin it is thus concluded that the black sea was not a major freshwater source contributing to formation of s1 given the absence of a low salinity layer the deposition of organic rich sediments corresponding to s1 in the marmara sea is likely the result of the global transgression and the concomitant re organization of biogeochemical cycles leading to enhanced productivity as shown by globigerina bulloides

an unusual modern silica carbonate sinter from pavlova spring ngatamariki new zealand a silica carbonate deposit is forming from the dilute alkali chloride waters of pavlova spring a small thermal pool and outflow channel 85 to 10 times lower accumulation rates than typical siliceous sinters in the tvz and deposition of both silica and calcite is controlled by microchemical conditions and local temperature gradients rather than by bulk spring water chemistry

danube river sediment input and its interaction with the north western black sea abstract the influence of the river danube is determinant to the sedimentation of the north western and western black sea area after 1970 following the building of the iron gates dam the danube river sediment discharge diminished to 30 40 of its previous value after a 12 000 year evolution marked by active progradation the danube delta has become mainly inactive over the last few decades partly due to interventions of man made origin the deficit of sediment influx has led to the intense erosional processes of the deltaic littoral on the black sea north western shelf two main areas with contrasting sedimentary processes have been identified the internal danube sediment fed shelf and the external sediment starved shelf the modern highstand sedimentary history of the north western black sea deep area is marked by the cessation of the danube deep sea fan active development the main depositional units within the north western black sea are described

a simple three dimensional model of diffusion with precipitation applied to localised pyrite formation in framboids fossils and detrital iron minerals a three dimensional diffusion with precipitation model is constructed to estimate radial variations in the amounts of pyrite which precipitate where a spherical mass of organic matter producing h2s by sulphate reduction is enveloped in a dissolved iron bearing porewater the model indicates that higher rates of sulphate reduction more readily metabolisable organic matter and larger organic masses require increasingly high dissolved iron concentrations in order to confine pyrite or iron sulphide precipitation to the decay site the maximum size sphere of exceedingly metabolisable organic matter equivalent to fresh planktonic material which can be pyritised is about 50 m radius where decay occurs in porewaters with typical dissolved iron levels this radius is close to the maximum radius of framboidal pyrite the formation of which could involve model type processes fossil carcases although mainly composed of less readily metabolisable organic matter may be orders of magnitude larger and the model demonstrates that their pyritisation requires unusually high porewater dissolved iron concentrations these inferred chemical conditions are consistent with sedimentological observations of pyritisation in beecher s trilobite bed new york state at greater depths within the sediment pyritisation is controlled by the kinetics of iron mineral reactivity towards h2s sediments vary widely in their exposure times to h2s which can range at least from 50 to 106 years at low exposure times only iron oxides are pyritised whereas at high exposure times even the most refractory iron silicates can become pyritised

genesis of large siliceous stromatolites at frying pan lake waimangu geothermal field north island new zealand lilypad stromatolites up to 3 m long and 1ae5 m wide were found to be actively growing in the shallow marginal waters of frying pan lake and its outflow channel these stromatolites composed of phormidium 90 fischerella and a variety of other microbes develop through a series of distinct growth stages dark green microbial mats cover the floor of the outflow channel and give rise to columns of various sizes and shapes in the shallower marginal waters once the columns reach the water level the mats spread laterally to form a lilypad stromatolite the lilypads are characterized by a raised dark green rim 4 5 mm high that encircles a flat interior covered with a distinctive orange red mat the microbes forming the columns and lilypad plate are being actively silicified the stromatolites are formed of i flat lying phormidium filaments p laminae ii upright filaments of phormidium that are commonly associated with fischerella u laminae and iii mucus diatoms and pyrite framboids m laminae p laminae dominate most of the columns with tripartite cycles of p u to m laminae being found mostly in the upper parts of the stromatolites the transition from the p to u laminae is marked by a change in the growth pattern of the phormidium and branching of fischerella which was probably triggered by a change in environmental conditions in the frying pan lake outflow channel this change may be related to fluctuations in water level and flow rates that are caused by periods of heavy rain seasonal changes long term variations in rainfall and or the unique 40 day hydrological cycle that exists between frying pan lake and inferno crater which is a nearby hydrothermal crater lake

hydraulic calculations of postglacial connections between the mediterranean and the black sea a series of simple hydraulic calculations has been performed to examine some of the questions associated with the reconnection of the black sea to the mediterranean through the turkish strait system during the holocene ryan et al s catastrophic flood scenario whereby the erosive power of the marine in fluxes initiated after eustatic sea level reached the sill depth opened up the bosphorus allowing saline water to pour into the black sea and filling it on a short time scale is examined the calculations show that although it might be possible to fill the palaeo black sea within the order of a decade a 1 2 year filling time scale is not physically possible a hydraulic model is also used to examine the more traditional connection hypothesis of near continuous freshwater outflow from the black sea with a slowly increasing saline inflow from the mediterranean beginning around 8 9 kyr bp the model considers two forms for the structure of the bosphorus a shallow sill as seen today and a deep sill associated with no sediments filling the 100 m gorge above the bedrock in the strait sensitivity experiments with the hydraulic model show what possible strait geometric configurations may lead to the black sea reaching its present day salinity of 18 psu salinity transients within the black sea are shown as a function of time providing for values that can be validated against estimates from cores to consider a deep non sediment filled bosphorus 100 m deep the entry of mediterranean water into the sea of marmara after 12 0 kyr bp is examined a rapid entry of marine water into the sea of marmara is only consistent with small freshwater fluxes flowing through the turkish strait system smaller than those of the present day by a factor of at least 4 such a small freshwater flux would lead to the salinification of the black sea being complete by an early date of 10 2 9 6 kyr bp thus the possibility of a deep bosphorus sill should be discounted

