chemical composition and stratigraphic correlation of mesozoic basalt units of the newark basin new jersey and the hartford basin connecticut summary new major and trace element analyses of the messozoic basalts of the hartford basin of connecticut the talcott holyoke and hampden basalts indicate that the basalts are chemically very similar to the mesozoic basalts of the newark basin of new jersey the first second and third watchung basalts our geochemical data impose some constraints on any time stratigraphic correlation of the basalts in the two basins we suggest that the holyoke and second watchung basalts are fractionation products of a talcott first watchung parent magma we also suggest that the hampden and third watchung basalts are synchronous fractionation products of a magma unlike any of the eastern north american basalt types described in the literature but they may instead be the fractionation products of a magma resembling a magma of the same type as that of the mid atlantic ridge from a petrologic standpoint the most straight forward time stratigraphic interpretation is a one to one correlation of the three flows of the newark basin with the three flows of the hartford basin our geochemical and petrologic evidence is particularly supportive of time stratigraphic correlations between the first watchung and the talcott basalts and between the third watchung and the hampden basalts our data however are not inconsistent with the possibility that the second watchung may be slightly older than the holyoke basalt

effects of episodic rainfall on a subterranean estuary numerical simulations were conducted to examine the effect of episodic rainfall on nearshore groundwater dynamics in a tidally influenced unconfined coastal aquifer with a focus on both long yearly and short term daily behaviour of submarine groundwater discharge sgd and seawater intrusion swi the results showed non linear interactions among the processes driven by rainfall tides and density gradients rainfall induced infiltration increased the yearly averaged fresh groundwater discharge to the ocean but reduced the extents of the saltwater wedge and upper saline plume as well as the total rate of seawater circulation through both zones overall the net effect of the interactions led to an increase of the sgd the nearshore groundwater responded to individual rainfall events in a delayed and cumulative fashion as evident in the variations of daily averaged sgd and salt stored in the saltwater wedge quantifying the extent of swi a generalized linear model glm along with a gamma distribution function was developed to describe the delayed and prolonged effect of rainfall events on short term groundwater behaviour this model validated with results of daily averaged sgd and swi from the simulations of groundwater and solute transport using independent rainfall datasets performed well in predicting the behaviour of the nearshore groundwater system under the combined influence of episodic rainfall tides and density gradients the findings and developed glm form a basis for evaluating and predicting sgd swi and associated mass fluxes from unconfined coastal aquifers under natural conditions including episodic rainfall

submarine groundwater discharge driven nitrogen fluxes to long island sound ny terrestrial vs marine sources abstract bottom waters in smithtown bay long island sound ny are subject to hypoxic conditions every summer despite limited nutrient inputs from waste water and riverine sources while modeling estimates of groundwater inputs are thought to be insignificant terrestrial and marine fluxes of submarine groundwater discharge sgd were quantified to smithtown bay using mass balances of 222 rn 224 ra 226 ra and 228 ra during the spring and summer of 2014 2015 in order to track this seasonal transition period intertidal pore waters from a coastal bluff terrestrial sgd and from a barrier beach marine sgd displayed substantial differences in n concentrations and sources traced using a multi isotope approach 222 rn ra 15 n no 3 18 o no 3 no 3 in terrestrial sgd did not display any seasonality and was derived from residential septic systems and fertilizer marine sgd n concentrations varied month to month because of mixing between oxic seawater and hypoxic saline pore waters n concentrations were greatest during the summer when no 3 was derived from the remineralization of organic matter short lived 222 rn and 224 ra sgd fluxes were used to determine remineralized n loads along tidal recirculation flow paths while long lived 228 ra was used to trace inputs of anthropogenic n in terrestrial sgd 228 ra derived terrestrial n load estimates were between 20 and 55 lower than 224 ra derived estimates excluding spring 2014 228 ra may be a more appropriate tracer of terrestrial sgd n loads terrestrial sgd no 3 derived from 228 ra to smithtown bay varied from 1 40 12 8 10 6 mol n y 1 with comparable marine sgd no 3 fluxes of 1 70 6 79 10 6 mol n y 1 derived from 222 rn and 224 ra remineralized n loads were greater during the summer compared with spring and these may be an important driver toward the onset of seasonal hypoxic conditions in smithtown bay and western long island sound seawater recirculation through the coastal aquifer can rival the n load from terrestrial sgd from a heavily polluted aquifer

stratigraphic evolution of the late holocene ganges brahmaputra lower delta plain sediment cores from the ganges brahmaputra delta in bangladesh were examined for sedimentological character clay mineralogy elemental trends c n s and 14c geochronology to develop a model for the sedimentary sequence resulting from lower delta plain progradation in the late holocene a widespread facies succession from muddy sand to interbedded mud records progradation of shoal island complexes and the transition from subtidal to intertidal conditions mangrove vegetated islands and peninsulas represent the final phase of progradation a mottled mud that is deposited by penetration of turbid coastal water into the mangroves during high water events organic matter preservation is generally low 1 toc in most of these well drained deposits that are characterized by a permeable silt dominated granulometry clay mineralogy in the cores records the relative influence of smectite and kaolinite rich ganges sediments and illite and chlorite rich brahmaputra material the lower delta plain west of the modern river mouths was deposited as a ganges dominated delta in three phases since 5000 cal years bp with brahmaputra influence confined to the meghna estuary area and to the supratidal section of western delta deposits evolution of the lower delta plain in the late holocene was influenced by regional subsidence patterns in the tectonically active bengal basin which controlled distributary channel avulsion and migration and the creation of accommodation space

shallow water eruption fed mafic pyroclastic deposits along a paleoproterozoic coastline kangerluluk volcano sedimentary sequence southeast greenland abstract the 200 300 m thick volcano sedimentary sequence at kangerluluk is part of the psammite zone one of four major zones which constitute the 1 8 ga ketilidian orogen in south greenland three lithofacies are emphasized in the study 1 the conglomerate sandstone 2 the volcanic and 3 the pyroclastic lithofacies the 2 40 m thick conglomerate sandstone lithofacies represents a subaerial to subaqueous fan delta deposit matrix and clast supported conglomerates are interpreted as debris flow and longitudinal gravel bar deposits erosive based conglomerate channel fills attest to stream incision trough crossbedded sandstone interpreted as lunate megaripples planar bedded sandstone indicative of upper flow regime bar top sands and small scale trough crossbeds reflecting ripples follow up section form collectively with the conglomerate 0 40 2 50 m thick fining upward sequences the sandstone dominated unit up section from the conglomerates and composed of planar and low angle crossbeds minor ripples and graded beds as well as mudstone is indicative of a lower shoreface deposit below normal wave base the clastic sedimentary rocks are suggestive of a fan delta setting the 100 200 m thick volcanic lithofacies composed of pillowed and pillow brecciated lava flows is consistent with shallow water deposition interstratification of lava flows with both conglomerate sandstone and pyroclastic lithofacies intrusion of dykes into volcaniclastic rocks and peperite formation accentuate contemporaneity between volcanism and sedimentation and is a common feature of island arcs the 1 50 m thick pyroclastic lithofacies with sharp depositional contacts to the overlying volcanic and underlying conglomerate sandstone lithofacies was emplaced in a subaqueous setting the lithofacies is divided into a planar to crossbedded tuff lapilli tuff and a bedded lapilli tuff breccia whereby both deposits are inferred to result from shallow water surtseyan type eruptions the 5 15 m thick bedded lapilli tuff breccia with abundant bomb sag structures and graded beds is considered a result of subaqueous eruptions strong enough to form an insulating steam cupola characterized by ballistically emplaced bombs that rapidly collapsed allowing for transport via mass flow processes the deposits are considered proximal to the vent the 2 50 cm thick planar to crossbedded tuff lapilli tuff featuring abundant euhedral and broken crystals of feldspar 2cm and minor pyroxene 1 cm are massive graded crossbedded and stratified the planar but laterally discontinuous beds characterized by abundant low angle scours are interpreted as low to high concentration sediment gravity flows produced directly from subaqueous tephra jets that collapsed due to massive water ingestion local breccia size pyroclasts disrupting beds are interpreted as bomb sags the mafic eruption fed surtseyan type deposits postulated to be a subaqueous counterpart of cold subaerial base surges originate from subaqueous tuff cones formed along a rugged volcanic dominated shoreline featuring high energy fan deltas

