formation deformation and chertification of systematic clastic dykes in a differentially lithified carbonate multilayer sw iberia algarve basin lower jurassic this work presents original field evidence for tectonically controlled calciclastic dyke injection and subsequent chertification in shelf carbonates during rifting in the south westernmost part of the eurasian continent in the early pliensbachian it is shown by the detailed description of tectonic structures faults and joints stratigraphic discontinuities and by the distribution orientation and morphology of the injected dykes of calciclastic sands into fine grained carbonates that these soft sediment deformation structures were tectonically controlled extensional tectonics developed vertical tensile joints in semi lithified fine grained limestones permitting upward and downward injection of loose calciclastic sands forming clastic dykes the frequency of injection structures along strata was constrained by the thickness of the layer into which the injection was occurring which implies an elastic behaviour however the curvi planar shapes of the dykes and drop like nodules attests the ductile behaviour of the fractured limestones indicating transition from elastic to ductile response to deformation with time the multi layered system consists of just two lithotypes the two display different mechanical behaviours which evolved in time to more brittle conditions as lithification progressed as shown by the cataclastic faulting and jointing of the previously formed soft sediment deformation structures and strata under an analogous stress regime the injection dykes were disrupted by a short lived episode of compression after which tectonic extension resumed still in the lower pliensbachian sometime before the deposition of the upper pliensbachian a pervasive selective event of chertification occurred only the calciclastic sandy layers dykes and nodules were substituted by silica thus enhancing the mechanical contrast between the primary sedimentary structures and the soft sediment deformation structures all the described events occurred during a time interval of approximately 2 myr as constrained by ammonoid stratigraphy

role of overpressures and in situ stresses in fault controlled hydrocarbon migration a case study abstract two wells no 1 and no 2 separated by 2 km and situated in the upper prospective zone of a tertiary basin in south east asiat cross the same mio pleistocene shaly sandy series from 1500 m downwards these series are subject to significant overpressures related to an active margin comparison of well data in terms of sonic compaction profiles anomalous pressures and temperatures has provided evidence of both a positive pressure and a temperature anomaly below a vertical depth of 1800 m in well 2 this anomaly is closely associated with the presence of liquid hydrocarbons in the 1900 2000 m reservoir interval the confirmed deep source of these fluids and the amounts that have migrated during a short time interval can be explained only by the transitory dynamics of active transfers along faults and fractures the episodic nature of this movement is the result of hydromechanical mechanisms in which the interactions between the high pressure regime and principal in situ stresses appear to be fundamental the processes which induce open faulting and fluid pressure build up in the direction of reservoirs with lower pressure regimes occur preferentially during phases of lateral tectonic stress relaxation as soon as the effective minimum stress component becomes negative the analysis of this case study gives a better understanding of the dynamic phenomena involving secondary hydrocarbon migration and caprock efficiency the results obtained will help to optimize the overpressure prediction approach in comparable geological contexts

development and flow structures of sand injectites the hind sandstone member injectite complex carboniferous uk abstract the hind sandstone member of the carboniferous craven basin occurs within a thick succession of marine mudstone and is here interpreted as a sandstone injectite complex injectites take the form of i sills ii upwards emplaced dykes iii downwards emplaced dykes iv a sedimentary laccolith and v sandstone bodies remobilised in situ the remobilised and injected sand originated from small turbidite scour fills and potentially a more significant sand body such as a submarine slope gully fill the sedimentary laccolith appears to jack up the units it injects and is filled by sandstone with a chaotic fabric suggestive of brecciation of partly cemented sand the laccolith and sill dominated nature are suggestive of relatively shallow remobilisation sills are commonly laterally gradational with upwards emplaced dykes and in some cases these feed apparently downwards emplaced dykes a series of flow structures are preserved within some of the injectites and these provide clues to the emplacement history crack propagation direction is inferred from the orientation of undulating crests developed on the upper and lower surfaces of injectites peak flow is indicated by scour marks resembling flute and tool marks which are superimposed onto these undulating surfaces internal flow structures highlighted by pyrite mineralistion record the waning stage of injection the observed flow structures suggest that the apparent crack propagation direction was generally oblique to the peak flow and nearly perpendicular to the direction of late stage fluidised sediment flow crack propagation relates to the local stress field whilst injection flow may be related to the local pore pressure distribution recognition of this suite of structures may provide a useful interpretational tool for other injectites in both core and outcrop pore fluid overpressure which drove injection developed through the migration of petroleum and mineralising fluids from the underlying bowland shales and older limestones a complex brecciated fracture network within the mudstones underlying the injectites records fluid migration pathways sliced blocks and thin sections from injectites reveal flow structures defined by iron pyrite mineralisation the trigger is here related to growth of compressional structures and associated syn sedimentary slumps which occur at the same stratigraphic level as the injectites

climate control of decadal scale increases in apparent ages of eogenetic karst spring water abstract water quantity and quality in karst aquifers may depend on decadal scale variations in recharge or withdrawal which we hypothesize could be assessed through time series measurements of apparent ages of spring water we tested this hypothesis with analyses of various age tracers 3h 3he sf6 cfc 11 cfc 12 cfc 113 and selected solute concentrations dissolved oxygen do no3 mg and so4 from 6 springs in a single spring complex ichetucknee springs in northern florida over a 16 yr period these springs fall into two groups that reflect shallow short group 1 and deep long group 2 flow paths some tracer concentrations are altered with cfc 12 and cfc 113 concentrations yielding the most robust apparent ages these tracers show a 10 20 yr monotonic increase in apparent age from 1997 to 2013 including the flood recession that followed tropical storm debby in mid 2012 this increase in age indicates most water discharged during the study period recharged the aquifer within a few years of 1973 for group 2 springs and 1980 for group 1 springs inverse correlations between apparent age and do and no3 concentrations reflect reduced redox state in older water positive correlations between apparent age and mg and so4 concentrations reflect increased water rock reactions concentrated recharge in the decade around 1975 resulted from nearly 2 m of rain in excess of the monthly average that fell between 1960 and 2014 followed by a nearly 4 m deficit to 2014 this excess rain coincided with two major el nino events during the maximum cool phase in the atlantic multidecadal oscillation although regional water withdrawal increased nearly 5 fold between 1980 and 2005 withdrawals represent only 2 5 of ichetucknee river flow and are less important than decadal long variations in precipitation these results suggest that groundwater management should consider climate cycles as predictive tools for future water resources

investigation of young water inflow in karst aquifers using sf6 cfc 3h he 85kr 39ar and stable isotope components abstract karst aquifers are known for their wide distribution of water transfer velocities from this observation a multiple geochemical tracer approach seems to be particularly well suited to provide a significant assessment of groundwater flows but the choice of adapted tracers is essential in this study several common tracers in karst aquifers such as physicochemical parameters major ions stable isotopes and 13c to more specific tracers such as dating tracers 14c 3h 3h 3he cfc 12 sf6 and 85kr and 39ar were used in a fractured karstic carbonated aquifer located in burgundy france the information carried by each tracer and the best sampling strategy are compared on the basis of geochemical monitoring done during several recharge events and over longer time periods months to years this study s results demonstrate that at the seasonal and recharge event time scale the variability of concentrations is low for most tracers due to the broad spectrum of groundwater mixings the tracers used traditionally for the study of karst aquifers i e physicochemical parameters and major ions efficiently describe hydrological processes such as the direct and differed recharge but require being monitored at short time steps during recharge events to be maximized from stable isotopes tritium and cl contents the proportion of the fast direct recharge by the largest porosity was estimated using a binary mixing model the use of tracers such as cfc 12 sf6 and 85kr in karst aquifers provides additional information notably an estimation of apparent age but they require good preliminary knowledge of the karst system to interpret the results suitably the cfc 12 and sf6 methods efficiently determine the apparent age of baseflow but it is preferable to sample the groundwater during the recharge event furthermore these methods are based on different assumptions such as regional enrichment in atmospheric sf6 excess air and flow models among others 85kr and 39ar concentrations can potentially provide a more direct estimation of groundwater residence time conversely the 3h 3he method is inefficient in the karst aquifer for dating due to 3he degassing

clastic dykes in over consolidated tills evidence for subglacial hydrofracturing at killiney bay eastern ireland abstract a swarm of vertical gravel filled dykes up to 6 m high and several decimetres wide cut through an over consolidated till at killiney bay the dykes are rooted in a gravel layer and many display plumes of clastic debris ejected into the overlying sediments burst out structures such features have not previously been described these clastic dykes are interpreted as the infillings of hydrofractures which formed when water pressures in the basal gravel layer exceeded the overburden pressure and tensile shear strength of the capping till the burst out structures extend up to 7 m from the tops of the dykes and provide strong evidence for forceful upward flow evidence suggests that the hydrofractures formed subglacially probably during a minor re advance their presence in late devensian 26 13 ka bp tills with an irish sea provenance irish sea till may have important implications for the subglacial hydrology of the last irish sea ice sheet these hydrofractures cannot form in unconsolidated glacimarine sediment and their presence precludes a glacimarine origin for these deposits they greatly affect the geotechnical properties of irish sea tills in particular providing very permeable routes through otherwise impermeable layers with important consequences in situations elsewhere in the irish sea basin where they have been used as aquicludes in landfill and low level nuclear waste disposal sites

a giant 5 3 107 m3 middle miocene c 15 ma sediment mound m1 above the siri canyon norwegian danish basin origin and significance abstract a large scale enigmatic mound structure m1 has been discovered in middle miocene strata of the norwegian danish basin c 10 km east and updip of the central graben it is located about 1 km beneath the seabed and clearly resolved by a 3d seismic data set focused on the deeper remobilised sand filled siri canyon m1 comprises two culminations up to 80 m high and up to 1400 m long constituting a sediment volume of some 5 3 10 7 m 3 it is characterized by a hard reflection at the top a soft reflection at the base differential compaction relative to the surrounding sediments and 10 ms twt velocity pull up of underlying reflections indicating a relatively fast mound fill attributed to the presence of sand within the mound internal seismic reflections are arranged in an asymmetric concentric pattern suggesting a progressive aggradation to the nw downstream to a mid miocene contour current system numerous elongated pockmarks occur in the upper miocene succession close to the mound and indicate that the study area was influenced by gas expulsion in the mid and late miocene the reflection configuration velocity dimensions regional setting and isolated location can best be explained by interpreting the mound as a giant sand volcano extruded 1 km upward from the siri canyon during the middle miocene c 15 ma the likely causes of this remarkable structure include gas charge and lateral pressure transfer from the central graben along the siri canyon reservoir while this is the first such structure described from this part of the north sea similar aged sand extrudites have recently been inferred from seismic observations in the north viking graben thus suggesting that the mid miocene was a time of widespread and intense sediment remobilization and fluid expulsion in the north sea

triassic latemar cycle tops subaerial exposure of platform carbonates under tropical arid climate the triassic latemar platform in the dolomites italy is the site of several ongoing controversies perhaps the most interesting debate focuses on apparent cyclic deposition within the latemar platform whose nature and duration are still open to debate further disagreement concerns the lack of meteoric diagenesis related isotope shifts at cycle tops that bear circumstantial petrographic evidence for subaerial emergence here an evaluation of the nature of latemar cycle tops is presented combining evidence from previous work and new field petrographic and geochemical data cycle tops are ranked according to increasing exposure duration and spatial extent type i surfaces lacking unequivocal evidence of prolonged supratidal conditions type ii dolomite caps formed in warm evaporitic intertidal lagoonal waters followed by exposure of perhaps intermediate duration type iii clastic rich red calcareous horizons with some showing platform wide extent representing prolonged supratidal conditions and type iv discontinuities in tepee belts genetically related to type ii and iii surfaces but likely representing shorter lived exposure stages petrographic and geochemical criteria indicate that most diagenesis occurred in the shallow marine and burial domain whilst an extensive meteoric overprint of cycle tops is lacking this is underlined by the scarcity of meteoric diagenetic fabrics such as gravitational cements that where present are here interpreted as marine vadose in origin the scarcity of carbon and oxygen isotope signatures commonly assigned to subaerial exposure stages is best explained in the context of mid triassic climate the low latitude tropical but arid setting of the latemar situated in the western extension of the tethys ocean its isolation from nearby continental areas and overall short term emergence episodes are in agreement with a limited degree of meteoric alteration of most cycle tops high amounts of aeolian clastic material beneath some cycle tops along with high fe and mn elemental abundances argue for intermittent subaerial conditions this study proposes an enhancement of the classical allan and matthews 1982 isotope model for subaerial exposure under strongly arid climates as the subaerial exposure nature of latemar cycle tops and therefore eustasy as the cause for cyclicity have been previously challenged due to the lack of meteoric induced isotopic signatures the outcome of this study is of significance for the ongoing latemar stratigraphic controversy

