pleistocene holocene calcareous nannofossil biostratigraphy of core samples from the northeastern sea of marmara fenerbahce pendik nw turkey abstract pseudoemiliana lacunosa gephyrocapsa oceanica and emiliania huxleyi ionian pleistocene holocene calcareous nannoplankton zones were identified from 82 samples of 14 cores taken from 8 locations in the northeastern sea of marmara the investigation indicates that the identified biozones have been alternated by tectonic activity in the 1 5 and 6 core locations the study area has been affected three times by tectonic activity during the pleistocene holocene time interval the first activity occured during the early pleistocene and the others during holocene

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

holocene slip rate of the north anatolian fault beneath the sea of marmara abstract the north anatolian fault naf is a major continental transform system that extends e w across turkey for over 1600 km separating the anatolian and eurasian plates a portion of its northern branch runs below the sea of marmara this portion constitutes a seismic gap because the last destructive earthquakes occurred at the western 1912 ganos earthquake m 7 4 and eastern 1999 izmit and duzce earthquakes m w 7 4 7 2 edges of the marmara basin it is likely that fault ruptures will fill this gap in the next decades this region of the north anatolian fault is critical to our understanding of fault interactions stress buildup during seismic cycle and seismic hazard in the istanbul area we obtained high resolution acoustic images of the naf in the floor of the eastern marmara sea gulf of izmit and measured fault related offsets of 14 c dated subseafloor channels and paleoshorelines the resulting average slip rate on the fault is 10 mm year for the last 10 kyr this is less than half the total anatolia eurasia relative motion estimated at 24 mm year for the last 10 years from satellite geodetic measurements we conclude that either much of the strike slip motion along this branch of the naf did not occur on the main fault segment or the slip rate increased recently or both these results affect kinematic models of the naf and assessments of seismic hazard for the city of istanbul and the surrounding region

late quaternary climate and sea level changes recorded in sediment composition off the buyuk menderes river delta eastern aegean sea turkey abstract influences of holocene climatic and sea level changes on sedimentation on the continental shelf off the buyuk menderes river delta sw turkey were investigated using grain size and x ray clay mineralogical data on surficial and 14c dated core sediments collected at 19 81 m water depths modern fine grained siliciclastic sediments cover most of the seafloor of inner to mid shelf areas a narrow relict belt extends from northwest to south at 66 81 m water depths where sediments are characterized by abundant sand and gravel 27 52 and biogenic carbonate 16 44 contents and microscopic examination suggests an older origin the radiocarbon ages of mid and lower sections in cores 3670 10 380 yr bp reflect sedimentation under depositional conditions from early to late holocene in the study area additionally downcore changes of grain size toward coarser grained sediments most probably record global climatic effects with sea level changes specifically the transition from lowstand in early holocene to highstand at mid late holocene the presence of this relict belt in offshore waters can be attributed largely to active uplift tectonics the coarser grained relict belt compared with available seismic profiles corresponds to an lowstand unconformity of bottomset beds of the prograding buyuk menderes delta reconstruction from nautical charts clearly showed the presence of an e w trending submarine canyon paleo buyuk menderes river valley in the course of buyuk menderes graben this is interpreted as product of combination of sea level lowstands and subsidence tectonics throughout the late quaternary smectite 35 62 illite 28 51 and kaolinite 12 19 constitute the dominant clay minerals in the

the active main marmara fault abstract this paper presents selections from and a synthesis of a high resolution bathymetric sparker and deep towed seismic reflection data set recently acquired by the french ifremer r v le suroit in an e w deep trough that forms the northern half of the sea of marmara in nw turkey it includes the first high resolution complete bathymetric map of this area a single throughgoing dextral strike slip fault system which is the western continuation of the northern branch of the north anatolian fault cuts this trough lengthwise and joins the 1999 8 17 kocaeli earthquake fault with the 1912 8 09 arkoy murefte earthquake fault both of which display strike slip offset in its eastern one fourth the structure follows closely the northern margin of the deep trough whereas in the west it hugs its southern margin the eastern one fourth of the structure has a minor component of its displacement distributed across the deep trough owing to a possible original bend in the course of the dextral structure the present course of the north anatolian fault in the sea of marmara originated some 2 105 a ago by cutting across the older basin fabric generated by a dominant nne ssw extension before it began taking up major motion in the pliocene

