environmental conditions for the presence of magnetofossils in the last glacial maximum inferred from magnetic parameters of sediments from the ulleung basin east sea abstract magnetic characterization of sediments from the ulleung basin in the east sea japan sea was carried out to decipher changes in environmental conditions over the last 39 000 years magnetic susceptibility intensities of natural remanent magnetization nrm anhysteretic remanent magnetization arm partial arm parm and saturation isothermal remanent magnetization sirm were measured for selected samples irm acquisition hysteresis and first order reversal curve forc measurements were made the ratios of rock magnetic parameters such as arm sirm arm and s ratio were determined to identify magnetic grain size and mineralogical variations along with electron microscope observations of magnetic mineral extracts down core variations in rock magnetic parameters for the 5 21 m long sediment core reveal distinct intervals with different grain size concentration and composition of magnetic minerals the uppermost portion and the high magnetic intensity zone hiz in marine isotope stage mis 2 are characterized by higher concentrations of fine grained magnetite whereas the mis 1 and 3 intervals contain lower concentrations of coarser grained magnetic minerals with increasing influence of hematite and or iron sulphide minerals the hiz interval is inferred to contain high occurrences of fine grained bacterial magnetosomes based on geochemical proxies east sea conditions for the hiz interval coincident with the last glacial maximum lgm can be summarized as having low total organic carbon toc enhanced eolian contributions from terrestrial organic particles and iron bearing minerals under the influence of an intensified east asian winter monsoon along with iron reducing but not sulphidic conditions that favoured growth and preservation of magnetotactic bacteria the delicate balance between reductive dissolution of magnetofossils under sulphidic conditions and production and preservation of magnetotactic bacteria in overlying iron reducing sediments for the hiz interval is responsible for the resultant abundance variations of magnetosomes in the studied sediments

high resolution magnetic stratigraphy across the oligocene miocene boundary in an alluvial lacustrine succession ebro basin northeast spain abstract the study of a late oligocene early miocene 300 m thick section of alluvial and shallow lacustrine sediments in the ebro basin has allowed a high resolution magnetic polarity stratigraphy for the oligocene miocene boundary to be established the samples studied include alluvial sandstones and mudstones as well as shallow lacustrine and paludine micritic and microsparitic limestones two hundred and fifty specimens were stepwise thermally or magnetically demagnetized following standard procedures magnetic imprints of the distinct lithologies present sharp contrasts especially for the stability of the secondary components the vgp data show 18 reversal events defining a sequence of 16 polarity intervals lateral and vertical continuity of the sequences studied has enabled a correspondence between the local paleomastological biozones and the magnetostratigraphic succession to be established the high resolution chronology of this magnetostratigraphic succession provides valuable information that allows the non marine european biochronological scales to be correlated to the global polarity time scale gpts the magnetic polarity zonation of the section has been correlated to the gpts using the distinct sequence and pattern polarity reversals as well as by considering the fossil mammal assemblages as a preliminary result chrons 8 7a 7 and 6c have been identified

interpreting avulsion process from ancient alluvial sequences guadalope matarranya system northern spain and wasatch formation western colorado alluvial deposits of the guadalope matarranya system oligocene ebro basin spain and the wasatch formation eocene western colorado provide time integrated records of the process of river channel avulsion these sequences consist of isolated channel belt sandstones incised into and abruptly overlain by flood plain siltstones indicating deposition by avulsive river systems the geometry and distribution of channel incisions suggest that avulsion was not controlled by tectonics climate or base level changes but formed by autocyclic processes measurements from 221 channel fills in the guadalope matarranya system and 38 from the wasatch formation allow us to statistically characterize channel geometries we infer to be associated with establishment and abandonment of individual river avulsions paleoflow depths in both systems average 1 4 to 1 6 m aggradation height superelevation of channel margin levees are on average 0 6 and 1 1 times paleoflow depth in the guadalope matarranya and wasatch systems respectively these results are consistent with values from recently avulsed modern rivers and suggest that 1 flow depth is the appropriate parameter against which to scale the critical superelevation necessary for channel avulsion and 2 the increase in potential energy due to channel perching drives the lateral instability that is needed for avulsion to be successful numerous stacked channel fills indicate repeated reoccupation of the same site by avulsing channels these reoccupation channels indicate that inherited flood plain topography here abandoned channel forms was an important control on the arrival site of newly avulsed channels comparison of our results to others suggests two end member types of avulsion can take place incisional avulsion seen here is characterized by an early incision phase followed by infilling by migrating bar forms aggradational avulsion begins with aggradation followed in time by stream integration into a single downcutting channel we suggest that the type of avulsion is strongly influenced by whether or not the adjacent flood plain is well or poorly drained in both cases subsequent aggradation and channel perching increase the chances that some triggering event will lead to avulsion

origins and paleoceanographic significance of laminated muds from the ulleung basin east sea sea of japan abstract a detailed facies analysis of long piston core sediments from the ulleung basin reveals four mud facies laminated mud crudely laminated mud bioturbated mud and homogenous mud the laminated and homogeneous muds were most likely deposited from turbidity currents whereas the bioturbated and crudely laminated muds were formed by hemipelagic pelagic sedimentation under well oxygenated and poorly oxygenated bottom water conditions respectively a detailed analysis of vertical distribution of the mud facies together with a chronostratigraphic framework derived from correlative tephra layers with known eruption ages reveals paleoenvironmental changes during the late quaternary during the period between 49 and 23 ka eustatic lowering of sea level facilitated frequent slope failure resulting in repeated deposition of fine grained turbidites on the basin floor normal hemipelagic sediments were intensively bioturbated under well oxygenated bottom water conditions during the period between 23 and 13 to 11 ka deposition from turbidity currents continued but hemipelagic sediments were non bioturbated under poorly oxygenated bottom water conditions the bottom water deoxygenation is attributed to further lowering of sea level during the last glacial period and consequent intensified stratification in the water column by freshwater supply to the nearly isolated sea primary laminae preserved in the crudely laminated mud generally exhibit low compositional bimodality in backscattered electron images which suggests low surface primary productivity and presence of superficial micro bioturbation after rapid rise of sea level at 13 to 11 ka the slopes were stabilized and pelagic sedimentation has prevailed under well oxygenated bottom water conditions

modelling of sedimentary basins from gravity anomalies with variable density contrast summary the decrease of density contrast with depth in sedimentary basins could be approximated by a quadratic function the sedimentary basin is viewed as a number of outcropping vertical prisms put in juxtaposition at each observation point equations are derived for the gravity anomaly of a vertical prism for a quadratic density function the initial model is obtained by calculating the thicknesses of the prisms at each station by an infinite slab formula the differences between the observed anomalies and the anomalies of the initial model at each station are used to modify the initial model a computer program is developed for initial estimates and refinement of the model the method is applied to interpret the gravity anomaly of san jacinto graben california where sediments filling the graben have a density contrast that can be approximated to a quadratic function finally the convergence of the method is discussed

a new chronology for the middle to late miocene continental record in spain abstract the first detailed chronology for the middle to late miocene continental record in spain is presented based on high resolution magnetostratigraphic data of mammal bearing sections which were studied in several basins calatayud daroca teruel valles penedes duero and jucar cabriel our results indicate that these sections compose an almost complete magnetostratigraphic succession from the lower aragonian mn4 to the middle turolian mn12 seven successive mammal neogene mn zone boundaries are directly dated in these sections which often contain faunas of two successive zones in superposition the three oldest boundaries are dated in the aragonian type area calatayud daroca basin the mn4 mn5 boundary vargas section occurs in chron c5cr o with a corresponding age of 17 26 0 01 ma the mn5 mn6 boundary aragon section in chron c5acn 0 8 with an age of 13 75 0 03 ma and the mn6 mn7 8 boundary aragon section in the interval c5ar 1n c5ar 3r with an age of 12 75 0 25 ma the mn7 8 mn9 aragonian vallesian boundary occurring in chron c5r 1n at 11 1 ma and the mn9 mn10 boundary in chron c4ar 3r at 9 7 0 1 ma are recorded in the valles penedes basin vallesian type area and are supported by the results from the duero basin torremormojon section in the turolian type area teruel basin the mn10 mn11 vallesian turolian boundary la gloria section occurs in chron c4an y at 8 7 0 1 ma taking into account the pre existing data from the jucar cabriel basin the mn11 mn12 boundary cabriel valley section is recalibrated to c4n 1n at an age of 7 5 0 1 ma

detection of land subsidence in semarang indonesia using stable points network spn technique land subsidence in semarang is a severe hazard threatening people and urban infrastructure the evolution of land subsidence has been monitored between 1996 and 2000 with few leveling stations hence maps show an overall distribution of land subsidence but are inaccurate in detail stable points network spn technique has been applied to improve land subsidence mapping spn measures ground motion using synthetic aperture radar satellite images for the spn processing 35 radar satellite images acquired between 2002 and 2006 have been selected derived land subsidence rates vary from fractions of 1 mm year to values of 10 cm year and even beyond classification and visualization of the ground motion data illustrate the boundary between mainly stable ground in the south of semarang and increasingly land subsidence affected land toward the coast final result is a map featuring the land subsidence with much higher accuracy as had been possible before this article presents a brief description of the land subsidence in semarang and introduces briefly the concept of spn technique results of spn based ground motion detection in semarang are presented and discussed from a user s point of view

manganese authigenesis in the landsort deep baltic sea abstract manganese mineralogy because of its redox sensitivity is a valuable parameter for interpreting water column anoxia and sediment diagenesis in the baltic and especially the landsort deep the relatively widespread occurrence of mn carbonates and the unique observations of authigenic mn sulphides in sedimentary environments need to be accounted for within the models proposed for mn authigenesis in diverse settings in this study stratigraphic changes in the geochemistry and mineralogy are documented in two gravity cores using petrographic microscopy xrd sem eds analyses of c and s content 13 c isotopes icp ms cation determinations and electron microprobe element profiling the lamination in the bottom sediments of the landsort deep suggests essentially continuous anoxic conditions at the sediment surface during the last ca 4500 14 c years the most striking variations in the sediments are related to the occurrence of two mn ii precipitate rich sapropel intervals recent and 1390 1990 14 c years bp sapropel deposition is associated with relatively slow detrital sedimentation allowing the concentration of organic matter the sediment c org content is influenced by the variations in the primary production as well as the supply of terrestrial c org but a major control appears to be detrital dilution the precipitation of mn carbonate as individual aggregates of spherical particles dispersed within clayey sediment matrix and as laminae with semi seasonal cyclicity is believed to be largely induced by the high alkalinity in connection with organic matter deposition and degradation where h 2 s has exceeded fe availability mns has also precipitated most commonly as well developed hexagonal crystals but also as the cubic variety alabandite which has not previously been reported from a sedimentary environment an expansion of the anoxic bottom water conditions during sapropel deposition is interpreted by correlation with laminated intervals on the slope of the deep basin budget calculations for the supply of mn to the basin during mn rich sapropel formation can be better balanced by the addition of mn from dissolution of oxides formed prior to the anoxic expansion the importance of alkalinity for the precipitation of mn carbonates and sulphides does not exclude the need for considerable mn concentrations but the model argued in several recently published studies stressing mn availability as the major control does not seem appropriate for the landsort deep and may be too restrictive in many other settings as well