some guidelines in reconstructing ancient sea conditions from wave ripplemarks abstract the collection of substantial field data on wave ripple mark spacing wavelength steepness grain size and symmetry index from the miocene burdigalian sandstones of western switzerland has allowed apparently close reconstruction of sea conditions results indicate however that ancient wave reconstructions must be restricted at present to data from relatively steep ripple marks vfi less than 7 5 i e vortex ripples data from the flatter ripple marks post vortex types formed at high oscillatory shear stresses do not provide reasonable estimates of wave conditions penecontemporaneous overwashing and or post depositional compaction ripple formation near the destruction condition rather than the threshold of sediment movement orbital diameters far exceeding ripple spacing and superimposed unidirectional currents are all factors which seriously affect wave reconstructions evaluation of ancient wave conditions provides insight into geologically important phenomena such as local water depth and basin size

fresh and saline groundwater discharge to the ocean a regional perspective 1 studies of groundwater flow in coastal aquifers often focus strongly on freshwater and investigate flow in a narrow 5 km zone surrounding the coastline this work was designed to place coastal flow in a regional context and to compare fresh and saline submarine groundwater discharge sgd for regional flow systems numerical flow and transport models were developed to estimate sgd associated with topography driven flow seawater recirculation and geothermal convection in a passive margin setting simulations were based on two cross sections of north carolina and sensitivity studies were used to explore the impact of varying hydraulic and transport parameters results suggest that saline flow associated with seawater recirculation and geothermal convection should be considered in studies of sgd studies limited to shallow topography driven flow may be justified in using small study areas but flow systems contributing to sgd may span at least 20 km surrounding the coast and continental slope

advective flow through the upper continental shelf driven by storms buoyancy and submarine groundwater discharge data from monitoring wells on the carolina usa continental shelf require a reevaluation of pore water exchange across the seafloor temperature salinity and 226ra data from 3 offshore wells require rapid and frequent pore water exchange to depths of several meters through sands and other permeable sediments the exchange is driven by tidal pumping storms buoyancy and submarine groundwater discharge tidal pumping causes semidiurnal temperature cycles in one well that can only be explained by rapid fluid flow the effect of large storms is evident in sudden temperature changes 2 4 m below the seabed in two wells these changes require considerable pore water exchange sudden cooling of the ocean may cause pore waters to become buoyant with respect to the ocean and trigger pore water convection to several meters depth as observed in one well the wells also display frequent large factor of ten changes in 226ra activity this requires a substantial input of 226ra enriched fluids to replace 226ra that is lost during exchange events these data support a fourth flow process which is groundwater seeping from the underlying limestone the pore spaces in the overlying sand provide a temporary reservoir for these fluids we conclude that pore water residence times in 2 4 m thick sands on this continental margin are on the order of a few months or less

theoretical wave modeling of large wave ripples in volcaniclastic sediments ordovician llewelyn volcanic group north wales abstract volcaniclastic sedimentary rocks of ordovician age underlying the garth tuff member of the capel curig volcanic formation north wales were deposited on a shallow marine shelf deposition at the capel curig anticline 2 km southwest of capel curig was on a high energy proximal offshore to foreshore analysis of large wave ripples and associated sedimentary structures suggests a shallow marine depositional environment above storm wave base and in water depths of 10 30 m this estimate of water depth from wave calculations is similar to that estimated by facies analysis

geologic influence on groundwater salinity drives large seawater circulation through the continental shelf observations of offshore freshened groundwater and saline groundwater discharge along continental shelves have important implications for water resources ecosystem function and the composition of the ocean but they cannot be explained by basic theory we show that these independent observations are linked and result from processes that drive variable density groundwater flow through the spatial heterogeneity that is ubiquitous in geologic formations we use lithologic data to develop geostatistical models that mimic the architecture of coastal aquifers simulation of groundwater flow and salt transport through these random realizations shows that heterogeneity produces spatially complex subsurface salinity distributions that extend tens of kilometers offshore even at steady state the associated density gradients drive high saline groundwater circulation rates that cannot be predicted by equivalent homogeneous models results suggest that these phenomena may be common along continental shelves potentially altering estimates of ocean chemical budgets and impacting coastal water management for future generations

the occurrence and chemical implications of geothermal convection of seawater in continental shelves 1 geothermal convection is an important driving force for fluid flow and diagenesis in carbonate platforms and the similar shape of continental shelves in general suggests that geothermal convection could occur in continental shelves around the world numerical models based on seven transects of the shelf off the east coast of north america were developed to bracket possible fluxes simulations assuming relatively permeable sediments medium grained carbonates failed to produce significant thermal variations suggesting that chemical tracers will be required to detect this flow in the field fluxes calculated assuming lower permeabilities fine grained carbonates between cape fear and the savannah river were approximately 3 orders of magnitude smaller than river discharge for the area a difference similar to that between global river discharge and hydrothermal convection at mid ocean ridges sediment diagenesis during geothermal convection in continental shelves thus has the potential to affect ocean chemical budgets including potassium calcium and magnesium

the influence of connected heterogeneity on groundwater flow and salinity distributions in coastal volcanic aquifers abstract geological heterogeneity is a key factor affecting rates and patterns of groundwater flow and the evolution of salinity distributions in coastal aquifers the hydrogeologic systems of volcanic aquifers are characterized by lava flows that can form connected geologic structures in the subsurface surface based geostatistical techniques were adopted to generate geologically realistic statistically equivalent model realizations of a hydrogeologic system based on that of the big island of hawaii conduit models the density dependent groundwater flow and solute transport code seawat was used to perform 3d simulations to investigate subsurface flow and salt transport through these random realizations statistically equivalent geological systems generated with sequential indicator simulation sis and equivalent homogeneous systems were also simulated for comparison simulation results show that conduit realizations tend to have more complex salinity distributions with larger mixing zones for which the center of mass is farther offshore compared to homogeneous and sis realizations the zone of groundwater discharge is also farther offshore than for homogeneous and sis models with higher point fluxes of both fresh and saline water and greater spatial variability this highlights the importance of the geometry of geologic features in coastal groundwater flow and solute transport processes in highly heterogeneous aquifers it also points to the importance of preferential flow with implications for both coastal groundwater resource management and solute fluxes to the ocean