the geological history of geysir iceland a tephrochronological approach to the dating of sinter the vertical succession through the discharge apron of geysir up to 3 5 m thick is formed of five lithological units a e units a b c and e are formed of siliceous sinters whereas unit d is a brown ash bed tephra grains in units c d and e came from katla hekla and vei ivotn katla tephra in unit d has been largely altered to palagonite integration of tephrochronological ages historical records and geological and geomorphological relationships shows that the geysir succession developed in four main phases during phase i c 10 000 4000 years ago laminated sinters formed from hot spring waters phase ii initiated c 3300 years ago saw the termination of sinter formation and blanketing of the area with tephra from katla and hekla phase iii c 3000 900 years ago represented by the boundary between units d and e was characterized by weathering and little sinter deposition phase iv was initiated with the re birth of geysir 800 900 years ago sinter deposited from the discharged waters has however been largely confined to the southern part of the discharge apron only limited opal a precipitation has occurred since 1916 because of a decline in geysir9s eruptions

the effect of subaerial exposure on the morphology and microstructure of stromatolites in the cretaceous sinyangdong formation gyeongsang supergroup korea1 stromatolite morphology is usually controlled by a number of biological and environmental factors in the south eastern part of the korean peninsula three stromatolite units of the cretaceous sinyangdong formation have been studied with regard to the effect of diagenesis on their morphology here it is proposed that subaerial exposure and meteoric diagenesis are the most significant factors in shaping the stromatolites of the cretaceous sinyangdong formation most previous palaeontological and sedimentological studies on stromatolites have concentrated on the environmental and biogenic controls on stromatolite morphology these include extrinsic factors such as sedimentation rates or current velocities the main controlling factor on the morphology of the stromatolites in the sinyangdong formation is apparently transient subaerial exposure and related meteoric diagenesis textural examination of stromatolite samples from three stratigraphic horizons shows a characteristic repetitive pattern of cycles with gradual transition from fibrous calcite to micrite layers reflecting changes in the hydrological cycle of the lake in which the stromatolites grew stromatolite growth was terminated by corroded surfaces indicative of subaerial exposure related to a fall in lake level the growth pattern of the stromatolites was mostly determined by the morphology of the corroded substrates during subaerial exposure furthermore the internal stromatolite structure was strongly modified by the process of leaching as a result growth forms mostly changed from stratiform to columnar mesostructure this study strongly implies that diagenesis could make a very significant influence on the morphogenesis of lacustrine stromatolites in the geological past

constraints on black sea outflow to the sea of marmara during the last glacial interglacial transition new cores from the upper continental slope off romania in the western black sea provide a continuous high resolution record of sedimentation rates clay mineralogy calcium carbonate content and stable isotopes of oxygen and carbon over the last 20 000 yr in the western black sea these records all indicate major changes occurring at 15 000 12 800 8400 and 7100 yr before present these results are interpreted to reflect an evolving balance between water supplied by melting glacial ice and other river runoff and water removed by evaporation and outflow the marked retreat of the fennoscandian and alpine ice between 15 000 and 14 000 yr is recorded by an increase in clays indicative of northern provenance in black sea sediments a short return toward glacial values in all the measured series occurs during the younger dryas cold period the timing of the first marine inflow to the black sea is dependent on the sill depths of the bosporus and dardanelles channels the depth of the latter is known to be 80 5 m which is consistent with first evidence of marine inundation in the sea of marmara around 12 000 yr the bedrock gorge of the bosporus reaches depths in excess of 100 m relative to present sea level though it is now filled with sediments to depths as shallow as 32 m two scenarios are developed for the connection of the black sea with the sea of marmara one is based on a deep bosporus sill depth effectively equivalent to the dardanelles and the other is based on a shallow bosporus sill less than 35 m in the deep sill scenario the black sea s surface rises in tandem with the sea of marmara once the latter connected with the aegean sea and black sea outflow remains continuous with inflowing marine water gradually displacing the freshwater in the deep basin the increase in the 18 o of mollusk shells at 12 800 yr and the simultaneous appearance of inorganic calcite with low 18 o is compatible with such an early marine water influx causing periodic weak stratification of the water column in the shallow sill scenario the black sea level is decoupled from world sea level and experiences rise and fall depending on the regional water budget until water from the rising sea of marmara breaches the shallow sill in this case the oxygen isotope trend and the inorganic calcite precipitation is caused by increased evaporation in the basin and the other changes in sediment properties reflect climate driven river runoff variations within the black sea watershed the presence of saline ponds on the black sea shelf circa 9600 yr support such evaporative drawdown but a sensitive geochemical indicator of marine water one that is not subject to temperature salinity or biological fractionation is required to resolve whether the sill was deep or shallow

