middle pleistocene bivalves of the iznik lake basin eastern marmara nw turkey and a new paleobiogeographical approach iznik lake is a tectonically originated basin mainly controlled by the e w trending middle strand of the north anatolian fault naf system pleistocene sediments occurring in front of the faults are well exposed both in the northern and in the southern shorelines of the basin in this study two endemic brackish water bivalve species didacna subpyramidata pravoslavkev 1939 and didacna nov sp were found in the oldest terrace of the northern pleistocene sequence having characterized morphology these species serve as stratigraphic indicators in the regional pleistocene stratigraphy of the ponto caspian region and thus are well correlated to the assemblages of the early khazarian subhorizon middle pleistocene hence these data demonstrate that the early khazarian brackish water sea covered the study area additionally a model for the formation of the basin is proposed the iznik lake basin was a gulf of the former marmara sea in the early khazarian connecting the marmara to the black sea and the caspian sea the subsequent regional prograding uplifts main dextral strike slip fault and many normal faults of the naf zone cut off the marine connections to the basin leading to its present location and topographic level

sequence stratigraphy tectonics and depositional history in eastern thrace basin nw turkey abstract the eastern thrace basin forms the eastern portion of the turkish thrace basin in nw turkey the pre tertiary crystalline basement shows platform and deep basin depositional morphology which results in facies pattern and thickness distribution localization during the early stages of basin development in middle to late eocene time normal fault controlled early and lateral reverse fault controlled later stage tectonic events characterize basin geometry and the present topography respectively the early stage normal faulting caused subsidence and sediment accumulation in the late eocene and early oligocene while later stage tectonic events caused intense deformation and structuration in the early to middle miocene as a result southeastern and northern regions were folded or uplifted and deeply eroded outcrop well log core and reflection seismic studies reveal that the sedimentary succession can be subdivided into five characteristic depositional sequences bounded at their base by unconformities these unconformities were dated using paleontological data the sequence boundaries underlying consecutively sequences 1 2 3 and 5 were dated at 39 5 36 30 and 25 5 ma from older to young in order of succession corresponding to the major erosional breaks between the middle and upper eocene the upper eocene and the lower oligocene the lower and upper oligocene and the upper oligocene and the lower miocene the sequence boundary underlying sequence 4 was determined to lie within the late oligocene succession and as an age designation could not be assigned it was termed intra sequence boundary isb the first two sequences correspond to relative sea level rises and a normal fault controlled tectonism coincides with them reefal carbonates coarse grained clastics and marine shales with abundant volcanic flows or layers represent the sedimentary facies of these two early sequences the third and fourth sequences correspond to either a decreased relative rise of sea level or a relative still stand of sea level and a sediment induced subsidence related to thermal relaxation provides accommodation prograding delta sediments of varying extent constitute the sedimentary packages of these two sequences the depositional sequence 5 which makes up the uppermost part of the sedimentary succession in the basin corresponds to a relative sea level fall and a tectonic style shaped by lateral and inversion faulting characterizes this period nonmarine alluvial fan fluvial channel and various lagoonal deposits constitute the sedimentary facies of this last sequence porous reefal limestones and shallow marine beach sandstones of sequence 1 and deltaic sandstones of sequences 3 and 4 provide good reservoir rocks for the hydrocarbons produced in the study area the marine shales and marls of the second and the third sequences provide good source rocks as they are rich in disseminated organic matter content although the non marine alluvial and fluvial channel deposits of sequence 5 are good reservoirs they lack effective seals the time interval in which sequence 5 was deposited represents a period of major structural and trap development in the basin

estimating the oxygen isotopic composition of equatorial precipitation during the mid cretaceous abstract recent studies utilize the oxygen isotopic composition of pedogenic carbonates siderite and calcite to evaluate empirically the global hydrologic cycle during the cretaceous pedogenic carbonates are used as a proxy for the isotopic composition of meteoric waters in order to estimate precipitation rates in the aptian albian via a mass balance model these modeling studies have previously been limited to mid latitude to high latitude data and thus a more extensive latitudinal data set is needed to produce a more globally constrained model this study provides an equatorial 2 s paleolatitude data set from pedogenic sphaerosiderites of the caballos formation from the upper magdalena valley colombia in addition macroscopic and microscopic morphological features of paleosols were used to identify ancient soil conditions the gleyed appearance and presence of sphaerosiderites suggest that soils were dominated by water saturated conditions with occasional incursions of marine influenced water resulting in pyrite precipitation this observation constrains the sampling sites to paleoelevations near sea level paleosols are interpreted to have been entisols inceptisols and ultisols similar to soils in coastal equatorial regions of modern colombia relatively invariant 18o values and more variable 13c values produce vertical trends in 13c vs 18o space called meteoric sphaerosiderite lines the average oxygen isotopic composition for these trends is 4 41 0 37 vpdb the average oxygen isotopic composition of meteoric waters precipitating the sphaerosiderites is estimated at 4 56 0 38 vsmow these are slightly more enriched than modern and modeled cretaceous estimates of equatorial precipitation 18o but are generally in agreement with expected oxygen isotopic compositions of precipitation for this paleolatitude

conditions and timescales for welding block and ash flow deposits welding of pyroclastic deposits to reform a coherent rock mass is a common phenomenon especially for pumiceous pyroclastic density current deposits i e ignimbrites however and despite the pervasive abundance of block and ash flow baf deposits in the geological and modern record instances of strongly welded baf deposits are few here we present a series of high temperature 800 900 c compaction experiments designed to map the conditions deposit thickness stress and temperature viscosity and timescales that permit or inhibit the welding of baf deposits our experiments were performed on unconsolidated aggregates containing an ash and lapilli component derived from crushed and sieved lava blocks containing 25 crystals taken from the well documented welded baf deposit at mount meager volcano british columbia canada the experiments demonstrate that welding efficiency increases with increasing time and temperature progressive welding is expressed by increasing axial strain porosity loss and bulk density the rate of change of each of these physical properties reduces as welding progresses microstructural analysis of the experimental products shows that the loss of interclast porosity during welding results from the progressive sintering and amalgamation of vitric fragments and that the pore shape changes from sub equant pores to stretched lenses sandwiched between vitric and crystal fragments the coincidence between the microstructure and rock physical properties of the natural and experimental samples highlight that we have successfully reproduced welded baf in the laboratory furthermore our permeability measurements highlight a hysteresis in the return journey of the there and back again volcanic permeability cycle expressed by an increase in permeability due to vesiculation and fragmentation followed by a decrease due to welding this hysteresis cannot be described by a single porosity permeability power law relationship and reflects the change in pore shape and connectivity during welding finally we show that a simple model for welding can accurately forecast the welding timescales of the baf deposit at mount meager as reconstructed from the collapse of the lillooet river valley dam using our experimental data we use this validation as a platform to provide a universal window for the welding of baf deposits also applicable for comparable welded deposits e g welded autobreccias in block lavas and lava domes for a broad range of deposit thickness or stress and effective viscosity

coal characteristics palynology and palaeoenvironmental interpretation of the yenikoy coal of late oligocene age in the thrace basin nw turkey abstract the yenikoy coal field is located in a narrow area between the black sea coast and the istranca standrja mountain in the thrace basin the aims of this study are to characterize coal petrographical mineralogical palynological geochemical and sedimentological properties of the yenikoy coal deposit and to reconstruct palaeoenvironmental conditions during peat accumulation a total of 9 coal samples collected from the coal seam section are almost entirely composed of xylite rich lithotype and are characterized by low ash yield 7 9 21 1 average 13 6 on dry basis and high total s contents 1 0 3 7 average 2 2 on dry basis the macroscopic features maceral composition and coal facies suggest that the peat was accumulated under mesotrophic anoxic conditions and the peat forming vegetation consisted mainly of arboreal species e g cupressaceae ulmus carya zelkova alnus pterocarya and quercus the low hi values of the analysed samples are presumably related to presence of xylite rich lithotype rather than the dominance of herbaceous plant and or low preservation of organic matter in the palaeomire even though relatively b enrichments high total s contents and weak anomalies of some rey e g y ce and gd in the analysed samples could refer possible sea water influence into palaeomire in the study area during late oligocene the sedimentological and palynological freshwater algaes pediastrum spirogyra and mougeotia data that indicate the palaeomire was located within a delta plain environment where small freshwater lakes and or ponds developed the statistical analysis and sem edx data show the vast majority of elements in the analysed coal samples have inorganic affinity the major elements al k and enriched elements like b v cr hg and u seem to be affiliated with aluminosilicate minerals whereas fe ni and as have probably sulphide affinity the detrital presences of apatite crystals as detected by sem edx analysis indicate that rey have mainly phosphate affinity in the analysed samples vertical distributions of the elements and ash yields suggest that the detrital input ratio was changeable and controlled some elemental enrichment during peat accumulation these variations could be related to development of and fluvial conditions in the study area which interrupted peat accumulation several times during late oligocene