magnetostratigraphic calibration of the european neogene mammal chronology abstract this paper presents first a discussion on the status of the subdivisions of the european neogene mammal chronology and second it synthesizes all available magnetostratigraphic data from europe to provide chronological framework for mammal localities mammalian events and mammalian biochronologic units of the european neogene because of the lack of their rock equivalents the subdivisions of the european neogene based on mammals have not attained the stage status in terms of reliability except the vallesian and turolian therefore they are designated as the european land mammal ages elma magnetostratigraphic data on mammal bearing deposits in europe is still scarce in time and space consequently it is not yet possible to correlate accurately all elma and mn zones with the geomagnetic polarity time scale gpts nevertheless several studies dealing with mammal localities and their deposits around the oligocene miocene boundary in the middle and late miocene provide reliable correlations of some elma and mn zone boundaries thus the calibration of the oligocene miocene boundary at the base of chron c6cn 2n is in agreement with its age in marine deposits the well known hipparion datum astaracian vallesian boundary is now dated as about 10 8 ma occurring slightly above the base of chron c5n 2n this paper also reviews magnetostratigraphic correlations of some late miocene and pliocene mammal localities in the paratethys area taking into account the chronological assessments in other parts of europe for some key mammalian events new correlations with the gpts have been proposed for these localities thus some new ages are suggested for the late miocene and pliocene paratethys stages

widespread submarine tephras around japan petrographic and chemical properties abstract in deep sea sediments around the japanese islands tephra layers are frequently recognized and some tephras can be identified by petrographic and chemical features and correlated to source volcanoes of both japan and korea most tephras distributed over more than several hundred kilometers from the source volcanoes were presumably carried away by the dominant westerly wind six characteristic marker tephras in deep sea sediments can be identified and correlated according to their distribution and grain size petrography and chemistry they play an important role in compiling the late quaternary chronology of the deep sea sediments distributed around the japanese islands petrographic and geochemical studies reveal that the refractive index of volcanic glass shards in tephras is controlled by the amount of total transition metal oxides rather than the amount of sio 2 we propose a new equation relating refractive index to glass shard chemistry

global warming may have slowed down the deep conveyor belt of a marginal sea of the northwestern pacific japan sea weakening of the abyssal circulation conveyor belt in the japan sea during the 20th century is deduced from the decreasing trend of bottom dissolved oxygen o2 this trend indicates a shortened o2 supply caused by too inactive conveyor belt to compensate for biological o2 consumption at the bottom of the sea recent climatic changes during the winter season in the northern japan sea may play a significant role in prohibiting the formation of surface seawater dense enough to sink to the bottom it is predicted that the japan sea bottom water will become anoxic within a few hundred years as it was in the last glacial maximum

contour current accumulation off the vema channel mouth southern brazil basin pattern of a contourite fan abstract in the southern part of the brazil basin 3 5 khz echosounding reveals the existence of a cone shaped sedimentary accumulation 4480 m depth this sediment body is interpreted as deposited by the antarctic bottom water currents aabw at the downstream exit of deep valleys cutting through the rio grande rise it is located between two major channels that prolonged northeastward the valleys into the brazil basin the vema channel in the southeast and the sao paulo abyssal gap in the northwest as a consequence most of the aabw flow is channelized in two branches deposition of the current transported particles occurs below the shear zone which takes place between the two branches the quaternary sediments consist of silty clayey muddy contourites associated with manganiferous deposits the accumulation is built by lateral migration of secondary channels and by lateral construction of lobes between the two major channels which are both well stabilized on account of a morphotectonic control on their location the entire sediment body progrades upward and downstream toward the northeast on the basis of morphological seismic and lithological arguments we would like to propose the name of contourite fan for such a contour current controlled accumulation

gis based assessment of risk due to salt mining activities at tuzla bosnia and herzegovina ground subsidence triggered by salt mining from deposits located beneath the city of tuzla bosnia and herzegovina is one of the major dangers acting on a very densely urbanized area since 1950 when the salt deposit exploitation by means of boreholes began as demonstrated in this paper subsidence induced several hazard factors such as severe ground deformations the arising of deep and superficial fractures and a very fast water table rise connected with the brine extraction now affecting several districts the above mentioned factors have been quantified by the use of geomatic methodologies including field surveys and analysis of geographical data in order to estimate the historical sinking rates authors processed the large and never before processed amount of topographical data collected during two periods from 1956 to 1991 and from 1992 to 2003 with only poor data collected afterward traditional surveys were completely and definitively stopped the analysis reveals a cumulative subsidence as high as 12 m during the whole period causing damage to buildings and infrastructures within an area that includes a large portion of the historical town at present almost entirely destroyed modern sinking rates have been monitored with static gps whereas the presence of superficial fractures monitored with kinematic gps factors related to the presence of deep fractures and water table rise have been evaluated by curvature analysis techniques and piezometric data respectively finally hazard factors have been combined in a risk map using the gis geographical information system map algebra capabilities and a simple multicriteria decision analysis mda in order to do that a vulnerability map has been derived on the basis of information reported on a couple of recently sensed high resolution satellite imageries the final risk arisen from the combination of single hazard factors and vulnerability map highlights critical scenarios and unsuspected threatening that are under consideration by the local decision makers and urban planners in particular as highlighted in the final risk map the present day water table rise triggered by the decrease in brine pumping is seriously posing a threat to a portion of the city which is not the most involved in ground deformations

magnetostratigraphy and small mammals of the late oligocene banovici basin in ne bosnia and herzegovina article i nfo a combined magnetostratigraphic and small mammal investigation was carried out to acquire better age control on the sedimentary infill of the banovici basin in bosnia and herzegovina although the dinarides occupy a crucial paleogeographic position bridging central europe and anatolia no detailed records of its small mammal fauna have been published until now a rich small mammal assemblage with over 500 molars was excavated from a section exposing marls and clays just underlying the basins main coal layer the fauna of this turija small mammal locality compares best with the uppermost oligocene to lowermost miocene localities from the european mp30 mn1 mammal zones and with anatolian zone b from central turkey a 160 m thick series of lacustrine sediments overlying the main coal layer in the nearby grivice section was sampled for paleomagnetic purposes the magnetostratigraphic pattern of the grivice section comprises a long reversed interval a subsequent short normal interval and another reversed interval the most logical correlation of this pattern to the late oligocene part of the geomagnetic polarity time scale gpts is to chrons c6cr c6cn 3n and c6cn 2r 24 to 23 2 ma this correlation implies a sedimentation rate of 20 cm kyr for the banovici basin and an age of approximately 24 ma for the turija mammal site the proposed correlation fits well with other magnetostratigraphically calibrated mammal records in western and central europe as well as anatolia and with the recalibrated ages of 24 95 0 05 ma and 24 72 0 04 ma for two basalt flows bracketing the enspel mp28 site in southern germany our results indicate that a limited exchange of fauna from central asia to western europe existed in late oligocene and miocene times

three dimensional interpretation of gravity data from sedimentary basins using an exponential density depth function in mapping the topography of the basement of deep sedimentary basins by gravity modelling the accuracy can be improved by incorporating an exponential increase in density with depth for calculating the gravity effect of a three dimensional 3d structure with such an exponential density depth relation a frequency domain forward algorithm based on series expansion is presented the numerical evaluation of which can be performed efficiently by fast fourier transform the algorithm can be applied in a recursive procedure to give the inverse solution in terms of basement relief the inversion procedure is satisfactorily tested on a 2d synthetic example and a 3d field example of gravity data from the western margin of the pannonian basin in eastern austria where up to 2 2 km of tertiary sediments overlie an igneous or metamorphic basement the results are confirmed by basement intersections in several wells

assessing sinkhole activity in the ebro valley mantled evaporite karst using advanced dinsar abstract sinkholes in karst areas may cause subsidence damage in transportation infrastructures demolition of buildings and even the loss of human lives when they occur in a catastrophic way differential interferometry dinsar is a promising technology for detecting and characterizing sinkholes as well as for reducing the associated risk when combined with other sources of data such as a sinkhole inventory in this work the usefulness of insar techniques and data for sinkhole risk management has been analyzed through the comparison of three dinsar derived velocity maps with a comprehensive sinkhole inventory in the ebro valley ne spain the dinsar maps have contributed to improve the sinkhole inventory in different ways 1 detection of non inventoried sinkholes 2 revision of sinkhole areas previously classified as inactive as active and 3 refinement of underestimated sinkhole boundaries the obtained results suggest that dinsar products are suitable for analyzing active dissolution induced subsidence the application of these techniques may help in recognizing and better characterizing previously unknown karst subsidence problems and in preventing personal and property losses however the analysis reveals that the available dinsar maps combined overlook about 70 of the previously mapped active sinkholes mainly due to decorrelation

authigenic sulfide and carbonate mineral formation in holocene sediments of the baltic sea formation of authigenic sulfides and carbonates in holocene 14c dated sediments is interpreted based on analyses of cations fes s fes2 s corg and sulfur isotopes mineral distribution was studied in thin sections and mineral morphology with sem eds the sediments were deposited in the gotland deep baltic sea during freshwater and brackish stages calcium rich rhodochrosite mnco3 occurs in concentrations up to 17 dw in brackish water sediments and are mainly confined to 0 02 0 5 mm thick laminae the frequency with which these laminae occur suggests that they formed with a periodicity of one to a few years and their purity suggests that formation took place in a few weeks we propose that these carbonate laminae resulted from oxic water inflow to the euxinic basin mn ii dissolved in the water column was rapidly oxidized and large amounts of mn oxides reached the sediment reduction of these mn oxides in a high alkalinity environment facilitated rhodochrosite precipitation at the sediment surface pyrite in the brackish water sediments formed at or above the sediment water interface in an iron limited environment due to alternating oxic and euxinic conditions fes was oxidized resulting in a high fes2 sfes s ratio median 170 formation of iron sulfides in the freshwater sediments occurred below the sediment water interface in a sulfate limited environment as a result of the rapid exhaustion of reactive iron in the brackish water sediments excess h2s diffused downwards to pyritize the uppermost part of the underlying freshwater sediments

