clay minerals in late glacial and holocene sediments of the northern and southern aegean sea different source areas oceanography and climate regimes influenced the clay mineral assemblages and grain size distribution of two sediment cores from the north and south aegean sea during the last glacial and the holocene in the north aegean sea clay mineral composition is mainly controlled by sea level evolution melting of southeastern european glaciers and establishment of the connection between the black sea and aegean sea the long term development of clay mineral assemblages in the south aegean sea reflects changes in the nile discharge and african dust input at this site the establishment of pluvial conditions in the nile catchment during the early to middle holocene resulted in a substantial rise in smectite illite ratios in the late holocene stepwise aridification of the southern borderlands caused an increase in windblown sediment material and a decrease in nile suspended material the clay mineral records exhibit periodic millennial scale fluctuations in the north aegean sea the changes are centred at a period of 1 3 1 8 ka and can be attributed to short term climate and weathering changes in the northern borderlands the changes in the south aegean sea are centred at periods of 3 2 4 3 1 9 2 4 and 1 3 1 7 ka reflecting short term changes in wind strength and northeast african hydrology 2007 elsevier b v all rights reserved

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

a record of glacial interglacial alternations in pleistocene sediments off new jersey expressed by clay mineral grain size and magnetic susceptibility data abstract clay mineral grain size and magnetic susceptibility measurements have been performed on a high resolution sampling of pleistocene clayey silts and silty clays drilled at odp site 902 hole d located on the upper slope off new jersey nw atlantic the combination of data from different techniques and their comparison with 18 o and gamma ray attenuation porosity evaluator grape data allow us to clearly distinguish between sediments deposited during glacial and interglacial cycles glacial sediments are poorly sorted rich in either clay or sand and characterized by the abundance of chlorite and high magnetic susceptibility values in contrast interglacial sediments are well sorted silt dominated and poor in chlorite the hudson river and its tributaries draining the appalachian highlands appear to constitute the perennial sources of the detrital input including quartz feldspars amphibole and a clay fraction dominantly composed of illite random mixed layers and kaolinite during glacial stages the terrigenous sedimentation was enhanced by additional input of chlorite from glacial erosion in northeastern america the variations in chlorite amounts supplied to the ocean were probably controlled by the ice sheet advances and retreats these variations are quantified by the kaolinite chlorite ratio k c which constitutes a reliable marker of glacial and interglacial influences on the terrigenous sedimentation

environmental control on shell structure and composition of agglutinated foraminifera along a proximal distal transect in the marmara sea abstract the study of benthic foraminifera in a complex marine system like the marmara sea is a key for understanding the influence of environmental factors on foraminiferal species density assemblage composition and shell construction this kind of study is important for further extensive use of foraminifera based investigation of water mass and sediment exchange between the eastern mediterranean and black sea through the marmara sea based on proximal distal transect from the southwest coast of the erdek bay to the top of canyon close to the north anatolian fault this study aims at defining the geochemical conditions at the seafloor and identifying the sediment constraints that act upon agglutinated test construction for selected species eggerelloides scaber textularia agglutinans textularia sagittula textularia truncata and textularia bocki grain size mineralogical and chemical analyses of their shells were investigated and confronted with the main geochemical conditions prevailing during deposition and within the sediment among grains used to construct the agglutinated foraminiferal tests from available grains both grain size selection and sorting have been evidenced this suggests that the mineralogical composition is related to the species and the sample localization within the basin our observations further suggest that bottom water conditions of the marmara sea do not have a significant influence on agglutinated foraminiferal shell development which is primarily driven by sediment characteristics our results are thus transposable to other environments

