biotic and geochemical response to anoxic events the aptian pelagic succession of the gargano promontory southern italy microfossil distribution patterns and high resolution 13 c and 18 o curves calibrated against planktonic foraminiferal and calcareous nannofossil data are provided for the aptian pelagic coppitella section of the gargano promontory southern italy the succession consists of cyclically arranged couplets of bioturbated grey marlstones and off white marly limestones referable to the marne a fucoidi in the lower portion of the section two thin black shales were recognized the high resolution 13 c curve presented here correlates with those of other alpine tethyan sections albeit with lower absolute values the onset of deposition of organic rich sediments falls at the top of the interval of unchanging carbon isotope values whereas the upper black shale is documented from the interval of the main aptian positive 13 c excursion according to our biostratigraphic data the deposition of organic matter in the gargano promontory persisted through early late aptian boundary time using a chemostratigraphic definition only the lower black shale is referred to the selli level as far as the biotic response is concerned the onset of the nannoconid crisis is recorded considerably below the lower black shale whereas the globigerinelloides eclipse is recorded below and within the upper black shale the distribution of meso eutrophic indices zygodiscus spp radiolaria vs moderate fertility indices rhagodiscus asper and lithraphidites carniolensis testifies to a modest increase of surface water fertility only throughout the stratigraphically higher black shale the occurrence of a benthic foraminiferal fauna albeit impoverished in both the basal and upper black horizons clearly documents dysaerobic rather than completely anoxic conditions on the sea floor relative sea level rise at the time of the selli event in the gargano promontory is documented by drowning and foundering of the apulia platform margin situated adjacent to the basin in which the marne a fucoidi accumulated

the effect of base level changes and geological structures on the location of the groundwater divide as exhibited in the hydrological system between the dead sea and the mediterranean sea summary the effects of base sea or lake level changes on the location and elevation of the groundwater divide were examined in the hydrological system between the mediterranean sea and the dead sea steady state simulations were conducted with a 1 d analytical model and transient conditions were simulated using feflow groundwater modeling software two hydrological scenarios were simulated a a transition to a new steady state following the expected drop of 150 m of the dead sea level and b the time of the precursor of the dead sea lisan lake some 20 000 years ago when the lake level was about 250 m above the present day dead sea level and the mediterranean sea level was 120 m below its present one the results of the simulations show that the dead sea level drop has led to a progressive decline in the groundwater level up to several kilometers inland from the shoreline the hydraulic gradient increases and thus the discharge to the lake also increases at the expense of the storage and also due to a small enlargement of the recharge zone by a 600 m shift of the divide broadly the subsurface hydrological system is compartmentalized into several sections separated by low permeability fold structures bounding the mountainous uplands most of the groundwater recharge occurs in the uplands given this geometry and the available water level measurements analytical and numerical modeling results show that only changes in the dead sea level and recharge rate result in dramatic changes for the scenarios examined limited by the low permeability folds the effects of the dead sea level on the groundwater level are most pronounced in the vicinity of the judea desert lowland the folds also greatly limit migration of the groundwater divide associated with changes in the dead sea level transient simulations show a peak increase of 30 in the dead sea groundwater flux in 75 years resulting from drainage of lowland aquifers after more than 500 years the groundwater flux is expected to return to values no more than 4 higher than at the beginning of the simulation this small net increase is consistent with the small shift in the groundwater divide

the energy source for the coastal trapped waves in the australian coastal experiment region abstract the sea level on the southern australian coast is examined for the source of the coastal trapped wave energy observed during the australian coastal experiment sea level adjusted for atmospheric pressure and atmospheric pressure are observed to propagate eastward at about 10 m s 1 at the lowest frequency examined 24 day period some energy travels south along the west coast of tasmania but does not reach the east coast of mainland australia while some energy travels through bass strait to reach the east coast of mainland australia at the most energetic frequency 8 day period adjusted sea levels are coherent over the 3700 km of coastline from southern australia to the east coast and much of the wind forced coastal trapped wave energy appears to travel through bass strait to the mainland east coast we have not identified a mechanism for energy transfer through bass strait and we do not know what fraction of the coastal trapped wave energy incident on western bass strait actually reach

architecture and evolution of a fjord head delta western vancouver island british columbia the architectural framework and holocene evolution of the zeballos fjord head delta on west central vancouver island was established through a multidisciplinary field based study the zeballos delta is a composite feature consisting of an elevated incised late pleistocene delta and an inset holocene delta graded to present sea level both deltas have a classic gilbert type tripartite architecture with nearly flat topset and bottomset units and an inclined foreset unit time domain electromagnetic tdem and ground penetrating radar gpr surveys borehole data and gravel pit exposures provided information on the internal form lithologies and substrate of both deltas both sets of deltaic deposits coarsen upward from silt in the bottomset unit to gravel in the topset unit the tdem survey revealed a highly irregular buried bedrock surface ranging from 20 m to 190 m in depth and it delineated saltwater intrusion into the deltaic sediments late quaternary sea level change at zeballos was inferred from delta morphology and the gpr survey the elevated late pleistocene delta was constructed when the sea was about 21 m higher relative to the land than it is today it was dissected when sea level fell rapidly as a result of glacio isostatic rebound relative sea level reached a position about 20 m below the present datum during the early holocene foreset beds that overlap and progressively climb in a seaward direction and topset beds that thicken to 26 m landward imply that the delta aggraded and prograded into zeballos inlet during the middle and late holocene transgression sea level may have risen above the present datum during the middle holocene creating a delta plain at about 4 m a s l remnants of this surface are preserved along the valley margins copyright 2004 john wiley sons ltd

the dead sea sinkhole hazard geophysical assessment of salt dissolution and collapse abstract a geophysical approach is presented for analyzing processes of subsurface salt dissolution and associated sinkhole hazard along the dead sea the implemented methods include seismic refraction srfr transient electromagnetic method tem electric resistivity tomography ert and ground penetration radar gpr the combination of these methods allows the delineation of the salt layer boundaries estimating its porosity distribution finding cavities within the salt layer and identifying deformations in the overlying sediments this approach is shown to be useful for anticipating the occurrence of specific sinkholes as demonstrated on both shores of the dead sea these sinkholes are observed mainly along the edge of a salt layer deposited during the latest pleistocene when lake lisan receded to later become the dead sea this salt layer is dissolved by aggressive water flowing from adjacent and underlying aquifers which drain to the dead sea sinkhole formation is accelerating today due to the rapid fall of the dead sea levels during the last 30 years caused by anthropogenic use of its water

cenomanian turonian carbon isotope events recorded in terrestrial organic matter from northern japan carbon isotopic fluctuations recorded in terrestrial organic matter from the upper cretaceous cenomanian turonian succession of hokkaido japan show a remarkably similar pattern to isotopic fluctuation in carbonate carbon reported from southern england and the italian apennines chronological correlation for the cenomanian turonian section of japan is based on planktonic foraminiferal biostratigraphy with some additional data from macrofossils allowing a detailed comparison of isotope stratigraphies for japan and europe three distinct features of the isotope profile namely a positive spike near the cenomanian turonian boundary a shoulder in the lower middle turonian and a level segment in the middle upper turonian are observed in japan these features are biostratigraphically comparable and correlative with isotope profiles reported from europe the single factor influencing isotopic composition of both terrestrial organic carbon and marine carbonate carbon is isotopic change in the global co2 reservoir of the ocean atmosphere system if these three carbon isotope features are synchronous they may be inferred as having been caused by global phenomena and as providing global high resolution chemo stratigraphic markers carbon isotope stratigraphy could be an important bridge between terrestrial inland sequences and marine sequences

paleobotanical evidence for near present day levels of atmospheric co2 during part of the tertiary understanding the link between the greenhouse gas carbon dioxide co 2 and earth9s temperature underpins much of paleoclimatology and our predictions of future global warming here we use the inverse relationship between leaf stomatal indices and the partial pressure of co 2 in modern ginkgo biloba and metasequoia glyptostroboides to develop a co 2 reconstruction based on fossil ginkgo and metasequoia cuticles for the middle paleocene to early eocene and middle miocene our reconstruction indicates that co 2 remained between 300 and 450 parts per million by volume for these intervals with the exception of a single high estimate near the paleocene eocene boundary these results suggest that factors in addition to co 2 are required to explain these past intervals of global warmth

geostrophic control with wind forcing application to bass strait abstract a conceptual model of the low frequency flow in a strait of finite length based on the derivation geostrophic control is compared with a more complete model that includes the reflection of kelvin waves at the ends of the strait the low frequency sea level responses of the two models are identical for bass strait the reason for the agreement in straits of width less than one external rossby radius is that the kelvin wave structure is approximately linear over the length and width of the strait the low frequency sea level response can be characterized as follows the pressure forced mode tilts down in the direction of flow and the wind forced mode tilts up in the direction of flow both modes are in geostrophic balance in the cross strait direction

