effects of short term variations in sea level on dissolved oxygen in a coastal karst aquifer quintana roo mexico sea level rise should cause salt water intrusion into coastal aquifers and limit fresh submarine groundwater discharge pargos spring offshore of puerto morelos quintana roo mexico intermittently discharges brackish water and allows intrusion of lagoon water with seawater salinity to the aquifer lagoon water intrusion occurred when sea level was 0 08 m above mean observed values during the study period salt water intrusion will be permanent within a few decades at the current eustatic sea level rise rate of 3 mm yr a mixing model demonstrates that oxygen dissolved in the lagoon water is reduced as it intrudes the spring dissolved oxygen do reduction is greater at the spring vent than at sensors 10 m inside the conduit reflecting rapid reaction kinetics do reduction results from organic carbon remineralization which also releases n and p to the water increased frequency of intrusion events or continuous intrusion may alter microbially mediated biogeochemical reactions thereby increasing aquifer vulnerability to sea level rise

active circulation of saline ground waters in carbonate platforms evidence from the great bahama bank measurements of salinity temperature and ground water discharges within the great bahama bank provide evidence of active circulation of near normal ocean water beneath north andros island elevated salinity waters 38 42 derived by density refulx from the great bahama bank flow eastward beneath the island and mix with normal salinity cold ground waters 19 20 c from deeper than 250 m in the adjacent oceans east to west flow of water from the straits of florida may be driven by head differences generated by the florida current which impinges on the western margins of the platform alternatively density differences between the reflux and tongue of the ocean sea waters may cause more local circulation on the eastern flanks these flows have important diagenetic implications particularly in the explanation of pervasive secondary dolomitization widely reported at shallow depths in the bahamas

porosity development in coastal carbonate aquifers geochemical mixing theory suggests that the mixing of seawater and calcite saturated fresh ground water can result in a solution that is undersaturated with respect to calcite previous studies of the mixing of such waters in carbonate rocks along certain coastlines have indicated that this mixing effect may be responsible for significant amounts of calcite dissolution and porosity development in this study potential rates of porosity development by calcite dissolution are assessed by combining geochemical mixing theory with the hydrodynamics of fresh water salt water mixing zones in a coupled reaction transport model results from the reaction path model phreeqe are used with a variable density ground water flow and solute transport model to simulate an idealized cross section of a coastal carbonate aquifer results of the simulations indicate that the dissolution process is sensitive to fresh water chemistry ground water velocities and sea level movement dissolution potential was evaluated at three field sites and evidence from those sites is in general agreement with the simulation results dissolution rates indicated by the model show that under the proper conditions this dissolution mechanism can produce significant increases in porosity over relatively short spans of geologic time tens of thousands of years

decoupled fresh saline groundwater circulation of a coastal carbonate aquifer spatial patterns of temperature and specific electrical conductivity summary the coastal carbonate aquifer of the eastern yucatan peninsula discharges groundwaters to the caribbean sea temperature and specific electrical conductance sec are used as natural tracers to gain new insight into the fresh and saline groundwater circulation along an 80 km section of the caribbean coastline the aquifer is density stratified with a cooler freshwater lens overlying a warmer saline water zone non conduit sites generally have lower temperatures and sec in the freshwater lens than conduit sites in conduits 4 km inland within the shallow saline water zone temperature decreases exponentially with distance from the coast with near equilibrium with the fresh waters reached at 10 km inland a distance coincident with the known limit of conduit development this pattern is indicative of the progressive cooling of warm seawater moving inland from the coast a flow direction opposite to that of both the conventional freshwater flow entrainment and geothermal convection models of coastal aquifer circulation

groundwater geochemistry of the yucatan peninsula mexico constraints on stratigraphy and hydrogeology summary we report 87sr 86sr and ion concentrations of sulfate chloride and strontium in the groundwater of the northern and central yucatan peninsula mexico correlation between these data indicates that ejecta from the 65 95 m y old chicxulub impact crater have an important effect on hydrogeology geomorphology and soil development of the region ejecta are present at relatively shallow subsurface depths in north central yucatan and at the surface along the rio hondo escarpment in southeast quintana roo where they are referred to as the albion formation anhydrite gypsum and by inference celestite are common in impact ejecta clasts and in beds and cements of overlying paleocene and lower eocene rocks cored around the margin of the crater the sulfate rich minerals that are found in rocks immediately overlying the impact ejecta blanket may either be partially mobilized from the ejecta layer itself or may have been deposited after the k t impact event in an extensive pre oligocene shallow sea these deposits form a distinctive sedimentary package that can be easily traced by the eocene cretaceous 87sr 86sr signal a distinct sr isotopic signature and high so4 cl ratios are observed in groundwater of northwestern and north central yucatan that interacts with these rocks moreover the distribution of the gypsum rich stratigraphic unit provides a solution enhanced subsurface drainage pathway for a broad region characterized by dissolution features poljes extending from chetumal quintana roo to campeche campeche the presence of gypsum quarries in the area is also consistent with a sulfate rich stratigraphic package that includes ejecta the distinctive chemistry of groundwater that has been in contact with evaporite ejecta can be used to trace flow directions and confirms a groundwater divide in the northern peninsula information about groundwater flow directions and about deep subsurface zones of high permeability is useful for groundwater and liquid waste management in the area where it discharges at the coast the unique chemistry of the groundwater that has interacted with the evaporite ejecta strata may also have significant geomorphologic implications while groundwater seawater mixing at the coast has been shown to dissolve and erode limestone phreeqc modeling shows that mixing of water nearly saturated in caso4 with seawater has a less vigorous dissolution effect due to its high ca content

geochemical and isotopic zoning patterns of plagioclase megacrysts in gabbroic dykes from the gardar province south greenland implications for crystallisation processes in anorthositic magmas chemical and sr isotopic zoning patterns in plagioclase megacrysts from gabbroic dykes in the gardar province can be used to elucidate magma chamber and emplacement processes the megacrysts occur either as single crystals or assembled as anorthosite xenoliths the size of the megacrysts varies from 1 cm to 1 m they consist of a large core with variable zonation an58 39 and a relatively small 600 m normally zoned rim an62 27 the contact between core and rim is sharp and marked by a sharp increase in anorthite content which can reach 11 mol an this gap is interpreted as having formed during dyke emplacement due to a sudden pressure release some of the megacryst cores show a fairly constant composition whereas others exhibit an unusual wavy oscillatory zoning which has not been reported elsewhere to our knowledge the oscillatory zoning has wavelengths of up to 2 500 m and a maximum amplitude of 7 mol an it is interpreted as reflecting movements of the crystals in the magma reservoir the sr isotopic composition of one crystal shows a radiogenic inner core 87sr 86sr i 0 7044 and a less radiogenic outer core 87sr 86sr i 0 7039 0 7036 the lack of a significant change between outer core and rim 87sr 86sr i 0 7037 is consistent with formation of the more an rich rim due to pressure release variations in the core may be related to movements of the crystal and or magma mixing a trace element profile across a megacryst shows a small increase in sr and small decreases in ba and la contents of the recalculated melt composition across the core rim boundary whereas p ce nd and eu remain constant melt compositional changes upon emplacement are therefore considered to be of minor importance constant ratios of incompatible trace elements in the megacryst cores indicate a dominant influence of a lower crustal source on trace element budgets