welding insights from high temperature analogue experiments abstract the rheological behavior of pyroclastic deposits during welding is incompletely understood and is based on a surprisingly small number of experimental studies here we present results from a new experimental apparatus comprising an automated uniaxial compression load frame that can run constant load up to 1150 kg or constant displacement rate 10 6 to 0 25 cm s tests at elevated temperatures 1100 c deformation experiments were performed on pre fabricated cylinders 4 5 cm diameter 6 cm length of soda lime silica glass beads n 32 sintered rhyolite ash n 7 and cores of pumiceous rhyodacite n 6 experimental runs used strain rates from 10 5 to 10 3 s 1 and stresses of 0 to 5 24 mpa temperatures varied from 535 to 650 c for experiments on soda lime silica glass beads and 825 to 950 c for natural materials in all cases experimental cores showed a strain dependent rheology that is more strongly affected by temperature than by load or strain rate results from these experiments are used to develop a relationship in which the effective viscosity e of the experimental cores is predicted by e o exp 5 3 f 1 f where 0 is melt viscosity and f is sample porosity this rheological model provides a means for exploring the relative roles of emplacement temperature load and glass transition temperature in welding of pyroclastic deposits

the thrace basin and the black sea the eocene oligocene marine connection the late cretaceous recent west black sea basin and the eocene oligocene thrace basin are separated by the strandja arch comprising metamorphic and magmatic rocks since late cretaceous time the strandja arch formed a palaeo high separating the two basins which accumulated clastic sediment of 9 km thickness during late eocene early oligocene time the marine connection between these basins existed through the catalca gap west of istanbul the catalca gap lies on the damage zone of a major cretaceous strike slip fault it formed a 15 km wide marine gateway where carbonate rich sediments of thickness c 350 m were deposited the sequence consists of upper eocene shallow marine limestones sbz18 20 overlain by upper eocene lower oligocene p16 p19 zones pelagic marl with a rich fauna of planktonic foraminifera the marls are intercalated with 31 32 ma acidic tuff and calc arenite beds the catalca gap is bounded in the west by a major normal fault which marks the eastern boundary of the thrace basin seismic reflection profiles well data and zircon u pb ages indicate that the thrace basin sequence west of the fault is late eocene middle oligocene 37 27 ma in age and that the fault has accommodated 2 km of subsidence although there was a marine connection between the west black sea and thrace basins during late eocene early oligocene time no significant exchange of clastic sediment took place sedimentation in the catalca gap ended abruptly during early oligocene time by uplift and this eventually led to the paralic conditions in the thrace basin

voluminous lava like precursor to a major ash flow tuff low column pyroclastic eruption of the pagosa peak dacite san juan volcanic field colorado abstract the pagosa peak dacite is an unusual pyroclastic deposit that immediately predated eruption of the enormous fish canyon tuff 5000 km3 from the la garita caldera at 28 ma the pagosa peak dacite is thick to 1 km voluminous 200 km3 and has a high aspect ratio 1 50 similar to those of silicic lava flows it contains a high proportion 40 60 of juvenile clasts to 3 4 m emplaced as viscous magma that was less vesiculated than typical pumice accidental lithic fragments are absent above the basal 5 10 of the unit thick densely welded proximal deposits flowed rheomorphically due to gravitational spreading despite the very high viscosity of the crystal rich magma resulting in a macroscopic appearance similar to flow layered silicic lava although it is a separate depositional unit the pagosa peak dacite is indistinguishable from the overlying fish canyon tuff in bulk rock chemistry phenocryst compositions and 40ar 39ar age the unusual characteristics of this deposit are interpreted as consequences of eruption by low column pyroclastic fountaining and lateral transport as dense poorly inflated pyroclastic flows the inferred eruptive style may be in part related to synchronous disruption of the southern margin of the fish canyon magma chamber by block faulting the pagosa peak eruptive sources are apparently buried in the southern la garita caldera where northerly extensions of observed syneruptive faults served as fissure vents cumulative vent cross sections were large leading to relatively low emission velocities for a given discharge rate many successive pyroclastic flows accumulated sufficiently rapidly to weld densely as a cooling unit up to 1000 m thick and to retain heat adequately to permit rheomorphic flow explosive potential of the magma may have been reduced by degassing during ascent through fissure conduits leading to fracture dominated magma fragmentation at low vesicularity subsequent collapse of the 75 35 km 2 la garita caldera and eruption of the fish canyon tuff were probably triggered by destabilization of the chamber roof as magma was withdrawn during the pagosa peak eruption

volcanic sintering timescales of viscous densification and strength recovery 1 sintering and densification are ubiquitous processes influencing the emplacement of both effusive and explosive products of volcanic eruptions here we sinter ash size fragments of a synthetic national institute of standards and technology viscosity standard glass at temperatures at which the resultant melt has a viscosity of 108 109 pa s at 1bar to assess sintering dynamics under near surface volcanic conditions we track the strength recovery via uniaxial compressive tests we observe that volcanic ash sintering is dominantly time dependent temperature dependent and grain size dependent and may thus be interpreted to be controlled by melt viscosity and surface tension sintering evolves from particle agglutination to viscous pore collapse and is accompanied by a reduction in connected porosity and an increase in isolated pores sintering and densification result in a nonlinear increase in strength micromechanical modeling shows that the pore emanated crack model explains the strength of porous lava as a function of pore fraction and size

experimental and textural investigation of welding effects of compaction sintering and vapor phase crystallization in the rhyolitic rattlesnake tuff abstract the abrupt changes in character of variably welded pyroclastic deposits have invited decades of investigation and classification we conducted two series of experiments using ash from the nonwelded base of the rhyolitic rattlesnake tuff of oregon usa to examine conditions of welding one series of experiments was conducted at atmospheric pressure 1 at in a muffle furnace with variable run times and temperature and another series was conducted at 5 mpa and 600 c in a cold seal apparatus with variable run times and water contents we compared the results to a suite of incipiently to densely welded natural samples of the rattlesnake tuff experiments at 1 at required a temperature above 900 c to produce welding which is in excess of the estimated pre eruptive magmatic temperature of the tuff the experiments also yielded globular clast textures unlike the natural tuff during the cold seal experiments the gold sample capsules collapsed in response to sample densification textures and densities that closely mimic the natural suite were produced at 5 mpa 600 c and 0 4 wt h2o over run durations of hours to 2 days clast deformation and development of foliation in 2 week runs were greater than in natural samples both more and less water reduced the degree of welding at otherwise constant run conditions for 5 mpa experiments changes in the degree of foliation of shards and of axial ratios of bubble shards and non bubble mainly platy shards are consistent with early densification related to compaction and partial rotation of shards into a foliation subsequent densification was associated with viscous deformation as indicated by more sintered contacts and deformation of shards sintering local fusion of shard shard contacts was increasingly important with longer run times higher temperatures and greater pressures during runs with high water concentrations sintering was rare and adhesion between clasts was dominated by precipitation of sublimates in pore spaces a few tenths wt h2o in the rhyolite glass promote the development of welding by sharp reduction of glass viscosity large amounts of water inhibit welding by creating surface sublimates that interfere with sintering and may exert fluid pressure counter to lithostatic load if sintering and vapor phase sublimates seal permeability in the tuff

fission track evidence for late oligocene and mid miocene activity along the north anatolian fault in south western thrace apatite fission track ft analyses of sandstone samples collected across the trace of the ganos segment of the north anatolian fault naf in south western thrace turkey indicate that a significant structural discontinuity was in existence at least by the latest oligocene such discontinuity had a complex kinematic history as exhumation south of it occurred during the latest oligocene and north of it during the mid miocene our data imply that early pliocene westward propagation of the naf in the marmara region followed a pre existing structural discontinuity such discontinuity could be related to the development of the intra pontide suture marking the terminal closure of the intra pontide ocean during the oligocene