organic and inorganic carbon dynamics in a karst aquifer santa fe river sink rise system north florida usa spatiotemporal variations in dissolved organic carbon doc dissolved inorganic carbon dic major ions concentrations and other geochemical parameters including stable carbon isotopes of dic 13cdic were measured in surface water and deep and shallow well water samples of the santa fe river sink rise eogenetic karst system north florida usa three end member water sources were identified one doc rich dic poor 13cdic depleted one doc poor dic rich 13cdic enriched and one enriched in major ions given their spatiotemporal distributions they were presumed to represent soil water upper aquifer groundwater and deep aquifer water sources respectively using assumed ratios of na cl and so42 for each end member a mixing model calculated the contribution of each water source to each sample then chemical effects of biogeochemical reactions were calculated as the difference between those predicted by the mixing model and measured species concentrations in general carbonate mineral dissolution occurred throughout the sink rise system surface waters were net autotrophic and the subsurface was in metabolic balance i e no net doc or dic production or consumption however there was evidence for chemolithoautotrophy perhaps by hydrogen oxidizing microbes at some deep aquifer sites mineralization of this autochthonous natural dissolved organic matter ndom led to localized carbonate dissolution as did surface water derived ndom supplied to shallow well sites during the highest flow periods this study demonstrates linkages between hydrology abiotic and microbial processes and carbon dynamics and has important implications for groundwater quality karst morphologic evolution and hydrogeologic projects such as aquifer storage and recovery in karst systems

groundwater flow beneath ice sheets part ii its impact on glacier tectonic structures and moraine formation abstract meltwater flowing as groundwater from beneath the margin of an ice sheet determines the distribution of sub surface heads and effective pressures a subglacial groundwater flow model is used together with an ice sheet loading model to compute the magnitudes and directions of the principal effective stresses in the subsurface from which the distribution of different types of sub surface failure in the subglacial and proglacial zones are deduced zones of hydrofracturing shear fracture and pervasive shear failure are distinguished beneath the ice sheet divide area intact rocks of high tensile strength may fail hydrofracturing and liquefaction are two coupled processes which lead to the formation of upward filled and downward filled sediment dykes and till wedges quicksand conditions are developed where strong vertical seepage pressures occur producing sediment diapirism it is suggested that subglacial permeability magnitude may be the product of a self organising process certain types of moraine extrusion moraines are suggested to be a consequence of upward movement and surface extrusion of sediment driven by rising groundwater it is suggested that groundwater over pressure associated with narrow proglacial permafrost plates are conductive to the formation of large push moraines and that many large ancient and modern examples are produced in this setting

the geometry and emplacement of conical sandstone intrusions conical sandstone intrusions with a geometry comparable with that of many igneous sills have been identified using 3d seismic data from large areas of the north sea and faeroe shetland basins these intrusions are of reservoir scale ranging from 100 to 2000 m or so in diameter 50 300 m in height and 1 80 m in thickness aperture they are concentrated in specific stratigraphic intervals in the cenozoic fills of both basins two geometrical end members are recognised and defined here apical cones and flat based bowls the former consist of inward dipping conical inclined sheets meeting at a prominent apex and the latter of similarly dipping discordant margins climbing from the edges of a concordant sheet both end members are associated with domal folds that are interpreted as resulting from the hydraulic elevation of the overburden during intrusion and which are analogous to similar structures associated with bowl shaped igneous sills measurements of aperture versus distance exhibit systematic relationships with the structural relief of these folds offering a potentially predictive method for estimation of sandstone intrusion aperture and reservoir volume prior to drilling a growth model for these end member geometries is presented drawing on existing theory for igneous sill emplacement aperture versus distance plots x are used to illustrate two contrasting models for aperture inflation during propagation but these require much further data before any specific growth model can be adopted

subtidal carbonate cycles implications for allocyclic vs autocyclic controls thick successions of repetitive metre scale subtidal carbonate cycles require that short term sedimentation rates approximate long term accumulation rates in order to maintain submergence below peritidal depths intrinsic processes such as storm and wave reworking and redistribution may act to inhibit aggradation into the zone of optimal carbonate production the presence of subtidal vs peritidal carbonate cycles may be a function of energy regime that in turn may relate to platform morphology the ultimate control on stacked subtidal cycles appears to be eustasy acting in concert with intrinsic processes such as storm and wave reworking

condensation processes in shallow platforms abstract sequence stratigraphy allows elucidation of the time space relationships of deposits in sedimentary basins however the relative distribution of unconformities and condensed sections can neither be used as diagnostic criteria for particular palaeogeographic settings nor as indicators of maximum regional transgressions condensation processes also occur in the shallowest portions of platforms and during maximum regression episodes three separate processes of condensation are here distinguished stratigraphic sedimentary and taphonomic these three categories of condensation can be used to analyze patterns of sediment distribution and also to estimate lateral and vertical variations in sedimentation rates contrary to the usual interpretation the maximum values of rate of sedimentation and degree of accommodation of sediments as well as the highest relative sea level occur in the lowest levels of the shallowing upward sequences the distinction between these condensation processes allows one to predict that the degree of sedimentary and stratigraphic condensation will be higher towards the distal portions of the platforms whereas the stratigraphic condensation processes without sedimentary condensation will show the maximum intensity and frequency in the shallowest portions of the platforms

sand injectites network as a marker of the palaeo stress field the structural framework and the distance to the sand source example in the vocontian basin se france a large sand injectite network is very well exposed in the area of bevons southeast france the associated sandstone turbiditic channel fill and the host marls are the aptian albian rocks of the vocontian basin the sand injection network is composed of dykes sills and sedimentary laccoliths ranging in thickness from mm to pluri m the dykes and sills have vertical and horizontal lengths of up to and over 100 m and 1 km respectively outcrop observations show that the architecture and morphology of the sand injectites in the marls is governed by the local stress field during injection pre existing faults the host rock lithology compaction and distance to the potential sand source s the main set of dykes is oriented n50 60 perpendicular to the minimum compressive stress 3 during sand injection two other sets of dykes are intruded along pre existing syn sedimentary faults oriented n140 150 set 2 and n90 set 3 during the apto cenomanian interval sills and dykes thin laterally away from their potential sand sources and thin laterally away from them the vertical thickness variations of the dykes and wings are more complex as thinning away from the sand sources is often compensated by thickening toward the palaeo surface based on field observations and measurements we characterized the 3d architecture of the sand injectites and showed that the injectites probably formed due to a forceful injection from an overpressured sand body sealed by low permeability lithologies

formation of high frequency sequences and their bounding surfaces case study of the eocene yegua formation texas gulf coast usa abstract short term variations in accommodation and sediment supply on the continental shelf cause imbalances within longer term dynamic equilibrium conditions these imbalances result in the deposition of high frequency sequences the eocene yegua formation of the texas gulf coast is made up of six such sequences which have average durations of 0 8 million years or less they formed in response to distinct variations in the rate and quantity of sediment supply increases and decreases in the average grain size carried into the basin relative sea level position and the capacity of basinal energy regimes to transport and rework sediments each sequence may be characterized by the mix of particular regime conditions which were dominant during its deposition if the rate of sediment supply and the average grain size were more significant factors than the rate of relative sea level change and the capacity for basinal transport then the sequence was supply dominated and was characterized by fluvio deltaic deposition progradation of parasequences and river mouth bypassing onto the shelf and slope if instead relative sea level rise and basinal transport were the dominant factors the sequence was accommodation dominated and was characterized by estuarine and wave dominated deposition retrogradation of parasequences and shoreface bypassing onto the shelf when the accommodation and supply factors were in equilibrium sequences containing both fluvial and estuarine deposits characterized by aggradational parasequence stacking were deposited no two consecutive sequences in the yegua were dominated by the same mix of regime conditions therefore the sequence boundaries are important indicators of changes in regime conditions all of the boundaries are highly correlatable well constrained regional marine flooding surfaces flooding of the shelf thus apparently either causes or occurs as a result of a readjustment between sediment supply and accommodation continuous readjustments between these factors result in long term equilibrium conditions

inter comparison exercises on dissolved gases for groundwater dating 1 goals of the exercise and site choice validation of the sampling strategy abstract two international inter comparison exercises devoted to dissolved gases and isotope analyses in groundwater used as tools for groundwater dating were organized in 2012 in france ides universite paris sud cnrs and osur universite rennes 1 cnrs the goal was to compare sampling and analytical protocols through results obtained by the community of groundwater dating laboratories the two exercises were gdat1 on three supply boreholes in a homogeneous sand aquifer of fontainebleau paris basin france and gdat2 on two supply boreholes shallow and deep in a fractured rock aquifer in french brittany this two step exercise is the first exercise which included a large number of gases and isotopes usually used in groundwater as dating tools and also permit to discuss the uncertainties related to sampling protocols issuing from each laboratory methods the two tests allowed 31 laboratories from 14 countries to compare their protocols for both sampling and analyses this paper presents the participants and parameters measured and focuses on the validation of the sampling strategy two laboratories analyzed cfc and sf6 samples collected at regular intervals during the sampling operations in order to verify water homogeneity the results obtained by the two reference laboratories along with monitoring of field parameters showed no clear trend of gas concentration or physic chemical properties it can be concluded that the pumped groundwater composition remained constant during sampling this study also shows the potential for relatively constant pumped groundwater composition from a specific well despite the complexity and or mixing processes that may occur at a larger scale in the aquifer

exchange of water between conduits and matrix in the floridan aquifer flow through carbonate aquifers may be dominated by conduits where they are present by intergranular or fracture porosity where conduits are missing or may occur in conduits and matrix porosity where both are well developed in the latter case the exchange of water between conduits and matrix could have important implications for water management and hydrodynamic modeling an extensive conduit system has been mapped by dye trace studies and cave diving exploration at the santa fe sinkrrise system located in largely unaltered rocks of the floridan aquifer of north central florida in this area the santa fe river flows underground at the river sink and returns to the surface 5 km to the south at a first magnitude spring called the river rise limited data show that discharge is greater by 27 96 at the river rise than at the sink and that the downstream increase in discharge is inversely related to discharge of the river natural so 2y 4 concentrations indicate that 25 of the water discharging from the rise originates from the sink during low flow conversely so 2y and other solute concentrations indicate that most of the water discharging from the rise originates from 4 the sink during floods ar 40 decrease in na q and cl y concentrations over a 5 1r2 month period at a down gradient water supply well may reflect flow of dilute flood water from the conduits into and through the matrix at rates estimated to be between 9 and 65 mrday calcium concentrations remain constant through time at the well although flood waters have 90 lower ca 2q concentrations than ground water perhaps reflecting dissolution of the matrix rocks this apparent exchange of water between matrix and conduits is important for regional ground water quality and dissolution reactions q 2001 published by elsevier science b v

cycle anatomy and variability in the storm dominated type cincinnatian upper ordovician coming to grips with cycle delineation and genesis although parasequence and sequence are scale independent terms they are frequently applied only to specific scales of cycles for example meter scale cycles are commonly assumed to be parasequences or pacs in the upper ordovi cian kope and fairview formations of northern kentucky we examined a succession of 50 meter scale cycles that have been variously interpreted as deepening upward shallowing upward or showing no relationship with water depth our analysis shows that these cycles characterized by shifts in storm bed proximality are highly variable in their thickness and internal construction most cycles are best considered high frequency sequences because deepening upward intervals are common and many cycles contain evidence of abrupt basinward shifts in facies as expected at sequence boundaries a minority fit the parasequence model of shallowing upward cycles bounded by flooding surfaces larger 20 m scale cycles are defined by systematic thickening and thinning trends of meter scale cycl

