conduit enlargement in an eogenetic karst aquifer summary most concepts of conduit development have focused on telogenetic karst aquifers where low matrix permeability focuses flow and dissolution along joints fractures and bedding planes however conduits also exist in eogenetic karst aquifers despite high matrix permeability which accounts for a significant component of flow this study investigates dissolution within a 6 km long conduit system in the eogenetic upper floridan aquifer of north central florida that begins with a continuous source of allogenic recharge at the santa fe river sink and discharges from a first magnitude spring at the santa fe river rise three sources of water to the conduit include the allogenic recharge diffuse recharge through epikarst and mineralized water upwelling from depth results of sampling and inverse modeling using phreeqc suggest that dissolution within the conduit is episodic occurring only during 30 of 16 sampling times between march 2003 and april 2007 during low flow conditions carbonate saturated water flows from the matrix to the conduit restricting contact between undersaturated allogenic water with the conduit wall when gradients reverse during high flow conditions undersaturated allogenic recharge enters the matrix during these limited periods estimates of dissolution within the conduit suggest wall retreat averages about 4 10 6 m day in agreement with upper estimates of maximum wall retreat for telogenetic karst because dissolution is episodic time averaged dissolution rates in the sink rise system results in a wall retreat rate of about 7 10 7 m day which is at the lower end of wall retreat for telogenetic karst because of the high permeability matrix conduits in eogenetic karst thus enlarge not just at the walls of fractures or pre existing conduits such as those in telogenetic karst but also may produce a friable halo surrounding the conduits that may be removed by additional mechanical processes these observations stress the importance of matrix permeability in eogenetic karst and suggest new concepts may be necessary to describe how conduits develop within these porous rocks

the relationship between current and paleo groundwater base levels abstract base levels are basically divided into two categories oceanic and marine base levels and continental terminal endorheic ones the marine domain serves as the ultimate base level for both surface and groundwater drainage systems continental inland depressions very often serve as terminal endorheic base levels to both surface drainage and groundwater systems many of the current both marine and inland base levels served also in the past as paleo base levels fluctuations of base level elevations affect the adjoined groundwater system in several ways such as changes in groundwater levels location of divides depths of fresh saline water interfaces and the amount of flow to the base levels this paper provides examples from many different parts of the world that describe the relationship between current and paleo base levels the examples include marine base levels as well as inland endorheic ones both currently above and below sea level close to and distant from the sea

age and correlation of emerged pliocene and pleistocene deposits u s atlantic coastal plain abstract paleontologic and paleomagnetic investigations were conducted on several hundred pliocene and pleistocene marine samples from five regions of the emerged atlantic coastal plain 1 the delmarva peninsula 2 eastern virginia 3 central and northern north carolina 4 southern north carolina and northeastern south carolina and 5 the charleston area south carolina molluscan and ostracode interval and assemblage zonations which are the primary means of regional correlation have been calibrated using planktic biochronologic paleomagnetic radiometric and amino acid recemization data these multiple dating criteria were used to determine the age and where possible the duration of marine transgressive regressive sequences a correlation chart illustrates the age relationships of 27 formations from five regions one important conclusion is some of the yorktown formation of virginia and north carolina including the duplin formation and some of the raysor of south carolina are late pliocene in age the late pliocene chowan river formation of north carolina is older than the early pleistocene waccamaw formation of south carolina which in turn may be older than the james city formation of north carolina during the last 1 0 million years multiple marine transgressions occurred in each region but the age of these middle and late pleistocene formations often may differ from one area to the next a significant result of the study is the evidence for the lack of time equivalence of formations in the five different regions that is the sequence of marine transgressions in one region does not necessarily correspond to that in another this appears to be the result of differing subsidence and uplift histories the patchiness of the depositional record and the limitations of the dating techniques in light of the rapidity and frequency of sea level fluctuations

uplifted flank margin caves in telogenetic limestones in the gulf of orosei central east sardinia italy and their palaeogeographic significance abstract this work reports the results of geomorphological observations carried out in the coastal fico cave and surrounding areas baunei central east sardinia in the gulf of orosei a tidal notch generally believed to be of eemian mis 5e age is barely visible at 8 5 above present sea level asl some metres below the main entrance of the cave old cave passages now partially opened by cliff retreat and parallel to the coastline are clearly visible at around 14 m asl and correspond to the main level of fico cave two more notches are located higher at 22 and 50 m asl fico cave itself is composed of at least 6 clearly distinguished more or less horizontal levels 10 m below present sea level bsl and 14 22 40 50 and 63 m asl independent of the stratal dip arguing for a sea level and hence fresh water lens control cave passages develop along main fractures more or less parallel to the coastline and never extend landward for more than 150 m mostly ending blindly or diminishing in their dimensions progressively landward most passages only contain clay deposits lacking fluvial or marine sediments or typical fluvial erosion morphologies i e scallops it is suggested from this body of evidence that fico cave was formed in the coastal mixing zone along major discontinuities during several quaternary interglacial periods when sea level was high and relatively stable for enough time to develop large dissolutional voids the geomorphological observations indicate the main 14 m asl level of the cave to have formed during mis 9 and was heavily reworked during mis 5 while the higher levels are relative to older interglacial highstands that occurred between 1 ma and 325 ka the small active branch developed below present sea level has formed during mis 7 225 ka these observations shed new light on the position of the mis 5e highstand markers in this area of the coast much higher than previously thought

