the limitations of cement stratigraphy as revealed in some lower carboniferous oolites from south wales abstract the use of staining and cathodoluminescence to correlate carbonate cements is often coupled with the conception of diagenetic environments that are uniform through a large volume of rock at any instant in time thus it is often assumed that individual growth zones within carbonate cements are present throughout a unit and have a chronological significance detailed study of meteoric phreatic cements in the oolite group lower carboniferous south wales indicates that individual growth zones can only be traced with any certainty between adjacent pores and are often only identifiable in a few square millimetres of thin section additionally cement sequences with apparently identical cathodoluminescence appearance are often demonstrably of different ages the complex variation in cements through the oolite group partly reflects the extremely localised controls on groundwater chemistry in the shallow subsurface it is also due to the superimposition of a number of phases of subaerial exposure at successively higher levels during deposition of the group the chemistry of a calcite cement reflects the geochemical environment at the time of precipitation at that location in the diagenetic system it is likely that that environment has been frequently repeated both in space and time

postscript summary of the coventry groundwater investigation and implications for the future abstract the broader implications of the coventry groundwater investigation are discussed in this postscript the complex interbedded sandstone and mudstone sequence under coventry is seriously polluted by chlorinated hydrocarbon solvents investigations in such terrain will require much greater expenditure than was available for this project if they are to describe the distribution and movement of pollutants in enough detail to evaluate quantitatively options for aquifer clean up it is not realistic to consider clean up of coventry s groundwater at the present time because of the lack of detailed knowledge it is probable at least for the present that clean up is not feasible because of hydrogeological constraints arising from the extreme variability of permeability in the system and an absence of operational techniques for clean up stronger more pro active protection of groundwater is needed a major recommendation for future investigations is a procedure to avoid open boreholes which can allow pollution to penetrate deeper into the aquifer and may confuse the results of sampling

the application of cathodoluminescence to interpreting the diagenesis of an ancient calcrete profile a laterally extensive calcrete profile has been identified in the late asbian lower carboniferous shallow marine shelf limestones of the llangollen area north wales the upper surface of the profile is defined by a laterally discontinuous palaeokarstic surface and by laminated calcareous crusts which developed within the underlying limestone the profile contains a unique series of early pore filling vadose cements which only occur down to 1 m below the palaeokarstic surface cathodoluminescence reveals that these cements pre date the late pore filling meteoric phreatic cements which occur throughout local asbian lithologies a spar cement stratigraphy has been established for the calcrete profile subaerial vadose cements comprise two generations of non luminescent cement followed by a brightly luminescent generation which occasionally shows an acicular habit this needle fibre calcite represents the final stage of vadose cementation precipitation of vadose cements was contemporary with subaerial alteration and micritization of the limestone textures visible only with cathodoluminescence provide evidence of recurrent periods of fabric dissolution the most extensive phase of dissolution occurred immediately after the precipitation of the non luminescent subaerial vadose cements several different textures have been recorded each reflecting the morphology of a partially dissolved substrate dissolution textures are generally confined to the walls of the larger pores and to early brecciation fractures these probably acted as fluid pathways in the calcrete during early subaerial diagenesis much of the non marine micrite in the calcrete profile appears as needle fibre calcite under cathodoluminescence this acicular calcite was probably formed in response to localized supersaturation of meteoric pore fluids caused by periods of near surface evaporation since needle fibre luminescence is strongly variable these ambient conditions are not believed to have directly controlled the activator ion concentrations of cementing pore waters needle fibre calcite is considered to be a cement precipitate which has almost completely recrystallized to micrite probably during the late stages of subaerial diagenesis two generations of subaerial micrite which define a micrite stratigraphy have been distinguished under cathodoluminescence reconstructing the diagenetic history of this ancient calcrete profile has revealed that subaerial alteration was multistaged with many diagenetic processes acting simultaneously during a single phase of emergence

near surface k feldspar precipitation in cretaceous sandstones from the potiguar basin northeastern brazil abstract the cretaceous fluvial sandstones of the acu formation potiguar basin northeastern brazil contain abundant very early authigenic k feldspar overgrowths around detrital orthoclase and microcline grains detailed optical and cathodoluminescence petrography scanning electron microscopy and electron microprobe analyses provided information about the conditions and timing of precipitation of these overgrowths as well as of the associated diagenetic phases the overgrowths are optically discontinuous with the detrital grains untwined nonluminescing and were formed clear on grain surfaces under phreatic conditions the overgrowths commonly show a rhombohedral sanidine habit range in thickness from about 0 4 to 1 0 mm are chemically pure kalsi3o8 and constitute up to 6 of the whole rock the extremely early origin of the k feldspar overgrowths is indicated by their coating of mechanically infiltrated smectitic clays authigenic smectite rims booklet and vermicular aggregates of kaolinit