measurements of two types of dilatational waves in an air filled unconsolidated sand this study consists of laboratory measurements of dilatational waves propagating through an air filled unconsolidated sand one excitation technique consists of a loudspeaker suspended in the air above the packing of sand a second excitation technique uses a mechanical shaker in contact with the sand the transmitted signals are received using microphones and geophones located at various depths within the sand an interpretation based on measured phase speeds indicates that the transmitted energy from the suspended loudspeaker source is partitioned primarily but not exclusively into the type ii dilatational wave this wave attenuates rapidly and is only detected at depths of less than about 15 cm for this particular sample at the deeper depths the detected signal is associated with the type i dilatational wave the mechanical shaker produces only a type i dilatational wave both the geophone and microphone sensors can detect both types of dilatational waves

the sea of marmara a plate boundary sea in an escape tectonic regime abstract the sea of marmara is dissected by two major fault systems the first consists of two east west striking transtensional boundary faults and a number of secondary faults subparallel to them the second is made up of ne sw trending subvertical strike slips and their conjugates oriented nw se that offset the first system these fault systems segment the deep marmara sea into 5 blocks that are either rhomboidal lazy z or wedge shaped three of these blocks may be interpreted as pull apart basins characterized by transtension while the other two sill areas which separate the basins are transpressional push up structures the blocks are subjected to rapid episodic subsidence but they also undergo pervasive vertical motions and possible rotations relative to one another the sedimentary column above the acoustic basement mapped within the sea of marmara can be divided into 3 seismic units a folded and truncated pre transform unit and two syn transform units the lower thick syn transform unit exhibits 3 distinct seismic facies a well stratified basin fill facies cut by subvertical growth faults a push up facies with a contorted or chaotic internal configuration and a slump facies the observed neotectonic and sedimentary regimes result from compressional movement between eurasia and africa which has led to major dextral transform movements along the north anatolian fault zone escape tectonics and from the fact that this fault zone splinters into two overlapping right stepping oblique master faults at the eastern and western border of the sea of marmara respectively

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

modern sedimentation in the n w aegean sea abstract the area under investigation is located within 22 45 to 23 45 e and from 39 15 to 40 15 n sedimentological bathymetric and shallow geophysical data were collected from here during the 7 78 cruise of r r s shackleton twenty seven sea bed surface samples were collected using a day grab from different environments these were analysed for grain size distribution carbonate content and clay mineralogy on the basis of the bathymetric and shallow geophysical data the area has been classified into five major physiographic environments according to their bathymetry and topography 1 shelf thermaicon plateau 2 slope 3 marginal plateau 4 the canyon system and valleys and 5 sporades basin based on the sedimentological analyses the surface sediments have been classified into four major provinces as follows 1 province 1 shelf muds 2 province 2 muddy sands 3 province 3 outer margin muds and 4 province 4 outer shelf shelf break it is concluded that modern sedimentation in the n w aegean sea is dominated by the terrigenous river inputs and by the circulation of both high and low salinity masses

cooling performance and deformation behavior of crushed rock embankments on the qinghai tibet railway in permafrost regions abstract the structural functionality of roads and railways in warm permafrost regions is influenced by both physical and mechanical processes at work within the underlying subgrade this paper uses ten years worth of monitoring data to examine the thermal regimes and deformation behaviors of three different types of crushed rock embankments employed in the construction of the qinghai tibet railway which is located in a warm permafrost region of the tibetan plateau china more specifically the efficiency of u shaped crushed rock crushed rock revetment and crushed rock basement embankments in stabilizing permafrost temperature is evaluated with consideration to the permafrost table ground temperature and mean annual ground temperature then deformation laws in the three embankments were analyzed finally deformation characteristics and sources for general subgrade are discussed and summarized on the basis of monitoring data and previous research results show the permafrost table of each of the three crushed rock embankments to be higher than that of the natural ground at all times and that the underlying permafrost warms with time regardless of the type of embankment employed the deformation characteristics of general subgrade in permafrost regions are determined to be non uniform and persistent furthermore u shaped crushed rock embankment out performed both crushed rock revetment embankment and crushed rock basement embankment in terms of cooling capacity and ability to weaken the sunny shady slope effect these findings stand to provide important guidance for understanding the deformation mechanisms of subgrade in warm permafrost regions as well as for improving qinghai tibet railway embankment quality and operational safety