delineation of saltwater intrusion zones using the time domain electromagnetic method the nabeul hammamet coastal aquifer case study ne tunisia the time domain electromagnetic method tdem is applied to monitor to delineate and to map the saltwater intrusion zones in the mediterranean plio quaternary aquifer forty two tdem soundings were carried out in the coastal plain of nabeul hammamet region ne tunisia tdem resistivity data were correlated with the existing borehole logging data to assign them to a particular lithology and to provide information about the position of the freshwater seawater transition zone the geoelectric sections showing the vertical configuration of seawater intrusion with the brackish salty saturated zones have a resistivity ranging from 0 1 to 5 m and are detected at a depth lower than 1 5 m the salinized zones are located at nabeul sidi moussa sidi el mahrsi al gasba and mrazgua and at hammamet touristic zone of hammamet north and south baraket essahel and reached a distance of 4 km from the coastline indicating a severe state for the aquifer in these zones these tdem results are confirmed by the increase of chloride concentration content in the analysed water samples of monitoring wells moreover in the northeastern part the presence of a saltwater front located far from the coast and along the nw se major surface fault can be explained by two hypothesis i this fault seems to provide a conduit for seawater to move readily towards the water wells and ii the clay and gypsum infiltration of marine messinian deposits through the fault plane leads to low resistivities finally it comes out from this study that tdem survey has successfully depicted salinized zones of this coastal aquifer copyright 2012 john wiley sons ltd

correlation of early cretaceous carbon isotope stratigraphy and platform drowning events a possible link the early cretaceous carbonate carbon isotope record is marked by three positive high amplitude 1 5 excursions each covering time spans of more than 106 years they are of late valanginian hauterivian and early and late aptian age in a case study along a transect across the western tethys ocean we identified a coincidence between 13c excursions black shale formation and widespread carbonate platform drowning events we conclude that the 13c excursions reflect a change in partitioning of carbon between the organic and carbonate carbon sinks which was triggered by climate induced ecological changes in cretaceous pelagic and neritic environments episodes of intensified greenhouse climate conditions led to an increase in weathering erosion and runoff rates and to elevated nutrient transfer rates from continents into oceans the resulting increase in oceanic nutrient levels favoured marine phytoplankton production and black shale deposition while conditions for carbonate producing biotas became unfavourable partial choking of carbonate production along river influenced coasts resulted in widespread carbonate platform drowning during times of sea level rise in the valanginian and aptian widespread contemporaneous black shale deposits and drowned carbonate platforms therefore reflect the contrasting response of the marine organic and carbonate carbon pumps to nutrient enhanced phytoplankton productivity the change in marine carbon partitioning is mirrored in a shift of the 13c record towards more positive values the transition to the 13c peak values lasted up to several hundred thousand years the peaks of the excursions also covering a time span of up to several hundred thousand years reflect a new stabilisation of the carbon partitioning between carbonate and organic carbon sinks a renewed intensification of carbonate sedimentation under mesotrophic conditions was facilitated by stabilisation of the sea level rise at a high level decreasing 13c values record increasing carbonate carbon burial rates at constant or decreasing organic carbon accumulation rates these changes contributed to the stabilisation of the marine carbon budget and the global carbon cycle up to millions of years after its initial perturbation

the mean summertime circulation along australia s southern shelves a numerical study abstract for the first time a high resolution regional model is developed for the slope and shelf circulation within the great australian bight and for the gulfs region of south australia the results indicate the extent nature and dynamical interaction of a variety of circulation features that are most likely to be important for the region in particular the positive wind stress curl south of australia leads to an equatorward sverdrup transport in the deep ocean westward flinders current along the slope and upwelling of the 600 m deep permanent thermocline the wind stress curl also leads to a seaward topographic sverdrup transport within the wide sloping shelf of the bight and results in an anticyclonic gyre that is intensified off the eyre peninsula and reduced in magnitude by the joint effect of baroclinicity and topographic relief in the western half of the bight the seaward surface ekman and topographic transports are shown to converge with the onshore component of the flinders current lea

coastal trapped waves on the west coast of south island new zealand abstract the coastal ocean response to wind forcing on the west coast continental shelf of south island new zealand is examined using current sea level and wind observations weather band motions over the northern region of the shelf appear to be dominated by the response to wind forced flux through cook strait through strait forcing is still evident in the currents of the southern region but west coast alongshore wind forcing is also important most of the variance of nearshore weather band currents in the northern region of the shelf can be described in terms of coastal trapped waves ctws a fit of ctw modes 1 and 2 to the observations in that region indicates the equal importance of both modes in agreement with the theories of strait generated ctws farther south the across shelf depth profile alters dramatically such that ctw structures change from being almost barotropic in the northern region to highly baroclinic this rapid change in topography suggests that considerable scattering of ctws m

spatial delineation of groundwater salinity using deep time domain electromagnetic geophysical measurements a feasibility study 1 the objective of this study was to delineate the spatial distribution of fresh brackish and saline groundwater bodies as well as brine beneath the judea desert israel we used the deep time domain electromagnetic tdem geophysical system cycle 5m which provides the maximum exploration capability to depths 1 5 2 km below land surface the study was conducted at 21 locations at the desert plateau where fresh groundwater flows through the upper aquifers from the replenishment area at the judea mountains toward the dead sea springs in deeper aquifers brackish and saline groundwater bodies exist which originated from lakes and lagoons that existed at the dead sea rift valley during the pleistocene and pliocene respectively it was found that within carbonate formations fresh groundwater c 103 ppm total dissolved solids tds is characterized by a resistivity of more than 15 m brackish groundwater 103 c 104 ppm tds is characterized by 5 15 m saline groundwater 104 c 105 ppm tds is characterized by 0 5 5 m and brine 105 c ppm tds is characterized by less than 0 5 m

on the east australian current variability encroachment and upwelling 1 observations from an intensive oceanographic field program which took place in 1998 1999 about the separation point of the east australian current eac show significant spatial and temporal variability of the eac upstream of the separation point southward flowing currents are strong with subinertial velocities of up to 130 cm s 1 in the near surface waters whereas downstream currents are highly variable in both strength 1 70 cm s 1 and direction upwelling is observed to occur through both wind driven and current driven processes with wind effects playing a lesser role by contrast the encroachment of the eac upon the coast has a profound effect on the coastal waters accelerating the southward alongshore currents and decreasing the temperature in the bottom boundary layer bbl by up to 5 degreesc as the axis of the jet moves onshore negative vorticity increases in association with an increase in nonlinear acceleration during this time bottom friction is increased the burger number is reduced and the bbl shut down time lengthens the observed upwelling is attributed to enhanced onshore ekman pumping through the bbl resulting from increased bottom stress as the southerly flow accelerates when the eac encroaches across the continental shelf

the forcing of low frequency motions within bass strait abstract three months of coincident sea level and current meter data collected during the autumn of 1984 is analyzed so as to determine the relative importance of local wind stress and coastal trapped waves ctws incident from the great australian bight in driving low frequency motions within bass strait the analysis is facilitated by the development of analytical models for kelvin waves within the strait that are forced by these agents and which allow for backscattering by the adjacent shelves such backscattering arises from the requirement that the kelvin wave pressure field within the strait match that of the ctws that are generated on the adjacent shelves two predictions that sea level variability vanish at the southeast strait corner and be dominated by incident ctw energy at the northwest strait corner are substantiated both directly by the data and indirectly through a fit of the forced kelvin wave models for the period of analysis the data and fitted models also show that at relatively hig

winter spring flushing of bass strait south eastern australia a numerical modelling study this study investigates winter spring flushing of bass strait with a two dimensional non linear depth averaged shallow water model the model is driven with a 180 day wind time series an advection diffusion scheme for several tracers is used to reveal the flushing pattern timescale of the region the study considers how external water masses flush strait waters it shows that shelf water entering the strait through the passage between king island and cape grim makes the largest contribution to strait waters results show that the central area of the strait is a stagnation area of weak currents and long flushing times 160 days the influence of external water masses on the stagnation area is estimated the findings have implications for marine ecosystems residence times air sea modifications of water mass properties and dense water formation in the region

carbon isotope signatures of pedogenic carbonates from se china rapid atmospheric pco2 changes during middle late early cretaceous time lower cretaceous pedogenic carbonates exposed in se china have been dated by u pb isotope measurements on single zircons taken from intercalated volcanic rocks and the ages integrated with existing stratigraphy 13 c values of calcretes range from 7 0 to 3 0 and can be grouped into five episodes of increasing decreasing values the carbon isotope proxy derived from these palaeosol carbonates suggests p co 2 mostly in the range 1000 2000 parts per million by volume ppmv at s z co 2 contributed by soil respiration 2500 ppmv and 25 c during the hauterivian albian interval c 30 ma duration such atmospheric co 2 levels are 4 8 times pre industrial values almost double those estimated by geochemical modelling and much higher than those established from stomatal indices in fossil plants rapid rises in p co 2 are identified for early hauterivian middle barremian late aptian early albian and middle albian time and rapid falls for intervening periods these episodic cyclic changes in p co 2 are not attributed to local tectonism and volcanism but rather to global changes the relationship between reconstructed p co 2 and the development of large igneous provinces lips remains unclear although large scale extrusion of basalt may well be responsible for relatively high atmospheric levels of this greenhouse gas suggested levels of relatively low p co 2 correspond in timing to intervals of regional to global enrichment of marine carbon in sediments and negative carbon isotope 13 c excursions characteristic of the oceanic anoxic events oae1a selli event kilian and paquier events constituting part of the oae 1b cluster and oae1d short term episodes of high p co 2 coincide with negligible carbon isotope excursions associated with the faraoni event and the jacob event given that episodes of regional organic carbon burial would draw down co 2 and negative 13 c excursions indicate the addition of isotopically light carbon to the ocean atmosphere system controls on the carbon cycle in controlling p co 2 during early cretaceous time were clearly complex and made more so by atmospheric composition also being affected by changes in silicate weathering intensity