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

fuzzy based spatial modeling approach to predict island karst distribution a conceptual model previous studies have shown that island karst could successfully indicate paleoclimate change in the quaternary period however because of the relative inaccessibility of carbonate islands and their rural settings the exploration of island karst features has been limited to enhance future research remote sensing and geospatial modeling were used in this study to improve the island karst exploration record the results showed that fuzzy based spatial modeling could successfully predict the island karst distributions on a simple carbonate island the accuracy of the model was above 90 this method could apply to other coastal karst regions and carbonate islands in the future

reconstructing past climates using carbon isotopes from fulvic acids in cave sediments little is known about the potential of organic substances found within cave sediments to provide useful reconstructions of past climatic changes here we present a study of the carbon isotopes of fulvic acids extracted from sediments from a cave in west central florida fulvic acids are the most contemporaneous representation of soil humic substances derived from vegetation growing above the cave radiocarbon dating of these sediments constrains their depositional period to be late holocene the range of the fulvic acid 13c record shows the dominance of c3 vegetation during this period but with changes in abundance and the shifting presence of c4 plants the 13c values record both the little ice age and medieval climate anomaly which produce drier and wetter conditions for florida respectively our conclusion that the stable carbon isotopic values of the cave sediment record as a proxy for vegetation change as driven by variability in precipitation is strongly supported by a comparison with the 13c and 18o values of two uranium series dated speleothems from this part of florida with both being proxies for precipitation change

evolution of isolated caves in porous limestone by mixing of phreatic water and surface water at the water table of unconfined aquifers a model approach summary when water from the surface e g from a lake flows through porous carbonate rocks down along some region with high hydraulic conductivity and encounters the water table of a phreatic aquifer both waters mix by diffusion along their boundary in a carbonate aquifer where both surface and phreatic waters are saturated with respect to calcite mixing corrosion causes renewed dissolution of the carbonate rock in the diffusional mixing zone extending from the boundary separating the phreatic water from the surface water encountering it a numerical model is presented from which the initial change of porosity in such a diffusional mixing zone is obtained the initial change of porosity d dt 0 is proportional to m x y 2 and d2 ceq m dm2 m x y is the spatial distribution of the mixing ratio m vsur vsur vphr and the vs assign the corresponding volumes of surface and phreatic water d2 ceq dm2 is the second derivative of ceq the renewed dissolution capacity of the mixed solution it has been calculated for three geochemical scenarios with differing co2 concentrations of surface and phreatic water by use of phreeqc 2 the spatial distribution m x y is obtained by using modflow and mt3dms in a modeling domain with constant hydraulic conductivity for various flow velocities of the phreatic aquifer from the results the time scale of cave evolution is estimated passages of dimensions of about one meter in width and several 10 cm in height extending in length along the border line where surface and phreatic water meet can be created in time scales of 10 000 years these caves are horizontal with blind ending passages and resemble closely to the isolated caves observed in central west florida for more realistic modeling we have used a geostatistical local distribution of hydraulic conductivities in the modeling domain for a correlation length of 1 of the length of modeling domain the spatial distribution extends deeper into the flow direction when the correlation length is increased by a factor of 10 flow focusing distorts the diffusional mixing zone and enhances the creation of porosity

coastal and inland karst morphologies driven by sea level stands a gis based method for their evaluation sea level is the base level for groundwater circulation in coastal aquifers the evolution of karst surface landforms and subsurface drainage systems in these aquifers has been conditioned in geological time by tectonics and glacio eustatic sea level changes present morpho structural settings and the type distribution of karst surface and subsurface forms have developed in different carbonate formations according to differences in lithology climate and exposure time all driving the intensity of morphologic and karst processes the repeated and significant changes of groundwater level linked to sea level changes have had the most important role in driving the continuous evolution of karstic drainage systems and has resulted in most cases in a multiphase karst this study aims at defining a general method for identifying in karst coastal settings the elevations of flat or low topographic gradient surfaces using morphometric analysis of digital elevation models dems and geographical information systems giss and their comparison with elevations of distinctive karstic levels passages lateral solution cavities observed in vertical shafts and horizontal caves of the elevations of flat or low topographic gradient surfaces only those agreeing within 10 m or 20 m with elevation ranges marked by the high frequency of distinctive karst levels were considered as representative of the more probable past sea level stands the method is applied to a regional coastal carbonate formation in southern italy by using a 10 m dem and information on 140 complex caves and 85 shafts of the 15 elevations indicated by dem analysis 620 600 470 450 425 385 355 315 270 250 205 180 150 110 and 70 m above sea level a s l 13 match clearly those highlighted by significant frequencies of distinctive karstic levels these elevations are validated by comparison to the elevation of terraces and karst plains indicated in the literature copyright 2012 john wiley sons ltd

heterogeneous distributions of co 2 may be more important for dissolution and karstification in coastal eogenetic limestone than mixing dissolution mixing dissolution a process whereby mixtures of two waters with different chemical compositions drive undersaturation with respect to carbonate minerals is commonly considered to form cavernous macroporosity e g flank margin caves and banana holes in eogenetic karst aquifers on small islands macroporosity commonly originates when focused dissolution forms globular chambers lacking entrances to the surface suggesting that dissolution processes are decoupled from surface hydrology mixing dissolution has been thought to be the primary dissolution process because meteoric water would equilibrate rapidly with calcium carbonate as it infiltrates through matrix porosity and because pco2 was assumed to be homogeneously distributed within the phreatic zone here we report data from two abandoned well fields in an eogenetic karst aquifer on san salvador island bahamas that demonstrate pco2 in the phreatic zone is distributed heterogeneously the pco2 varied from less than log 2 0 to more than log 1 0 atm over distances of less than 30 m generating dissolution in the subsurface where water flows from regions of low to high pco2 and cementation where water flows from regions of high to low pco2 using simple geochemical models we show dissolution caused by heterogeneously distributed pco2 can dissolve 2 5 to 10 times more calcite than the maximum amount possible by mixing of freshwater and seawater dissolution resulting from spatial variability in pco2 forms isolated globular chambers lacking initial entrances to the surface a morphology that is characteristic of flank margin caves and banana holes both of which have entrances that form by erosion or collapse after cave formation our results indicate that heterogeneous pco2 rather than mixing dissolution may be the dominant mechanism for observed spatial distribution of dissolution cementation and macroporosity generation in eogenetic karst aquifers and for landscape development in these settings copyright 2015 john wiley sons ltd