microchemical and sr isotopic investigation of zoned k feldspar megacrysts insights into the petrogenesis of a granitic system and disequilibrium crystal growth k feldspar megacrysts kfm are used to investigate the magmatic evolution of the 7ma monte capanne mc monzogranite elba italy dissolution and regrowth of kfm during magma mixing or mingling events produce indented resorption surfaces associated with high ba contents diffusion calculations demonstrate that kfm chemical zoning is primary core to rim variations in ba rb sr li and p support magma mixing i e high ba and p and low rb sr at rims but more complex variations require other mechanisms in particular we show that disequilibrium growth related to variations in diffusion rates in the melt may have occurred as a result of thermal disturbance following influx of mafic magma in the magma chamber initial 87 sr 86 sr ratios isr obtained by microdrilling decrease from core to rim inner core analyses define a mixing trend extending towards a high isr rb sr melt component whereas the outer cores and rims display a more restricted range of isr but a larger range of rb sr lower isr at the rim of one megacryst suggests mixing with high k calc alkaline mantle derived volcanics of similar age on capraia trace element and isotopic profiles suggest 1 early megacryst growth in magmas contaminated by crust and refreshed by high isr silicic melts as seen in the inner cores and 2 later recharge with mafic magmas as seen in the outer cores followed by 3 crystal fractionation with possible interaction with hydrothermal fluids as seen in the rim the model is compatible with the field occurrence of mafic enclaves and xenoliths

tidal pumping of water between bahamian blue holes aquifers and the ocean summary exchange of water between conduits and aquifers occurs in many continental karst settings because allogenic recharge from confined catchments causes hydraulic heads in conduits to increase faster than in the aquifer most modern carbonate platforms lack allogenic catchments allowing rainfall to recharge the aquifer uniformly without sufficiently altering head gradients to drive exchange between conduits and aquifers some modern carbonate platforms experience tidal variations which could lead to head gradients that drive exchange to determine the impact of tides on exchange we measured water elevations at high temporal resolution in the ocean blue holes and wells on san salvador island and rum cay bahamas dampened tidal amplitudes inland indicate diffusivity values transmissivity storativity at wells were around 1 3 10 6 m 2 day and at blue holes were around 76 9 10 6 m 2 day assuming dampening results only from head loss these diffusivity values were used to estimate hydraulic conductivity values of around 4 0 294 10 4 m day although they may be lower if the aquifer thickness is greater than the estimated 10 m we assume wells provide values representing greater influence of matrix permeability than values from blue holes which represent a greater influence of conduit permeability differences in permeability drive exchange because hydraulic head in the aquifer lags the head in the conduits and blue hole through a tidal cycle if negligible head loss occurs with flow through conduits as reflected in lag times less than 10 min then differences in elevation at the blue holes and the ocean may represent exchange of water between the blue hole and matrix porosity with this assumption about 0 9 m 3 of water is exchanged per half tidal cycle or about 1 of the complete change in volume of water in the blue hole per half tidal cycle this volume represents an average penetration into the aquifer of 6 8 mm although it could be further in zones with elevated permeability exchange is reflected in systematic changes in specific conductivity and ph between high and low tide and the ph changes reflect reaction with the surrounding aquifer material since exchange occurs twice daily cumulative alteration of aquifer porosity could be large tidal exchange should decrease away from the coast on large carbonate platforms so that tidally driven alteration will be enhanced at the rims over interior of carbonate platforms

late holocene mangrove development and onset of sedimentation in the yax chen cave system ox bel ha yucatan mexico implications for using cave sediments as a sea level indicator abstract this study examines the relationship between the flooding of cenotes and formation of coastal mangrove with holocene sea level rise and the onset of aquatic sedimentation in yax chen a cave system in quintana roo on mexico s yucatan peninsula sediment depth measurements n 180 were collected along 2 7 km of an underwater cave passage and three cores were radiocarbon dated to examine both the extent and timing of sedimentation in the cave basal radiocarbon ages 4 ka for aquatic sediments in the cave show that holocene sea level rise flooded cenotes creating sunlit open water conditions with associated mangroves on the upper karst surface these conditions initiated abundant and widespread sedimentation in the cave cenote surface area controlled the long term sediment accumulation in the cave passages through primary productivity in the sunlit open water areas of the cenotes this primary productivity was enhanced with mangrove formation which causes funneling of precipitation and nutrient rich waters into the cenotes from the mangroves accumulation histories from the radiocarbon dated sediment cores n 3 were compared with accumulation histories in previously published studies including actun ha mexico and green bay cave gbc bermuda

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

hurricane ingrid and tropical storm hanna s effects on the salinity of the coastal aquifer quintana roo mexico abstract there is a lack of information on aquifer dynamics in anchialine systems especially in the yucatan peninsula of mexico most of our knowledge is based on spot measurements of the aquifer with no long term temporal monitoring in this study spanning four years 2012 2016 sensors water depth and conductivity salinity were deployed and positioned 9 and 10 m in the meteoric water mass wm close to the transition with the marine wm halocline in 2 monitoring sites within the yax chen cave system to investigate precipitation effects on the salinity of the coastal aquifer the results show variation in salinity 95 mm such as hurricane ingrid 2013 and tropical storm hanna 2014 shows meteoric water mass salinity rapidly increasing approx 6 39 to 8 6 ppt but these perturbations have a shorter duration weeks and days wavelet analysis of the salinity record indicates seasonal mixing effects in agreement with the wet and dry periods but also seasonal effects of tidal mixing meteoric and marine water masses occurring on shorter time scales diurnal and semi diurnal these results demonstrate that the salinity of the freshwater lens is influenced by precipitation and turbulent mixing with the marine wm the salinity response is scaled with precipitation larger more intense rainfall events 95 mm create a larger response in terms of the magnitude and duration of the salinity perturbation 1 ppt the balance of precipitation and its intensity controls the temporal and spatial patterning of meteoric wm salinity

the complex diagenetic history of discontinuities in shallow marine carbonate rocks new insights from high resolution ion microprobe investigation of δ18o and δ13c of early cements sedimentary gaps are a major obstacle in the reconstruction of a carbonate platform s history in order to improve the understanding of the early diagenesis and the succession of events occurring during the formation of discontinuity surfaces in limestones secondary ion mass spectrometry was used for the first time to measure the 18o and 13c signatures of 12 early cement and fabric stages in several discontinuity surfaces from the jurassic carbonate platform of the paris basin pendant cements show a high variability in 18o which was impossible to detect by the less precise microdrilling method the morphology of a given cement can be produced in various environments and dogtooth cements especially can precipitate in marine phreatic and meteoric phreatic to vadose environments marine dogtooth cements and micritic microbially induced fabrics precipitated directly as low magnesium calcite in marine waters as attested by the preservation of their initial 18o and 13c signals five discontinuity types are recognized based on high resolution geochemical analyses and their palaeoenvironmental history can be reconstructed two exposure surfaces with non ferroan pendant or meniscus cements formed in the oxidizing vadose zone a hardground displays marine fibrous cements and non ferroan dogtooth cements that formed in a subtidal environment in oxidizing water two composite surfaces have undergone both marine and subaerial lithification composite surface 1 displays non luminescent ferroan dogtooth cements that precipitated in reduced conditions in seawater followed by brown luminescent dogtooth cements characteristic of a meteoric phreatic environment composite surface 2 exhibits microbially induced fabrics that formed in marine water with abundant organic matter the latter discontinuity initially formed in a subtidal environment was subsequently exposed to meteoric conditions as evidenced by ferroan geopetal cements a high resolution ion microprobe study is essential to precisely document the successive diagenetic environments that have affected carbonate rocks and discontinuities with a polygenic and intricate history this article is protected by copyright all rights reserved

high resolution spectrometric analysis of rare earth elements activated cathodoluminescence in feldspar minerals abstract cathodoluminescence cl investigations of igneous metamorphic and sedimentary feldspars indicate that rare earth elements ree activated cl in feldspars is more common than previously assumed hot cathode cl microscopy combined with high resolution spectrometric analysis of cl emission allow to detect some ree below the detection limits of electron microprobe and proton induced x ray emission analysis pixe and reveal variations in the ree distribution within single feldspar crystals differently luminescing zones can reflect changes during feldspar crystallization and or element fluctuations during secondary alteration processes which are not discernible using conventional polarizing microscopy the results of the study document eu 2 sm 3 dy 3 tb 3 and nd 3 activated cl in feldspars of different origin the influence of the crystal field on shape and position of ree luminescence spectra significantly differs for divalent and trivalent ree ions whereas eu 2 shows a broad band emission 420 nm which is influenced by the local crystal field trivalent ions of the rare earth show narrow emission lines which reflect the transitions between excited state wave functions lying inside closed electronic shells the positions of these peaks and the characteristic energies are described for the different ree 3