the 1984 nuee ardente deposits of merapi volcano central java indonesia stratigraphy textural characteristics and transport mechanisms for many centuries merapi volcano has generated hot avalanches of blocks lapilli and ashes derived from the destruction of partially solidified viscous lava domes merapi type nuees ardentes on 15 june 1984 at least four nuees ardentes came down the southwest slope of the merapi the first and the last being responsible for more than 99 of the deposits which are now exposed the first nuee ardente a merapi type nuee ardente was produced by the destruction of the dome travelled 7 km from the crater leaving a measured deposit 2 7 m thick 4 km from the crater near its upper depositional limit regularly increasing to a maximum measured thickness of 12 m at the front of the deposit the lower contact is sharp non erosive with pines still rooted in the underlying paleosol the deposit consists of 50 ash 33 lapilli and 17 blocks with two subpopulations one rosin and one normal and is finespoor with less than 4 of fine ash d finer than 4 the deposit displays reverse population grading of both vesiculated and massive clasts and of the maximum grain size the maximum size significantly increases regularly down current over most of the exposed length of unit 1 and bed thickness increases for the entire length of the deposit the deposit of the second nuee ardente is only 6 21 cm thick and of very limited lateral extent it is a normally graded coarse to fine ash with a finespoor base the third unit consists of fines poor normally graded coarse ash exposed in low amplitude 20 40 cm 12 m wavelength dunes the deposit of the fourth nuee ardente rests in sharp erosive contact on the underlying unit increasing in thickness down flow it consists of transitional coarse and fine grained strata 6 130 c cm thick dipping 5 10 down flow the deposit made up of two subpopulations one rosin and one normal is normally graded over the entire bed but coarsegrained strata are reversely graded the relative content of vesiculated clasts increases up bed in both strata types from 12 at the base to 40 at the top the characteristics of unit 1 suggest that it accumulated from a concentrated suspension of cohesionless solids exhibiting non newtonian behavior where dispersive pressure played an important role in the suspension of the clasts units 2 and 3 were probably deposited from dilute turbulent suspensions whereas the upper unit 4 is a classic example of deposition from a high density turbulent suspension leading to the formation of multiple traction carpets driven by the overlying lower density surge the horizontal distance travelled by a hot rock avalanche may be influenced by its transport mechanism debris flows are mobile on very low slopes as low as 1 whereas grain flows even density modified grain flows require relatively high slopes more than 6 at merapi to maintain their mobility if the present merapi dome were to collapse and produce a debris flow its present volume coupled with the minimal 1 5 km vertical drop could travel a distance ranging between 15 and 30 km however if transport were by grain flow mechanisms the mass could come to rest as it reaches a 5 10 slope

nuees ardentes of 22 november 1994 at merapi volcano java indonesia nuees ardentes associated with dome collapse on 22 november 1994 at merapi volcano traveled to the south southwest as far as 6 5 km and collectively accumulated roughly 2 5 3 million cubic meters of deposits the damaged area comprises 9 5 km2 and is covered by two nuee ardente facies a conventional merapi type valley fill block and ash flow facies and a pyroclastic surge facies the proximal deposits reflect the accumulation of dozens of nuees ardentes with many subsidiary flow units the distal deposits are more simply organized as only a few individual events reached to distances 3 5 km the stratigraphic relationships north of turgo hill indicate that the surge deposits are a facies of particularly mobile nuees ardentes that also deposited channeled block and ash flow facies they further suggest that the surge facies beyond the channel margins correlate laterally with a finer grained sublayer locally developed at the base of the block and ash flow facies eyewitness reports suggest that the emplacement of the block and ash flow facies in the distal part of the boyong river may have followed by a short time interval the destruction and deposition of the surge facies at turgo village the stratigraphy is in accord with the eyewitness reports the surge facies was emplaced by a dilute surge current detached from the same dome collapse nuee ardente that as a separate flow unit subsequently emplaced the distal block and ash deposit in the boyong valley the detachment occurred at higher elevations likely at or above the slope break at about 2000 m elevation this flow separation enabled the surge current to shortcut over the landscape and to emplace its deposit even as the block and ash flow continued its tortuous southward movement in the boyong channel dome collapse nuee ardente activity formed the bulk of the eruption which was accompanied by virtually no significant vertical summit explosive activity

in situ formation of welded tuff like textures in the carapace of a voluminous silicic lava flow owyhee county sw idaho the badlands rhyolite on the owyhee plateau of southwestern idaho can be demonstrated to be a large lava flow on the basis of its geometry of large and small flow lobes its well exposed near vent features and its response to pre existing topography however samples of the dense upper vitrophyre of the unit reveal a range of annealed fragmental textures including material which closely resembles the compressed welded glass shards which are characteristic of ignimbrites formation of these tuff like textures involved processes probably common to emplacement of most silicic lava flow units decompression upon extrusion causes inflation of pumice at the surface of the lava flow some of this pumice is subsequently comminuted producing loose bubble wall shards bits of pumice chips of dense glass and fragments of phenocrysts this debris sifts down around loose blocks and into open fractures deeper in the flow where it can be reheated compressed and annealed to varying degrees the end result is a dense vitrophyre layer beneath the true upper non welded carapace breccia which can be extremely texturally heterogeneous with areas of flow foliated lava occurring very near lava which in many aspects looks like welded ignimbrite complete with flattened pumices identical textures in other silicic units have been cited by previous workers as evidence that those units erupted as pyroclastic flows which then underwent sufficient rheomorphism to create a flow foliated rock which otherwise appears to be lava the textures described herein indicate that lava flows can come to mimic rheomorphic ignimbrites at least at scales ranging from thin sections to outcrops voluminous silicic units with scattered fragmental textures but with otherwise lava like features are probably true effusive lava flows

mt pelee martinique may 8 and 20 1902 pyroclastic flows and surges abstract the distribution stratigraphic relationships and fragmental components of the may 8 and 20 1902 pyroclastic flows from mt pelee martinique together with eyewitness accounts suggest the following explanation for those eruptions the eruptions were vertically directed magmatic perhaps initiated phreatically and contained abundant juvenile lithics from congealed magma of the dome and neck this resulted in a two part eruption column having 1 a dense lithic charged part which collapsed into the crater and flowed out of a pre existing notch in its side giving rise to pyrochlastic flows and 2 a magmatically derived column containing gases juvenile vitric material and crystals which largely by passed the neck and dome and escaped into the atmosphere all of the energy of the flows was apparently focused through the notch they emerged fully turbulent and flowed down riviere blanche gravity segregation of large and abundant fragments soon resulted in a dense high concentration poorly fluidized block and ash flow confined to the valley leaving above a fully turbulent high energy ash cloud surge as the ash cloud surge moved down the mountain it continued to expand outward the process of gravity segregation continued as the ash cloud surge expanded resulting in secondary block and ash underflows toward st pierre the secondary block and ash flows developed on a gently sloping upland surface 100 m or more above the valley of riviere blanche the turbulent fragment depleted surges above the secondary block and ash flows maintained sufficient energy to devastate the landscape outward to about 3000 m including st pierre the surges refracted around obstacles and in one place moved up a small valley in a direction opposite to the main flows

a fore arc origin for the thrace basin nw turkey hydrocarbon bearing thrace basin occupies much of the european part of turkey the middle eocene to oligocene sequence in the centre of the basin exceeds 9 km in thickness based on the stratigraphy structure and the regional context of this basin we propose that it developed as a fore arc basin between the medial eocene and the oligocene above the northward subducting intra pontide ocean its post miocene history has been dominated mainly by wrench tectonics resulting from the activity of the now deactivated northwestern strand of the present day north anatolian fault zone

palaeogeographical evolution of the thrace neogene basin and the tethys paratethys relations at northwestern turkey thrace abstract the thrace neogene basin situated in northwestern turkey was initiated by strike slip faulting that was active from the early miocene until the end of the pliocene during the early miocene it began to form under the control of the thrace eskisehir fault zone initiated by continental collision in northwestern anatolia late oligocene early miocene during the late early miocene the basin was a site of mainly fluviatile and limnic sedimentation to the west and marine sedimentation via the paratethyan transgression in the north with the onset of the middle miocene the thrace block started to rotate in a counterclockwise sense and escaped westward with respect to the strandja istanbul block owing to rejuvenation of fossil fault systems within it in this period warm marine conditions were also established around the gulf of saros through a mediterranean originated transgression during the middle late miocene fluviatile and limnic conditions were created over the western thrace by the westerly propagation of the thrace eskisehir fault zone one of the principal results of the early middle miocene tectonics is the tilting of the strandja istanbul block to the south severing the tethys and the paratethys during the latest miocene early pliocene period the thrace eskisehir fault zone was deactivated because of the evolution of the north anatolian fault zone to the south the resurrected ganos fault zone situated on the dissected fossil suture zone in the sea of marmara also joined the north anatolian fault zone uplifting the gelibolu peninsula and thus severing the connection that existed between the sea of marmara and the paratethys the sea of marmara eventually became an endemic basin by the activity of the north anatolian fault zone

