ancient dna derived from alkenone biosynthesizing haptophytes and other algae in holocene sediments from the black sea 1 holocene sea surface temperatures sst of the black sea have been reconstructed using sedimentary c37 unsaturated alkenones assumed to be derived from the coccolithophorid haptophyte emiliania huxleyi whose fossil coccoliths are an important constituent of the unit i sediments however alkenones can also be biosynthesized by haptophyte species that do not produce microscopic recognizable coccoliths a species specific identification of haptophytes is important in such u37k based past sst reconstructions since different species have different alkenone sst calibrations we showed that 18s rdna of e huxleyi made up only a very small percentage less than 0 8 of the total eukaryotic 18s rdna within the up to 3600 year old fossil record obtained from the depocenter 2000 m of the black sea the predominant fossil 18s rdna was derived from dinoflagellates gymnodinium spp which are predominant members of the summer phytoplankton bloom in the modern black sea using a polymerase chain reaction denaturing gradient gel electrophoresis method selective for haptophytes we recovered substantial numbers of a preserved 458 base pair bp long 18s rdna fragment of e huxleyi from the holocene black sea sediments additional fossil haptophyte sequences were not detected indicating that the e huxleyi alkenone sst calibration can be applied for at least the last 3600 years the ancient e huxleyi dna was well protected against degradation since the dna alkenone ratio did not significantly decrease throughout the whole sediment core and 20 of 2700 year old fossil e huxleyi dna was still up to 23 000 base pairs long we showed that fossil dna offers great potential to study the holocene paleoecology and paleoenvironment of anoxic deep sea settings in unprecedented detail

tilting uplift volcanism and disintegration of the south german block abstract we present a large set of fault slip data together with six u pb ages on calcite vein fillings constraining the kinematics and timing of near surface uppermost 2 3 km of crust faulting of the uplifted south german block in the northern foreland of the nw ward advancing alps the structural data confirm earlier studies showing miocene subhorizontal ne directed extension with shortening mainly being subvertical but also subhorizontally nw oriented the u pb ages are between 15 3 0 2 and 2 3 1 1 ma 2 analytical uncertainty and date kinematically coordinated normal and strike slip faulting in the northern alpine foreland the faults in the south german block have limited strike lengths indicating that they do not cut deeply into the crust however the faults appear to control volcanic centers the melts of which originated at the base of the lithosphere we suggest that the miocene faults could tap the mantle because they reactivated formerly deep seated faults the ages for near surface faulting are coeval with eruption of the urach and hegau volcanics published data suggest that alpine shortening induced large wavelength lithospheric folding in the foreland since 18 16 ma volcanism in the south german block focussed along a lithospheric antiform which is in part superimposed on the foreland bulge of the alps we propose a close link between progressive southward tilting uplift and faulting of the south german block due to lithospheric scale folding and upward flow of the asthenosphere flexure of the lithosphere deep seated volcanism and the nw ward advancing alps

the jura mountains an active foreland fold and thrust belt abstract recently completed in situ stress measurements using the borehole slotter at 33 new test sites within the swiss and french jura mountains combined with previously published stress data allow a detailed description of the contemporary state of stress in this fold and thrust belt and the adjacent foreland five stress provinces can be recognized with two different general orientations of maximum horizontal stress sh 1 the central and southwest provinces with a nnw sse to nne ssw orientation 2 the east northwest and southeast provinces with an e w to nw se orientation stress magnitudes are in general higher in the southern than in the northern jura mountains characteristic of the northern jura is an e w trending zone of low stress magnitudes which can be traced from the bresse depression south of besancon to the eastern end of the jura northwest of zurich boundaries of stress provinces show poor agreement with boundaries of tectonic units in the jura in addition stress provinces extend beyond the boundaries of the jura mountains into their foreland furthermore palaeo stress orientations show large discrepancies with respect to the contemporary stress orientation these findings are considered to indicate a termination of jura thin skinned foreland tectonics which probably took place some time between 9 and 4 ma according to palaeontological and tectonic evidence it is suggested that a new style of tectonics has commenced in the jura mountains deforming both the basement directly below the jura fold and thrust belt and the cover rocks in a similar mode