cement stratigraphy in triassic and jurassic limestones of the weserbergland northwestern germany abstract cement stratigraphy of the korallenoolith oxfordian and trochitenkalk upper muschelkalk formations southern lower saxony hills of germany is based on investigation of 232 carbonate samples by cathodoluminescence cl this enables subdivision of cements into four main generations generation 1 consisting of fine columnar equant and syntaxial cements with blotchy cl and or microdolomite inclusions that is interpreted as originally submarine mg calcitic precipitate generation 2 found in jurassic samples only these cements show intrinsic to non luminescent cl with thin bright orange subzones and they are interpreted as meteoric phreatic calcites generation 3 1 characterized by zoned calcites with variable cl colours these cements precipitated under shallow burial conditions in a phreatic environment during an incipient stage of late diagenesis generation 3 2 with relatively uniform orange cl indicative of precipitation in a stable chemical environment this cement generation is interpreted as late diagenetic deep burial calcites generation 3 3 partially strongly zoned and with a characteristically intense cl contrast it has been identified in only 17 of the 82 trochitenkalk samples deformation twins end within this generation indicating a post tectonic genesis for the subsequent younger cement zones the cements were probably precipitated in a near surface environment characterized by reducing or variable eh conditions generation 4 consisting of calcites that show intrinsic cl with bright orange subzones comparable to generation 2 but lacking deformation twins these cements are interpreted as post tectonic late diagenetic products of a meteoric phreatic environment based on detailed cl petrography fifteen diagenetic events three calcite cements three dolomite generations three fissure generations two stages of dedolomitization aragonite dissolution matrix recrystallization and two stages of hmc lmc transformation can be distinguished and timed relative to cement zonation the progressively decreasing 18o values for cement generations 1 to 3 2 likely reflect increasing temperatures caused by burial the low 18c values of cement generation 4 are probably a reflection of a meteoric diagenetic environment a time burial cementation pathway can be modelled combining cl patterns cement isotopic data and the subsidence history of the study area the main features of this model are 1 1 generation 1 cements are submarine precipitates and their age therefore coincides with sedimentation 2 2 cement generation 3 1 of the trochitenkalk commenced precipitation at a depth of about 120 m reached during late triassic time in case this minimum depth is also the formation depth of generation 3 1 in the korallenoolith formation then precipitation of these cements started during late jurassic time 3 3 cement generation 3 2 of both the trochitenkalk and the korallenoolith formation precipitated at assumed depths 1000 m reached during the doggerian and at the time of jurassic cretaceous transition respectively 4 4 cement generation 4 precipitated after the sediments had undergone telogenesis and must thus be younger than the intra senonian sub hercynian tectonic phase and possibly even younger than the paleocene tectonic pulse laramian phase

intermediate range fish detection with a 12 khz sidescan sonar the application of a prototype 12 khz sidescan sonar suitable for horizontal imaging of fish distributions is described the sonar consisted of a 40 element 20 array transmitting a 1600 hz 0 2 s fm sweep with correlation processing of the received echoes observations are reported for two different implementations i a configuration in which the sonar was towed at 35 m in water of depth 60 220 m in the southern strait of georgia british columbia where the primary target was sockeye salmon and ii a bottom mounted deployment in a shallow 10 14 m channel near copenhagen denmark where herring were present in the strait of georgia discrete fish targets were detected with up to 25 db signal to reverberation ratio at ranges from 1 to 7 km in the shallow danish waters herring schools were detected at ranges up to 1 2 km in each case an acoustic propagation analysis identifies the useful detection characteristics in the strait of georgia the signal is confined to a subsurface sound channel re

formation of beach rock at siesta key florida and its influence on barrier island development seaward dipping strata of carbonate cemented shell debris located along the coast of siesta key on the gulf coast of the florida peninsula have long been interpreted to be beachrock equivalent in age to the pleistocene anastasia formation stage 5e of the east coast of florida detailed examination of thin sections along with radiometric dating and isotopic analyses demonstrates clearly that this is a holocene deposit that is not beachrock but was lithified in a meteoric environment whole rock dates dates from shells only and from cement only demonstrate that these beach deposits were in place by at least 1800 yr bp and might have been there as long ago as 4300 yr bp this means that some type of barrier island was in place at that time previous investigations have depicted siesta key as having a maximum age of 3000 yr with these deposits being located about 2 km landward of the beach deposits this suggests that the beach deposits might have been the site of the original position of siesta key these data also indicate that sea level must have been near its present position at the time that these foreshore beach deposits were deposited sometime between 1800 and 4300 yr ago this scenario indicates that sea level along this coastal reach probably reached its present level at least about 2000 yr ago

multibeam volume acoustic backscatter imagery and reverberation measurements in the northeastern gulf of mexico multibeam volume acoustic backscatter imagery and reverberation measurements are derived from data collected in 200 m deep waters in the northeastern gulf of mexico with the toroidal volume search sonar tvss a 68 khz cylindrical sonar operated by the u s navy s coastal system station the tvss s 360 degree vertical imaging plane allows simultaneous identification of multiple volume scattering sources and their discrimination from backscatter at the sea surface or the seafloor this imaging capability is used to construct a three dimensional representation of a pelagic fish school near the bottom scattering layers imaged in the mixed layer and upper thermocline are attributed to assemblages of epipelagic zooplankton the fine scale patchiness of these scatterers is assessed with the two dimensional variance spectra of vertical volume scattering strength images in the upper and middle water column mean volume reverberation levels exhibit a vertical directionality which is attributed to the volume scattering layers boundary echo sidelobe interference and reverberation is shown to be the major limitation in obtaining bioacoustic data with the tvss because net tow and trawl samples were not collected with the acoustic data the analysis presented is based upon comparison to previous biologic surveys in the northeastern gulf of mexico and reference to the bioacoustic literature