turbidity current sediment waves on the submarine slopes of the western canary islands two sediment wave fields have been identified on the flanks of the western canary islands of la palma and el hierro using a high quality 2 d and 3 d dataset that includes geosea and tobi imagery 3 5 khz profiles and short sediment cores the la palma sediment wave field covers some 20 000 km2 of the continental slope and rise and consists of sediment waves with wave heights of up to 70 m and wavelengths of up to 2 4 km the wave crestlines have a complex morphology with common bifurcation and a clear sinuosity waves have migrated upslope through time cores recovered from the wave field contain volcaniclastic turbidites interbedded with pelagic hemipelagic layers the wave field is interpreted as having formed beneath unconfined turbidity currents a simple previously published two layer model is applied to the waves revealing that they formed beneath turbidity currents flowing at 10 100 cm s 1 with a flow thickness of 60 400 m and a sediment concentration of 26 427 mg l the el julan sediment wave field lies within a turbidity current channel on the southwest flank of el hierro the sediment waves display wave heights of about 6 m and wavelengths of up to 1 2 km the waves are migrating upslope and migration is most rapid in the centre of the channel where the flow velocity is highest this wave field has been formed by channelised turbidity currents originating on the flanks of el hierro

paleoenvironmental changes in the japan sea during the last 85 000 years five distinct changes in the paleoenvironment of the japan sea within the last 85 000 years are revealed from the sedimentary record of a piston core recovered from the oki ridge changes in both surface and deepwater conditions are registered by changes in lithology calcium carbonate content organic carbon content oxygen and carbon isotope ratios and microfossil assemblages including calcareous nannoplankton diatoms radiolaria and foraminifera between 85 and 27 ka the warm tsushima current did not flow into the japan sea and cold surface water conditions prevailed environments at the seafloor fluctuated between dysaerobic to weakly oxic conditions between 27 and 20 ka freshwater input to the japan sea probably from the huang ho river in china stratified the water column and the severe anoxic conditions eliminated most benthic fauna between 20 and 10 ka the cold oyashio current flowed into the japan sea through the tsugaru strait reestablishing deepwater ventilation shallow water benthic assemblages of the north pacific ocean subsequently colonized the japan sea and occupied the vacant niches of the deep basins between 10 and 8 ka the foraminifer compensation level fcl gradually rose to a depth shallower than 1000 m and bottom conditions changed from dysaerobic to oxic at 10 ka the warm tsushima current started to flow into the japan sea through the tsushima strait to establish the modern oceanographic regime which has existed since 8 ka the eustatic sea level during the last glacial maximum was above the sill depths 130 m of the tsushima and tsugaru straits assuming that tectonic movements at these straits were negligible for the last 20 ka

stable inversion of gravity anomalies of sedimentary basins with nonsmooth basement reliefs and arbitrary density contrast variations we present a new stable method for interpreting the basement relief of a sedimentary basin which delineates sharp discontinuities in the basement relief and incorporates any law known a priori for the spatial variation of the density contrast the subsurface region containing the basin is discretized into a grid of juxtaposed elementary prisms whose density contrasts are the parameters to be estimated any vertical line must intersect the basement relief only once and the mass deficiency must be concentrated near the earth s surface subject to the observed gravity anomaly being fitted within the experimental errors in addition upper and lower bounds on the density contrast of each prism are introduced a priori one of the bounds being zero and the method assigns to each elementary prism a density contrast which is close to either bound the basement relief is therefore delineated by the contact between the prisms with null and nonnull estimated density contrasts the latter occupying the upper part

the interplay between turbidity and contour current processes on the columbia channel fan drift southern brazil basin abstract the distribution of sedimentary processes and associated deposits on the columbia channel fan drift system southern brazil basin were investigated on the basis of 3 5 khz echosounding profiles and core lithology this system is composed of a sediment levee elongated downslope with a w e then sw ne trend bounded to the south by the columbia channel and to the north by the vitoria trindade seamounts turbidites are widespread on the shallowest part of the system 1 thick turbidite sequences composed of quartz rich sandy material originating from the upper continental margin are found in the axis of the channel the turbidity currents do not significantly overflow the northern levee where only sparse and thin silty muddy turbidites occur close to the axis of the channel 2 the major part of the levee shows quartz poor mica and foram rich turbidite material originating from the vitoria trindade seamounts the abundance of this material decreases southwards and eastwards the whole area is swept by the northward flowing antarctic bottom water contour current deposited muds are dominant on the southern flank of the columbia channel free of any turbidite supply as a consequence of the coriolis effect and on the deepest part of the northern levee remote from turbidite source areas however the contour currents interplay with the turbidity currents on the shallowest part of the levee contour current deposited muds are interbedded with silty sandy turbidite sequences and a part of the muddy material has probably been pirated from the finer tails of the turbidity flows the other part being transported from southernmost areas by the bottom currents the interplay of both processes is also responsible for the deposition of silty turbidite beds top truncated by contour currents and overlain by bioturbated muddy contourites

fine structures of turbidite and associated muds in the ulleung tsushima basin east sea sea of japan abstract the ulleung basin is a presently tectonically inactive back arc basin it is a nonfan slope centered sedimentary basin in which up to 800 m of mostly fine grained turbidites have accumulated the precursors of these turbidity currents were slides slumps and debris flows on the slope and near the base of slope an ideal mud turbidite sequence identified in cores from the basin includes divisions of laminated mud e1 graded mud e2 and homogeneous mud e3 associated with convolute mud e4 bioturbated mud f1 bioturbated mud with authigenic pyrite f2 and indistinctly laminated mud g e1 through e4 muds are turbiditic in origin as evidenced by an absence of bioturbation preferred orientation of large sediment particles liquefaction and high organic carbon content all suggestive of rapid deposition from unidirectional flow the indistinctly laminated mud g is characterized by poorly defined laminae slight bioturbation intermediate organic carbon content and large amounts of skeletal debris in the silt fractions in contrast to both the turbiditic and bioturbated muds this mud is suggestive of deposition from bottom currents the bioturbated mud f1 resulted from slow particle by particle settling in the postglacial oxic environment whereas the bioturbated mud with pyrite filaments f2 is due to deposition in suboxic environment when the basin was isolated from the pacific during the last glacial period both bioturbated muds are low in organic carbon poorly sorted and characterized by random orientation of large sediment particles

salty groundwater flow in the shallow and deep aquifer systems of the schleswig holstein area north german basin abstract in the schleswig holstein area salty groundwaters are not always spatially related to the presence of shallow sat structures furthermore hydrochemical data point to instable salinity profiles and to the occurrences of deep brines close to the surface therefore complex interaction between shallow and deep solute migration must occur numerical simulation of fluid flow mass and heat transport have been carried out in order to understand the role of shallow salt dissolution and young geological features on groundwater flow as well as to investigate the interrelationships between shallow and deep aquifer systems for these purposes a shallow 500 m and a deep profile model 5 km have been constructed the results indicate that different flow regimes coexist within the study area shallow brine migration is strongly controlled by the geological features of the basin such as salt flank glacial channels and sand layers furthermore shallow salt dissolution is the major cause for gravitational convection in the deeper aquifers this source of salinization from above leads to the formation of instable salinity profiles at 2 km depth further interactions between shallow and deep fluid flow exist in the eastern part of the basin where brine upconing is due to both topography driven flow and thermohaline convection the simulations also showed that the hydraulic conductivity of the stratigraphic units influences the brine regime on a regional scale gravitational convection is likely to occur in permeable units located near shallow salt structures while thermohaline convection persists within thick permeable areas in which salt dissolution is not the dominant process the presented study provides new insights into fluid basin processes the described flows could develop in any geothermal basin hosting salt diapirs which pierce shallow aquifer systems

crustal deformation at the sumatran subduction zone revealed by coral rings analyses of coral rings grown in the interval 1970 1997 reveal a geographically distinct pattern of interseismic uplift off sumatra s western coast at distances less than 110 km from the sumatran trench coral reefs are submerging as fast as 5 mm y at 130 and 180 km distance from the trench they are emerging at similar rates we suggest that a locked or partially locked patch located above 30 km depth on the upper surface of the subducting oceanic plate generates this pattern

a complete terrestrial oligocene magnetobiostratigraphy from the ebro basin spain abstract the integrated litho bio and magnetostratigraphic cross correlation of 11 continuous and correlatable sections in the southeastern ebro basin ne spain produced a complete oligocene magnetic polarity stratigraphy ranging from latest eocene to earliest miocene the magnetic polarity zonation of the different alluvial and shallow lacustrine sections has been correlated to the gpts using fossil mammals and the distinct sequence and pattern of polarity reversals the composite magnetic polarity sequence defines a continuous sequence from chron c15n to chron 6cn 2n from 34 8 to 23 7 ma late eocene early miocene in addition a few short normal and reverse polarity events that correlate to cryptochrons in the gpts are found i e in c11n 1r and c8n 1r the resulting regional magneto biostratigraphic framework based on fossil mammals is proposed to refine the dating of the european oligocene biochronological mammal paleogene units and correlate them with the standard oligocene marine stages and the north american land mammal ages the magnetochronology now established enables more precise dating of the late eocene and oligocene paleofloristic and paleofaunistic changes in southwestern europe which were coeval to ongoing global paleoclimatic and paleoceanographic changes on earth caused by high latitude cooling and ice sheet development in eastern antarctica

the influence of urbanization of sinkhole development in central pennsylvania the karsted limestone valleys of central pennsylvania contain two populations of sinkholes solution sinkholes occur in the champlainian limestone units along the margins of the valleys solution sinkholes are permanent parts of the landscape and although a nuisance to construction do not present other problems the second population is the suffosional or soil piping sinkholes these occur on all carbonate rock units including the beekmantown and gatesburg dolomites that comprise the two principal carbonate aquifers in the valley suffosional sinkholes are the principal land use hazard suffosional sinkholes are transient phonomena they occur naturally but are exacerbated by runoff modifications that accompany urbanization suffosional sinkholes are typically 1 5 2 5 m in diameter depending on soil thickness and soil type the vertical transport of soil to form the void space and soil arch that are the precursors to sinkhole collapse is through solutionally widened fractures and cross joints and less often through large vertical openings in the bedrock the limited solution development on the dolomite bedrock combined with soil thickness seldom greater than 2 m limits the size of the sinkholes all aspects of suffosional sinkhole development are shallow processes transport piping void and arch formation and subsequent collapse take place usually less than 10 m below the land surface factors exacerbating sinkhole development include pavement street and roof runoff which accelerates soil transport such seemingly minor activities as replacing high grass and brush with mowed grass is observed to accelerate sinkhole development dewatering of the aquifer is not a major factor in this region