origin of late glacial holocene hemipelagic sediments in the aegean sea clay mineralogy and carbonate cementation abstract four hemipelagic lithological units are identified in the late glacial to holocene sediments in the aegean sea these lithologies are silty clay and clay in texture and include a varying mixture of loose terrigenous sediments supplied from the adjacent landmass gravel to sand sized cemented carbonate clasts and nodules sand to silt sized air born volcanic debris and biogenic remains sediment dispersal during the past 14 000 years was controlled mainly by the fluvial discharge rate by sea level variations which determined the proximity of basins to river mouths and by oceanographic conditions in the aegean sea cemented carbonate clasts and nodules occur in all sediments except unit c sapropel s1 they are well to friably cemented mottled to peloidal micrite or microcrystalline inter granular cement between terrigenous and bioclastic debris and the carbonate is 10 11 mole magnesium calcite during the deposition of sapropel s1 unit c the aegean sea was strongly stratified with colder more saline water masses occupying the deep basins which prevented the development of cemented carbonate nodules and clasts aragonite as pteropods and microcrystalline aragonite is present throughout the cores and together with the cemented carbonate clasts and nodules show that shallow pore waters in the aegean sea have been saturated to supersaturated with respect to both aragonite and magnesium calcite for at least the past 14 000 years results of xrd studies show that unit c sapropel s1 is characterized by lower smectite and kaolinite and higher illite and chlorite than the other units lower smectite illite and kaolinite chlorite ratios in unit c may reflect increased supply of illite and chlorite from european lowland rivers flowing into the black sea from rivers discharging directly into the northern and eastern aegean sea and decreased supply of kaolinite which is mainly of north african origin

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

a novel mineralogical approach for provenance analysis of late quaternary marine sediments the case of myrtoon basin and cretan sea aegean greece abstract sediments from two deep sea bottom cores from the myrtoon basin in the sw aegean sea and eastern cretan sea were examined by quantitative mineralogical and geochemical analysis to infer sediment provenance and climatic conditions and palaeo environmental control on sediment deposition both cores contain calcareous muds and silts with dark olive grey organic rich intervals corresponding to the regional sapropel s1 horizon the presence of a few tephra layers documents volcanic activity in the southern part of the aegean sea the bulk sediments contain abundant carbonate minerals mainly calcite and mg calcite and clay minerals mainly illite and smectite and accessory serpentine talc and hornblende which attest to contributions from ultrabasic sources there is a sharp decrease of the mg calcite content and the mg ca ratio of the carbonate fraction in sapropelic sediments followed by an increase of the average grain size a well expressed negative relationship between illite and smectite was observed in the clay fraction in full accordance with previous studies however this trend is absent from the bulk sediments because smectite is significantly overestimated in the oriented clay fractions clay mineral distribution is controlled mainly by sediment sorting with deposition in the sapropelic sediments being also affected by climatic changes the different types of smectite in the cores and the presence of smectite with high dehydroxylation temperature in the se aegean suggests that the sediment supply from se mediterranean sources should be limited

reconstructing precipitation changes in northeastern africa during the quaternary by clay mineralogical and geochemical investigations of nile deep sea fan sediments abstract clay mineralogy combined with high resolution element geochemistry of core md90 9064 located in the distal part of the nile deep sea fan levantine basin have been investigated to reconstruct rainfall changes in northeastern africa during the quaternary and to determine possible climatic controls clay minerals of core md90 964 are derived mainly from three sedimentary sources the sahara nile river and egyptian wadis and are characterized by contrasted mineralogical composition variations in illite content and logarithm ratios of si al and k al permit the tracking of eolian input from sahara to the mediterranean sea it is suggested that precipitation changes in the sahara are mainly dominated by glacial interglacial cycles such variations are owing to a shift of climatic conditions in the north atlantic from a nao positive like condition in glacial times to a nao negative like condition in interglacial times fe content in the levantine sediments is mostly derived from fe bearing heavy minerals brought by the nile river therefore variations of fe al ratios can be used to establish precipitation changes in the nile river basin long term variation in precipitation in the nile river basin is governed by precessional and eccentricity signals implying that the african monsoon is the most significant controlling factor for precipitation changes in this region precipitation changes in the northeastern coasts of africa are reconstructed using kaolinite contents provided by the egyptian wadis it is reported that precipitation in coastal northeastern africa is mainly of the mediterranean climate type long term variations in rainfall in this region are also affected by the nao like climatic variability and thus dominated by the glacial interglacial cycles