identification of a 15 m wisconsin shoreline on the texas inner continental shelf abstract the maximum sea level position during the middle wisconsin oxygen isotope stage 3 is controversial it being interpreted as anywhere from at or above present day levels to 85 m high resolution seismic lithologic paleontologic and radiocarbon data from the east texas continental shelf were used to map a stage 3 shoreline the shoreline was placed in a regional context with a study of the texas shelf based on seismic profiles core and platform boring descriptions that identifies the stage 3 maximum flooding surface and the stage 2 sequence boundary these surfaces were then traced up dip on the east texas shelf where a shore parallel escarpment was recognized landward of the escarpment the stage 3 maximum flooding surface is amalgamated with the stage 2 sequence boundary therefore the location of the escarpment marks the up dip limit of stage 3 deposits and a stage 3 shoreline lagoonal sediments with in situ brackish water fossils on lap the escarpment seaward of the escarpment remnants of barrier island facies have been preserved as a bank freeport rocks bathymetric high located in 18 m of water the shoreline adjusted for subsidence is located at 15 2 m which is shallower than what oxygen isotope and coral records indicate

magnetic susceptibility zonation of the melilititic riedheim dyke hegau volcanic field germany evidence for multiple magma pulses the olivine melilitic riedheim dyke complex is related to the tertiary alkaline magmatism within the hegau volcanic field magnetic susceptibility measurements and the mineral composition of oxides together with petrographic observations imply two phases of magma intrusion for the emplacement of this dyke the first intrusion forms the eastern and western margins of the dyke section with high magnetic susceptibility values of up to 75 10 3 si which are related to ferrimagnetic mg al cr bearing titanomagnetites with a magnetite component between 0 59 and 0 75 mol a generally lower magnetic susceptibility of up to 45 10 3 si and a significantly lower and homogeneous magnetite component of the titanomagnetites xmt 0 38 mol are recorded for the second intrusion into the central part of the dyke furthermore a dependence of magnetic susceptibility on the amplitude of the ac field was measured which is more pronounced in the second intrusion hd 25 than in the first one 6 hd 10 confirming the magneto mineralogical data secondary pervasive alteration is more pronounced in the first intrusion phase characterised by a very fine grained and glassy matrix that is more receptive to hydrothermal overprint than the well crystallised matrix of the second intrusion localised thermally induced alteration at the intimately fractured contact between the first and second intrusion phase has oxidised the titanomagnetite of the first intrusion phase but did not significantly effect the second intrusion differences between the dyke sections are also documented by the anisotropy of magnetic susceptibility ams which reflects a magmatic flow fabric with long axis of the ams ellipsoids magnetic lineation parallel to the flow direction and short axis normal to the n s trending dyke boundary the orientation of the magnetic fabric for the individual magma pulses is different with a more moderate plunge of the magnetic lineation within both the western 177 57 and eastern parts 181 50 of the first dyke intrusion compared to a nearly vertical orientation in the second central dyke intrusion 180 78 we suggest that the primary crystallisation history of the two intrusion phases caused the magnetic susceptibility zonation in the riedheim dyke complex

quaternary cave levels in peninsular florida abstract the hypothesis that caves in the florida peninsula are tied to quaternary sea levels was proposed by hydrogeologists without data some 40 years ago the hypothesis is a version of glacial control of cave levels which is the logical combination of the water table theory of speleogenesis and the concept that base level positions the water table at the usa type example of glacial control of cave levels mammoth cave in the paleozoic rocks of kentucky the intermediary is base level determined by rivers by hypothesis the intermediary for florida is glacioeustatic sea level this paper presents elevation data that supports this hypothesis recent cave surveys in the air filled caves and spot elevations from archived maps reveal prominent levels of passages centered at 5 12 21 and 30 m above sea level over broad areas they do not follow the large scale structure of the floridan aquifer instead they align with nearby coastal marine terraces identified as modal peaks on frequency plots from various topographic data bases levels matching with the three highest terraces wicomico penholoway and talbott are particularly clear lower levels if they accord with sea level stands are likely composites data from cavities encountered in drilled wells e g bit drops and spot elevations from archived underwater cave maps demonstrate passage levels at depths of 15 30 70 and 90 120 m below the modern water table the depths below water table are similar to the depths below sea level of distant submerged terraces and paleoshoreline features identified using multibeam bathymetric data in the gulf of mexico the cave bit drop and terrace data are all consistent with the concept that quaternary sea level is the fundamental control on the cave scale porosity within the floridan aquifer this conclusion does not rule out the possibility that lithologically favored positions paleokarst features and confining units and mixing zones are also involved in the location of caves levels in this near coastal environment