subsidence rates and urban damages in alluvial dolines of the central ebro basin ne spain in the central ebro basin alluvial dolines develop on quaternary materials overlying neogene evaporites this process is very active analysing aerial photographs of different years important differences can be observed since the 1970s when the urbanisation of the area took place karst processes have damaged many buildings and infrastructures from the dates of construction and the repair of a number of buildings and pavements we calculate subsidence rates 12 120 mm year moreover we decided to monitor for around 4 years three dolines developed on urban areas to determine their subsidence behaviour a water level device with an error of 2 3 mm was utilised for this purpose the subsidence rates so obtained are 64 5 39 and 21 mm year which fit with the previous data from repaired zones

the southern margin of the east european craton new results from seismic sounding and potential fields between the north sea and poland abstract the extension of eastern avalonia from britain through the ne german basin into poland is in some sense a virtual structure it is covered almost everywhere by late paleozoic and younger sediments evidence for this terrane is only gathered from geophysical data and age information derived from magmatic rocks during the last two decades much geophysical and geological information has been gathered since the european geotraverse egt which was followed by the babel lt 7 mona lisa dekorp basin 96 and polonaise 97 deep seismic experiments based on seismic lines a remarkable feature has been observed between the north sea and poland north of the elbe line el the lower crust is characterised by high velocities 6 8 7 0 km s a feature which seems to be characteristic for at least a major part of eastern avalonia far eastern avalonia in addition the seismic lines indicate that a wedge of the east european craton eec or baltica continues to the south below the southern permian basin spb a structure which resembles a passive continental margin the observed pattern may either indicate an extension of the baltic crust much farther south than earlier expected or oceanic crust of the tornquist sea trapped during the caledonian collision in either case the data require a reinterpretation of the docking mechanism of eastern avalonia and the elbe odra line eol as well as the elbe fault system together with the intra sudedic faults appear to be related to major changes in the deeper crustal structures separating the east european crust from the paleozoic agglomeration of middle european terranes

a new geomagnetic polarity time scale for the late cretaceous and cenozoic we have constructed a magnetic polarity time scale for the late cretaceous and cenozoic based on an analysis of marine magnetic profiles from the world s ocean basins this is the first time since heirtzler et al 1968 published their time scale that the relative widths of the magnetic polarity intervals for the entire late cretaceous and cenozoic have been systematically determined from magnetic profiles a composite geomagnetic polarity sequence was derived based primarily on data from the south atlantic anomaly spacings in the south atlantic were constrained by a combination of finite rotation poles and averages of stacked profiles fine scale information was derived from magnetic profiles on faster spreading ridges in the pacific and indian oceans and inserted into the south ariantic sequence based on the assumption that spreading rates in the south atlantic were smoothly varying but not necessarily constant a time scale was generated by using a spline function to fit a set of nine age calibration points

the diachroneity of alluvial fan lithostratigraphy a test case from southeastern ebro basin magnetostratigraphy abstract alluvial fan strata contain valuable proxy data for kinematic climatic and sediment flux phenomena associated with high relief source regions proper application of this data is dependent upon acquisition of accurate high resolution chronostratigraphic data best achieved through magnetostratigraphy collection of magnetostratigraphic and other proxy data from composite alluvial fan sections assumes the chronostratigraphic significance of lithostratigraphy we present the first test of this assumption with new magnetostratigraphy collected from paleogene rocks of the southeastern ebro basin we report five new magnetostratigraphic sections that collectively sample 850 m of alluvial fan and associated fluvial strata one hundred meters of lithostratigraphic overlap between these sections reveals equivalent magnetic polarities over short along strike distances 200 2000 m however lithostratigraphic correlation of these sections with the magnetostratigraphy of continuously exposed strata eight km away reveals discrepancies in magnetic polarity trends and age interpretations correlation of our 760 m composite magnetostratigraphic section with the paleogene geomagnetic polarity time scale suggests that this section spans from ca 31 3 to 27 7 ma c12r c9n early to late oligocene this correlation implies steady sedimentation rates of 12 cm ka for fluvial facies and 32 cm ka for alluvial fan facies alternative interpretations that force chronostratigraphic correlation with the lithostratigraphically equivalent interval generate unsteady and or unlikely sedimentation rates in one or both of the stratigraphies and require rejection of multiple well constrained polarity zones the absence of significant surfaces of erosion or paleosol development argue against these alternative interpretations and suggest that even in the best exposed study areas alluvial fan successions may be diachronous and preclude lateral extrapolation of chronostratigraphic and other proxy data interpretations and models based upon data collected from alluvial fan strata may be tenuous unless supported by sufficient spatial overlap to constrain the relationship between time surfaces and rock surfaces

characterization of gas hydrate reservoirs by integration of core and log data in the ulleung basin east sea abstract examinations of core and well log data from the second ulleung basin gas hydrate drilling expedition ubgh2 drill sites suggest that sites ubgh2 2 2 and ubgh2 6 have relatively good gas hydrate reservoir quality in terms of individual and total cumulative thicknesses of gas hydrate bearing sand hybs beds in both of the sites core sediments are generally dominated by hemipelagic muds which are intercalated with turbidite sands the turbidite sands are usually thin to medium bedded and mainly consist of well sorted coarse silt to fine sand anomalies in infrared core temperatures and porewater chlorinity data and pressure core measurements indicate that gas hydrate occurrence zones ghoz are present about 68 155 mbsf at site ubgh2 2 2 and 110 155 mbsf at site ubgh2 6 in both the ghoz gas hydrates are preferentially associated with many of the turbidite sands as pore filling type hydrates the hybs identified in the cores from site ubgh2 6 are medium to thick bedded particularly in the lower part of the ghoz and well coincident with significant high excursions in all of the resistivity density and velocity logs gas hydrate saturations in the hybs range from 12 to 79 with an average of 52 based on pore water chlorinity in contrast the hybs from site ubgh2 2 2 are usually thin bedded and show poor correlations with both of the resistivity and velocity logs owing to volume averaging effects of the logging tools on the thin hybs beds gas hydrate saturations in the hybs range from 15 to 65 with an average of 37 based on pore water chlorinity in both of the sites large fluctuations in biogenic opal contents have significant effects on the sediment physical properties resulting in limited usage of gamma ray and density logs in discriminating sand reservoirs

a calibrated mammal scale for the neogene of western europe state of the art abstract a magnetobiostratigraphically calibrated mammal scale for the neogene of western europe is presented in this paper the mammal neogene mn units originally proposed by mein report on activity rcmns working groups 1975 have been re defined here on the basis of first appearances of selected small and large mammal taxa the chronology of the lower boundaries of each unit had been established mostly after the significant magnetobiostratigraphic framework developed in the last decade in a number of spanish basins ebro calatayud daroca valles penedes teruel fortuna cabriel and guadix baza in the case of the early and middle miocene particularly mn 1 mn 2 and mn 3 the authors have also taken into account the magnetobiostratigraphic framework developed in the north alpine foreland basin some alternative correlations of the magnetostratigraphic data from this last basin are proposed in order to achieve a higher degree of consistence with the data from the iberian basins a quite well established magnetostratigraphic calibration of the mn boundaries can be proposed for most of the neogene from middle miocene to late pliocene on the other hand the chronological boundaries of the early miocene mn units are still poorly constrained due to 1 scarcity of well studied continuous thick magnetostratigraphic sections 2 the difficulty in defining the boundaries of the mn zones for this time span due to the relative homogeneity and persistence of the fossil rodent faunas and the absence of significant large mammal dispersal events some of the troubles which arise with the application of the mn units strengthen the need to take into account the palaeobiogeographical meaning of these units and their real suitability to date and correlate through extensive geographic areas

sedimentology of the minoan deep sea tephra layer in the aegean and eastern mediterranean the minoan eruption of santorini resulted in deposition of pyroclastic material over a large area of the aegean sea and eastern mediterranean the eruptive activity commenced with a plinian phase which was followed by a phreatomagmatic phase and ended with numerous pyroclastic flows we present a sedimentological study of the minoan ash deposits found in cores taken throughout the region the cores are divided into three groups 1 those from the sub marine slopes immediately surrounding santorini 2 those from the aegean sea where the topography consists of many steep sided basins and 3 those from the eastern mediterranean where the topography is relatively flat and smooth this last group is designated the distal ash zone the deposits from the aegean sea have been remobilised as turbidity currents grain size distribution analysis reveals that these deposits are bimodal the mdo of the coarse population increasing away from source whilst that of the fine population remains uniform irrespective of distance from source the bimodality is caused by a combination of aggregation of fine particles in ash clouds produced during the last two phases of the eruptive activity and mixing of the coarse plinian and fine phreatomagmatic and co ignimbrite deposits within the turbidity current an unusual feature found in two of the cores is a coarse density sorted layer beneath the bouma a division of several turbidite units this is interpreted as an example of a flow head deposit as described by sparks and wilson 1983 the deposits from the distal ash fall zone are fine grained and unimodal containing phreatomagmatic and co ignimbrite material they show only very minor remobilisation of the original air fall ash due to the flat topography of the area the mdo of the deposit remains uniform irrespective of distance from source and is very similar to that of the fine population found in the bimodal aegean deposits this is interpreted as the result of aggregation of fines in the phreatomagmatic and co ignimbrite ash clouds the deposits in both areas have been extensively bioturbated a study of dispersed ash in the cores to reconstruct the original thickness of the ash layers suggests that ash layers less than 0 62 cm thick will be completely dispersed in the surrounding sediment whilst those thicker than 2 5 cm will be preserved as discrete layers the base being unaffected by bioturbation the deposits on the submarine slopes of santorini were not originally deposited as air fall ash but are derived from the erosion of coastal exposures of non welded ignimbrite they form storm sand layers and are typical of the type of deposit that may be formed by rapid erosion of fresh pyroclastic material after the eruption of an island arc volcano

