late pleistocene uplift history along the southwestern marmara sea determined from raised coastal deposits and global sea level variations pleistocene raised coastal deposits characterized by locally abundant shells aragonite cemented beachrock and associated nearshore deposits border the western marmara sea at elevations of 0 50 m field observations confirm that these deposits formed during a series of transgressive and regressive events u th dates in 16 in situ shells from four localities show that the peak of the transgressions occurred during the highstands of oxygen isotopic stages 7 and 5 between 53 and 210 ka the elevations of these dated deposits can be used to quantify their post depositional uplift and indicate that the entire western marmara shelf including the strait of canakkale dardanelles has been rising at an average rate of 0 40 mm yr 1 since 225 ka the primary cause of uplift is the local compression associated with a restraining bend in the western segment of the north anatolian fault paleogeographic maps constructed using the average rate of tectonic uplift and detailed topographic and bathymetric maps reveal that prior to glacial oxygen isotopic stage 8 the marmara sea was never isolated from the aegean sea even when global sea level was low because the floor of the strait of canakkale was too deep early in its uplift history the dominance of mytilus edulis in raised coastal terraces dating from the lowstand of glacial oxygen isotopic stage 8 suggests that the degree of communication between the aegean sea and marmara sea was comparable to that of the present during the peak of glacial oxygen isotopic stage 6 the floor of the strait was subaerially exposed isolating the marmara sea for the first time in the pleistocene from the higher salinity mediterranean water inflow and possibly causing it to become a blackish water lake during interglacial isotopic stages 9 7 and 5 the strait of canakkale was very wide and deep 100 125 m and there were two subsidiary channels bolayir and eceabat channels providing additional links between the aegean sea the marmara sea further promoting significant water exchange between these basins the dominance of ostrea edulis in the raised terraces dating from isotopic stages 5 and 7 confirms an enhanced penetration of the mediterranean water mass into the marmara sea the history of communication between the black sea fed by central and northern european drainage systems and the low latitude mediterranean sea is of fundamental importance in understanding the genesis of organic rich sapropel deposits throughout the region the results presented in this paper caution against the simple assumption that sea level change alone controlled the degree of connection across this oceanographic gateway instead the physiography and paleoceanography of the region were controlled both by variations in global sea level and the rate of uplift in an area of active transpression

a revised calendar age for the last reconnection of the black sea to the global ocean abstract during the last decade a debate arose regarding the timing and pattern of the last reconnection of the black sea lake with the global ocean on a geochemical basis the radiocarbon age of black sea lake surface water during the time of reconnection was determined to be 8400 14c a bp despite the potential bias induced by the hard water effect in lakes the reconnection age was calibrated without any reservoir age correction which led to an estimate of 9400 cal a bp since knowledge for the actual calendar age has important hydrologic implications that would provide new insights regarding the mechanism of reconnection determining the actual calendar age for the last reconnection remains important based upon modeling experiments and micropaleontological reconstructions the black sea lake reconnection occurred in two steps as follows 1 initial marine inflow imi followed by 2 a period of increasing basin salinity that led to the disappearance of lacustrine species dls in order to better define the actual calendar age for the last reconnection a review of the sedimentary expressions of the imi and dls boundaries was performed in order to correlate them throughout the black sea sedimentary environments this correlation reconciles the apparent inconsistency in the published radiocarbon dataset and provides the atmospheric radiocarbon age of the last reconnection which represents the reference for reservoir age calculations and which can be directly calibrated we determine reservoir ages for the water column as well as the reconnection calendar age to be 9000 cal a bp at the reconnection with the global ocean black sea lake reservoir ages were non negligible and water depth dependent consistent with a weak water column stratification during the early holocene the calibrated age of initial marine inflow 9000 cal a bp implies that the former bosphorus sill was shallower by 10 m than is commonly assumed in the literature compared to the sedimentary context of the sakarya coastal plain this result suggests that the level of the isolated black sea was below the former bosphorus sill depth at the time of the last reconnection furthermore a lag of 900 yr between initial marine inflow and the disappearance of lacustrine species indicates that approximately ten centuries were needed to establish the currently observed two way flow exchange with the global ocean

organic geochemistry and origin of late glacial holocene sapropelic layers and associated sediments in marmara sea abstract organic geochemistry of two sapropel sapropelic sediment units dated 10 6 6 4 and 3 8 3 2 kyr bp and associated sediments in two gravity cores from the marmara sea were studied to characterize the organic matter and discuss its paleoceanographic implications vertical trends of c n ratio 13c and hydrogen indices show that the flooding of the marmara sea by the mediterranean waters at 12 kyr bp and onset of deposition of the lower sapropelic layer at 10 6 yr bp are characterized with a high input of terrestrial organic matter this terrestrial input decreased and marine organic matter contribution increased in time towards the top of the upper sapropelic layer at 3 2 kyr bp the lower sapropelic layer is broadly the same age and has a similar distribution of organic matter type as the s1 sapropel of the aegean sea suggesting their depositions may have been controlled by the same events both the lower marmara sapropelic layer and the aegean s1 sapropel were probably deposited during a time of high influx of organic rich river waters from the black sea this influx of black sea water could have induced water stratification in the marmara sea and aegean sea and lead to the deposition of the sapropels

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

the last reconnection of the marmara sea turkey to the world ocean a paleoceanographic and paleoclimatic perspective during the late glacial marine isotope stage 2 the marmara sea transformed into a brackish lake as global sea level fell below the sill in the dardanelles strait a record of the basin s reconnection to the global ocean is preserved in its sediments permitting the extraction of the paleoceanographic and paleoclimatic history of the region the goal of this study is to develop a high resolution record of the lacustrine to marine transition of marmara sea in order to reconstruct regional and global climatic events at a millennial scale for this purpose we mapped the paleoshorelines of marmara sea along the northern eastern and southern shelves at cekmece prince islands and imrali using data from multibeam bathymetry high resolution subbottom profiling chirp and ten sediment cores detailed sedimentologic biostratigraphic foraminifers mollusk diatoms x ray fluorescence geochemical scanning and oxygen and carbon stable isotope analyses correlated to a calibrated radiocarbon chronology provided evidence for cold and dry conditions prior to 15 ka bp warm conditions of the bolling allerod from 15 to 13 ka bp a rapid marine incursion at 12 ka bp still stand of marmara sea and sediment reworking of the paleoshorelines during the younger dryas at 11 5 to 10 5 ka bp and development of strong stratification and influx of nutrients as black sea waters spilled into marmara sea at 9 2 ka bp stable environmental conditions developed in marmara sea after 6 0 ka bp as sea level reached its present shoreline and the basin floors filled with sediments achieving their present configuration

defect structures in naturally deformed clinoamphiboles a tem study abstract naturally deformed clinoamphiboles from the selbu tydal and forsback tarnaby areas of the scandinavian caledonides exhibit a well defined subgrain microstructure from a transmission electron microscopy study tem the subgrain boundaries are shown to consist of arrays of positive and negative screw dislocations with burgers vector b 001 locally expanded loops are present having long screw segments the subgrain boundaries are parallel to rational crystallographic planes of the type hk 0 the density of isolated dislocations within the subgrains is low in addition planar defect structures parallel to 010 and bounded by screw dislocations with b x 001 x are observed based on metamorphic criteria the p t values at the time of the amphibole growth have been estimated at 450 600 c and 4 6 kbar and these represent maximum conditions for the deformation the present results indicate that slip on hk 0 001 is an operative deformation mechanism in naturally deformed clinoamphiboles