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

relationship of the tetra unsaturated c37 alkenone to salinity and temperature implications for paleoproxy applications 1 this study assesses the relationship to salinity and temperature of the levels of the tetra unsaturated 37 carbon methyl alkenone c37 4 in the surface ocean uk 37 a measure of the relative abundances of the c37 2 and the c37 3 alkenones has a well constrained linear relationship to temperature in the open ocean prahl and wakeham 1987 and is a well established technique for estimating past sea surface temperatures in the sediments e g muller et al 1998 unlike the di and tri unsaturated c37 alkenones the temperature response of the tetra unsaturated c37 alkenone is less certain sikes et al 1997 and recent work has suggested a relationship to salinity instead rosell mele 1998 schulz et al 2000 our study examined 106 surface water and sediment trap samples from the atlantic pacific and southern oceans to assess the relationship of the relative abundance of c37 4 to temperature and salinity we also examined the relative unsaturation of c37 2 and c37 3 the parameter uk 37 to the same parameters to place the c37 4 results in context uk 37 has a strong correlation to salinity in the atlantic but the relationship does not hold worldwide whereas uk 37 shows a strong linear relationship to temperatures in all ocean basins as shown in previous calibrations the salinity response in the atlantic does not confirm cause and effect and interpretation of the broader data set suggests any correlation is an artifact of the strong correlation of salinity to temperature in this basin implying salinity has no effect on the unsaturation of the c37 2 or c37 3 alkenones the c37 4 alkenone shows no discernable relationship to temperature or salinity across the several basins even when correlations are restricted to cooler temperatures where the tetra unsaturated alkenone would be expected to be present these results indicate that c37 4 alkenone levels in the open ocean do not reflect either salinity levels or temperature but respond most strongly to some other environmental variable perhaps changes in growth rate light or nutrient supply as suggested by culture studies

a baltic ice lake transgression in the southwestern baltic evidence from fakse bugt denmark abstract marine geological investigations including shallow seismic surveys and corings have been carried out in the shallow waters of fakse bugt bay and hjelm bugt near to the island of mon denmark a combined sequence and lithostratigraphy has been established and supplemented with biostratigraphic data and 14 c datings the data show that a sequence of varved glaciolacustrine sediments mapped east of mon and in hjelm bugt can be followed into the arkona basin correlation of these glaciolacustrine deposits with baltic ice lake deposits in blekinge southern sweden indicates the existence of a major lake basin the initial baltic ice lake in sweden the initial phase of the baltic ice lake is dated to about 12 500 14 c years bp in the mon area transgression of the baltic ice lake is indicated in the central part of fakse bugt by the development of a transgressive freshwater barrier beach ridge lagoon system following the initial onlapping sedimentation of varved deposits the freshwater coastal system was initiated during the allerod stage and the final maximum transgression level 13 m below present sea level was reached in the upper part of younger dryas just prior to the final drainage of the baltic ice lake

the late variscan control on the location and asymmetry of the upper rhine graben the nne trending upper rhine graben urg of the european cenozoic rift system developed from c 47 ma onwards in response to changing lithospheric stresses in the northwestern foreland of the alps the composite graben structure consists of three segments each c 100 km long and 30 40 km wide but flares to c 60 km near its southern and to c 80 km near its northern termination normal faulting induced a total extension of 5 8 km of the 1 2 km thick mesozoic sedimentary franconian platform and underlying variscan basement rocks however distribution of an up to 3 5 km thick sedimentary graben fill and cumulative displacements near eastern and western main border fault systems suggest that subsidence of the graben floor and shoulder uplift created strong cross sectional asymmetries cumulative w down displacements 3 km along strongly segmented transfer faults in the east contrast with e down displacements 600 km long zone that delimits the trailing edge of a sw moving lithospheric block in the urg area ne sw oriented seismic anisotropy at sublithospheric depths of c 60 80 km suggest active mantle flow in this direction as a possible driving force for the reactivation of pre graben lithospheric shear zones

compaction induced stress variations with depth in an active anticline northern apennines italy 1 it is shown that the stress field can vary with depth even within a homogeneous tectonic setting as documented for the active mirandola fault related fold along the buried front of the northern apennines analyses of borehole breakouts and other well data integrated with seismological information and field evidence show that extension perpendicular to the fold axis above approximately 1200 m changes to a strike slip stress field and finally to compression near the main detachment at depth similar along depth strain variations recognized in non active anticlines are usually explained by invoking tangential longitudinal strain folding i e stretching above and shortening below a neutral surface or gravitational instabilities however in this study we propose that differential compaction may play a significant and generally overlooked role with the aid of numerical modeling it is shown that where fold limbs are onlapped by highly compactable deposits as in the mirandola area differential compaction induces stretching at shallow 1 2 km depths the amount of stretching is a function of the shape of the fold and of the thickness of the syn tectonic sediments we conclude that in the mirandola case study the stress variations observed with depth are the result of a combination of a regional compression at depth and local tension driven by differential compaction of growth strata on the limbs of the anticline with respect to its crest