the circulation and hydrography of the marmara sea abstract a comprehensive set of data collected during 1986 1992 reveal seasonal and interannual variability in the circulation and hydrography of the marmara sea waters which have contrasting properties and originate from the adjacent basins supply the two layer stratified flows in the sea of marmara turbulent entrainment into the upper layer in the exit region of the bosphorus jet and wind stirring in winter both contribute equally to the basin vertical mixing the upper layer circulation of the marmara sea is determined from adcp measurements and from dynamical calculations based on hydrographic data the mean upper layer circulation is anti cyclonic mainly driven by the southward flowing bosphorus jet in the enclosed domain the bosphorus inflow is well defined except during the periods of low discharge in autumn and winter when the jet becomes weaker and tends to become attached to the west coast near the exit mediterranean water entering from the dardanelles supply the suhalocline layer the negatively buoyant plume of well oxygenated water is the only means of renewal of the deep waters partially compensating for the oxygen consumed by the degradation of organic matter sinking from the upper layer into the lower layer yet the subhalocline waters remain permanently deficient in oxygen as a result of the internal balances of diffusion advection and consumption the depth to which the plume penetrates is a function of the seasonal characteristics of the inflow density modified in the strait and the weak interior stratification

clay mineral and heavy metal distributions in the northeastern north sea abstract clay mineralogy and heavy metal distribution of surface sediments of the northeastern north sea have been analysed in order to show the origin and transport pathways of fine grained sediments the distribution patterns of clay minerals largely reflect regional current patterns fine material enriched in smectite derived mostly from the german bight sector in the south is transported by the jutland current parallel to the west coast of denmark into the skagerrak where a decreasing proportion of smectite indicates the increasing influence of the central and northern north sea currents illite and chlorite have identical distribution patterns in the northeastern north sea which suggests a common origin for both clay minerals this origin is located in pleistocene relict sediments of the northern north sea rather than in a contribution from the north atlantic zinc cadmium copper and lead in surface sediments of the north sea when compared to background values are significantly enriched sediments of the inner german bight are in comparison with other north sea sediments highly polluted a zone of high heavy metal contents zn cd and cu is found along the german and danish coasts comparable to the smectite distribution indicating the transport of fine grained polluted sediments to the north further to the north these sediments are diluted by less polluted sediments finally in the skagerrak and the norwegian trench a relatively low stage of pollution is reached

origin of the strait of canakkale dardanelles regional tectonics and the mediterranean marmara incursion abstract the regional tectonics and the mid to late quaternary seismic stratigraphy of the strait of canakkale dardanelles and its opening towards the aegean sea were interpreted by using shallow seismic profiles this strait is a narrow valley that resulted from regional uplift of the gelibolu and biga peninsulas in the pliocene as a consequence of compressional events generated by strike slip faulting activity of the ganos fault a northern strand of the north anatolian fault a nne ssw trending fault system between eceabat and canakkale believed to result from the left lateral displacement of the ganos fault on the gelibolu peninsula cut this valley into different segments the connection between the marmara basin and the aegean sea has been achieved after flooding of the connected valleys during the mid to late pleistocene three major sea level lowstands 130 150 m during this period 600 kyear bp interrupted the sea water connection at least twice three main seismic unconformities detected in the sediments of the strait of canakkale represent these lowstands minor sea level lowstands could have induced narrowing of the strait and erosion of depositional units the recent geological history of the strait of canakkale appears as deduced from the gelibolu peninsula and its western regions strongly related to escape tectonics influenced by the compressional forcing of the anatolian block in addition it also shows a morphological evolution which carries the effects of the global sea level variations

seasonal chemical and mineralogical variability of atmospheric particles in the coastal region of the northeast mediterranean abstract a time serial analysis of atmospheric particles collected since 1990 at a coastal site bordering the northeastern mediterranean sea shows that the collected samples display seasonal patterns in both concentration and color the 1990 91 and 1992 collections yield an annualised average of around 0 5 g day dust loading reducing to around 0 3 g day when the sea salt contribution is excluded the highest concentrations of atmospheric particles of continental origin for both natural e g fe mn and anthropogenic e g cd pb materials are observed between april and october and this variability is inversely related to the frequency and the amount of rainfall sea salt aerosol na contents do not follow this pattern but are related to local wind speeds trace elements in the dusts also display seasonal variations in enrichment factors ef with respect to average elemental abundances in crustal rocks the non enriched crustal elements appear to be indicators of long distance supply while the strongly enriched anthropogenic and moderately enriched suites of elements represents inputs from local or anomalous sources the similar morphology of quartz and calcite grains and the uniformity of the clay mineral assemblages in samples collected over a two year period strongly indicate a common source for the bulk of the atmospheric particles the dominant clay types palygorskite and smectite document a desertic source areas