structural and hydrogeologic evolution of the putumayo basin and adjacent fold thrust belt colombia this multidisciplinary study evaluates the structural and hydrogeologic evolution of cretaceous age reservoirs in the putumayo basin colombia we focused on the eastern cordillera fold thrust belt along the southern garzon massif many important hydrocarbon accumulations occurred regionally along the proximal foreland basin and frontal fold thrust belt defining the eastern margin of the northern andes to understand why recent putumayo basin and adjacent thrust belt exploration has resulted in a wide range of oil quality and limited economic discoveries we reconstructed the structural evolution timing of oil migration and timing of groundwater infiltration by 1 assessing regional trends in formation water oil and reservoir properties 2 quantifying the timing of hydrocarbon generation and migration relative to trap formation using a two dimensional 2 d and three dimensional seismic data to define and constrain a restorable balanced cross section from the upper magdalena valley to the putumayo foreland and b coupled one dimensional thermal basin modeling 3 evaluating the potential roles of mesozoic extensional faulting and paleogene shortening in the generation and preservation of structural traps and 4 assessing groundwater influx from the modern foothills into the reservoir using a 2 d numerical groundwater flow model we suggest that four way closure is limited in the study area where most foreland verging structures create three way fault closures that do not effectively trap light hydrocarbons in addition east dipping structures and a relatively large reservoir outcrop area provide water infiltration pathways groundwater modeling suggests reservoirs were water washed by 2 200 million pore volumes since andean uplift finally average reservoir temperatures are 80 c 176 f which further facilitated biodegradation

sequence and eruptive style of the 1783 eruption of asama volcano central japan a case study of an andesitic explosive eruption generating fountain fed lava flow pumice fall scoria flow and forming a cone the 3 month long eruption of asama volcano in 1783 produced andesitic pumice falls pyroclastic flows lava flows and constructed a cone it is divided into six episodes on the basis of waxing and waning inferred from records made during the eruption episodes 1 to 4 were intermittent vulcanian or plinian eruptions which generated several pumice fall deposits the frequency and intensity of the eruption increased dramatically in episode 5 which started on 2 august and culminated in a final phase that began on the night of 4 august lasting for 15 h this climactic phase is further divided into two subphases the first subphase is characterized by generation of a pumice fall whereas the second one is characterized by abundant pyroclastic flows stratigraphic relationships suggest that rapid growth of a cone and the generation of lava flows occurred simultaneously with the generation of both pumice falls and pyroclastic flows the volumes of the ejecta during the first and second subphases are 0 21 km3 dre and 0 27 km3 dre respectively the proportions of the different eruptive products are lava cone pumice fall 84 11 5 in the first subphase and lava cone pyroclastic flow 42 2 56 in the second subphase the lava flows in this eruption consist of three flow units l1 l2 and l3 and they characteristically possess abundant broken phenocrysts and show extensive welding texture these features as well as ghost pyroclastic textures on the surface indicate that the lava was a fountain fed clastogenic lava a high discharge rate for the lava flow up to 106 kg s may also suggest that the lava was initially explosively ejected from the conduit the petrology of the juvenile materials indicates binary mixing of an andesitic magma and a crystal rich dacitic magma the mixing ratio changed with time the dacitic component is dominant in the pyroclasts of the first subphase of the climactic phase while the proportion of the andesitic component increases in the pyroclasts of the second subphase the compositions of the lava flows vary from one flow unit to another l1 and l3 have almost identical compositions to those of pyroclasts of the first and second subphases respectively while l2 has an intermediate composition suggesting that the pyroclasts of the first and second subphases were the source of the lava flows and were partly homogenized during flow the complex features of this eruption can be explained by rapid deposition of coarse pyroclasts near the vent and the subsequent flowage of clastogenic lavas which were accompanied by a high eruption plume generating pumice falls and or pyroclastic flows

compaction and gas loss in welded pyroclastic deposits as revealed by porosity permeability and electrical conductivity measurements of the shevlin park tuff pyroclastic flows produced by large volcanic eruptions commonly densify after emplacement processes of gas escape compaction and welding in pyroclastic flow deposits are controlled by the physical and thermal properties of constituent material through measurements of matrix porosity permeability and electrical conductivity we provide a framework for understanding the evolution of pore structure during these processes using data from the shevlin park tuff in central oregon united states and from the literature we find that over a porosity range of 0 70 matrix permeability varies by almost 10 orders of magnitude from 10 20 to 10 11 m 2 with over three orders of magnitude variation at any given porosity part of the variation at a given porosity is due to permeability anisotropy where oriented core samples indicate higher permeabilities parallel to foliation horizontally than perpendicular to foliation vertically this suggests that pore space is flattened during compaction creating anisotropic crack like networks a geometry that is supported by electrical conductivity measurements we find that the power law equation k 1 1 3 10 21 5 2 provides the best approximation of dominant horizontal gas loss where k 1 permeability and porosity application of kozeny carman fluid flow approximations suggests that permeability in the shevlin park tuff is controlled by crack or disk like pore apertures with minimum widths of 0 3 and 7 5 m we find that matrix permeability limits compaction over short times but deformation is then controlled by competition among cooling compaction water resorption and permeable gas escape these competing processes control the potential for development of overpressure and secondary explosions and the degree of welding in the deposit processes that are applicable to viscous densification of volcanic deposits in general further the general relationships among porosity permeability and pore geometry are relevant for flow of any fluid through an ignimbritic host

the history and dynamics of a welded pyroclastic dam and its failure the 2 360 bp eruption of mount meager british columbia began as an explosive dacitic sub plinian eruption that waned rapidly to a sustained period of vulcanian eruption triggered dome collapse events producing voluminous block and ash flow baf deposits the earliest baf deposits accumulated rapidly enough immediately downslope of the vent to retain heat and weld using the deposit as a paleoviscometer determines an effective viscosity of 109 1010 pa s during welding this prolific production of hot lava and block and ash flows in a steep mountainous terrain created a 110 m high largely impermeable dam capped by permeable non welded baf deposits and unconsolidated avalanche deposits that blocked the flow of the lillooet river and created a temporary lake the welded pyroclastic dam was compromised and overtopped at least once before the peak dam height was reached renewed eruption caused buildup of the dam to a maximum of 780 m above sea level asl and grew the temporary lake to an elevation of 740 m asl and a minimum volume of 0 55 km3 the rise of lake level led to catastrophic failure of the top of the dam generating an outburst flood that carved a canyon through most of the dam and resulted in a voluminous lahar that is traced at least 65 km downstream based on current flow rates of the lillooet river the lake would have overtopped the final dam at a minimum of 39 65 days after its formation the peak deluge lasted approximately 8 h and eroded a 2 5 km long canyon into the still hot dam core before returning to background flow rates

rheology of welding inversion of field constraints at present the mechanisms and rheological behaviour of pyroclastic deposits during welding and compaction are poorly understood here we explore the extent to which the rheological properties of pyroclastic deposits are constrained by physical property distributions in welded ignimbrite physical properties of samples from a 20 m section of the bandelier tuff new mexico are used as proxies for strain the observed strain et is ascribed to a combination of a time dependent viscous compaction ev and a time independent mechanical compaction em described by