neogene to ongoing normal faulting in the inner western alps a major evolution of the late alpine tectonics 1 widespread brittle extension occurs in the internal zones of the southwestern alps forming a dense fault network which overprints the compressional structures the extension has been followed by transcurrent motions in terms of paleostress this extension is radial to the belt close to the crustal penninic front and multidirectional in the eastern part of the internal zones the paleostress field of the strike slip phase is coherent with the extensional one and compatible with dextral shear along longitudinal faults globally we propose that the internal zones of the southwestern alps underwent a single neogene transtensive tectonic regime to strengthen our structural results the current tectonics has been analyzed using seismotectonic tools this approach allowed the recognition of several active faults moreover the ongoing tectonics is coherent with the observed brittle deformation the fault network controls the present day seismicity the combined seismotectonic and structural approaches give coherency and continuity from the neogene to ongoing extensional tectonics in the southwestern alps in the framework of the whole western alps a synthesis of our results with neotectonic related data allowed us to provide an accurate map of the neogene to present kinematics of the belt extension which appears as a major feature of the internal zones has been coeval with the propagation of thrusts in the outer zones during neogene times the geodynamic processes which rule this major tectonic evolution of the belt remain a matter of debate

temperature dependency of long chain alkenone distributions in recent to fossil limnic sediments and in lake waters distribution patterns of c37 and c38 polyunsaturated long chain alkenones lcas serve as proxies for the determination of paleotemperatures for marine surface waters we studied recent subrecent and late glacial holocene sediments from germany austria russia and the u s to test for a correspondence between lca distribution and surface water temperature in limnic systems previously reports of lca occurrence were restricted to sediments of 6 wide distributed freshwater and alkaline lakes in this study 13 of 27 investigated lakes contained lcas in surface sediments with concentrations varying between 12 to 205 g g toc late glacial to holocene sediment sequences from lake steisslingen and lake wummsee germany lake pichozero russia and brush lake u s a contained abundant lcas with averaged concentrations of 33 to 7536 g g toc for the first time we observed the occurrence of lcas within in the water column of oligotrophic lake stechlin ne germany alkenones were restricted to the zone of maximum chlorophyll concentration within the water column indicating that lcas have a biosynthetic origin and can be attributed to phototrophic micro algae attempts to identify the producing organism however were not successful culture experiments allow various phytoplankton to be excluded as producers alkenone producing algae are evidently of small size hindering microscopical identification lcas commonly occur in high concentrations in late glacial sediments mainly during the cold period of the younger dryas whereas the holocene usually is devoid of polyunsaturated alkenones the episodic occurrence of lcas restricts their utility as proxies for continuous geological records furthermore lack of microscopical verification and the episodic distribution allow for different producers of unsaturated alkenones in recent and late glacial sediments an empirical relationship between lca distribution and temperature was observed in fossil sediments from lake steisslingen there is a good correspondence between uk37 and the temperature controlled 18o isotope ratio of lake chalk comparison of lca patterns obtained from the uppermost centimetres of lake sediments with averaged summer surface water temperatures of the lakes studied demonstrates a trend of covariance r2 uk 37 0 90 uk37 0 67 n 9 hence the same mechanism that causes temperature dependence of lca patterns in marine systems might be effective in limnic settings identification of alkenone producers and their culture under controlled temperature are still mandatory before lcas can be routinely applied as paleotemperature proxy in limnic systems