grain scale iron isotopic distribution of pyrite from precambrian shallow marine carbonate revealed by a femtosecond laser ablation multicollector icp ms technique possible proxy for the redox state of ancient seawater abstract the redox state of precambrian shallow seas has been linked with material cycle and evolution of the photosynthesis based ecosystem iron is a redox sensitive element and exists as a soluble fe ii species or insoluble fe iii species on earth s surface previous studies have shown that the iron isotopic ratio of marine sedimentary minerals is useful for understanding the ocean redox state although the redox state of the archean shallow sea is poorly known this is partly because the conventional bulk isotope analytical technique has often been used wherein the iron isotopic record may be dampened by the presence of isotopically different iron bearing minerals within the same sample here we report a microscale iron isotopic ratio of individual pyrite grains in shallow marine stromatolitic carbonates over geological time using a newly developed near infrared femtosecond laser ablation multicollector icp ms technique nir fs la mc icp ms we have determined that the grain scale iron isotopic distribution of pyrite from coeval samples shows a bimodal 2 7 and 2 3 ga or unimodal pattern 2 9 2 6 and 0 7 ga in particular pyrite from the 2 7 ga fortescue group shows a unique bimodal distribution with highly positive 1 0 defined as type 1 and negative 56fe values 1 8 defined as type 2 type 1 and 2 pyrites occasionally occur within different siliceous layers in the same rock specimen layer scale iron isotopic heterogeneity indicates that the iron isotopic ratios of the two types of pyrite are not homogenized by diagenesis after deposition some cubic pyrites have a core with a positive 56fe value 1 and a rim with a crustal 56fe value 0 the observed isotopic zoning suggests that the positive 56fe value is a primary signature at the time of stromatolite formation while secondary pyrite precipitated during diagenesis the positive 56fe value of type 1 and the large iron isotopic difference between type 1 and 2 2 8 suggest partial fe ii oxidation in the 2 7 ga shallow sea i e pyritization of 56fe enriched ferric oxyhydroxide type 1 and 56fe depleted fe2 aq in seawater type 2 type 2 pyrite was probably not produced by microbial iron redox cycling during diagenesis because this scenario requires a higher abundance of pyrite with 56fe of 0 than of 1 8 consequently the degree of fe ii oxidation in the 2 7 ga shallow sea can be estimated by a fe2 aq steady state model the model calculation shows that half the fe2 aq influx was oxidized in the seawater this implies that o2 produced by photosynthesis would have been completely consumed by oxidation of the fe2 aq influx grain scale iron isotopic distribution of pyrite could be a useful index for reconstructing the redox state of the archean shallow sea

exceptional silica speleothems in a volcanic cave a unique example of silicification and sub aquatic opaline stromatolite formation terceira azores this research was funded by the spanish ministry of economy and competitiveness project cgl2011 27826 co2 02

origin and significance of lamination in lower cretaceous stromatolites and proposal for a quantitative approach stromatolite lamination is typically defined as alternation of dark and light laminae study of lower cretaceous stromatolites fromthe leza fm n spain supports this statement but recognises additional complexities in lamination that have implications for interpreting accretion processes these stromatolites are partial analogues of present day coarse grained carbonate stromatolites in the bahamas and shark bay australia that mainly form by trapping and binding carbonate sand the leza examples contain both grain rich and micrite rich laminae with scarce particles suggesting that they accreted both by trapping and not trapping grains lamination in modern and ancient coarse grained stromatolites is commonly defined by thinmicritic crusts that formed during interruptions in accretion and separate contiguous grainy laminae repetitive lamination leza examples also contain these thin hiatal crusts and locally showrepetitive lamination but their conspicuous macroscopic lamination is defined by thicker alternating grain rich and micrite rich laminae alternating lamination this indicates that although hiatuses in accretion occurred change in accretion process was the main cause of macroscopic lamination these differences in accretion processes and lamination styles between leza examples and modern coarse grained stromatolites may reflect differences in their environmental settings modern examples occur in shallow marine tidal environments whereas leza fm coarse grained stromatolites developed in ideinfluencedwater bodies in coastal wetlands that experienced fluctuations inwater salinity and hydrochemistry analysis of lamina thickness in these cretaceous stromatolites and similar published examples provides a quantitative approach to the processes that underlie stromatolite lamination

taphonomy of very ancient microfossils from the 3400ma strelley pool formation and 1900ma gunflint formation new insights using a focused ion beam abstract focused ion beam fib milling permits the accurate extraction of ultrathin c 100 nm cross sectional lamellae from microfossils found in geological thin sections subsequent tem analysis of these lamellae can provide unique insights into the ultrastructure chemistry and taphonomy of precambrian microfossils at the micrometer to nanometer scale combining serial fib milling with sem imaging extends this capability to three dimensional 3d tomographic reconstruction and visualization of precambrian microfossils revealing information not available in light microscopy here we apply these techniques to two iconic silicified microfossil assemblages from the 3400 ma strelley pool formation of western australia and the 1900 ma gunflint formation of canada all the examined microfossils have carbonaceous walls surrounded by pure silica impregnation of microfossil walls by nano grains of silica is common together with variable degrees of wall displacement and replacement by silica all microfossils are rigidly preserved in 3d and show little or no folding or compression however there are also notable differences in taphonomic preservation our examples of the spheroidal gunflint microfossil huroniospora showed the highest fidelity of preservation with a continuous carbonaceous wall fossilized by spheroidal nano silica grains that resemble those found on bacterial surfaces in modern silicifying hot spring environments the nucleation of these silica nano spheres on the microfossil walls has induced an artificial saw tooth like ridged wall texture that may subsequently hinder species level identification the strelley pool microfossils in comparison show a lower fidelity of preservation with small parts of the microfossil walls completely replaced by silica plus extensive recrystallization of spheroidal silica nano grains to angular micro quartz our examples of the sheath like filamentous gunflint microfossil siphonophycus showed the lowest fidelity of preservation with many gaps in the carbonaceous walls and significant redistribution of carbon by recrystallizing silica grains a model is presented to explain these observations criteria for distinguishing highly probable microfossils from non cellular carbonaceous microstructures e g botryoids and grain coatings using fib based imaging are put forward for the first time here using examples drawn from the strelley pool formation and comparisons with younger gunflint material the combined in situ techniques of fib tem and fib sem nano tomography potentially provide a wealth of new nano scale information regarding the biogenicity antiquity and taphonomy of precambrian microfossils however the destructive nature of both techniques makes their application to unique palaeontological specimens problematical

cave minerals of the world 2nd edition by carol hill and paolo forti national speleological society huntsville al 463 p isbn number 1 879961 07 5 70 00 think about all of those spectacular displays of mineral crystals that grace the world s mineral museums a great many of the large faceted crystals grew in some sort of cavity over long periods of time such mineral crystals are discovered in vugs pockets and cavities exposed in mines and quarries the conditions under which they were found are very different from the conditions under which they grew the fluids from which they grew are long gone a challenge for mineralogists to deduce from the surviving clues of trace elements isotopes and fluid inclusions now consider a cave it also is a cavity maintaining conditions of constant temperature water vapor pressure and carbon dioxide pressure for long periods of time this is also an environment where minerals can grow but in the case of many caves human observers can watch the growth process in progress some cave minerals appear as large faceted crystals some are nondescript crusts of little beauty but fascinating mineralogy most have formed from flowing dripping and seeping water and thus take on shapes dictated by the idiosyncrasies of the moving water such mineral deposits are known as speleothems stalactites stalagmites flowstone and a host of more intricate shapes hill and forti illustrate speleothems with some spectacular color photographs the authors have solicited contributions from cave photographers all over the world and without exception the