paleoceanography of the northwestern pacific during the albian abstract the deep ocean conditions and circulation during the cretaceous have been characterized mainly by the sediments from the tethys sea and the proto atlantic ocean because sedimentological data from the pacific basin from that period have been quite limited here we present new geochemical measurements from sediments that we collected from two sites in hokkaido japan that were presumably deposited in the northwest pacific during the albian 112 ma the low organic carbon and carbonate contents combined with other measurements from our study suggest that the mid depth northwest pacific during the time of deposition was corrosive to sedimentary carbonate but oxic we also use a simple box model of the ocean biogeochemistry to investigate the conditions of carbonate preservation and suggest that the northwest pacific hydrography was quite distinct from the tethys sea and the proto atlantic ocean

recirculation in the lee of complicated headlands a case study of bass point it has been argued in recent papers that the nature of headland and coastal island wakes can be highly dependent on the level of turbulence caused by complicated coastal geometry and bottom topography as well as on the loss of energy and momentum to the seabed due to friction a series of field experiments was conducted around bass point a 4 km long headland near sydney australia using moored current meters and an acoustic doppler current profiler the offshore component of currents measured offshore of the point showed a high degree of spectral energy at about the 7 day cycle with a small amount at the diurnal frequency but the reverse was found in the lee of the headland where most of the recirculation was at the diurnal frequency numerical experiments resulted in similar spectra being obtained from locations behind the headland when the numerical model was forced with a spectrum of frequencies resembling the spectrum of the offshore free stream current which was derived from the field results the size and frequency of eddyshedding in the lee of the headland depended on the degree of variability of the inflowing free stream with a diurnal component in the free stream appearing to cause the oscillations in the wake also of diurnal frequency the numerical experiments also show that the size of the recirculating wake was affected by the complexity of the headland s geometry

mid cretaceous step wise demise of the carbonate platform biota in the northwest pacific and establishment of the north pacific biotic province the global spatiotemporal distribution of the cretaceous carbonate platform biota which is characterized by tropical mesogean cretaceous tethys taxa is an important aspect of earth s paleobiogeography all available records of this biota in the northwest pacific japan and sakhalin island are summarized in order to elucidate its stratigraphic distribution patterns and faunal changes with special attention given to the biota of the late aptian early albian this carbonate platform biota flourished from the berriasian to early albian interval in the northwest pacific indicating that the northwest pacific clearly belonged to the tethyan biotic realm at that time a step wise demise of the carbonate platform biota transpired in the latest aptian to middle albian interval mesogean key taxa rudists and dasycladacean algae some mesogean indicators hermatypic corals and stromatoporoids and nerineacean gastropods disappeared at the late aptian to early albian transition following this event other mesogean indicators orbitolinid foraminifers and calcareous red algae and coated grains disappeared at the early to middle albian transition there is no record of carbonate platform biota in the northwest pacific during the long interval between the middle albian and paleocene the step wise demise of the carbonate platform biota in the latest aptian middle albian interval strongly implies a vicariance event which separated the north pacific from the tethyan biotic realm and established the north pacific biotic province 2006 published by elsevier b v

carbon isotope fluctuations of terrestrial organic matter for the upper cretaceous cenomanian santonian in the obira area of hokkaido japan stratigraphic fluctuations of carbon isotope values of terrestrial organic matter within the upper cretaceous cenomanian santonian sequence in the obira area of hokkaido japan record distinctive 13 c fluctuations for the cenomanian turonian boundary the middle turonian the upper turonian lower coniacian and the santonian a biostratigraphic framework of the age diagnostic taxa ammonoids bivalves and planktic foraminifers indicates that these 13 c fluctuation events are comparable with those recorded in 13 c data of terrestrial organic matter in japan and marine carbonates in europe these correlations reinforce the utility of these 13 c events in terms of global chemostratigraphy in particular the 13 c patterns within the overall positive interval of the cenomanian turonian boundary event are highly conformable between marine and terrestrial records the consistent nature of these different records of 13 c fluctuation patterns demonstrates that the terrestrial organic 13 c data mirror the global scale 13 c patterns in the carbon reservoir of ocean atmosphere terrestrial biosphere during the cenomanian turonian boundary event in addition global correlation of short term marine and terrestrial organic 13 c fluctuations of the upper cretaceous sequence indicate that the magnitude of several terrestrial organic 13 c events appears more amplified than that of coeval marine carbonate 13 c events this correlation is interpreted to mean that the effects of local co 2 emission into the atmosphere by release of terrestrial methane hydrate or biomass burning of terrestrial vegetation in the hinterland of the ne asian region have been superimposed on the global 13 c trend and resulted in the terrestrial organic 13 c records of the yezo group

numerical study on tidal mixing along the shelf break in the green belt in the southeastern bering sea 1 tidal mixing and its associated iron and nutrients flux from a subsurface layer along the shelf break has been considered as one of the key processes to maintain the high summertime biological productivity in the green belt in the southeastern bering sea in the present study tidal mixing near the shelf break is examined with a three dimensional high resolution numerical model to quantify the enhanced mixing and to reveal the underlying physical mechanisms based on the different characteristics of diurnal and semidiurnal internal waves strong turbulent mixing with energy dissipation rates of over 1 10 8 w kg is reproduced along the green belt in the numerical model forced by barotropic diurnal and or semidiurnal tides at open boundaries the energy dissipation off the shelf break near the sea surface is enhanced due to the semidiurnal internal waves whereas the dissipation near the bottom of the shelf break is enhanced by the diurnal topographically trapped waves an additional experiment with stratification representative of winter conditions shows a significant influence of stratification on the energy dissipation off the shelf break due to the change in features of both diurnal and semidiurnal internal waves low mode semidiurnal baroclinic energy flux from the aleutian passes is shown to increase the energy dissipation along the shelf slope between pribilof and zhemchug canyons these results suggest that the strong vertical mixing along the shelf break induced by the diurnal and semidiurnal tides both play important roles in maintaining the iron and nutrients supply along the green belt

low frequency current variability on the labrador shelf current meter measurements from two locations on the northern part of the labrador shelf have been analyzed using empirical orthogonal function eof analysis in the three frequency bands 0 09 0 18 cpd 0 18 0 36 cpd and 0 36 0 54 cpd to describe the measurements in each frequency band a numerical circulation model was developed for the shelf driven by alongshore and onshore wind stresses and by flow through hudson strait the latter flow is taken to arise from the atmospheric pressure variations over hudson bay and from the along static wind stress over hudson strait the model appears to be quite successful in describing the circulation in the center frequency band this suggests that the forcing within this band is primarily due to the alongshore wind stress over the shelf and to the flow through hudson strait the model indicates that in the region of study the mode 1 shelf wave dominates the velocity field over the upper part of the shelf whereas mode 2 dominates the flow near the shelf break in the first and third frequency bands the model is less successful in describing the measured currents it is likely that this failure is at least in part due to the neglect of other forcing mechanisms such as shelf waves propagating southward out of baffin bay

investigating the record of permian climate change from argillaceous sedimentary rocks oman a standard method for the analysis of carbon isotope composition of bulk organic matter 13 c bulk in palaeoenvironmental and stratigraphic studies of sedimentary basins associated with hydrocarbons is suggested this method includes the removal of interstitial hydrocarbon within the sediments which is shown to have a negative effect on 13 c using the method a 13 c bulk trend c 21 to 24 was found within the lower permian al khlata and lower gharif formations of thuleilat 16 and 42 well sections south oman palaeontological and sedimentological evidence indicates considerable palaeoenvironmental change from a cold climate lowland fern flora and upland primitive conifer flora low in the sequence to a lowland cycad like and upland glossopterid or other gymnospermous flora higher in the sequence the lithologies range from glacial diamictite at the base to calcrete horizons and redbeds at the top it is therefore likely that the 13 c bulk trend is related to palaeoenvironmental change