holocene paleohydrology of little salt spring florida based on ostracod assemblages and stable isotopes abstract ostracod assemblages and the 18o and 13c records of cytheridella ilosvayi provide a 12 000 yr paleohydrological reconstruction of little salt spring a sinkhole lake and underwater archaeological preserve in west central florida the ostracod record documents relative changes in water temperature and hydrologic characteristics of the lacustrine system that are the result of warming air temperatures changes in the relative contributions of input waters shallow vs deep groundwater rainfall patterns and relative sea level rise during the holocene the data indicate that lss was initially supplied by relatively low amounts of direct rainfall and surface runoff as the spring s location was closer to the recharge area and far from the freshwater saltwater interface at about 11 000 yr bp lss became groundwater supported initially by a shallow freshwater aquifer with low 18o composition until 5700 yr bp and after that time by 18o enriched and increasingly mineralized groundwater originating from a deeper carbonate aquifer as the regional water table rose bringing the saltwater interface closer to the location of lss which at this time was becoming a groundwater discharge area the data also shows that the most abrupt and pronounced hydrologic changes occurred during the late holocene with an interval of low 18o values 2 86 between 2700 and 2000 yr bp followed by a stepped increase in 18o composition with maximum values 1 46 between 1100 and 900 yr bp over these periods to the present time the ostracod assemblage is characterized by brackish species cyprideis spp and limnocythere floridensis it is inferred that the interval of decreased isotopic values indicates mixing with saline water during dry climatic conditions while the interval of more enriched isotopic values suggest saltwater intrusion during a period of presumably a sea level highstand although some discrepancies exist between other records from the northern caribbean region and the one from lss with regards to the exact timing for the late holocene drying and subsequent increase in rainfall conditions the differences between the records may be explained by greater continental influences on ocean atmosphere interactions on the florida peninsula a highly complex groundwater mixing balance in lss and by a better constrained age model in the other records

an isotopic calibration study of precipitation cave dripwater and climate in west central florida a calibration study of oxygen and hydrogen isotopic composition from precipitation and cave dripwater was conducted in west central florida at legend cave during 2007 2008 this study was performed to better understand how modern precipitation patterns can be discerned through examination of cave dripwater and speleothem calcite for paleoclimate reconstruction the amount effect was shown to be a dominant control on the oxygen isotopic composition of precipitation for the study area a meteoric water line with a slope of 6 7 suggests evaporative effects occur either during precipitation or subsequent hydrological processes however 18o values of cave dripwater averaged near the mean annual amount weighted average of precipitation suggesting that the isotopic composition of dripwater tracks the long term average of rainfall an observed weak seasonal influence occurred in the d excess values with summer precipitation being more enriched due to increased evaporative effects comparison of precipitation 18o values to synoptic weather data shows the dominant amount effect influence occurs due to strong convective storms producing highly 18o depleted rainfall at greater amounts during the year constant 18o values of the dripwater indicate that paleoclimate reconstructions using speleothems from this area would record changes in annual to interannual shifts in precipitation amount above the cave copyright 2011 john wiley sons ltd

sulfuric acid speleogenesis of carlsbad cavern and its relationship to hydrocarbons delaware basin new mexico and texas sulfur isotope data and ph dependence of the mineral endellite support the hypothesis that carlsbad cavern and other caves in the guadalupe mountains were dissolved primarily by sulfuric acid rather than by carbonic acid floor gypsum deposits up to 10 m thick and native sulfur in the caves are significantly enriched in 32 s isotope 34 s values as low as 25 8 per mil cdt indicate that the cave sulfur and gypsum are the end products of microbial reactions associated with hydrocarbons a model for a genetic connection between hydrocarbons in the basin and caves in the guadalupe mountains is proposed as the guadalupe mountains were uplifted during the late pliocene pleistocene oil and gas moved updip in the basin the gas reacted with sulfate anions derived from dissolution of the castile anhydrite to form h 2 s co 2 and castile limestone the hydrogen sulfide rose into the capitan reef along joints forereef carbonate beds or bell canyon siliciclastic beds and there reacted with oxygenated groundwater to form sulfuric acid and carlsbad cavern a sulfuric acid mode of dissolution may be responsible for large scale porosity of some delaware basin reservoirs and for oil field karst reservoirs in other petroleum basins of the world

development of small carbonate banks on the south florida platform margin response to sea level and climate change abstract geophysical and coring data from the dry tortugas tortugas bank and riley s hump on the southwest florida margin reveal the stratigraphic framework and growth history of these carbonate banks the holocene reefs of the dry tortugas and tortugas bank are approximately 14 and 10 m thick respectively and are situated upon pleistocene reefal edifices tortugas bank consists of the oldest holocene corals in the florida keys with earliest coral recruitment occurring at 9 6 cal ka growth curves for the tortugas bank reveal slow growth

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

formation of phreatic caves in an eogenetic karst aquifer by co2 enrichment at lower water tables and subsequent flooding by sea level rise formation of extensive phreatic caves in eogenetic karst aquifers is widely believed to require mixing of fresh and saltwater extensive phreatic caves also occur however in eogenetic karst aquifers where fresh and saltwater do not mix for example in the upper floridan aquifer these caves are thought to have formed in their modern settings by dissolution from sinking streams or by convergence of groundwater flow paths on springs alternatively these caves have been hypothesized to have formed at lower water tables during sea level low stands these hypotheses have not previously been tested against one another analyzing morphological data and water chemistry from caves in the suwannee river basin in north central florida and water chemistry from wells in the central florida carbonate platform indicates that phreatic caves within the suwannee river basin most likely formed at lower water tables during lower sea levels consideration of the hydrological and geochemical constraints posed by the upper floridan aquifer leads to the conclusion that cave formation was most likely driven by dissolution of vadose co2 gas into the groundwater sea level rise and a wetter climate during the mid holocene lifted the water table above the elevation of the caves and placed the caves tens of meters below the modern water table when rising water tables reached the land surface surface streams formed incision of surface streams breached the pre existing caves to form modern springs which provide access to the phreatic caves phreatic caves in the suwannee river basin are thus relict and have no causal relationship with modern surficial drainage systems neither mixing dissolution nor sinking streams are necessary to form laterally extensive phreatic caves in eogenetic karst aquifers dissolution at water tables potentially driven by vadose co2 gas offers an underappreciated mechanism to form cavernous porosity in eogenetic carbonate rocks copyright 2012 john wiley sons ltd