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

testing the physical oceanographic implications of the suggested sudden black sea infill 8400 years ago 1 we apply a shock capturing numerical model based on the single layer shallow water equations to an idealized geometry of the black sea and the sea of marmara in order to test the implications of a suggested sudden black sea infill 8400 years ago the model resolves the two dimensional flow upstream and downstream of the hydraulic jump provoked by the cascade of water from the sea of marmara into the black sea which would occur during a sudden black sea infill the modeled flow downstream of the hydraulic jump in the black sea would consist of a jet that is in part constrained by bathymetric contours guided by the bosporus canyon the modeled jet reaches depths of up to 2000 m and could explain the origin of the sediment waves observed at this depth at a late stage of the infill the modeled jet is attached to the coast and might account for the course of a submerged channel at the mouth of the bosporus the preservation of continuous barrier washover lagoonal fill systems occurring on the black sea shelf is however not easily reconcilable with the large flows over the southwest black sea shelf predicted by the model intensified flow in the upstream basin sea of marmara is restricted to the immediate vicinity of the bosporus suggesting that a sudden reconnection need not have disturbed sediments in the wider sea of marmara

the behaviour of antimony released from surface geothermal features in new zealand abstract antimony rich geothermal features in the taupo volcanic zone tvz of new zealand s north island drain directly into surface aquatic environments the discharge from champagne pool a mixed alkali chloride sulfate hot spring at wai o tapu geothermal field contains up to 194 g l sb the discharge from frying pan lake a chloride sulfate hot spring at waimangu geothermal field contains up to 21 5 g l sb at champagne pool downstream concentrations of sb show distinct diurnal variations particularly in winter when concentrations in the early morning were less than half those measured mid afternoon changes in sulfide sulfate equilibria and direct stibnite oxidation may explain this phenomenon in the discharge from frying pan lake sb exhibits little diurnal variation most 80 of the dissolved sb released from champagne pool is removed from solution at alum lake an acid sulfate hot pool containing elevated levels of dissolved sulfide therefore relatively little sb is discharged into the freshwater drainage in the area however in the absence of a sulfide rich feature at waimangu most of the sb discharged from frying pan lake remains dissolved and is transported into the freshwater drainage system of lake rotomahana the contrast in sb behaviour between these two sites confirms the importance of dissolved sulfide and low

unraveling signatures of biogeochemical processes and the depositional setting in the molecular composition of pore water dom across different marine environments abstract dissolved organic matter dom in marine sediment pore waters derives largely from decomposition of particulate organic matter and its composition is influenced by various biogeochemical and oceanographic processes in yet undetermined ways here we determine the molecular inventory of pore water dom in marine sediments of contrasting depositional regimes with ultrahigh resolution mass spectrometry and complementary bulk chemical analyses in order to elucidate the factors that shape dom composition our sample sets from the mediterranean marmara and black seas covered different sediment depths ages and a range of marine environments with different i organic matter sources ii balances of organic matter production and preservation and iii geochemical conditions in sediment and water column including anoxic sulfidic and hypersaline conditions pore water dom had a higher molecular formula richness than overlying water with up to 11 295 vs 2114 different molecular formulas in the mass range of 299 600 da and covered a broader range of element ratios h c 0 35 2 19 o c 0 03 1 19 vs h c 0 56 2 13 o c 0 15 1 14 formula richness was independent of concentrations of doc and toc near surface pore water dom was more similar to water column dom than to deep pore water dom from the same core with respect to formula richness and the molecular composition suggesting exchange at the sediment water interface the dom composition in the deeper sediments was controlled by organic matter source selective decomposition of specific dom fractions and early diagenetic molecule transformations compounds in pelagic sediment pore waters were predominantly highly unsaturated and n bearing formulas whereas oxygen rich cho formulas and aromatic compounds were more abundant in pore water dom from terrigenous sediments the increase of s bearing molecular formulas in the water column and pore waters of the black sea and the mediterranean discovery basin was consistent with elevated hs concentrations reflecting the incorporation of sulfur into biomolecules during early diagenesis sulfurization resulted in an increased average molecular mass of dom and higher formula richness up to 5899 formulas per sample in sediments from the methanogenic zone in the black sea the dom pool was distinctly more reduced than overlying sediments from the sulfate reducing zone bottom and pore water dom from the discovery basin contained the highest abundances of aliphatic compounds in the entire dataset a large fraction of abundant n bearing formulas possibly represented peptide and nucleotide formulas suggesting preservation of these molecules in the life inhibiting environment of the discovery basin our unique data set provides the basis for a comprehensive understanding of the molecular signatures in pore water dom and the turnover of sedimentary organic matter in marine sediments

oceanography of the black sea a review of some recent results abstract a new synthesis of the black sea oceanography is presented primarily based on studies carried out in the southern black sea as well as on some recent work covering the entire basin obtained in a new era of increasing cooperation between the riparian countries a review of the physical environment is given seasonal and interannual climatic variability of the system are discussed in relation to its hydrology water mass variability and formation are studied with emphasis on the inflow of mediterranean waters pycnocline variability shelf and internal mixing and double diffusive convection the general circulation of the basin and the roles of stratification topography and coastline variations in determining the behaviour of the rapid unstable boundary currents and upwelling along the coast are discussed based on hydrographic data and satellite observations impacts of the physical processes on the ecosystem are discussed