downstream changes in sand composition roundness and gravel size in a short headed high gradient stream northwestern italy abstract we assessed changes in grain composition and roundness of the 1 2 and 2 3 size fractions of sand along a 16 km length of the graveglia river liguria italy to its mouth at the tyrrhenian sea and then for 1 km along the beach rocks exposed in the drainage area include ophiolites ribbon chert limestone shale sandstone and quaternary sands the erosion of shale and limestone bedrock yields large amounts of sand but sand grains of these rock types decrease rapidly in abundance downstream chiefly through dilution rather than abrasion carbonate rock fragments that reach the beach survive wave abrasion but most shale grains do not predictably monocrystalline and polycry talline quartz and chert are the most durable grain types but serpentine basalt and unidentified rock fragments also show significant resistance to both stream and wave abrasion polycrystalline quartz feldspar basalt serpentine sandstone and shale grains are more abundant in the coarser sand size fraction monocrystalline quartz carbonate rock fragments and unidentified rock fragments are more abundant in the finer sand size fraction and chert and plutonic rock fragments have no size preference a comparison of the outcrop areas of the different rock types with the corresponding percentages of different grain types present in each of three drainage areas indicates that shale which breaks down readily to silt and clay size particles and chert which does not readily break down into sand size fragments are underrepresented in the sands limestone and serpentine however are overrepresented in comparison to outcrop area in certain drainage areas the overrepresentation of limestone reflects in part a sampling bias sand was sampled adjacent to limestone outcrops but the overrepresentation of serpentine reflects its resistance to weathering compared to other aluminosilicates and its durability shale limestone and serpentine increase in roundness downstream and along the beach to a maximum limiting value of 5 rho units medium grained shale clasts attain high rounding in only a few kilometers of transport downstream decrease in gravel size follows an exponential formula that can be expressed in linear form using phi size size 0 1167 distance km 10 29

chemical signals from submarine fluid advection onto the continental shelf we report unambiguous signals of subsurface fluid input on the continental shelf 40 80 km from shore in water depths of 20 45 m the site of this input is near the continental shelf break off the south carolina coast between 32 33 n and 78 5 79 5 w repeated transects over this area reveal enrichments of 226ra 228ra and ba by factors of 3 4 above ambient ocean concentrations the short lived 223ra and 224ra are enriched by over an order of magnitude the ra and ba enrichments are not caused by up welling of deep water as no such 226ra or ba concentrations occur in the upper 2000 m of the atlantic ocean sediments in the region are largely relic sand and do not offer a viable source for 226ra 228ra and ba enrichments we conclude that the source is the discharge of submarine fluids enriched in 226ra 228ra and ba the salinity of water in the ra ba enriched zone is diluted by 0 2 0 6 relative to water at the same depth farther offshore pronounced salinity and density anomalies characterize one site of active discharge estimates of 226ra and ba concentrations in the fluids and the replacement time of water in the enriched zone suggest the fluid flux is similar to the summertime flow of major rivers in the area the region of ra ba enrichment is also characterized by a strong fluorescence signal indicating high concentrations of chlorophyll in the water it is probable that the leaking fluids supply nutrients that stimulate productivity in the bottom waters which are within the photic zone because the fluorescence signal is restricted to depths greater than 20 m it is unlikely that the signal could be recognized by satellite or aircraft sensors

early history of the atlantic ocean and gas hydrates on the blake outer ridge results of the deep sea drilling project leg 76 leg 76 of the deep sea drilling project achieved two major scientific objectives the first objective was met at site 533 where on the blake outer ridge gas hydrates were identified by geophysical geochemical and geological studies gas hydrate decomposition produced a volumetric expansion of 20 1 of gas volume to pore fluid volume this expansion exceeded by about a factor of four the volume of gas that could be released from solution in pore water under similar conditions the gas hydrate includes methane ethane propane and isobutane but apparently excluded normal butane and higher molecular weight hydrocarbons as predicted from gas hydrate crystallography for the first time marine gas hydrates were tested with a pressure core barrel the second objective was achieved when coring at site 534 in the blake bahama basin sampled the oldest oceanic sediments yet recovered the sequence of oceanic basement and overlying sediments documents the geologic history of the early stages of the opening of the north atlantic ocean in detail the oldest oceanic sediments are red claystones and laminated green and brown claystones of middle callovian age this finding supports the interpretation that the beginning of the modern north atlantic occurred in the early callovian 155 m y b p as much as 20 m y later in time than often previously thought

reconstruction of ancient sea conditions with an example from the swiss molasse ancient sea conditions can be estimated from the grain size spacing and steepness of preserved ripple marks the element of greatest uncertainty in such reconstructions is the relationship between near bed orbital diameter of water particles and the ripple spacing this relationship is simple for vortex ripples of high steepness but is problematical for the low steepness forms known as post vortex rolling grain or anorbital ripples the existence field for wave ripples is between the threshold velocity for sediment movement and the onset of sheet flow most low steepness forms occurring close to the bed planation threshold a range of maximum period of formative waves can be obtained using combinations of orbital diameter and orbital velocity assuming linear wave theory to be a reasonable approximation probable wave heights wave lengths and water depths can be investigated using the transformation of wave parameters in shallowing waters and the constraints on wave dimensions provided by the wave breaking condition given reasonable estimates of wave height crude estimates of wave power allow a comparison of ancient wave influenced sequences with modern counterparts wave ripple marks preserved in the upper marine molasse of western switzerland have been investigated results which are in agreement with regional geology suggest deposition in a seaway of approximately 100 km width where moderate period waves t 3 6 s were generated the depositional facies belts were adjusted to the prevailing waves tides and fluvial outflows

cyclic deposits and hummocky cross stratification of probable storm origin in upper cretaceous rocks of the cape sebastian area southwestern oregon abstract cyclic deposits containing hummocky cross stratification occur in the upper part of the cape sebastian sandstone of bourgeois 1980 a shallow marine transgressive sandstone of late cetaceous age on the southern oregon coast the cycles average 1 6 m in thickness and consist where complete of a lower hummocky cross stratified sandstone a middle planar and ripple bedded sandstone with a shale bed in its middle part and an upper bioturbated sandstone noteworthy features of the hummocky cross stratification include the presence of depositional domes in addition to scoured depressions the absence of significant bedform migration and the presence of a small proportion of dip angles greater than the angle of repose 34 in addition to the large proportion of low 15 deg dip angles the lower stratified fining upward part of the cycle up to the top of the shale bed is interpreted as having accumulated under conditions of initially great but gradually decreasing current velocity and deposition rate the currents probably had a strong oscillatory component and the depositional event is inferred to have been a storm the part of the planar and ripple bedded sandstone above the shale bed was probably deposited during relatively fair weather after the storm but before re establishment of a normal benthic fauna the bioturbated sandstone is interpreted to have been deposited during fair weather or during minor storms separated by long intervals of fair weather

groundwater flow in the ganges delta basu et al 1 1 reported that 2 1011 m3 year of groundwater flows directly into the bay of bengal an outflow equivalent to 19 of the discharge from the ganges brahmaputra river system they showed that this estimate of flow could have important consequences for the interpretation of

mixed convection and density dependent seawater circulation in coastal aquifers 1 density dependent circulation of seawater in coastal aquifers results in submarine groundwater discharge sgd across the seabed that is a mixture of terrestrial groundwater and former marine water in this study the controls of the relative amount of seawater to freshwater in sgd were investigated numerically using the feflow and sutra codes it was found that the key controls could be expressed in the form of a single nondimensional recirculation number that incorporates the combined effects of free convection forced convection and hydrodynamic dispersion on convective overturn within the coastal salt wedge anisotropy effects were incorporated into the recirculation number with limited success based on the principle of equivalent isotropic hydraulic conductivity the type of boundary condition employed along the seabed was shown to be important convective overturn was substantially increased if backward dispersion of salt into the aquifer from along the outflowing portion of the seabed boundary was prevented overall the results demonstrated a strong dependence of convective overturn on the aquifer dispersivities suggesting that results from numerical simulations are problematic to apply to real aquifer systems that typically exhibit uncertain scale dependent dispersion properties