relative sea level change climate and sequence boundaries insights from the kimmeridgian to berriasian platform carbonates of mount saleve e france the present study analyses the stratal architecture of the late jurassic kimmeridgian to early cretaceous berriasian sedimentary succession of mount saleve e france and four berriasian stratigraphic intervals containing four sequence boundary zones reflecting lowering trends of the relative sea level evolution massive kimmeridgian limestones characterized by the presence of colonial corals appear to be stacked in an aggrading pattern these non bedded thick deposits which are interpreted to have formed in balance between relative sea level rise and carbonate accumulation suggest a keep up transgressive system above well bedded tithonian to berriasian peritidal carbonates reflect a general loss of accommodation these strata are interpreted as a highstand normal regressive unit during the early phase of this major normal regression the vertical repetition of upper intertidal lower supratidal lithofacies indicates an aggrading depositional system this is in agreement with an early stage of a highstand phase of relative sea level the berriasian sequence boundary zones investigated up to 4 m thick developed under different climatic conditions and correspond to higher frequency forced and normal regressive stages of relative sea level changes according to the classical sequence stratigraphic principles these sequence boundary zones comprise more than one candidate surface for a sequence boundary three sequence boundary zones studied in early berriasian rocks lack coarse siliciclastic grains contain a calcrete crust as well as marly levels with higher abundances of illite with respect to kaolinite and exhibit fossilized algal microbial laminites with desiccation polygons these sedimentary features are consistent with more arid conditions a sequence boundary zone interpreted for the late berriasian corresponds to a coal horizon the strata above and below this coal contain abundant quartz and marly intervals with a higher kaolinite content when compared to the illite content accordingly this late berriasian sequence boundary zone was formed under a more humid climate the major transgressive regressive cycle of relative sea level identified and the climate change from more arid to more humid conditions recognized during the late berriasian have been reported also from other european basins therefore the kimmeridgian to berriasian carbonate succession of mount saleve reflects major oceanographic and climatic changes affecting the northern margin of the alpine tethys ocean and thus constitutes a reliable comparative example for the analysis of other coeval sedimentary records in addition the stratigraphic intervals including sequence boundary zones characterized in this study constitute potential outcrop analogues for sequence boundary reflectors mapped on seismic profiles of subsurface peritidal carbonate successions the detailed sedimentological analyses provided here highlight that on occasions the classical principles of sequence stratigraphy developed on seismic data are difficult to apply in outcrop a sequence boundary reflector when seen in outcrop may present successive subaerial exposure surfaces which formed due to high frequency sea level changes that were superimposed on the longer term trend of relative sea level fall

natural cf4 and sf6 on earth the occurrence of cf4 and sf6 in natural fluorites caf2 is reported contents are found to be typically 200 2000 ppt mass for cf4 and 50 100 ppt mass for sf6 cf4 and sf6 were also detected in granites where fluorite is an accessory mineral cf4 and sf6 thus possess a large reservoir in the continental crust that by degassing can sustain natural atmospheric background levels of 40 ppt mole and up to 0 01 ppt mole respectively the article also discusses how natural sf6 may cause interference in hydrological tracer studies

characterisation of interactions between a pre existing polygonal fault system and sandstone intrusions and the determination of paleo stresses in the faroe shetland basin abstract detailed analysis of 3d seismic data shows how hundreds of large scale conical sandstone intrusions interact with a polygonal fault network in the faroe shetland basin the intrusions were injected upwards during the late miocene through polygonally faulted claystones of eocene oligocene age three types of interactions are recognized 1 intrusions that are unaffected by polygonal faults 2 intrusions partially or fully intruded into fault planes and 3 intrusions arrested by polygonal faults type 2 intrusions are generally thinner taller and wider whereas those unaffected by faults are thicker and characterized by low dips of intrusive limbs wings it was found that type 2 intrusions preferentially intruded into faults striking nw se whereas type 3 intrusions were arrested by faults striking ne sw comparison of structural data and simple mechanical predictions allows paleostresses to be reconstructed at the time of intrusion we have established that the basin was undergoing anisotropic horizontal stresses at the time of intrusions in which h and h were oriented n145 e and n055 e respectively intrusion depth polygonal fault dips and strikes have been used to quantify paleostress intensity and to give a h v ratio close to 0 95 and a h h ratio of 0 8 these ratios support the conclusion that sandstone intrusion emplacement occurred just after a mid late miocene sse nnw n145 e compressional phase when the compression direction had decreased in intensity and became smaller than lithostatic stress v

sea level changes an integrated approach sea level changes an integrated approach in october 1985 sepm sponsored a four day conference entitled sea level changes an integrated approach the purpose of the conference was to provide a forum for an interdisciplinary exchange of ideas on sea level changes and to provide an opportunity for integrating various types of evidence in approaching unresolved issues the conference was successful in bringing together scientists from industry academia and government representing all of the major geosciences disciplines presentations of many new papers plus significant releases of data that were previously held proprietary provided fertile ground for discussion this much cited volume represents the best of the material presented at the conference includes the early vail chart

regional sand injectite architecture as a record of pore pressure evolution and sand redistribution in the shallow crust insights from the panoche giant injection complex california abstract observations on outcrop of a regionally developed sand injectite are used to infer and estimate the pore pressure conditions in the shallow crust that caused the fluidization and injection of tens of cubic kilometres of sand the estimated pore fluid pressures at the base of the injection complex at 1500 m burial depth below a regionally developed shale dominated seal are from 22 26 to 25 08 mpa which respectively correspond to 0 81 and 0 95 lithostatic pressure a theoretical basis for prediction of sand injection is defined and applied to the prediction of pore pressure at the time of sand injection the depth at which seal failure occurred and the density and granular content of the fluidized flow lateral variations in the style and abundance of sandstone intrusions are described and these all fit into a remarkably uniform tripartite division of parent units an intrusive complex and an extrusive complex a sill zone intrusions are dominated by sills occurs in a restricted stratigraphic interval 200 270 m thick location of the base of the sill zone is directly related to the thickness of the overburden and an isobaric surface at the time of sand injection the lithostatic equilibrium surface is defined at the base of the sill zone when the sills formed an extended period of supra lithostatic pressure occurred within the sill zone

geochemical and statistical evidence of recharge mixing and controls on spring discharge in an eogenetic karst aquifer summary information about sources of recharge distributions of flow paths and the extent of water rock reactions in karst aquifers commonly result from monitoring spring chemistry and discharge to investigate the relationship between spring characteristics and the complexities of karst aquifers we couple variations in surface and groundwater chemistry to physical conditions including river stage precipitation and evapotranspiration et within a sink rise system through a 6 km portion of the upper floridan aquifer ufa in north central florida principal component analysis pca of time series major element compositions suggests that at least three sources of water affect spring discharge including allogenic recharge into a swallet diffuse recharge through a thin vadose zone and water upwelling from deep within the aquifer the deep water source exerts the strongest influence on water chemistry by providing a majority of na mg2 k cl and so 4 2 to the system anomalously high temperature at one of several monitoring wells reflects vertical flow of about 1 m year mass balance calculations suggest diffuse recharge and deep water upwelling can provide up to 50 of the spring discharge however their contributions depend on head gradients between the conduit and surrounding aquifer matrix which are influenced by variations in precipitation et and river stage our results indicate that upwelling from deep flow paths may provide significant contributions of water to spring discharge and that monitoring only springs limits interpretations of karst systems by masking critical components of the aquifer such as water sources and flow paths these results also suggest the matrix in eogenetic aquifers is a major pathway for flow even in a system dominated by conduits

formation and deformation of subglacial intrusive clastic sheets in the dwyka formation of northern natal south africa abstract an arenaceous diamictite rests on fissile silty mudstone and argillaceous diamictite and is overlain by a laminated muddy siltstone east of helpmekaar in the dundee district of northern natal the argillaceous deposits originated either in the subglacial or proglacial zone of a partly grounded marine ice sheet where sediment was supplied by debris laden floating ice meltwater plumes and turbidity currents the arenaceous diamictite is the product of melt out debris released close to the grounding line of the ice sheet where it was subjected to overriding by the ice and slumping and redeposition by sediment gravity flow the laminated siltstone represents sediment that was deposited in a low energy setting by turbidity currents and suspension settling downslope from a retreating g ounding line dispersed ice rafted clasts occur in these fine grained deposits the upper surface of the arenaceous diamictite displays regularly spaced linear undulations that are parallel to the former iceflow direction as are corrugations in discrete subhorizontal slip planes in its upper part dike like bodies of this diamictite are found in the underlying mudstone and argillaceous diamictite these dikes or wedge shaped sheets of sandy diamictite are nearly vertical in their upper parts but at depth curl to the southeast to form sill like bodies these intrusive diamictites record a novel and previously undescribed form of subglacial bed shear by repeated hydraulic injections which shuffled the upper layers of the substrate to the south southeast bed compaction and shear beneath the grounded ice is recorded by folds in steepened portions of the clastic intrusive sheets and by pinch and swell and folded pinch and swell of the clastic sills displacement of steep folded sheet elements along subhorizontal slicken sided slip planes indicate that bed shear continued along spaced planes of slip during the process of compaction the corrugated and planar slip surfaces and the formation of the listric or spoon shaped intrusions are all shown to be different expressions of bed shear induced by traction from the overriding ice flowing to the southeast when it was temporarily grounded the base of an ice sheet flowing from land into the sea undergoes flow acceleration and forms a ramp where it decouples from the high friction substrate the arenaceous diamictite mound most likely to have developed beneath this ramp is inferred to have a structural core of sediments that have been squeezed and sheared and have slipped from beneath the ice in the tidal grounding zone

stacking pattern of cyclic carbonate platform strata lower cretaceous of southern apennines italy detailed sedimentological analysis of aptian albian shallow water carbonate platform strata from monte faito southern italy reveal composite sea level change the organization of the lithofacies and their related diagenetic overprint have allowed the identification of 50 elementary cycles they often show exposure related diagenetic features superimposed on subtidal deposits suggesting drops of relative sea level elementary cycles are grouped into 16 bundles forming six superbundles the hierarchical organization of the cycles are interpreted to be related to composite eustatic sea level fluctuations driven by the earth s orbital perturbation in the milankovitch frequency band moreover the systematic variation of superbundle thickness and the general evolution of the lithofacies reflects variations of accommodation potential defining longer term environmental changes different lithofacies forming elementary cycles are frequently separated by bedding planes that when viewed in a sequence stratigraphic context are interpreted as transgressive surfaces maximum flooding surfaces or sequence boundaries this allows the recognition of lowstand transgressive and highstand deposits in the cyclic units considering both the bundle superbundle ratio and the sequence stratigraphic interpretation of the superbundles a chronostratigraphic diagram illustrating both gaps at bundle level and their expected location along the section was created it establishes that the section developed over about 2 4 ma

flow of river water into a karstic limestone aquifer 2 dating the young fraction in groundwater mixtures in the upper floridan aquifer near valdosta georgia abstract tritium helium 3 3h 3he and chlorofluorocarbon cfcs cfc 11 cfc 12 cfc 113 data are used to date the young fraction in groundwater mixtures from a karstic limestone aquifer near valdosta georgia where regional paleowater in the upper floridan aquifer receives recharge from two young sources the flow of withlacoochee river water through sinkholes in the river bed and leakage of infiltration water through post eocene semi confining beds above the upper floridan aquifer in dating the young fraction of mixtures using cfcs it is necessary to reconstruct the cfc concentration that was in the young fraction prior to mixing the 3h 3he age is independent of the extent of dilution with older 3h free and 3hetrit free water the groundwater mixtures are designated as type 1 for mixtures of regional paleowater and regional infiltration water and type 2 for mixtures containing more than approximately 4 of river water the fractions of regional paleowater regional infiltration water and withlacoochee river water in the groundwater mixtures were determined from cl and 18o data for water from the upper floridan aquifer at valdosta georgia the chlorofluorocarbons cfc 11 and cfc 113 are removed by microbial degradation and or sorption processes in most anaerobic type 2 groundwater at valdosta but are present in some aerobic type 1 water cfc 12 persists in both so4 reducing and methanogenic water the very low detection limits for cfcs approximately 0 3 pg kg 1 permitted cfc 11 and cfc 12 dating of the fraction of regional infiltration water in type 1 mixtures and cfc 12 dating of the river water fraction in type 2 mixtures overall approximately 50 of the 85 water samples obtained from the upper floridan aquifer have cfc 12 based ages of the young fraction that are consistent with the 3h concentration of the groundwater because of uncertainties associated with very low 3h and 3he content in dilute mixtures 3h 3he dating is limited to the river water fraction in type 2 mixtures containing more than about 10 river water of the 41 water samples measured for 3h 3he dating dilution of 3h and low 3he concentration limited 3h 3he dating to 16 mixtures in which 3h 3he ages are defined with errors ranging from 2 to 7 5 a 1 after correction for dilution with assumed cfc free regional infiltration water and regional paleowater in the upper floridan aquifer adjusted cfc 12 ages agree with 3h 3he ages within 5 a or less in 7 of the 9 co dated type 2 mixtures tritium data and dating based on both cfc 11 and cfc 12 in type 1 mixtures indicate that travel times of infiltration water through the overlying post eocene semi confining beds exceed 35 a the cfc and 3h 3he dating indicate that the river fraction in most groundwater entered the groundwater reservoir in the past 20 to 30 a few domestic and municipal supply wells sampled intercept water younger than 5 a calculated velocities of river water in the upper floridan aquifer downgradient of the sinkhole area range from 0 4 to 8 2 m d radiocarbon data indicate that ages of the regional paleowater are on the 10 000 a time scale an average lag time of approximately 10 to 25 a is determined for discharge of groundwater from the surficial and intermediate aquifers above the upper floridan aquifer to the withlacoochee river