anatomy of siliceous hot springs examples from yellowstone national park wyoming usa abstract numerous siliceous hot spring systems in the norris and lower geyser basins of yellowstone national park wyoming provide insights into spring geometries depositional facies and lithofacies associated with modern hot springs analyses of active cistern spring octopus spring deerbone spring and spindle geyser and inactive pork chop geyser siliceous hot springs have facilitated the construction of a facies model for siliceous hot spring deposits at yellowstone yellowstone s siliceous springs tend to group into four broad morphological categories siliceous spires and cones domal mounds terraced mounds and ponds siliceous spires cones are subconical accumulations up to 5 7 m high and about 2 m in diameter and are common deposits in yellowstone lake domal mounds are characterized by siliceous precipitates with a broad lens or shield geometry 2 3 m in vertical relief discharge channels and an areal accumulation of approximately 150 m2 in contrast terraced mounds have a stair step morphology a substantial pool 8 10 m in diameter shrubby precipitates and occupy areas of 2000 m2 siliceous ponds are variable in size have little outflow and exhibit low amounts of silica precipitation of these morphological varieties domal mounds and terraced mounds are thought to have the best long term preservation potential the four spring morphotypes are composed of up to eight cumulative hot spring depositional facies 1 vent 95 c 2 proximal vent precipitation of siliceous sinter is the result of abiotic and biotic processes abiotic precipitational processes are dominant in the vent area whereas biotic influences on the precipitate fabric become progressively more important downflow

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

evolution of the danube deep sea fan since the last glacial maximum new insights into black sea water level fluctuations abstract the danube deep sea fan nw black sea is one of the most developed deep sea sediment depositional systems in europe although the morphology and the architecture have been widely described in the past years little is known about the stratigraphy of this depositional system for the late quaternary this results from the lack of significant stratigraphic markers the scarcity of radiocarbon ages and the difficulty in constraining reservoir ages recent robust quantification of reservoir ages has allowed the construction of a new stratigraphic framework for the black sea from the end of the last glacial period to the holocene thus giving the opportunity to correlate sedimentological and geochemical features previously described on the nw black sea margin with climatic events identified in the northern hemisphere based on this approach we propose an improved chrono lithostratigraphic framework for the danube deep sea fan channel levees since the last glacial maximum we show that the danube deep sea fan was active during the last glacial maximum until the younger dryas early holocene transition ca 11 700 cal a bp when the turbidite activity abruptly terminated in the whole system throughout this period the danube river was the main source of the deep depositional system except between ca 17 200 cal a bp and 15 700 300 cal a bp at that time the deposition of red turbidites in the deep basin concomitant with the deposition of the so called red layers onto the continental shelf and the upper slope emphasises the direct impact of the increased meltwater runoff of the dnieper river as far as the danube deep sea fan some significant changes in the location of the depocentre of the danube deep sea fan occurred through time the main change in depocentre location occurred at ca 28 000 cal a bp with the northward avulsion leading to the formation of the middle channel although the middle and northern channel became the preferential turbidite depocentres after this event the deposition of turbidites has persisted in the southern channel levee until 14 700 cal a bp indicating that the southern channel was definitely not abandoned after the upstream northward avulsion unsurprisingly water level fluctuations and river sediment flux acted as the main forcings on the evolution of the danube deep sea fan based on these results and on the morphology of the danube canyon we propose that i lowstand conditions 110 m prevailed during the last glacial maximum and possibly between 15 700 300 cal a bp and 14 700 cal a bp ii water level ranged from 110 and 70 m between 14 700 and 11 700 cal a bp and iii water level ranged from 70 and 30 m from 11 700 cal a bp and until the reconnection of the black sea lake with the global ocean at ca 9000 cal a bp

automated measurement of eroding streambank volume from high resolution aerial imagery and terrain analysis abstract excessive sediment is an important form of surface water impairment throughout the continental united states numerous studies have investigated the role of upland soil erosion as a source of sediment and phosphorus but contributions of streambank erosion are still poorly understood current methods such as delineation and automated channel planform morphometric models are either too time intensive or do not provide adequate spatial resolution to measure smaller rivers over large scales to estimate sediment contributions from river migration on large scales we have created the aerial imagery migration model aimm a python and arcpy based automated channel migration model designed to estimate volumes of erosion and deposition related to channel migration aimm utilizes the normalized difference water index ndwi to derive binary representations of river channels from aerial photography the location of the channel is then compared between two time periods to identify zones of erosion and deposition and the volume loss related to channel migration is then calculated using a lidar derived dem when compared to three delineations and the rivmap model in the south fork iowa river watershed aimm was found to have a 98 agreement with rivmap 79 agreement with delineations and predicted net sediment flux that was within one standard deviation of the mean prediction from the delineation analysis where public imagery is available aimm can be widely applied to estimate volumes of sediment loss in a time and cost efficient procedure in particular the use of aimm within the project planning phase of conservation efforts could help focus resources in areas where they can have the most impact

coherent patterns of ice rafted debris deposits in the nordic regions during the last glacial 10 60 ka we have synchronized records of ice rafted rock debris deposits of three sediment cores from the norwegian sea and the irminger basin during the last glacial period from 10 to 50 ka by combining the use of radiocarbon dates and adjustments of physical properties our synchronized records indicate that layers rich in ice rafted debris were deposited throughout the nordic regions at times near to synchronous with the major collapses of the laurentide ice sheet during the heinrich events there are also millennial scale coherent and near to synchronous deposits of ice rafted rock debris into the norwegian sea related to repetitive changes of the flux of icebergs from the fenno scandinavian the correlation with the cold phases of the dansgaard oeschger temperature record points to a close coupling between atmospheric temperature oscillations and variations of iceberg fluxes into the norwegian sea during the last glacial variations in atmospheric circulation patterns bringing moisture supply to high latitudes and the distribution of this moisture over the different northern hemisphere coastal ice sheets and ice shelves could be controlling both the timing of ice sheet advances and the flux of iceberg to the open ocean