response of a coastal hydrogeological system to a rapid decline in sea level the case of zuqim springs the largest discharge area along the dead sea coast summary the almost instantaneous response of a natural on shore groundwater system to an extremely rapid drop in the level of an adjacent lake is described in this study the study is focused on the zuqim feshcha spring complex located on the northwestern shore of the dead sea which exhibits a drop of tens of meters in its water level over the last few decades in this exceptional field lab fluctuations and trends in the flow regime are recognized as well as the contemporaneous geochemical variations lithological facies variations have a pronounced effect on the underground flow regime the following main processes were recognized a slight shifting of the long standing springs eastward following the retreating shore b extension of the hydrologic system southward without significant change in the total discharge of the entire spring complex the new seepages are characterized by high variability in salinity and c continuous refreshing of the spring water as a result of prolonged flushing of old trapped brines the water of the zuqim springs lie on mixing lines between two local brine types and diluted brine of the lisan lake the precursor of the dead sea based on our findings future development processes in the spring complex are predicted which is essential because of their impact on the endemic ecosystem that relies on this water in addition continuation of the rapid drop in lake level is expected to cause intensification of erosional processes such as deepening of flow gullies shifting of the entire hydrological system southward and migration along with the retreating shore is also expected to continue as well as the continuous decrease in the water salinity

pre collapse identification of sinkholes in unconsolidated media at dead sea area by nanoseismic monitoring graphical jackknife location of weak sources by few low snr records summary the sudden failure of near surface cavities and the resulting sinkholes have constituted a recent hazard affecting the populations lifelines and the economy of the dead sea region this paper describes how seismic monitoring techniques could detect the extremely low energy signals produced by cavitation in unconsolidated layered media dozens of such events were recorded within a radius of 200 m during several night time experiments carried out along the western dead sea shores the absence of prior knowledge about cavitation induced events in unconsolidated media required an initial signal characterization for which a series of source processes were simulated in the field under controlled conditions the waveform analysis by sonograms recognizes two main groups of seismic events impacts on dry material and impacts in liquid our analysis demonstrates that the discrimination between both types of source functions is robust despite the extreme nature of the scatter media in addition to their association with specific source processes these events can be precisely located by a graphical error resistant jackknifing approach using an extended m l scale their source energy can be quantified and related to standard seismic activity in summary it is now possible to monitor subsurface material failures before sinkhole collapse since the discrimination of impact signals on the basis of their frequency content is indicative of the maturity of the cavitation process

sinkhole swarms along the dead sea coast reflection of disturbance of lake and adjacent groundwater systems more than a thousand sinkholes have developed along the western coast of the dead sea since the early 1980s more than 75 of them since 1997 all occurring within a narrow strip 60 km long and 1 km wide this highly dynamic sinkhole development has accelerated in recent years to a rate of 150 200 sinkholes per year the sinkholes cluster mostly over specific sites up to 1000 m long and 200 m wide which spread parallel to the general direction of the fault system associated with the dead sea transform research employing borehole and geophysical tools reveals that the sinkhole formation results from the dissolution of an 10 000 yr old salt layer buried at a depth of 20 70 m below the surface the salt dissolution by groundwater is evidenced by direct observations in test boreholes these observations include large cavities within the salt layer and groundwater within the confined subaquifer beneath the salt layer that is undersaturated with respect to halite moreover the groundwater brine within the salt layer exhibits geochemical evidence for actual salt dissolution na cl 0 5 0 6 compared to na cl 0 25 in the dead sea brine the groundwater heads below the salt layer have the potential for upward cross layer flow and the water is actually invading the salt layer apparently along cracks and active faults the abrupt appearance of the sinkholes and their accelerated expansion thereafter reflects a change in the groundwater regime around the shrinking lake and the extreme solubility of halite in water the eastward retreat of the shoreline and the declining sea level cause an eastward migration of the fresh saline water interface as a result the salt layer which originally was saturated with dead sea water over its entire spread is gradually being invaded by fresh groundwater at its western boundary which mixes and displaces the original dead sea brine accordingly the location of the western boundary of the salt layer which dates back to the shrinkage of the former lake lisan and its transition to the current dead sea constrains the sinkhole distribution to a narrow strip along the dead sea coast the entire phenomenon can be described as a hydrological chain reaction it starts by intensive extraction of fresh water upstream of the dead sea continues with the eastward retreat of the lake shoreline which in turn modifies the groundwater regime finally triggering the formation of sinkholes

detection of subsurface brines freshwater bodies and the interface configuration in between by the time domain electromagnetic method in the dead sea rift israel high radon fluxes in the seismically active dead sea rift seem to be affected by the hydrological system and the different salinities of groundwater bodies involved the time domain electromagnetic tdem method was employed to delineate those different bodies and the configuration of the interfaces between them the present hydrological system and the related brines and interfaces are controlled by the dead sea base level presently at 408 m below msl tdem measurements detect low resistivity 1 ohm m units representing brines and the interface between them as well as the overlying fresher water bodies in addition high resistivity freshwater units are also detected underlying the brines related herein to a multiple hydrological system low resistivity brines detected above the present base level are interpreted herein as yet unflushed ones which correspond to a former higher base level higher sequences below historical sixteenth century base levels are already devoid of brines which gives an indication as to the rate of flushing

evolution patterns of radiolaria and organic matter variations a new approach to identify sea level changes in mid cretaceous pelagic environments the relation between sea level changes plankton productivity and evolution as well as the occurrence of anoxic sediments provides an interesting avenue of paleooceanographic research in this context we examined mid cretaceous radiolarian faunas carbonate isotopic and organic matter type data of deep sea drilling project and ocean drilling program cores from the north atlantic and samples from outcrops of the western tethys from central and northern italy former studies indicate that an expansion of the oxygen minimum zone caused plankton extinctions at the cenomanian turonian boundary an expanded oxygen minimum zone would destroy deeper habitats of planktic foraminifera causing the extinction of deeper dwelling forms although this model is well established for the cenomanian turonian boundary not much is known about the causes of extinctions and radiations during the entire mid cretaceous aptian turonian we demonstrate that the dimension of the oxygen minimum zone which depends on the relative sea level and the corresponding nutrient supply causes the complex pattern of evolution and radiation of planktic protozoa and the sedimentation of black shales in the mid cretaceous this new depositional model allows correlation of micropaleontologic data and different types of black shales in the pelagic realm within a sequence stratigraphic framework

coastal trapped wave scattering into and out of straits and bays abstract a theory for the generation of coastal trapped waves ctws by an oscillatory coastal flux through a strait is extended so as to make velocity pressure and energy flux everywhere continuous this development is achieved through the inclusion of kelvin and poineare wave modes in a match for pressure leading to a system of linear equations for the unknown amplitudes a kelvin wave incident on the eastern mouth of bass strait for example is shown to preferentially scatter energy into ctw modes 2 and 1 on the shelf as well as driving a poincare wave field that results in a velocity jet trapped to the victorian coast such coastal velocity jets are also a feature of the scattering of ctws incident on a strait for a mode n incident ctw the fraction of net energy flux that enters the strait is also shown to be well approximated by h0bn2 where h0 is the strait depth and bn coupling coefficient the scattering of the remaining energy among other ctw modes is detailed and shown to become larger as the

stable isotope geochemistry of coals humic kerogens and related natural gases isotope systematics are well defined for conventional sapropelic type i ii kerogens and their associated bacterial and thermogenic natural gas products these geochemical tools are used to estimate source type maturity and depositional environment and as a correlation technique in many cases the natural gas signatures in near surface samples and drill cuttings can be used to classify or predict a deeper lying source rock or reservoir corresponding interpretative schemes for coals type iii kerogens and their associated hydrocarbons are progressing quickly the shift in attention to humic sources is driven primarily by depletion of conventional oil and gas resources and the economic and societal requirements of coal and coal bed methane carbon hydrogen and nitrogen stable isotope variations can be large between different coals and humic kerogens these differences can often be recognized in their bulk 13corg dorg and 15norg values isotope signatures of coals can be diagnostic of several factors including deposit age type geographic location maturity and generation history however these characteristic isotopic variations are substantially better defined by the c h and n isotope ratios of the separate maceral groups such as vitrinite exinite and inertinite this new application of stable isotopes at the maceral and compound levels have great potential to improve the interpretative precision over conventional whole coal or bulk techniques hydrocarbon gases including coal gases derived from coals and humic kerogens can be distinguished from type i ii sources based on their molecular rations i e c1 c2 c3 and by comparing their stable isotope compositions especially 13cch4 and dch4 the 13cc2h6 can also be valuable but ethane is generally present in small amount 1 vol and requires

pre existing caverns in salt formations could be the major cause of sinkhole hazards along the coast of the dead sea since 1990 hundreds of sinkholes have appeared along the coast of the dead sea in the literature the rapid development of sinkholes is explained as a result of a drop in the level of the dead sea this model assumes very fast dissolution of large volumes of salt and the creation of new caverns that cause sinkholes in 10 to 20 years however the results of our geophysical study do not confirm the fast dissolution assumption to explain the available field observations we propose the following model 1 slow dissolution of salt much longer than 20 years with the creation of caverns without development of sinkholes 2 sinkhole development is triggered by the lowering of the groundwater level because the rocks overlying the salt formation become unsaturated 3 the time of sinkhole appearance is controlled by the mechanical properties of the rocks that overlie pre existing caverns