depositional cycles composite sea level changes cycle stacking patterns and the hierarchy of stratigraphic forcing examples from alpine triassic platform carbonates carbonate platform deposits record a complex interplay of numerous geodynamic variables of which eustasy subsidence and sediment accumulation are prime factors in determining both the kilometer scale depositional sequence scale and meter scale depositional cycle scale stratigraphic packaging in this study we looked particularly at composite eustasy that is superimposed sea level fluctuations with different frequencies defined as orders and different amplitudes and the role it plays in the linkage between meter scale cyclic stratigraphy and kilometer scale sequence stratigraphy specifically we have investigated the relationship between low frequency third order 1 10 m y period depositional cycles and their component high frequency fourth 0 1 1 m y and fifth 0 01 0 1 m y order cycles through detailed stratigraphic analyses of alpine triassic platforms complemented by computer modeling on the basis of our results we suggest that in general there exists a hierarchy of stratigraphic forcing driven by composite eustasy that results in organized stacking patterns thickness subfacies character early diagenetic attributes of high frequency typically fourth and fifth order shallow water carbonate cycles dictated by low frequency third order relative sea level effects we suggest that systematic vertical changes in stacking patterns of high frequency cycles across a larger depositional sequence are due to systematic and predictable differences in depositional space available during the rising and falling stages of a relative third order sea level change we also suggest that these systematic variations in cycle stacking patterns will exist regardless of the mechanism responsible for generating the high frequency cycles be it an autocyclic or allocyclic mechanism this approach has major implications for the use of high frequency fourth and fifth order cycle characteristics to identify third order cycles in outcrops and cores of shallow water carbonates where stratigraphic control may be less than desirable this would constitute a valuable bridge between cyclic stratigraphy at the meter scale and sequence stratigraphy at the seismic scale we present two examples from triassic buildups of the alps the ladinian latemar buildup and the norian dolomia principale where a systematic succession of high frequency cycle stacking patterns and early diagenetic features exists within an overriding third order cycle sequence reflecting the interplay of short term high frequency fourth fifth order eustasy and long term low frequency third order eustasy in accordance with the hierarchy of stratigraphic forcing central to the interpretation of these examples is the demonstration that true eustatic rhythms are recorded in the high frequency cyclicity as verified by time series analyses and the use of fischer plots these examples can be modeled by computer under conditions of lag depth constrained sedimentation uniform subsidence and composite eustasy we also present two examples one from the alpine triassic the norian lofer cyclothems and one from the pleistocene of south florida that lack both a systematic succession of high frequency cycle stacking patterns and identifiable composite rhythms in the stratigraphic record despite the existence of composite high frequency eustasy in these examples we call upon 1 local tectonic forcing in the form of short term deviations in subsidence via faulting lofer example and 2 large differences in the relative amplitudes of different orders of high frequency sea level oscillations pleistocene example to explain the lack of composite rhythms and we present computer simulations to illustrate the concepts an understanding of composite relative sea level changes and the potential for a hierarchy of stratigraphic forcing provides the link between cyclostratigraphy and sequence stratigraphy and also has important implications regarding the stratigraphy of early diagenesis

accommodation and supply a dual control on stratigraphic sequences abstract it is widely accepted that both eustatic and tectonically controlled regional changes of sea level have contributed to the record of stratigraphic sequences i suggest that environmental change be added as a third autonomous control sedimentologic principles clearly indicate that sequences and their systems tracts are controlled by the interplay of two rates the rate of change in accommodation space available for sedimentation and the rate of sediment supply sea level has direct control on accommodation but its influence on sediment supply is remote and easily overshadowed by environmental factors for instance the record of the most recent sea level rise is a transgressive systems tract where supply is low it is a prograding highstand systems tract in deltas where the supply is high examples of sequence boundaries generated by changes in sediment supply include tectonically driven shifts in sediment input into basins changes in ocean currents pulsating supply from failure of submarine slopes and drowning of carbonate platforms by environmental stress furthermore the stratigraphic sequences in fluviatile continental basins are physically removed from sea level induced changes in accommodation and must have formed by changes in the rate and pattern of supply subaerial exposure of marine sediments at the sequence boundary is a most important criterion for recognizing sea level cycles as opposed to supply cycles other criteria include downstepping of shelf breaks and characteristic patterns in the spacing of time lines within sequences some third order cycles ca 0 5 3 ma duration meet these criteria others do not cycle stacking patterns and the shifting facies belts on cratons indicate that many second and third order cycles lack pronounced exposure unconformities and represent gradual changes superimposed on more rapid shorter oscillations seismic data yield poor images of these gradational changes because they lack resolution seismic models of outcrops show that near the limits of resolution the seismic tool tends to portray rapid changes in facies and bed thickness i e lateral variations in supply as unconformities seismic unconformities do not necessarily correspond to unconformities in outcrop the succession of stratigraphic sequences is best considered a composite record of sea level and environmental change separating the various controls requires carefully planned experiments work on the oxygen isotope curve another proxy for sea level has set an example in this respect

bank storage in karst aquifers the impact of temporary intrusion of river water on carbonate dissolution and trace metal mobility abstract storms can trigger changes in river stage that alter the hydraulic gradients between rivers and adjacent aquifers in eogenetic carbonate karst aquifer systems storms enable river water to intrude 1 km into the adjacent aquifer systems for days to weeks this process is similar to bank storage of streams in siliciclastic sediments but can have longer temporal and larger spatial scales river intrusion triggers changes in mineral saturation states and redox conditions in the aquifer due to the input of low ph low specific conductivity spc and high dissolved organic carbon doc flood water to assess the effects of river intrusion into karst aquifers we measured spc temperature ph redox state and concentrations of dissolved major and trace elements through an intrusion event at madison blue spring in northern florida usa river water displaced groundwater in the conduit at least 1 km into the aquifer and flowed into the pores of the unconfined aquifer matrix distinct cl concentrations between river water and groundwater provide estimates for mixing fractions the location and magnitude of oxidation of organic matter in the subsurface controlled trace metal concentration redox state and saturation state of the water with respect to calcite sical organic matter oxidation in the phreatic conduits was limited by the terminal electron acceptors teas present in the conduit water calcite dissolution and trace metal sorption were limited by the lower surface area to porosity ratios in the conduits than the matrix organic matter oxidation was enhanced in the matrix by mixing with matrix waters with available do and no3 resulting in greater co2 production and calcite dissolution than in the conduit after the intruded river water discharged conditions remained more reducing in the aquifer than baseflow conditions due to the reduction of do and no3 in the matrix water the organic matter transported into the aquifer during river intrusion drives carbonate dissolution alters redox state and impacts trace metal mobility impacting groundwater and surface water quality

age distribution estimation for karst groundwater issues of parameterization and complexity in inverse modeling by convolution summary convolution modeling is useful for investigating the temporal distribution of groundwater age based on environmental tracers the framework of a quasi transient convolution model that is applicable to twodomain flow in karst aquifers is presented the model was designed to provide an acceptable level of statistical confidence in parameter estimates when only chlorofluorocarbon cfc and tritium 3 h data are available we show how inverse modeling and uncertainty assessment can be used to constrain model parameterization to a level warranted by available data while allowing major aspects of the flow system to be examined as an example the model was applied to water from a pumped well open to the madison aquifer in central usa with input functions of cfc 11 cfc 12 cfc 113 and 3 h and was calibrated to several samples collected during a 16 year period a bimodal age distribution was modeled to represent quick and slow flow less than 50 years old the effects of pumping and hydraulic head on the relative volumetric fractions of these domains were found to be influential factors for transient flow quick flow and slow flow were estimated to be distributed mainly within the age ranges of 0 2 and 26 41 years respectively the fraction of long term flow 50 years was estimated but was not dateable the different tracers had different degrees of influence on parameter estimation and uncertainty assessments where

facies associations and discontinuous surfaces in the syringothyris limestone formation of tethyan margin of gondwana kashmir abstract the early carboniferous sedimentation of the tethyan margin of gondwana in the kashmir himalaya represents alternating siliciclastic carbonate succession consisting of distinct stratigraphic sequences which are bounded by discontinuities the discontinuities in the sedimentation are related to environmental changes in the form of subaerial exposure subaqueous erosion subaqueous omission or changes in texture and facies these distinct surface zones or time significant boundaries can be correlated across the depositional platform low stand high stand and transgressive sedimentation units in the lower and middle parts of early carboniferous syringothyris limestone formation in banihal area have been recognised this is explained by superposition of high frequency and low amplitude sea level fluctuations on a large scale trend under greenhouse conditions during the early carboniferous period the facies associations present in the early carboniferous succession of the himalaya broadly represent intertidal peritidal shallow subtidal deeper subtidal off shore slope and deeper environments discontinuities that are interpreted as progradational retrogradational and aggradational phases of sedimentation bound these facies associations this formation represents continental margin depositional setting which is authenticated by deposition of siliciclastic sediments this marginal depositional setting is greatly affected by numerous dynamic processes including tectonic and other active sea as well as continental processes the records of all those processes in this formation reflect the eustatic changes in sea level these periodic eustatic changes have generated the various discontinuities stratigraphic sequences or systems tracts overall it appears that interplay of many processes such as sediment supply thermal and tectonic activity eustatic and climatic changes in the kashmir tethyan depositional basin generated these distinct depositional sequences during the early carboniferous period

a fractal model for the distribution of stratigraphic hiatuses several recent studies have suggested that there is a negative log linear relationship between sedimentation rates and the time span over which they are measured i e measured sedimentation rates are slow when measured over long time spans and rapid when measured over short time spans this relationship may be due to the inclusion of more and longer hiatuses over long time spans this paper proposes a mathematical model consistent with this relationship that is based upon the fractal cantor bar this model allows the estimation of the relative number and durations of stratigraphic hiatuses within a given section

mechanisms and controls on the formation of sand intrusions sandstone intrusions are found in all sedimentary environments but have been reported most commonly from deep water settings they also appear to be more frequently developed in tectonically active settings where applied tectonic stresses facilitate development of high fluid pressures within the sediments a variety of mechanisms have been cited as triggers for clastic intrusions these include seismicity induced liquefaction application of tectonic stresses excess pore fluid pressures generated by deposition related processes and the influx of an overpressured fluid from deeper within the basin into a shallow sand body the formation of sandstone dykes and sills is investigated here by considering them as natural hydraulic fractures when the seal on an unconsolidated overpressured sand body fails the resulting steep hydraulic gradient may cause the sand to fluidize the fluidized slurry can then inject along pre existing or new fractures to form clastic intrusions the scale and the geometry of an intrusive complex is governed by the stress state depth and pre existing joints or faults within the sedimentary succession as well as the nature of the host sediments for the simplest tectonic setting where the maximum stress in a basin is vertical gravitational loading small irregular intrusions commonly result in the formation of sills at shallow depths within a few metres of the surface whereas at greater depth dykes and sills forming clastic intrusion networks are more typical a simple relationship is derived to calculate the maximum burial depth at which a dyke sill complex forms as a function of the source bed to sill height the bulk density of the surrounding sediments and the ratio of the vertical to horizontal effective stresses k 0 when applied to three examples of large scale dyke sill complexes developed within paleocene and eocene deep water reservoir sand bodies of the north sea maximum burial depths in a range of 375 to c 500 m 450 700 m and 550 850 m are estimated for intrusion of each of the three complexes