late pleistocene and mid holocene climate change derived from a florida speleothem abstract a stalagmite collected from brooksville ridge cave in west central florida was deposited from 30 to 20 kyr bp encompassing heinrich event 2 h2 and from 5 to 4 kyr bp the later part of the mid holocene the h2 event in the speleothem occurs at 24 kyr bp which is temporally similar to its timing in other paleoclimate reconstructions however the oxygen and carbon isotope values indicate the climate in florida was relatively warm and wet for a glacial period rather than extremely cool and dry as seen in other regions the higher temperatures and increased precipitation compared to the preceding climate state produced a shift towards enhanced vegetation growth dense forest during this period one possible cause is the faltering of the north atlantic thermohaline circulation due to increased glacial meltwater input thereby preventing heat transfer via the gulf stream from the tropics to the northerly latitudes this change in the circulation would lead to warmer gulf of mexico and subtropical atlantic sea surface temperatures ssts these higher ssts would promote an increase in convective thunderstorm activity due to higher evaporation rates however to give this shift some paleoclimate perspective the average mid holocene speleothem oxygen isotope values were more depleted by 1 indicating even warmer temperatures and higher precipitation amounts compared to the glacial period additionally the carbon isotopes show a 3 shift towards more negative values indicating a more heavily forested west central florida the variability within both the mid holocene and late pleistocene data support the possibility of atmospheric teleconnections between the tropics subtropics and northerly latitudes contributing to shorter term shifts in precipitation amount superimposed on the larger scale glacial interglacial isotopic composition of the speleothem

the use of high resolution elevation histograms for mapping submerged terraces tests from the eastern tyrrhenian sea and the eastern atlantic ocean abstract histogram plots can be used as a cost and time efficient tool to detect horizontal or gently dipping geomorphic surfaces within a background regional topography one of the main classes of these surfaces is typified by terraces formed during marine still stands this contribution uses elevation histogram plots as morphometric indicators for detecting the possible existence of concealed terrace orders in digital elevation models dems derived by the processing of bathymetric data the approach is particularly useful when dealing with submerged terraces and platforms because of the obvious difficulties in mapping those surfaces the advantage of using this indicator consists in the rapid identification of dem recurrent bathymetric values this tool is most powerful when dealing with shortly developed terraces and or multiple terrace orders whose detection could have been missed by direct observation two case studies characterized by the presence of a single terracing event are tested the southern slope of the ischia island and the top of the palinuro seamount both located in the eastern tyrrhenian sea margin elevation histograms are used for terrace order computation in a more complex setting the gorringe bank located offshore sw portugal in the eastern atlantic ocean the results show that a joint use of elevation histogram computation and geomorphologic analysis can be particularly efficient in the study of planar surfaces

detrital cave sediments record late quaternary hydrologic and climatic variability in northwestern florida usa abstract detrital sediment in florida s usa submerged cave systems may preserve records of regional climate and hydrologic variability however the basic sedimentology mineralogy stratigraphic variability and emplacement history of the successions in florida s submerged caves remains poorly understood here we present stratigraphic mineralogical and elemental data on sediment cores from two phreatic cave systems in northwestern florida usa on the dougherty karst plain hole in the wall cave hitw and twin cave water flowing through these caves is subsurface flow in the apalachicola river drainage basin and the caves are located just downstream from jackson blue 1st magnitude spring 2 8 m3 s 1 discharge sedimentation in these caves is dominated by three primary sedimentary styles i ferromanganese deposits dominate the basal recovered stratigraphy which pass upsection into ii poorly sorted carbonate sediment and finally into iii fine grained organic matter gyttja deposits resolving the emplacement history of the lower stratigraphic units was hampered by a lack of suitable material for radiocarbon dating but the upper organic rich deposits have a punctuated depositional history beginning in the earliest holocene for example gyttja primarily accumulated in hitw and twin caves from 5500 to 3500 cal yr bp which coincides with regional evidence for water table rise of the upper floridian aquifer associated with relative sea level rise in the gulf of mexico and evidence for invigorated drainage through the apalachicola river drainage basin gyttja sediments were also deposited in one of the caves during the bolling allerod climate oscillation biologically these results indicate that some floridian aquatic cave stygobitic ecosystems presently receive minimal organic matter supply in comparison to prehistoric intervals the pre holocene poorly sorted carbonate sediment contains abundant invertebrate fossils and likely documents a period of enhanced limestone dissolution and cave formation speleogenesis during lower paleo water levels further work is still required to a determine whether precipitation of the ferromanganese deposits is inorganically or biologically mediated b temporally constrain the emplacement history of the primary sedimentary styles and c determine the full geographic extent of these sedimentary signals however these preliminary observations suggest that sedimentation in the inland underwater caves of northwestern florida is related to quaternary scale hydrographic variability in the apalachicola river drainage basin in response to broader ocean and atmospheric forcing