micromorphological and geochemical characterization of tertiary freshwater carbonates locally preserved north of the edge of the miocene molasse basin sw germany abstract miocene carbonates intercalated in a deposit of upper freshwater molasse middle miocene exposed in a limestone quarry at heidenheim mergelstetten germany were analysed geochemically and micromorphologically the heavy minerals fine sand and clay minerals confirm the sedimentary interpretation of the formation as a sequence of paleogene soil residues overlain by younger neogene soil horizons developed in sediments of the upper freshwater molasse osm the supposed continental origin of the massive bedded pisolitic limestone and white chalky columnar limestone indicated by terrestrial gastropods is confirmed by analysis of stable carbon and oxygen isotopes the microfacies show the characteristics of terrestrial carbonates pisoids nodules and pedodes nevertheless the occurrence of intraclasts reworking features grey black concretions indications of swampy conditions and carbonate enrichment restricted to the depression area cannot be explained by terrestrial pedogenetic processes cathodoluminescence suggests the meteoric character of the sparitic cements which could be differentiated into three phases of cementation corresponding to conditions during lake regression and subsequent transgression x ray diffraction differential thermal and transmission electron microscope analysis of the ammonium acetate insoluble residue of the carbonates indicate neoformation of palygorskite within the pisolitic limestone si and al for formation of palygorskite were probably supplied by degradation of clay minerals illite under alkaline conditions mg was externally supplied to the system the results suggest formation of the miocene carbonates in a marsh or shallow ephemeral lake environment with repeated superimpositions of pedogenetic processes

a 5 day long range sonar record of an extensive concentration of fish the 2 khz correlation sonar at perranporth was used to produce a continuous 5 day record in may 1967 the record s unusual feature is a strong and extended return from a range of the order of 45 km with apparent extent varying from 5 to 35 km this echo return must be due to fish probably sprats the leading edge of the echo shows a diurnal rather than a tidal variation in range being about 13 km closer at night the patterns suggest that at night the sound is attenuated in propagating through the concentration of fish other features shown in the record include a a storm b phase changes in the interference patterns c the whole dispersion process for some shoals and d some 4 m s tracks

on the occurrence of displacive calcite in lower old red sandstone of carnoustie eastern scotland abstract although some skepticism has been expressed regarding the occurrence of displacive calcite this type of growth occurs in the calcrete profiles in lower old red sandstone of carnoustie eastern scotland the calcretes are restricted both laterally and vertically implying they formed on the tops of bars and other bed forms petrographic evidence that the calcite crystals are displacive in origin includes the following 1 sparry calcite crystals occur between textural components i e micas rock fragments fragments of a quartz grain that have an exploded texture and many of the fragments can be visually fitted back together and 2 cathodoluminescence reveals that the calcite crystals are compositionally zoned implying that the crystals are a cement and definitely are not due to replacement the displacive calcite has variable crystal morphology and is restricted vertically to a maximum depth of i m below the subaerial exposure surface in addition the precipitation of displacive calcite concurrently with subaerial expansion and brecciation of detrital fragments indicates that displacive calcite was generated within the vadose zone in the vadose zone crystallization was promoted by rapid surface evaporation leading to supersaturation the recognition of displacive calcite provides evidence of supersaturated precipitating solutions

hydrothermal diagenesis of paleozoic seamount carbonate components we present geochemical results of paleozoic carbonate components brachiopods biogenic low mg calcite blmc crinoids biogenic high mg calcite bhmc and whole rock admixture of aragonite and calcite wrac from open ocean permo carboniferous seamounts of japan situated in the tropical mid panthalassic ocean the diagenetic history of these and other carbonate allochems was determined by visual optical inspection of their external morphology and luminescence by evaluation of their microstructures and by assessment of their trace element and stable isotope distributions the degree and trends of the diagenetic alteration tests were then reconciled with their concomitant sr isotope values and compared to those of the established seawater sr isotope curve the altered carbonate material from three of the four time slices support the novel concept of diagenesis in the presence of marine hydrothermal fluids leading to less radiogenic sr isotope values in addition sr isotope values of unaltered blmc from three of the four time slices do not concur with the values for the concurrent time of the established seawater 87sr 86sr curve an adjustment of their stratigraphic position is untenable and unsatisfactory in light of their biostratigraphic assignment which suggests that sr isotope diagenesis is much more complex and complicated than is espoused in the literature consequently the concept of less radiogenic sr isotope values in diagenetic marine carbonates has profound implications for the veracity of the established seawater 87sr 86sr profile and curve and it needs to be re evaluated in light of the findings

microbial communities and their primary to early diagenetic mineral phases the record from neoproterozoic microbialites of qarn alam oman