classification of paleosols despite increased interest in paleosols during the past decade no satisfactory classification is in current use presented here is a largely descriptive classification system that utilizes those pedogenic features that have the highest preservation potential in the rock record emphasized in the classification are morphological and mineralogical features that are easily recognizable in the field and through the petrographic microscope the classification is based on evaluation of the relative prominence in a paleosol of six pedogenic features or processes organic matter content horizonation redox conditions in situ mineral alteration illuviation of insoluble minerals compounds and accumulation of soluble minerals the most prominent of these six features processes provides the key to classifying a paleosol into one of nine orders four of the order names are borrowed from soil taxonomy histosol spodosol oxisol vertisol whereas the other five order names are presented here for the first time calcisol gypsisol gleysol argillisol protosol the orders may be preceded by one or more subordinate modifiers that describe other important features of the paleosol the classification is relatively easy to apply to the rock record and should enhance communication and aid in the standardization of terminology

use of chemical and isotopic tracers to assess nitrate contamination and ground water age woodville karst plain usa concerns regarding ground water contamination in the woodville karst plain have arisen due to a steady increase in nitrate n concentrations 0 25 0 90 mg l during the past 30 years in wakulla springs a large regional discharge point for water 9 6 m3 s from the upper floridan aquifer ufa multiple isotopic and chemical tracers were used with geochemical and lumped parameter models exponential mixing em dispersion and combined exponential piston flow to assess 1 the sources and extent of nitrate contamination of ground water and springs and 2 mean transit times ages of ground water delta 15n no3 values 1 7 13 8 indicated that nitrate in ground water originated from localized sources of inorganic fertilizer and human animal wastes nitrate in spring waters 15n no3 5 3 8 9 originated from both inorganic and organic n sources nitrate n concentrations 1 0 mg l were associated with shallow wells open intervals less than 15 m below land surface elevated nitrate concentrations in deeper wells are consistent with mixtures of water from shallow and deep zones in the ufa as indicated from geochemical mixing models and the distribution of mean transit times 5 90 years estimated using lumped parameter flow models ground water with mean transit times of 10 years or less tended to have higher dissolved organic carbon concentrations lower dissolved solids and lower calcite saturation indices than older waters indicating mixing with nearby surface water that directly recharges the aquifer through sinkholes significantly higher values of ph magnesium dolomite saturation index and phosphate in springs and deep water 45 m relative to a shallow zone 45 m were associated with longer ground water transit times 50 90 years chemical differences with depth in the aquifer result from deep regional flow of water recharged through low permeability sediments clays and clayey sands of the hawthorn formation that overlie the ufa upgradient from the karst plain

oriented clastic dike swarms as indicators of paleoslope an example from the upper cretaceous nanaimo group canada abstract an impressive oriented clastic dike swarm 165 dikes occurs within 3 25 m of strata of a submarine fan turbidite succession of the upper cretaceous nanaimo group british columbia the dikes are remarkably parallel in orientation are consistently subvertical and strike southwest slump fold vergence paleocurrent indicators and other evidence indicate that local paleoslope strike was northwest with a downslope direction to the southwest thus the clastic dikes strike downslope indicating that extension occurred perpendicular to the regional downslope direction not parallel as generally expected two possible models are proposed 1 rapid downslope compression caused by sudden loading perhaps due to slumping events or deposition of thick turbidity current beds this downslope compression caused minor extension perpendicular to the downslope direction resulting in small extensional joints that accommodated clastic injection from buried overpressured sands 2 chaotic sedimentary breccias laterally adjacent to the dike swarm formed as part of a large slumping event which created a local slump channel minor slumping into the main channel from the sides caused extension parallel to the channel margin slope and formation of the clastic dikes parallel to the channel margin but perpendicular to the regional slope oriented clastic dike swarms may represent a new type of paleoslope indicator but they may be created by a number of processes and should therefore be used only in conjunction with supporting evidence

influence of diel biogeochemical cycles on carbonate equilibrium in a karst river abstract variations in temperature photosynthesis and respiration force diel variations in ph and dissolved co 2 concentrations of surface streams possibly controlling carbonate equilibrium between river water and carbonate stream beds diel cycles of water chemistry and 13 c of dissolved inorganic carbon dic were measured to assess how biogeochemical processes affect dissolution and precipitation of calcite and thus channel development in ichetucknee river a large spring fed river discharge 6 m 3 s flowing over carbonate karst terrain in north central florida usa samples were collected at a 4 h sampling interval during two one week periods and at a 1 h interval during a single 24 h period simultaneously temperature ph dissolved oxygen do and no 3 concentrations were measured using in situ sensors at 15 min or 1 h intervals ca 2 dic and no 3 concentrations decreased during the day and increased at night causing diel changes of in stream specific conductivity these changes were inversely related to diel changes in ph pco 2 and do concentrations this work shows that photosynthesis and respiration of subaquatic vegetation are the dominant processes influencing in stream diel variation during the day a simultaneous increase of 13 c dic and decrease in dic indicates that photosynthesis was the primary control on dic concentrations calcite saturation indices ranged from 0 to 0 5 with the highest value in daylight as a result of co 2 consumption causing carbonate precipitation the water remained saturated with respect to calcite at night and 13 c dic values decreased indicating that co 2 production from ecosystem respiration was the dominant process affecting dic concentrations but was insufficient to induce significant carbonate dissolution at night outgassing maintained in stream dic concentrations lower than the supersaturated dic springs source but a drop in 13 c dic indicates that ecosystem respiration had a dominant influence over outgassing although co 2 outgassing occurs it is shown to be a minor component of the dic mass balance while carbonate precipitation represents 88 of dic loss these results indicate that in stream biological processes influence carbonate mineral diagenesis in large clear water rivers

the parasequence definition are transgressive deposits inadequately addressed abstract in only a few decades sequence stratigraphy has become one of the cornerstones of modern stratigraphy although the sequence is the principal stratigraphic unit parasequences are the fundamental composite building blocks by definition parasequences are typically upward shoaling successions that are bounded by flooding surfaces that form in response to relatively rapid rises of relative sea level in that definition little provision is made for significant transgressive deposition during the time of flooding but transgressive deposits do exist in the geological record because these deposits lie above the flooding surface and derive much of their sediment from transgressive erosion of the underlying progradational succession should the parasequence boundary not be moved from the u derlying flooding surface upward to the top of the transgressive unit by doing so the underlying progradational unit and the overlying transgressive unit would constitute one complete regressive transgressive succession nonetheless although appealing the typical inability to easily accurately and consistently identify the uppermost surface of the transgressive unit makes it an untenable surface for stratigraphic purposes as suggested by earlier workers therefore the flooding surface a readily identifiable surface that caps the progradational package and consistently underlies transgressive deposits is the most appropriate surface to bound the parasequence in any event to ignore transgressive deposits is to ignore an important component of the geological record a record that not only provides insight into transgressive depositional processes but also is one that can be economically important as a result transgressive deposits need to be included in the parasequence definition possibly only implicitly but certainly not explicitly excluded furthermore the notion that sequences typically indicate progradational deposition excludes examples where upward fining transgressive deposits related to upward deepening are present and lie below the upward shoaling progradational part of the same parasequence

sequential and climatic framework of the growth and demise of a carbonate platform implications for the peritidal cycles late jurassic north eastern france the middle oxfordian of the eastern paris basin constitutes a remarkable example of the growth and demise of a carbonate platform fischer plots sedimentary and diagenetic features allow the identification of four depositional cycles s5 to s8 in the transversarium zone they are inserted in a lower frequency cycle of increased decreased accommodation space soiii the long term period of accommodation creation occurred during the older s5 and s6 cycles the maximum accommodation zone being located in the lower part of the s6 cycle this high accommodation period was tectonically controlled and was coeval with local distensive activity of a hercynian fault a major minimum accommodation zone exists during the s8 cycle at that time the platform was isolated and presented both a windward and a leeward margin the growth of the platform was favoured by a warm and arid climate oligotrophic conditions and reduced siliciclastic input during a highstand in relative sea level these palaeoenvironmental features favoured the proliferation of phototrophic organisms producing carbonate material the death of the platform was generated by a reduction in the carbonate production surface during a lowstand in relative sea level and by the appearance of mesotrophic conditions induced by the increase in siliciclastic inputs at the beginning of a period with a cooler and more humid climate in the eastern paris basin during the middle oxfordian the parasequences are ordered and present greenhouse characteristics in contrast at the beginning of the s8 cycle the randomness in the thickness of contiguous parasequences increased decreased carbonate production during the lowstand caused by a transition from photozoan to heterozoan benthic communities certainly favoured this randomness and the appearance of catch down parasequences

clastic dike swarms and the structural evolution of the foreland fold and thrust belt of the southern andes clastic dike swarms are intruded into a cenozoic foreland fold and thrust belt in southern chile the dike material consists of sandstone and conglomerate with clasts as much as 25 cm in diameter brecciated wall rocks are also found in the clastic matrix the dikes often exceed 50 cm in width and hundred of metres in length in outcrop and are oriented overwhelmingly transverse to fold axes and parallel to cross joints the dike swarms are concentrated near the toe of major thrusts where they are found injected into the hanging wall a regional axial planar spaced cleavage is developed in the clastic dikes and sills clearly postdating injection of clastic material dike injection postdates at least the initiation of extension fractures the cross joint set within the swarms the dike intrusions represent as much as 20 extension parallel to fold axes in addition to several percent extension represented regionally by the cross joints the structural features of the dike swarms and their geometric relationship to other structures suggest rapid single phase injection the arrival of the front edge of a thrust on an already highly overpressured sedimentary sequence would cause an instantaneous increase in the overburden pressure and therefore could result in injection of a dense slurry of wet coarse sediments along preexisting planes of weakness field relationships of mesoscopic structures suggest the following evolution cross joint development incipient cleavage development initiation of thrusting and buckling clastic dike injection regional spaced cleavage development and associated late stage tightening of folds

soft sediment deformation structures in the mio pliocene misaki formation within alternating deep sea clays and volcanic ashes miura peninsula japan abstract the mio pliocene misaki formation of the miura group miura peninsula japan shows an extremely wide variety of soft sediment deformation structures the most common deformation structures are load casts and associated flame structures dish and pillar structures synsedimentary faults multilobated convolutions chaotic deformation structures sedimentary veins and dykes and large scale slides and slump scars the formation which accumulated in a deep sea environment 2000 3000 m is well exposed in and around jogashima it consists of relative thin commonly dm scale alternations of deep marine fine grained sediments and volcanic ejecta that are as a rule coarse grained since the formation represents fore arc deposits of the izu bonin and the honsu arc collision zone it might be expected that tectonic activity also played a role as a trigger of the soft sediment deformation structures that abound in these sediments this is indicated indeed by the abundance of soft sediment deformations over large lateral distances that occur in numerous beds that are sandwiched between undeformed beds on the basis of their characteristics and the geological context these layers can be explained satisfactorily only by assuming deformation triggered by seismicity which must be related to the izu bonin and honsu arc collision the layers thus form deep marine seismites

discontinuity surfaces on a shallow marine carbonate platform berriasian valanginian france and switzerland discontinuities in sedimentation are commonly expressed as surfaces in outcrop sections and are due to rapid and substantial environmental changes on shallow marine carbonate platforms most such surfaces represent hiatuses below biostratigraphic resolution and detailed analysis is necessary to identify and evaluate the environmental change involved surfaces in nine sections of the lower cretaceous of the french and swiss jura platform are characterized on the basis of eight universally applicable criteria geometry lateral extent morphology biological activity mineralization facies contrast diagenetic contrast and biostratigraphy nine different surface types are distinguished by their common features and environment of formation all of them are related to environmental changes in the form of subaqueous erosion subaerial exposure subaqueous omission or changes in texture and facies the distribution of surface types in the studied sections shows that condensation and exposure related surfaces tend to occur repetitively in certain intervals calibrated by biostratigraphy these surface zones can be correlated across the platform from proximal to distal positions in comparison with the global sequence stratigraphic framework hardenbol et al 1997 most exposure zones correlate with third order sequence boundaries condensation zones fall in between in the studied sections third order eustatic sea level drops appear to be represented rather by zones of small scale discontinuities than by widespread and well marked single sequence boundaries this is explained by the superposition of high frequency low amplitude sea level fluctuations on a larger scale sea level trend under greenhouse conditions the lateral extent of the surface zones varies through time and indicates important changes in platform morphology changes in local subsidence rate indicated by variable thicknesses of the deposits in comparison with second and third order sea level trends suggest an evolution of the french jura platform from a ramp type morphology in the late middle berriasian to a flat topped platform in the late berriasian the early valanginian again is characterized by increased differential subsidence and well marked platform morphology this study demonstrates that 1 small scale and short lived discontinuities can reflect large scale variations of relative sea level 2 on shallow platforms characterized by small topographic variations and lateral facies changes third order sequence stratigraphic surfaces are not necessarily expressed by one widespread single surface but by zones of surfaces indicating repeated environmental changes surface zones can serve as an additional tool for correlation and interpretation of platform evolution and 3 small scale discontinuities form an integral part of the stratigraphic record and should receive the same attention as the sedimentary deposits they delimit