mantle flow and plate motions summary new data on mantle viscosity variation and plate motions suggest that the author s previous theory for the forces driving and resisting plate tectonics needs revision the flow in the mantle associated with plate movements probably pervades the whole mantle instead of being almost entirely in a thin asthenosphere at the top of it the first task undertaken in this paper is a calculation of the viscous torque exerted on a hemispherical plate by a vertical point force in the mantle directly beneath the plate boundary this prototype problem is simple enough even with asthenosphere and mesosphere assigned different viscosities to allow the computing to be done with a large number of terms of the relevant spherical harmonic series it shows that forces in the lithosphere and asthenosphere are the major source of torques on plates especially if the asthenosphere viscosity is low and that truncating the series at a pre assigned degree can seriously underestimate the effect of a force in the asthenosphere these results are used as a guide to the approximations to adopt for more realistic boundary conditions where accurate computing by the same method as the prototype problem would be too time consuming to do the second task is estimating the torques actually driving and resisting the motion of the earth s plates it includes a recalculation of the ridge push driving mechanism which gives a zero resultant torque about the centre of the earth in agreement with archimedes principle but contrary to a recent conclusion of davis solomon the recalculation does not affect slab pull which still has a non zero resultant balanced mainly by a non zero mean angular velocity of the plate system relative to the mean mesosphere in which the hot spots are assumed in this work to lie this angular velocity agrees well with observational data and gives a test of the approximations on data not used in deriving them misfits between driving and resisting torques are found for each plate they are smaller for the present method than its best fitting competitor conclusions common to both are that the slab pull driving force must be appropriately weighted for age and speed and that the most important resisting

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 sea ecosystem variability of the aegean sea during the past 22 kyr as revealed by benthic foraminifera abstract specific responses of the regional deep sea ecosystems to climatic and oceanographic processes during the last 22 kyr are revealed by benthic foraminiferal faunas from two cores in the northern and southern aegean sea under glacial boundary conditions high diversity benthic foraminiferal faunas and elevated benthic foraminiferal numbers indicate enhanced organic matter availability and well ventilated deep water masses in the whole aegean sea the glacial termination is accompanied by significant fluctuations in productivity and deep water ventilation in the northern aegean sea meltwater inflow from mountain glaciers during the bolling allerod warm period resulted in a restriction of local deep water formation as mirrored by a dominance of bolivinids during the deposition of sapropel s1 drops in benthic foraminiferal number and diversity are more significant in the southern aegean sea when compared to the north this suggests the persistence of local deep water formation in the northern aegean sea during s1 deposition in addition faunal fluctuations within s1 at both sites suggest the repeated influence of short term cooling events on the re ventilation and re colonization of aegean deep sea ecosystems during the middle and late holocene benthic foraminiferal faunas document the establishment of oligotrophic and well ventilated conditions in the southern aegean sea the corresponding faunas from the northern aegean sea reflect generally mesotrophic conditions and variable deep water oxygenation during the entire holocene the deep sea ecosystems of this region responded very sensitively to short term changes in humidity and temperature these abrupt climate changes controlled the inflow of nutrients from rivers and the black sea and the formation of local deep water masses

distribution of clay minerals in surface sediments of the aegean sea a compilation extensive published data sets and some new data on the clay mineral composition of surface sediments in the aegean sea northeastern mediterranean sea have been compiled in order to map the distribution patterns of clay mineral assemblages and to decipher source areas and transport paths we distinguished six provinces a northwest aegean province a marmara dardanelles province a west turkey province a southeast aegean province a kithira province and a central aegean province the clay mineral assemblages in the coastal and shelf areas carry the signature of the riverine sediment discharge from southeast europe and turkey respectively the southern aegean sea is probably influenced by the river nile discharge and transport of clay minerals by surface currents the clay minerals in the central aegean sea form a mixed assemblage comprising components of the other assemblages a dispersion and dilution of clay minerals by surface currents is obvious