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

hydrology in the sea of marmara during the last 23 ka implications for timing of black sea connections and sapropel deposition 1 sediments deposited under lacustrine and marine conditions in the sea of marmara hold a late quaternary record for water exchange between the black sea and the mediterranean sea here we report a multiproxy data set based on oxygen and strontium isotope results obtained from carbonate shells major and trace elements and specific organic biomarker measurements as well as a micropaleontological study from a 14c dated sediment core retrieved from the sea of marmara pronounced changes occurred in 18o and 87sr 86sr values at the fresh and marine water transition providing additional information in relation to micropaleontological data organic biomarker concentrations documented the marine origin of the sapropelic layer while changes in n alkane concentrations clearly indicated an enhanced contribution for organic matter of terrestrial origin before and after the event when compared with the black sea record the results suggest that the black sea was outflowing to the sea of marmara from the last glacial maximum until the warmer bolling allerod the first marine incursion in the sea of marmara occurred at 14 7 cal ka b p however salinification of the basin was gradual indicating that black sea freshwaters were still contributing to the marmara seawater budget after the younger dryas which is associated with a high input of organic matter of terrestrial origin both basins were disconnected resulting in a salinity increase in the sea of marmara the deposition of organic rich sapropel that followed was mainly related to enhanced primary productivity characterized by a reorganization of the phytoplankton population

jurassic hot spring deposits of the deseado massif patagonia argentina characteristics and controls on regional distribution abstract the deseado massif santa cruz province argentinean patagonia hosts numerous middle to late jurassic age geothermal and epithermal features represented by siliceous and calcareous chemical precipitates from hot springs sinters and travertines respectively hydrothermal breccias quartz veins and widespread hydrothermal silicification they indicate pauses in explosive volcanic activity marking the final stages in the evolution of an extensive jurassic ca 178 151 ma volcanic complex set in a diffuse extensional back arc setting heralding the opening of the atlantic ocean published paleo hot spring sites for the deseado massif plus additional sites identified during our recent field studies reveal a total of 23 locations five of which were studied in detail to determine their geologic and facies associations they show structural lithologic textural and biotic similarities with miocene to recent hot spring systems from the taupo and coromandel volcanic zones new zealand as well as with modern examples from yellowstone national park u s a these comparisons aid in the definition of facies assemblages for deseado massif deposits proximal middle apron and distal siliceous sinter and travertine terraces and mounds with preservation of many types of stromatolitic fabrics that likely were controlled by formation temperature ph hydrodynamics and fluid compositions locally the mapped hot spring deposits largely occur in association with reworked volcaniclastic lacustrine and or fluvial sediments silicic to intermediate lava domes and hydrothermal mineralization all of which are related to local and regional structural lineaments moreover the numerous geothermal and significant epithermal those with published minable resources deposits of the deseado massif geological province mostly occur in four regional nnw and wnw hydrothermal structural belts northwestern northern central and southern defined here by alignment of five or more hot spring deposits and confirmed as structurally controlled by aeromagnetic data the northern and northwestern belts in particular concentrate most of the geothermal and epithermal occurrences hence jurassic hydrothermal fluid flow was strongly influenced by the most dominant and long active geological boundaries in the region the outer limits of the deseado massif horst itself

mass occurrence of oncoids at the cambrian series 2 series 3 transition implications for microbial resurgence following an early cambrian extinction abstract the traditional lower middle cambrian transition cambrian series 2 series 3 transition is marked by the first major biotic extinction of the phanerozoic eon this biotic crisis has been arguably linked to changes in ocean chemistry and or marine environments but their casual relationships remain controversial to better understand the microbial responses to paleoceanographic changes across this critical transition we have studied the environmental conditions for mass occurrence of oncoids in the western north china platform oncoids at the lower middle cambrian transition form 1 to 3 m thick massive beds show spherical subspherical morphology and contain 8 14 light dark cortical laminar couplets the light laminae are thicker and contain densely intertwined filamentous cyanobacteria that have calcified sheaths and a prostrate growth pattern the dark laminae are thinner and rich in organic matter relics pyrite framboids and heterotrophic bacteria in most oncoids cortical laminae show the same growth orientation for more than five light dark laminar couplets suggesting much less frequent grain overturning than generally thought both light and dark laminae contain well preserved organomineralization fabrics textures including extracellular polymeric substances epss nanoglobules polyhedrons and micropeloids suggesting oncoid formation in shallow marine environments with high alkalinity and active sulfate reduction the presence of pyrite framboids and heterotrophic bacterial relics implies anoxic dysoxic bottom water conditions stratigraphic correlation indicates that time equivalent oncolites and other microbialites are widespread not only in north china but also in other early cambrian successions globally the mass occurrence of oncoids coincides with the kalkarindji large igneous province of australia a prominent negative 13 c excursion roece or redlichiid olenellid extinction carbon isotope excursion a significant increase in 87 sr 86 sr and a large positive shift in 34 s the coincidence of these events suggests that the early cambrian biotic crisis may have been caused by an ocean anoxic event resulting from enhanced volcanic release of co 2 global warming and increased continental weathering preservation of massive oncolites is likely related to decreased metazoan grazing following an early cambrian biotic crisis during which archaeocyathids and many early cambrian trilobite taxa went to extinction the oncoid mass occurrence provides evidence for the resurgence of microbial life in anoxic dysoxic marine shelf environments concomitant with the early cambrian extinction event