the rheology of two phase magmas a review and analysis abstract we consider the current state of our understanding of the rheology of two phase magmas that is suspensions of either bubbles or crystals in a viscous silicate melt the discussion is restricted to strain rates at which the suspending melt can be considered newtonian we start by considering the range of textures found in magmas and the bubble deformation and particle motions caused by shearing we then review proposed models for suspensions focussing on those functions of the form r f or f that have been most widely used to describe magmatic systems r is the relative apparent viscosity of the suspension is the volume fraction of the suspended phase is the driving stress and is the strain rate both theoretical and empirical methods are presented and then compared against the available analogue i e non magmatic and magmatic data the paper contains new data and significant re analysis of previously published data we present a new semi empirical constitutive model for bubble bearing magmas that is valid for steady and unsteady flow and large strains and strain rates this equation utilises a new parameter the capillarity cx that encapsulates the combined effect of shearing and unsteadiness on bubble suspensions we also present a new scheme for dealing with polydispersivity of bubble suspensions new data on the rheology of particle suspensions undergoing forced oscillations are presented these data show that the cox merz rule only holds for dilute particle suspensions 0 25 a re analysis of all available experimental data that relate rheology to particle aspect ratio provides distinct curves of maximum packing as a function of aspect ratio for smooth and rough particles with magmatic data lying on the curve appropriate for rough particles we analyse several rheological datasets of crystal bearing basaltic magmas and find that they are in good agreement with the constitutive equations derived from analogue data by contrast the same equations do not agree well with data for high viscosity haplogranitic melts this may be an effect of fracturing or viscous dissipation within these samples the paper concludes with a practical rheological recipes section giving a step by step method for calculating a constitutive equation for a two phase magmatic suspension and assessing its likely accuracy

the myth of the brackish sarmatian sea the biota of the 1 5 ma period of the middle miocene sarmatian of the central paratethys lack stenohaline components this was the reason to interpret the sarmatian stage as transitional between the marine badenian and the lacustrine pannonian stages however our new data indicate that brackish water conditions could not have prevailed sarmatian foraminifera molluscs serpulids bryozoans dasycladacean and corallinacean algae as well as diatoms clearly indicate normal marine conditions for the entire sarmatian during the lower sarmatian however a sea level lowstand forced the development of many marginal marine environments during the late sarmatian a highly productive carbonate factory of oolite shoals mass occurrences of thick shelled molluscs and larger foraminifera as well as marine cements clearly point to normal marine to hypersaline conditions this trend is not restricted to the western margin of the pannonian basin system but can be observed in the entire central and even eastern paratethys

paleobiogeography and historical biogeography of the non marine caenogastropod family melanopsidae abstract we investigate the distributions of representatives of the family melanopsidae gastropoda caenogastropoda cerithioidea from the late cretaceous to present day the present contribution discusses and partly revises former schemes of melanopsid dispersal during the cenozoic all of which were based on outdated stratigraphic and tectonic concepts as well as an incompletely considered fossil record conflating a comprehensive and stratigraphically well constrained fossil record modern paleogeographical reconstructions and contemporary climate data our goal is to present a thorough model of melanopsid distribution and its changes over the cenozoic as well as its paleogeographical and climatic constraints the family melanopsidae evolved about 90 ma ago in the late turonian from brackish cerithioidean ancestors cretaceous and paleogene species occur in marginal marine to brackish environments along the shores of the tethys and paratethys seas the extant clades of melanopsis likely derive from the evolution of freshwater melanopsis on the balkan peninsula back in the late early miocene up to the pliocene freshwater species spread toward southwestern and southeastern europe and successively replaced brackish water representatives paralleling a general decline of latter systems during the late cenozoic the southwards expansion of melanopsis and its simultaneous retreat from northern latitudes resulted in the disjunct distribution pattern observed today the genus holandriana first appeared in northern italy in the late early miocene the genera microcolpia and esperiana both first occurred in the late miocene and likely derive from brackish water melanopsis species native to peri paratethyan lakes the present day biogeographic isolation of the three latter genera and melanopsis roots in the climatic deterioration and the disappearance of major lake systems in southeastern europe while thermophilous melanopsis retreated to the warm dry climates of the mediterranean and middle east holandriana microcolpia and esperiana adapted to the seasonal cold temperate climate of southeastern and eastern europe and some species became restricted to thermal springs

generation of block and ash flows during the 1990 1995 eruption of unzen volcano japan processes generating block and ash flows by gravitational dome collapse merapi type pyroclastic flow were observed in detail during the 1990 1995 eruption of unzen volcano japan two different types were identified by analysis of video records and observations during helicopter flights most of the block and ash flows erupted during the 1991 1993 exogenous dome growth stage initially involved crack propagation due to cooling and flowage of the dome lava lobes the mass around the crack became unstable locally decreasing in tensile strength finally a slab separated from the lobe front fragmented progressively from the base to the top within a few seconds and became a block and ash flow rock falls immediately followed in response to local instability of the lobe front clasts in these rock falls fragmented and merged with the preceding flow in contrast block and ash flows during the endogenous dome growth stage in 1994 were generated due to local bulge of the dome unstable lava blocks collapsed and subsequently fragmented to produce block and ash flows

fault textures in volcanic conduits evidence for seismic trigger mechanisms during silicic eruptions it is proposed that fault textures in two dissected rhyolitic conduits in iceland preserve evidence for shallow seismogenic faulting within rising magma during the emplacement of highly viscous lava flows detailed field and petrographic analysis of such textures may shed light on the origin of long period and hybrid volcanic earthquakes at active volcanoes there is evidence at each conduit investigated for multiple seismogenic cycles each of which involved four distinct evolutionary phases in phase 1 shear fracture of unrelaxed magma was triggered by shear stress accumulation during viscous flow forming the angular fracture networks that initiated faulting cycles transient pressure gradients were generated as the fractures opened which led to fluidisation and clastic deposition of fine grained particles that were derived from the fracture walls by abrasion fracture networks then progressively coalesced and rotated during subsequent slip phase 2 developing into cataclasite zones with evidence for multiple localised slip events fluidisation and grain size reduction phase 2 textures closely resemble those formed on seismogenic tectonic faults characterised by friction controlled stick slip behaviour increasing cohesion of cataclasites then led to aseismic distributed ductile deformation phase 3 and generated deformed cataclasite zones which are enriched in metallic oxide microlites and resemble glassy pseudotachylite continued annealing and deformation eventually erased all structures in the cataclasite and formed microlite rich flow bands in obsidian phase 4 overall the mixed brittle ductile textures formed in the magma appear similar to those formed in lower crustal rocks close to the brittle ductile transition with the rheological response mediated by strain rate variations and frictional heating fault processes in highly viscous magma are compared with those elsewhere in the crust and this comparison is used to appraise existing models of volcano seismic activity based on the textures observed it is suggested that patterns of long period and hybrid earthquakes at silicic lava domes reflect friction controlled stick slip movement and eventual healing of fault zones in magma which are an accelerated and smaller scale analogue of tectonic faults

interaction between trench retreat and anatolian escape as recorded by neogene basins in the northern aegean sea the evolution of the north aegean sea is studied through the development of three deep basins the north aegean trough the north skyros basin and the ikaria basin bathymetric data a 2d seismic dataset and the well investigated stratigraphic records of the onshore deep basins of northern greece and western turkey were used to make structural and seismic stratigraphic interpretations the study area shows two sharp unconformities that correspond to the eocene oligocene transition and the miocene pliocene shift these discontinuities were used as marker horizons for a more detailed structural and seismic stratigraphic interpretation resulting in the identification of several seismic units a general seismic signature chart was established using onshore basin stratigraphy and well data which was then used to constrain the ages of the different seismic units the main features observed in the basins are interpreted as 1 trans tensional growth patterns in pliocene and quaternary sediments that combine ne sw trending and steeply dipping fault zones that likely correspond to strike slip corridors and e w wnw ese trending normal faults 2 regional erosional truncations of miocene sediments likely related to the messinian salinity crisis msc 3 thick delta turbidite deposits of neogene age only the north aegean trough shows evidence of earlier development and polyphase deformation through inversion structures and additional seismic units extension processes in the aegean region have been driven by the hellenic slab rollback since the middle eocene the widespread development of neogene basins at the whole aegean scale attests to a major tectonic change due to an acceleration of the trench retreat in the middle miocene the present study shows that the neogene basins of the north aegean sea developed in dextral transtension with the northward migration of the associated ne sw trending strike slip faults at regional scale this tectonic pattern indicates that the westward escape of anatolia started to interact with the trench retreat in the middle miocene around 10 myr before the arrival of the north anatolian fault in the north aegean sea