quantifying hydrological and tidal influences on groundwater discharges into coastal waters 1 in coastal aquifers the dynamic mixing zone between intruding seawater and fresh groundwater constitutes a zone of salinity transition that may supply brackish groundwater along with chemical

cretaceous volcanism and jurassic magnetic anomalies in the nauru basin western pacific ocean the nauru basin contains a well documented pattern of late jurassic magnetic anomalies and a cretaceous volcanic complex that has not disturbed the older magnetic structure the following hypotheses are offered to explain this paradox the cretaceous basalts are normally and uniformly magnetized making them invisible to a surface towed magnetometer tension cracks and fractures associated with thermal uplift and or magma wedging provided pathways for the cretaceous magma through the jurassic basement without disrupting the jurassic magnetic structure the same tension cracks admitted sea water that convectively removed heat from the magnetic layer and thus maintained the jurassic basement below its magnetic blocking temperature for extended periods of time during intrusive thermal episodes finally the maximum uplift associated with cretaceous volcanism in the nauru basin could have been equal to but was probably something less than that associated with nearby seamount and atoll chains

the late jurassic tithonian a greenhouse phase in the middle jurassic early cretaceous cool mode evidence from the cyclic adriatic platform croatia well exposed mesozoic sections of the bahama like adriatic platform along the dalmatian coast southern croatia reveal the detailed stacking patterns of cyclic facies within the rapidly subsiding late jurassic tithonian shallow platform interior over 750 m thick ca 5 6 myr duration facies within parasequences include dasyclad oncoid mudstone wackestone floatstone and skeletal peloid wackestone packstone shallow lagoon intraclast peloid packstone and grainstone shoal radial ooid grainstone hypersaline shallow subtidal intertidal shoals and ponds lime mudstone restricted lagoon fenestral carbonates and microbial laminites tidal flat parasequences in the overall transgressive lower tithonian sections are 1 4ae5 m thick and dominated by subtidal facies some of which are capped by very shallow water grainstone packstone or restricted lime mudstone laminated tidal caps become common only towards the interior of the platform parasequences in the regressive upper tithonian are dominated by peritidal facies with distinctive basal oolite units and well developed laminate caps maximum water depths of facies within parasequences estimated from stratigraphic distance of the facies to the base of the tidal flat units capping parasequences were generally 4 m and facies show strongly overlapping depth ranges suggesting facies mosaics parasequences were formed by precessional 20 kyr orbital forcing and form parasequence sets of 100 and 400 kyr eccentricity bundles parasequences are arranged in third order sequences that lack significant bounding disconformities and are evident on accommodation fischer plots of cumulative departure from average cycle thickness plotted against cycle number or stratigraphic position modelling suggests that precessional sea level changes were small several metres as were eccentricity sea level changes or precessional sea level changes modulated by eccentricity supporting a global hot greenhouse climate for the late jurassic tithonian within the overall cool mode of the middle jurassic to early cretaceous

phenomena of pulsation tectonics related to the breakup of the eastern north american continental margin abstract new data from the recent ipod drilling of dsdp site 534 in the blake bahama basin give a definite age for the spreading center shift involved in the breakup of the north american atlantic margin a basal callovian age 155 m y is determined for the blake spur magnetic anomaly marking this spreadingcenter shift that signals the birth of the modern north atlantic ocean this is some 20 m y younger than previously thought an implication of this younger age for the blake spur event is that very high spreading rates are now required for the jurassic outer magnetic quiet zone along the north american margin this association of a relatively high spreading rate with a magnetic quiet zone is similar to that for the mid cretaceous and implies a link between the processes controlling plate spreading which are in the upper mantle and the processes controlling the magnetic field which are in the outer core a theory of pulsation tectonics involving the cyclic eruption of plumes of hot mantle material from the lowermost mantle could explain the correlation plumes carry heat away from the core mantle boundary and later reach the asthenosphere and lithosphere to induce faster spreading the pulse of fast spreading in the jurassic apparently followed the breakup of continents bordering the north atlantic ocean other pulses of fast spreading appear to correlate with major ocean openings on various parts of the globe implying that this might be a prevalent process rifting of passive margins may be controlled by the more fundamental global processes described by the theory of pulsation tectonics

wave formed structures and paleoenvironmental reconstruction clifton h e and dingier j r 1984 wave formed structures and paleoenvironmental reconstruction in b greenwood and r a davis jr editors hydrodynamics and sedimentation in wave dominated coastal environments mar geol 60 165 198 wave formed sedimentary structures can be powerful interpretive tools because they reflect not only the velocity and direction of the oscillatory currents but also the length of the horizontal component of orbital motion and the presence of velocity asymmetry within the flow several of these aspects can be related through standard wave theories to combinations of wave dimensions and water depth that have definable natural limits for a particular grain size threshold of particle movement and that of conversion from a rippled to fiat bed indicate flow velocity limits the ratio of ripple spacing to grain size provides an estimate of the length of the near bottom orbital motion the degree of velocity asymmetry is related to the asymmetry of the bedforms though it presently cannot be estimated with confidence a plot of water depth versus wave height h h diagram provides a convenient approach for showing the combination of wave parameters and water depths capable of generating any particular structure in sand of a given grain size natural limits on wave height and inferences or assumptions regarding either water depth or wave period based on geologic evidence allow refinement of the paleoenvironmental reconstruction the assumptions and the degree of approximation involved in the different techniques impose significant constraints inferences based on wave formed structures are most reliable when they are drawn in the context of other evidence such as the association of sedimentary features or progradational sequences

terrestrial originated submarine groundwater discharge through deep multilayered aquifer systems beneath the seafloor a large quantity of submarine groundwater discharge sgd of about 1000 m3 day 1 m 1 of the 600 km long shoreline of south atlantic bight has been estimated by moore global biogeochemical cycles 2010b 24 gb4005 doi 10 1029 2009gb003747 however there is great uncertainty in estimating the percentage of net land originated groundwater recharge of sgd moreover most previous studies considered the homogeneous case for the coastal superficial aquifers here we investigated the terrestrial originated sgd through a multilayered submarine aquifer system which comprises two confined aquifers and two semi permeable layers the inland recharge includes a constant part representing the annual average and a periodical part representing its seasonal variation an analytical solution was derived and used to analyse the distributions of the terrestrial originated sgd from the multilayered aquifers along the winyah bay transect south atlantic bight it is found that the width of the zone of sgd from the upper aquifer ranges from 0 8 to 8 0 km depending on the leakance of the seabed semi permeable layer a head of the upper aquifer at a coastline 1 0 m higher than the mean sea level will cause a sgd of 1 82 18 3 m3 day 1 m 1 from that aquifer as the seabed semi permeable layer s leakance varies from 0 001 to 0 1 day 1 providing considerable possibility for considerable land originated sgd seasonal terrestrial originated sgd variations predicted by the analytical model provide consistent explanation of the seasonal variation of 226ra observed by moore journal of geophysics 2007 112 c10013 doi 10 1029 2007jc004199 the contribution of the lower aquifer to sgd is only 1 2 12 of that of the upper aquifer copyright 2014 john wiley sons ltd