sedimentology three dimensional geobody reconstruction and carbon dioxide origin of pleistocene travertine deposits in the ballik area south west turkey the denizli basin in the west anatolian extensional province in western turkey is well known for its numerous travertine occurrences a combined sedimentological diagenetic and geochemical investigation is executed on the ece and faber travertines of the ballk area the largest travertine site in the denizli basin the first aim of this study is the reconstruction of a three dimensional geo model in combination with a detailed sedimentological description from fabric to lithotype lithofacies and geobody scale with a focus on integrating pore typing the second aim involves the delineation of the co2 origin of ancient travertine precipitating waters peloidal phyto and dendritic lithotypes dominate the studied travertines and honeycomb and bacteriform shapes and encrusted bacterial or fungal filaments related to their fabrics suggest a microbial influence the environment of travertine precipitation evolved from dominantly sub aqueous as represented by the sub horizontal and biostromal reed travertine facies to dominantly sub aerial in a thin water film resulting in the cascade waterfall and biohermal reed travertine facies a general progradation of the travertine mound is indicated by the occurrence of stacked waterfall travertines this results in sigmoidal clinoforms inside a general mound boundary configuration strontium and oxygen carbon isotope signatures of the travertines point to a mixing mechanism of palaeofluids with deeply originated heavy carbon co2 with lighter carbon co2 of shallow origin these deposits can thus be considered as endogenic travertines carbonates of the lycian nappes acted as main parent carbon source rocks the relative contribution of the lighter carbon isotopes is most likely to have originated from organic matter or soil co2 this study provides a unique three dimensional insight into the ballk travertine architecture that potentially can be used as an analogue for subsurface travertine reservoirs worldwide and illustrates the importance of the combined use of c 13 and sr 87 sr 86 signatures in the delineation of the co2 origin of travertine precipitating waters

low magnesian calcite marine cement in middle ordovician hardgrounds from kirkfield ontario abstract middle ordovician trentonian biosparites from the bobcaygeon and verulam formations near lake simcoe ontario exhibit numerous features demonstrating lithification near the sediment water interface these include planar erosion surfaces which truncate shells and intraclasts undercut hummocks on upper surfaces vertical borings which cross cut fossil debris and early cement and a diverse fauna of encrusting organisms which grew attached to lithified surfaces a marine origin for early cement is indicated by the development of hardgrounds within a transgressire regionally onlapping sequence the occurrence of dozens of such units within normal marine sediments and a lack of features recording early oxidation and or partial dissolution during exposure to meteoric water marine cement from four of these units examined in thin section by sem and by cathodoluminescence consists of clear zoned syntaxial overgrowths on echinoderm debris and equant spar on trilobite bryozoan and brachiopod fragments as such this cement 1 is morphologically identical to meteoric phreatic low magnesian calcite cement from calcitized pleistocene sequences 2 is interpreted as having been precipitated as low magnesian calcite 3 is anomalous in habit and inferred composition in comparison with holocene marine cement and 4 demonstrates that generalizations which relate cement morphology and composition to environmental water chemistry in modern diagenetic systems may not be valid when applied to more ancient carbonate sequences

climatic significance of holocene beachrock sites along shorelines of the red sea discussion the geologic record of climate change is currently a very active area of research the results of such studies have the potential to greatly improve our understanding of the different factors that influence climate and consequently may help to guide policy initiatives regarding global warming given the importance of such studies it is imperative that they be scientifically rigorous and thorough friedman 2005 falls short on both counts in this article friedman attempted to use the oxygen isotopic composition of a series of 14c dated beachrock samples to infer past changes in temperature on the basis of increasing 18o values for beachrock with decreasing age he concluded that global temperature has decreased dramatically during much of the holocene the conclusions of the study regarding changing temperature are not supported by the data presented alternative hypotheses not considered in the study are far more likely explanations for the observed isotopic trend than decreasing temperature the principal problems with the article are that 1 critical assumptions are unsupported and there is no discussion of alternative hypotheses 2 there is no description of the petrographic characteristics of the samples 3 no information on methodology is included 4 the existing literature on beachrock much directly relevant to the study is completely ignored and 5 the conclusions are contradicted by a large number of paleoclimate studies for the same period these problems are discussed in detail below friedman makes several important assumptions without adequately justifying them the first assumption is that cements in the beachrock precipitated from unaltered seawater he acknowledges that ground water discharge mixing with river water and evaporation effects particularly significant in the gulf of aqaba friedman 1968 can alter the isotopic composition of local seawater but proceeds to assume for the purpose of the subsequent

beachrock a tool for reconstructing relative sea level in the far field abstract today s understanding of sea level change developed through a combination of process based physical modelling and observational data observational data of sea level change derives from coral reefs in the far field of the former ice sheets where a geographically variable relative sea level signal is expected as a response of the earth to ocean loading given this variability and the limited geographical distribution of coral reefs there is a need to explore other non coral based sea level markers to further understand sea level change and for example to fingerprint melt water here we present beachrock as a coastal deposit suitable for relative sea level rsl observations in the far field beachrock is an intertidal deposit forming in the zone where carbonate saturated meteoric and marine water mix and p co 2 decreases we provide the conceptual framework for beachrock analysis and describe techniques suitable for analysing and dating the deposit the approach is standardised by outlining the sediment characteristics in terms of rsl indicative meaning and indicative range and is tested against published data a study conducted on coasts of the mediterranean sea exemplifies the utility of beachrock for rsl reconstruction it is shown that the precision of the reconstruction is derived from the combined uncertainty of age and tidal amplitude or tidal range the uncertainty can be reduced to half the tidal amplitude when a deposit can be ascribed to the upper or lower intertidal zone beachrock based data benefit from the lack of non quantifiable error terms such as post depositional compaction due to the instantaneous formation and high preservation potential of the deposit this underlines the high precision of beachrock based rsl reconstruction which is a prime requirement for testing and extending coral based records