combining geophysical data sets to study the dynamics of shallow evaporites in urban environments application to hamburg germany summary shallowly situated evaporites in built up areas are of relevance for urban and cultural development and hydrological regulation the hazard of sinkholes subrosion depressions and gypsum karst is often difficult to evaluate and may quickly change with anthropogenic influence the geophysical exploration of evaporites in metropolitan areas is often not feasible with active industrial techniques we collect and combine different passive geophysical data as microgravity ambient vibrations deformation and hydrological information to study the roof morphology of shallow evaporites beneath hamburg northern germany the application of a novel gravity inversion technique leads to a 3 d depth model of the salt diapir under study we compare the gravity based depth model to pseudo depths from h v measurements and depth estimates from small scale seismological array data while the general range and trend of the diapir roof is consistent a few anomalous regions are identified where h v pseudo depths indicate shallower structures not observed in gravity or array data these are interpreted by shallow residual caprock floaters and zones of increased porosity the shallow salt structure clearly correlates with a relative subsidence in the order of 2 mm yr 1 the combined interpretation of roof morphology yearly subsidence rates chemical analyses of groundwater and of hydraulic head in aquifers indicates that the salt diapir beneath hamburg is subject to significant ongoing dissolution that may possibly affect subrosion depressions sinkhole distribution and land usage the combined analysis of passive geophysical data may be exemplary for the study of shallow evaporites beneath other urban areas

magnetostratigraphy of the vallesian late miocene in the valles penedes basin northeast spain the magnetostratigraphic analysis of the late miocene continental deposits from the valles penedes basin combined with its well documented fossil mammal record has provided a well resolved chronology for the upper basin infill the study is based on the biostratigraphic and magnetostratigraphic cross correlation of 12 sections throughout the alluvial sequences in the western valles area the biostratigraphic framework consists of 21 mammal localities corresponding to the mammal neogene mn9 and mn10 units the composite magnetic polarity sequence is based on 400 paleomagnetic sites correlation with the geomagnetic polarity time scale gpts has led to an absolute dating of the faunal events and a precise chronostratigraphy of the vallesian mammal stage in its type area the hipparion first appearance datum fad at the mn8mn9 boundary is dated at 11 1 ma in the valles penedes basin this age compared to other radiometrically dated localities in europe north africa and turkey is consistent with an isochronous dispersal of this equid through the mediterranean region a possible isochrony at a larger geographical scale old world mesogea must await more reliable ages of the hipparion fad in asia and africa the cricetulodon fad mn9amn9b boundary is dated to 10 4 ma in chron c5n the progonomys fad mn9mn10 boundary corresponding to the intra vallesian faunal crisis is dated at 9 7 ma c4ar 3r the vallesian spans 2 4 myr from 11 1 ma c5r 1n to 8 7 ma c4an and correlates to the early tortonian

sedimentary geochemistry of manganese implications for the environment of formation of manganiferous black shales the sedimentary geochemistry of manganese is dominated by the redox control of its speciation higher oxidation states mn super 3 and super 4 occurring as insoluble oxyhydroxides in well oxygenated environments and the lower oxidation state mn super 2 being much more soluble in oxygen deficient settings its geochemical behavior is therefore quite different in oxic and anoxic environments and where oxic and anoxic conditions are juxtaposed mn is recycled between the two environments in modern marine sediments mn is present above its crustal abundance as an oxyhydroxide in all slowly accumulating pelagic sediments of the deep ocean and in surficial deposits of continental margin environments diagenetic recycling of mn in the latter causes surficial deposits to have larger mn enrichments than in many pelagic sediments bottom sediments of permanently anoxic basins show no enrichments and have mn concentrations that are controlled solely by the aluminosilicate fraction manganese carbonates kutnohorite and calcic rhodochrosite are found only in anoxic sediments accumulating beneath surface oxic horizons and therefore under oxygenated bottom waters in many nearshore environments such enrichments are due to delivery of mn by burial of surface oxyhydroxides into the subsurface anoxic environment where they are dissolved pore water mn levels can reach saturation with respect to a mixed mn ca carbonate phase in such sediments the diagenetic origin for these phases is shown by their carbon isotope compositions which typically indicate a carbon source from decomposing organic matter the presence of mn carbonates therefore signifies that the host sediment must have accumulated under oxygenated bottom waters on the basis of this information it is proposed that in contrast to several current explanations for the formation of mn carbonates kutnohorite and rhodochrosite in ancient organic rich shales limestone and marl sequences and in many mn ore deposits the occurrence of these mineral phases indicates that the sediments originally accumulated beneath oxygenated bottom waters by analogy with the present mn carbonates could not have formed in the bottom waters of anoxic basins these diagenetic phases however did form where mn was supplied at a high rate namely by the burial of oxyhydroxide enriched surface sediments to a subsurface anoxic environment this situation could only have occurred under oxygenated bottom waters the presence of mn carbonates in ancient black shales and in some carbonate rich rocks lends strong support to the notion that these rocks did not necessarily form in anoxic basins but owe their carbon richness to a high supply of organic matter to sediments deposited under oxygenated bottom waters probably in continental margin settings

paleogene neogene depositional history of the middle u s atlantic continental rise mixed turbidite and contourite depositional systems abstract the construction of the middle u s atlantic continental rise from late paleogene to late pliocene time included downslope sediment gravity flows and alongslope contourite deposition some previous studies have suggested that contour following bottom currents were the dominant control on depositional patterns depositional relief from two large contourite drifts largely built in late miocene to late pliocene time continue to dominate present day lower rise morphology detailed seismic sequence mapping presented here suggests that significant turbidite fan systems also were active and are preserved in the stratigraphic section a single thick depositional sequence is mapped for oligocene to middle miocene sediments deposited when inferred fan systems off the norfolk washington canyons were reworked by bottom currents along the lower rise to form the proto hatteras outer ridge detailed mapping of three late miocene to late pliocene depositional sequences indicates that fan channel systems were active at the same time large contourite drifts were being constructed sediment delivered to the lower rise by these elongate turbidite systems undoubtedly was an important local source for construction of the hatteras outer ridge and through entrainment and resuspension was an important source for regional contourite deposition controlled by the deep western boundary undercurrent we suggest that submarine fans and current controlled sediment drifts may develop simultaneously as companion systems types of fan drift interaction include current only modification of fans transitional fan to drift and adjacent or overlapping submarine fan and sediment drift deposition

variation in biogenic and detrital fluxes and formation of laminae in late quaternary sediments from the peruvian coastal upwelling zone abstract studies of laminated sediments from the peru margin using back scattered electron imagery bsei provide a high resolution record of variation in detrital and biogenic fluxes and highlight the uncertainty involved in preserving a record of surface processes in bottom sediments intermittently laminated sediments which predominate in the peru forearc basins record episodic major diatom bloom events from which there was adequate flux to counteract water column processes of dissolution and comminution a distinctive sub millimetre lamination with a limited occurrence during isotope stage 5 comprises a regular alternation between silt rich and clay rich couplets which may represent annual deposition with irregularly interlaminated diatom ooze containing near monospecific bloom assemblages the absence of diatom ooze layers between silt clay couplets may be controlled by variation of either the intensity of upwelling and or the nutrient content of upwelled waters macroscopically obvious 0 5 3 cm thick pelleted or homogeneous zones which occur throughout the sub millimetre laminated sequence represent periods of increased oxygenation with a probable 8 16 year duration occurring at irregular intervals of a few years to a few hundred years a slight but pervasive microscopic bioturbation is common within laminated intervals which would macroscopically be described as anaerobic sediments

fossil contourites a critical review abstract despite three decades of study there is still great controversy over the recognition and interpretation of fossil contourites exposed in ancient series on land in order to best examine this problem we briefly review the evidence from modern systems including the many examples of cenozoic contourites that have been recovered from dsdp odp drilling on major drifts in the present day oceans the range of contourite facies described from both deep water 2000 m and mid water 300 2000 m drifts are mostly fine grained bioturbated and homogeneous often with a distinct bedding cyclicity and with some coarser grained sandy contourites developed under higher energy bottom currents there are also a number of current controlled sediment bodies that have formed in outer shelf upper slope settings 50 300 m under the influence of counter currents underflows and major surface currents these are not considered contourites sensu stricto but may be mistaken as such in ancient examples the most commonly described fossil contourites in the literature have been interpreted by the authors concerned as bottom current reworked turbidites however a critical review suggests that these are the facies most subject to misinterpretation and many of the sediments claimed as fossil contourites are almost certainly fine grained turbidites whereas others were more likely formed under outer shelf upper slope current systems there remain very few ancient examples that are more closely comparable to modern contourites these include the cretaceous talme yafe formation in israel the ordovician jiuxi drift in china and parts of the paleogene lefkara formation cyprus and the neogene misaki formation in japan we present a set of possible criteria for the recognition of fossil contourites and bottom current reworked turbidites

gravity interpretation of nonoutcropping sedimentary basins in which the density contrast decreases parabolically with depth the decrease in density contrast of sedimentary rocks with depth in many sedimentary basins can be approximated by a parabolic density function analytical gravity expression of an outcropping two dimensional vertical step along which the density contrast decreases parabolically with depth is derived in the space domain a modification ofbott s 1960 method of gravity interpretation is proposed by considering two outcropping vertical steps on either side of the first and last observation points in addition ton outcropping vertical prisms in order to interpret the gravity anomalies of nonoutcropping basins the thicknesses of the two outcropping vertical steps are made equal to the thicknesses of the two outcropping vertical prisms placed below the first and last observation points the initial depth estimates of the sedimentary basin are calculated by the infinite slab formula ofvisweswara raoet al 1993 the gravity effects of then outcropping prisms and the two outcropping vertical steps are calculated at each anomaly point and the depth to the floor of the basin are adjusted based on the differences between the observed and calculated anomalies a gravity anomaly profile of los angeles basin california is interpreted

late quaternary sedimentary processes and variations in bottom current activity in the ulleung interplain gap east sea korea abstract a detailed facies analysis of core sediments from the ulleung interplain gap uig reveals ten sedimentary facies which reflect a variety of sedimentary processes volcaniclastic high concentration sediment gravity flows low density turbidity currents pelagic settling under either well or poorly oxygenated bottom water conditions marine fallout of tephra hampered sedimentation by bottom currents top truncation of turbidites by bottom current reworking and mn carbonate precipitation under changing bottom water oxygenation states distribution of the facies in the cores integrated with echo characters of high resolution subbottom profiles delineates spatial and temporal changes in sedimentary processes influenced by variations in bottom current activity during the late quaternary the glacial 15 ka sediment units from the ulleung interplain channel uic an erosional axial channel system in the uig consist mainly of manganiferous and muddy contourites interbedded with coarse grained volcaniclastic turbidites or debrites and non bioturbated pelagites this indicates prevalent activity of bottom currents rarely interrupted by volcaniclastic high concentration sediment gravity flows and deep water stagnations which resulted in anoxic bottom water conditions on the other hand the glacial units of the southeastern margin of the uic where upslope migrating sediment waves developed are generally dominated by alternating fine grained turbidites and bioturbated or non bioturbated pelagites this suggests that frequent turbidity currents derived from upslope mass wasting were responsible for the generation of the sediment waves the post glacial