sedimentation and diagenesis of an oligocene manganese deposit in a shallow subbasin of the paratethys thrace basin turkey abstract the northern part of the thrace basin intermittently connected to the paratethys seaway was the site of micritic carbonate sedimentation during the eocene pisolite and coarse shell debris in the earliest oligocene and clastic sediments through into the neogene near the transition from carbonate to clastic facies thin and discontinuous manganese ores at binkilic consist of interlayers of dominantly oxide and lesser carbonate minerals these occur as disseminated pisolitic oolitic concretionary and massive forms chief ore minerals are pyrolusite manganite cryptomelane rhodochrosite and kutnahorite in thin and polished sections mn carbonates in originally calcite monaxon sponge spicules are seen to have been replaced by mn oxides thus documenting the introduction of dissolved mn and major diagenetic alteration of primary calcite to mn carbonate and finally to mn oxide throughout the ore sequence the rees show pronounced positive eu and small negative ce anomalies carbon isotopes in the sequence show a narrow range of values from about 5 to 7 pdb within the range characterizing modern fresh waters the ore body formed during a marine regression and it was positioned adjacent to an embayment in the basin margin facts which support the hypothesis that the ore fluid was groundwater draining from mn bearing rocks of the nearby stranjha massif at a time when the basin was cut off from the paratethys this scenario thus differs significantly from that suggested for penecontemporaneous paratethyan mn deposits redox controlled primary precipitation of oxides and carbonates in segregated environments

assessment of impact of coal mining on ground and surface waters in tozakli coal field kirklareli northeast of thrace turkey in this study the surface and groundwaters of tozakli coal field were investigated in order to determine possible environmental impacts of coal mining on water pollution the water samples were analyzed for chemical trace metal and microbiological quality and compared with international directives epa and who in order to determine the impact of the mining activities as a source of pollution on bodies of water tozakli coal was lignitic rank and sulfur content varied between 9 and 4 the ph values of the waters were between 8 04 and 6 92 for the mine ponds and 8 7 and 6 6 for the groundwater and surface water the ca 2 mg 2 na k cl so 4 2 and no3 values of the waters varied between 394 2 and 52 195 and 1 200 and 22 6 and 1 1 and 0 9 756 and 20 2 4 and 1 1 mg l respectively in the mine ponds all the major cation and anion and trace element concentrations were below admissible limits of both epa and who except for so4 and no3 all the mine ponds and tap waters of the villages were contaminated by enterococcus spp while e coli and total coliforms were only present in the mine pond waters the geoaccumulation index igeo values of the clay samples from the mining area revealed that the soils were moderately contaminated by ni whereas as and ni concentrations had high anthropogenic shares due to coal mining the surface and groundwaters of the study area were not polluted by the coal mining operations

a precursor of the north anatolian fault in the marmara sea region abstract apatite u th he and fission track analyses of both basement and sedimentary cover samples collected around the marmara sea point to the existence of a system of major e w trending structural discontinuities active at least from the late oligocene in the early pliocene inception of the present day north anatolian fault naf system in the marmara region occurred by reactivation of these older tectonic structures this is particularly evident across the ganos fault in southern thrace as exhumation south of it occurred during the latest oligocene and north of it during the mid miocene in this area large tectonic structures long interpreted as the results of plio quaternary naf related transpressional deformation i e the ganos monocline the korudag anticline and the gelibolu folds were in fact produced during the late oligocene early miocene the overall lack of significant u th he age differences across the naf indicates that the early pliocene inception of strike slip motion in the marmara region represents a relatively minor episode at the scale of the entire marmara region the geographic pattern of exhumation ages shown in this study results instead from the complex superposition of older tectonic events including i the amalgamation of sakarya and anatolide tauride terranes and ii aegean related extension

miocene rhyolitic welded tuff infilling a funnel shaped eruption conduit shiotani southeast of matsue sw japan at shiotani sw japan rhyolitic welded tuff forms a steep sided funnel shaped body confined by paleogene granitic rocks to an elliptical area 1 1 5 km across the shiotani welded tuff is pervasively welded and foliated concordantly with the contact that dips inward at angles of 70 90 in contrast nearby contemporary volcaniclastic deposits are non welded and gently inclined near the contact with the granite the tuff is plastically deformed and shows lineations that plunge inward at angles of 40 65 lithic and crystal clasts in the rheomorphic outer part are rotated in a plane normal to the foliations and parallel to the lineations indicating downward flow of the welded tuff the geometry and internal structures suggest that the shiotani welded tuff was emplaced and welded in a funnel shaped eruption conduit upon collapse of a plinian or phreatoplinian eruption column the majority of the conduit filling pyroclasts probably fell back en masse into the conduit heat and steam from underlying magma and diffusion of interstitial volatiles into the glass perhaps reduced the viscosity of juvenile pyroclasts and facilitated welding in the conduit especially at deep levels the hot welded pyroclasts then flowed down the conduit wall during welding compaction and retreat of the magma these processes resulted in increased welding toward the contacts and welding foliations concordant with the steep wall emplacement of nearby correlative volcaniclastic mass flow deposits in a shelf to upper bathyal environment suggests a possibility that when active the shiotani conduit was under the sea welding compaction would occur even under the sea provided that the steam generated in the upper part of the conduit fill prevented water access

from tethys to eastern paratethys oligocene depositional environments paleoecology and paleobiogeography of the thrace basin nw turkey the oligocene depositional history of the thrace basin documents a unique paleogeographic position at a junction between the western tethys and the eastern paratethys as part of the tethys shallow marine carbonate platforms prevailed during the eocene subsequently a three staged process of isolation started with the oligocene during the early rupelian the thrace basin was still part of the western tethys indicated by typical western tethyan marine assemblages the isolation from the tethys during the early oligocene is reflected by oolite formation and endemic eastern paratethyan faunas of the solenovian stage the third phase reflects an increasing continentalisation of the thrace basin with widespread coastal swamps during the late solenovian the mollusc assemblages are predominated by mangrove dwelling taxa and the mangrove plant avicennia is recorded in the pollen spectra the final continentalisation is indicated by the replacement of the coastal swamps by pure freshwater swamps and fluvial plains during the late oligocene mammal zone mp 26 this paleogeographic affiliation of the thrace basin with the eastern paratethys after 32 ma contrasts all currently used reconstructions which treat the basin as embayment of the eastern mediterranean basin

welded breccias in andesite lavas flow breccias formed at the margins of blocky andesite lavas can be reheated welded and sometimes deformed to form rocks reminiscent of welded pyroclastic rocks reheating occurs due to advection of heat from the flow to the basal breccias surface breccias also infill extensional crevasses which are later closed and compressed strongly deformed welded breccia bands form within the flow levees the angular breccia clasts can be deformed into fiamme

volcanology of the 2350 b p eruption of mount meager volcanic complex british columbia canada implications for hazards from eruptions in topographically complex terrain the pebble creek formation previously known as the bridge river assemblage comprises the eruptive products of a 2350 calendar year b p eruption of the mount meager volcanic complex and two rock avalanche deposits volcanic rocks of the pebble creek formation are the youngest known volcanic rocks of this complex they are dacitic in composition and con tain phenocrysts of plagioclase orthopyroxene amphi bole biotite and minor oxides in a glassy groundmass the eruption was episodic and the formation com prises fallout pumice bridge river tephra pyroclastic flows lahars and a lava flow it also includes a unique form of welded block and ash breccia derived from col lapsing fronts of the lava flow this merapi type brec cia dammed the lillooet river collapse of the dam triggered a flood that flowed down the lillooet valley the flood had an estimated total volume of 10 9 m 3 and inundated the lillooet valley to a depth of at least 30 m above the paleo valley floor 5 5 km downstream of the blockage rock avalanches comprising mainly blocks of plinth assemblage volcanic rocks an older formation making up part of the mount meager vol canic complex underlie and overlie the primary vol canic units of the formation both rock avalanches are unrelated to the 2350 b p eruption although the post eruption avalanche may have its origins in the over steepened slopes created by the explosive phase of the eruption much of the stratigraphic complexity evident in the pebble creek formation results from deposition in a narrow steep sided mountain valley containing a major river