a reevaluation of submarine groundwater discharge along the southeastern coast of north america 1 new data of fluxes of radium isotopes and concentrations of radium in coastal groundwater enable an estimation of fluxes of submarine groundwater discharge sgd to a large section of the south atlantic bight sab the new fluxes are considerably greater than sgd fluxes to this region estimated earlier the annual average total sgd fluxes which represent a range of salinity are 3 times greater than the river fluxes the highest fluxes of radium and sgd occur in the summer off the coast of georgia when scaled per kilometer of shoreline the sgd flux is the same for the coastlines of onslow bay nc 140 km a section of the south atlantic bight from onslow bay nc to cresent beach florida united states 600 km and the entire atlantic ocean 75 000 km the fact that each independent estimate is based on different methods and assumptions gives confidence to the results these sgd fluxes are not restricted to the shoreline but occur throughout the continental shelf they are important for supplying not only radium but also nutrients carbon metals and freshwater to these coastal waters citation moore w s 2010 a reevaluation of submarine groundwater discharge along the southeastern coast of north america global biogeochem cycles 24 gb4005 doi 10 1029 2009gb003747

seasonality of major redox constituents in a shallow subterranean estuary abstract the subterranean estuary ste the subsurface mixing zone of outflowing fresh groundwater and infiltrating seawater is an area of extensive geochemical reactions that determine the composition of groundwater that flows into coastal environments this study examined the porewater composition of a shallow ste

seawater sr isotope variation over the past 300 kyr and influence of global climate cycles the past 300 000 years have been characterized by glacial inter glacial fluctuations accompanied by glacio eustatic changes in sea level and changes in continental erosion arising from varying low latitude rainfall and river drainage here we use measurements of strontium isotopes in foraminifera and corals to place limits on variations in the sr isotope composition of sea water in response to these changing inputs we find small variations of about 20 p p m in the 87sr 86sr ratio which for the foraminiferal record seem to follow a cycle close to the 100 kyr periodicity seen for a number of other climate related phenomena these are superimposed on a general increase in87sr 86sr through the cenozoic to the present on short timescales these changes are likely to be controlled by variations in the global riverine sr flux and thus by weathering rates rather than in the hydrothermal sr flux at mid ocean ridges we show that transient variations over a 50 kyr timescale can be explained on the basis of the present day global drainage system in conjunction with the perturbations expected to accompany climate changes over the past 300 kyr

global estimate of submarine groundwater discharge based on an observationally constrained radium isotope model along the continental margins rivers and submarine groundwater supply nutrients trace elements and radionuclides to the coastal ocean supporting coastal ecosystems and increasingly causing harmful algal blooms and eutrophication while the global magnitude of gauged riverine water discharge is well known the magnitude of submarine groundwater discharge sgd is poorly constrained using an inverse model combined with a global compilation of 228ra observations we show that the sgd integrated over the atlantic and indo pacific oceans between 60 s and 70 n is 12 3 1013 m3 yr 1 which is 3 to 4 times greater than the freshwater fluxes into the oceans by rivers unlike the rivers where more than half of the total flux is discharged into the atlantic about 70 of sgd flows into the indo pacific oceans we suggest that sgd is the dominant pathway for dissolved terrestrial materials to the global ocean and this necessitates revisions for the budgets of chemical elements including carbon

a shallow marine volcaniclastic facies model an example from sedimentary rocks bounding the subaqueously welded ordovician garth tuff north wales u k abstract volcaniclastic sedimentary rocks bounding the ordovician garth tuff in north wales were deposited in a shallow marine setting adjacent to a magmatic arc the volcaniclastic sedimentary rocks are primarily of angular to euhedral quartz angular euhedral feldspar and volcanic rock fragments these grains are of a pyroclastic origin but have been reworked to various degrees sedimentary rock fragments rounded quartz muscovite biotite iron rich chlorite and various clay minerals occur in lesser amounts the sedimentary rocks can be divided into a proximal offshore to foreshore facies association poffa and an offshore to lower shoreface facies association olsfa the sand dominated poffa exposed near capel curig is characterized by large wave ripples hummocky cross stratification co sets of trough cross beds reactivation surfaces plane beds and graded turbidite layers in suspension deposited mudstone water depths calculated from bedding plane exposure of large wave ripples and determined by the presence of hummocky cross stratification and by facies association vary from a few meters to around 30 m 45 50 m theoretical maximum in a 45 m thick stratigraphic section beneath the tuff eight kilometers to the southeast the garth tuff is bounded by a thick sequence of suspension deposited laminated mudstone with thin graded beds of siltstone and fine grained sandstone this facies association olsfa represents the introduction of material by distal turbidites and by pelagic sedimentation the olsfa was deposited in water depths well below storm wave base possibly in excess of 200 m no evidence of storm waves or surface generated currents occur until over 40 m above the tuff this study documents marine sedimentary rocks deposited in water depths ranging from foreshore to offshore as the bounding facies of the garth tuff it is thus reasonable to conclude that the garth tuff was emplaced and welded in water depths greater than the thickness of the tuff in the area of this study

global depletion of groundwater resources 1 in regions with frequent water stress and large aquifer systems groundwater is often used as an additional water source if groundwater abstraction exceeds the natural groundwater recharge for extensive areas and long times overexploitation or persistent groundwater depletion occurs here we provide a global overview of groundwater depletion here defined as abstraction in excess of recharge by assessing groundwater recharge with a global hydrological model and subtracting estimates of groundwater abstraction restricting our analysis to sub humid to arid areas we estimate the total global groundwater depletion to have increased from 126 32 km3 a 1 in 1960 to 283 40 km3 a 1 in 2000 the latter equals 39 10 of the global yearly groundwater abstraction 2 0 6 of the global yearly groundwater recharge 0 8 0 1 of the global yearly continental runoff and 0 4 0 06 of the global yearly evaporation contributing a considerable amount of 0 8 0 1 mm a 1 to current sea level rise

combined geophysical and analytical methods to estimate offshore freshwater extent abstract offshore fresh groundwater is increasingly suggested as a potential water resource for onshore human demands in many cases onshore pumping already draws significant fresh groundwater from offshore however offshore aquifers and the extent of offshore freshwater are usually poorly characterised due to data scarcity this study combines geophysical data hydraulic information and a first order mathematical analysis to investigate offshore freshwater extent in the gambier embayment australia a large seismic data set combined with onshore and offshore bore log geological profiles are used to explore the regional offshore hydro stratigraphy aquifer hydraulic parameters and onshore heads are obtained from onshore investigations a novel application of archie s law geophysical data and onshore hydrochemical data provide useful insights into the salinity profiles within four offshore wells these are compared to steady state sharp interface estimates of the freshwater extent obtained from a recently developed analytical solution albeit using simplified conceptual models salinities derived from resistivity measurements indicate that in the south of the study area pore water with total dissolved solids tds of 2 2 g l 1 is found up to 13 2 km offshore offshore pore water salinities are more saline in the northern areas most likely due to thinning of the offshore confining unit the analytical solution produced freshwater saltwater interface locations that were approximately consistent with the freshwater saltwater stratification in two of the offshore wells although analytical uncertainty is high this investigation provides a leading example of offshore freshwater evaluation applying multiple techniques demonstrating both the benefit and uncertainty of geophysical interpretation and analytical solutions of freshwater extent