the paleoclimatic interpretation of clay minerals in sediments a review abstract the application of paleoclimatic interpretation to clay minerals from continental and marine sediments is reviewed and the advantages of this method are indicated levels relatively rich in chlorite illite palygorskite and quartz are interpreted as corresponding to relatively dry periods while more humid periods lead to more intensive weathering and consequently to the dominance of clay minerals more advanced in the relative stability scale such as kaolinite smectite is taken to indicate a climate with contrasting seasons and a pronounced dry season using this and similar schemes the paleoclimates of areas adjoining the mediterranean basin north sea north atlantic southern arctic equatorial and north west pacific and north phillipine sea are reconstructed clay minerals in sediments particularly marine sediments can be useful indicators of paleoclimatic conditions while they do not produce direct indications of climatic parameters they provide integrated records of overall climatic impact occasionally they may be superior to the more conventional paleoclimatic methods such as pollen or oxygen isotope analysis the limitations imposed on the paleoclimatic interpretation of clay minerals in sediments are discussed on the basis of examples the distinction between authigenic and detrital clay minerals is shown to be problematic particularly with regard to smectite the relationship between climatic parameters and clay mineral formation is complicated by the intervention of extra climatic factors such as topography geomorphology lithology and time post depositional diagenetic changes may not be recognized differentiation during transport due to size sorting or differential flocculation may overlap climate induced differentiation the association of clay mineral assemblages with specific source areas presents difficulties due to dispersal pathways that are affected by type of transport agency i e water ice or wind transport agencies are not constant with time by an interdisciplinary approach with the paleoclimatic information derived from clay minerals being correlated with that obtained from the analysis of microfossils and oxygen isotope data many of these limitations can be overcome

submarine fault scarps in the sea of marmara pull apart north anatolian fault implications for seismic hazard in istanbul earthquake scarps associated with recent historical events have been found on the floor of the sea of marmara along the north anatolian fault naf the marmarascarps cruise using an unmanned submersible rov provides direct observations to study the fine scale morphology and geology of those scarps their distribution and geometry the observations are consistent with the diversity of fault mechanisms and the fault segmentation within the north marmara extensional step over between the strike slip ganos and izmit faults smaller strike slip segments and pull apart basins alternate within the main step over commonly combining strike slip and extension rapid sedimentation rates of 1 3 mm yr appear to compete with normal faulting components of up to 6 mm yr at the pull apart margins in spite of the fast sedimentation rates the submarine scarps are preserved and accumulate relief sets of youthful earthquake scarps extend offshore from the ganos and izmit faults on land into the sea of marmara our observations suggest that they correspond to the submarine ruptures of the 1999 izmit mw 7 4 and the 1912 ganos ms 7 4 earthquakes while the 1999 rupture ends at the immediate eastern entrance of the extensional cinarcik basin the 1912 rupture appears to have crossed the ganos restraining bend into the sea of marmara floor for 60 km with a right lateral slip of 5 m ending in the central basin step over from the gulf of saros to marmara the total 1912 rupture length is probably about 140 km not 50 km as previously thought the direct observations of submarine scarps in marmara are critical to defining barriers that have arrested past earthquakes as well as defining a possible segmentation of the contemporary state of loading incorporating the submarine scarp evidence modifies substantially our understanding of the current state of loading along the naf next to istanbul coulomb stress modeling shows a zone of maximum loading with at least 4 5 m of slip deficit encompassing the strike slip segment 70 km long between the cinarcik and central basins that segment alone would be capable of generating a large magnitude earthquake mw 7 2 other segments in marmara appear less loaded

paleoenvironments of the marmara sea turkey coasts from paleontological and sedimentological data abstract the faunal composition of upper pleistocene holocene sedimentary sections was investigated from several boreholes in the coastal areas of the northern and eastern marmara sea the boreholes penetrated to pre quaternary basement and contain sediments deposited in near shore environments such as lagoons estuaries and deltas during the post glacial transgression rapidly rising sea level drowned these littoral areas progressively transforming into their present form over the last 9 5 10 ka bp uncalib thus the lower kucukcekmece valley became a lagoon while the golden horn became an estuary on the northeast coast the kurbagali delta was submerged when the rate of sea level rise decreased at about 5000 6000 years ago the influence of mediterranean water on the faunal assemblage was surpassed by salinity tolerant forms probably due to increased freshwater and sediment input on land