calcite raft geochemistry as a hydrological proxy for holocene aquifer conditions in hoyo negro and ich balam sac actun cave system quintana roo mexico abstract two cores from calcite rafts deposits located in cenote ich balam and hoyo negro were dated and analyzed for 87sr 86sr 18o 13c sr ca and cl ca the geochemical records show changing aquifer salinity spanning the last 8 5 cal kyrs bp and interrelationships with holocene climate trends wet and dry periods during the wet mid holocene the salinity of the meteoric water mass wm at 7 8 8 3 cal kyrs bp was relatively high at 1 5 2 7 ppt and then became less saline 1 0 1 5 ppt during the last 7000 yrs as climate became progressively drier high salinity of the meteoric wm during the wet mid holocene is attributed to increased turbulent mixing between the meteoric and underlying marine wm increased precipitation in terms of amount frequency and intensity e g hurricanes causes higher flow of meteoric water towards the coast and mixing at the halocline a phenomenon recorded with recent instrumental monitoring of the aquifer conversely during dry periods reduced precipitation and flow in the meteoric wm would result in lower salinity karst properties and holocene sea level rise also seem to have an effect on the aquifer when the regionally extensive network of shallow cave passages 10 12 m water depth are flooded at 8000 cal yrs bp there is a rapid shift in salinity this study demonstrates that calcite raft deposits can be used as paleo environmental recorders documenting the effects of sea level and climate change on aquifer condition

magma evolution recorded in plagioclase zoning in 1991 pinatubo eruption products plagioclase the most abundant phenocryst at mount pinatubo displays varying textures and compositions within the 1991 eruption products in june 7 14 dome forming andesite plagioclase phenocrysts show prominent rims with higher mgo 0 04 0 06 wt jo fe20j 0 6 0 8 wt o and k20 at given an than the interiors the compositions of the rims are identical to those of microlites which are abundant in the groundmass glass white dacitic pumice the most voluminous product of the june 15 eruption contains partly corroded plagioclase phenocrysts but no prominent rims and no microlites the interiors of phenocrysts from the dacitic pumice and the dome forming andesite are remarkably similar in terms of textures and compositions they show oscillatory zoning mostly an35 6o low mgo 0 02 wtojo and fe20j 0 10 0 30 wt jo and similar k20 at given an this similarity indicates that the two types of plagioclase phenocrysts formed in the same rhyolitic melt the oscillatory zoning likely formed by temperature fluctuations in the convecting magma and incorporation and degassing of external fluids a portion of the felsic magma 800 c mixed with a mafic melt 1000 1100 c to become an andesitic magma that extruded to form the june 7 14 dome all plagioclase phenocrysts in the andesite were derived from the felsic magma the mixing caused destabilization of phenocrysts forming sieve textures dusty zones and partial resorption extrusion of the mixed magma resulted in overgrowths on once resorbed phenocrysts and the nucleation of plagioclase microlites in the groundmass glass in the unmixed remaining portion of the felsic magma some plagioclase underwent partial resorption but did not develop overgrowths this lack of overgrowths and the absence of micro lites in the groundmass glass of the june 15 dacitic pumice indicate rapid magma ascent during the eruption and a short time span between the injection of a mafic melt and the cataclysmic eruption supporting the linkage between the two

speleothem constraints on marine isotope stage mis 5 relative sea levels yucatan peninsula mexico rates of sea level fall at the termination of the last interglacial are poorly defined and archives from which sea level elevations are constrained during marine isotope stage mis 5 in the western north atlantic caribbean region are restricted spatially to a few key sites here growth periods of presently submerged but subaerially deposited speleothems from the yucatan peninsula south east mexico are dated using the 230 th 234 u multi collector inductively coupled plasma mass spectrometric method the growth periods used to constrain maximum elevations of relative sea level are in agreement with glacio isostatic adjustment models for the near to intermediate region of the former north american ice sheets furthermore our data provide additional constraints on the timing of peak relative sea levels during mis 5a and 5c and the timing of the regression following the last interglacial highstand combining our data with coral archives of minimum relative sea level from the same region provides a novel approach to calculating the rate of relative sea level fall although initial estimates are poorly constrained because of the wide range in ages observed for the most suitable corals copyright 2013 john wiley sons ltd

geochemistry and provenance of the altendorf feldspathic sandstone in the middle bunter of the thuringian basin germany an integrated mineralogical and geochemical study of the altendorf feldspathic sandstone in the middle bunter of the thuringian basin germany was carried out to obtain more information on its provenance sedimentological history and geochemistry the fine to coarse grained sandstone has an average composition of 66 63 71 quartz 30 27 35 feldspar and a fine grained illitic matrix the heavy mineral assemblage consists mainly of tourmaline zircon rutile apatite and opaque fe ti minerals it is inferred that this terrigenous material was laid down at the margin of the bunter basin high abundances of igneous quartz grains determined by cathodoluminescence cl the lack of metamorphic heavy minerals as well as alkali feldspar with an average k2o na2o ratio of 14 9 point to material of mostly granitic origin regional geologic and paleogeographic observations suggest that granites of the older and younger intrusive complex of the western erzgebirge are possible source rocks of the feldspathic sandstone the geochemical signature of the alkali feldspar k2o na2o ratio bao content points to the bergen and kirchberg granites as possible parent rocks comparing the mineralogical and geochemical data of the presumed source granites with those of the altendorf sandstone provides information on the sedimentation processes weathering fluvial transport and sedimentation under arid climatic conditions have caused complete decomposition and removal of plagioclase and biotite lowered the bulk ree content and led to the development of a positive eu anomaly the immobile trace elements e g ta th zr sc co ti are best suited for provenance determination because of their relatively low mobility during sedimentary processes elemental ratios such as la sc th sc co th and th ta have inherited the signature of the parent rocks and thus may be particularly useful for provenance studies to evaluate the control of specific minerals and grain size fractions on the distribution of trace elements in the sandstone separated fractions of quartz feldspar the 20 m fraction and heavy minerals were additionally analyzed the concentration densities elemental concentration in the fraction fraction weight reveal that with exception of hf the influence of the heavy mineral fraction on the whole rock geochemistry is insignificant although this fraction generally plays the most important role as carrier of trace elements quartz feldspar and the 20 m fraction have similar concentration densities between 20 and 40 for the ree with exception of eu which is mainly hosted in feldspar strong positive eu anomaly the influence of the 20 m fraction on the distribution of the ree and the elements u th sc ta strongly depends on the abundance of this fraction in the sediment alkali feldspar contains most of the ba sr rb and cs in the samples concentration densities of up to 97 thus differences in the abundances of these elements in whole rock samples can be related to changes in the mineralogical composition quartz feldspar ratio of the sediment

experimental partitioning of rb cs sr and ba between alkali feldspar and peraluminous melt hydrous partial melting experiments performed between 650 and 750 c at 200 mpa h20 on synthetic metapelite compositions quartz albite muscovite biotite mineral mixtures doped with ba sr rb and cs yielded alkali feldspar crystals with a wide range of compositions in equilibrium at their rims with peraluminous melt measured partition coefficients for normally trace lithophile elements between feldspar and melt d m fsp gl m ba sr rb cs do not depend on either temperature or bulk composition of melt for the compositions studied values of d sr fsp gl are between 10 and 14 and appear to be independent of the albite and orthoclase contents of the feldspar crystals in contrast values of d ba fsp gl and d rb fsp glare strongly dependent on the orthoclase content of feldspar relationships that can be expressed by the following linear equations d ba fsp gl 0 07 0 25 orthoclase and d rb fsp gl 0 03 0 0 1 orthoclase where orthoclase is in mole percent these equations reproduce the range of previously reported values for d ba and d rb determined on natural and synthetic samples a single partition coefficient for cs was also determined at d cs fsp gl 0 13 these data can be used in conjunction with recently published partition coefficients for muscovite biotite and plagioclase feldspars blundy and wood 1991 icenhower and london 1995 to model quantitatively the trace element signatures of peraluminous magmas during anatexis and crystallization depending on bulk composition and pressuretemperature trajectories during episodes of partial melting ba and sr and to a lesser extent rb are retained at the source while cs and li are enriched in the first melts these results explain why peraluminous granitic magmas with s type sedimentary sources carry a distinctive enrichment in li and cs