geometry and tectonic significance of albian sedimentary dykes in the sisteron area se france abstract sedimentary dykes in the sisteron area have penetrated pre existing fracture sets in late aptian and early albian strata dynamic characteristics of such fractures are revealed by the bifurcation and the branching of dykes three dimensional statistical analysis of the initial orientation of two vertical conjugate sets of dykes indicates their mechanics of formation as well as the principal compressional stress direction during the development of the sill dyke regime in the sisteron area another set of sandstone dykes present in the area suggests syn sedimentary and extensional faulting tectonic activity before the area became involved in compressional tectonics several significant dyke forms clearly show the sense of shear along fractures filled with sand and enable the stress pattern during dyke formation in the area to be recognized

reply to the discussion by b pratt on depositional setting of the 2 1 ga francevillian macrobiota gabon rapid mud settling in a shallow basin swept by high density sand flows by reynaud et al 2018 sedimentology 65 670 701

stratigraphic completeness of carbonate dominated records from continental interiors versus continental margins stratigraphic thinning occurs via condensation and omission at multiple scales abstract over phanerozoic time scales stratigraphic records from continental interiors or cratons are dramatically thinner and are generally assumed to be relatively incomplete with more numerous and longer duration hiatuses compared to records from more rapidly subsiding continental margins however this assumption need not be true for the shorter time scales i e several 106 years and shorter over which accumulation of the preserved stratigraphic record on the continental interior actually takes place this study compares carbonate dominated sedimentary records from the devonian continental interior iowa and continental margin nevada to evaluate whether the continental interior record is 1 miniaturized i e thinner but equally complete 2 comparable in thickness and quality where the sedimentary record is preserved but certain portions of the record are notably absent i e omitted or truncated or 3 so invariably preserved that equivalent stratigraphic packages cannot be recognized compared to the continental margin record this study finds that fourth to fifth order cycles in iowa are on average approximately half as thick and half as numerous compared to the continental margin of nevada moreover the stratigraphic record on the continental margin of nevada is dominated by cycles that are composed of tidal flat and shallow subtidal lithofacies capped by simple flooding surfaces and exhibit catch up or keep up depositional styles the continental interior record in iowa is dominated by cycles that are composed of subtidal lithofacies capped by a range of bounding surfaces and exhibit catch down or give up depositional styles these findings suggest that the thin record in iowa is largely a result of low sedimentation rates associated with suppressed carbonate production in this epeiric sea setting rather than minimal subsidence rates and an increased potential for subaerial exposure and associated loss of record

influence of trench width on subduction hinge retreat rates in 3 d models of slab rollback subduction of tectonic plates limited in lateral extent and with a free trailing tail i e free subduction is modeled in a three dimensional 3 d geometry the models use a nonlinear viscoplastic rheology for the subducting plate and exhibit a wide range of behaviors depending on such plate characteristics as strength width and thickness we investigate the time evolution of this progressive rollback subduction measure the accompanying return flow in the upper mantle and quantify the plate kinematics due to the 3 d geometry flow is allowed to accompany slab rollback around the lateral edges of the slab the toroidal component as opposed to 2 d geometry where material is forced to flow underneath the slab tip the poloidal component a simple force balance is provided which relates the speed of backward trench migration to the resistive forces of generating flow and weakening the plate our results indicate most of the gravitational energy of the system i e the negative buoyancy of the subducting slab is converted into a toroidal flow 69 a much smaller amount goes into weakening the plate 18 and the remaining amount goes into driving flow parallel to displacement of the slab 13 for the trench widths w we investigate 1500 km a maximum trench retreat rate occurs for trenches 600 km wide which is attributed to the interaction between a plate of finite width and the induced flow which has a lengthscale in the horizontal direction these numerical results quantitatively agree with comparable 3 d laboratory experiments using analogue models with a purely viscous plate material schellart 2004a 2004b including correlations between increasing retreat rate with increasing plate thickness trench width for maximum retreat rate 500 km and estimated amount of slab buoyancy used to drive rollback induced flow 70 several implications for plate tectonics on earth result from these models such as rollback subduction providing a physical mechanism for ephemeral slab graveyards situated above the more viscous lower mantle and endothermic phase transition prior to a flushing event into the lower mantle mantle avalanche

periodicity of mesoscale phanerozoic sedimentary cycles and the role of milankovitch orbital modulation data on more than 200 mesoscale sedimentary cycles indicate that phanerozoic cycle periods are randomly distributed with respect to the four major milankovitch orbital parameters except late mississippian through late pennsylvanian cycles which show positive clustering about the 413 000 yr eccentricity period cycle periods calculated from average thicknesses and accumulation rates are strongly dependent on the former correlation coefficient 0 802 but relatively independent of the latter correlation coefficient 0 360 hence calculated period is largely a function of average cycle thickness and milankovitch range periods will be preferentially calculated for cycles with average thicknesses between 1 m and 20 m regardless of actual causes of cyclicity for individual cyclic sequences arguments for milankovitch control based solely on average period are unfounded comparison of short term holocene sedimentation rates and long term phanerozoic accumulation rates for cyclic peritidal and delta

control of pore fluid pressure on depth of emplacement of magmatic sills an experimental approach article in sedimentary basins the emplacement of magmatic sills tends to occur within rock of low mechanical competence and permeability such as shale this often contains pore fluids at abnormally high pressure we first theoretically show that in anisotropic media the higher the pore fluid pressure the deeper the sill emplacement then we introduce a new technique for analogue modelling of such intrusive bodies under conditions of fluid overpressure greater than hydrostatic which corroborate the theoretical analysis as an analogue of brittle sediment we use a diatomite powder this material is a dry fine grained frictional cohesive and permeable material as an analogue for magma we take a silicone putty rtv silicone which is at first newtonian but then solidifies at room temperature we use compressed air as a pore fluid under these experimental conditions we investigate the intrusion of magma into the host powder under various fluid overpressures in homogeneous diatomite powder having uniform cohesion intrusive bodies are segmented dykes these become feeders to sills if the fluid overpressure exceeds the weight of overburden where the sedimentary column has a horizontal discontinuity in strength the transition from dyke to sill occurs at a smaller overpressure hydrostaticb exb1 as a possible illustration of these results we consider sills within source rocks of the neuquen basin and of the parana basin both in south america where overpressure may have resulted from maturation of organic material

depositional sequences in shallow carbonate dominated sedimentary systems concepts for a high resolution analysis abstract oxfordian and berriasian sections representing shallow water carbonate dominated sedimentary systems have been studied in the swiss and french jura in spain and in normandy they all display a hierarchical stacking of depositional sequences facies evolution and stacking pattern allow to define elementary small scale medium scale and large scale sequences some depositional sequences display well marked sequence boundaries others are limited by transgressive or maximum flooding surfaces the hierarchical organisation of such sequence stratigraphic elements implies that sea level fluctuations were an important factor in their formation and that these fluctuations had different frequencies the superposition of high frequency sea level changes on a long term sea level trend leads to repetition of diagnostic surfaces defining sequence boundary and maximum flooding zones wherein the corresponding high frequency surfaces are well developed chronostratigraphic tie points permit us to estimate the duration of large scale sequences this time control and the observed hierarchical stacking suggest that the high frequency sea level changes were controlled by climatic cycles in the milankovitch frequency band the variability of stacking pattern and facies evolution between sections illustrates the complexity of the studied environments furthermore because of the minimal accommodation space available in these shallow water settings much of the geologic time is not recorded nevertheless detailed analysis of the depositional sequences allows the interpretation of the evolution of the sedimentary system with a high time resolution thus there is a potential to monitor sedimentological ecological and diagenetic processes on a time scale of 20 to 100 ka

the age origin and tectonic significance of mesozoic sediment filled fissures in the mendip hills sw england implications for extension models and jurassic sea level curves in the eastern mendip hills on the northern margin of the wessex basin sw england the carboniferous limestone is cut by numerous fissures that are filled with mesozoic sediments sedimentary dykes neptunian dykes the fissures contain a record of triassic lower jurassic sediments that are only sparingly preserved in their normal stratigraphical position between the carboniferous limestone and the unconformably overlying upper inferior oolite of bajocian age detailed analysis of cross cutting relationships facies analysis biostratigraphy lithostratigraphy and strontium isotope ages of relevant mesozoic sediments has allowed the construction of an upper triassic lower jurassic fissure fill stratigraphy for the eastern mendip area most fissures were clearly formed by rapid influx of unlithified sediment from the land surface or sea floor some smaller cavities or larger cavities with restricted access to the unconformity were apparently filled by sediment that trickled down into the fissure system the vast majority of the mendip fissures are interpreted as having formed as a response of the carboniferous limestone north of major basin bounding faults to pulses of tectonic extension during ladinian norian rhaetian late hettangian early sinemurian late sinemurian early pliensbachian late pliensbachian and bajocian times triassic earliest jurassic fissures have a broad spread of strike from e w to nw se to n s accommodating extension in a roughly ne sw direction younger jurassic fissures show well defined e w and n s trends with the former becoming dominant through time total extension of 4 7 n s and 0 6 e w was produced by the formation of triassic jurassic fissures within the carboniferous limestone such patterns of extension are thought likely to be characteristic of the subsurface geology in much of southern england and wales major implications of this study are that 1 the presence of seismically unresolvable sediment filled fissures in supposedly rigid fault blocks can lead to a significant underestimate of regional extension based on the restoration of motion on normal faults on seismic reflection profiles and 2 the isolation of pulses of tectonic activity with a temporal resolution of 10 5 10 6 years may provide a means of identifying a tectonic signal in relative sea level curves derived from the jurassic sedimentary record

a mohr circle construction for the opening of a pre existing fracture abstract the opening of a fracture is dependent on the fluid pressure and the local stress regime around the fracture for a fracture to open the fluid pressure must exceed the normal stress acting on the fracture the mohr circle provides a useful tool allowing the visualization of these relationships this construction determines the range of fracture orientations that are able to open as well as determining the opening direction of these fractures this is then used to produce ratios of the magma pressure and the principal stresses for some dykes from the lizard ophiolite u k

the alba field ocean bottom cable seismic survey impact on development alba field in the central north sea uk block 16 26 consists of eocene age high porosity unconsolidated turbidite channel sands sealed by low permeability shales at an average subsea depth of 1900 m the main channel is approximately 9 km long and 1 5 km wide and can be up to 100 m thick figure 1 the channel contains discrete bodies of intrareservoir shales that can cause significant drilling completion and production problems immediately overlying the main alba sand channel several wells have encountered thin discontinuous oil saturated brioc sands

the 2 1 ga old injectite network of the franceville basin gabon architecture origin and implications on manganese mineralization abstract detailed sedimentological investigations on numerous outcrops and drill core sections in the 2 1 ga old franceville basin gabon provide evidence for a large scale injectite network the injectites were formed by the injection of sands through a thickness of about 150 m of the fb1 member and now cover a minimum area of 70 km 2 corresponding to the bangombe plateau but are also recognized close to franceville 35 km farther south east the injectite lithology corresponds to a mud or carbonate supported sandstone characterized by a loose and uncompacted fabric contrasting with the host rock because the injectites are often parallel to subparallel to the stratification they were misinterpreted as depositional beds by previous authors at outcrop the injectite bodies exhibit sill dyke wing and protrusive geometries emplaced during early burial within poorly compacted material with partial wall erosion and dissociation the source of the sand material is attributed to a channel levee turbidite depositional system located in the lower part of the fb1 member these deposits were buried by a thick biochemical muddy cap deposited during a starvation phase which increased the seal capacity of the system this type of architecture has a high potential to develop compaction disequilibrium during burial moreover in the case of the francevillian injectites the abundance of microbial organic matter favoured early methane degassing and lateral charging of the sand reservoir the overpressure in the channels was periodically released during early burial through the effect of rapid sedimentary and tectonic loading and possible seismic activity the fluidized sand was injected according to a symmetrical wing pattern thus the injected masses caused a local decrease in the grade of the lateritic manganese ore deposit of the bangombe plateau