delineation of macroporous zones in the unsaturated portion of the miami limestone using ground penetrating radar miami dade county florida summary the atlantic coastal ridge in dade county is an ooid shoal formed during the late pleistocene the ridge is composed of the eogenetic karst miami limestone characterized by a heterogeneous distribution of porosity that can manifest as large touching vug macroporous features with sizes in the meters and tens of meters direct evidence for the presence of such large dissolution features is only visible when exposed to the surface which may be problematic in urbanized areas for that reason it is critical to detect any potential precursors for such dissolution features at the subsurface level the purpose of this study was to investigate the ability of ground penetrating radar to detect areas of macroporosity by quantifying changes in electromagnetic wave velocity and relate them to changes in porosity after application of the complex refractive index model crim in order to constrain volumetric water content vwc in the crim an experiment using miami limestone samples was designed to understand 1 the range of typical vwcs and 2 the effect of capillary fringe on water table elevation the results show several areas where increases in em wave travel time associated with contrasts in porosity exceeding 40 cannot be explained by changes in vwcs typically shown in the miami limestone this study may help understand porosity variability in the unsaturated part of the miami limestone and if expanded to larger scales may aid groundwater flow models by better capturing distributions of macroporous areas that may contribute to direct recharge of the biscayne aquifer

strange bedfellows a deep water hermatypic coral reef superimposed on a drowned barrier island southern pulley ridge sw florida platform margin abstract the southeastern component of a subtle ridge feature extending over 200 km along the western ramped margin of the south florida platform known as pulley ridge is composed largely of a non reefal coastal marine deposit modern biostromal reef growth caps southern pulley ridge spr making it the deepest hermatypic reef known in american waters subsurface ridge strata are layered lithified and display a barrier island geomorphology the deep water reef community is dominated by platy scleractinian corals leafy green algae and coralline algae up to 60 live coral cover is observed in 60 75 m of water although only 1 2 of surface light is available to the reef community vertical reef accumulation is thin and did not accompany initial ridge submergence during the most recent sea level rise the delayed onset of reef growth likely resulted from several factors influencing gulf waters during early stages of the last deglaciation 14 kyr b p including cold low salinity waters derived from discrete meltwater pulses high frequency sea level fluctuations and the absence of modern oceanic circulation patterns currently reef growth is supported by the loop current the prevailing western boundary current that impinges upon the southwest florida platform providing warm clear low nutrient waters to spr the rare discovery of a preserved non reefal lowstand shoreline capped by rich hermatypic deep reef growth on a tectonically stable continental shelf is significant for both accurate identification of late quaternary sea level position and in better constraining controls on the depth limits of hermatypic reefs and their capacity for adaptation to extremely low light levels

spreading of tracer plumes through confined telogenetic karst aquifers a model summary to calculate spreading of a tracer or contaminant through an aquifer all details of the aquifer e g distribution of hydraulic parameters must be known this is not possible in nature to study the spreading of plumes through karst we have used a digital model of a confined karst aquifer at different stages of early karstification in these models all details such as fracture aperture widths their lengths and widths and the hydraulic boundary conditions are known therefore the flow velocity of water can be calculated in each fracture using this information a particle tracking method is employed to calculate the propagation and spreading of a plume caused by an instantaneous input pulse into selected regions of the aquifer from this information the time dependence of the outflow of particles from any selected region is obtained this function represents the transfer response function for an instantaneous dirac function input two digital karst models are designed in the first homogeneous one the aperture widths of the fractures are statistically distributed but of similar width in the second a coarse percolating net of prominent fractures with larger constant aperture width is embedded into the dense net of narrow fissures propagation of the plumes and the transfer response function are presented at the onset of karstification and at different times of karst evolution if particles are injected at the entrance of evolving karst channels propagating towards the output boundary tracer breakthrough times increase with increasing time of karst evolution until shortly before breakthrough of the karst conduit they drop to half of their maximal value with increasing evolution of the karst aquifer the hydraulic heads are redistributed and regions of low hydraulic gradients in the upstream side of the aquifer are created particles injected into fractures which have stopped dissolutional widening of their aperture widths and are located in regions of low gradient are kept in these regions for long times in the order of 100 years until they have propagated towards regions of high hydraulic heads where a fan like plume develops along the pathway of steepest gradient

quaternary climates and sea levels of the u s atlantic coastal plain uranium series dating of corals from marine deposits of the u s atlantic coastal plain coupled with paleoclimatic reconstructions based on ostracode marine and pollen continent data document at least five relatively warm intervals during the last 500 000 years on the basis of multiple paleoenvironmental criteria we determined relative sea level positions during the warm intervals relative to present mean sea level were 7 5 meters at 188 000 years ago 7 5 1 5 meters at 120 000 years ago 6 5 3 5 meters at 94 000 years ago and 7 3 meters at 72 000 years ago the composite sea level chronology for the atlantic coastal plain is inconsistent with independent estimates of eustatic sea level positions during interglacial intervals of the last 200 000 years hydroisostatic adjustment from glacial interglacial sea level fluctuations lithospheric flexure and isostatic uplift from sediment unloading due to erosion provide possible mechanisms to account for the discrepancies alternatively current eustatic sea level estimates for the middle and late quaternary may require revision

origin of the epeirogenic uplift of pliocene pleistocene beach ridges in florida and development of the florida karst marine fossils of pleistocene age are known to occur in beach ridges near the border of northern florida and southern georgia at elevations of between 42 and 49 m above mean sea level no evidence exists for a massive melt off of glacial ice which would be required to raise sea level to these elevations florida therefore must have been uplifted epeirogenically during the pleistocene measurement of dissolved solids in florida9s springs demonstrates that the karst area is losing a minimum of 1 2 10 6 m 3 yr of limestone through spring flow the equivalent of 1 m of surficial limestone every 38 000 yr this loss has led to an isostatic uplift of the north central part of the florida peninsula of at least 36 m during pleistocene and holocene time which agrees with observed elevations of marine terraces