culturing of the first 37 4 predominant lacustrine haptophyte geochemical biochemical and genetic implications long chain alkenones lcas are potential biomarkers for quantitative paleotemperature reconstructions from lacustrine environments however progress in this area has been hindered because the conditions necessary for the growth of haptophytes responsible for alkenone distributions in lake sediments the predominance of c37 4 lca are not known here we report the first enrichment culturing of a novel haptophyte phylotype hap a from lake george nd that produces predominantly c37 4 lca hap a was enriched from its resting phase collected from deep sediments rather than from water column samples in contrast enrichments from near surface water yielded a different haptophyte phylotype hap b closely related to chrysotila lamellosa and pseudoisochrysis paradoxa which does not display c37 4 lca predominance similar enrichments have been reported previously the lca profile in sediments resembles that of enrichments containing hap a suggesting that hap a is the dominant alkenone producer of the sedimentary lcas in enrichments increased lighting appeared to be crucial for triggering alkenone production both u37k and u38k indices show a promising positive relationship with temperature for hap a in enrichments but the offset from the environmental calibration suggests that other factors e g the growth stage or nutrients may influence the absolute u37k value based on 18s rrna gene analyses several lakes from the northern great plains as well as pyramid lake nv and tso ur tibetan plateau china contain the same two haptophyte phylotypes analysis of surface sediment from the great plains lakes show the hap a type lca distribution whereas pyramid and tso ur show the hap b type distribution waters of the great plain lakes are dominated by sulfate ions whereas those pyramid and tso ur are dominated by carbonate ions suggesting that the sulfate to carbonate ratio may be a determining factor for the dominance of the hap a and hap b phylotypes in natural settings

organic matter production and preservation and evolution of anoxia in the holocene black sea dating of sediments collected in gravity cores during leg 1 of the 1988 r v knorr expedition to the black sea suggests that the onset of water column anoxia at 7 5 ka was virtually synchronous across the basin over a depth range of 200 2250 m a finely laminated organic carbon oc rich sapropel unit ii was produced as a result of this anoxia the trigger for increased oc production and development of anoxia was the spillover of saline waters through the bosporus that probably began at 9 0 ka and peaked between 7 0 and 5 5 ka this spillover enhanced vertical mixing and nutrient cycling and caused a short term 2 3 kyr burst in surface water productivity during the early part of unit ii deposition continued incursion of saline waters enhanced vertical stability and inhibited mixing of nutrients into surface waters thus limiting primary production and decreasing the oc flux to sediments beginning 5 5 ka concentration accumulation rate and degree of preservation of organic matter all decreased in the upper part of unit ii as a result of decreasing productivity but anoxia persisted throughout most of the water column the end of unit ii sapropel deposition was synchronous across the black sea as the result of the first blooms of the coccolith emiliania huxleyi which presumably marked an increase in surface water salinity above 11 and the beginning of unit i deposition the high coccolith carbonate fluxes that occurred during deposition of unit i diluted the oc concentration in the sediments but oc accumulation rates are about the same as those in upper part of unit ii

darss sill as a biological border in the fossil record of the baltic sea evidence from diatoms abstract biostratigraphical and palaeoecological analyses of cores along a transect from femer belt to the arkona basin reveal that north sea waters began to enter the western baltic sea between 8600 and 8400 calibrated years bp studies of diatoms indicate that mecklenburg bay was characterised by slightly brackish water conditions between 8400 and 8000 cal years bp at around 8000 cal years bp increasing salinity is indicated by a strong dominance of the diatoms paralia sulcata and dimeregramma minor some centuries later another diatom assemblage appeared and became dominant in mecklenburg bay this assemblage includes hyalinella lateripunctata and pravifusus hyalinus species typical of shallow water areas along the atlantic coast today at this time the first marine molluscs made their appearance the oldest shell of a marine mollusc found in our material is dated to 7600 cal years bp the associated assemblage that includes adult specimens of the gastropod aporrhais pespelicani indicates higher salinities than today during the littorina sea stage a marine diatom flora with p sulcata catenula adhaerens and d minor crossed the darss sill and became widely distributed in the arkona basin pomeranian bay and the baltic sea proper in contrast taxa indicative of the hyalinella lateripunctata p hyalinus assemblage are only found west of the darss sill in femer belt and mecklenburg bay apparently the darss sill threshold has been acting as an important salinity border from around 7800 cal years bp until today