estimating palaeo water depth from the physical rock record abstract palaeo water depth and its change with time is a key factor in environmental analysis and in sedimentology in general the literature published on this topic and on related subjects however is substantial albeit scattered within and between different communities geologists oceanographers engineers physicists etc here i focus on proxies for palaeo bathymetry as obtained from the physical rock record floral faunal and chemical evidence for palaeo water depth being equally important must be dealt with elsewhere an assessment of the main depth related parameters in actualistic settings is presented and their applicability to the fossil sedimentary record discussed the outcome reveals the full complexity of this topic there is for example no such thing as an average wave base depth applicable to a wide range of fossil case settings this because wave and current climates in general and particularly so in neritic and coastal settings are intriguingly complex furthermore observations from modern oceans are not a priori applicable to fossil ones acknowledging these problems and limitations critically evaluated quantitative proposals for depth indicative facies and features in the sedimentary record are presented and error bars discussed

effects of terrigenic he components on tritium helium dating a case study of shallow groundwater in the saijo basin abstract dating using a combination of 3h and 3he is believed to be the most practical method for estimating the short residence time of shallow groundwater however this method must estimate tritiogenic 3he alone and tends to overestimate the residence time of groundwater if terrigenic 3he from the mantle cannot be excluded from the total dissolved 3he we demonstrate the exclusion of terrigenic 3he in the saijo basin where mantle he is easily released along the major active fault median tectonic line the 3he 4he ratios suggest that the west bank of the kamo river which lies within the basin has experienced greater emanations of mantle he than the east bank we estimate the residence times to be 1 1 96 years by the proposed exclusion method

discontinuities in carbonate successions identification interpretation and classification of some italian examples abstract the growing use of unconformities as bounding surfaces for new types of stratigraphic units seems not to be matched by a corresponding effort on process oriented researches on unconformities themselves this paper aims at giving a contribution to classification and understanding of discontinuities in carbonate successions from the outcrop perspective based on some italian examples a number of integrated criteria geometry sedimentology diagenesis biostratigraphy is proposed to recognise stratigraphic breaks old terms are discussed and sometimes redefined while some new terms are introduced the term discontinuity surface ds is proposed as a general one to indicate any stratigraphic interface where an interruption of sedimentation can be proved a ds can be characterized as a firm ground or a rock ground depending on its coherence at the moment of the renewal of sedimentation polygenic and simple omission surfaces are separated within firm grounds if a recognizable gap is either present or not a third kind of firm ground revealed only by biostratigraphy has been called hidden discontinuity surface two categories of rock grounds are also distinguished hard grounds and inherited rock grounds if respectively generation of the ds and or deposition of the overlying sediments took place in the same environment of the underlying sediments or not a genetic interpretation for each type of discontinuity is proposed the largest variety of ds s occurs in pelagic sediments some discontinuities hard grounds and simple omission surfaces are attributed to increased bottom current activity during sea level falls others polygenic omission surfaces and hidden ds s are interpreted as submarine slide scars either with or without the overprint due to exposure on the seafloor the ds s separating different facies e g platform and pelagic ones are interpreted to be due to tectonics the relevance of the recognized ds s to sequence stratigraphy is briefly discussed

constraining the depth and timing of large scale conical sandstone intrusions kilometer scale sandstone intrusions a recently recognized end member of the spectrum of soft sediment deformation structures are important components of many deep water sandstone reservoirs they result from the remobilization of considerable volumes of sand during early stages of burial this paper uses three dimensional seismic data calibrated to nearby wells to describe an extensive system of large downward tapering conical sandstone intrusions from the faeroe shetland basin on the uk atlantic margin the intrusions are derived from a middle eocene submarine fan and are injected vertically upward through overlying highly faulted claystones to form conical bodies that interconnect across the 700 m thick claystone interval to feed a set of shallow intrusions located within a few hundred meters of the paleoseabed the forcible intrusion of these shallow sandstone bodies produced complementary folding of the contemporaneous seabed the subsequent onlap of these seabed domal folds took place immediately after the intrusion event and by correlation to biostratigraphic data from nearby wells we date these intrusions as late miocene this is the first time that both the age and emplacement depth range of a system of large scale sandstone intrusions have been constrained

large scale conical sandstone intrusions and polygonal fault systems in tranche 6 faroe shetland basin abstract kilometre scale sandstone intrusions are important components of many deep water clastic systems they result from the remobilisation and injection of sand during early stages of burial and are commonly found in fine grained mudrocks containing a pervasive polygonal fault network this paper uses three dimensional seismic data from the faroe shetland basin on the uk atlantic margin calibrated to nearby wells to examine the relationship between an extensive system of large downward tapering conical sandstone intrusions to the pervasive polygonal fault network present within the surrounding encasing host mudstones the intrusions were injected upwards during the late miocene through eocene oligocene claystones with a pre existing polygonal fault network to form conical bodies up to 300 m high within the 700 m thick claystone sequence this study shows that polygonal faults and the discordant limbs of conical sandstone intrusions form two distinct dip populations with little overlap that have average dips of 58 and 26 respectively polygonal faults display decreasing dip with increasing depth however conical sandstone intrusion dip is uniform throughout the eocene oligocene succession these observations lead us to conclude that the geometry of conical sandstone intrusions is not greatly affected by the presence of a pre existing polygonal fault network nor is it affected by increased overburden pressure with depth therefore the 10 50 dip range displayed by the limbs of conical sandstone intrusions observed within the study area is a fundamental property of conical sandstone intrusions the presence of a widespread region of conical sandstone intrusions in the faroe shetland basin has important implications for vertical fluid migration in the region the eocene oligocene claystones in the region have very low permeability but the presence of large scale conical sandstone intrusions and any possible feeder systems is likely to provide high permeability fluid conduits through this sequence in effect the otherwise good regional caprock provided by the eocene oligocene claystone sequence is breached by a network of sandstone intrusions possibly resulting in reduced hydrocarbon trapping potential beneath the seal

infiltration mechanisms related to agricultural waste transport through the soil mantle to karst aquifers of southern indiana usa abstract a hydrogeological study was conducted during the 1991 1992 water year in the clay soil mantled portion of a limestone terrain in southern indiana the purpose of the study was to investigate the modes of soil water infiltration contributing to rapid transport of nitrate to the saturated zone the 1 year cycle profiles of nitrate concentration vs time show a consistent increase of nitrate at various depths in the unsaturated zone during the period of investigation the increase of nitrate in soil water is attributed to the rapid flushing of the inorganic fertilizers from the fields after the area received sufficient rainfall in late fall the investigation also showed a major movement of nitrate in quick pulses through the unsaturated zone rather than a slow uniform recharge immediately after a major storm event the asymmetric profiles of nitrate concentration vs depth point to the existence of preferential flow through macropores in the clay soil mantle above the bedrock soil water transport between storm events is by matrix type flow nitrogen isotopes were analyzed for representative groundwater samples collected before and immediately after fertilization of fields in the summer 1991 the 615n values of the samples did not show any major shift in nitrate sources between the sampling periods the summer of 1991 was extremely dry prohibiting vertical transport of nitrate from the fields to the groundwater system any change in nitrate concentration in groundwater during this time is attributed to the mixing through lateral flow within the aquifer

three orders of regional sea level changes control facies and stacking patterns of shallow platform carbonates in the maestrat basin tithonian berriasian ne spain middle tithonian berriasian shallow platform carbonates of the maestrat basin salzedella and montanejos sections ne spain are stacked in sequence stratigraphic units of different orders higher order sequences parasequences and subunits have a shallowing or deepening shallowing evolution they have been related to the short term eccentricity and precession cycles major facies changes and stacking pattern of parasequences reveal the presence of two 2nd order sequences the lower sequence is middle tithonian mid early berriasian in age the upper sequence extends up to the mid late berriasian it is suggested that local subsidence changes along with regional sea level changes controlled the long term evolution of accommodation in the maestrat basin facies evolution stacking pattern and sharp lithological changes have allowed the definition of five 3rd order sequences in the lower sequence in montanejos the transgressive deposits are characterised by the progressive absence of the restricted lagoon facies and the presence of deepening upward intervals in the parasequences the highstand deposits display an increase in siliciclastics and a progressive predominance of restricted lagoon facies some of the 3rd order sequence boundaries match the sequence boundaries identified in other european basins and may be related to sea level falls induced by the long term eccentricity cycle enhanced during periods of long term loss of accommodation

paleosols in shallow marine carbonate sequences abstract shallow water carbonate sequences in the geological record commonly exhibit numerous exposure surfaces reflecting emersion of sediment due to progradation processes and sealevel oscillations some ancient platform sequences contain hundreds of such surfaces associated with paleosols fossil soils typically calcretes a wide range of macro and microstructures are associated with these calcretes which are reviewed profile types and stages in profile development can be defined the nature of the exposure surface and associated paleosols can be used to identify the nature of the prevailing climate although hydromorphic effects related to marine flooding of the platforms can modify the paleosols a potentially important use of paleosols is to define the nature of sequence boundaries several studies have identified sets of paleosols with varying maturities reflecting changes in rates of accommodation space creation during sealevel rises and falls

topography and significance of a basinwide sequence bounding erosion surface in the cretaceous cardium formation alberta canada abstract the cardium formation turonian coniacian upper cretaceous of the western interior seaway alberta contains six marine sandier upward successions bounded by seven basin wide erosion surfaces in the subsurface erosion surface e5 is associated with major oil and gas fields and is penetrated by thousands of wells a topographic map of e5 based on 6126 well logs and over 1100 measured cores shows a series of subparallel elongate highs steps and lows which trend northwest southeast parallel to tectonic trends and to the actively rising cordillera to the southwest the steps are about 10 km apart and the relative relief step to adjacent low is up to 25 m the steps are asymmetrical with a steeper face to the northeast the e5 erosion surface cuts into offshore marine hummock cross stratified sandstones and interbedded mudstones and it records a lowering of relative sea level our interpretation suggests that erosion was in neither a fully subaqueous nor a fully subaerial environment instead it involved relative sea level lowering and subaerial erosion followed by major modification of the landscape during transgressive shoreface erosion at times of relative stillstand during overall transgression gravel was supplied to the shoreface and was reworked a short distance alongshore by waves these conglomerates now form important oil and gas reservoirs the asymmetry of the steps and lows indicates that the originally flat sea floor was tilted northeastward immediately before erosion giving a gradient of about 1 1000 during transgression shorefaces were incised into the tilted surface to form a stepped morphology also during transgression the sea floor was gradually restored to its pre tilting position each of the six marine sandier upward sequences along with the erosion surface at the top occupies an average of 470 000 years and we estimate that transgression took at least 100 000 to 200 000 years

characterization lateral variability and lateral extent of discontinuity surfaces on a carbonate platform barremian to lower aptian oman hiati of various duration in carbonates are commonly expressed as discontinuity surfaces the understanding of processes that form and affect these surfaces leads to an improved sequence stratigraphic interpretation a reliable outcrop correlation and better models for reservoir compartmentalization various intraformational discontinuities were analysed and interpreted in a well exposed study window 2 5 km in lateral length and 60 m in height comprising the barremian aptian qishn formation haushi huqf area central oman this study focuses on the lateral extent and morphology of the surfaces the petrography of the underlying rocks and the facies changes and geochemical trends across these discontinuities furthermore the lateral variability of discontinuity surfaces was documented three genetic types of discontinuities are differentiated i erosion surfaces ii omission surfaces hard and firmgrounds and iii composite surfaces with evidence for both subaerial exposure and submarine boring field observations combined with petrographic and geochemical data suggest that 17 surfaces are laterally extensive for at least 20 km and record relative sea level fluctuations of regional scale in contrast a large number of laterally limited surfaces 1 km are related to locally active processes such as waves and current erosion the lateral variability along extensive surfaces is the result of the depositional environment below the discontinuity the sea floor topography waves and currents and differential erosion the most pronounced lateral variability is present along six laterally extensive composite surfaces that record terrestrial exposure and subsequent flooding of a tidal flat environment this variability is caused by spatial variability in the tidal flat environment meteoric alteration and differential erosion this study emphasizes the spatial and temporal complexity of processes that form and modify discontinuity surfaces this variability must be kept in mind when interpretations and correlations are based on one dimensional sections or cores 2005 international association of sedimentologists