fluidization of wet sediments during the emplacement and cooling of various igneous bodies during the emplacement and cooling of igneous bodies fluidization of wet sediment by water vapour may occur by heating or by pressure relief during the opening of fractures momentary fluidization causes sediment reconstitution and local transport continuous fluidization can result in substantial sediment displacement theoretical considerations show that fluidization due to heating is not likely to occur at depths where pressure is much greater than 312 bars studies of the emplacement of sills of andesite ayrshire fluid rhyolite ramsey island and viscous rhyolite moelwyn hills recognize a wide range of phenomena attributable to wet sediment fluidization and in places modify existing interpretations the transgressive bases of the subaqueously welded ash flow tuffs of the capel curig volcanic formation are consistent with emplacement attended by fluidization of the subjacent sediment evidently fluidization is a means by which large volumes of wet sediment can be replaced by igneous material with minimal disturbance of the remaining host also fluidization can result in exceptionally complex contact relationships between sedimentary host and intrusive rocks and can cause fractures formed during cooling to be thoroughly pervaded by sediment fluidization is commonly associated with the formation of peperites

magnitudes of submarine groundwater discharge from marine and terrestrial sources indian river lagoon florida 1 magnitudes of terrestrial fresh and marine saline sources of submarine groundwater discharge sgd are estimated for a transect across indian river lagoon florida two independent techniques seepage meters and pore water cl concentrations show terrestrial sgd decreases linearly to around 22 m offshore and these techniques together with a model based on the width of the outflow face indicate a cumulative discharge of between 0 02 and 0 9 m3 d per meter of shoreline seepage meters and models of the deficiencies in 222rn activity in shallow sediments indicate marine sgd discharges of roughly 117 m3 d per meter of shoreline across the entire 1800 m wide transect two surface streams nearest the transect have an average discharge of about 28 m3 d per meter of shoreline marine sgd is thus 4 times greater then surface water discharge and more than 2 orders of magnitude greater than terrestrial sgd the magnitude of the terrestrial sgd is limited by the amount of regional precipitation evaporation recharge and groundwater usage while marine sgd is limited only by processes circulating marine water into and out of the sediments the large magnitude of marine sgd means that it could be important for estuarine cycling of reactive components such as nutrients and metals with only slight modification from estuarine water compositions the small magnitude of terrestrial sgd means that large differences from estuarine water composition would be required to affect chemical cycling

hydrodynamics and sedimentation in wave dominated coastal environmentsreconstruction of ancient sea conditions with an example from the swiss molasse ancient sea conditions can be estimated from the grain size spacing and steepness of preserved ripple marks the element of greatest uncertainty in such reconstructions is the relationship between near bed orbital diameter of water particles and the ripple spacing this relationship is simple for vortex ripples of high steepness but is problematical for the low steepness forms known as post vortex rolling grain or anorbital ripples the existence field for wave ripples is between the threshold velocity for sediment movement and the onset of sheet flow most low steepness forms occurring close to the bed planation threshold a range of maximum period of formative waves can be obtained using combinations of orbital diameter and orbital velocity assuming linear wave theory to be a reasonable approximation probable wave heights wave lengths and water depths can be investigated using the transformation of wave parameters in shallowing waters and the constraints on wave dimensions provided by the wave breaking condition given reasonable estimates of wave height crude estimates of wave power allow a comparison of ancient wave influenced sequences with modern counterparts wave ripple marks preserved in the upper marine molasse of western switzerland have been investigated results which are in agreement with regional geology suggest deposition in a seaway of approximately 100 km width where moderate period waves t 3 6 s were generated the depositional facies belts were adjusted to the prevailing waves tides and fluvial outflows

tectonics global changes in sea level and their relationship to stratigraphical sequences at the us atlantic continental margin of geological the principal factors that control the extent of seas through geological time are vertical movements of the lithosphere and global changes in sea level the relative height of the sea surface determines the facies and the thickness of sediments that can accumulate in a sedimentary basin backstripping studies show that the primary factors affecting the subsidence of rifted sedimentary basins are thermal contraction following heating and thinning of the lithosphere at the time of rifting and sedimentary loading factors such as compaction palaeobathymetry erosion and global sea level changes also contribute but their combined affects are small compared to those of thermal contraction and sedimentary loading simple models have been constructed which combine the effects of sedimentary loading and thermal contraction with those of compaction sub aerial erosion and global changes in sea level in the models it was assumed that the lithosphere was heated and thinned by stretching at the time of rifting sedimentary loading occurs by flexure of a lithosphere that progressively increases its flexural rigidity with age following rifting and that sediment compaction and bathymetry change across a basin but do not vary significantly with geological time furthermore different assumptions were made on the magnitude of curves of global sea level changes and the relationship between denudation rate and regional elevation the models show that tectonics in the form of thermal contraction of the lithosphere and flexure and slowly varying global changes in sea level can explain a number of the stratigraphic features of the us atlantic continental margin in this paper some of the implications of these results are examined for studies of a sea level changes through geological time and b the maturation history of continental margin basins

isolated pods of subaqueous welded ash flow tuff a distal facies of the capel curig volcanic formation ordovician north wales acidic welded tuffs of the capel curig volcanic formation were deposited from ash flows that transgressed from a proximal subaerial to a distal submarine environment isolated pods of welded tuff enveloped by marine sediments represent a distal facies of the formation deposited beyond the limits of the continuous ash flow tuff sheets various mechanisms for the separation of the tuff pods from a parent flow are discussed and it is concluded that it is most likely that the formation of the pods was due to disruption of a subaqueous ash flow during transport rather than by downslope collapse at the front of a previously deposited ash flow tuff sheet

offshore continuation of coastal groundwater systems predictions using sharp interface approximations and variable density flow modelling analytical sharp interface solutions and numerical variable density flow and transport modelling are used to study how far into the offshore the influence of meteoric continental groundwater systems extends under steady state flow and transport conditions results show that factors which favour the development of an extensive fresh water wedge in the offshore are 1 a high head or fresh water discharge at the coastline 2 a thick semi confined high permeability submarine aquifer 3 optimum but not necessarily maximum and minimum values for the thickness and permeability of the confining layer near the seafloor respectively sharp interface models tend to overpredict the seaward extent of fresh water considerably because in distal parts upward seepage rates through the overlying confining layer are too small to prevent salinisation by diffusion from the overlying sea and ensuing convective mixing by density differences within underlying aquifers the overprediction is particularly large for relatively low heads at the coastline and low permeabilities of the confining layer under favourable conditions fresh water connected to continental flow systems is predicted to occur up to several tens of kilometers offshore comparison of model predictions with observational data demonstrates that relatively fresh submarine pore waters off the coasts of new jersey us and suriname south america occur too far offshore to be explained by active flow systems indicating that they are paleo waters which formed during the pleistocene when sea levels were lower than at present