a southern hemisphere verification for the topex poseidon satellite altimeter mission as a check on the total system accuracy of the topex poseidon satellite a southern hemisphere verification study was undertaken in bass strait 41 s immediately adjacent to the southern ocean an acoustic tide gauge and two pressure gauges were installed on the southern side of bass strait near where descending pass 88 crosses the tasmanian coast the tide gauge benchmark height was estimated relative to the laser tracking station at orroral valley and the very long baseline interferometry station near hobart using global positioning system surveying techniques in the topex poseidon geophysical data records flags on the altimeter data began to be set 15 20 km from land and little useful altimeter data were available within about 13 km of the coast the acoustic tide gauge heights were corrected for changes in tidal phase and amplitude between the coast and the offshore subsatellite point using results from a numerical model the altimeter correction for atmospheric water vapor calculated from the topex microwave radiometer data and the insitu precipitable water data agreed to 2 cm rms with no significant bias the rms variability between the insitu sea level estimates and the topex poseidon estimates was less than 3 5 cm as part of this variability is caused by inaccuracies in the estimates of the sea level variations between the coast and the subsatellite point the result indicates that the precision of the topex poseidon sea level height measurement system including the time dependent orbit errors the ionospheric corrections and the wet and dry tropospheric path delays is less than 3 5 cm over bass strait considerably below the original system specifications of 13 cm our estimate of the altimeter bias including geographically correlated orbit error is 25 10 cm consistent with the results at the nasa harvest platform and centre national d etudes spatiales lampedusa calibration sites however accurate estimation of this total altimeter bias is confounded by the lack of altimeter data close to land and in particular limitations in the available local geoid data the altimeter bias shows no significant drift at this site

geochemical and climatic effects of increased marine organic carbon burial at the cenomanian turonian boundary perhaps the most significant event in the cretaceous record of the carbon isotope composition of carbonate1 2 other than the 1 2 5 negative shift in the carbon isotope composition of calcareous plankton at the cretaceous tertiary boundary3 is the rapid global positive excursion of 2 13c enrichment which took place between 91 5 myr and 90 3 myr late cenomanian to earliest turonian c t boundary event 1 4 5 this excursion has been attributed to a change in the isotope composition of the marine total dissolved carbon tdc reservoir resulting from an increase in rate of burial of 13c depleted organic carbon which coincided with a major global rise in sea level5 during the so called c t oceanic anoxic event oae 6 here we present new data from nine localities which demonstrate that a positive excursion in the carbon isotope composition of organic carbon at or near the c t boundary7 8 is nearly synchronous with that for carbonate and is widespread throughout the tethys and atlantic basins fig 1 as well as in more high latitude epicontinental seas the postulated increase in the rate of burial of organic carbon may have had a significant effect on co2 and o2 concentrations in the oceans and atmosphere and consequent effects on global climate and sedimentary facies

aquifer characteristics derived from the interaction between water levels of a terminal lake dead sea and an adjacent aquifer the water level of the dead sea a terminal hypersaline lake total dissolved solids approximately 340 g l has decreased at an average rate of 0 5 m yr since 1960 and by 0 8 m yr between 1981 and 1989 the dramatic long term water level variation of the dead sea and the seasonal short term fluctuations are accompanied by parallel variations of groundwater levels in an adjacent aquifer a general methodology based on a simplified yet reliable one dimensional flow model together with continuous measurements of groundwater levels in observation wells enables analysis of aquifer structural and hydraulic properties furthermore this analysis enables prediction of future groundwater levels in unconfined and confined aquifers due to future changes in lake levels

calcite graphite isotope thermometry a test for polymetamorphism in marble tudor gabbro aureole ontario canada graphitization and coarsening of organic material in carbonate bearing metasedimentary rocks is accompanied by carbon isotope exchange which is the basis of a refractory pressure independent geothermometer comparison of observed isotopic fractionations between calcite and graphite a13ccal gr with independent petrological thermometers provides the following empirical calibration over the range 400 800 c a13ccal gr 5 81 x lo6 x t k 2 61 this system has its greatest potential in marbles where calcite graphite is a common assemblage and other geothermometers are often unavailable the temperature dependency of this empirical calibration differs from theoretical calibrations reasons for this are unclear but the new empirical calibration yields temperature estimates in better agreement with independent thermometry from several terranes and is preferred for geological applications both calcite graphite isotopic thermometry and calcite dolomite solvus thermometry are applied to marble adjacent to the tudor gabbro in the grenville province of ontario canada the marble has undergone two metamorphic episodes early contact metamorphism and later regional metamorphism values of a13cca gr decrease regularly from c 8 0 in samples over 2 km from the pluton to values of 3 4 within 200m of the contact these samples appear to preserve fractionations from the early thermal aureole with the empirical geothermometer and indicate temperatures of 450 500 c away from the intrusion and 700 750 c near the gabbro this thermal profile around the gabbro is consistent with conductive heat flow models in contrast the distribution of mg between calcite and dolomite has been completely reset during later regional metamorphism and yields uniform temperatures of c 500 c even at the contact graphite textures are important for interpreting the results of the calcite graphite thermometer coarsening of graphite approaching the tudor gabbro correlates with the decrease in isotopic fractionations and provides textural evidence that graphite crystallization took place at the time of intrusion in contrast to isotopic exchange during prograde metamorphism which is facilitated by graphitization retrogressive carbon isotopic exchange appears to require recrystallization of graphite which is sluggish and easily recognized texturally resistance of the calcite graphite system to resetting permits thermometry in polymetamorphic settings to see through later events that have disturbed other systems

discharge estimation of submarine springs in the dead sea based on velocity or density measurements in proximity to the water surface the dead sea is a closed lake the water level of which is lowering at an alarming rate of about 1 m year factors difficult to determine in its water balance are evaporation and groundwater inflow some of which emanate as submarine groundwater discharge a vertical buoyant jet generated by the difference in densities between the groundwater and the dead sea brine forms at submarine spring outlets to characterize this flow field and to determine its volumetric discharge a system was developed to measure the velocity and density of the ascending submarine groundwater across the center of the stream along several horizontal sections and equidistant depths while divers sampled the spring this was also undertaken on an artificial submarine spring with a known discharge to determine the quality of the measurements and the accuracy of the method the underwater widening of the flow is linear and independent of the volumetric spring discharge the temperature of the dead sea brine at lower layers primarily determines the temperature of the surface of the upwelling produced above the jet flow as the origin of the main mass of water in the submarine jet flow is dead sea brine based on the measurements a model is presented to evaluate the distribution of velocity and solute density in the flow field of an emanating buoyant jet this model allows the calculation of the volumetric submarine discharge merely requiring either the maximum flow velocity or the minimal density at a given depth

late jurassic early cretaceous intra arc sedimentation and volcanism linked to plate motion change in northern japan the sorachi group composed of upper jurassic ophiolite and lower cretaceous island arc volcano sedimentary cover provides a record of late jurassic early cretaceous sedimentation and volcanism in an island arc setting off the eastern margin of the asian continent stratigraphic changes in the nature and volume of the sorachi group volcanic and volcaniclastic rocks reveal four tectonic stages these stages resulted from changes in the subduction direction of the pacific oceanic plate stage i in the late jurassic was characterized by extensive submarine eruptions of tholeiitic basalt from the back arc basin slab roll back caused rifting and sea floor spreading in the supra subduction zone along the active asian continental margin stage ii corresponded to the berriasian and featured localized trachyandesitic volcanism that formed volcanic islands with typical island arc chemical compositions at the beginning of this stage movement of the pacific oceanic plate shifted from northeastward to northwestward during stage iii in the valanginian submarine basaltic volcanism was followed by subsidence the pacific oceanic plate motion turned clockwise and the plate boundary between the asian continent and the pacific oceanic plate changed from convergent to transform during stage iv in the hauterivian barremian in situ volcanism ceased in the sorachi yezo basin and the volcanic front migrated west of the sorachi yezo basin

a review of the shelf slope circulation along australia s southern shelves cape leeuwin to portland abstract a review is presented of the ocean circulation along australia s southern shelves and slope uniquely the long zonal shelf is subject to an equatorward sverdrup transport that gives rise to the flinders current a small sister to the world s major western boundary currents the flinders current is strongest near the 600 m isobath where the current speeds can reach 20 cm s and the bottom boundary layer is upwelling favourable it is larger in the west but likely intermittent in both space and time due to possibly opposing winds thermohaline circulation and mesoscale eddies the flinders current may be important to deep upwelling within the ubiquitous canyons of the region during winter the leeuwin current and local winds act to drive eastward currents that average up to 20 30 cm s the currents associated with the intense coastal trapped wave field 6 12 day band are of order 25 30 cm s and can peak at 80 90 cm s wintertime winds and cooling also lead to downwelling to depths of 200 m or more and the formation of dense coastal water within the great australian bight and the south australian sea within the great australian bight the thermohaline circulation associated with this dense water is unknown but may enhance the eastward shelf edge south australian current the dense salty water formed within spencer gulf is known to cascade as a gravity current to depths of 200 m off kangaroo island this dense water outflow and meanders in the shelf circulation also fix the locations of a sequence of quasi permanent mesoscale eddies between the eyre peninsula and portland during summer the average coastal winds reverse and surface heating leads to the formation of warm water in the western great australian bight and the south australian sea no significant exchange of shelf water and gulf water appears to occur due to the presence of a dense nutrient rich sub surface pool that is upwelled off kangaroo island the winds lead to weak average coastal currents increasing evidence suggests that el nino events 4 7 year period can have a major impact on the winter and summer circulation these events propagate from the pacific ocean and around the shelf slope wave guide of west australia and into the great australian bight during winter el nino events the average shelf currents may be largely shut down during summer the thermocline may be raised by up to 150 m the nature and role of tides and surface waves is also discussed along with uncertainties in the general circulation and future research