tides on the west florida shelf the principal semidiurnal m2 and s2 and diurnal k1 and o1 tidal constituents are described on the west florida continental shelf wfs using a combination of in situ measurements and a three dimensional primitive equation numerical model the measurements are of sea level and currents along the coastline and across the shelf respectively the model extends from west of the mississippi river to the florida keys with an open boundary arcing between it is along this open boundary that the regional model is forced by a global tide model standard barotropic tidal analyses are performed for both the data and the model and quantifiable metrics are provided for comparison based on these comparisons the authors present coamplitude and cophase charts for sea level and velocity hodographs for currents the semidiurnal constituents show marked spatial variability whereas the diurnal constituents are spatially more uniform apalachicola bay is a demarcation point for the semidiurnal tides that are well developed to the southeast along the wfs but are minimal to the west the largest semidiurnal tides are in the florida big bend and florida bay regions with a relative minimum in between just to the south of tampa bay these spatial distributions may be explained on the basis of local geometry a lagrangian stokes drift coherently directed toward the northwest is identified but is of relatively small magnitude when compared with the potential for particle transport by seasonal and synoptic scale forcing bottom stressinduced tidal mixing is examined and estimates are made of the bottom logarithmic layer height by the m2 tidal currents

magnitude and timing of episodic sea level rise during the last deglaciation a succession of elevated ridge deposits on the south florida margin was mapped using high resolution seismic and side scan sonar imaging in water depths ranging from 50 to 124 m the ridges are interpreted to be subtidal shoal complexes and paleoshorelines eolian dune or beach formed during the last sea level transgression oolitic and skeletal grainstones and mixed skeletal peloidal ooid packstones were recovered using a research submersible all of the grains are of shallow water or intertidal origin and both marine and nonmarine cements were identified formation and preservation of these features are attributed to episodic and rapid changes in the rate of the deglacial sea level rise at the onset of the termination 1a 18o excursion this high resolution record of sea level change appears to be related to deglacial processes operating on submillennial time scales and supports increasing evidence of rapid episodic fluctuations in ice volume climate and ocean circulation patterns during glacial interglacial transitions

multiphase breakdown sequence of collapse doline morphogenesis an example from quaternary aeolianites in western australia abstract the morphology of collapse dolines varies according to their maturity and effectiveness of the removal of collapsed material in addition the variable balance between various geomorphic processes due to local geologic hydrologic and climatic settings results in a diverse morphology of collapse dolines and dynamics of their morphogenesis a single generalised proposed sequence of collapse dolines morphogenesis has therefore limited value and more detailed study is needed in terrains which differ in terms of geology hydrology and or climate there is a particularly well exposed karst in stockyard gully national park in the southwestern coastal part of western australia formed in quaternary aeolianites consisting of a dense field of collapse dolines up to 100 m in diameter and on average 10 m deep extensive field work combined with available data of local rock stratigraphy and a comparison to collapse dolines worldwide revealed that the principal processes of collapse doline formation in stockyard gully national park are similar to processes responsible for collapse doline formation worldwide i e collapses above underground chambers and removal of the collapsed material however rock characteristics in the area influence their morphometry due to the mechanical weakness of aeolianite compared to well cemented limestones and a surface calcrete layer with stronger mechanical resistance than underlying aeolianite consequently we propose a new 4 stage multiphase breakdown sequence of collapse doline morphogenesis in aeolianites divided into cave dome calcrete caprock dome young collapse doline and mature collapse doline calcrete caprock dome is stabilised by the uppermost well cemented calcrete and represents a distinctive phase just before the final breakdown to form an actual collapse doline

organic geochemical characteristics of black shales across the ordovician silurian boundary in the holy cross mountains central poland abstract black shales in the holy cross mountains area of poland provide a record of environmental change across the ordovician silurian boundary the changing depositional conditions have generated a variation in organic matter contents above and below the boundary investigating the organic constitution of these black shales has the potential to reveal how their organic matter contents were generated and how suitable these rocks and their lateral equivalents may be for exploitation as shale gas reservoirs one outcrop at the holy cross mountains with a continuous section across the ordovician silurian boundary occurs near the village of bardo stawy in the kielce region and contains sandy silty mudstones as well as grey and black shales organic geochemical analyses of samples at bardo stawy reveals low total organic carbon toc contents for ordovician samples and higher toc values for silurian samples organic biomarkers indicate that the ordovician rocks were deposited in a shallow marine shelf setting while the silurian rocks were deposited in a deeper marine environment the progressive increase in toc from the uppermost ordovician to the lowermost silurian rocks reflects increasingly oxygen poor depositional conditions during the post glacial transgression following the deposition and preservation of organic matter in the ordovician and silurian rocks these rocks were buried and subjected to thermal maturation rock eval and biomarker thermal maturity parameters all indicate that the organic matter is mature and lies within the oil window the ordovician and silurian shales have direct relevance to recent attempts to discover and exploit shale gas reservoirs in poland our data and interpretations suggest that the relatively low toc values