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

distribution of surficial shelf sediments in the northeastern and southwestern parts of the sea of marmara strait and canyon regimes of the dardanelles and bosporus surficial sediment samples collected from the northeastern and southwestern shelf regions of the sea of marmara together with data available from other sources indicate marked variations in sediment compositions resulting from differences in topographical hydrological and biological conditions in the strait channels of the dardanelles and bosporus where strong undercurrents prevail the floor was covered mostly by coarse grained sediments rich in sand and gravel however in areas of relatively low energy conditions sediments contained appreciable amounts of mud with a tendency towards an increase in the amount of clay towards the open sea the effects of the strong undercurrents on the bedforms was also apparent in the southern strait of bosporus where sidescan sonar surveys revealed the presence of asymmetrical sand ripples although terrigenous mud is the principal sediment type in the two canyons dardanelles and south bosporus the sediments in particular on the floor of south bosporus canyon show a distinct contrast between the inner n s and outer e w trending parts along its axis where depths are greatest the outer part of the canyon appears to contain much more coarse sediment in part derived from the benthic communities than the inner canyon in general both the topography related current regimes and the biological activities in the study areas mostly determine the types and modes of sediment distribution among the biogenic components the calcareous corraline algae rhodophycae chiefly lithothamnium calcareum and l fruticolusum and the molusc families galeommatacae and cerithiospidae are associated with the prevailing mediterranean undercurrents especially in the shallower waters of the junction of the sea of marmara and strait of bosporus the relatively abundant mollusc species mytilus galloprovincialis and modiolus barbatus and the trochidae in the strait of bosporus are largely affected by black sea waters the wide range of carbonate concentrations in the sediments generally reflects the relative abundances of biogenic admixtures in the samples high carbonate percentages in the sediments are usually associated with low mud contents and vice versa interestingly the organic carbon contents of the sediments generally increase with proximity to the black sea suggesting influxes of appreciable amounts of organic matter from the black sea

late quaternary stratigraphic evolution of the inner continental shelf in response to sea level change santa catarina brazil abstract the inner continental shelf 0 50 m water depth off santa catarina southern brazil was investigated using seismic stratigraphic methods to identify and interpret the major seismic stratigraphic units and to reconstruct the late quaternary evolution of the inner shelf and coast the stratigraphy comprises a bedrock basement overlain by a thick 30 m unit that comprises in the distal portion laminated muds and sands and in the coast proximal zone offlapping deltaic deposits whose upper surface has been reworked to form alongshore prograding barrier spits deposition of this unit is tentatively attributed to sea levels 20 m msl during the late pleistocene mis 5a or 5c a normal fault in the muddy units with a vertical offset of 3 5 m indicates episodic tectonic activity cut into this unit is a profusion of incised valleys associated with sea level fall ultimately to 120 m at the last glacial maximum lgm the associated subaerial unconformity is only preserved close to shore where it has escaped subsequent wave ravinement this coupled with the well preserved incised valleys implies the underlying substrate to be weakly cohesive material mud the incised valleys display a variety of infilling sediments interpreted variously as basal fluvial sediments estuarine basin infill muds and marginal bar or barrier associated sands deposited during the postglacial marine transgression during a sea level stillstand at ca 50 m a 3 5 km wide planar surface was cut into the unconsolidated coastal plain sediments forming a terrace on which a thick sequence of sands accumulated this unit is regionally developed and the acoustic signature implies it to comprise littoral sand including a large aeolianite component the accumulation of sand on this mainland beach dune system is attributed to establishment of a mature littoral system with strong longshore drift the fact that it rests on an erosional surface that truncates incised valleys suggests the unit to be holocene in age it is interpreted to have been deposited during a still stand in the holocene and to have undergone aggradation and cementation until it was overstepped by sea level rise its surface and the coastal plain to landward were then subject to wave ravinement and a thin ca 5 6 m layer of modern marine sands was deposited on the eroded surface sea level rise continued to the regional glacio isostatic highstand of ca 5 5 m after which regressive strandplains developed in response to a renewed mature longshore drift system similar to that prevailing during the 50 m stillstand of sea level in the intervening period rapid shoreline translation over the low gradient surface inhibited the development of the longshore transport system the three shoreline systems identified show marked differences that relate to sea level change and the influence of the underlying topography shoreline 1 pleistocene highstand developed by localised wave reworking of delta deposits and involved a series of alongshore prograding barrier spits on a shoreline of alternating high relief bedrock and littoral sands in coastal re entrants shoreline 2 50 m was a major accumulation of beach and dune sand deposited as a mainland attached beach dune system on a low lying coastal plain environment shoreline 3 the modern coast comprises a series of headland embayment beaches strandplains and transgressive dunes with a strong bedrock control and a well developed longshore drift system delivering sediment northward

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

dynamic recrystallization and chemical evolution of clinoamphibole from senja norway clinoamphibole from a mylonitic amphibolite exhibits microstructures characteristic of dynamic recrystallization including porphyroclasts in a finer grained matrix of needle shaped amphibole the matrix amphibole defines an ls fabric and porphyroclasts have core and mantle structures with a core containing undulose to patchy extinction and 100 deformation twinning surrounded by a mantle of recrystallized grains in addition intragranular grains also occur within the cores tem analyses of the porphyroclasts reveal that they contain a wide variety of lattice defects including high densities 5 108cm 2 of free dislocations and dislocation arrays dissociated dislocations stacking faults and 100 micro twins tem also shows that matrix grains and intragranular grains have relatively low defect densities and that the intragranular new grains occur at localities in the porphyroclasts characterized by high densities of dislocations these observations along with the chemical and orientation relationships between the recrystallized grains and porphyroclasts indicate that the new grains may have formed by heterogeneous nucleation and that further growth probably occurred by both strain assisted and chemically induced grain boundary migration or liquid film migration this recrystallization event is interpreted to be synkinematic based on the fact that no recrystallization textures are present in the matrix grains and that the matrix grains define an ls fabric however the low defect densities in the matrix grains and the lack of intracrystalline strain in other phases indicate that post kinematic recovery processes were active

quantitative estimation of holocene surface salinity variation in the black sea using dinoflagellate cyst process length reconstruction of salinity in the holocene black sea has been an ongoing debate over the past four decades here we calibrate summer surface water salinity in the black sea sea of azov and caspian sea with the process length of the dinoflagellate cyst lingulodinium machaerophorum we then apply this calibration to make a regional reconstruction of paleosalinity in the black sea calculated by averaging out process length variation observedatfourcore sites fromtheblack seawithhigh sedimentation rates anddatedbymultiple mollusk shell ages results show averygradual change of salinity from w14 0 91 psu around 9 9 cal ka bp to a minimum w12 3 0 91 psu around 8 5 cal ka bp reaching current salinities ofw17 1 0 91 psu around