dating the northern deposits of the ebro foreland basin implications for the kinematics of the sw pyrenean front abstract dating the sedimentary infill of the northern margin of the ebro foreland basin informs about the orogen basin evolution a magnetostratigraphic section of 5 km thick combines new magnetostratigraphic results from the syntectonic alluvial uncastillo fm upper oligocene lower miocene 1 km thick the fuencalderas section with previous 3 3 km thick and new 0 7 km thick magnetostratigraphic data from the underlying fluvial campodarbe fm luesia and san marzal sections eocene oligocene this composite section allows dating the entire basin infill in this sector therefore bracketing the timing of the deformation in the southern margin of the pyrenees after considering previous kinematic studies deformation recorded by the continental deposits spans from syn gavarnie nappe activity broto and fiscal basement thrust sheets from 31 3 to 24 55 ma rupelian chattian oligocene to the syn guarga thrust activity from 24 55 to 21 2 ma chattian aquitanian oligocene miocene the accumulation rates vary from ca 22 to ca 39 cm kyr between the genetic stratigraphic units in the uncastillo fm through the section these rates are close to those of the underlying deposits of the campodarbe fm average of ca 36 cm kyr deformation for the latest pyrenean front syn guarga thrust is younger than previously assigned in 5 4 1 5 and 1 1 myr of the beginning of the punta comun thrust sheet from 29 4 ma to 24 ma lower riglos thrust sheet system from 24 to 22 5 ma and the upper riglos thrust system 22 5 to 21 4 ma respectively other significant changes in accumulation rate and its derivative also indicate variations in the tectonic activity ca 33 and 28 ma

determination of the crustal and thermal structure of the erzurum horasan pasinler basins eastern turkiye using gravity and magnetic data the erzurum horasan pasinler basin which surrounds miocene rocks is oriented approximately e w and is located in eastern anatolia turkiye east anatolia where ophiolitic and young volcanic rocks are widespread is situated in the alpine himalayan fold thrust fault belt the nw se trending north anatolian transform fault zone and the ne sw trending east anatolian transform fault zone formed by the compressional regime of east anatolia control the main tectonics of the study region while the moho and conrad depths of the study region are 43 0 and 20 9 km respectively the average sedimentary thickness has been determined to be 5 2 km by using the power spectrum method on the other hand it is found that the depth of the moho in the region varies from 41 0 to 44 5 km and the depth of the conrad discontinuity varies between 22 and 26 km as computed using empirical equations the basement of the sedimentary layer is calculated to be 6 km by using inversion results applied to the residual gravity data the curie point depth and average heat flow value in this region are calculated as 18 0 km and 89 1 m wm 2 respectively geotherm calculations reveal that the moho temperature is 1 028 0 c based on the crustal model the high heat flow values obtained are attributed to tectonic activities and melting of the lithospheric mantle caused by upwelling of the asthenosphere

late quaternary sedimentation in the ulleung interplain gap east sea korea the ulleung interplain gap uig is a deep 2300 2700 m passage which has served as a conduit for deep water circulation between the ulleung and japan basins a detailed analysis of chirp 2 7 khz subbottom profiles ca 6270 linekm and nine sediment cores 8 6 11 4 m long together with age data of tephra layers and four ams 14 c from the uig and the adjacent areas reveals complex sedimentation caused by an interaction between bottom currents and mass flows during the lastand post glacial periods from high resolution subbottom data rock basement slide slump rock fall deposits mass flow chutes channels mass flow deposits bottom current deposits and a large scale bottom current channel system are recognized core sediments consist of various deposits of turbidites muddy contourites manganiferous contourites and pelagic hemipelagic sediments based on vertical distribution of sedimentary facies together with a chronostratigraphic framework core sediments can be divided into units i f15 ka the extensive mass flow deposits with slope failures on the entire slopes of topographic highs around the uig and the dominant turbidites in unit ii f15 ka suggest that a relatively large amount of sediment was delivered into the uig by frequent mass flows recurrence intervals of ca 250 500 years in the upper unit ii during the last glacial period erosion or hampered sedimentation by bottom currents is indicated by the truncated reflectors of channel walls and muddy manganiferous contourites in the ulleung interplain channel uic along the uig interbedded turbidites in the uic floor reflect that some large scale mass flows intermittently entered into the uic the uic has an asymmetric channel flank geometry the southeastern flank shows a gentle wide mound morphology of mass flow deposits derived from large scale slope failures on the slopes of the oki bank reflecting a dominance of downslope gravitational processes over alongslope bottom currents in contrast the northwestern flank is characterized by a narrow steep geometry of mass flow deposits where a relatively small amount of sediment derived from the slopes of the south korea plateau could not overcome bottom current activity the dominant muddy and manganiferous contourites with rare turbidites in unit i f15 ka reflect intensified bottom currents and infrequent slope failures recurrence intervals of ca 1700 5000 years during the post glacial period these

discrimination of sediment provenance using rare earth elements in the ulleung basin east japan sea abstract in order to discriminate the origins of ulleung basin east japan sea sediments using rare earth elements rees sediments from 15 box cores and one piston core collected in the shelf slope and basin were analyzed for major elements al fe ca and mn and rees the major sedimentary components in this basin were presumed to be detrital materials from land even in the basin sediments based on al and organic contents carbon and opal post depositional recycling processes involving fe and mn were identified in the basin sediments thus the ce anomaly and the fractionation factors of light rees lrees and middle rees mrees relative to heavy rees hrees could not be used as provenance indicators in the deep basin sediments 2000 m of water depth based on a feasibility check using their covariation with fe and mn for the shelf slope and basin b sites near islands water depths of 1200 1800 m regions the eu anomaly lreen hreen and mreen hreen could be successfully used to discriminate possible provenances including nakdong river sediments nrs chinese river sediments crs ulleungdo volcanic rocks uvr and dokdo volcanic rocks dvr from the provenance indicators slope as well as the shelf sediments called the korea strait shelf mud kssm in the ulleung basin can be regarded as mixtures of nrs and crs with decreasing portions of nrs in the kssm with distance from the nakdong river basin b sediments were mixtures of uvr or dvr and crs these findings can be explained if sediments discharged from the nakdong river were transported and deposited kssm northward within the strong coastal front in normal periods and if sediment flumes from summer floods flowed out across the coastal front were carried with the tsushima warm current and then deposited in the slope area this study indicated that crs were very important detrital sediments and that ree compositions can be successfully used as a provenance indicator in even hemipelagic sediments close to land

detailed japan sea paleoceanography during the last 25 kyr constraints from ams dating and δ18o of planktonic foraminifera abstract we have reconstructed paleoceanographic changes in the japan sea for the period from the last glacial maximum lgm to the present using expanded paleoclimate proxy records from two cores together with previously published results from three others a suite of new accelerated mass spectrometer ams 14 c dates provides chronologies that differ from earlier age models and suggest correlation between conditions in the japan sea changes in the north pacific and global sea level and climate changes we present evidence that reduced salinity of the japan sea surface water during the late pleistocene was due primarily to the increased importance of the precipitation evaporation balance at a time when lowered sea level had reduced water exchange with the pacific to a few percent of the present value

a palaeomagnetic analysis of miocene fluvial sediments at pertusa near huesca ebro basin spain the magnetostratigraphy of two logged sections 1 km apart within this system consists of an upper zone of normal polarity and a lower zone of reversed polarity the lithostratigraphy and magnetostratigraphy are parallel the sands and silts are mainly pale yellow brown to dusky yellow and magnetic tests indicate that the magnetization is carried dominantly by ferric oxyhydroxides haematite and goethite the higher temperature natural remanent magnetization is probably due to detrital haematite which would have been partially aligned during fluvial deposition post depositional modification pdrm may have occurred during dewatering haematite pseudomorphing pyrite framboids indicates that early reducing conditions were succeeded by a more oxidizing regime which produced secondary magnetizations associated with fine grained haematite and goethite complete polarity zones are not delineated but the thicknesses present are not excessive compared with other continental miocene deposits the average palaeolatitude of 22 degrees is lower than would be expected for the miocene of northern spain probably due to incomplete averaging of secular variations and other sources of error including possible inclination error modified journal abstract

organic molecular and carbon isotopic records of the japan sea over the past 30 kyr the organic and isotopic geochemical study of two sediment cores kh 79 3 l 3 and kh 79 3 c 3 from the oki ridge in the japan sea has revealed that total organic carbon toc mass accumulation rates are extremely high in the 12 11 ka calendar age interval and toc in the sections in the 24 17 ka interval is depleted in 13c by 3 5 relative to holocene sediments alkenone sea surface temperature sst shows a decrease from 18 to 14 c from 17 5 to 11 6 ka and a sharp increase from 14 to 19 c from 11 6 to 11 1 ka the sst changes are associated with the inflow of cold seawater with the vertical water mixing and the inflowof warm tsushima current into the japan sea the 13c values for both 24 methylcholesta 5 22 dien 3 ol diatom marker and dinosterol dinoflagellate marker are at their minimum from 24 to 17 ka while those for long chain alkenones are not the theoretical considerations on 13c for biomarkers suggest low photosynthetic carbon demand of diatoms and dinoflagellates from 24 to 17 ka