eocene sandstone intrusions in the tampen spur area norwegian north sea quad 34 imaged by 3d seismic data the eocene of the northern north sea is characterised by fine grained mudstones and isolated sandbodies three dimensional 3d seismic data reveal that the eocene mudstones are intensely deformed by polygonal faulting and contain numerous discordant amplitude anomalies the anomalies identified in the tampen spur area are similar to discordant anomalies previously described from the eocene in the south viking graben and the outer moray firth detailed mapping shows that the anomalies are often conical in three dimensions with dimensions ranging from 100 to 200 m height and a few hundred metres to a few kilometres lateral extent well calibrations show that the anomalies arise from sandstones tens of metres thick encased in mudstone the discordant amplitude anomalies are interpreted as large scale conical sandstone intrusions fed from deeper paleocene sandbodies individual conical intrusions may contain millions of cubic metres of sandstone and may provide fluid migration paths potential reservoirs and pose a drilling risk when exploring for deeper targets

use of liquefaction induced features for paleoseismic analysis an overview of how seismic liquefaction features can be distinguished from other features and how their regional distribution and properties of source sediment can be used to infer the location and strength of holocene paleo earthquakes abstract liquefaction features can be used in many field settings to estimate the recurrence interval and magnitude of strong earthquakes through much of the holocene these features include dikes craters vented sand sills and laterally spreading landslides the relatively high seismic shaking level required for their formation makes them particularly valuable as records of strong paleo earthquakes this state of the art summary for using liquefaction induced features for paleoseismic interpretation and analysis takes into account both geological and geotechnical engineering perspectives the driving mechanism for formation of the features is primarily the increased pore water pressure associated with liquefaction of sand rich sediment the role of this mechanism is often supplemented greatly by the direct action of seismic shaking at the ground surface which strains and breaks the clay rich cap that lies immediately above the sediment that liquefied discussed in the text are the processes involved in formation of the features as well as their morphology and characteristics in field settings whether liquefaction occurs is controlled mainly by sediment grain size sediment packing depth to the water table and strength and duration of seismic shaking formation of recognizable features in the field generally requires a low permeability cap above the sediment that liquefied field manifestations are controlled largely by the severity of liquefaction and the thickness and properties of the low permeability cap criteria are presented for determining whether observed sediment deformation in the field originated by seismically induced liquefaction these criteria have been developed mainly by observing historic effects of liquefaction in varied field settings the most important criterion is that a seismic liquefaction origin requires widespread regional development of features around a core area where the effects are most severe in addition the features must have a morphology that is consistent with a very sudden application of a large hydraulic force this article discusses case studies in widely separated and different geological settings coastal south carolina the new madrid seismic zone the wabash valley seismic zone and coastal washington state these studies encompass most of the range of settings and the types of liquefaction induced features likely to be encountered anywhere the case studies describe the observed features and the logic for assigning a seismic liquefaction origin to them also discussed are some types of sediment deformations that can be misinterpreted as having a seismic origin two independent methods for estimating prehistoric magnitude are discussed briefly one method is based on determination of the maximum distance from the epicenter over which liquefaction induced effects have formed the other method is based on use of geotechnical engineering techniques at sites of marginal liquefaction in order to bracket the peak accelerations as a function of epicentral distance these accelerations can then be compared with predictions from seismological models

facies architecture of a late jurassic carbonate ramp the korallenoolith of the lower saxony basin the sedimentary succession of a late jurassic oxfordian to basal kimmeridgian carbonate ramp is described and interpreted the study area is located in the central part of the lower saxony basin in nw germany which forms part of the central european basin eight well exposed and undeformed sections of the study area suntel area wesergebirge and eastern part of the wiehengebirge provide detailed information about lithofacies and lateral thickness variations biostratigraphically the age of these sediments is poorly constrained twenty microfacies types are recognized that can be grouped into seven facies associations a strongly bioturbated marlstones deposited near storm wave base swb b foraminifera rich wackestones c wackestones and floatstones with biostromes and d bioclastic limestones deposited between swb and fair weather wave base fwwb e oolitic and iron oolitic limestones and f siliciclastic sediments deposited above fwwb and g lagoonal deposits these facies associations characterize a storm dominated shallow mixed carbonate siliciclastic ramp based on facies changes quartz content and gamma ray logs the korallenoolith formation can be subdivided into a lower carbonate dominated and an upper siliciclastic dominated part build up by different scales of small to large scale deepening and shallowing upward cycles a preliminary correlation of measured outcrops of this formation is presented

intercomparison of tritium and noble gases analyses 3h 3he ages and derived parameters excess air and recharge temperature abstract groundwater age dating with the tritium helium 3 h 3 he method has become a powerful tool for hydrogeologists the uncertainty of the apparent 3 h 3 he age depends on the analytical precision of the 3 h measurement and the uncertainty of the tritiogenic 3 he component the goal of this study as part of the groundwater age dating interlaboratory comparison exercise was to quantify the analytical uncertainty of the 3 h and noble gas measurements and to assess whether they meet the requirements for 3 h 3 he dating and noble gas paleotemperature reconstruction samples for the groundwater dating intercomparison exercise were collected on 1 february 2012 from three previously studied wells in the paris basin france fourteen laboratories participated in the intercomparison for tritium analyses and ten laboratories participated in the noble gas intercomparison not all laboratories analyzed samples from every borehole the reproducibility of the tritium measurements was 13 5 the reproducibility of the 3 he 4 he ratio and 4 he ne ar kr and xe concentrations was 1 4 1 8 1 5 2 2 2 9 and 2 4 respectively the uncertainty of the tritium and noble gas measurements results in a typical 3 h 3 he age precision of better than 2 5 years in this case however the measurement uncertainties for the noble gas concentrations are insufficient to distinguish the appropriate excess air model if the measured helium concentration is not included while the analytical uncertainty introduces an unavoidable source of uncertainty in the 3 h 3 he apparent age estimate other sources of uncertainty are often much greater and less well defined than the analytical uncertainty

sand injectites from source to emplacement an example from the miocene age frimmersdorf seam garzweiler open cast mine lower rhine embayment

river reversals into karst springs a model for cave enlargement in eogenetic karst aquifers most conceptual models of epigenic conduit development assume that conduits sourcing karst springs form as water that is undersaturated with respect to carbonate minerals flows from recharge to discharge points this process is not possible in springs fed by distributed recharge that is transmitted through aquifer matrix porosity such as unconfined aquifers in eogenetic carbonate rocks diffusely recharged water has a long residence time within the aquifer and thus would have equilibrated with the aquifer rocks prior to discharge to the conduits the upper floridan aquifer has high matrix permeability 10 13 m 2 and many springs lack discrete inputs of undersaturated allogenic water in their recharge areas consequently another explanation for their development is necessary during flooding of the suwannee river in north central florida water highly undersaturated with respect to carbonate minerals commonly recharges the upper floridan aquifer through spring vents and solution scallops oriented away from the vents suggest most dissolution along conduit walls occurs during these flow reversals during a single flow reversal at the peacock spring cave system flood water was capable of dissolving up to 3 4 mm of the conduit wall rock dissolution occurs as flow reversals follow preexisting features that include joints and paleo water table caves lack of speleothems in conduits in the upper floridan aquifer has been used as evidence that the caves formed in the phreatic zone however flooding would dissolve any speleothems that may have formed during previous subaerial exposure conduit enlargement during flow reversals suggests that dissolution can progress in the normal upstream directions and this process may be an important driver of dissolution in any karst aquifer with outflows to surface water that are subject to flooding flow reversals would also introduce dissolved organic carbon and oxygen into the groundwater and provide important energy sources for cave ecosystems as well as altering redox chemistry of the aquifer water

hierarchy of high frequency orbital cycles in cretaceous carbonate platform strata abstract lower cretaceous valanginian hauterivian carbonate platform strata which are well exposed in the matese mountains of the southern apennines italy have been analyzed on a microstratigraphic cm scale to exemplify the high frequency cyclic nature of the mesozoic shallow water sedimentation in southern italy based on the vertical organization of lithofacies and their early diagenetic signature 46 metre scale cycles are recognized these elementary cycles are hierarchically organized into groups bundles and superbundles the elementary cycles are prevalently formed by subtidal deposits and show emersion related features at the top suggesting repeated sea level fluctuations the number of elementary cycles compared to time as constrained by biostratigraphy and their grouping into sets implying higher order complexity in the environmental oscillation suggest an orbital control on sedimentation spectral analysis of recurrent thickness in stratal features defines and quantifies the cyclicity which is characterized by lithofacies thickness periodicities of 1271 391 159 124 and 69 cm linear correlation of the relative ratio set rrs of these periodicities with the corresponding rrs of the orbital perturbation periodicities shows that 1271 and 391 cm fit the 404 220 and 94 890 year cycles of early cretaceous orbital eccentricity 159 and 124 cm fit the 49 010 and 38 030 year cycles of the earth s axial obliquity whereas 69 cm corresponds to the precession periodicity thus the san lorenzello section required not less than 1 6 ma to form at an average rate of 26 mm ka each 400 ka cycle can be viewed as a depositional sequence in which sequence boundaries maximum flooding surfaces and system tract equivalents have been recognized the microstratigraphic approach is very promising for understanding the fine structure of climate related environmental fluctuation recorded by the 3000 m thick carbonate platform successions of the southern apennines over a time span of about 150 ma upper triassic upper cretaceous and for deriving a more precise chronostratigraphy for global correlation

punctuated aggradational cycles a general hypothesis of episodic stratigraphic accumulation according to the hypothesis of punctuated aggradational cycles presented here the stratigraphic record consists of small scale 1 5 m thick shallowing upward cycles pacs separated by surfaces marked by abrupt change to deeper facies this motif pervasive in time and environment is produced by relatively long periods tens of thousands of years of base level stability punctuated by geologically instantaneous relative base level rises of at least basin wide extent as basin wide lithologic time stratigraphic units pacs are fundamental to all aspects of stratigraphic analysis including correlation paleoenvironmental interpretation and paleogeographic reconstruction of several possible allogenic mechanisms for a pervasively cyclic stratigraphic record glacial eustasy driven by orbital perturbations is preferred the pac hypothesis is presented as a comprehensive model to be tested and modified by examination of the stratigraphic record from an episodic perspective

alpine halite mudstone polyhalite tectonite sedimentology and early diagenesis of evaporites in an ancient rift setting haselgebirge formation eastern alps the permian haselgebirge formation of the eastern alps is among the most highly deformed evaporites worldwide in underground salt mines it is composed of a melange of halite anhydrite and mudstone with a subordinate amount of magmatic rocks the only potassium mineral is polyhalite k2ca2mg so4 4 center dot 2h 2 o its extreme tectonic deformation provides a challenge for reconstructing the tectono sedimentary environment in this context we were able to compile a set of characteristic sedimentary and early diagenetic features of the non halite components in particular mudstone and anhydrite pseudomorphs after gypsum preserve synsedimentary structures while mudstone represents the overall background sedimentation sulfate precipitated mainly at the brine surface under pelagic conditions the large amount of mudstone 50 was probably trapped as mud in a quiet lagoonal basin its magnesium dominated mineral composition is in accordance with coeval halite precipitation from seawater earthquake induced deformation structures formed in the semiductile mud sediment as mostly ramified centimeter scale sedimentary dikes which originated intrastratally by liquefaction permian volcanism is documented by a basaltic body from the hallstatt salt mine which exhibits a sedimentary contact with the mudstone its immobile trace element composition favors an intraplate origin consistent with a rift stage during subsequent burial authigenic minerals such as quartz and feldspar started to grow the origin of polyhalite relates to the mobilization of complex fluids and roughly coincides with the final late middle triassic opening of the meliata ocean all evidence from syn sedimentary deformation and early diagenesis confirms the deposition of the evaporites in a late thinning stage of an ancient rift