late pleistocene holocene sea level dynamics in the caspian and black seas data synthesis and paradoxical interpretations abstract different multidisciplinary data concerning the paleodynamics of sea level variations in the caspian and black seas are controversial in some aspects there are at least three paradoxes that are discussed in the paper the paradox no 1 relates to the early and late khvalynian transgressions that occurred in the cs during the second part of mis 3 35 25 ka bp and the late glacial epoch 17 12 ka bp respectively it is unclear what the main source or sources of water were that caused them paradox no 2 emerges from the comparison of climate events and transgressive regressive cycles in the caspian sea and the black sea it implies that large sea level anomalies occurred in accordance with global climate changes because they are influenced by climate variations however other not so long lived sea level fluctuations are poorly correlated with climate events the question is why climatically induced sea level changes did not follow climatic variations paradox no 3 concerns the contradiction between the massive water discharge from the black sea into the sea of marmara via the bosphorus strait and the black sea level fluctuations in the latest pleistocene holocene that could not exist simultaneously it is shown that paradox no 2 has been solved at least on conceptual level solutions to paradoxes no 1 and no 3 are still lacking further geological and geochronological evidence as well as climate simulation are required formulation of solutions for these paradoxes should make a major contribution not only to the problems of the caspian and black seas paleogeography but also provide help in explaining the reasons for inadequate simulation of regional climate changes this is important in the context of the development of models for future climate prediction

constraining holocene sea surface conditions in the south western black sea using dinoflagellate cysts this paper presents two dinoflagellate cyst records from the south western shelf of the black sea a new site mar05 13 from the sakarya shelf is described and placed into context with site mar02 45 250 km distant on the thracian shelf the records provide a centennial resolution of surface water conditions in the holocene analysis of the data suggests that the surface salinity of the south western shelf increased in a gradual and progressive manner in the period 11 000 9000 cal a bp the assemblages suggest surface water salinities between 7 13 psu the initial arrival of euryhaline species 8100 cal a bp is linked to the reconnection of the black sea and marmara sea the suggested surface water changes related to the reconnection took approximately 1000 years following this initial change in assemblages a further increase in the number of euryhaline species is noted between 5000 and 4000 cal a bp this is linked to the establishment of more saline surface water conditions close to present day values the record for mar05 13 highlights the complexity of the changes in cyst assemblages during the mid holocene copyright 2012 john wiley sons ltd

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

oxygen and carbon isotopes and trace element ca ratios in late quaternary ostracods loxoconcha lepida and palmoconcha agilis from the black sea paleoclimatic and paleoceanographic implications abstract oxygen and carbon isotopes and trace element ca ratios are presented for the valves of benthic ostracods palmoconcha agilis and loxoconcha lepida extracted from two composite sediment cores from the black sea shelf the two cores together provide a complete latest pleistocene holocene sedimentary record with 16 radiocarbon dated shells in core m02 45 and 9 in core m05 50 results reveal environmental changes and evolution of water chemistry associated with the last reconnection of the black sea to the global ocean the 18o values in composite cores m02 45 and m05 50 exhibit ranges of 8 0 and 3 0 respectively 13c values show ranges of 2 5 and 2 0 there are three isotopic substages a substage 1c 12 1 9 4 cal ka represents conditions in the neoeuxine lake with relatively high 13c and low 18o b substage 1b 9 4 6 3 cal ka represents the transition from lacustrine to marine conditions with an increase in 18o values as small amounts of mediterranean water flowed into the black sea and c substage 1a 6 3 cal ka to present represents the establishment of marine conditions like today with near constant 18o values and a trend of slowly increasing 13c trace element ca ratios show downcore trends consistent with the three isotopic substages at 6 3 cal ka isotopic data and trace element ca ratios exhibit a major shift with changes in the mg ca ratio suggesting an increase in water temperature from 12 14 c to 17 19 c these mid holocene changes in ostracod valve composition and environmental conditions coincide with the weakening of black sea outflow and the proliferation of marine organisms

the timing and evolution of the post glacial transgression across the sea of marmara shelf south of istanbul high resolution reflection seismic profiles with core analyses of sedimentary sequence near the sea of marmara som entrance to the strait of istanbul soi bosphorus provide detailed record of sealevel changes since the late glacial maximum lgm the sequence is deposited over the lgm erosional surface at a maximum depth of 105 m it includes seven seismic units that can be confidently correlated with 14c dated sedimentary units in the cores unit 6 represents levee deposits of the paleo soi channel that was deposited by a black sea outflow during 11 2 10 6 kyr bp the reflection surfaces at base of unit 5 and 4 correspond to wave cut terraces at 71and 63 m respectively and are estimated to be 10 6 and 9 8 kyr bp the seismic unit 2 overlaying a mud drape unit 3 comprises deltaic sediments that was deposited during 6 400 3200 yr 14c bp isopach map and

semibrittle and cataclastic deformation of hornblende quartz rocks in a ductile shear zone abstract hornblende quartz rock of the coniston shear zone i csz i at the grenville front canada was deformed dominantly by semibrittle flow of hornblende quartz aggregate and locally by cataclastic flow of hornblende aggregates fracturing and slip along fractures produced mesoscopic domino style deformation void formation associated with domino style deformation was prevented by leveling the corners of the slid segments of individual mesodominoes producing narrow shear zones the shear zones eventually coalesced to form the dominant mylonitic c foliation on the microscopic scale semibrittle flow was achieved by dynamic recrystallization of quartz concomitant with microcracking and microfaulting of hornblende into microdominoes and rotation shear and separation of the microdominoes plastic deformation of quartz accommodated the rotation and shear of the microdominoes thereby obviating the space problem local cataclastic flow occurred in the hornblende domains and produced r 1 riedel shear surfaces the observed processes are consistent with greenschist grade retrograde metamorphism accompanying post orogenic uplift along this zone

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

reply to comment on the timing and evolution of the post glacial transgression across the sea of marmara shelf south of istanbul by hiscott et al marine geology 248 228 236 in their comment hiscott and co authors adhere rigidly to ages and sources for sedimentary units in the subsurface of the marmara shelf that they have previously reported in their publications from 2002 through 2007 this adherence is in spite of a superior age depth model from our 13 m long sediment core that penetrated deeply into the deposits under consideration and in disregard to the results of subsequent more detailed and full coverage mapping of the region under scrutiny the age revisions are dismissed by the authors of the comment as representing sediments severely disturbed during coring we rebut this criticism the bosporus source attributed by them to the sedimentary units sampled and dated by us appears to be driven by their conception that the black sea had a persistent outflow prior to its two way connection with marmara irrespective of whether the outflow was persistent our reply shows that the drawing of the isopachs of the sedimentary units by hiscott and co authors was accomplished in a fashion to promote the bosporus source hypothesis regardless of the geographic limits of their survey the ages assigned to the units are equally indeterminate because the cores used by them have missing core tops of unknown lengths that are not discussed in their publications furthermore the sub bottom reflectors at the sites where the reflectors were calibrated to their only core without a missing top are actually hidden by the finite width of the bottom reflecting wavelet