formation exposure and evolution of a high latitude beachrock in the intertidal zone of the corrubedo complex ria de arousa galicia nw spain abstract the presence of beachrocks is noted on the galician shoreline at 41 n a latitude at which this phenomenon is rarely found the present study focuses on the petrological characterization and sedimentological evolution of a beachrock that was exhumed during an exceptional storm in the winter of 2001 in the intertidal zone of a high energy beach the cemented material comprises medium to coarse mixed siliciclastic carbonate sands unlike tropical beachrocks the cement consists of epitaxial low mg calcite presenting varied morphologies and textures acicular and bladed coatings and pore linings pore fillings of sparitic calcite and meniscus style cements seawater dominantly wave action plus marine and meteoric mixed waters are invoked as the main generative fluids beachrock formation and evolution are approached from a morphodynamic viewpoint considering four progressive stages 1 initial cementation in the intertidal zone 2 exposure and modelling by wave action 3 colonization and hardening and 4 disintegration preservation and burial finally the morphodynamic significance climatic implications and occurrence of this type of cementation along the north and northwest shoreline of spain are discussed

diagenetic model for carbonate rocks in midcontinent pennsylvanian eustatic cyclothems abstract diagenetic patterns in cyclic midcontinent pennsylvanian carbonates are readily explained in terms of a predictive diagenetic model derived logically from the eustatic depositional model for widespread pennsylvanian cyclothems developed by heckel 1977 1980 transgressive shoal water calcarenites are characterized by pervasive overpacking of grains neomorphism of originally aragonite grains ooids green algae molluscs and ferroan calcite and dolomite cement which indicate movement from the marinephreatic environment of deposition and diagenesis into the low oxygen deeper burial connate zone with substantial compaction before any cementation offshore invertebrate calcarenites associated with offshore core shales also are characterized by pervasive overpacking of grains an ferroan carbonate cements which indicate a similar diagenetic history their lack of discernible neomorphism relates to original absence of shallow water aragonite grains ooids green algae and probable removal of thin shelled molluscs by dissolution during long periods of sediment starvation in cool water which also corroded the edges of many calcite grains regressive shoal water calcarenites show a much greater variety of diagenetic features including early marine cement rims and large scale leaching of originally aragonite grains often with subsequent collapse of micrite envelopes grain fragments and overlying material in samples insufficiently stabilized by early cement rims this was followed by pervasive cementation by blocky calcite before much further compaction then by ferroan calcite and finally ferroan dolomite in remaining voids this pattern indicates replacement of depositional marine phreatic water by meteoric water which dissolved unstable carbonate grains and then deposited stable carbonate cements in environments that eventually became increasingly oxygen depleted and otherwise chemically changed probably as mixing zone and deeper connate water moved back into the rock and replaced the meteoric water during and after the succeeding transgression trends in calcilutites are essentially similar to those in calcarenites of equivalent phase of deposition with evidence of subaerial exposure and meteoric vadose soil formation in strata at the top of many regressive limestones it is apparent that with the regression of the sea and emergence that terminated deposition of a cyclothem meteoric water penetrated the permeable pans of the regressive carbonate and left its distinctive diagenetic patterns of early leaching and cementation before much compaction took place but rarely did meteoric water penetrate the impermeable offshore shale which acted as a seal this allowed associated offshore and underlying transgressive carbonates to become more deeply buried and substantially compacted before cementation took place with unstable grains undergoing slow neomorphism in the absence of meteoric leaching

fish population and behavior revealed by instantaneous continental shelf scale imaging until now continental shelf environments have been monitored with highly localized line transect methods from slow moving research vessels these methods significantly undersample fish populations in time and space leaving an incomplete and ambiguous record of abundance and behavior we show that fish populations in continental shelf environments can be instantaneously imaged over thousands of square kilometers and continuously monitored by a remote sensing technique in which the ocean acts as an acoustic waveguide the technique has revealed the instantaneous horizontal structural characteristics and volatile short term behavior of very large fish shoals containing tens of millions of fish and stretching for many kilometers

cathodoluminescence of carbonate cemented holocene beachrock from the togo coastline west africa an approach to early diagenesis carbonate cemented holocene beachrock outcrops sporadically along more than 100 km of the togo and benin coasts the sands are siliciclastic with subsidiary carbonate skeletal fragments and intraclasts 14c radiometric dating indicates the sand deposits have formed within the last 5000 years beachrock has been indurated in phreatic environments undergoing afterwards several stages of burial and subaerial exposure cathodoluminescence cl proved a useful tool in unravelling the intricate cementation of this beachrock which can be subdivided into three stages firstly magnesian calcite was precipitated in a marine phreatic active zone very dull orange and very dull blue colours emitted in isopachous rims of needle like crystals and peloidal micrite cl1 fabric reveal different eh and ph precipitating conditions in this environment secondly bright yellow orange luminescing acicular and equant spar cement cl2 fabric is interpreted to have formed in a mixed water phreatic zone the third stage of cementation occurred dominantly in the landward part of the beachrock and accompanied neomorphism of the earlier marine cements the resultant cl3 fabric dull blue medium orange luminescing equant spar is typical of continental fresh water phreatic zones the progression from marine to fresh water pore fillings accompanied sand bar progradation during a stable sea level stage ultimately there was erosion stage of the sand bar deposits which led to subaerial exposure and partial erosion of the beachrock recognition of the effects of repeated shoreline progradation during the early diagenesis of this holocene beachrock indicates the potential value of diagenetic studies in aiding recognition of marine regressions and transgressions in the geological record