submarine groundwater discharge effects of hydrogeology and of near shore surface water bodies submarine groundwater discharge is investigated numerically for a confined aquifer considering three types of permeability distribution uniform anisotropic and heterogeneous lognormal as well as for an aquifer in which a surface water body is embedded the latter case corresponds to aquifers with lagoons flat lakes or wetlands near the coast the numerical simulations are performed using the code fast c 2d developed by holzbecher 1998 for the confined aquifer the portion of recirculated seawater in submarine groundwater discharge and the length of the recirculation zone are investigated the parameters influencing these variables in the case of homogeneous aquifer isotropic or anisotropic are discussed further the validity of a linear relationship between the submarine groundwater discharge and the flux of terrestrial groundwater toward the sea proposed by destouni and prieto 2003 is investigated as far as possible our results are compared with results presented by smith 2004 which were obtained using different codes the investigation of a heterogeneous model aquifer concerns the influence of the variability of the permeability distribution on the portion of recirculated seawater and is performed by means of monte carlo analyses finally for coastal aquifers in which surface water bodies are embedded the main flow features are investigated particularly the pathway of terrestrial groundwater to the sea the flux of groundwater of marine origin to the surface water body the recirculation of seawater and the flux from the surface water body to the sea have been considered the parameters influencing these fluxes which are important for the transfer of pollutants and tracers from the groundwater to the surface water and to the near shore seawater are discussed

a subaqueous welded tuff from the ordovician of county waterford ireland abstract the metal man tuff mmt from the ordovician of county waterford ireland was emplaced and welded in water depths greater than the thickness of the pyroclastic flow the mmt is the basal member of the middle tramore volcanic formation mtvf of the 5 km thick tramore group the mmt consists of a 10 m thick basal graded zone that represents a pyroclastic flow consisting of angular clasts of black mudstone pumice gray flow banded rhyolite and pink massive rhyolite set in a matrix of non deformed ash shards and pumice maximum grain size grades from large cobbles and small boulders to pebbles the basal 10 30 cm is depleted with respect to the largest boulders resulting in an inversely graded basal layer the basal graded zone passes upward into a transition zone with a strong eutaxitic foliation defined by elongated fiamme of mudstone and flattened pumice overlying this is an upper welded zone with a pronounced eutaxitic foliation columnar jointing flattened ash shards and shards deformed around phenocrysts and spheroids the presence of these features indicate that the deposit is welded was hot and was in motion as the shards deformed the mmt represents a pyroclastic flow that was a hot primary product of an eruption rather than re mobilized cold pyroclastic debris the mmt is bounded by suspension deposited fine grained tuff tuffaceous mudstone and terrigenous mudstone deposited below storm wave base many of the mudstone horizons contain brachipod faunas from shelf depth water nowhere in the 5 km thick tramore group is there terrigenous sandstone evidence of unidirectional flowing water nor any indication of shoreline alluvial environments or subaerial exposure it thus seems reasonable to conclude that the mmt was emplaced and welded subaqueously the geochemistry of the mmt is typical of other high silica 70 78 wt sio2 rhyolite from the ordovician of ireland the chemistry of the mmt is consistent from top to bottom allowing it to be distinguished from associated syndepositional intrusive rock and fine grained tuffs

heterogeneity induced mixing and reaction hot spots facilitate karst propagation in coastal aquifers the data provided in the included folders are results directly taken from simulations originating from comsol multiphysics all data are provided as text files each text file includes coordinate data and the raw values for the variable of interest presented in the manuscript and supporting information the files provided are separated into folders for homogeneous equivalent cases and heterogeneous cases for each of these folders the data is further subdivided by the variance of the hydraulic conductivity field finally the data is organiyed according to the output variable of interest

rethinking the use of seabed sediment temperature profiles to trace submarine groundwater flow submarine groundwater fluxes across the seafloor facilitate important hydrological and biogeochemical exchanges between oceans and seabed sediment yet few studies have investigated spatially distributed groundwater fluxes in deep ocean environments such as continental slopes heat has been previously applied as a submarine groundwater tracer using an analytical solution to a heat flow equation assuming steady state conditions and homogeneous thermal conductivity these assumptions are often violated in shallow seabeds due to ocean bottom temperature changes or sediment property variations here heat tracing analysis techniques recently developed for terrestrial settings are applied in concert to examine the influences of groundwater flow ocean temperature changes and seabed thermal conductivity variations on deep ocean sediment temperature profiles temperature observations from the sediment and bottom ocean water on the scotian slope off eastern canada are used to demonstrate how simple thermal methods for tracing groundwater can be employed if more comprehensive techniques indicate that the simplifying assumptions are valid the spatial distribution of the inferred groundwater fluxes on the slope suggests a downward groundwater flow system with recharge occurring over the upper middle slope and discharge on the lower slope we speculate that the downward groundwater flow inferred on the scotian slope is due to density driven processes arising from underlying salt domes in contrast with upward slope systems driven by geothermal convection improvements in the design of future submarine hydrogeological studies are proposed for thermal data collection and groundwater flow analysis including new equations that quantify the minimum detectable flux magnitude for a given sensor accuracy and profile length

volcaniclastic sedimentation in and around an ordovician subaqueous caldera lower rhyolitic tuff formation north wales the lower rhyolitic tuff formation of ordovician age in north wales records the collapse infilling and subsequent resurgence of a volcanic caldera with an original diameter of about 15 km this volcanic center controlled patterns of volcaniclastic sedimentation providing enough topographic relief for both a shallow lagoon depositional basin within the caldera and a source of sediment derived from the rim within the caldera sediment consists of tuffaceous laminated siltstone and immature coarse grained volcaniclastic sandstone containing plane beds ripple cross laminations symmetrical wave ripples and hummocky cross stratification coarse grained matrix supported conglomerate layers and layers of ash flow tuffs are also present these sediments accumulated in shallow water above fair weather wave base conglomerate units represent debris flows from the caldera rim a nearby shoreline and elevated areas associated with resurgent domes sedimentation outside of the caldera consisted of deposition of background suspension and volcanic ash suspension and turbidite deposition on a pyroclastic apron the outer margin of the apron was dominated by fine grained suspension and turbidite deposition whereas the inner margin of the apron contains hummocky cross stratification and other evidence of reworking by episodic storm waves local highs with associated shallow water sedimentation existed outside the caldera even though deposited in high energy marine environments all sedimentary rocks are both texturally and mineralogically very immature this textural immaturity differs from the typical very mature marine sediments and was caused by rapid depositional rates and a local volcanic sediment source

geologic effects on groundwater salinity and discharge into an estuary summary submarine groundwater discharge sgd can be an important pathway for transport of nutrients and contaminants to estuaries a better understanding of the geologic and hydrologic controls on these fluxes is critical for their estimation and management we examined geologic features porewater salinity and sgd rates and patterns at an estuarine study site seismic data showed the existence of paleovalleys infilled with estuarine mud and peat that extend hundreds of meters offshore a low salinity groundwater plume beneath this low permeability fill was mapped with continuous resistivity profiling extensive direct sgd measurements with seepage meters n 551 showed fresh groundwater discharge patterns that correlated well with shallow porewater salinity and the hydrogeophysical framework small scale variability in fresh and saline discharge indicates influence of meter scale geologic heterogeneity while site scale discharge patterns are evidence of the influence of the paleovalley feature beneath the paleovalley fill fresh groundwater flows offshore and mixes with saltwater before discharging along paleovalley flanks on the adjacent drowned interfluve where low permeability fill is absent fresh groundwater discharge is focused at the shoreline shallow saltwater exchange was greatest across sandy sediments and where fresh sgd was low the geologic control of groundwater flowpaths and discharge salinity demonstrated in this work are likely to affect geochemical reactions and the chemical loads delivered by sgd to coastal surface waters because similar processes are likely to exist in other estuaries where drowned paleovalleys commonly cross modern shorelines the existence and implications of complex hydrogeology are important considerations for studies of groundwater fluxes and related management decisions