early holocene age and provenance of a mid shelf delta lobe south of the strait of bosphorus turkey and its link to vigorous black sea outflow abstract the chronology of an abandoned holocene delta lobe present water depth 40 70 m on the northeastern shelf of the marmara sea south of the strait of bosphorus was revised from the early holocene 11 0 9 7 cal ka to the middle holocene 6 65 3 75 cal ka by eris et al eris k k ryan w b f cagatay m n sancar u lericolais g menot g bard e 2007 the timing and evolution of the post glacial transgression across the sea of marmara shelf south of istanbul marine geology 243 57 76 three independent seismic and multibeam surveys and replotting of navigational fixes for the 1992 1993 vintage survey lines which eris et al correlated to their md04 2750 giant piston core confirm that they misplotted the location of the md04 2750 core site on seismic profiles by a minimum of 200 m because of rapid convergence of seismic reflections in this critical area the assessment of the age of the holocene delta proposed by eris et al is incorrect instead existing and new data allow the age of this delta lobe to be refined to 11 1 10 2 cal ka 200 300 years each using several dated cores and the md04 2750 chronology itself a dense grid of previously unpublished seismic data shows that the lobe emanates from the strait of bosphorus and not from any of the local small streams mineralogy of the very fine sand fraction of the delta excludes the kurbagalidere stream as a source of the detritus as does the composition of detrital hornblendes it is concluded that the early holocene delta lobe indeed records a period of strong black sea outflow as advocated by co authors rnh and aea in 2002 re examination of multibeam imagery from the strait itself provides support for strong southward flow that potentially coincided with accumulation of the delta lobe at the southern exit of the strait

late quaternary ice sheet history of northern eurasia the maximum limits of the eurasian ice sheets during four glaciations have been reconstructed 1 the late saalian 140 ka 2 the early weichselian 100 80 ka 3 the middle weichselian 60 50 ka and 4 the late weichselian 25 15 ka the reconstructed ice limits are based on satellite data and aerial photographs combined with geological field investigations in russia and siberia and with marine seismic and sediment core data the barents kara ice sheet got progressively smaller during each glaciation whereas the dimensions of the scandinavian ice sheet increased during the last ice age the barents kara ice sheet attained its maximum size as early as 90 80 000 years ago when the ice front reached far onto the continent a regrowth of the ice sheets occurred during the early middle weichselian culminating about 60 50 000 years ago during the late weichselian the barents kara ice sheet did not reach the mainland east of the kanin peninsula with the exception of the nw fringe of taimyr a numerical ice sheet model forced by global sea level and solar changes was run through the full weichselian glacial cycle the modeling results are roughly compatible with the geological record of ice growth but the model underpredicts the glaciations in the eurasian arctic during the early and middle weichselian one reason for this is that the climate in the eurasian arctic was not as dry then as during the late weichselian glacial maximum

chronology of glacial lake agassiz meltwater routed to the gulf of mexico abstract sediment cores with new radiocarbon dates from the southern outlet of glacial lake agassiz indicate that meltwater delivery to the mississippi valley was disrupted at 10 800 14 c yr b p and the outlet was abandoned by 9400 14 c yr b p these findings confirm the timing of generally accepted terminations of the lockhart and emerson phases of lake agassiz additionally the radiocarbon chronology indicates that the spillway was fully formed by 10 800 14 c yr b p and that the occupancy in late emerson time was likely short lived with minimal spillway erosion

comment on the timing and evolution of the post glacial transgression across the sea of marmara shelf south of istanbul by eris et al marine geology 243 57 76 abstract in their recent paper eris and co authors attempt to refute much of our work on deltaic sediments at the southern exit of the bosphorus strait turkey first their age model is completely inconsistent with the well constrained chronology of our cores mar02 110 and mar02 111 their calypso core md 2750 must have seriously oversampled the holocene section giving an erroneous impression of true thicknesses and ties to seismic data and therefore leading to an incorrect assessment of the timing of deltaic sedimentation second they have ignored evaporative drawdown in the marmara sea from 14 7 11 3 ka lowering of the sea surface by evaporation is a better explanation for a lowstand shoreline at 83 m elevation than their proposal that the dardanelles sill was this deep at the time of reconnection with the global ocean third we contest their conclusion that the uppermost delta in this area was sourced from the kurbagalidere river the sediment flux of this river is too little it cannot account for the strong upward climb of the topset to foreset transition into a rapidly rising ocean and eris et al make no attempt to explain the absence of a precursor shelf edge delta that would be mandatory if this river had the water and sediment discharge that they suggest

the periglacial climate and environment in northern eurasia during the last glaciation this paper summarizes the results of studies of the late weichselian periglacial environments carried out in key areas of northern eurasia by several queen teams european science foundation esf programme quaternary environment of the eurasian north the palaeoglaciological boundary conditions are defined by geological data on timing and extent of the last glaciation obtained in the course of the eu funded project eurasian ice sheets these data prove beyond any doubt that with the exception of the northwestern fringe of the taymyr peninsula the rest of the eurasian mainland and severnaya zemlya were not affected by the barents kara sea ice sheet during the last glacial maximum lgm inversed modelling based on these results shows that a progressive cooling which started around 30 ka bp caused ice growth in scandinavia and the northwestern areas of the barents kara sea shelf due to a maritime climate with relatively high precipitation along the western flank of the developing ice sheets in the rest of the eurasian arctic extremely low precipitation rates less than 50 mm yr 1 did not allow ice sheet growth in spite of the very cold temperatures palaeoclimatic and palaeoenvironmental conditions for the time prior to during and after the lgm have been reconstructed for the non glaciated areas around the lgm ice sheet with the use of faunal and vegetation records permafrost eolian sediments alluvial deposits and other evidences the changing environment from interstadial conditions around 30 ka bp to a much colder and drier environment at the culmination of the lgm at 20 15 ka bp and the beginning of warming around 15 ka bp have been elaborated from the field data which fits well with the modelling results

magnitude and symmetry of seismic anisotropy in mica and amphibole bearing metamorphic rocks and implications for tectonic interpretation of seismic data from the southeast tibetan plateau we calibrated the magnitude and symmetry of seismic anisotropy for 132 mica or amphibole bearing metamorphic rocks to constrain their departures from transverse isotropy ti which is usually assumed in the interpretation of seismic data the average bulk vp anisotropy at 600 mpa for the chlorite schists mica schists phyllites sillimanite mica schists and amphibole schists examined is 12 0 12 8 12 8 17 0 and 12 9 respectively most of the schists show vp anisotropy in the foliation plane which averages 2 4 for phyllites 3 3 for mica schists 4 1 for chlorite schists 6 8 for sillimanite mica schists and 5 2 for amphibole schists this departure from ti is due to the presence of amphibole sillimanite and quartz amphibole and sillimanite develop strong crystallographic preferred orientations with the fast c axes parallel to the lineation forming orthorhombic anisotropy with vp x vp y vp z effects of quartz are complicated depending on its volume fraction and prevailing slip system most of the mica or amphibole bearing schists and mylonites are approximately transversely isotropic in terms of s wave velocities and splitting although their p wave properties may display orthorhombic symmetry the results provide insight for the interpretation of seismic data from the southeast tibetan plateau the n s to nw se polarized crustal anisotropy in the sibumasu and indochina blocks is caused by subvertically foliated mica and amphibole bearing rocks deformed by predominantly compressional folding and subordinate strike slip shear these blocks have been rotated clockwise 70 90 around the east himalayan syntaxis without finite eastward or southeastward extrusion in responding to progressive indentation of india into asia