primary or secondary distal volcaniclastic turbidites how to make the distinction an example from the miocene of new zealand mahia peninsula north island abstract miocene marine volcaniclastic deposits occur in mahia peninsula north island new zealand and were sedimented in a forearc setting related to the hikurangi trench subduction system these deposits are interbedded with hemipelagic marls and correspond to simple or amalgamated centimetric to metric thick turbiditic sequences volcaniclastic material is mainly composed of vitric particles with crystals quartz plagioclase with minor biotite amphibole pyroxene and oxides which are well represented in the coarse grained fraction the glass shards are mainly rhyolitic in composition three types of volcaniclastic turbidites were distinguished with geochemical data because distinction is impossible on sedimentary characteristics 1 primary monomagmatic turbidites contain both magmatic bubble wall pumice and shards and phreatomagmatic blocky shards with few vesicles and hydroclastically fragmented pyroclasts vitric particles the chemical compositions of the vitric particles and the crystals are very homogeneous suggesting a cogenetic origin these turbidites directly result from unique eruptive events and are probably related to the entrance of hot subaerial pyroclastic flows into the sea which also led to their transformation into subaqueous gravity flows 2 secondary monomagmatic turbidites never contain phreatomagmatic pyroclasts and the glass compositions display a trend from andesites to rhyolites there is a strong linear correlation in the compositions that suggest that the glass particles are derived from the same magma crystals also show a compositional homogeneity these deposits reflect the succession of several eruptions related to a unique magmatic system and result of the reworking of volcaniclastic material after relatively short storage on the shelf 3 secondary multimagmatic turbidites do not display compositional homogeneity of their vitric and mineral components this implies that the volcaniclastic material has been stored during a relative long period on the shelf before remobilization and that this sedimentation records the volcanic activity of multiple magmatic sources consequently it has been possible to distinguish primary volcaniclastic turbidites that are directly related to the volcanic activity from secondary turbidites that result from reworking of previously deposited material on the shelf monomagmatic turbidites can be used as stratigraphic and magmatic markers whereas multimagmatic cannot multimagmatic turbidites however record the evolution of the volcanic arc during longer periods this leads to the conclusion that the mahia peninsula volcaniclastic turbidites distally record the evolution of the source volcanic arc

environmental and engineering problems of karst geology in china karst terrane is generally regarded as a fragile and vulnerable environment its underground drainage system can aggrevate both drought and flood problems the lack of filtration in an underground conduit makes waste disposal more difficult and the lack of soil cover in bare karstland can enhance deforestation moreover karst terranes are quite often haunted by a series of engineering problems such as water gushing into mines or transportation tunnels leakage from reservoirs and failure of building foundations in china there are more than 200 cases of karst collapse which include many thousands of individual collapse points some of these are paleo and natural collapses but most of them are modern collapses induced by human activities and they have caused serious damage many factors such as geologic structure overburden thickness and character lithologic features of karstified rock and intensity of karstification are related to development and distribution of modern collapses however china s karst is mainly developed in pre triassic old phase hard compact carbonate rock consequently most modern collapses have occurred only in the overlying soil so it is understandable that the fluctuation of the water table in the underlying karstified strata plays an important role in the process of collapse nevertheless there are different explanations as to how the groundwater activities can induce collapse

parabolic density function in sedimentary basin modelling for modelling sedimentary basins of large thickness from their gravity anomalies the concept of parabolic density function which explains the variation of true density contrast of the sediments with depth in such basins is introduced inbott s 1960 procedure the analytical expression the gravity anomaly of a two dimensional vertical prism with parabolic density contrast needed to estimate the gravity effect of the basin in modelling procedure is derived in a closed form two profiles of gravity anomalies one across san jacinto graben california and the other across tucson basin arizona where the density of sediments is found to vary with depth are interpreted

influence of particle aggregation on deposition of distal tephra from the may 18 1980 eruption of mount st helens volcano the may 18 1980 eruption of mount st helens msh produced an extensive ashfall deposit in washington idaho and montana with a minumum volume of 0 55 km3 tephra an unusual feature of the deposit is the occurrence of a second thickness maximum 325 km ene of msh near ritzville washington grain size and component abundance analysis of samples along the main dispersal axis indicates that ash in this region is very fine grained mean size 22 m poorly sorted polymodal and rich in glass shards and pumice fragments a computer simulation of ash fallout from an atmospherically dispersed eruption plume was developed to evaluate various hypotheses for the origin of the distal ash characteristics particularly the thickness versus distance relationship the model was constrained by observations of the eruption column height elevation of major ash transport lateral spreading of the eruption plume and atmospheric wind structure in the vicinity of msh results of different simulations indicate that the second thickness maximum cannot be attributed to either decreased wind velocities over central washington or injection of fine ash above the horizontal wind velocity maximum near the tropopause for the model to fit the observed characteristics of the deposit significant particle aggregation of ash finer than 63 m must be invoked the best fit occurs when ash less than 63 m is aggregated into particles several hundred microns in diameter with a settling velocity of 0 35 m s support for this process comes from the observation and collection of fragile ash clusters of similar size which fell at pullman washington during the may 18 eruption sorem 1982 the premature fallout of fine ash as particle aggregates is a fundamental process in the origin of the grain size characteristics variations in component abundances and thickness versus distance relationship of the may 18 msh ash fall deposit

subaqueous pyroclastic flows and ignimbrites an assessment an assessment of the literature on subaqueous pyroclastic flows and their deposits shows that the term pyroclastic flow is frequently used loosely to describe primary hot gas rich pyroclastic flows mass flows which resulted from the transformation of gassupported flows into water supported ones and secondary mass flows carrying redeposited pyroclastic debris based on subaerial pyroclastic flows the term pyroclastic flow should be restricted to demonstrably hot gas rich mass flows of pyroclastic debris using this definition very few examples of subaqueous pyroclastic deposits with evidence for hot emplacement and of having been wholly submerged have been described in the majority of these cases the evidence for a hot state of emplacement and for the subaqueous nature of the host depositional environment is inadequate the only unequivocal cases of hot pyroclastic flow deposits with adequate supporting evidence are the ordovician nearshore shallow marine ignimbrites of ireland and wales and miocene ignimbrites of southwest japan resulting from the passage of subaerially erupted pyroclastic flows into shallow water other possible examples are near vent dense clast deposits in the donzurobo formation of japan possible submarine intra caldera ponded ignimbrite successions in california and wales and near vent pumiceous deposits of ramsay island wales all other purported cases are either clearly the result of water supported mass flow transportation and deposition debris avalanches debris flows turbidity currents or lack adequate supporting evidence regarding the heat state or the palaeoenvironment only the shallow marine ignimbrites of ireland and wales show adequate evidence of welding but even these could have been nearly wholly exposed above sea level when welding occurred we conclude that when pyroclastic flows enter water they are generally disrupted explosively and or ingest water and transform into water supported mass flows and we suggest the various scenarios in which this occurs there is no evidence to suggest that welding in wholly subaqueous environments is common

correlating the eocene oligocene mammalian biochronological scale from sw europe with the marine magnetic anomaly sequence magnetostratigraphic studies have been undertaken on sedimentary continental formations from western france and spain which have yielded palaeogene mammals the results obtained provide new constraints on the chronological distribution of the mammalian reference levels a magnetozone sequence associated with the reference levels is defined the correlation of this sequence with the geomagnetic polarity time scale is proposed this correlation links the late mid eocene to oligocene mammalian biochronological scale from western europe to other stratigraphic scales a numerical calibration of the palaeogene polarity sequence is made taking into account recent radiometric dating the equations to convert the ages proposed by several authors are given

zoned facies of mass flow deposits in the ulleung tsushima basin east sea sea of japan abstract high resolution 3 5 khz reflection profiles in the ulleung tsushima basin made it possible to classify the uppermost ca 50 m thick sedimentary deposits into rock fall slide slump debris flow deposit debrite and turbidite in terms of their acoustic properties these deposits generally occur in a distinctive zonal facies slides and slumps on the slope debrites on the base of slope and turbidites on the basin floor the rock fall deposits occur along the bases of the korea plateau and ulleung and dok islands the zonal distribution of mass flow deposits suggests that they most likely are derived from a line source at the shelfbreak shelf sediments prograde toward the shelfbreak on the slope sediment masses move downslope mainly accompanied by progressive slumping upslope individual slides and slumps on the slope probably develop into debris flows on the base of slope and successively into turbidity currents on the basin floor mass flow processes on the ulleung basin slope played an important role in transporting a large volume of terrigenous sediments into the deep basin

coal deposition in carbonate rich shallow lacustrine systems the calaf and mequinenza sequences oligocene eastern ebro basin ne spain two main coal bearing sequences developed during the oligocene in the tertiary ebro basin the calaf early oligocene and mequinenza late oligocene coal basins coal deposition took place in shallow marsh swamp lake complexes which sometimes became closed and evolved under warm climatic conditions with fluctuating humidity these shallow lacustrine systems are closely interrelated with the terminal parts of the distributive fluvial systems which spread from the tectonically active ebro basin margins laterally extensive lignite bearing sequences including rather thin lenticular autochthonous and or hypautochthonous coal seams with high ash and sulphur contents characterized coal deposition in the shallow lacustrine systems coal seam geometry which makes them nearly subeconomic resulted from the tectonic instability during basin margin evolution and the sometimes closed arid conditions under which the lacustrine systems evolved high ash and sulphur contents resulted from the inadequate isolation of peat forming environments from clastic influx and from the very low acidity and sometimes high sulphate contents of the lacustrine waters coal exploration in shallow lacustrine sequences similar to those described here must take into account that the spread of coal forming environments and maxima of coal deposition are usually coincident with lake expansions and retraction or shifting of the terminal fluvial zones interrelated with the lacustrine areas

a 36 kyr geochemical record from the sea of japan of organic matter flux variations and changes in intermediate water oxygen concentrations intervals of organic c and carbonate rich laminated sediments occur in the sea of japan with roughly the same frequency as temperature changes observed in greenland ice cores providing clear evidence of rapid oceanographic change during the past 36 kyr planktonic foraminiferal 18o data suggest that only the laminated sediments deposited during the last glacial maximum lgm and perhaps one other interval formed during a period of increased water column stratification sedimentary re and mo data are consistent with bottom waters that were sulfidic during the lgm and suboxic during other laminated intervals results of a numerical model of corg and re burial are consistent with a mechanism whereby an increased corg flux to the seafloor drove oxygen concentrations toward depletion during times of deposition of the suboxic laminated intervals such a process could have resulted from increased upwelling driven either by increased deep water formation due to colder and or more saline surface waters or by stronger northeasterly monsoonal winds

sedimentology of the krakatau 1883 submarine pyroclastic deposits the majority of tephra generated during the paroxysmal 1883 eruption of krakatau volcano indonesia was deposited in the sea within a 15 km radius of the caldera two syneruptive pyroclastic facies have been recovered in scuba cores which sampled the 1883 subaqueous pyroclastic deposit the most commonly recovered facies is a massive textured poorly sorted mixture of pumice and lithic lapilli to block sized fragments set in a silty to sandy ash matrix this facies is indistinguishable from the 1883 subaerial pyroclastic flow deposits preserved on the krakatau islands on the basis of grain size and component abundances a less common facies consists of well sorted planarlaminated to low angle cross bedded vitric enriched silty ash entrance of subaerial pyroclastic flows into the sea resulted in subaqueous deposition of the massive facies primarily by deceleration and sinking of highly concentrated deflated components of pyroclastic flows as they traveled over water the basal component of the deposit suggests no mixing with seawater as inferred from retention of the fine ash fraction high temperature of emplacement and lack of traction structures and no significant hydraulic sorting of components the laminated facies was most likely deposited from low concentration pyroclastic density currents generated by shear along the boundary between the submarine pyroclastic flows and seawater the krakatau deposits are the first well documented example of true submarine pyroclastic flow deposition from a modern eruption and thus constitute an important analog for the interpretation of ancient sequences where subaqueous deposition has been inferred based on the facies characteristics of encapsulating sedimentary sequences