seasonal trends in calcite raft precipitation from cenotes rainbow feno and monkey dust quintana roo mexico implications for paleoenvironmental studies abstract calcite raft precipitation was monitored in three yucatan cenotes rainbow feno and monkey dust over a 2 year period site specific variables including water temperature relative humidity water level and salinity were recorded as well as rainfall cozumel calcite raft surface area was monitored through trail cameras that collected photographs every 60 min accumulation rates were recorded using sediment traps that were collected in may and december of each year calcite raft surface area was calculated using an image segmentation procedure that identified the boundary of objects edge detection that share certain pixel characteristics removed non points of interest and measured the sum of the area covered by the raft material results show that large rainfall events have a regional effect on the meteoric water mass i e salinity as well as the precipitation of calcite rafts the large rainfalls and increased inflows cause dilution of the caco3 supersaturated meteoric water mass and cause increased flow hindering calcite raft precipitation for days to weeks after the rainfall raft precipitation gradually returns with deceasing flow after the event and stagnation allows the recurrence of caco3 supersaturation and accumulation of nucleation particles small rainfalls did not seem to have the same effect as slower percolation of rainwater through the epikarst would be more saturated and micro topographic relief may isolate the water pools from the lower flow the sediment trap data shows that calcite rafts accumulate relatively constantly throughout the year in all three sites sedimentation rates from feno and monkey dust responded to seasonal changes in surface water disturbance associated with rainfall wet and dry although rainbow didn t show any seasonality likely due to other site specific factors affecting water disturbance e g bats wind

early middle holocene relative sea level oscillation events recorded in a submerged speleothem from the yucatan peninsula mexico geomorphological and biological archives of relative sea level change in the western north atlantic caribbean region following the last glacial maximum have traditionally supported the hypothesis o

gradients in fluid composition across metacarbonate layers of the wepawaug schist connecticut usa metamorphic index mineral zones pressure temperature p t conditions and co2 h2o fluid compositions were determined for metacarbonate layers within the wepawaug schist connecticut usa peak metamorphic conditions were attained in the acadian orogeny and increase from 420 c and 6 5 kb in the low grade greenschist facies to 610 c and 9 5 kb in the amphibolite facies the index minerals oligoclase biotite calcic amphibole and diopside formed with progressive increases in metamorphic intensity in the upper greenschist facies and in the amphibolite facies prograde reaction progress is greatest along the margins of metacarbonate layers in contact with surrounding schists or in reaction selvages bordering syn metamorphic quartz veins new index minerals typically appear first in these more highly reacted contact and selvage zones it has been postulated that this spatial zonation of mineral assemblages resulted from infiltration largely by diffusion of water rich fluids across lithologic contacts or away from fluid conduits like fractures in this model the infiltrating fluids drove prograde co2 loss and were derived from surrounding dehydrating schists or sources external to the metasedimentary sequence the model predicts that significant gradients in the mole fraction of co2 x co 2 should have been present during metamorphism but new estimates of fluid composition indicate that differences in x co 2 preserved across layers or vein selvages were very small 0 02 or less however analytical solutions to the two dimensional advection dispersion reaction equation show that only small fluid composition gradients across layers or selvages are needed to drive prograde co2 loss by diffusion and mechanical dispersion these gradients although typically too small to be measured by field based techniques would still be large enough to dominate the effects of fluid flow and reaction along regional t and p gradients larger gradients in fluid composition may have existed across some layers during metamorphism but large gradients favor rapid reaction and would therefore seldom be preserved in the rock record most of the h2o needed to drive prograde co2 loss probably came from regional dehydration of surrounding metapelitic schists although h2o rich diopside zone conditions may have also required an external fluid component derived from syn metamorphic intrusions or the metavolcanic rocks that structurally underlie the wepawaug schist

comment and reply on porosity development in coastal carbonate aquifers sanford and konikow 1989a in comparing their numerical model of coastal carbonate aquifers to the yucatan peninsula concluded that the model results were in general agreement with the rates of dissolution estimated by hanshaw and back 1980 the agreement may be fortuitous because the location of the steady state mixing zone predicted by the model is a poor representation of the actual mixing zone observed between playa del carmen and tulum which is the most intensively studied part of the coastal aquifer sanford and konikow s model predicts that the 50 isoline for mixing of fresh water and seawater will be at a depth of 100 m at a position 650 m inland from the coast the halocline has been observed by cave divers at a depth of 18 m in a cave located 11 km inland from the coast on the basis of the haloclines in several caves the layer of lower

detachment folding related miocene submarine slope instability in the romagna apennines italy 1 the relationships between slope failure and growing thrust related structures have been explored in the miocene marnoso arenacea foredeep basin romagna apennines impressive fossil slump layers are distributed along the footwall of the regional mount nero thrust which evolved from detachment fold to breakthrough thrust during the detachment fold stage development of growth strata on the rotating forelimb was preceded by the emplacement of slump layers that are currently part of the mount nero thrust footwall in this process sliding is assumed to nucleate along the contacts between different lithologies in the semiconsolidated rock mass the conditions of sliding specifically the critical angle of sliding crit are quantified by adding the influence of cohesion of sediments to the equilibrium analysis reported in hubbert and rubey s 1959 classical work the resulting angles crit are discussed with respect to the depth of the basal surface of sliding and pore fluid pressure states on the basis of such an analysis and field work results an evolutionary model is proposed in which slide sheets come from the crest and upper forelimb of growing detachment folds and attain a deeper detachment depth as the forelimb rotates and steepens pore fluid pressure is found to play a major role by radically decreasing the critical angle of sliding likewise localization of overpressures may also control the depth of sliding during progressive forelimb rotation to allow sliding along gently dipping bedding surfaces slope failure is interpreted as being related to the reactivation of anisotropies represented by lithological discontinuities

modelling karst aquifer evolution in fractured porous rocks abstract the removal of material in soluble rocks by physical and chemical dissolution is an important process enhancing the secondary porosity of soluble rocks depending on the history of the soluble rock dissolution can occur either along fractures and bedding partings of the rock in the case of a telogenetic origin or within the interconnected pore space in the case of eogenetic origin in soluble rocks characterised by both fractures and pore space dissolution in both flow compartments is possible we investigate the dissolution of calcite both along fractures and within the pore space of a limestone rock by numerical modelling the limestone rock is treated as fractured porous aquifer in which the hydraulic conductivity increases with time both for the fractures and the pore spaces we show that enlargement of pore space by dissolution will accelerate the development of a classical fracture dominated telogenetic karst aquifer breakthrough occurs faster in the case of a pore controlled aquifer as in eogenetic rocks enlargement of pores results in a front of enlarged pore spaces migrating into the karst aquifer with more homogeneous enlargement around this dissolution front and later breakthrough

the mineralogy of the kokchetav lamproite implications for the magma evolution abstract kokchetav lamproite occurs in the east end of kokchetav massif and consists of phenocryst mainly clinopyroxene and matrix mainly feldspar the compositions of clinopyroxene magnetite and biotite phenocryst were determined using wavelength dispersive spectrometry on a jeol super probe 8900 electron microprobe for the purpose of revealing the process of magma evolution analyses revealed a core rim variation which is consistent with three stages of magmatic evolution mg rich clinopyroxene cores diopside and biotite cores phlogopite crystallized in a deep magma chamber stage i fe rich clinopyroxene rim salite and biotite rim crystallized at low pressure in a shallow magma chamber stage ii magnetite phenocryst core also crystallized in a shallow magma chamber and co exists with fe rich clinopyroxene rim and biotite rim the magnetite rims probably formed during magma eruption at the same time when groundmass crystallized stage iii the calculated temperatures for ilmenite magnetite pair range from 679 to 887 c log f o 2 values range from 11 1 to 14 9 log units these values represent the latest conditions of magma as ilmenite exsolution in magnetite probably occurred during magma eruption from the shallow chamber to surface