holocene paleoecology and paleoceanography of the southwestern black sea shelf revealed by ostracod assemblages abstract the holocene replacement of ponto caspian ostracod assemblages by mediterranean species is studied in two long composite cores m02 45 a composite of cores m02 45p m02 45 t and m05 03p and m05 50 a composite of cores m05 50p and m05 51g acquired at sites 69 m and 91 m deep on the southwestern black sea shelf composite core m02 45 was collected from the middle shelf and composite core m05 50 was acquired on the distal fringe of the eastern levee of a saline underflow channel emanating from the strait of bosphorus sixteen radiocarbon dates in m02 45 and nine in m05 50 are used to construct age models which show recovery of sediments as old as 12 915 cal yr bp m02 45 site and 12 010 cal yr bp m05 50 site a total of 45 ostracod species are identified in the two cores from 12 000 to 7425 cal yr bp the ostracod assemblage is dominated by ponto caspian species mainly loxoconcha sublepida l lepida and tyrrhenocythere amnicola donetziensis from 7425 to 6315 cal yr bp the assemblage consists of nearly equal abundances of mediterranean species cytheroma variabilis in m02 45 sagmatocythere littoralis in m05 50 and the ponto caspian species after 6315 cal yr bp to the tops of the cores the assemblage is dominated by mediterranean species including palmoconcha agilis carinocythereis carinata hiltermannicythere rubra and pterygocythereis jonesii cluster analysis further subdivides the stratigraphic succession into six bioecozones with different ostracod assemblages the changes in the ostracod assemblages from one bioecozone to the next indicate that progressive environmental changes took place on the southwestern black sea shelf from at least 7500 cal yr bp to the present the first hint of changing conditions at 7500 cal yr bp lags the initial reconnection to the mediterranean sea through the strait of bosphorus by 2000 yr demonstrating that black sea salinity increased slowly and took that long to reach values tolerable to marine ostracod immigrants widespread colonization by mediterranean species took even longer 3000 years from the time of the initial reconnection

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

organized patches of bioherm growth where the strait of dardanelles enters the marmara sea turkey abstract high resolution multibeam mosaics show that the seafloor across the southwestern marmara sea is host to remarkably organized near circular bioherm mounds which commonly are arranged into large tightly packed clusters grab samples and gravity cores reveal that the bioherms are predominantly composed of very fine grained calcareous silty mud with abundant bioclasts including centimetre scale masses of coralline red algae and intact disarticulated mollusc shells mainly the genera modiolus and mytilus geometric analysis of multibeam images reveals that the average bioherm is 15 6 m in diameter occupies 190 m2 of seabed stands 113 cm above the adjacent seafloor and its crest is 20 6 m from the crests of neighbouring bioherms in regions of tightly packed bioherm clusters referred to as bioherm colonies the inter mound depressions are on average 4 4 m wide and 33 cm deep although each bioherm mound is nearly circular the surrounding inter mound channels form a more rectilinear mesh of linked pentagonal and hexagonal polygons suggesting densest possible spatial packing of the mounds near neighbour statistics of r 2 11 2 14 indicate an essentially uniform spacing between the bioherms which is the expected result for close packing on a plane and full utilization of the available space the bioherms occur at depths between 30 m and 60 m they are absent above and below these depths in this part of the southwestern marmara sea at the eastern exit of the strait of dardanelles water depth controls important water mass properties such as salinity nutrient supply and availability of light other inferred critical controls are the availability of a suitable hard substrate where holocene muds are thin or absent and nutrient supply potentially including a component from escaping methane rich pore fluids evidence here and elsewhere in the marmara sea provisionally dates the onset of bioherm growth and development to the latest pleistocene earliest holocene after global sealevel rose to the breach depth of the strait of dardanelles at 13 8 cal ka

high resolution sr isotopic evolution of black sea water during the holocene implications for reconnection with the global ocean abstract the 10 m thick holocene succession at core site m02 45 41 41 17 n 28 19 08 e 69 m water depth has key advantages for investigation of the sr isotopic evolution of the holocene black sea earlier studies have focussed on thinner successions and coquinas at the m02 45 site augmented by nearby core m05 03p 87sr 86sr determinations on mollusc shells extracted at mostly 10 20 cm depth increments provide a temporal resolution mostly

structural interpretation of the marmara region nw turkey from aeromagnetic seismic and gravity data abstract the seismically active marmara region located in nw turkey lies on the westward end of the north anatolian fault naf the naf is well defined on land previous investigations of its extension in the marmara sea include marine bathymetry seismological activity and seismic profiles in this study faults and their configurations identified inland are extended into the marmara sea by means of aeromagnetic anomalies as well as seismic and gravity profiles the deep structure was resolved by constructing a map of the tertiary bottom shallow curie isotherm was determined by spectral analysis indicating a thinner crust in the northern marmara depression area with respect to the continental crust a combination of the geophysical data allows us to propose the existence of subsidence and isostatic equilibrium in the northern marmara sea a less active zone identified in the central high zone dividing the marmara sea into two parts may also be deduced from the seismic data this structural arrangement may play a key role in earthquakes that will affect the surrounding regions

evaluation of the global oxygen isotope curve as a proxy for quaternary sea level by modeling of delta progradation patterns of delta progradation in rapidly subsiding basins have been used previously as a proxy for quaternary sea level change major transgression surfaces and maximum lowstand positions are readily recognizable in seismic reflection profiles quaternary sea level change can be approximated by stacked and tuned oxygen isotope records but significant departures from this proxy result from variation in isotopic composition of ice sheets temperature variations in the deep sea and the effect of bioturbation in degrading the isotopic record we analyze the influence of rapid quaternary sea level change on delta progradation in the eastern mediterranean using delta a multi process sediment transport model subsidence rates and sediment inputs may vary through time but compared to quaternary sea level change such variations were minor and had little effect on model results for a variety of geologically reasonable sediment inputs and subsidence rates the delta architecture observed in seismic profiles could not be reproduced when the sea level estimates were taken directly from a scaled global oxygen isotopic curve however when this sea level curve was corrected to include independent estimates of sea level from geological data elsewhere in the world previously used sediment inputs and subsidence rates invariably predict the general form of the observed architecture the difference between isotopic and geological estimates of sea level for the last 200 ka follows a linear trend that was applied to previous glacial interglacial cycles producing a corrected sea level history for the last 540 ka using delta over this time span the sea level history based directly on the oxygen isotope curve was again less able to reproduce the observed delta architecture compared with a corrected sea level history this study shows the importance of modeling delta progradation as an avenue for testing and exploring quaternary sea level history