carbon isotope record of the early jurassic toarcian oceanic anoxic event from fossil wood and marine carbonate lusitanian basin portugal thetoarcianoceanicanoxicevent oae intheearlyjurassic 183maago wascharacterizedbywidespreadnear synchronous deposition of organic rich shales in marine settings as well as perturbations to several isotopic systems characteristically two positive carbon isotope excursions in a range of materials are separated by an abrupt negative shift carbon isotope profiles from toarcian fossil wood collected in england and denmark have previously been shown to exhibit this large drop 7 i n 13 c values interpreted as due to an injection of isotopically light co2 into the ocean atmosphere system however the global nature of this excursion has been challengedonthebasisofcarbon isotopedatafromnektonicmarinemolluscs belemnites whichexhibitheavierthanexpectedcarbonisotope values here we present new data principally from fossil wood and bulk carbonate collected at centimetre scale from a hemipelagic section at peniche coastal portugal this section is low in organic carbon average toc 0 5 and the samples should not have suffered significant diagenetic contamination by organic carbon of marine origin the carbon isotope profile based on wood shows two positive excursions separated by a large and abrupt negative excursion which parallels exactly the profile based on bulk carbonate samples from the same section albeit with approximately twice the amplitude 8 in wood versus 3 5 in carbonate these data indicate thatthe negative carbon isotope excursion affected the atmosphereand by implication the global ocean as well the difference in amplitude between terrestrial organic and marine carbonate curves can be explained by greater water availability in the terrestrial environment during the negative excursion for which there is independent evidence from marine osmiumisotope records and plausibly changes in atmospheric co2 content for which independent evidence is also available the peniche succession is also notable for the occurrence of re deposited sediments their lowest occurrence coincides with the base of the negative excursionandtheirhighestoccurrencecoincideswithitstop thus slopeinstabilityandsedimentsupplycouldhavebeenstronglylinked to the global environmental perturbation an association that may misleadingly simulate the effects of sea level fall

handbook of environmental isotope geochemistry vol 1 the terrestrial environment a p fritz and j ch fontes editors elsevier amsterdam 1980 xii 532 pp u s 90 25 dfl 185 00

combined time domain electromagnetic soundings and gravimetry to determine marine intrusion in a detrital coastal aquifer southern spain summary marine intrusion is undoubtedly the most serious problem facing coastal aquifers that are exploited for use it is also an excellent indicator of the state of the aquifers resources this work proposes the combined application of two complementary geophysical techniques as an effective method for locating the saline wedge on one hand time domain electromagnetic soundings are the most reliable geophysical method for determining low resistivity zones that usually correspond to the presence of seawater although in some cases low resistivities may be due to the properties of the substrate on the other hand gravimetry allows a precise determination of the depth of the aquifer basement thus resolving the above uncertainty information provided by the lithological columns from boreholes has also allowed great precision in the calibration of the results from both techniques this methodology has been applied to the motril salobrena detrital coastal aquifer which has had no problems of marine intrusion to date nonetheless changes in soil use brought about by housing developments golf courses and a proliferation of hothouse agriculture comprise significant shifts in aquifer use in addition the construction of a dam which is drastically reducing the main recharge of the aquifer the guadalfeo river makes it likely there will be profound hydrogeological changes delimiting the extent of the saline wedge is therefore a fundamental step towards quantifying the effects of both the dam and the changes in soil use seawater saturated zones have a resistivity ranging from 0 5 to 5 m detrital sediments 8 400 m carbonates 80 300 m and schists from 2 to 60 m the current position of the saline wedge has been located at 100 200 m from the coastline indicating a healthy state for the aquifer areas with wide and narrow mixing zones have been noted and related to differences in the hydrogeological characteristics of the aquifer

modeling the response of an idealized coastal ocean to a traveling storm and to flow over bottom topography abstract to validate a three dimensional hydrodynamic model for use in coastal waters two test cases with idealized geometry and forcing functions were performed the tests involve the barotropic and baroclinic response of a coastal ocean with a uniform alongshore shelf to the passage of a storm and the circulation induced by flow over a topographic feature the model used in this study is the estuarine coastal and ocean model developed by blumberg and mellor the model is three dimensional and solves for three components of the current field temperature and salinity the model has a terrain following sigma coordinate system a coastal following curvilinear grid in the horizontal and an embedded second order turbulence closure submodel to provide vertical mixing coefficients and uses the free surface as a prognostic variable at the open boundaries a flow relaxation scheme frs has been implemented to pass out internally generated disturbances with minimum reflection the results from the firs

the structure of a hydrothermal system from an integrated geochemical geophysical and geological approach the ischia island case study the complexity of volcano hosted hydrothermal systems is such that thorough characterization requires extensive and interdisciplinary work we use here an integrated multidisciplinary approach combining geological investigations with hydrogeochemical and soil degassing prospecting and resistivity surveys to provide a comprehensive characterization of the shallow structure of the southwestern ischia s hydrothermal system we show that the investigated area is characterized by a structural setting that although very complex can be schematized in three sectors namely the extra caldera sector ecs caldera floor sector cfs and resurgent caldera sector rcs this contrasted structural setting governs fluid circulation geochemical prospecting shows in fact that the caldera floor sector a structural and topographic low is the area where co2 rich 40 cm3 l hydrothermally mature log mg na ratios 150 g m 2 d 1 is clearly captured by electrical resistivity tomography ert and transient electromagnetic tem surveys as a highly conductive resistivity 10 000 mg l and poorly conductive meteoric derived tds 4 000 mg l waters are observed respectively we finally integrate our observations to build a general model for fluid circulation in the shallowest 0 5 km part of ischia s hydrothermal system

hydrogeophysical exploration of three dimensional salinity anomalies with the time domain electromagnetic method tdem summary the time domain electromagnetic method tdem is widely used in groundwater exploration and geological mapping applications tdem measures subsurface electrical conductivity which is strongly correlated with groundwater salinity tdem offers a cheap and non invasive option for mapping saltwater intrusion and groundwater salinization traditionally tdem data is interpreted using one dimensional layered earth models of the subsurface however most saltwater intrusion and groundwater salinization phenomena are characterized by three dimensional anomalies to fully exploit the information content of tdem data in this context three dimensional modeling of the tdem response is required we present a finite element solution for three dimensional forward modeling of tdem responses from arbitrary subsurface electrical conductivity distributions the solution is benchmarked against standard layered earth models and previously published three dimensional forward tdem modeling results concentration outputs from a groundwater flow and salinity transport model are converted to subsurface electrical conductivity using standard petrophysical relationships tdem responses over the resulting subsurface electrical conductivity distribution are generated using the three dimensional tdem forward model the parameters of the hydrodynamic model are constrained by matching observed and simulated tdem responses as an application example a field dataset of ground based tdem data from an island in the okavango delta is presented evaporative salt enrichment causes a strong salinity anomaly under the island we show that the tdem field data cannot be interpreted in terms of standard one dimensional layered earth tdem models because of the strongly three dimensional nature of the salinity anomaly three dimensional interpretation of the field data allows for detailed and consistent mapping of this anomaly and makes better use of the information contained in the tdem field dataset

aspects of the mean wintertime circulation along australia s southern shelves numerical studies abstract a high resolution numerical model is used to study the mean wintertime shelf slope circulation between the gulfs of south australia and the west coast of tasmania the mean downwelling favorable winds for the region result in a continuous eastward coastal current cc extending from cape leeuwin to the eastern coast of tasmania the magnitude of the cc is generally largest over the shelf break has speeds of more than 40 cm s 1 transport 2 4 sv sv 106 m3 s 1 and is generally in good agreement with observations the relative importance of the leeuwin current zonal winds and density gradients to the shelf circulation is established within bass strait the eastward circulation is in good agreement with observations and simple models show that about 30 of the transport arises from local winds and the remainder from the cc the total transport through the strait 0 95 sv is shown to be controlled by sea level on the east coast of tasmania a current of up to 10 cm s 1 is also found to flow

the influence of bays on adjusted sea level over adjacent shelves with application to the labrador shelf we examine how low frequency variations in adjusted sea level over a continental shelf are influenced by an inland sea connected to the shelf through a strait an analytical model shows that free continental shelf waves propagating by the mouth of the strait are strongly modified at a period corresponding to a helmholtz like resonance of the inland sea and strait also near this period atmospheric pressure variations over the inland sea result in relatively strong flow through the strait and the resulting cross isobath flow over the exterior shelf efficiently generates continental shelf waves in the region forward of the strait calculations using a fully nonlinear numerical model with more realistic although still idealized topography verify the predictions of the simpler analytical model we apply this theory to the hudson bay labrador shelf system where we find that this mechanism of shelf wave generation strongly influences the shelf response in the energetic meteorological band 2 6 days data from nain labrador are analyzed using multiple linear regression models and lend further support to the theory