controls on alkenone unsaturation ratios along the salinity gradient between the open ocean and the baltic sea abstract alkenone unsaturation ratios of sedimentary lipids are used as a geochemical proxy for sea surface temperatures and interest is growing in their potential as indicators of different water masses and possibly of salinity we analyzed the abundance of unsaturated c37 to c38 ketones in lipid extracts of 57 surface sediment 0 1 cm samples along a salinity gradient from 8 to 33 psu in the transition from the skagerrak to the baltic sea nw europe in addition to surface sediments we analyzed alkenones in suspended particulate matter at 13 stations over a gradient in salinity from 25 to 33 psu during a bloom of the coccolithophore emiliania huxleyi alkenones were detected in all samples suspended matter and sediment with variable contributions of the tetra unsaturated c37 alkenone compound c37 4 range from 2 to 10 of total c37 alkenone content comparing the alkenone unsaturation index u37k and c37 4 data to climatological sea surface temperature and sea surface salinity data sets revealed that sst estimated from u37k of saline end members samples from the skagerrak is in the general range of modern sst during bloom periods of haptophytes at salinities below 30 psu c37 4 increases to above 5 and the unsaturation ratios cease to be related to climatological annual or seasonal sea surface temperatures on the other hand the c37 4 appears to be inversely and significantly correlated to salinity highest c37 4 proportions in the inner baltic sea are caused by an unidentified organism but in the transition area at salinities down to 10 psu the producer apparently is e huxleyi the suspended matter data together with those from the water column support the hypothesis of changing biosynthesis of alkenones under salt stress by the coccolithophore e huxleyi but constrain the maximum of c37 4 attributable to salt stress to 10 of all c37 alkenones

in situ stress data from the jura mountains new results and interpretation recently completed in situ stress measurements using the borehole slotter at 33 new test sites within the swiss and french jura mountains are presented when combined with previously published stress data these new measurements allow a detailed description of the contemporary state of stress in this fold and thrust belt and the adjacent foreland the data now allow the recognition of five stress provinces within which two general and different orientations of maximum horizontal stress sh can be distinguished the central and the southwest provinces with a nnw sse to nne ssw orientation and the east northwest and southeast provinces orientated e w to nw se each province has its own characteristic orientation measurements in three study areas are presented for comparison with already published acoustic anisotropy measurements borehole breakout data overcoring tests and triangulation measurements the results show a generally good agreement with the new borehole slotter measurements the tectonic implications of these stress data are discussed in terms of a large scale stress reorientation of the nw se orientated contemporary central european stress field in the foreland of the western alpine arc

seismic reflection evidence for thick skinned tectonics in the northern jura newly released seismic reflection data from the northern jura mountains and southern rhine graben provide the first high quality subsurface images from this area these throw light on the details of the fault patterns in the area and show that the ferrette and le glaserberg jura structures are largely the result of thrust faulting however the faults differ in their nature from those usually assumed in jura tectonics they are not low angle thrusts converging on a decollement zone in triassic evaporites they appear instead to be high angle faults that cross the entire sedimentary section indicating that thick skinned tectonics prevailed in this part of the jura embryonic jura folds can be seen on the images from the nearby mulhouse horst folds that are not supported by thickened triassic evaporites the existence of recent earthquake activity taken together with the prevalence of thick skinned tectonics suggests that occasional large earthquakes cannot be ruled out in this area

combined dna and lipid analyses of sediments reveal changes in holocene haptophyte and diatom populations in an antarctic lake preserved ribosomal dna of planktonic phototrophic algae was recovered from holocene anoxic sediments of ace lake antarctica and the ancient community members were identified based on comparative sequence analysis the similar concentration profiles of dna of haptophytes and their traditional lipid biomarkers alkenones and alkenoates revealed that fossil rdna also served as quantitative biomarkers in this environment the dna data clearly revealed the presence of six novel phylotypes related to known alkenone and alkenoate biosynthesizing haptophytes with isochrysis galbana uio 102 as their closest relative the relative abundance of these phylotypes changed as the lake chemistry particularly salinity evolved over time changes in the alkenone distributions reflect these population changes rather than a physiological response to salinity by a single haptophyte using this novel paleo ecological approach of combining data from lipid biomarkers and preserved dna we showed that the post glacial development of ace lake from freshwater basin to marine inlet and the present day lacustrine saline system caused major qualitative and quantitative changes in the biodiversity of the planktonic populations over time

alkenone producers inferred from well preserved 18s rdna in greenland lake sediments 1 the 18s ribosomal dna rdna sequences of haptophyte algae were successfully amplified using the polymerase chain reaction pcr from water filtrate surface sediments and a late holocene sediment sample 1000 years old from a group of lakes in the sondre stromfjord region of west greenland the dna of the algal primary producer is extremely well preserved in the laminated lake sediments which have been deposited in cold 1 2c anoxic and sulphidic bottom water phylogenetic analyses of the greenland haptophyte rdna sequences suggest that alkenones in the greenland lake sediments are produced by haptophyte algae of the class prymnesiophyceae the 18s rdna sequences from the greenland samples cluster within a distinct phylotype differing from both marine haptophytes and from those reported previously from ace lake antarctica the similarity of haptophyte rdna sequences among all samples in this study suggests a single alkenone based temperature calibration may be applied to these lakes for at least the past 1000 years these sedimentary archives hold great promise for highresolution alkenone based paleotemperature reconstruction of southern west greenland a region sensitive to atmospheric oceanic climate phenomena such as the north atlantic oscillation nao