accretionary prism forearc interactions as reflected in the sedimentary fill of southern thrace basin lemnos island ne greece architecture of the well exposed ancient forearc basin successions of northeast aegean sea greece provides useful insights into the interplay between arc magmatism accretionary prism exhumation and sedimentary deposition in forearc basins the upper eocene lower oligocene basin fill of the southern thrace forearc basin reflects the active influence of the uplifted accretionary prism deep marine sediments predominate the basin fill that eventually shoals upwards into shallow marine sediments this trend is related to tectonically driven uplift and compression field stratigraphic sedimentological petrographic geochemical and provenance data on the lower oligocene shallow marine deposits revealed the accretionary prism i e pindic cordillera or biga peninsula as the major contributor of sediments into the forearc region field investigations in these shallow marine deposits revealed the occurrence of conglomerates with 1 mafic and ultramafic igneous rock clasts 2 low grade metamorphic rock fragments and 3 sedimentary rocks the absence of felsic volcanic fragments rules out influence of a felsic source rock geochemical analysis indicates that the studied rocks were accumulated in an active tectonic setting with a sediment source of mainly mafic composition and palaeodispersal analysis revealed a ne nne palaeocurrent trend towards the rhodopian magmatic arc thus these combined provenance results make the accretionary prism the most suitable candidate for the detritus forming these shallow marine deposits

circum mediterranean oligo miocene biogeographic evolution the gastropods point of view based on studies in iran qom basin esfahan sirjan basin zagros mountains in turkey mut and sivas basins in the mesohellenic basin and in northeastern egypt a new palaeobiogeographic concept for the oligocene and miocene in the circum mediterranean area with special emphasis on the distribution patterns of gastropod faunas is presented a very strict biogeographic terminology is proposed to avoid the common fusion of geographic faunistic and geodynamic terms in the palaeontologists jargon our main interest focuses on the affinities and the faunistic interactions between the early mediterranean and the early indo pacific regions during the oligo miocene especially the role of the early indo pacific faunas as the mythic centre of origination of early neogene european mollusc faunas as often vaguely indicated in the literature is critically evaluated this leads to the establishment of a mediterranean iranian province and a western indian eastern african province as palaeobiogeographic subunits of the western tethys region during the oligocene due to major geodynamic and related biogeographic changes in the early miocene the western tethys region no longer existed and was replaced by the proto mediterranean atlantic region for the area of the paratethys the palaeobiogeographic unit danubian province which includes the protocaspian subprovince is proposed furthermore the underrated transatlantic communication of the oligo miocene nearshore mollusc faunas is demonstrated altogether this paper is a contribution to the discussion on the biogeographic concepts classification and nomenclature in palaeontology as initiated by westermann palaeogeogr palaeoclimatol palaeobiogeogr 158 2000 1 13 163 2000 49 68 2002 elsevier science b v all rights reserved

paleoenvironmental evolution of the paratethys in the slovenian basin during the late paleogene several sections from the uppermost eocene and oligocene of northern slovenia have been investigated with respect to sedimentary facies foraminiferal assemblages stable isotopes carbonate microfacies and palynology the main objective was to reconstruct the paleoenvironmental history of the paleogene paratethys in this region of the eastern alpine realm the sediments exhibit a transgressive succession beginning with conglomerates sandstones and mudstones of fluvial and lacustrine origin followed by carbonates and muddy marls indicating marine conditions the foraminiferal faunal changes from brackish to shallow marine to deeper marine assemblages and the distribution of the palynofloras corroborate the sedimentological results microfacies analysis of the limestones shows a wide variation of shallow water generally mud rich facies dominated by coralline algae foraminifera and corals microfaunas adapted to low oxygen conditions indicate temporal sluggish bottom water circulation which can be associated with high fresh water fluxes these results are discussed as reflecting both the global sea level rise during the early oligocene and the regional tectonic and climatic evolution

field observations of pristine block and ash flow deposits emplaced april 16 17 1991 at volcan de colima mexico abstract for the first time since the effusive activity of 1981 1982 volcan de colima extruded scoriaceous andesitic lava on march 1 1991 this followed a period of increasing seismicity summit dome deformation and fumarolic activity that began in february of 1991 growth of the new lava dome proceeded until april 16 at 16 00 hrs local time gmt 6 hours when a series of gravitational failures of the upper edifice and the new lava dome flow triggered the emplacement of successive small volume non glowing block and ash flows to a distance of 4 km within the upper reaches of barranca el cordoban south southwest of the present summit aerial photos taken at the time of the event clearly show the lack of explosions at the summit dome efficient elutriation of the finest silt and clay sized fraction from the main body of the avalanching material produced large reddish yellowish and grayish ash clouds which rose to an altitude of 1 5 2 5 km for several hours and were carried southeast to northeast by predominant winds vegetation in the path of the debris was totally stripped sand blasted and bent in the sense of flowage but was not burnt no fatalities were reported we present a summary of our field observations of the pristine deposits which we studied prior the rainy season on april 20 27 between 2 200 and 2 500 m elevation

geochemistry of trace elements in the kesan coal and its effect on the physicochemical features of ground and surface waters in the coal fields edirne thrace region turkey abstract in this study concentration and origin of trace elements of the kesan coals in edirne thrace basin have been investigated in order to determine possible environmental impacts on water pollution the coal ground and surface waters and clay samples were taken from the coal mining area the concentration of trace elements in 14 coal ashes 15 water samples and seven clays was determined by inductively coupled plasma mass spectrometry additionally 11 of these coal samples were studied by proximate and seven coal samples were also studied by x ray diffraction analyses the mineralogical composition of the studied coal samples is made up mainly of quartz clay minerals feldspar group minerals pyrite and amorphous matter the kesan coal ash samples have higher average concentrations of cr 180 ppm ni 192 ppm rb 91 ppm and sr 1701 ppm average values of other trace elements are lower than the world average of brown coal ashes the sulfur content of the kesan coals ranges from 0 4 to 3 90 2 02 on average the ph values of the waters vary between 6 55 and 8 36 in coal fields 7 21 and 7 54 in springs the f cl no 3 so 4 ca mg na and k values of the waters vary between 0 11 and 0 25 mg l 33 49 and 52 90 mg l 0 05 and 59 27 mg l 85 and 2829 mg l 66 and 349 mg l 64 and 222 mg l 41 and 1187 mg l 2 and 13 mg l respectively in coal fields some elements are anomalous in concentrations in some water samples e g cr up to 49 6 ppb mn up to 1185 ppb fe up to 10 352 ppb ni up to 55 8 ppb as up to 9 7 ppb ppb it has been interpreted that the lower trace element concentrations in the water samples may be due to clay intercalated with coal the clays are smectite type and they are enriched in cr co ni as sr and th e g up to 394 ppm cr up to 305 ppm ni and up to 35 5 ppm as

time scales of compaction in volcanic systems we used 12 high temperature deformation experiments on fabricated cores of rhyolite ash to explore the effect of porosity on the rheology of pyroclastic deposits during deformation the cores of ash accommodate strain mainly by shortening and reduction of porosity porosity loss creates a strain dependent rheology expressed by a marked and continuous increase in effective viscosity the effective viscosity graphic 1 of pyroclastic materials is predicted as a function of porosity graphic 2 and melt viscosity graphic 3 o by graphic 4 the optimal value for the parameter based on the experimental data is 0 78 0 15 these experiments provide constraints on the time scales of compaction and flow processes in volcanic systems under variable conditions i e temperature load stress our results indicate that welding and compaction processes in pyroclastic deposits e g ignimbrites conduits can occur on time scales of tens of minutes to hours at these time scales welding is fully decoupled from cooling of the deposits and may be coupled to depositional processes within volcanic conduits welding processes operate on fragmented magma rapidly enough to eliminate porosity in a matter of hours thereby sealing off permeability and supporting cyclical vulcanian style explosive eruptions 1 embed inline graphic 1 gif 2 embed inline graphic 2 gif 3 embed inline graphic 3 gif 4 embed inline graphic 4 gif

palaeoenvironmental reconstructions by stable isotopes of middle miocene gastropods of the central paratethys abstract the stable isotopes of carbon and oxygen were used to provide information of mixing of marine and freshwater and subsequently used to determine palaeosalinities in the middle to late miocene st margarethen zollhaus section upper sarmatian mactra zone pannonian a succession of three gastropod assemblages indicates changing environmental conditions from a limnic fluviatile to littoral mudflat and a sublittoral marine environment several shells of the main representatives of the three assemblages potamides hartbergensis hilber granulolabium bicinctum brocchi potamides disjunctus sowerby and additionally shells of lymnaea sp a typical freshwater gastropod and pomatias conicus a terrestrial gastropod were taken for stable isotope analyses oxygen and carbon isotope data of the freshwater endmember are distinctively lower 18 o 4 5 13 c 9 than of the marine endmembers 18 o 2 2 13 c 2 3 in contrast to the expected intermediate isotopic composition between the freshwater and marine environment the shells of supposed brackish environments have higher 18 o values than the shells of the marine environment these higher 18 o values are explained by evaporation which affected the protected areas of riverine to lacustrine environments and small pools on mudflats formerly considered to be the habitats of the brackish assemblages thus the oxygen and carbon isotope data extend the already existing palaeoenvironmental information