terrestrial record of methane hydrate dissociation in the early cretaceous reconstruction of changing c isotopic composition of early cretaceous atmospheric co2 from fossilized c3 vascular land plant tissue revealed a brief and striking negative excursion d 25 in atmospheric d 13 c followed by a rapid positive compensation d 15 during the aptian ca 117 ma mass balance calculations show that dissociation of a small amount of methane gas hydrate is the most tenable cause of the negative excursion this would also result in an increased co2 o2 mixing ratio as o2 is consumed during ch4 oxidation to co2 spurring the exponential phase of angiosperm biogeographic expansion

stratigraphic carbon isotope fluctuations of detrital woody materials during the aptian stage in hokkaido japan comprehensive δ13c data from four sections of the ashibetsu area abstract geological and organic geochemical studies were performed on an aptian mid cretaceous sedimentary succession of the sorachi and yezo groups in the ashibetsu area central hokkaido northern japan microscopic observations of kerogen samples indicate that the constituents of sedimentary organic matter som are predominantly detrital woody materials opaque and translucent phytoclasts hydrogen carbon atomic ratios of the kerogen samples indicate that the som have not been affected by thermal alteration significantly and thus preserved the original 13c compositions it is found that 13cwood profiles of four sections from the ashibetsu area fluctuate systematically with stratigraphy the 13cwood profiles show a remarkable negative shift followed by a positive excursion of 3 6 from 25 4 to 21 8 exhibiting a bifurcate shape in the early aptian 13cwood values become nearly constant between 23 0 and 23 5 and then approximate to 24 0 in the late aptian a relatively small positive anomaly is also identified in the latest aptian the similarity in 13cwood profiles among different sections suggests that som with homogenized 13c values of c3 plants were deposited in sediments transportation for a long distance from the sufficiently large provenance is postulated to mix c3 plant materials resulting in the homogenization of 13cwood values the 13cwood profile is essentially conformable with that of pacific marine carbonates with their isotopic difference almost constant at all times such conformable marine and terrestrial 13c variations support the previous hypothesis that the temporal 13c change of the aptian ocean atmosphere biosphere system is precisely traced by bulk isotopic analyses of detrital woody materials and the supplemental paleoenvironmental effects onto 13cwood composition such as pco2 changes are probably negligible

long shelf waves generated by a coastal flux solutions are presented for the shelf response of barotropic and stratified oceans to an oscillatory coastal flux through a strait the flux is modeled as the return interior flow due to an ekman transport that arises from a fictitious square wave longshore wind stress the width 2 d of the square wave stress is taken to be that of the strait and the response due to the coastal flux determined from longwave wind forced solutions that exist in the literature the net longshore energy flux for the nth strait forced shelf wave mode wave number kn is shown to be proportional to u2 bnsin knd knd 2 where u2 is the coastal flux spectrum and bn the modal wind coupling coefficients results compare favorably with existing barotropic theories and estimates of net longshore energy flux obtained for the australian coastal experiment region are shown to be in reasonable agreement with observations at periods of 9 days when forcing by bass strait is assumed greatest

a new look at the chemical and hydrological evolution of the dead sea abstract hydrological models of the dead sea ds indicate that subrecent equilibrium conditions have been maintained by input and evaporation of about 1600 106 m3 yr of surface waters recent diversions of the headwaters have led to a drop of about 0 95 m yr suggesting that waters stored in adjacent aquifers are being drained at a rate of about 200 106 m3 yr chemical modeling of the ds indicates that the chemical evolution of the waters can be explained by a simple mixture and evaporation model this model requires the input of 50 106 m3 yr of hot spring waters similar to those emanating at zohar and evaporation factors of about 50 this model suggests that the ds salts have accumulated over the past 5000 years this indicates that the initiation of the present ds was triggered by the onset of the mid holocene pluvial stage as well as by draining of the freshwater lakes present upstream from the lake review of the data of the springs responsible for the chemical nature of the ds suggests that these waters are of meteoric continental origin and that it is likely that these waters have experienced deep circulation in the rift system before discharging at the surface due to convective forces operating in the rift

carbon isotope composition of lower cretaceous fossil wood ocean atmosphere chemistry and relation to sea level change the carbon isotope composition of fossil wood fragments collected through a biostratigraphically well constructed aptian lower cretaceous shallow marine siliciclastic succession on the isle of wight southern britain shows distinct variations with time the results indicate that the stratigraphic signature of delta sup 13 c sub wood through the aptian was influenced primarily by fluctuations in the isotopic composition of co sub 2 in the global ocean atmosphere system as registered in marine carbonates elsewhere and was not governed by local paleoenvironmental and or paleoecological factors negative and positive excursions in delta sup 13 c sub wood through the lower aptian occur in phase with inferred transgressions and regressions respectively a pattern that contrasts with that observed in many previous studies for different time intervals the relationship between delta sup 13 c variations and relative sea level change is tentatively interpreted as a response to various climatic and eustatic factors relating to rapid sea floor spreading thermal uplift of ocean floor emplacement of plateaus volcanic co sub 2 emissions weathering and sedimentary rate

numerical treatment of cross shelf open boundaries in a barotropic coastal ocean model abstract using a barotropic coastal ocean model with a straight coastline and uniform cross shelf bottom slope seven different cross shelf open boundary conditions four of which are applied in either implicit or explicit form are compared in three numerical experiments 1 a mound of water is allowed to collapse and radiate waves toward the open boundaries 2 a uniform alongshelf wind stress is applied at zero time over the entire shelf and held constant for the duration of the experiment 3 a uniform cross shelf wind stress is applied at zero time over the entire shelf and held constant for the duration of the experiment the boundary condition which is most transparent to waves consists of a sponge at the outer edge of the model domain with an orlanski radiation condition at the outer edge of the sponge several open boundary conditions perform adequately in the wind stress experiments but the orlanski radiation condition alone without a sponge appears to give the best total performance of thes

observations of diurnal coastal trapped waves with a thermocline intensified velocity field abstractusing 18 days of field observations we investigate the diurnal d1 frequency wave dynamics on the tasmanian eastern continental shelf at this latitude the d1 frequency is subinertial an

effects of chemical preparation protocols on δ13c values of plant fossil samples abstract for over a half century studies of the stable carbon isotope compositions of plant fossils have provided noteworthy conclusions about the evolution of earth climate however different preparation protocols were used prior to carbon isotope analysis of plant fossils and the accuracy of measured 13c 12c ratios may strongly depend on them we have applied the most frequently used chemical preparation protocols to frenelopsis leaves from four cretaceous localities of western europe our results indicate that procedures to extract plant fossils from sediments are not adequate to retrieve the original plant 13c values the use of schulze s reagent to bleach cuticles in paleobotany allows misleading 13c values of specimens from a same locality with positive shifts of up to 13 6 and increases intra specimen and inter specimen variances sample treatment involving hcl or hcl hf gives consistent 13c mean values for a same leaf and for leaves from a same sedimentary bed however although hf does not provide any advantage in removing potential contamination sources it alters plant fossil tissues slightly increasing the intra and inter leaf variances of 13c values our results indicate that processing plant fossils with hcl only is the most accurate and conservative way to retrieve original 13c values

identification of sinkhole development mechanism based on a combined geophysical study in nahal hever south area dead sea coast of israel seismic refraction magnetic resonance sounding mrs and the transient electromagnetic tem method were applied to investigate the geological and hydrogeological conditions in the nahal hever south sinkhole development area at the dead sea ds coast of israel microgravity and mrs results reliably reveal large karst cavity in the central part of investigated area the map of the seismic velocity shows that sinkholes in nahal hever can be divided into two major groups sinkholes close to the salt edge and sinkholes over compact salt formations between a few tens to a hundred meters from the major cavern the present study shows that the formation of sinkholes of the first group is caused by soil collapsing into the cavern in the area occupied by sinkholes of the second group karst was not detected either by mrs or by seismic diffraction methods tem results reveal shallow clay layer saturated with ds brine underlain sinkholes of this group it allows suggestion that the water drainage and intensive water circulation during rain events wash out fine rock particles from the unsaturated zone into the pre existing cavern initiating the formation of sinkholes of the second group karst development takes place at a very low bulk resistivity 1 m of the ds aquifer attesting to the fact that pores are filled with a highly saline solution refilling of the karstic cavities with collapsing and flushed soil slows down sinkhole development in the area the sinkhole formation cycle at the site is estimated at 10 years sinkhole development throughout the studied area is triggered by a drop in the level of the ds which reduces the head of the confined aquifer and the strength of the overlain sediments