pycnocline and deep mixing in the black sea stable isotope and transient tracer measurements abstract the peculiar mixing processes at the pycnocline and deep regions of the black sea are reviewed in addition to the wind stirring and convective mixing active in the upper pycnocline the other important mechanism that results in limited ventilation of the anoxic waters of the black sea is the mediterranean dense water inflow from the bosphorus modified by the entrainment of surface and intermediate waters introduced into the interior through double diffusive intrusions this inflow aided by the surface ekman flux divergence boundary processes and internal wave breaking is the main mechanism for the mixing and renewal of the sub pycnocline waters in the black sea interior a review of these mixing processes is complemented by results from isotope measurements with improved accuracy and reduced noise compared to earlier experiments measurements of the stable isotopes oxygen 18 18 o and deuterium 2 h confirm the origin of the water masses in the black sea and in the turkish straits including the sea of marmara to be a continuous mixture with variable fractions of salty mediterranean waters with inflowing fresh waters tritium 3 h measurements confirm very little penetration of the transient signal to the sub pycnocline and deep waters of the black sea in comparison to the better ventilated mediterranean waters filling the lower layer of the marmara sea the comparison of stable and transient tracer isotopes shows the effects of fresh waters originating from the north western shelf and the difference between the renewal mechanisms of the marmara and black seas as well as those between the upper and lower pycnocline of the black sea

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

travertines depositional morphology and the bacterially constructed constituents abstract investigation of travertine accumulations throughout central italy and the west central u s has shown that the carbonate is precipitated in response to both inorganic and organic processes individual deposits range up to 85 m thick and hundreds of square kilometers in areal extent all of the carbonate is low magnesian calcite water chemistry temperature and morphology of the accumulation greatly influence the constituents comprising these deposits harsh environmental situations favor inorganic deposits while increasingly more moderate conditions result in the formation of a greater abundance of organically precipitated material morphological variations of travertine deposits recognized include 1 waterfall or cascade 2 lake fill 3 sloping mound fan or cone 4 terraced ound and 5 fissure ridge gross morphology internal stratification and constituents comprising these deposits vary systematically depending upon the type of accumulation and chemistry of the waters bacterially precipitated calcite forms a large percentage of the carbonate in many travertine accumulations exceeding 90 of the framework grains comprising some of the lake fill deposits bacteria are among the first taxa to inhabit and reproduce in harsh spring environments and produce a variety of fascinating constituents the bacteria are primarily rods generally 0 2 m in diameter and less than 1 0 m in length the rods readily decay resulting in calcite crystals loaded with micropores the basic building block of bacterially constructed travertine is a clump of bacteria averaging 20 m in diameter enclosed in a single crystal of calcite aggregates of these crystals produce a variety of deposits including 1 crudely laminated carbonate mud 2 finely laminat d layers of mud 3 intraclasts 4 foam rock and 5 shrubs the shrubs are most striking commonly forming layers 1 3 cm thick but also producing bacterial pisoids at some locales bacterial stromatolites composed of layers of shrubs alternating with finely laminated layers of bacterial mud comprise essentially the entire deposit the shrub layers are the result of flourishing summer growth of bacteria and furthermore show remarkable daily laminae 0 1 0 5 mm thick the importance of bacteria in the formation of travertine and their universally recognized abundance in modern sediments provides an impetus for a reexamination of the role of bacteria in the origin of other types of ancient deposits

actively growing siliceous oncoids in the waiotapu geothermal area north island new zealand oncoids that are actively growing in some of the shallow water pools around champagne pool waiotapu new zealand are formed of amorphous silica opal a with minor amounts of native sulphur the growth of these oncoids is being mediated by a high diversity microbial biota that achieves optimal growth in waters that have a temperature of 35 42 c and ph of 6 6 6 9 although this biota is dominated by coccoid bacilliform and filamentous cyanobacteria sulphur oxidizing bacteria are common in the cortical laminae of some oncoids in addition diatoms and silicified pollen grains are present in some cortical laminae the silicified microbes are superbly preserved with their three dimensional form and some of their internal structures being apparent including the sites of sulphur globules in the sulphur oxidizing bacteria the microbes probably acted as templates for silica precipitation and thereby mediated the growth of the oncoids some cortical laminae are formed entirely of silicified pollen grains that came from the pinus radiata that grow in the exotic pine plantations around champagne pool by using these laminae as a record of the annual pollination event typically in september november it can be shown that many of the oncoids are

catastrophic flooding of the black sea abstract decades of seabed mapping reflection profiling and seabed sampling reveal that throughout the past two million years the black sea was predominantly a freshwater lake interrupted only briefly by saltwater invasions coincident with global sea level highstand when the exterior ocean lay below the relatively shallow sill of the bosporus outlet the black sea operated in two modes as in the neighboring caspian sea a cold climate mode corresponded with an expanded lake and a warm climate mode with a shrunken lake thus during much of the cold glacial quaternary the expanded black sea s lake spilled into to the marmara sea and from there to the mediterranean however in the warm climate mode after receiving a vast volume of ice sheet meltwater the shoreline of the shrinking lake contracted to the outer shelf and on a few occasions even beyond the shelf edge if the confluence of a falling interior lake and a rising global ocean persisted to the moment when the rising ocean penetrated across

pyrite and oxidized iron mineral phases formed from pyrite oxidation in salt marsh and estuarine sediments abstract we used scanning electron microscopy and energy dispersive x ray analysis to examine sediments from vegetated portions of three salt marshes the great sippewissett marsh cape cod ma sapelo island georgia and the hackensack meadowlands n j and from the sediments of an estuary newark bay n j pyrite particles were abundant in sediments from all sites both fine grained pyrite crystals and framboids were found single fine grained crystals diameter 0 2 to 2 0 micrometers predominated in all samples strong evidence for rapid formation of pyrite we also found both microcrystalline and framboidal iron oxyhydroxide phases in many of the sediment samples this is evidence of pyrite oxidation within the sediments and suggests that iron is conserved in salt marshes even as pyrite is oxidized the thermodynamic stability of iron phases in marsh sediments and recent pyrite oxidation studies in coal suggest goethite as the crystalline iron oxyhydroxide phase present in addition we sometimes found a red amorphous coating on grass roots from the great sippewissett and sapelo island marshes this coating is likely a form of hydrated iron iii oxide