intertidal and subtidal benthic foraminifera in flooded caves implications for reconstructing coastal karst aquifers and cave paleoenvironments abstract coastal karst aquifers have an upper meteoric water mass stratified from a saline groundwater mass below that increasingly mix and discharge towards the ocean preserved sediment in caves and sinkholes provide an opportunity to evaluate the long term hydrodynamics in the local coastal karst aquifer e g salinity oxygenation vertical displacement in response to sea level forcing here we evaluate the response of shallow 45 m versus 63 m mesh sieve fractions these modern analog results can be used to interpret subfossil benthic foraminiferal records from coastal karst aquifers especially during early cave inundation by concomitant groundwater and sea level rise

the effect of seasonal rainfall on nutrient input and biological productivity in the yax chen cave system ox bel ha mexico and implications for μxrf core studies of paleohydrology abstract lakes and speleothems from mexico s yucatan peninsula have been used extensively over the past decades for paleoclimate studies however aquifer condition and its response to climate change has received little attention cenotes sinkholes and coastal caves have been shown to record the paleohydrology of the aquifer but there is little information on sedimentation in these cave systems and its response to climate change newly developed xrf instrumentation for the analysis of cores can achieve subannual resolution due to small measurement increments but short period studies examining weathering inputs and rainfall have not yet been undertaken hindering paleoenvironmental interpretations of lake and cave sediment records this study examines the spatial and temporal relationship of cave sediment geochemistry in the anchialine cave system of yax chen quintana roo mexico sediment traps n 51 were placed at seventeen stations along the 2 7 km flooded cave system which transitions from mangrove to upland forest terrain with cenotes of variable size and frequency along its length sediment traps were collected every 6 months from may 2013 may 2017 along with rainfall and groundwater level data there are distinct responses of lithogenic fe ti sr limestone weathering and biogenic influenced si k s phytoplankton and mangrove sediment elements in the sediment samples associated with seasonal rainfall and hurricanes while lithogenic elements ti k show a direct relationship seasonal rainfall the sedimentation of biologically influenced si ti elements exhibit a 6 12 month lagged response with large rainfalls such as hurricane ingrid in 2013 and other tropical storms throughout the study period

crystallization of the shap granite evidence from zoned k feldspar megacrysts textural chemical and sr isotopic studies of feldspars from the subsolvus shap granite northern england demonstrate that a number of magma mixing events have dominated the evolution of this pluton k feldspar megacrysts are phenocrysts formed in the magma chamber they contain a number of ba rich zones that developed during periods of slight dissolution and regrowth linked to the hybridization of the granite by the intrusion of basic magmas diorite enclaves represent the relicts of these magmas and these also contain k feldspar megacrysts which show evidence of major dissolution they are xenocrysts picked up from the host granite and incorporated in the basic magma increasing h 2 o contents during fractional crystallization caused a late switch from growth of megacrysts to finer grained k feldspars in the matrix the chemically and isotopically zoned k feldspar megacrysts preserve an exceptional record of the evolution of the magma and the zones also had a significant influence on the development of exsolution microtextures during cooling

high resolution temperature measurements in the borehole yaxcopoil 1 mexico within the frame of the international continental deep drilling program icdp and as a part of the chicxulub scientific drilling project csdp high resolution temperature measurements were performed in the borehole yaxcopoil 1 yax 1 the temperature was logged to the depth of 858 m seven times between march 6 19 2002 starting 10 days after the hole was shut in and mud circulation ceased successive logs revealed only small temperature variations in time and space indicating a fast temperature recovery to almost undisturbed conditions prior to the first log from these logs a mean temperature gradient of 37 mk m was determined below the uppermost 250 m another temperature log was recorded on may 24 2003 15 months after the shut in to a depth of 895 m the obtained temperature profile is very similar to the 2002 profile with an insignificantly higher mean gradient below 250 m that may indicate a long term return to the pre drilling temperature the temperature in the uppermost part of the hole bears signs of considerable influence of a convective contribution to the vertical thermal heat transfer the depth extent of the convection seems to have deepened from 150 m in march 2002 to 230 m in may 2003 based on the observed temperature gradient and the rock types encountered in the borehole above 670 m the conducted heat flow is expected to be in the range 65 80 mw m2

the use of sulfur hexafluoride sf6 as a tracer of septic tank effluent in the florida keys to determine the fate and movement of sewage derived contaminants and their possible interaction with surface waters in the florida usa keys two types of experiments were conducted using sf6 as an artificial tracer the first type of experiment examined fluid flow from septic tanks placed in miami oolite on big pine key where there is a shallow freshwater lens overlying saline groundwaters here groundwater transport rates were constrained to be between 0 11 and 1 87 m h travelling in an easterly direction the second type of experiment took place on key largo where there is no freshwater aquifer and the matrix of the aquifer is solely the more porous key largo limestone here we injected the tracer into a shallow well which was screened from 0 6 to 10 m this allowed us to evaluate groundwater movement in the shallow upper portion of the aquifer the area to which inputs by septic tanks occur groundwater transport rates in the upper keys were as great as 3 7 m h and were controlled by the atlantic tide sf 6 laden groundwater plumes moved back and forth due to tidal pumping and reached nearby surface waters within 8 h q 1999 elsevier science b v all rights reserved

yucatan subsurface stratigraphy implications and constraints for the chicxulub impact much of the discussion about the effects of an end of cretaceous impact by a large extraterrestrial body in northwestern yucatan has been done in the context of limited and partly erroneous published data on the mesozoic stratigraphy of that area reexamination of cores and geophysical logs taken in several pemex wells has produced improved lithologic and biostratigraphic correlation of the jurassic to maastrichtian section across the northern yucatan peninsula these data suggest that major disturbance of strata by an impact would have been confined to within about 100 km of the proposed impact center near chicxulub the only unusual lithologic unit is polymict breccia which apparently was penetrated at or near the top of the cretaceous section in all the deep wells of northern yucatan this breccia in pemex wells yucatan 1 2 4 5a and 6 is composed predominantly of detrital dolomite limestone and anhydrite clasts set in dolomitized carbonate mud matrix which contains upper maastrichtian foraminifers these constituents mixed with fragments of altered glass or melt rock shocked quartz and feldspar and basement rock suggest an impact as the most likely origin for the breccia the timing of brecciation is poorly constrained by biostratigraphic data there is some evidence however that the breccia unit is overlain by about 18 m of uppermost maastrichtian marls suggesting an impact before the cretaceous tertiary boundary in addition there may have been more than one episode of breccia deposition

hurricanes ingrid and manuel 2013 and their impact on the salinity of the meteoric water mass quintana roo mexico abstract we report on measurements of the salinity and temperature in the yax chen cave system on the yuacatan peninsula this paper is submitted together with kovacs et al 2017 kovacs et al focuses on the salinity levels of the meteoric lens while this paper uses the observed results to elucidate the hydrodynamics the cave passages have water depths on the order of 10 m with flow on the order of ten centimeters a second and as such is a hydrodynamic as opposed to a porous system the measurements reveal that episodes of significant mixing between the fresh meteoric lens and the underlying salty water are driven by meteorological events e g hurricane rina in 2011 and the twin hurricanes ingrid and manuel in 2013 we find evidence that after the hurricanes in 2013 the water column remains unstable for several months through wavelet analysis we find that the marine water mass wm exhibits much less low period activity compared to the meteoric wm we hypothesize that the open cenotes are locations of high mixing intensity with turbulent fronts propagating away from the sites of direct mixing into the cave network we perform laboratory experiments and numerical simulations to explore this phenomenon and find that mixing preferentially occurs on the flanks of regions of strong stable density stratification i e on the periphery of pycnoclines and leads to entrainment of fluid into the turbulent region using high resolution direct numerical simulation we explore the detailed manner in which turbulent entrainment can drive flow toward the mixing region and lead to mixing of passive tracers finally we discuss the implications of these results for the mixing of passive tracers such as suspended chemicals