assessing the impact of groundwater abstractions on river flows abstract groundwater abstractions affect the water balance in catchments of rivers in hydraulic continuity with groundwater and may lead to reductions in river baseflow the environment agency issues licences for groundwater abstractions and takes into account the risk of such adverse impacts when deciding whether to grant licences and what conditions to associate with each licence assessing the impact of a particular licence is a difficult task but analytical solutions to idealizations of the complex river aquifer interaction can help guide such judgements this paper presents a brief review of available analytical solutions and discusses their applicability to real groundwater systems the most useful analytical solutions developed by theis hantush and stang have been incorporated into a spreadsheet and a new methodology has been made available to support environment agency hydrogeologists working in abstraction licensing this offers a consistent approach to making an initial evaluation of the impact of groundwater abstraction on river flow that may be applied across the diverse hydrogeological systems found throughout the environment agency regions of england and wales the use of analytical solutions in this methodology inevitably represents a significant simplification of what is generally a very complex issue and the limitations of the new methodology are emphasized

marine vadose beachrock cementation by cryptocrystalline magnesian calcite maui hawaii abstract active precipitation of high magnesian cryptocrystalline calcite cement 15 5 mole mgco3 in the intertidal zone on the north shore of maui hawaii results in formation of an extensive beachrock exposure at hookipa park framework grains in the beachrock are coarse algal molluscan and intraclast bearing sands meniscus fabric is dominant in the cement indicating that most lithification occurs in the vadose zone the cryptocrystalline cement is generally brownish gold in color but very thin clear isopachous fringes of microcrystalline calcite surround darker cryptocrystalline cement especially in upper horizons of the beachrock peloidal texture is scarce in the cement but is present in a few samples silt and fine sand sized skeletal fragments have been trapped in he evolving cement resulting in cement supported fabric hollow rims of microcrystalline calcite occupy some pore spaces these hollow rims may have precipitated at the air water interface of bubbles that formed in pores and they may therefore be additional evidence of cementation in the vadose zone interstitial water samples from wells that penetrate portions of the beachrock and unconsolidated beach sands reveal temporal chemical variations that suggest the importance of co2 degassing in the formation of beachrock cement when chemical and tidal cycles fluctuate with the same period pco2 values in pore water of the intertidal zone generally bear a direct relationship to tidal stand increasing values of pco2 most often occur during semi daily rising tides and decreasing values of pco2 occur during falling tides saturation ratios with respect to calcite vary in direct proportion to pco2 saturation levels generally increase during rising tides and decrease during falling tides t ese data suggest that co2 degassing during falling tides results in precipitation of calcite cement from pore water of the beach

genetic implications of the trace element distribution pattern in the upper knox carbonate rocks copper ridge district east tennessee abstract the lower ordovician upper knox group rocks the kingsport and mascot formations in the copper ridge district consist predominantly of fine grained dolostones medium and coarser grained dolostones and limestones dolomite crystals of medium and coarser grained dolostones show up to eight cathodoluminescent zones of variable width and intensity electron microprobe analyses indicate that the zoning is related to variation in fe mn ratios the brighter luminescent zones corresponding to lower ratios superposed on this growth zoning is a compositional zoning characterized by a general increase in fe from core to rim of individual dolomite crystals field and petrographic studies churnet 1979 churnet et al 1981 indicate that the fine grained dolostones formed in supratidal to upper intratidal environments whereas the precursor lime muds of the limestones as well as of the medium and coarser grained dolostones formed in shallow subtidal to lower intertidal environments the large areal extent of the dolostones must have required a regionally abundant source of mg such as marine water yet both limestones and dolostones have low na and sr contents suggestive of their formation in solutions more dilute than normal marine water it is proposed that the fine grained dolostones formed by aggradation of initially very fine grained dolostones in presence of fresh water and that the limestones stabilized and the medium and coarser grained dolostones formed in environments of mixed marine and fresh waters considered in the light of ordering of partition coefficients such a mixing model can account for the observed correlation pattern of trace elements especially s mn and sr fe as well as the fe distribution in the zoned dolomite crystals variation of the partition coefficient of mn due to fluctuations in the relative proportions of fresh and marine waters in the diagenetic solution may explain the different fe mn ratios observed in the growth zones luminescence bands of zoned dolomite crystals

groundwater chemistry in southeast suffolk u k and its relation to quaternary geology abstract east anglia has a complex pleistocene geological history having been affected both by major changes in the level of the adjacent north sea and by glacial processes the resulting geology has a profound effect on the distribution of water chemistry in the chalk aquifer which underlies the pleistocene deposits a detailed study of the chemistry of the chalk groundwater including strontium fluoride and iodide as well as major elements has shown that this chemistry results from three phases of saline intrusion early pleistocene to modern and at least two periods of freshwater flushing climatic changes and erosional history were important in controlling flushing periods