cellular taphonomy of well preserved gaoyuzhuang microfossils a window into the preservation of ancient cyanobacteria abstract the 1500 ma gaoyuzhuang microfossils a representative mesoproterozoic cyanobacteria assemblage are crucial for understanding and searching for early precambrian life on earth the cellular taphonomy of fossils in this assemblage is poorly known however here we combined in situ microscopic and microanalytical techniques to study the detailed taphonomy of these microfossils light microscopy lm scanning electron microscopy sem and transmission electron microscopy tem observations show that gaoyuzhuang microfossils are mainly preserved in black chert layers and that silica particles can be found within fossilized cell walls and sheaths raman spectra show the characteristic first order bands at 1350 and 1605 cm 1 of carbonaceous material comprising microfossils indicating that they have experienced peak temperatures of 215 to 308 c raman maps show the spatial distribution of the carbonaceous matter as well as that of the silica matrix consistent with nano scale secondary ion mass spectrometry nanosims analyses variations in 13c versus 12c and 34s versus 32s within individual microfossils are likely the result of original differences in the isotopic compositions of cellular components confocal laser scanning microscopy clsm analyses provide fluorescence based 2 d and 3 d images of the cellular components of such microfossils at high spatial resolution the micro scale chemical isotopic and structural heterogeneities together with the subcellular morphological features support the preferential preservation of cyanobacterial cell walls and sheaths over cell contents in precambrian chert we proposed a potential taphonomic model perhaps responsible for the high fidelity of preservation for such microfossils permineralized in precambrian rocks the integrated approach has potential for deciphering the enigmatic nature of mesoproterozoic microorganisms preserved in stromatolitic cherts with significant implications for microbial preservation in the geological record

infrared spectroscopy of microbially induced carbonates and past life on mars abstract a number of evidences as the past presence of water a denser atmosphere and a mild climate suggest that on early mars environmental conditions should have been favourable to the emergence of life therefore if life actually developed on mars a few hundreds of million years ago or even more recently some biomarkers may still be present in several previous papers based on laboratory analysis we have investigated the modifications induced by thermal processing in the mid infrared spectra of carbonate samples in the form of fresh shells and fossils of different ages skeletal remains of already complex terrestrial life whose biotic origin is not questionable in this way we have been able to develop a spectroscopic method for discriminating biotic samples from their abiotic counterparts in this work we show that our method can be successfully applied also to microbialites i e bio induced carbonates deposits and particularly to stromatolites the laminated fabric of microbialites some of which are among the most primitive and oldest traces of biological activity on earth this result is of valuable importance since such primitive living organisms can be considered good analogues for putative martian life forms

abrupt drainage cycles of the fennoscandian ice sheet continental ice sheets are a key component of the earth s climate system but their internal dynamics need to be further studied since the last deglaciation the northern eurasian fennoscandian ice sheet fis has been connected to the black sea bs watershed making this basin a suitable location to investigate former ice sheet dynamics here from a core retrieved in the bs we combine the use of neodymium isotopes high resolution elemental analysis and biomarkers to trace changes in sediment provenance and river runoff we reveal cyclic releases of meltwater originating from lake disna a proglacial lake linked to the fis during heinrich stadial 1 regional interactions within the climate lake fis system linked to changes in the availability of subglacial water led to abrupt drainage cycles of the fis into the bs watershed this phenomenon raised the bs water level by 100 m until the sill of the bosphorus strait was reached flooding the vast northwestern bs shelf and deeply affecting the hydrology and circulation of the bs and probably of the marmara and aegean seas

microbial silica interactions in icelandic hot spring sinter possible analogues for some precambrian siliceous stromatolites silicified deposits such as sinters occur in several modern geothermal environments but the mechanisms of silicification and crucially the role of microorganisms in their construction are still largely unresolved detailed examination of siliceous sinter in particular sections of microstromatolites growing at the krisuvik hot spring iceland reveals that biomineralization contributes a major component to the overall structure with approximately half the sinter thickness attributed to silicified microorganisms almost all microorganisms observed under the scanning electron microscope sem are mineralized with epicellular silica ranging in thickness from 5 lm coatings on individual cells to regions where entire colonies are cemented together in an amorphous silica matrix tens of micrometres thick within the overall profile there appears to be two very distinct types of laminae that alternate repeatedly throughout the microstromatolite microbial layers are predominantly consisting of filamentous intact vertically aligned biomineralized cyanobacteria identified as calothrix and fischerella sp and weakly laminated silica layers which appear to be devoid of any microbial component the microbial layers commonly have a sharply defined base overlying the weakly laminated silica and a gradational upper surface merging into the weakly laminated silica these cyclic laminations are probably explained by variations in microbial activity active growth during spring summer allows the microorganisms to keep pace with silicification with the cell surfaces facilitating silicification while during their natural slow growth phase in the dark autumn winter months silicification exceeds the bacteria s ability to compensate i e grow upwards at this stage the microbial colony is probably not essential to microstromatolite formation with silicification presumably occurring abiogenically when conditions once again become favourable for growth recolonization of the solid silica surface by free living bacteria occurs cell motility is not responsible for the laminations we have also observed that microbial populations within the microstromatolite some several mm in depth appear viable i e they still have their pigmentation the trichomes are not collapsed cell walls are unbroken cytoplasm is still present and they proved culturable this suggests that the bulk of silicification occurred rapidly probably while the cells were still alive surprisingly however measurements of light transmittance through sections of the microstromatolite revealed that photosynthetically active light pal only transmitted through the uppermost 2 mm therefore the deeper microbial

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

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

allophanic and ferric root associated stalactites biomineralization induced by microbial activity galeria da queimada lava tube terceira azores this work was funded by project cgl2011 27826 co2 02 from the spanish ministry of science and innovation