alluvial dolines in the central ebro basin spain a spatial and developmental hazard analysis abstract alluvial dolines are abundant in quaternary terraces and pediments overlying neogene gypsum in the zaragoza area central ebro basin spatial analysis and experimental simulation show that sulphate content in the groundwater grain size of the detrital cover topography of the tertiary quaternary boundary annual variation of the water table and thickness of the detrital cover are the main factors controlling their development taking into account these variables a theoretical spatial hazard model has been elaborated expressed as a mathematical equation and a hazard map both experiments and field data show a high correspondance between two basic mechanisms of evacuation and subsidence dragging slow subsidence and collapse of cavities and two basic types of morphology and internal structure of dolines basin doline funnel structure and well doline vault structures respectively a genetic classification of dolines and some evolutionary patterns based on these criteria are developed historical changes observed in doline distribution as well as field surveys of urban damage and microtopographic profiles allow us to evaluate the present day activity of dolines local subsidence rates measured in urban areas range from 2 5 to 10 cm year although doline generation and reactivation in the whole area tend to be compensated by filling by human activity

land ocean linkages over orbital and millennial timescales recorded in late quaternary sediments of the japan sea late quaternary sediments of the japan sea are characterized by centimeter to meter scale alternations of dark and light layers which are synchronous basinwide high resolution analyses of the sediments from ocean drilling program site 797 reveal that deposition of the meter scale alternations reflect variations in paleoceanographic conditions which were closely associated with glacio eustatic sea level changes through the modulation of the volume and character of the influx to the sea through the tsushima strait the centimeter to decimeter scale alternations reflect millennial scale variations which are possibly associated with dansgaard oeschger d o cycles with each dark layer appearing to correspond to an interstadial this variability is attributed to the development of a humid climate in central to eastern asia and the consequent increase in discharge from the huanghe and changjiang rivers during interstadials this caused expansion of the east china sea coastal water ecscw which penetrated more strongly into the japan sea the increased influence of the lower salinity nutrient enriched ecscw reduced deep water ventilation and enhanced the surface productivity leading to the development of anoxic bottom waters and deposition of the dark layers thus the centimeter to decimeter scale alternations of the dark and light layers record wet and dry cycles in central to eastern asia possibly associated with d o cycles

mapping subsurface karst features with gpr results and limitations ground penetrating radar gpr has been applied with relative success to locate paleo collapses and cavities and to detect and characterise karst one of its main advantages is that while the penetration depth is limited to several tens of meters or even just several meters the obtained resolution can be in the scale of centimeters in this paper we illustrate the applicability of gpr prospecting to the study of alluvial karst and the structures associated with subsidence areas gpr radargrams obtained with two central frequency antennas 50 and 100 mhz are balanced against direct observation of geological features of collapse structures in vertical exposures of gravel quarries gpr surveys offer the possibility of obtaining nearly continuous vertical cross sections of the subsoil and integration of data within a 3d frame however the study of the internal structure of the subsoil by means of the gpr profiles has been usually neglected in this work we show that some hints about the evolution of individual dolines can be established from the study of the geometry of the sedimentary filling by means of gpr the obtained results indicate that gpr allows to characterise the structures associated with karst features and can therefore be useful evaluating hazard susceptibility in doline fields because 1 when no surface evidences exists it permits the detection of karst hazards in the subsoil and 2 when surficial evidences of karst activity are present it permits the characterisation of processes associated with subsidence

natural and human induced sinkholes in gypsum terrain and associated environmental problems in ne spain the central ebro basin comprises thick evaporite materials whose high solubility produces typically karstic landforms the sinkhole morphology developed in the overlying alluvium has been studied using gravimetry and ground penetrating radar gpr on stream terraces as well as analyzing the evolution of sinkhole morphologies observed in aerial photographs taken in 1928 1957 and 1985 the sinkhole morphologies give some idea of possible subsurface processes as well as an indication of the final mechanisms involve in sinkhole development on stream terraces and cover pediments the most commonly encountered dolines are bowl shaped in their morphology with both diffuse and scarped edges in contrast dolines developed in the gypsiferous silt infilled valleys have a funnel and well shaped morphology the diffuse edged bowl shaped dolines are developed through the progressive subsidence of the alluvial cover due to washing down of alluvial particles through small voids and cracks into deeper subsurface caves resulting in a decrease alluvial density future compaction of the alluvial cover will produce surface subsidences this type of dolines are associated with negative gravity anomalies in contrast the scarped edge dolines are formed by the sudden collapse of a cavity roof the cavities and cracks formed in the gypsum karst may migrate to the surface through the alluvial deposits by piping and they may subsequently collapse in this instance the cavities can be detected by both gravity and gpr anomalies where the voids are not deeper than 4 5 m from the surface these processes forming sinkholes can be enhanced by man induced changes in the groundwater hydrologic regime by both inflows due to irrigation ditch losses or pipe leakages and by outflows from pumping activities

gypsum karst problems in constructing dams in the usa gypsum is a highly soluble rock and is dissolved readily to form caves sinkholes disappearing streams and other karst features that typically are also present in limestones and dolomites gypsum karst is widespread in the usa and has caused problems at several sites where dams were built or where dam construction was considered gypsum karst is present at least locally in most areas where gypsum crops out or is less than 30 60 m below the land surface these karst features can compromise on the ability of a dam to hold water in a reservoir and can even cause collapse of a dam gypsum karst in the abutments or foundation of a dam can allow water to pass through around or under a dam and solution channels can enlarge quickly once water starts flowing through such a karst system the common procedure for controlling gypsum karst beneath the dam is a deep cut off trench backfilled with impermeable material or a close spaced grout curtain that hopefully will fill all cavities in oklahoma the proposed upper mangum dam was abandoned before construction because of extensive gypsum karst in the abutments and impoundment area catastrophic failure of the quail creek dike in southwest utah in 1989 was due to flow of water through an undetected karstified gypsum unit beneath the earth fill embankment the dike was rebuilt at a cost of us 12 million with construction of a cut off trench 600 m long and 25 m deep other dams in the usa with severe gypsum karst leakage problems in recent years are horsetooth and carter lake dams in colorado and anchor dam in wyoming

late oligocene early miocene paleosols of distal fluvial systems ebro basin spain abstract the study of paleosols can be a vital tool in the paleoenvironmental interpretation of continental deposits because their physical and chemical characteristics are a reflection of variations in aspects of soil formation changes in paleosol characteristics can be used to determine the architecture and nature of parent material paleosol maturity topography climate and soil forming organisms including vegetation cover on the ancient floodplain and can be utilized to recreate a palaeocatena furthermore paleosols can provide quantitative data on paleoclimate where other sources such as organic matter and pedogenic carbonate are absent late oligocene early miocene strata exposed in the ebro basin spain have been identified as proximal alluvial fan fluvial and lacustrine continental facies in parts of the distal fluvial system pedogenically altered channel and overbank deposits interfinger with ephemeral lacustrine facies three main paleosol types developed in these sediments and have been described and compared to modern soils entisol like early successional soils inceptisol like young soils and alfisol like open woodland soils paleoenvironmental reconstructions suggest a mosaic of ecotypes with areas of open woodland composed of shrubs herbs and small trees and other plants of low stature and with each ecotype being controlled primarily by fluctuating paleohydrological conditions from field observations and geochemical analysis the climate was found to be humid continental mean annual temperature mat 10 14 c 4 c mean annual precipitation map 450 830 mm yr 1 200 mm yr 1 these results indicate that climatic conditions were wetter than the present day ebro basin mat 14 c map 320 mm yr 1 and differ from previous interpretations of an arid to semi arid environment based on sedimentological criteria alone

sea level surface salinity of the japan sea and the younger dryas event in the northwestern pacific ocean abstract the japan sea was profoundly different during glacial times than today available 18 o evidence indicates that sea surface salinity was lower by several per mil this probably increased the stability of the water column and caused anoxic sedimentary conditions in the deep sea as shown by the absence of benthic microfossils and the presence of laminated sediment these changes are likely related to the effects of late quaternary sea level change on the shallow sills ca 130 m across which the japan sea exchanges with the open ocean the hwang he yellow river has previously been implicated as the source of fresh water to the japan sea during glaciation but the possible roles of the amur river and excess precipitation over evaporation must also be considered ambiguous radiocarbon chronologies for the latest quaternary of japan sea cores do not adequately constrain the timing of salinity lowering previous studies have suggested that lowest sea surface salinity was achieved 27 000 to 20 000 14 c yr b p however if global sea level fall restricted exchange with the open ocean circulation then lowest salinity in the japan sea may have occurred as recently as 15 000 to 20 000 yr ago when sea level was lowest if this alternative is correct then as sea level abruptly rose about 12 000 yr ago relatively fresh water must have been discharged to the open pacific this might have affected the dynamics of outflow local faunal and floral expression of the polar front and stable isotope ratios in foraminifera these environmental changes could be misinterpreted as evidence for the cooling of younger dryas age which has not been identified in nearby terrestrial records

bottom current controlled sedimentation a synthesis of the contourite problem abstract an overview of the main items concerning deep bottom current controlled deposits is presented these include the definition of contourites their processes of deposition and facies characteristics contourite drift types and seismic patterns the interplay of turbidity and bottom current processes and the correlation between bottom current processes and global changes in climate sea level from this discussion several of the more significant problems are highlighted which we believe should be priority targets for future research 1 identification of contourites especially in ancient series where they are interbedded with turbidites and other facies 2 refinement of the numerous parameters used as tracers of palaeocirculation patterns 3 understanding the interaction between the different types of bottom currents and also between bottom current and other deep water processes 4 distinction in the sedimentary record between the effects of short time scale bottom current variations due to regional causes like benthic storms and geological scale current fluctuations related to climatic or astronomic control 5 understanding the control of glacial interglacial climatic cycles on the nature and rate of contourite deposition