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

morphotectonic development of the marmara region abstract the marmara region of northwest turkey covers the marmara sea basin and the surrounding lands in the region morphologically different areas may be distinguished the marmara sea basin is a structural depression the land to the north is known as the thrace kocaeli peneplain a flatland elevated above a horst this may be referred to as the istanbul horst bounded by two strike slip fault zones which define the structural boundaries of two sea basins the black sea in the north and the marmara sea in the south the southern boundary fault is part of the north anatolian transform fault zone nafz which cuts through the region in the e w direction and extends to the aegean sea region the land to the south of the marmara sea is a plateau about 300 to 800 m high known as the bursa balikesir plateau it has a rather rugged topography represented by nw and ne trending ridges separated by depressions the ridges and the depressions correspond to horsts and grabens respectively the data reveal that the marmara region has passed through the following morphotectonic evolution together with the surrounding region it suffered a long period of denudation between the oligocene and the end of the late miocene which formed a regionwide peneplain the n s extensional regime followed this phase and began to produce a horst graben system and thus fragmented the peneplain the flat lying erosional surfaces have been elevated above the horsts later the nafz reached the marmara region in the initial stage it affected nw anatolia extensively as a wide right lateral shear regime this has evolved and through time the present narrow fault zone has developed the major morphological difference between the regions to the north and the south of the marmara sea basin is mainly related to the nafz as a plate boundary it formed a barrier to the n s extension saving the northern sector from the effect of the extension the southern region has gradually elevated to much higher altitudes

sea level changes and depositional environments in the izmit gulf eastern marmara sea during the late glacial holocene period abstract offshore and onshore stratigraphic studies together with high resolution shallow seismic reflection profiling and multibeam bathymetric mapping were carried out in the western and central part of the izmit gulf these studies indicate that the izmit gulf was a lacustrine environment as part of the marmara lake during the late glaciation and early deglaciation until 12 kyr bp when the marmara basin was inundated by the mediterranean waters correlation of 14 c dated onshore and offshore stratigraphic units in the western izmit gulf indicates that generally coarse late glacial sediments overlie a marked erosional surface formed during the low water level of the marmara lake these coarse sediments are succeeded by 10 4 7 kyr bp old transgressive and by late holocene post transgression mud units the bathymetry and sub bottom chirp profiles clearly show that the paleoshoreline of the gulf was located at 85 m having been controlled by the bedrock sill depth of the canakkale strait another paleoshoreline observed at 65 m on the northern margin of the western izmit and karamursel basins was probably formed during the younger dryas sea level stillstand the shelf areas during this time were colonized by bioherms which were subsequently drowned and disappeared after a further rise of the sea level the presence of a 65 m marine paleoshoreline in the karamursel basin indicates that the sill restricting this basin to the west was much deeper than its present 55 m level and was located further south the golcuk basin restricted by a 38 m sill to its west was probably not flooded by marine waters until 9 kyr bp

the holocene sea level story since 7500 bp lessons from the eastern mediterranean the black and the azov seas abstract this paper addresses the obvious controversy between the so far published sea level curves of the black sea and the mediterranean it starts with a discussion of the methods of reconstructing sea level curves the evaluation of sea level indicators and the application of the radiocarbon dating method at least since 7500 bp when the black sea and the mediterranean were connected both water bodies must have reacted synchronously on glacio eustatic changes it is documented that none of the mediterranean sea level curves shows the major wiggles postulated for the black sea which are supposed to reflect trans and regression cycles the very shallow bathymetric condition of the azov sea and the northern black sea should have led to considerable and traceable shoreline displacements there is neither archaeological nor historical evidence of mid and late holocene regressions of several meters the tectonic setting of the black and azov seas implicates that the tectonic signal often overrides the eustatic one therefore only local sea level curves can be established in this paper based on vibracores a locally valid sea level curve for the taman peninsula is demonstrated layers of paralic peat were used as sea level indicators and for 14 c dating the shape of this curve follows the one known from the mediterranean this study also revealed that the present peninsula of taman evolved out of a former archipelago