glacier dammed lakes and geological work of glacial superfloods in the late pleistocene southern siberia altai mountains quaternary glacier dammed lakes ofsouthern siberia produced cataclysmic superfloods floodstreams at the initial and final glacial stages when the ice dams were unstable consequently the initial surface was greatly and geologically instantly transformed morphologic associations ofmountainous scablands developed similar to the diluvial complexes ofthe channeled scabland in north america giant diluvial ramparts and terraces bars diluvial berms and giant current ripple relief diluvial erosional and evorsional forms including spillways outburst and oversplash gorges and dry waterfalls are also present the discharges of the glacial superfloods which have been calculated by independent methods were hundreds ofcubic meters per second at the locations where the giant current ripple marks were formed up to millions of cubic meters per second within the gorges maximum discharges of18 10 6 m 3 s 1 were characteristic ofthe diluvial floods in the runoff channel f rom the chuya kuray system ofthe glacierdammed lakes below the mouth ofthe kuray depression as f as the settlement ofchibit the power ofthose floods reached 10 6 wm 2 these values exceed the hydraulic parameters ofthe jok ulhlaups from late quaternary lake missoula in north america the floods of which previously were considered the most powerful freshwater streams in earth history the last phenomenal glacial superflood with discharges in excess of1 10 6 m 3 s 1 occurred in the chuya and katun valleys no later than 13 000 years ago afterwards the glacier dammed lakes degraded simultaneously with the degradation of the glaciers the glacier dammed lakes ofthe intermontane basins in southern siberia disappeared completely at some time af ter 5000 years ago calculations ofthe hydraulics and the estimates ofthe geological activity ofthe quaternary jok ulhlaups mean that the diluvial processes of relief formation can now be viewed as the most powerful exogenous process r 2001 published by elsevier science ltd

detailed investigation of overwash on a gravel barrier abstract this paper uses results obtained from a prototype scale experiment barrier dynamics experiment bardex undertaken in the delta flume the netherlands to investigate overwash hydraulics and morphodynamics of a prototype gravel barrier gravel barrier behaviour depends upon a number of factors including sediment properties porosity permeability grain size and wave climate since overwash processes are known to control short term gravel barrier dynamics and long term barrier migration a detailed quantification of overwash flow properties and induced bed changes is crucial overwash hydrodynamics of the prototype gravel barrier focused on the flow velocity depth and discharge over the barrier crest and the overwash flow progression across and the infiltration through the barrier during the bardex experiment overwash peak depth 0 77 m velocity 5 m s 1 and discharge max 6 m 3 m 1 were high especially considering the relatively modest wave energy significant wave height 0 8 m conversely to schemes found in the literature average flow depth did not linearly decrease across the barrier rather it was characterised by a sudden decrease at the crest a milder decrease at the barrier top and then propagation as a shallow water lens over the backbarrier the barrier morphological evolution was analysed over a series of 15 min experimental runs and at the timescale of individual overwash events overall the morphological variation did not result from an accumulation of many small consistently erosive or accretionary events but rather the mean bed elevation change per event was quite large 10 mm and the overall morphology change occurred due to a small imbalance in the number of erosive and accretionary events at each location two relationships between overwash hydrodynamic variables were deduced from results 1 between overwash flow depth and velocity a power type relation was obtained and 2 a linear relation was observed between overwash flow depth and maximum overwash intrusion distance across the barrier top i e overwash intrusion findings from this study are useful to enhance the knowledge of overwash processes and also have practical applications on the one hand results shown here can be use for the validation of overwash predictive models and additionally the simple empirical relations deduced from the dataset can be used by coastal managers to estimate overwash intrusion distance which in turn can assist in the location of areas under risk of overwash and breaching

modelling the provenance of detritus flushed through the strait of bosphorus turkey during early holocene outflow from the black sea to the world ocean abstract source to sink tracing of very fine sand supplied to a controversial lower holocene deltaic lobe in the northeastern marmara sea was undertaken using sem backscatter mapping and quantitative mineral liberation analysis of very fine sand fractions forty two samples from the kurbagalidere goksu golden horn and riva watersheds and from oligo miocene outcrops along the southwestern black sea coast show that each of these potential sources has a distinct mineralogical fingerprint comparison with 11 samples from the lower holocene delta and 19 samples from the overlying mud drape show that no single source can account for the mineral proportions in the sand fractions of these depositional sinks but a mixed provenance provides good matches for the deltaic lobe quantitative mixing based on 250 000 monte carlo simulations suggests 50 contribution from oligo miocene successions of the southwestern black sea coast and inner shelf 20 contribution from the goksu stream and minor contributions from other sources including the kurbagalidere stream this balance of source contributions continued to supply the holocene mud drape until 6 cal ka after which local sources became more important it is hypothesized that unconsolidated sediment from a number of watersheds was parked along the coast of the neoeuxine lake and in the paleo bosphorus valley during the mis 2 lowstand a rising neoeuxine lake possibly swollen by glacial outburst floods from the altay region of central asia flushed 0 5 km 3 of this sediment through the strait of bosphorus to the deltaic lobe and permitted it to rapidly advance into the marmara sea which at that time was rising 1 m each 100 yr provenance of the lower portion of the holocene mud drape is consistent with continued black sea outflow throughout the deposition of sapropel m1 in the marmara sea

geology geography and humans battle for dominance over the delivery of fluvial sediment to the coastal ocean abstract sediment flux to the coastal zone is conditioned by geomorphic and tectonic influences basin area and relief geography temperature runoff geology lithology ice cover and human activities reservoir trapping soil erosion a new model termed bqart in recognition of those factors accounts for these varied influences when applied to a database of 488 rivers the bqart model showed no ensemble over or underprediction had a bias of just 3 across six orders of magnitude in observational values and accounted for 96 of the between river variation in the long term 30 years sediment load or yield of these rivers the geographical range of the 488 rivers covers 63 of the global land surface and is highly representative of global geology climate and socioeconomic conditions based strictly on geological parameters basin area relief lithology ice erosion 65 of the between river sediment load is explained climatic factors precipitation and temperature account for an additi

the holocene history of the ne black sea and surrounding areas an integrated record of marine and terrestrial palaeoenvironmental change here we present an almost complete and integrated holocene record of marine and terrestrial palaeoenvironmental change from the ne shelf of the black sea a dinoflagellate cyst record used to recon

variation in amphibole and plagioclase composition with deformation investigation of the mineral chemistry of a shear zone in an amphibolite facies metagabbro has shown that the composition of the amphibole and plagioclase varies with deformation chemical analyses of the rocks indicate that the shear zone approximates an isochemical system the amphibole varies progressively from an initial magnesio hornblende to a ferroan pargasitic hornblende in the shear zone alkalies ti and fe2 fe2 mg increasing while the plagioclase becomes more anorthitic varying from labradorite to bytownite these changes in composition of amphibole and plagioclase from metabasic rocks are normally associated with increasing temperature in prograde regional metamorphic terrains such chemical variations observed in localized shear zones would suggest that shearing stress in regional metamorphism may play an important role in producing the documented discrepancies in amphibole chemistry between different metamorphic belts

paleohydrology of late pleistocene superflooding altay mountains siberia cataclysmic flooding is a geomorphological process of planetary significance landforms of flood origin resulted from late pleistocene ice dammed lake failures in the altay mountains of south central siberia peak paleoflows which exceeded 18 x 10 6 cubic meters per second are comparable to the largest known terrestrial discharges of freshwater and show a hydrological scaling relation to floods generated by catastrophic dam failures these seem to have been earth9s greatest floods based on a variety of reconstructed paleohydraulic parameters