sea level rise and coastal circulation controlled holocene groundwater development in bermuda and caused a meteoric lens to collapse 1600 years ago abstract the recent report from working group ii of the intergovernmental panel on climate change ipcc called for an increased understanding of how groundwater interacts with the ocean atmospheric system this remains a prerequisite to better understand how groundwater will respond to climate change however achieving this goal is hampered by several problems including 1 our minimal understanding of how current groundwater conditions evolved and responded to previous climatic perturbations and 2 the scarcity of techniques available for evaluating prehistoric groundwater subfossil benthic foraminifera in underwater caves are an overlooked method of evaluating prehistoric groundwater on coastal carbonate terrain because they provide a proxy for groundwater salinity and circulation twelve radiocarbon dates and foraminiferal paleoecology from two sediment cores obtained from green bay cave gbc bermuda provide the first holocene scale groundwater reconstruction first the cave floor 20 7 mbsl was flooded at 7 7 ka as north atlantic sea level and groundwater rose in near synchrony over the holocene groundwater conditions salinity circulation and degree of oxygenation shifted a minimum of five times primarily in response to sea level rise most importantly we provide evidence that a prehistoric meteoric lens collapsed at 1 6 ka as sea level rise breached a local sill and completely altered bermudian coastal circulation the complete loss or retreat of a groundwater mass associated with a minor sea level change validates some numerical predictions that small changes in sea level can destabilize coastal groundwater resources when coastal geometry and circulation are considered

hells bells unique speleothems from the yucatan peninsula mexico generated under highly specific subaquatic conditions abstract we here report on a type of meter sized pendant speleothem growing under water in the submerged el zapote sinkhole cenote west of puerto morelos on the mexican yucatan peninsula these conical mantle shaped downward expanding and diverging calcareous structures here termed as hells bells are yet unreported in the scientific literature they are characterized by bell or trumpet shaped longitudinal and circular elliptical or horse shoe like horizontal cross sections hells bells grow downward based on the downward divergence of the structures and the horizontally laminated internal texture of both blade shaped spar calcite and microspar laminae age dating confirms that hells bells are young

ring of cenotes sinkholes northwest yucatan mexico its hydrogeologic characteristics and possible association with the chicxulub impact crater a 180 km diameter semicircular band of abundant karst sinkholes ring of cenotes in northwest yucatan mexico coincides approximately with a concentric ring of the buried chicxulub structure a circular feature manifested in cretaceous and older rocks that has been identified as the product of the impact of a bolide the ring expressed in tertiary rocks marks a zone of high permeability as shown by 1 the sinkholes themselves 2 breaks in the coastal dune system and high density of springs where the ring intersects the coast and 3 water level transects characterized by a decline in water level toward the ring any direct relation that exists between the ring of cenotes and the chicxulub structure bears on regional hydrogeology if the layer or zone responsible for the ring is deeply buried it may act as a barrier to the movement of ground water across the main flow direction shallower zones of horizontal permeability could result in less complete diversion of ground water through its influence on yucatan aquifer characteristics the ring may provide a link between modern environmental problems and astrogeology possible origins for the ring of cenotes are 1 faulting perhaps reactivated by post eocene mid miocene basin loading 2 permeability in a buried reef complex developed in the shallow paleocene sea around the crater rim or 3 breccia collapse occasioned by consolidation or by solution of evaporite components if the ring developed on ancient faults it may outline hydrothermal systems and mineral deposits produced during paleocene cooling of the chicxulub melt sheet

distribution of trace metals in anchialine caves of adriatic sea croatia abstract this study presents results of the first comprehensive research on ecotoxic trace metals cd pb cu and zn in aquatic anchialine ecosystems data show the influence of hydrological and geological characteristics on trace metals in highly stratified anchialine water columns distribution of cd pb cu and zn in two anchialine water bodies bjejajka cave and lenga pit in the mljet national park croatia were investigated seasonally from 2006 to 2010 behaviour and concentrations of dissolved and total trace metals in stratified water columns and metal contents in sediment carbonate rocks and soil of the anchialine environment were evaluated trace metals and dissolved organic carbon doc concentrations in both anchialine water columns were significantly elevated compared to adjacent seawater zn and cu concentrations were the highest in the lenga pit water column and sediment elevated concentrations of zn pb and cu in bjejajka cave were mainly terrigenous significantly elevated concentrations of cadmium up to 0 3 g l 1 were found in the water column of bjejajka cave almost two orders of magnitude higher compared to nearby surface seawater laboratory analysis revealed that bat guano was the major source of cadmium in bjejajka cave cadmium levels in lenga pit which lacks accumulations of bat guano were 20 fold lower moreover low metal amounts in carbonate rocks in both caves combined with mineral leaching experiments revealed that carbonates play a minor role as a source of metals in both water columns we observed two types of vertical distribution pattern of cadmium in the stratified anchialine bjejajka cave water column at lower salinities non conservative behaviour was characterized by strong desorption and enrichment of dissolved phase while at salinities above 20 cd behaved conservatively and its dissolved concentration decreased conservative behaviour of cu pb zn and doc was observed throughout the water column after heavy rains cd showed reduced concentration and uniform vertical distribution suggesting a non terrestrial origin under the same conditions concentrations of total and dissolved pb cu zn and doc were significantly elevated variations of trace metal vertical distributions in anchialine water columns were caused by large inputs of fresh water extraordinary rainy events and were not influenced by seasonal changes

linkages between holocene paleoclimate and paleohydrogeology preserved in a yucatan underwater cave abstract three sediment cores spanning the last 4200 years from aktun ha cave on the yucatan peninsula mexico demonstrate that underwater caves can document changes to regional hydrogeology and climate benthic microfossils testate amoebae foraminifera organic matter geochemistry 13 c 15 n c n and particle size distributions were analyzed however microfossil paleoecology proved the most useful for indicating three salinity phases in the aktun ha sediment cores phase 1 4300 yr bp contains predominantly foraminifera physalidia simplex 78 that indicate the meteoric lens flooding the cave was initially brackish salinity 3 5 g l 1 phase 2 2800 4300 cal yr bp has both freshwater testate amoebae centropyxis spp 40 and p simplex 42 which indicates a slight freshening of the meteoric lens to 1 5 2 g l 1 phase 3 lagenodifflugia vas and difflugia oblonga with a reduction in p simplex 10 this last faunal shift represents the initiation of modern freshwater conditions in the cave 1 5 g l 1 this final freshening is synchronous with a significant reduction in the c n ratio e g core 2 27 to 19 which suggests an expansion of primary productivity in the adjacent cenote the 15 n values ranged from 1 5 to 3 5 with observed cycles likely from intervals of increased terrestrial om input into the cave during high rainfall events e g hurricanes the observed paleoenvironmental shifts in the cave correlate well with regional precipitation patterns aquifer recharge and storm activity caused by southward migration of the intertropical convergence zone therefore regional climate change impacted eastern yucatan groundwater during the mid to late holocene however decelerating holocene sea level rise and aquifer occlusion are likely contributing factors these results demonstrate that underwater cave sediments and microfossils can be useful proxies for aquifer evolution and climate change