composition of clays along the continental shelf off israel contribution of the nile versus local sources the eastern mediterranean sedimentary regime is dominated by sediment transport from the nile river and its delta but recent studies have also suggested a certain contribution of clay fraction from streams to the continental shelf and slope off israel in the present study we focused on clay fraction deposition along the inner 40 1000 m water depth shelf of israel in order to substantiate and quantify its different sources for this purpose detailed xrd mineralogical determinations as well as chemical compositions of the clay 2 m fraction of marine and continental sediments were used the clay mineral composition of israeli stream sediments is variable with no distinct spatial or temporal trend but within a limited assemblage this clay assemblage is made up of illite smectite is phases 70 90 kaolinite 5 25 and illite 10 and is similar to that of the nile however it is clearly distinguished by the type of the is phases which are derived mainly from mesozoic outcrops and recent sediments soils and are less expandable than those of the nile which are derived mainly from weathered basalt the nile derived component is depleted in the marine clay fraction along the israel coast evidenced by a decrease of is expandability and the fe2o3 al2o3 ratio and an increase in the k2o al2o3 mgo al2o3 and cao al2o3 ratios the depletion is well pronounced north of tel aviv where the largest coastal plain stream flows to the sea a northward increase of carbonates in the clay fraction and particularly of the bioskeletal component is indicated by the ratios of mgo and sr to cao the contribution of the local streams to the shallow shelf marine clay fraction is estimated to be about 50 a minor contribution of desert dust is identified by the relative increase in kaolinite in the marine sediments south of tel aviv

clay mineral distribution in surface sediments of the south atlantic sources transport and relation to oceanography abstract surface samples mostly from abyssal sediments of the south atlantic from parts of the equatorial atlantic and of the antarctic ocean were investigated for clay content and clay mineral composition maps of relative clay mineral content were compiled which improve previous maps by showing more details especially at high latitudes large scale relations regarding the origin and transport paths of detrital clay are revealed high smectite concentrations are observed in abyssal regions primarily derived from southernmost south america and from minor sources in southwest africa near submarine volcanoes of the antarctic ocean south sandwich bouvet island smectite contents exhibit distinct maxima which is ascribed to the weathering of altered basalts and volcanic glasses the illite distribution can be subdivided into five major zones including two maxima revealing both south african and antarctic sources a particularly high amount of mg and fe rich illites are observed close to east antarctica they are derived from biotite bearing crystalline rocks and transported to the west by the east antarctic coastal current chiorite and well crystallized dioctaedral illite are typical minerals enriched within the subantarctic and polarfrontal zone but of minor importance off east antarctica kaolinite dominates the clay mineral assemblage at low latitudes where the continental source rocks west africa brazil are mainly affected by intensive chemical weathering surprisingly a slight increase of kaolinite is observed in the enderby basin and near the filchner ronne ice shelf the investigated area can be subdivided into ten large scale clay facies zones with characteristic possible source regions and transport paths clay mineral assemblages of the largest part of the south atlantic especially of the western basins are dominated by chlorite and illite derived from the antarctic peninsula and southernmost south america and supported by advection within the circumantarctic deep water flow in contrast the east antarctic provinces are relatively small assemblages of the eastern basins north of 30 s are strongly influenced by african sources controlled by weathering regimes on land and by a complex interaction of wind river and deep ocean transport the strong gradient in clay mineral composition at the brazilian slope indicate a relatively low contribution of tropically derived assemblages to the western basins