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

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

oscillating quaternary water levels of the marmara sea and vigorous outflow into the aegean sea from the marmara sea black sea drainage corridor abstract detailed interpretation of single channel air gun and deep tow boomer profiles demonstrates that the marmara sea turkey experienced small amplitude 70 m fluctuations in sea level during the later quaternary limited in magnitude by the sill depth of the strait of dardanelles moderate subsidence along the southern shelf and quaternary glacio eustatic sea level variations created several stacked deltaic successions separated by major shelf crossing unconformities which developed during the transitions from global glacial to interglacial periods near the strait of dardanelles a series of sand prone deposits are identified beneath an uppermost holocene transparent mud drape the sandy deposits thicken into mounds with the morphology and cross sectional geometries of barrier islands sand waves and current generated marine bars all cross stratification indicates unidirectional flow towards the dardanelles prior to the deposition of the transparent drape which began 7000 years bp in strong support of the notion that the marmara sea flowed westwards into the aegean sea through the dardanelles at times of deglaciation in northern europe the global sea level curve shows that at 11 000 and 9500 years bp sea level rose to the sill depths of the straits of dardanelles and bosphorus respectively the effect from 11 000 to 9500 years bp was seawater incursion into the marmara sea drowning and formation of algal serpulid bioherms atop lowstand barrier islands and transgression of shelves and lowstand deltas at 9500 years bp glacial meltwater temporarily stored in the black sea lake developed into a vigorous southward flow toward the aegean sea forming west directed sandy bedforms in the western marmara sea and initiating deposition of sapropel s1 in the aegean sea this strong outflow persisted until 7000 years bp after which a mud drape began to accumulate in the marmara sea and euryhaline mediterranean mollusks successfully migrated into a progressively more saline black sea where sapropel deposition began most eastern mediterranean sapropels from s1 to s11 appear to correlate with periods of rising sea level and breaching or near breaching of the bosphorus sill these events are believed to coincide with times of vigorous outflow of low salinity fresh surface waters transiting the black sea marmara sea corridor and ultimately derived from melting of northern european ice sheets

deep crustal extensional faulting in the ivrea zone of northern italy abstract the ivrea zone in northern italy consists of amphibolite and granulite facies metasedimentary metabasic and ultrabasic rocks and is thought to represent a section through the deep continental crust detailed mapping of the high grade part of this zone has revealed a series of high temperature shear zones which after the effects of later low temperature faulting and folding have been removed appears to accommodate extension of the sequence the shear zones formed at temperatures similar to those at which thermal equilibration occurred in the host rocks and locally show evidence for development under prograde conditions these observations fit well with thermal effects calculated from a simple heat flow model for extensional faulting in this model the effects of shear heating and displacement of cool hanging wall rocks against hotter footwall rocks are calculated these observations indicate that faulting as a mode of failure may be important during extension of the lower continental crust especially when basic rocks are the dominant components of the rock pile a restored section through the extended lower crust as observed in the ivrea zone is presented and the extent to which the features observed are able to explain seismic reflectivity of the lower crust is discussed

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

mylonitic deformation of gabbro in the lower crust a case study from the pankenushi gabbro in the hidaka metamorphic belt of central hokkaido japan abstract the mylonitization of the pankenushi gabbro in the hidaka metamorphic belt of central hokkaido japan occurred along its western margin at 600 mpa and 660 700 c through dynamic recrystallization of plagioclase and a retrograde reaction from granulite facies to amphibolite facies orthopyroxene clinopyroxene plagioclase h2o hornblende quartz the reaction produced a fine grained 100 m polymineralic aggregate composed of orthopyroxene clinopyroxene quartz hornblende biotite and ilmenite into which strain is localized the dynamic recrystallization of plagioclase occurred by grain boundary migration and produced a monomineralic aggregate of grains whose crystallographic orientations are mostly unrelated to those of porphyroclasts the monomineralic plagioclase aggregates and the fine grained polymineralic aggregates are interlayered and define the mylonitic foliation while the latter is also mixed into the former by grain boundary sliding to form a rather homogeneous polymineralic matrix in ultramylonites however in both mylonite and ultramylonite plagioclase aggregates form a stress supporting framework and therefore controlled the rock rheology crystal plastic deformation of pyroxenes and plagioclase with dominant 100 001 and 001 1 2 1 1 0 slip systems respectively produced distinct shape and crystallographic preferred orientations of pyroxene porphyroclasts and dynamically recrystallized plagioclase grains in both mylonite and ultramylonite euhedral to subhedral growth of hornblende in pyroxene porphyroclast tails during the reaction and its subsequent rigid rotation in the fine grained polymineralic aggregate or matrix produced clear shape and crystallographic preferred orientations of hornblende grains in both mylonite and ultramylonite in contrast the dominant grain boundary sliding of pyroxene and quartz grains in the fine grained polymineralic aggregate of the mylonite resulted in their very weak shape and crystallographic preferred orientations in the fine grained polymineralic matrix of the ultramylonite however pyroxene and quartz grains became scattered and isolated in the plagioclase aggregate so that they were crystal plastically deformed leading to stronger shape and crystallographic preferred orientations than those seen in the mylonite

analysis and modelling of gravity and piston coring based on soil mechanics the effects of gravity and piston corers on the dimensional accuracy of marine sediment cores is analysed using principles of soil mechanics a model for the coring process is built around the feedback that arises and develops between the core barrel and the sampled sediment this model for sediment response is applied to different hypothetical coring scenarios which are then compared to real examples providing insights into the specific effects of each sampling method and the development of these effects down core four cores from a single location on the iberian margin are found to contain stratigraphically intact successions that differ in length by a factor of up to 2 7 due solely to the different effects of each coring method these dimensional discrepancies are attributed to the combined effects of over sampling in the upper portions of the piston cores due to cable rebound causing upward piston acceleration and under sampling dominant in the basal portions of the open barrel gravity type cores it is suggested that heavier piston corers deployed on longer lighter cables are prone to greater over sampling ratios over longer stratigraphic intervals due to the increased likelihood and extent of cable rebound cable rebound may also give rise to double penetration of gravity corers resulting in repeated stratigraphic intervals knowledge of the dimensional accuracy of marine sediment cores is essential to an evaluation of past sedimentation rates and hence interpretations of past depositional processes it is therefore essential that we recognise the sampling effects of each coring method and their variability down core lest coring artefacts be interpreted as sedimentary signals different core types may be more suited to different palaeoceanographic investigations hence failing the development of a practical cable deployed recoilless piston corer a combination of a variety of core types will permit the best acquisition of the in situ stratigraphic truth our results suggest that a large diameter dc 20 30 cm square barrel gravity corer for the top 10 12 m combined with a cylindrical piston corer below 10 m may provide the least deformed material

eclogite inclusions from subducted metaigneous continental crust malpica tui allochthonous complex nw spain petrofabric geochronology and calculated seismic properties this study describes the strain geometry crystal plastic deformational features isotopic age of metamorphism and calculated seismic properties of two medium temperature eclogite types from the malpica tui allochthonous complex of variscan nw iberia the eclogite types are eclogites with coronitic garnets and eclogites with a planolinear fabric both of them were buried deformed and recrystallized under maximum p and t of 2 6 gpa and 610 640 c and subsequently exhumed in a late devonian subduction channel the metamorphic peak of the subduction exhumation cycle occurred ca 375 ma ago omphacite petrofabric ties eclogites with coronitic garnet to non coaxial constrictional strain and eclogites with planolinear fabrics to non coaxial flattening strain and stretching along the lineation we also used omphacite crystallographic preferred orientations to calculate and constrain the seismic properties of the eclogites the slight variations in petrophysical properties observed are interpreted to result from variations in the strain regime recorded by pristine eclogites or from variations in the modal proportions of the constituent high pressure minerals we foresee that eclogite in subduction metamorphic complexes might be either seismically undetectable or detected as planar features with high impedance contrasts relative to their host rocks