hydrothermal recharge and discharge across 50 km guided by seamounts on a young ridge flank hydrothermal circulation within the sea floor through lithosphere older than one million years myr is responsible for 30 of the energy released from plate cooling and for 70 of the global heat flow anomaly the difference between observed thermal output and that predicted by conductive cooling models 1 2 hydrothermal fluids remove significant amounts of heat from the oceanic lithosphere for plates typically up to about 65 myr old3 4 but in view of the relatively impermeable sediments that cover most ridge flanks5 it has been difficult to explain how these fluids transport heat from the crust to the ocean here we present results of swath mapping heat flow geochemistry and seismic surveys from the young eastern flank of the juan de fuca ridge which show that isolated basement outcrops penetrating through thick sediments guide hydrothermal discharge and recharge between sites separated by more than 50 km our analyses reveal distinct thermal patterns at the sea floor adjacent to recharging and discharging outcrops we find that such a circulation through basement outcrops can be sustained in a setting of pressure differences and crustal properties as reported in independent observations and modelling studies

an overview of the sedimentary geology of the bengal basin in relation to the regional tectonic framework and basin fill history abstract the bengal basin in the northeastern part of indian subcontinent between the indian shield and indo burman ranges comprises three geo tectonic provinces 1 the stable shelf 2 the central deep basin extending from the sylhet trough in the northeast towards the hatia trough in the south and 3 the chittagong tripura fold belt due to location of the basin at the juncture of three interacting plates viz the indian burma and tibetan eurasian plates the basin fill history of these geo tectonic provinces varied considerably precambrian metasediments and permian carboniferous rocks have been encountered only in drill holes in the stable shelf province after precambrian peneplanation of the indian shield sedimentation in the bengal basin started in isolated graben controlled basins on the basement with the breakup of gondwanaland in the jurassic and cretaceous and northward movement of the indian plate the basin started downwarping in the early cretaceous and sedimentation started on the stable shelf and deep basin and since then sedimentation has been continuous for most of the basin subsidence of the basin can be attributed to differential adjustments of the crust collision with the various elements of south asia and uplift of the eastern himalayas and the indo burman ranges movements along several well established faults were initiated following the breakup of gondwanaland and during downwarping in the cretaceous by eocene because of a major marine transgression the stable shelf came under a carbonate regime whereas the deep basinal area was dominated by deep water sedimentation a major switch in sedimentation pattern over the bengal basin occurred during the middle eocene to early miocene as a result of collision of india with the burma and tibetan blocks the influx of clastic sediment into the basin from the himalayas to the north and the indo burman ranges to the east rapidly increased at this time and this was followed by an increase in the rate of subsidence of the basin at this stage deep marine sedimentation dominated in the deep basinal part while deep to shallow marine conditions prevailed in the eastern part of the basin by middle miocene with continuing collision events between the plates and uplift in the himalayas and indo burman ranges a huge influx of clastic sediments came into the basin from the northeast and east throughout the miocene the depositional settings continued to vary from deep marine in the basin to shallow and coastal marine in the marginal parts of the basin from pliocene onwards large amounts of sediment were filling the bengal basin from the west and northwest and major delta building processes continued to develop the present day delta morphology since the cretaceous architecture of the bengal basin has been changing due to the collision pattern and movements of the major plates in the region however three notable changes in basin configuration can be recognized that occurred during early eocene middle miocene and plio pleistocene times when both the paleogeographic settings and source areas changed the present basin configuration with the ganges brahmaputra delta system on the north and the bengal deep sea fan on the south was established during the later part of pliocene and pleistocene and delta progradation since then has been strongly affected by orogeny in the eastern himalayas pleistocene glacial activities in the north accompanied sea level changes in the bay of bengal

stratigraphy and structure of southern blake plateau northern florida straits and northern bahama platform from multichannel seismic reflection data approximately 2 100 km of 24 fold multichannel seismic reflection data reveal much about the subsurface geology for a large part of the continental margin east of florida discordance between the westward dipping pre breakup sediments and the eastward sloping basement along the edge of the blake plateau is interpreted as an effect of a splinter of continental margin derived from the african plate by a spreading center jump in the middle jurassic early rifting centered under the main part of the blake plateau became inactive as a spreading center jump shifted the active rift to east of the present blake escarpment along the blake spur magnetic anomaly in the northern florida straits the data reveal that the breakup unconformity underlain by triassic lower jurassic arkosic volcaniclastics extends from southern florida to the western bahama banks these volcaniclastics are associated with the rift crust of intermediate nature formed just prior to and during breakup of the north american and african continental plates back reef platform deposits of limestones dolomites and evaporites of late jurassic to albian age extend from the blake bahama escarpment westward beneath florida these deposits formed what once was a megabank extending over a wider area than the present smaller isolated bahama banks the formation of the florida straits and bahama channels occurred during the cenomanian transgression only on the present bahama banks and florida platform did shallow water carbonate deposition persist to maintain a shallow bank environment evidence of recurring scour by current erosion is found in the florida straits erosional events apparently occurred in the middle cenomanian middle paleocene early middle eocene and eocene oligocene which coincidentally are times of lower eustatic sea level according to vail et al 1977a this evidence of florida current scour indicates that the current was present as far back as the cenomanian major faulting appears to have dropped the northeast providence channel relative to the western bahamas after the albian submarine erosion and bank buildup created the channels and smaller relief features like great abaco knoll beginning in about the cenomanian a carbonate bank margin and reef complex was present along the bahama escarpment since the middle jurassic apparently these organic buildups seeded on originally shallow structural relief on oceanic basement created during the spreading center jump to the position of the blake spur magnetic anomaly the bank margin apparently has retreated at least 15 km from a late jurassic earliest cretaceous position now marked by a bench below the au unconformity active faulting occurred along the great abaco fracture zone at least through the late cretaceous and perhaps into the tertiary these relatively young tectonic events together with the post albian faults in providence channel indicate interactions between the atlantic and caribbean plates and that extensions of faulting have taken place far to the northeast of cuba and the greater antilles

the driving forces of porewater and groundwater flow in permeable coastal sediments a review abstract advective flows rapidly transport water solutes and particles into and out of permeable sand beds and significantly affects the biogeochemistry of coastal environments in this paper we reviewed the drivers of porewater and groundwater advection in permeable shelf sediments in an attempt to bridge gaps among different disciplines studying similar problems we identified the following driving forces 1 terrestrial hydraulic gradients 2 seasonal changes in the aquifer level on land moving the location of the subterranean estuary 3 wave setup and tidal pumping 4 water level differences across permeable barriers 5 flow and topography induced pressure gradients 6 wave pumping 7 ripple and other bed form migration 8 fluid shear 9 density driven convection 10 bioirrigation and bioturbation 11 gas bubble upwelling and 12 sediment compaction while these drivers occur over spatial scales ranging from mm to km and temporal scales ranging from seconds to years their ultimate biogeochemical implications are very similar i e they are often a source of new or recycled nutrients to seawater and transform organic carbon into inorganic carbon drivers 2 12 result in no net water input into the ocean taking all these mechanisms into account we conservatively estimate that a volume equivalent to that of the entire ocean is filtered by permeable sediments at time scales of about 3000 years quantifying the relative contribution of these drivers is essential to understand the contribution of sediments to the global cycles of matter