diagenesis in neogene coal sequence a study on soluble organic matter abstract sedimentary materials for the 2 km neogene quaternary section in the tiszapalkonya i corehole north eastern hungary pannonian basin have been used to study the processes of diagenesis the age of lignite coal and sediment samples penetrated ranged between 6 and 9 million years with a corresponding temperature increases from 18 to 105 c over the section studied the soluble organic matter from 65 coal strata was analyzed by different methods in some cases the insoluble organic matter was also characterized by rock eval and vitrinite reflectance measurements the values of bitumen corg and s1 in the top samples have obviously demonstrated that the late diagenetic processes have not taken place yet the insolubilization was observed in the case of the long chain aliphatic esters by their decreasing proportion in bitumens the variation of certain indices pr phr pr n c17 n c22 n c23 and cpi also showed a distinctive depth interval 800 1200 m for insolubilization during late diagenesis the epimerization of 16 h phyllocladane to 16 h phyllocladane has encountered below 1300 m and was still incomplete at about 1600 m depth the traces of the onset of early oil genesis was recognized at about 1500 m depth

stress field variations in the swiss alps and the northern alpine foreland derived from inversion of fault plane solutions 1 this study is devoted to a systematic analysis of the state of stress of the central european alps and northern alpine foreland in switzerland based on focal mechanisms of 138 earthquakes with magnitudes between 1 and 5 the most robust feature of the results is that the azimuth of the minimum compressive stress s3 is generally well constrained for all data subsets and always lies in the ne quadrant however within this quadrant the orientation of s3 changes systematically both along the structural strike of the alpine chain and across it the variation in stress along the mountain belt from ne to sw involves a progressive counterclockwise rotation of s3 and is most clear in the foreland where it amounts to 45 50 this pattern of rotation is compatible with the disturbance to the stress field expected from the indentation of the adriatic block into the central european plate possibly together with buoyancy forces arising from the strongly arcuate structure of the moho to the immediate west of our study area across the alps the variation in azimuth of s3 is defined by a progressive counterclockwise rotation of about 45 from the foreland in the north across the helvetic domain to the penninic nappes in the south and is accompanied by a change from a slight predominance of strike slip mechanisms in the foreland to a strong predominance of normal faulting in the high parts of the alps the observed rotation can be explained by the perturbation of the large scale regional stress by a local uniaxial deviatoric tension with a magnitude similar to that of the regional differential stress and with an orientation perpendicular to the strike of the alpine belt the tensile nature and orientation of this stress is consistent with the spreading stress expected from lateral density changes due to a crustal root beneath the alps

on the causes for salinity variations in the baltic sea during the last 8500 years 1 the baltic sea became connected to the open sea about 8500 years b p and that marked the beginning of the still continuing litorina sea stage there have since been significant long term variations of the salinity from a maximum of some 10 15 to the present of 7 8 the salinity variations have been known since the beginning of the twentieth century and various mechanisms have been proposed to explain these however so far no one has actually tried to quantify and thereby rank the relative importance of the different proposed mechanisms in this paper we used a simple oceanographic model to quantify the impact of changes in cross sectional areas of the inlets to the baltic we found that such changes cannot explain the full variation of the salinity we propose that the remaining salinity variations 0 5 5 are explained by changes in net freshwater input in the range 15 60 the calculated variations in the freshwater supply are in large coherent with known variations of the northern european climate we show that other possible factors as increased mixing frontal displacements higher deep water salinity and larger depths in kattegat and larger oscillating flows across the sills due to increased sea level variability are less likely to have made substantial contributions to the salinity variations in the baltic sea