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

the chemistry of detrital chromian spinels and its implications for the geodynamic evolution of the eastern alps detrital chromian spinel is a key mineral in paleogeographic reconstructions the chemical compositions of the spinels provide even more specific information about their host ophiolites because their chemistry is related to the degree of melting of the mantle peridotite and thus to the geotectonic environment of ocean crust formation

a hydrological model of the black and caspian seas in the late pleistocene and early middle holocene abstract this topic area has been a controversial one since the concept of a catastrophic black sea flood was first proposed and there is still considerable disagreement between experts as to the exact sequence of events this paper describes a numerical model of the caspian and black sea basins together with flows through the manych spillway and the bosphorus strait the model has been calibrated against the deductions made by various researchers concerning past water levels and parameters such as river flow volumes and evaporation rates have been assigned to give reasonable agreement with these deductions the model successfully predicts flow through the manych spillway during the early khvalynian transgression of the caspian sea between 15 2 and 12 3 ky bp and not thereafter the black sea is predicted to reach a lowstand of 163 m in about 11 ky bp and then to fill relatively rapidly due to increased river inflow combined with a breakthrough of mediterranean water across the bosphorus sill in about 10 5 ky bp this is followed by a period of high outflow through the bosphorus and between 9 3 and 8 ky bp by rapidly rising salinity due to marine inflow at depth the model also highlights two significant points of conflict with the physical evidence these concern the lack of apparent reason for the sudden onset of sapropel formation in the black sea in 7 6 ky bp and the significant erosion that has apparently occurred across the manych sill

holocene sedimentation in the southwestern black sea interplay between riverine supply coastal eddies of the rim current surface and internal waves and saline underflow through the strait of bosphorus abstract an extensive grid of high resolution huntec deep tow seismic reflection profiles 9150 line km complemented by 72 gravity cores and 25 piston cores reveals that the sedimentary architecture of the southwestern black sea above a prominent shelf crossing unconformity is characterized by three allostratigraphic units allounits 1b 1c 1d separated by two regional unconformities and their correlative conformities 1 and 2 a fourth allounit 1a occurs as patchy remnants between the unconformity and a deeper pleistocene erosional unconformity 0 the chronology is established using 56 radiocarbon dates in five key piston cores the unconformity developed as a ravinement surface during the transgression associated with the transition from the last glacial maximum to holocene thus defines the base of the holocene successions allounit 1b is bounded at its base and top by the and 1 unconformities correlative conformities it was deposited between 12 5 and 7 4 cal ka and shows a notably patchy but widespread distribution across the southwestern shelf allounit 1c is bounded at its base and top by the 1 and 2 unconformities correlative conformities it was deposited between 7 4 and 5 3 cal ka allounit 1d accumulated above the 2 unconformity correlative conformity and was deposited since 5 3 cal ka interpretation of radiometrically dated cores and several detailed regional maps reveal that the widespread occurrence of 12 5 7 4 cal ka deposits allounit 1b across the middle and outer shelf provides no possibility for a holocene evaporative drawdown to a lowstand elevation of 120 m at 9 4 cal ka as suggested by yanchilina et al 2017 instead the volume of detritus in allounit 1b can only be explained if base level was sufficiently high to allow major distant rivers in bulgaria and romania e g kamchiya danube to contribute mud through long distance marine transport along a submerged shelf there is no evidence in any cores which sample allounit 1b that the sites were located in limans rather than on a transgressed shelf which had been flooded by post glacial meltwater and enhanced river runoff as the climate became more humid in the early holocene a prolonged stillstand at the spill depth controlled by the sill in the strait of bosphorus is confirmed by the elevation of a drowned recurved spit downdrift from cape emine bulgaria the development of the subaqueous unconformities correlative conformities 1 and 2 was facilitated by storm induced wave erosion transport bypass and erosion under the rim current and its anticyclonic eddies and possibly breaking internal waves volumetrics based on isopach maps and pre industrial sediment discharge rates of various rivers entering the western and southwestern black sea suggest that the total sediment yields of bulgarian and turkish rivers can only account for 13 14 of the total holocene succession allounits 1b 1d and that major input from the danube river via along shelf long distance transport must have occurred through the entire holocene

stress gradients around porphyroclasts palaeopiezometric estimates and numerical modelling abstract based on strain gradients commonly found around porphyroclasts the mechanical interaction of porphyroclasts and recrystallized mylonite matrix in a retrograde amphibolite facies shear zone of the ivrea verbano zone italy was investigated differential stresses inferred from recrystallized grain size and dislocation density indicate stress concentrations at the porphyroclast matrix interface of about 1 7 2 0 with respect to the average in the matrix the palaeopiezometric stress data are compared to the results of a finite element model composed of two rheologically different phases in this model the local distribution and concentration of stresses around porphyroclasts mostly depend on clast matrix coupling and the effective viscosity contrast of the two phases the bulk strength and work hardening of the composite system increases with interface coupling both the modified stress field and the reduced average grain size around porphyroclasts may result locally in instabilities and promote strain localization and a change in the dominant deformation mechanism

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

late quaternary sedimentation in the strait of bosporus high resolution seismic profiling abstract uniboom profiling supported by borehole data in the southern part of the bosporus revealed that close to its banks holocene sediments are underlain by the faulted slopes of a valley cut in many places into the palaeozoic bedrock away from the banks the sediments thicken and their boundary with the underlying pleistocene deposits is defined by an erosional surface at about the 80 ms twt this surface marks the initiation of marine currents in the valley as its deeper parts began to be submerged in the late pleistocene to early holocene marine spillway phase the upward coarsening holocene sequence records the subsequent evolution of the present two way marine strait the sequence is divided into three seismostratigraphic units the lowest one constitutes an onlapping fill deposited under salt wedge estuarine conditions when sediment input and runoff discharge were high and sealevel was still rising but the flow of mediterranean waters into the black sea was not continuous it fills low areas and is well developed under a sill close to the southern entrance of the strait as sealevel rose closer to its present level and the rate of terrigenous input decreased in the middle holocene this unit began to be eroded and reworked by strong bottom currents the second unit records the transitional stage between the estuarine phase and the present two layered current system its seismic facies and sedimentary features indicate deposition under high energy conditions and shifting loci of accumulation the third surficial unit is a thin depositional lag rich in shell fragments blanketing the other two units it records deposition under fully marine conditions and flow of powerful bottom currents during the last few millenia