continuous monitoring of fish in a shallow channel using a fixed horizontal sonar an acoustic monitoring program of herring migration in drogden channel near copenhagen denmark was conducted from june 1996 until the end of may 1997 fixed 100 khz side looking sonars provided nearly continuous surveillance in a 1 km wide by 12 m deep navigation channel water temperature salinity and current profiles were simultaneously monitored at this site the sonars were positioned to insonify regions near the seabed at ranges up to 800 m such that the typical reverberation was due to low grazing angle seabed backscatter it was found that under normal weakly stratified flow conditions fish schools attributable to herring clupea harengus were observed from the 50 to 500 m range this could be done despite interference from the dense vessel traffic specifically direct echoes from hulls propeller cavitation noise and bubbly wakes at close ranges 150 m hyperbolic trajectories attributable to individual herring were observed with horizontal advection speeds in close agreement with mea

syntaxial overgrowths in muddy crinoidal limestones cathodoluminescence sheds new light on an old problem lower carboniferous shallow water limestones of asbian and brigantian age in britain commonly contain abundant interparticle micrite and characteristically display large syntaxial calcite overgrowths on crinoid and echinoid grains these overgrowths appear to have developed at the expense of the micrite and are widely regarded as neomorphic replacements however cathodoluminescence of these has revealed growth features which indicate that they are not neomorphic but originated as passive cement fills of solution voids surrounding echinoderm grains we introduce the term solution corona for these grain selective voids and consider that three processes may have contributed to their development namely high mg calcite stabilization of host grains crystal ripening and meteoric dissolution cyclic subaerial emergence was a critical factor in these processes and we contrast the morphology of the overgrowths in question with forms produced in basinal limestones which never experienced comparable early meteoric conditions these early formed solution coronas around echinoderm grains are therefore a useful indicator of meteoric diagenesis and have important implications for porosity evolution the syntaxial cements which fill the solution coronas show distinct phases of growth in cathodoluminescence which reflect a progression from near surface meteoric conditions to deep burial with pressure solution

cathodoluminescence in quaternary carbonate deposits abstract the cathodoluminescent oscillatory and sectoral growth zones common in crystals formed in ancient limestone successions in a variety of putative environments appear to be rare or absent from recent and pleistocene marine carbonate sequences the factors controlling cathodoluminescence and reasons for this disparity are examined the cathodoluminescent zones in the cements of ancient rocks have been interpreted as responses to variations in the redox potential of formative pore waters during crystal growth although similar cathodoluminescent behaviour is recorded from some deposits including travertines and quaternary speleothems formed in what are thought to have been strongly oxidizing environments the apparent absence of cathodoluminescence in the most recent and pleistocene marine deposits that presumably reflect deposition and diagenesis in environments that are also characteristically oxidized therefore seems anomalous the controlling influences on cathodoluminescence are reviewed together with evidence relating to observations of pleistocene marine deposits and likely conditions of formation but where it is present the mechanism s for its development remain elusive

subaqueous shrinkage cracks in the sheepbed mudstone implications for early fluid diagenesis gale crater mars the sheepbed mudstone yellowknife bay formation gale crater represents an ancient lakebed now exhumed and exposed on the martian surface the mudstone has four diagenetic textures including a suite of early diagenetic nodules hollow nodules and raised ridges and later diagenetic light toned veins that crosscut those features in this study we describe the distribution and characteristics of the raised ridges a network of short spindle shaped cracks that crosscut bedding do not form polygonal networks and contain two to four layers of isopachous erosion resistant cement the cracks have a clustered distribution within the sheepbed member and transition laterally into concentrations of nodules and hollow nodules suggesting that these features formed penecontemporaneously because of the erosion resistant nature of the crack fills their three dimensional structure can be observed cracks that transition from subvertical to subhorizontal orientations suggest that the cracks formed within the sediment rather than at the surface this observation and comparison to terrestrial analogs indicate that these are syneresis cracks cracks that formed subaqueously syneresis cracks form by salinity changes that cause sediment contraction mechanical shaking of sediment or gas production within the sediment examination of diagenetic features within the sheepbed mudstone favors a gas production mechanism which has been shown to create a variety of diagenetic morphologies comparable to the raised ridges and hollow nodules the crack morphology and the isopachous layered cement fill show that the cracks were filled in the phreatic zone and that the sheepbed mudstone remained fluid saturated after deposition and through early burial and lithification

diagenetic evaluation of a pennsylvanian carbonate succession bird spring formation arrow canyon nevada u s a 1 brachiopod and whole rock comparison abstract diagenetic evaluation of the pennsylvanian bird spring formation arrow canyon nevada u s a involved the detailed petrographic and geochemical examination of its brachiopod and whole rock components 13 c 18 o and 87 sr 86 sr of whole rock wr statistically p 0 0001 do not agree with isotope values of coeval brachiopod low mg calcite lmc more importantly a detailed investigation of the best preserved fine grained whole rock material demonstrates that it does not universally preserve its carbon isotope values in contrast with hypothetical predictions furthermore lumped trace chemistry or stable isotope tests do not unequivocally identify brachiopod or whole rock fine to coarse grained samples that carry an original seawater signal instead diagenetic evaluation involving as many screening tests as possible on a horizon by horizon level to compensate for spatial and temporal variations is necessary to identify the sample s that carries an original seawater signature many brachiopods from the bird spring formation are blue to non luminescent and carry microstructures and trace element contents similar to those of their modern tropical counterparts concurrence of chemical results between well preserved brachiopods and whole rock if originally low mg calcite is achieved in 22 of coeval samples for 13 c blmc wr with natural limits of 0 25 in 20 of samples for 18 o blmc wr with natural limits of 0 25 and in 9 of samples for 87 sr blmc wr with global limits of 0 000025 after an adjustment for mineralogical fractionation if whole rock is considered originally aragonite the concurrence of 13 c blmc wr drops to 0 and for 18 o blmc wr it drops to 6 furthermore comparison of stable isotopes of our well preserved brachiopods with those of preserved whole rock from the literature suggests that they are significantly different p 0 0001 with results of the latter dataset being more negative by about 0 77 2 57 with mineralogical adjustment for 13 c pdb and 1 31 2 11 for 18 o pdb thus our integrated screening and comparative tests indicate that 1 an overwhelming number of the whole rock samples from the bird spring formation carry a diagenetic instead of a primary signal for both carbon and oxygen isotopes and 2 many of the biogenic low mg calcite brachiopods in this succession carry an original chemical signal suitable for the reconstruction of high resolution seawater isotope curves representative of the pennsylvanian north american epeiric sea and potentially of the global oceans