two and three dimensional numerical simulations of the stress field at the thrust front of the northern apennines italy 1 two and three dimensional mechanical models simulating the seismic cycle along thrust faults are devoted to the active front of the northern apennines buried under the plio pleistocene sediments of the eastern po plain the models aim at understanding two peculiar characters of the stress field in the region 1 analyses of borehole breakouts and other well data integrated with seismological information and field evidence show along depth variations from extensional to strike slip to compressional for increasing depth of the stress style along the active mirandola anticline and 2 seismic and borehole breakout data suggest strong lateral rotations of the stress axes along the frontal and lateral ramp portions of the mirandola thrust fault modeling results allowed us to understand that the mechanical decoupling along faults strongly affects the stress distribution in their vicinity under the form of strong rotations of the principal stress axes as a consequence the slip either fast or slow along active blind thrust faults could drive to local stress fields very different from that associated with regional tectonics this could explain together with other processes such as differential compaction the along depth variation of the stress field observed in the mirandola region and the strong lateral rotations of the principal stress axes observed along the lateral ramp of the mirandola thrust fault finally the seismic activity along one of the thrust fault ramps along the apennines front should not interfere with the state of stress along adjacent ramps

sedimentary alkenone distributions reflect salinity changes in the baltic sea over the holocene the baltic sea has had a complex salinity history since the last deglaciation here we show how distributions of alkenones and their d values varied with past fluctuations in salinity in the baltic sea over the holocene by examining a holocene record 11 2 0 1 cal kyr bp from the arkona basin major changes in the alkenone distribution i e changes in the fractional abundance of the c37 4 me alkenone the c38 2 et alkenone and a c36 2 me alkenone the latter which has not been reported in the baltic sea previously correlated with known changes in salinity both alkenone distributions and hydrogen isotopic composition suggest a shift in haptophyte species composition from lacustrine to brackish type haptophytes around 7 7 7 2 cal kyr bp corresponding with a salinity change that occurred when the connection between the basin and the north sea was re established a similar salinity change occurred in the black sea previously published alkenone distributions and their d values from the black sea were used to reconstruct holocene changes in surface water salinity and hence it was shown that the unusual c36 2 alkenone dominates the alkenone distribution at salinities of 2 8 ppt g kg this information was used to corroborate the interpretations made about salinity changes from the data presented for the baltic sea low and variable salinity waters in the baltic sea over the holocene have led to a variable alkenone producing haptophyte community composition including low salinity adapted species hindering the use of the unsaturation ratios of long chain alkenones for sea surface temperature reconstruction however these alkenone based indices are potentially useful for studying variations in salinity regionally as well as in the past

determination of sediment provenance at drift sites using hydrogen isotopes and unsaturation ratios in alkenones the large 20 hydrogen isotopic gradient in surface waters of the northwest atlantic ocean is exploited to track changes in the source of alkenones to the bermuda rise sediment drift cultures of the predominant alkenone producing coccolithophorid e huxleyi were grown in deuterium enriched seawater and shown to possess alkenones with a d h ratio that closely tracked the water d h ratio r 2 0 999 n 5 isotopic enrichments with a fractionation factor between 0 732 and 0 775 a hydrogen isotopic depletion of 193 3 n 9 was measured in alkenones from suspended particles relative to seawater in the subpolar and subtropical northwest atlantic ocean this value was used to calculate the water d values in which alkenones from bermuda rise sediment were synthesized and by extension the water mass in which they were produced applying this technique we find that 60 to 100 of the alkenones in late holocene bermuda rise sediment were produced in deuterium depleted subpolar water to the northwest of the drift to reconcile values of the alkenone unsaturation ratio u k 37 a widely used proxy for sea surface temperature with the d values of alkenones in late holocene sediments from the bermuda rise at least three sources of sediment must be invoked a cold very isotopically depleted source almost certain to be the scotian margin a warm moderately isotopically depleted source likely to be the northwestern edge of the subtropical gyre and a cold isotopically enriched source which we hypothesize to be the subpolar waters overlying the main branch of north atlantic deep water flowing southwest from the nordic seas copyright 2005 elsevier ltd paleoclimate records with sufficient length and temporal resolution to study the occurrence and causal mechanisms of abrupt climate change are exceedingly rare rapidly deposited ocean sediments provide the best archive for studying these events through geologic time but such sites in the open ocean are limited to sediment drift deposits such as the bermuda rise in the northwest atlantic using multiple climate proxies in a single core is becoming more common in high resolution pa leoclimate investigations but a major potential concern for this approach arises from the possibility that the fine fraction of sediment e g 63 m and the climate proxies within it may represent conditions far from the deposition site here we propose and test the hypothesis that hydrogen isotope ratios of alkenones a class of lipids from phytoplankton may provide insight into the source of fine grained sediment because of their restricted sources broad geographic distri bution and excellent preservation properties alkenones are of particular interest in the emerging field of compound specific hydrogen isotopic analysis the sedimentary abundances ex tents of unsaturations and isotopic compositions of alkenones provide quantitative and near continuous records we isolated alkenones from cultured unicellular algae haptophyte emil iania huxleyi surface ocean particulate material and open ocean sediments to determine the extent and variability of hydrogen isotopic fractionation in the di tri and tetraunsat urated c37 compounds we then compared the d values of the alkenones in surface sediments between the bermuda rise and the scotian margin above which a large 20 d gradient exists we determined the fractionation between alkenones from suspended particulate samples and the water in which the phytoplanton lived and examined the variability of alkenone d values during the medieval warm period little ice age climate transition cf keigwin 1996 at the bermuda rise