eocene oligocene stratigraphy and structural history of the karaburun area southwestern black sea coast turkey transition from extension to compression the stratigraphic succession exposed in the karaburun area southern black sea coast nw turkey records multiple changes in depositional and tectonic settings during cenozoic times it starts with the middle upper eocene sogucak formation of reef limestone that across a normal fault omitting the lower part of the lower oligocene ceylan formation deep marine shale unit abuts the upper part of the ceylan formation that is made up of two facies 1 shallow marine sandstone and 2 shallow marine limestone units containing horizons of submarine slumps both facies are unconformably overlain by the fluvial upper miocene cukurcesme formation the tectonic record includes 1 latest eocene early oligocene ne sw extension 2 early oligocene ne sw shortening and 3 late miocene nw ne extension the earliest normal faults cutting the sogucak and the lower part of the ceylan formations are associated with clastic dykes injected into the deep marine shale these structures suggest a disruption of the eocene carbonate platform and are also known in the neighbouring thrace basin the following ne sw shortening created the ne vergent karaburun thrust that is synchronous with the shallowing and inversion of the ceylan basin rotation of the stress field is recorded by changes in clastic dyke orientation and their deformation compression caused multiple westerly directed submarines slides from uplifts in easterly located regions this event is not recorded in the thrace basin finally the miocene tectonic activity formed nw and ne striking normal faults the outlined tectonic history includes early oligocene extensional and compressional episodes recorded in the southern margin of the black sea that had hitherto not been known

porosity and lithology prediction at caballos formation in the puerto colon oil field in putumayo colombia at a given pressure and temperature differences in the velocities of propagation of p and s waves in rocks can indicate differences in various properties of the rocks including porosity lithological composition and the fluids occupying the pore space in the absence of direct s wave observations we study the response of interfaces between rock units to wavefronts with different angles of incidence to infer changes in s wave velocities we have used modern techniques of seismic inversion that involve p and s impedance estimation from various angle stacks to estimate the rock properties

welded block and ash flow deposits from mount meager british columbia canada abstract the 2360 years b p eruption of mount meager british columbia produced a succession of rarely observed welded block and ash flow deposits and non welded equivalents we report on these rhyodacitic block and ash flow deposits by describing the deposits documenting the nature of the welding process and establishing the origins of these pyroclastic deposits variations in welding intensity are tracked by image analysis of field texture maps petrographic study of shard morphology and measurements of sample density and porosity pyroclast oblateness from image analysis of texture maps provides a qualitative record of welding intensity but underestimates the amount of compactional e g volume strain when compared to estimates from physical property measurements e g density porosity unconsolidated deposits have an average matrix porosity of 41 38 45 and clasts have an average porosity of 32 24 40 in unconsolidated deposits isolated porosity is pervasive 50 m shortening of the thickest deposit from 162 m to the current 112 m the pyroclastic flow deposits result from accumulation in a narrow confined river valley the accumulation was sufficiently rapid to keep the deposits above their glass transition temperature thereby allowing the succession to weld as a single cooling unit the nature and distribution of isolated porosity in the juvenile clasts of rhyodacite suggest an explosive rather than effusive origin for these block and ash flow deposits that may be analogous to some vulcanian eruption triggered dome collapse processes observed at soufriere hills volcano montserrat rather than gravitational collapse

dense welding caused by volatile resorption welding of pyroclastic rocks is generally thought to occur by mechanical expulsion of interstitial gas from a deposit as it compacts under its own weight we propose here that volatile resorption and compression can also be important factors in welding we describe densely welded rocks which cannot be explained by loading and re evaluate the welding process taking into account the effects of volatile resorption into the glassy fragments intra caldera oligocene ignimbrites from the rhodope mountains bulgaria and intrusive tuffs of the loch ba ring dyke mull in scotland are intensely welded but some samples lack foliation eutaxitic texture fiamme and glass shards show no preferred orientation in thin section or on outcrop scale fiamme are sometimes complexy deformed into u or s shapes we propose that these textures are the consequence of volatile dissolution in the glass and gas compression scaling analysis indicates that there are two regimes for gas behaviour following emplacement of hot pyroclastic deposits which depend on the relative characteristic time scales of compaction gas escape and gas resorption a gas escape regime and a gas retention regime during explosive eruption glassy pyroclasts are decompressed to less than one atmosphere pressure and are outgassed during deposition and subsequent burial in a thick hot deposit volatiles will be retained and soluble gases h 2 o can be resorbed back into the glass defining the gas retention regime poorly soluble gases air are compressed to small fractions of their original volume resulting in destruction of pore spaces and vesicles in pumice in some circumstances such as volcanic vents the volume changes involve isotropic strain and implosion of the tuff resorption of water greatly speeds up welding during compactional loading by reducing the viscosity of the glass welding is inhibited not only by lower temperatures but also by entrainment of insoluble atmospheric gases the two regimes also can explain the common presence of post emplacement gas escape pipes in non welded ignimbrites and their rarity in densely welded ignimbrite factors that are likely to promote the gas retention regime include fine grain size low collapsing columns a large thickness of tuff and incorporation of external water

the region of the strandja sill north turkey and the messinian events the two sides of the strandja sill show a highly discontinuous stratigraphic succession since the late oligocene this area together with the sea of marmara basin is usually proposed as the gateway for the paratethyan freshwaters and organisms that constituted the lago mare facies in the mediterranean sea during the messinian salinity crisis msc our investigations involving new field observations and datings together with previous studies suggest that the sill has possibly experienced such a connection at around 8 ma i e significantly before the crisis the proposal of a sea level drop of the black sea before 7 ma is not supported by our data on dinoflagellate cysts consistency of calcareous nannofossil succession at dsdp site 380 is reinforced allowing to reassert that subaerial erosion impacted both the southwestern black sea and the central marmara dardanelles area during the peak of the msc at that time this region was crossed by two oppositely directed fluvial networks further supporting the absence of a marine gateway through the strandja sill it is concluded that none of the lago mare events recorded in the mediterranean during the msc were the consequence of the passage of paratethyan waters and organisms through this area in the black sea the well dated messinian fluvial erosion can be followed offshore the overlying prograding deltaic deposits attest to a fast marine reflooding after the crisis this constitutes a comprehensive erosion sedimentation model in an area intensively explored for hydrocarbons

sedimentology and stratigraphy of cenozoic deposits in the kagizman tuzluca basin northeastern turkey the kagizman tuzluca basin is located in the northeastern anatolia to the east of the intersection point near karliova of the major north and east anatolian fault systems this intermontane basin displays a thick sequence over 2000 m of mostly terrestrial deposits represented by repetitive alternations of the lake and fluvial environments ranging from late eocene oligocene to middle late miocene a marine incursion only mappable in the southeastern margin of the basin deposited limestones and sandy limestones rich in marine mollusks and nummulites in particular n fichteli that constrain an early oligocene age for this marine unit kagan fm the terrestrial basin fill deposits show different thicknesses throughout the basin due to irregular bottom topography and tectonic configuration of the basin margins the thickest deposits were accumulated along the different margins of the basin which received high quantities of siliciclastics from meandering river alluvial and coastal fans fan delta gilbert type delta and wave worked fluvial delta climate changes have also driven the development of lake environments during distinct depositional periods siliciclastic dominated overfilled lakes halikislak and kizilkaya formations and chemical dominated underfilled lakes turabi and tuzluca formations were formed they have been also classified as newark type and fundy type lakes respectively fluvial systems evolved from high energy meandering rivers deposited under humid climate gungoren formation to low energy meandering rivers resulted from arid and semiarid climates cincavat formation the transitional intervals from ephemeral river dry mudflat cincavat formation to saline pan lake tuzluca formation indicate wadi sand flat playa fluvial systems the chronostratigraphic constrains of the entire sequence remain poor and so far solely based on vertebrate fossil assemblages the evaporitic tuzluca formation would be middle miocene in age due to its stratigraphic position over the cincavat formation