morphosedimentary evolution of a delta sourced drift aligned sand barrier lagoon complex western bight of benin the coast of eastern ghana and togo is bounded by a major holocene sand barrier complex hinged on the volta delta to the west and subject to high rates of longshore sand drift 1 1 5 106 m3 yr in spite of its proximity to this major deltaic sediment source this barrier system shows marked longshore variations in progradation following the middle holocene eustatic stillstand it is a hybrid system in terms of internal facies composition and plan view morphology in that it has evolved from an essentially regressive to a stationary synonymous with cessation of progradation system both transgressive and barrier inlet facies have also developed through time and space these temporal and spatial changes in patterns of development reflect variations in longshore sand transport and deposition over the last 5000 years such variations have been controlled by sediment supply from the volta by antecedent topography by lagoonal and river drainage by sediment cell development and maturation and in the very recent past by anthropogenic perturbation barrier progradation in the western bight of benin diminished considerably or ceased probably as early as 3400 yr b p as a single major equilibrium drift aligned bight cell matured permitting transport of volta sand toward the rest of the eastern bight in benin and nigeria the eastward longshore supply from the volta has involved both direct inputs of upland derived sand by the volta river channel and reworking of nearshore deltaic deposits a recent reduction in direct fluvial supply exacerbated by the akosombo dam completed in 1961 has induced a wave of erosion of the downdrift delta mouth barrier and shoreface deposits to fulfil the strong drift requirements in togo construction of a deepwater port in 1967 has also affected the barrier system both of these changes have had considerable impacts on longshore sediment dynamics the most significant impact has been segmentation of the former unique sediment cell characterising the 400 km long bight of benin coast resulting in differential longshore erosion progradation or equilibrium these changes have also induced new patterns of barrier behaviour that include transgressive and regressive dynamics at various locations alongshore

hydrochemical evolution of the east midlands triassic sandstone aquifer england a detailed hydrogeochemical interpretation has been made of the red bed sherwood sandstone triassic aquifer of the east midlands of england on which a radiocarbon model has been used to establish a chronology of groundwaters along the flow line groundwater evolution is dominated by carbonate and sulphate mineral solution and precipitation and by redox reactions cation exchange reactions are negligible and the hydrogeochemistry has evolved in the absence of residual saline water three distinct zones are recognised 1 i recent groundwater mainly 100 y oxidising dominated by congruent dissolution of dolomite and by inputs from atmospheric and anthropogenic sources 2 ii groundwater age 103 104 y predominantly reducing dominated by incongruent dissolution of dolomite 3 iii groundwater age 104 y reducing conditions approach to isotopic and chemical equilibrium in the carbonate system dominance of gypsum dissolution the minor and trace element variation can be interpreted in relation to the principal geochemical reactions and recharge history na cl f and b are controlled by atmospheric inputs sr2 and mn2 trends can be explained by carbonate and sulphate mineral dissolution ba2 is derived from carbonates but controlled by barite equilibrium fe so42 no3 and u are strongly influenced by redox reactions the concentrations of transition metals and other elements remain very low only li and k are considered to represent additions by reaction of silicate minerals the extent of direct anthropogenic influence is probably limited to enhanced so4 no32 and possibly cu zn and pb in zone i

estimating the instantaneous velocity of randomly moving target swarms in a stratified ocean waveguide by doppler analysis doppler analysis has been extensively used in active radar and sonar sensing to estimate the speed and direction of a single target within an imaging system resolution cell following deterministic theory for target swarms such as fish and plankton in the ocean and raindrops birds and bats in the atmosphere multiple randomly moving targets typically occupy a single resolution cell making single target theory inadequate here a method is developed for simultaneously estimating the instantaneous mean velocity and position of a group of randomly moving targets within a resolution cell as well as the respective standard deviations across the group by doppler analysis in free space and in a stratified ocean waveguide while the variance of the field scattered from the swarm is shown to typically dominate over the mean in the range velocity ambiguity function cross spectral coherence remains and maintains high doppler velocity and position resolution even for coherent signal processing algorithms such as the matched filter for pseudo random signals the mean and variance of the swarms velocity and position can be expressed in terms of the first two moments of the measured range velocity ambiguity function this is shown analytically for free space and with monte carlo simulations for an ocean waveguide