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

modeling of hydraulically controlled exchange flow in the bosphorus strait abstract recent hydrographic observations obtained in the bosphorus strait illustrate several features of the flow that may be related with the internal hydraulics a two layer numerical model indicates that the two way exchange flow may indeed be subject to a series of internal hydraulic adjustments along the strait due to morphological features such as sills a contraction and abrupt expansion of the width of the strait the model identifies three distinct regions of the supercritical flow the lower layer flow of the marmara sea origin is directed to the north towards the black sea in a progressively thinning layer and is controlled by the sill located near the black sea entrance of the strait the upper layer water of the black sea origin flows in the opposite direction and is controlled upon reaching the constricted region located about 10 12 km away from the marmara end of the strait the upper layer flow is then matched to the subsequent subcritical conditions by undergoing an internal hydraulic ju

intra basinal water movements induced by faulting the august 17 1999 golcuk izmit bay earthquake m w 7 4 abstract a strong earthquake m w 7 4 occurred near the town of golcuk izmit bay western turkey at 00 01 gmt on august 17 1999 izmit bay is a e w trending pull apart basin with a surface area of about 300 km 2 along the north anatolian fault zone naf in the eastern extension of the sea of marmara the earthquake was caused by a westerly movement of the anatolian plate along naf and was accompanied by isolated chaotic water movements along the northern and southern shores of the bay at localities along the shoreline a sudden drop in sea level and a subsequent rise was prominent the mode of observed sea level movements rules out the occurrence of a basin wide tsunami sensu stricto instead the water movements are attributed to localized sudden dip slip movements of fault blocks in this pull apart basin

remedying embankment thaw settlement in a warm permafrost region with thermosyphons and crushed rock revetment due to the special engineering geology characteristics of permafrost construction in permafrost regions tends to result in serious permafrost related engineering problems thaw settlement induced by permafrost degradation is the principal challenge for railway construction on the qinghai tibetan plateau it threatens the stability and safety of the railway system especially in warm and ice rich permafrost regions thaw settlement in section dk1139 780 along the qinghai tibetan railway is a potential risk to the safety of the railway and a combination of closed thermosyphons and crushed rock revetment was used to remedy permafrost warming and thaw settlement of the embankment based on ground temperatures and embankment deformations observed at this site since 2002 the effects of the remedial measures were evaluated the results show that the remedial measures lowered the ground temperature and raised the permafrost table the crushed rock slope protection acted as an insulation layer and reduced heat

active faults and evolving strike slip basins in the marmara sea northwest turkey a multichannel seismic reflection study abstract the north anatolian fault is a 1200 km long transform fault forming the boundary between the anatolian and eurasian plates near its western end it strikes through the marmara sea and is responsible for the creation of three deep marine depressions the north anatolian fault system and the linked basins in the eastern marmara sea were studied using newly acquired multi channel seismic reflection data in the marmara sea the north anatolian fault consists of a main strand and a few subsidiary branches the main strand is made up of the ganos 15 km long central marmara 105 km and north boundary 45 km fault segments the north boundary fault joins in the east to the izmit segment which was ruptured during the m s 7 4 earthquake on 17 8 1999 the north boundary fault is highly oblique to the regional displacement vector which results in the generation of a symmetrical fault wedge basin this cinarcik basin is a wedge shaped deep marine depression south of istanbul it is about 50 km long up to 20 km wide and 1250 m deep and is filled with pliocene to quaternary sediments over 3 km thick the north boundary fault joins in the west to the transpressional central marmara fault around the restraining segment boundary the syntransform sediments are being deformed into a large anticlinorium the cinarcik basin started to form when the westward propagating north anatolian fault intersected a northwest trending pre existing fault zone during the pliocene and bifurcated into nw and sw trending segments forming a transform transform transform type triple junction dextral strike slip movement along the arms of the triple junction led to the development of the cinarcik basin the present fault geometry in the marmara region was achieved later during the mid pliocene following the termination of the triple junction geometry south of the main north anatolian fault system there is a second active strike slip fault in the marmara sea made up of several segments a highly asymmetrical fault bend basin comprising pliocene quaternary sediments over 2 5 km thick is forming along a releasing fault segment of this south boundary fault system

analysis of frost heave mechanisms in a high speed railway embankment the harbin dalian high speed railway in northeastern china has a significant portion of track foundation built on seasonally frozen ground wide spread frost heave was observed during the first win

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