radiogenic heat production in the continental crust abstract the thermal structure and evolution of continents depend strongly on the amount and distribution of radioactive heat sources in the crust determining the contribution of crustal rocks beneath a superficial layer is a major challenge because heat production depends weakly on major element composition and physical properties such as seismic wavespeed and density enriched granitic intrusives that lie at the current erosion level have a large impact on the surface heat flux but little influence on temperatures in the deep crust many lower crustal rocks that are poor in heat producing elements are restites from ancient orogenic events implying that enrichment of the upper crust was achieved at the expense of deeper crustal levels for the same total heat production concentrating heat sources in an upper layer acts to reduce temperatures in the lower crust thereby allowing stabilization of the crust the present day structure of the crust is a consequence of orogeny and should not be adopted for thermal models of the orogenic event itself this review summarizes information extracted from large data sets on heat flow and heat production and provides estimates of crustal stratification and heat production in several geological provinces analysis of global and regional data sets reveals the absence of a positive correlation between surface heat flow and crustal thickness showing that the average crustal heat production is not constant differences of heat flow between geological provinces are due in large part to changes of crustal structure and bulk composition collating values of the bulk crustal heat production in a few age intervals reveals a clear trend of decrease with increasing age this trend can be accounted for by radioactive decay indicating that thermal conditions at the time of crustal stabilization have not changed significantly for the average crustal thickness of 40 km moho temperatures are near solidus values at the time of stabilization suggesting an intrinsic thermal control on crustal thickness and heat production distribution crustal thickening by more than about 10 km above this mean value induces changes of gravitational potential energy that exceed the strength of the lithosphere for several provinces where strong constraints on heat production are available it is shown that prior to intracrustal fractionation only modest amounts of thickening were needed to generate the conditions of ultra high temperature metamorphism the tell tale signature of crustal heat production is anatectic and metamorphic events that lag the cessation of orogenic activity by several tens of million years crustal heat production is decreasing with time because it is due to the radioactive decay of uranium thorium and potassium its rundown is responsible for the secular cooling of lithospheric roots at a typical rate of about 100 k gy 1 implying complex thermal interactions with a convecting mantle that is not cooling at the same rate

clay mineral variations in the northeastern nile delta as influenced by depositional processes abstract a study of five holocene sections cored in the northeastern nile delta egypt indicates that smectite and kaolinite dominate the clay mineral assemblages that illite is of lesser importance and that proportions of chlorite are usually very low of note is the poor or lack of correlation among the clay mineral assemblages and time related stratigraphic position in the cores and the moderate to good relationships among mineral assemblages grain size and geographic location of the three major minerals illite appears most closely related with grain size we suggest that changes in deposition particularly those related to transport processes and flocculation effective in former nile delta front environments best explain upcore fluctuations in the proportions of clay minerals observed in the five cores the percentages of kaolinite in the delta clay mineral assemblages are generally higher than those recorded in the nile river and in distal offshore nile cone and levantine basin regions this probably resulted from selective entrapment of kaolinite relative to smectite near former coastlines and by passing of the latter mineral to sectors beyond the delta front moreover smectite values are highest in one core located south of lake manzala a site near what may have been the mouth of a former branch tanitic of the nile which flowed east of the present damietta branch climate and related paleoceanographic conditions fluctuated markedly in the eastern mediterranean during the holocene it is concluded however that depositional processes rather than climate have been largely responsible for observed vertical and lateral changes in clay mineral proportions in deposits accumulating in these sedimentologically active nile fluviomarine environments

hydrographic deltaic and benthogenic controls of sediment dispersal in the gulf of iskenderun se turkey e mediterranean abstract grain size carbonate and organic carbon data obtained from a total of 73 surficial bottom sediments together with some available hydrographic data were used to investigate the major depositional characteristics and the sediment transport paths on the shelves of the gulf of iskenderun sediments with more than 30 biogenic carbonate composed of a variety of benthic organisms remains have formed a belt on the sea floor of the gulf entrance which extends northwards to the offshore ceyhan delta and eastward along the southern coast north westerly and easterly flowing open sea currents low terrigenous sedimentation bathymetry and high topographic relief of the coastal hinterland seems to be responsible for the formation of this benthogenic bottom zone the two other benthogenic bottom zones found in the eastern and north eastern parts of the gulf are under the influences of increased anthropogenic activities and ephemeral fluviatile input of terrigenous material the typical seaward profile of the offshore ceyhan delta near shore delta front pro delta and offshore facies was actively modified by current action the ratio of silt clay clay medium silt clay coarse silt and fine silt coarse silt fractions of the sediments revealed the occurrences of at least two distinct patterns of concentric zonal depositions which are in good agreement with the prevailing hydraulic gyre regimes in the gulf these depositional zonal patterns are characterized by the increased fractionation processes that separate finer grained and coarser grained fractions whereby clay contents increase towards the centres of these gyres predominantly in an offshore direction similar zonal deposition was also mirrored by the organic carbon contents of sediments we propose patterns of water movement and sediment pathways in the gulf of iskenderun based upon the interpretation of water current data and analysis of sedimentological data particular conditions for transportation and deposition of terrigenous materials and benthic accumulation are discussed this model produces a database for understanding dispersal of pollutants in association with water and fine grained sediment in this gulf opyright 1998 academic press limited