mid cretaceous faunal turnover of intermediate water benthic foraminifera in the northwestern pacific ocean margin abstract the western pacific ocean is a data free region for the mass extinction event and the oxygen conditions at the cenomanian turonian boundary taxonomic and stratigraphic studies of cenomanian to campanian intermediate water 100 1000 m benthic foraminifera at oyubari hokkaido lead to the recognition of extinctions of the largest magnitude in the latest cenomanian interval 94 91 ma the stepwise extinction event is marked by a 48 reduction of calcareous taxa followed by a gradual orgination event during a late turonian to santonian interval this sequence of events marks the greatest faunal turnover observed in the late cretaceous of hokkaido these benthic foraminiferal morphologies indicate a minimum dissolved oxygen content in the early turonian low during middle late turonian medium during coniacian to middle santonian and a high dissolved oxygen content during the late santonian to campanian the establishment of prevailing dysoxic conditions around the cenomanian turonian boundary is the main cause of the benthic foraminiferal mass extinction

a regional model of shelf circulation near bass strait a new upwelling mechanism abstract a study is made of the low frequency three dimensional circulation and upwelling for the western region of bass strait using oceanographic data and the princeton ocean model a novel radiation condition which simulates the effect of an eastern shelf on kelvin wave scattering is successfully tested against analytic solutions for coastal trapped wave ctw scattering and generation using a realistic bathymetry for the bass strait region the model was forced with 8 day period zonal winds within the strait and a mode 1 ctw at the northwestern boundary results demonstrate the existence of a new mechanism for upwelling whereby at the cessation of westward winds within the strait the residual poleward flow over the steeply sloping tasmanian shelf separates from a gyre that develops over the more gently sloping topography near the mouth of the strait the resultant divergence of the velocity field leads to large vertical velocities 34 m day 1 and a plume of subthermocline water that is upwelle

response of the mediterranean and dead sea coastal aquifers to sea level variations 1 the present study examines the response of groundwater systems to expected changes in the mediterranean sea rise of 1cm yr and dead sea levels decline of 1 m yr a fast response is observed in the dead sea coastal aquifer exhibited both in the drop of the water levels and in the location of the fresh saline water interface no such effect is yet observed in the mediterranean coastal aquifer as expected numerical simulations using the feflow software show that the effect of global sea level rise depends on the coastal topography next to the shoreline a slope of 2 5 is expected to yield a shift of the interface by 400 m after a rise of 1m 100 years whereas a vertical slope will yield no shift reduced recharge due to climate change or overexploitation of groundwater also enhances the inland shift of the interface

synchronous negative carbon isotope shifts in marine and terrestrial biomarkers at the onset of the early aptian oceanic anoxic event 1a evidence for the release of 13c depleted carbon into the atmosphere 1 a common feature of records of the early aptian oceanic anoxic event oae 1a is the sharp negative 13c excursion displayed in both carbonate and organic matter at the onset of this event a synchronous negative 13c excursion has also been noted for terrestrial organic matter this negative excursion has been attributed to either an injection of 13c depleted light carbon into the atmosphere or in case of marine sediments recycling of 13c depleted co2 however most studies were done on separate cores and no information on the relative timing of the negative spikes in terrestrial versus marine records has been obtained here we examine early aptian core sections from two geographically distal sites italy and the mid pacific to elucidate the causes and relative timing of this negative spike at both sites increased organic carbon corg and decreased bulk carbonate contents characterize the interval recording oae 1a variously referred to as the selli event the organic material within the selli level is immature and of autochthonous origin measured 13c values of marine and terrestrial biomarkers largely covary with those of bulk organic carbon with lowest values recorded at the base of the organic rich section by contrast sediments enveloping the selli level exhibit very low corg contents and their extractable corg is predominantly of allochthonous origin hydrous pyrolysis techniques used to obtain an autochthonous pre selli 13c value for algal derived pristane from corresponding sample material yielded a negative 13c shift of up to 4 a negative 13c shift of similar magnitude was also measured for the terrigenous n alkanes the results are collectively best explained by means of a massive syndepositional rapid input of 13c depleted carbon into the atmosphere and surface oceans likely delivered either via methane produced from the dissociation of sedimentary clathrates or perhaps by widespread thermal metamorphism of corg rich sedimentary rocks

coefficients for sea surface wind stress heat flux and wind profiles as a function of wind speed and temperature surface layer coefficients for wind profiles wind stress and heat flux in typical open sea conditions are briefly reviewed businger dyer flux gradient relationships and a charnock wind stress formula fit the empirical data and are dimensionally consistent these have been solved by an iterative method and the results are presented in a tabular form suitable for climatological calculations from marine wind and temperature data

new perspective on aptian carbon isotope stratigraphy data from δ13c records of terrestrial organic matter carbon isotope analyses were performed on detrital woody materials in aptian mid cretaceous marine sediments of central hokkaido northern japan a positive 13cwood excursion from 25 4 to 21 8 following a remarkable negative isotope shift is recognized in the early aptian and a small positive anomaly is also found in the latest aptian this 13cwood profile is exactly in phase with the 13ccarbonate curve from a pacific guyot when the age of the guyot carbonates is revised using published sr isotope stratigraphies the highly conformable 13c profiles of pacific and hokkaido sections suggest that 13c compositions of aptian marine and terrestrial carbon reservoirs changed simultaneously by the same amplitude within the ocean atmosphere biosphere system fluctuation patterns of tethyan 13ccarbonate curves are slightly different from those of pacific and hokkaido sections such differences in 13c profiles may be attributed to the local paleoceanographic setting of the aptian mediterranean tethys

scattering of coastal trapped waves by irregularities in coastline and topography abstract the scattering of freely propapting coastal trapped waves ctws by large variations in coastline and topography is studied using a numerical model which accomodates arbitrary density stratification bathymetry and coastline particular attention is paid to the role of stratification which in moderate amounts can eliminate backscattered free waves which occur theoretically in a barotropic ocean numerical simulations using widening and narrowing shelf topographies show that the strength of the forward scattering into transmitted ctw modes is proportional to a topographic warp factor which estimates the severity of the topographic irregularities the forward scattering is further amplified by density stratification within the scattering region itself the strengths of the scattered wave induced currents exhibit substantial variation over short spatial scales there is generally a marked intensification of the flow within the scattering region and rapid variations in phase on narrowing shelves

identification of sinkhole origin using surface geophysical methods dead sea israel abstract the western and eastern dead sea ds shores are hit by intensive sinkhole collapse during the last 30 years the first researchers have considered a piping model of sinkhole formation based on washing out fines by underground flows then it was proved by numerous boreholes and seismic refraction surveys that sinkholes along western shore are caused by dissolution of buried salt layers and collapse of the surface into dissolution caverns however signs of piping and subsurface flows were observed in some sinkhole sites in this paper we show that robust identification of sinkhole origin can be achieved when proper geophysical methodologies and their application are used we consider newe zohar site located in the southern part of the dead sea in order to analyse different signs of sinkhole formation models using various geophysical methods the seismic refraction method srfr enables us to discover the salt layer based on longitudinal wave velocity vp the multichannel analysis of surface waves masw method allows to determine the salt layer properties rigidity based on shear wave velocity vs finally the time electromagnetic tem method allows us to evaluate the degree of aggressiveness of groundwater with respect to salt based on bulk resistivity values here we analyse competitive models of sinkhole formation and suggest geophysical methods to determine the subsurface geomorphology we show that various geophysical methods should be applied in concert to explore the subsurface for the occurrence of salt as well as understanding sinkhole formation processes the underlying voids along the dead sea are shown to form primarily by salt dissolution with some cases of additional piping applying the right geophysical parameters for groundwater and salt sediments classification proves to be crucial for understanding the subsurface geomorphology

the australian coastal experiment a search for coastal trapped waves abstract the australian coastal experiment ace was conducted in the coastal waters of new south wales from september 1983 to 1984 the data obtained allow a detailed examination of the dynamics of flow on the continental shelf and slope and in particular allow a description of coastal trapped wave modes propagating within the coastal waveguide the trapped wave signal is contaminated by energy from the east australia current eddies approaching the continental slope however the data do allow a clear separation of the first three coastal trapped wave modes over the range of frequencies appropriate to the weather forcing band through that frequency range the phase speed is computed and an empirical dispersion relation determined for each mode the empirical dispersion relations compare well with the theoretical relations indicating that a large fraction of the variance in current velocities on the continental shelf can be accounted for by coastal trapped wave theory wind forcing of trapped waves is als

litho and biofacies of early cretaceous rudist bearing carbonate sediments in northeastern japan abstract carbonate blocks of late aptian lower cretaceous age occur in the lower yezo group of central hokkaido in northeast japan the shallow water carbonates were emplaced by gravity sliding and rock fall into a deep water flysch basin various lithofacies can be distinguished within the blocks including massive wackestone bedded packstone and micro oncoid grainstone containing corals rudists an oyster gastropods calcareous algae and an orbitolinid foraminifer facies and palaeoecological analyses suggest deposition of low energy biostromes and sand banks in open lagoonal and restricted environments with local higher energy shoals and beaches the presence of calcareous sandstones and abundant insoluble residues in limestones suggest deposition in an attached carbonate platform close to a supply of terrigenous material rather than deposition upon seamounts within an oceanic setting a narrow rimmed shelf in tropical subtropical conditions would have been the depositional environment for these carbonates which were subsequently deformed into blocks and transported into deep water as a result of the tectonic collapse of the platform