volcanogenic origin of cenotes near mt gambier southeastern australia abstract the cenotes near mt gambier are circular cliffed collapse dolines containing water table lakes up to 125 m deep floored by large rubble cones they lie in a flat coastal plain composed of mid tertiary limestone most of the deepest cenotes are concentrated in two small areas located along trends sub parallel to the main joint direction in the limestone the cenotes do not connect to underwater phreatic passages and water chemistry data confirm that they are not part of an interconnected karst network they formed by collapse into large chambers up to 1 million m 3 that extended 125 m or more below the land surface several cenotes have actively growing stromatolites on the sub vertical walls that started growing at 8000 years bp the caves that collapsed to form the deep mt gambier cenotes are much larger than shallow and deep phreatic caves in the area and do not connect into deep phreatic systems they were not formed by freshwater seawater mixing responsible for many of the well known yucatan cenotes because they are not associated with locations of the mixing zone during previous high sea levels and are much larger than caves presently forming along the mixing zone near mt gambier instead dissolution was most likely due to a process whereby acidified groundwater containing large amounts of volcanogenic co 2 ascended up fractures from the magma chambers that fed the pleistocene holocene volcanic eruptions in the area deep reservoirs of volcanogenic co 2 occur nearby cave dissolution could have been due to release of co 2 during the mt gambier eruption 28 000 years ago followed by collapse to form cenotes during the low sea levels of the last glacial maximum 20 000 years ago the cenotes then flooded 8000 years ago as sea level rose and stromatolites began to grow on the walls

fate of reflux brines in carbonate platforms active reflux may occur during periods of platform top brine generation but the role and fate of these brines after reflux events are uncertain we have used a numerical flow model to investigate and quantify the response of reflux brines to changes in platform top salinity simulations suggest that reflux brines originally concentrated to gypsum saturation 150 have a relatively long platform residence time on the order of 100 times the duration of the reflux event when brine generating conditions cease brines will continue to sink through the platform entraining seawater a variant of reflux circulation we term latent reflux mesosaline brines intercepted by drilling of carbonate margins by the ocean drilling program may have originated from pleistocene reflux event s on the adjacent platform top and be currently moving by latent reflux latent reflux circulation could deliver a significant quantity of dissolved reactants to platform carbonates including mg for dolomitization

coral geochemical record of submarine groundwater discharge back to 1870 in the northern south china sea abstract the importance of submarine groundwater discharge sgd is becoming increasingly recognized because of its potential significance as a source of dissolved species to explore the probable coral geochemical signal of sgd and verify the validity of potential reliable proxies multiple geochemical proxies over the last 137 years were identified from a porites coral near a subterranean estuary in the northern south china sea where the sgd was reported to be the predominant flux of terrestrial waters to the coastal ocean results indicated that the sgd in the coastal zone was the dominant source of trace elements especially ree and ba due to the various dissolution reactions occurring during groundwater flow in the karst terrain the time and frequency domain comparison between the coral geochemical proxy and the local regional precipitation indicated that coral ree ca ratios are predominantly impacted by the sgd associated with local precipitation while coral ba ca ratios are also affected by the primary productivity and allochthonous seawater ba from surrounding areas the ree signal from coral allows us to reconstruct the coastal surface seawater ree concentrations and the sgd rates on the coast of sanya during 1870 2006 in a novel approach to developing a proxy for historic sgd to coastal waters this study provides evidence that the coral ree ca record from the karst coast with large sgd has potentials to be a promising paleohydrological indicator

low frequency storminess signal at bermuda linked to cooling events in the north atlantic region north atlantic climate archives provide evidence for increased storm activity during the little ice age 150 to 600 calibrated years cal years b p and centered at 1700 and 3000 cal years b p typically in centennial scale sedimentary records meteorological tropical versus extratropical storms and climate forcings of this signal remain poorly understood although variability in the north atlantic oscillation nao or atlantic meridional overturning circulation amoc are frequently hypothesized to be involved here we present records of late holocene storminess and coastal temperature change from a bermudian submarine cave that is hydrographically circulated with the coastal ocean thermal variability in the cave is documented by stable oxygen isotope values of cave benthic foraminifera which document a close linkage between regional temperature change and nao phasing during the late holocene however erosion of terrestrial sediment into the submarine cave provides a storminess signal that correlates with higher latitude storminess archives and broader north atlantic cooling events understanding the driver of this storminess signal will require higher resolution storm records to disentangle the contribution of tropical versus extratropical cyclones and a better understanding of cyclone activity during hemispheric cooling periods most importantly however the signal in bermuda appears more closely correlated with proxy based evidence for subtle amoc reductions than nao phasing

hydrogeology of the south eastern yucatan peninsula new insights from water level measurements geochemistry geophysics and remote sensing summary the yucatan peninsula is one of the world s largest karstic aquifer systems it is the sole freshwater source for human users and ecosystems the region hosts internationally important groundwater dependent ecosystems gdes in the 5280 km2 sian ka an biosphere reserve the gdes are threatened by increasing groundwater abstractions and risks of pollution hydrogeological exploration work is needed as basis for sound groundwater management a multidisciplinary approach was used to study this data scarce region geochemical data and phreatic surface measurements showed distinct hydrogeological units in the groundwater catchment of sian ka an the hilly southwestern areas had a low hydraulic permeability likely caused by a geology containing gypsum whereas the transition zone and flat areas in the east and north had a high permeability in the latter areas the fresh groundwater could be described by a dupuit ghyben herzberg lens geophysical borehole logging and time domain electromagnetic soundings identified a shallow low resistive and high gamma radiation layer present throughout the hilly area and transition zone its thickness was 3 8 m apparent conductivity was 200 800 ms m and natural gamma radiation about 80 counts pr second the layer is proposed to be ejecta from the chicxulub impact cretaceous paleogene boundary spatial estimates of recharge were calculated from modis imagery using the triangle method average recharge constituted 17 of mean annual precipitation in the study area recharge was greatest in the hilly area and towards valladolid near the coast average actual evapotranspiration exceeded annual precipitation the multidisciplinary approach used in this study is applicable to other catchment scale studies

continuous inflow of seawater and outflow of brackish water in the substratum of the karstic island of cephalonia greece abstract there is massive continuous inflow of seawater at a place on the coast of the karstic island of cephalonia in the mediterranean this current reappears at the coast on the other side of the island this is extremely astonishing when it is considered that for water sea level represents minimum potential in the earth s gravitational field the nature of the energy which causes the phenomenon has been the subject of numerous as yet unconfirmed hypotheses on the part of numerous authors this study proposes a new explanation connected with the existence of a marine current which creates a hydraulic gradient between the two sides of the island but with inflow being maintained by density flow this is made possible by a deep karstic conduit created during the cenozoic period and which runs in the same direction as the marine current

natural causes of changes in marine environment mercury speciation and distribution in anchialine caves abstract mercury speciation and distribution were assessed for the first time from the water sediment rock soil and air of anchialine caves we evaluated the origin and distribution of four mercury species total thg reactive rhg dissolved gaseous mercury dgm and monomethylmercury mehg in water from bjejajka cave bjejajka and lenga pit lenga in the croatian adriatic sea from 2006 to 2011 concentrations of all mercury species were elevated at both sites compared to adjacent seawater which had concentration range of 0 5 2 4 ng l 1 for thg 0 06 0 2 ng l 1 for rhg 0 02 0 07 ng l 1 for dgm and 0 01 0 02 ng l 1 for mehg in bjejajka the maximum thg concentration 350 ng l 1 in the middle layer 3 7 m of the 12 m deep stratified water column was up to 3 orders of magnitude greater than in adjacent seawater during and after the rainy sampling periods in january 2009 and 2010 mixing of bjejajka water column resulted in elevated concentrations up to 3700 ng l 1 of thg 4 orders of magnitude higher compared to values in nearby seawater in the bottom water layer mehg concentrations in the bjejajka water column were also considerably elevated 0 7 6 3 ng l 1 compared to the surrounding seawater 0 01 0 02 ng l 1 the vertical distribution of mehg concentrations followed that of thg however the ratio of mehg thg above the bjejajka halocline was drastically higher up to 57 compared to mehg proportion 1 2 below the halocline which was similar to that of surface seawater in sediment of bjejajka thg concentrations were up to 3 3 mg kg 1 considerably above concentrations in unpolluted adriatic marine sediment 0 1 0 3 mg kg 1 the highest thg amounts found in soil and air were inside and in close proximity to bjejajka while thg in rock 0 01 mg kg 1 were below reported values for unaltered carbonates laboratory experiments indicate that bat guano was the major source of elevated mercury concentrations in the water column and sediment of bjejajka concentrations of thg in bat guano were up to 0 45 mg kg 1 above the range of thg concentrations found in unpolluted marine sediment seventy two days after the addition of bat guano in solution a 100 fold higher hg concentration was observed from 2 5 up to 252 ng l 1 in lenga bat guano was not spotted and thg water and sediment concentrations were drastically lower mostly below 7 ng l 1 and 0 8 mg kg 1 respectively