sedimentology and mineralogy of surficial bottom deposits from the aegean canakkale marmara transition eastern mediterranean effects of marine and terrestrial factors abstract grain size carbonate and xrd mineral data of surficial shelf sediments from 113 stations in the aegean marmara transition revealed the presence of three distinctive sectors which were controlled by the changing morphologic hydrodynamic benthic and terrigenous conditions that lasted during the late quaternary the northeastern aegean sea forms the western sector of the study area this region shows several bank and ridge like bottom features at 60 70 m water depths which are widely capped with sand and gravel up to 93 of both biogenic 30 caco 3 and terrigenous 3 origin the low abundances of fine grained materials 1 24 mud in this biogenic belt are probably in response to higher current velocities in the sea and to low fluvial discharges from the adjacent land masses biogenic materials consist of a large variety of calcareous remains of benthic organisms which are partly cemented by carbonate it is hypothesized that this biogenic belt at least in part is a relict feature canakkale strait is the central sector of the study area and its bottom is covered largely by terrigenous sand and gravel 3 the coarse grained nature of the sea floor of canakkale strait can be explained by the prevailing high current velocities western marmara sea is the eastern sector of the study area where the local major rivers supply a great part of the terrigenous materials and the prevailing low current velocities favour fine grained materials deposition here 3 up to 99 mud calcite mainly mg calcite 5 92 quartz 3 72 feldspars mainly plagioclase 7 56 and micas are the major bulk minerals in the sediments except for mg calcite which is mainly derived from calcareous biogenic components bulk minerals reflect a terrigenous source from the adjacent land masses in particular the overall lower qtz fsp ratios in the study area 0 4 1 2 showed significant increases i e enrichment of quartz relative to feldspars qtz fsp 1 2 2 4 in the inner biogenic belt of the northern aegean sea where older or relic early holocene sediments are suspected to occur if so these values can be used as an indicator for long duration of lowstands of sea level and associated intense current and wave activities 17 a expandable smectite 23 84 illite 12 43 and kaolinite 6 38 determined in the less than 2 m of the sediment are the major clay minerals higher abundances of smectite relative to illite and kaolinite found in sediments particularly off the mouths of rivers karamenderes gonen and biga and off the gokceada and bozcaada islands reflect mainly local sources for the clay minerals studied the higher smectite illite ratios of abundances are largely attributed to the weathered volcanic rocks which are widely distributed on the surrounding land masses however the prevailing current and wind patterns seem to be important factors controlling clay mineral distribution in marine sediments of this study

sea level changes and related depositional environments on the southern marmara shelf abstract petrographic data obtained from 182 surface sediment samples together with the available bathymetric data are used to investigate the effects of the last major sea level changes on shelf evolution in the southern sea of marmara grain size analysis reveals the presence of at least three belts or zones which are rich in coarse grained sand and gravel sediments these coarse grained belts which are up to 45 km long 15 km wide show up to 20 m of relief and are presently found at 40 80 m average 60 m water depths based on microscopic examination and residual analysis the sediments from these belts are interpreted as indicators of high energy shallow waters where detrital siliciclastics with some benthic contribution accumulated the presence of a 62 65 m deep sill in the canakkale strait and the consideration of sea level curves would suggest that the marmara shelves must have been subaerially exposed down to 65 m water depths for about 10 000 yrs 22 000 12 000 yrs b p sufficient time to modify former shelf topographies and form such bottom relief while difficult to date we believe that coarse grained belts found on the southern marmara shelf must be relict i e former shorelines beaches and their formation is largely related to low stands of sea level during the late pleistocene regression and early holocene transgression however the available high resolution seismic profiling data suggest that the neotectonism in this seismically active sea of marmara plays an important role to explain the raise of these older shorelines to their present levels on the sea floor

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