salinity changes in the central baltic sea nw europe over the last 10000 years we attempt a reconstruction of salinity levels of the central baltic sea based on diatom assemblages the isotopic composition of organic matter and sedimentological expression of anoxia over the last 10 000 years we use the data to investigate the dependence of salinity levels on climate evolution and isostasy changes in salinity of surface and deep waters were most pronounced from 8400 to approximately 5000 cal bp density stratification between salty deep and fresher surface waters caused the frequent development of anoxic conditions and deposition of laminated sediments on large parts of the sea floor in the central baltic sea and dramatic changes in organic carbon accumulation rates from 5000 to 3100 cal bp the salinity of the basin decreased oxygenation of deep sea floors was improved and fertility of the sea surface was significantly reduced this is reflected by low accumulation rates of organic carbon in bioturbated sediments since 2800 cal bp salinity rose again and anoxic periods were more common even though the major steps in environmental evolution in the baltic sea coincide with known patterns of climatic change of the north atlantic realm over the last 10 000 years we find no conclusive evidence for synchronous changes or linear responses on submillennial timescales however we note that major variations in our salinity records agree with temporal patterns of reconstructed summer warmth and winter precipitation in southern scandinavia both types of record suggest that climate in the mid holocene was far from stable our data also confirm that climate evolution over the late holocene had significant impact on environmental conditions in the baltic sea

unusual distributions of long chain alkenones and tetrahymanol from the highly alkaline lake van turkey long chain c37 to c40 alkenones with di tri and tetra unsaturation are very abundant in sediment trap material and holocene to late pleistocene core samples from the earth s largest soda lake lake van turkey thus the known distribution range of these typical biomarkers for haptophyte microalgae is extended to highly alkaline environments the observed unsaturation patterns differ strikingly from those found in open marine haptophytes and sediments by an enhanced relative abundance of the tetra unsaturated compounds especially the c37 4 methyl ketone their preponderance is suggested to be a facies marker pattern for lacustrine and marginal marine areas of sedimentation using published u37k calibrations no reliable absolute temperatures were obtained for the lake van samples accordingly marine sea surface temperature determinations based on long chain alkenones should be applied with caution when a contribution of these compounds from coastal or nonmarine sources can not be excluded the presence of tetrahymanol and gammacer 3 one in the lake van materials is attributed to organic matter contributions of ciliates the relative abundance of long chain alkenones and of tetrahymanol gammacer 3 one is considered to reflect changes in the environmental conditions in particular in the hydrological setting we suggest that times of pronounced stagnation are recognised by very high tetrahymanol gammacer 3 one concentrations together with drastically increased stanol stenol ratios and intervals of enhanced convection or of high freshwater input are characterised by high alkenone contributions

interhemispheric appraisal of the value of alkenone indices as temperature and salinity proxies in high latitude locations alkenone sediment data from the nordic seas and north atlantic are compared to those from sikes et al 1997 for the southern ocean to evaluate further uk37 and uk37 as proxies to estimate cold temperatures 10 c and the effect of salinity and temperature in the relative abundance of 37 4 to the total abundance of c37 alkenones 37 4 uk37 and uk37 are found to be equally viable as proxies but there are significant regional differences in their cold temperature dependence the measurement of 37 4 in cores from the north atlantic region can be used to identify situations when uk37 is not a reliable paleothermometer variations in salinity are probably responsible for changes in the sedimentary record of 37 4 and a preliminary calibration has been obtained for 37 4 f salinity this new relationship should be further confirmed through field or laboratory experiments but it paves the way to derive a molecular proxy to reconstruct paleosalinity in surface waters