regional response of the coastal aquifer to hurricane ingrid and sedimentation flux in the yax chen cave system ox bel ha yucatan mexico abstract coastal karst aquifers are an important source of potable water which can be affected by external forcing on various temporal and spatial scales e g sea level but there is a lack of long term data to understand their response sediment cores and their proxy records have been used in lakes and oceans to assess past environmental change but haven t been extensively applied to anchialine caves where there is less known about the physical biological and chemical processes affecting sedimentation over fifty sediment traps were placed in yax chen which is part of the ox bel ha cave system near tulum mexico and four water level sensors were placed in two additional cave systems ponderosa sac actun for comparative water table fluctuations data collected over the past three years 2011 2013 captured seasonal and spatial sediment flux including the effect of an intense rainfall associated with hurricane ingrid september 18 2013 the data indicates that sediment deposition was controlled by cenote size and the presence of mangrove areas upstream of cenote gemini had negligible sediment accumulation as there were few cenotes and the terrain is dominated by lowland tropical forest while areas downstream from cenote gemini were dominated by mangrove forests and larger cenotes which resulted in higher sediment accumulation rates 0 014 vs 0 22 mg cm 2 day bi annual sedimentation rates in 2013 2014 were higher in the months after the rainy season 0 2 vs 0 5 mg cm 2 day indicating that cenote productivity was likely controlling sedimentation mangrove areas with their peat accumulations occlude the porous karst causing funneling of nutrient rich rainwater into the sunlit cenotes enhancing primary productivity and sedimentation in downstream areas hurricane ingrid had little effect on the yearly sediment rate even though water table fluctuations were high 0 7 m compared to the yearly values 0 3 m this likely is due to water bypassing the cenotes with little residence time to enhance productivity and sedimentation in downstream areas

salt intrusion at a submarine spring in a fringing reef lagoon variations in discharge and turbulent kinetic energy tke were studied at a point source submarine groundwater discharge sgd within a fringing reef lagoon from quadrature neap to syzygy spring tides the principal factors affecting discharge and tke variations were tides and waves field data indicated discharge and tke varied with high and low tides and with quadrature and syzygy maximum discharge and tke values were observed during low tides when the hydrostatic pressure over the jet was minimal while the lowest discharge and tke values were found at high tides syzygy tides produced consistent saltwater intrusion during high tides while quadrature tides produced the greatest tke values in general as the discharge intensified during low tides jet temperatures decreased suggesting that waters originated further within the aquifer at the same time jet salinities increased suggesting a mixing of aquifer and seawater to reconcile these two seemingly opposing views it is proposed that the jet conduit is connected to a stratified chamber with seawater below brackish water the greatest subtidal discharge occurred during quadrature tides syzygy produced low subtidal discharge driven by flow reversals flow into the aquifer observed throughout syzygy high tides in conjunction with the peak wave setup 5 cm observed during a storm while tides were the primary driving force of the discharge waves played a nonnegligible role wave effects on the discharge were most evident during syzygy high tides combined with a storm when the subtidal spring discharge was weakest and salt intrusion developed

foraminifera and testate amoebae thecamoebians in an anchialine cave surface distributions from aktun ha carwash cave system mexico surface sediment samples from aktun ha carwash cave system mexico were analyzed for microfossils carbonate isotopes and organic matter content saline water flooded the cave during the sangamon interglacial highstand 124 119 kyr hosting a marine assemblage dominated by saline foraminifera bolivina sp 73 and elphidium sp 11 with a mean 13c 25 5 and a mean 18o 22 7 this assemblage was found distal to sinkholes 75 m upstream 150 m downstream and in yellow orange sediment mean total organic carbon toc 3 6 late pleistocene 95 15 kyr sea level fall reestablished vadose conditions in the cave allowing for localized speleothem flowstone to seal in the marine assemblage holocene sea level rise completely reflooded the cave with freshwater by 6 5 kyr providing a suitable habitat for a freshwater assemblage of living testate amoebae centropyxis aculeata 38 arcella vulgaris 10 and the foraminifer ammonia tepida var juvenile 35 with a mean 13c 210 8 and a mean 18o 24 9 on the ostracod cytheridella ilosvayi this assemblage was found proximal to sinkholes 75 m upstream 150 m downstream and in black to brown sediment mean toc 17 5 foraminifera and testate amoebae colonize aquatic cave environments respond to physicochemical conditions in the cave similarly to other coastal settings and thereby provide promise for the application of protists as proxies in flooded caves

trace element geochemistry of groundwater in a karst subterranean estuary yucatan peninsula mexico ndseg nsf chemical oceanography program oce 0751525 coastal ocean institute ocean and climate change institute at woods hole oceanographic institution

petrogenesis of syenites at a rifted continental margin origin contamination and interaction of alkaline mafic and felsic magmas in the astrophyllite bay complex east greenland the astrophyllite bay complex in east greenland part of the palaeogene north atlantic igneous province consists of an alkaline diorite plug with detached trachyandesitic pillows surrounded by co magmatic syenite that was emplaced into archaean basement the diorite intrusion has yielded a 47 11 0 68 ma rb sr isochron age saw cut profiles through pillow syenite gneiss sections have been taken to resolve close spatial elemental and isotopic sr nd hf pb o variations the diorite and syenite formed from alkaline basaltic mantle derived melts with complex histories of prolonged assimilation and fractional crystallisation each evolved to different extents in separate magma chambers during the establishment of new plumbing systems in the kangerlussuaq area the diorite is dominated by lower crustal granulite facies contamination whereas the syenite shows evidence for greater degrees of upper crustal amphibolite facies contamination indicating stalling and fractionation of magmas at different levels within the crust the syenite and diorite magmas were subsequently emplaced as separate pulses into the basement gneisses at astrophyllite bay giving rise to superimposed local contamination trends between pillow syenite and syenite gneiss respectively

saltwater wedge variation in a non anthropogenic coastal karst aquifer influenced by a strong tidal range burren ireland summary spatial and temporal changes in saltwater wedges in coastal karst aquifers are still poorly understood largely due to complex mixing processes in these heterogeneous environments but also due to anthropogenic forcing such as pumping which commonly affect natural variations in wedges the purpose of this study was first to characterize the hydrodynamic functioning of a karst aquifer in an oceanic temperate climate with little anthropogenic pressure but strongly influenced by a high tidal range and second to evaluate the extent and movements of a saltwater wedge influenced by both the tide and the natural recharge of the aquifer variations in specific conductivity combined with water chemistry results from six boreholes and two lakes located in the bell harbour catchment western ireland enabled us to assess the extent of the intrusion of the saltwater wedge into the aquifer as a function of both karst recharge and tidal movements at high low and neap spring tidal cycles the marked spatial disparity of the saltwater wedge was analysed as a function of both the hydrodynamic and the structural properties of the karst aquifer results showed that the extent of the saltwater wedge depended not only on the intrinsic properties of the aquifer but also on the relative influence of the recharge and the tide on groundwater levels which have opposite effects recharge in the burren area throughout the year is large enough to prevent saltwater intruding more than about one kilometre from the shore a strong tidal amplitude seems to be the motor of sudden saltwater intrusion observed in the aquifer near the shore while the position of the groundwater level seems to influence the intensity of the salinity increase competition between recharge and the tide thus controls the seawater inputs hence explaining temporal and spatial changes in the saltwater wedge in this coastal karst aquifer