reply to comment on paleokarst on the top of the maokou formation further evidence for domal crustal uplift prior to the emeishan flood volcanism by bin he yi gang xu jun peng guan yu ting zhong lithos 119 1 9 2010 we welcome the comments of ukstins peate et al 2011 on our recent paper he et al 2010a which provide us with an opportunity to extend our discussion on paleokarst between themaokou formation and theemeishanbasalts ukstins peate et al 2011 question the existence of karstic surface of the maokou limestone described by he et al 2010a instead theycontend that the earliest emeishanmagmaswereeruptedat or below sea level in the center of the emeishan large igneous province elip rejecting the pre volcanic domal uplift model proposed by he et al 2003 their arguments are largely basedon their interpretations of field observations such as a sedimentary continuity across the guadalupian lopingian boundary g lb in the center of the elip and b the faulted contact between emeishan basalt andmaokou formation however aswewill showbelow wedispute thesefieldobservations and ukstins peate et al s interpretation of the temporal and spatial frameworks of our and others results in this reply we will clarify using specific examples some key aspects of their questions about the paleokarst on the maokou formation and its relationship to plumeinduced uplift in the elip

paleokarst on the top of the maokou formation further evidence for domal crustal uplift prior to the emeishan flood volcanism abstract the 260 ma emeishan large igneous province elip in southwest china has previously been demonstrated to provide compelling evidence for pre volcanic crustal doming in support of the mantle plume hypothesis however this has been questioned by ukstins peate and bryan 2008 by showing hydrothermal magmatic activity at the daqiao section to solve this argument a detailed characterization of the contact between the emeishan basalts and the maokou formation was carried out the contact is shown to be an unconformity which is characterized by paleokarst on top of the maokou formation including paleokarst relief sinkholes caves tower karst and its corresponding rocks such as kaolinite bauxite and ferruginous duricrust and collapsed breccias etc this paleokarst unconformity was in turn covered or infilled by the emeishan basalts and tuffs suggesting that uplift and erosion occurred prior to the eruption of the elip the extent of erosion of the maokou formation indicates the elip can be divided into three roughly concentric zones the inner intermediate and outer zones the paleokarst features on the top of maokou formation vary across the elip in the inner zone a likely sinkhole and an incision valley with 450 m relief in height are found in the intermediate zone various paleokarst landforms such as karst relief sinkholes and tower karsts are well developed some sinkholes that developed in the qixia formation below the maokou formation imply that the paleorelief is more than 350 m in height in the outer zone the paleokarstic surface is a paleo weathering layer with minor karstification and development of caves at 10 50 m this spatial variation of the paleokarst reflects variation of uplift height across the elip the extent of minimal uplift is estimated to be at least 450 m in the inner zone 350 m in the intermediate zone whereas uplift is minor tens 50 m in the outer zone the magnitude and shape of the uplift is roughly consistent with that predicted by mantle plume models the paleokarst was formed after the deposition of the maokou formation and the eruption of the emeishan basalts at the end guadalupian and indicates a short duration of uplift thus this study lends further support to domal uplift prior to the emeishan flood volcanism but also to the mantle plume initiation model for the generation of the elip

pliocene pleistocene incision of the green river kentucky determined from radioactive decay of cosmogenic 26al and 10be in mammoth cave sediments cosmogenic 26al and 10be in sediments washed into mammoth cave kentucky record the history of 3 5 m y of water table position governed by incision and aggradation of the green river a tributary of the ohio river upper levels of the cave formed during a period of slow river incision and were later filled with sediment due to river aggradation at 2 3 2 4 ma a brief surge of river incision ca 2 ma was followed by river stability and cave passage formation at a lower level rapid incision through 15 m of bedrock ca 1 5 ma was prompted by repositioning of the ohio river to its present course along an ice sheet margin renewed incision ca 1 2 ma and aggradation at 0 7 0 8 ma correlate with major ice advances in the ohio river basin measurements of 26al and 10be also indicate that sandstone capped uplands have maintained slow erosion rates of 2 7 m m y for the past 3 5 m y despite accelerated pleistocene river incision rates of 30 m m y

discussion on the article coastal and inland karst morphologies driven by sea level stands a gis based method for their evaluation by canora f fidelibus d and spilotro g comments are presented on the article by canora et al 2012 dealing with karst morphologies driven by sea level stands in the murge plateau of apulia southern italy our comments start from cave levels that are considered in the cited article as a proof of sea level stands we argue that the presence of sub horizontal passages in cave systems is not a sufficient condition for correlating them with hypothetical past sea level stands such a correlation must be based upon identification of speleogenetic features within the karst systems and or geological field data the problems encountered when using cave surveys for scientific research and their low reliability especially in the case of old surveys are then treated since they represent a crucial point in the paper object of this discussion eventually we present some final consideration on cave levels and terraces and on the specific case study pointing out once again to the need in including geological field data to correctly find a correspondance between flat landforms and sea level fluctuations our main conclusion is that field data and information on speleogenesis of the underground karst landforms cannot be disregarded in a study that claims to deal with the influence of sea level changes on caves copyright 2013 john wiley sons ltd

a 50 000 year record of climate oscillations from florida and its temporal correlation with the heinrich events oscillations of pinus pine pollen in a 50 000 year sequence from lake tulane florida indicate that there were major vegetation shifts during the last glacial cycle episodes of abundant pinus populations indicate a climate that was more wet than intervening phases dominated by quercus oak and ambrosia type ragweed and marsh elder the pinus episodes seem to be temporally correlated with the north atlantic heinrich events which were massive periodic advances of ice streams from the eastern margin of the laurentide ice sheet possible links between the tulane pinus and heinrich events include hemispheric cooling the influences of mississippi meltwater on sea surface temperatures in the gulf of mexico and the effects of north atlantic thermohaline circulation on currents in the gulf

vadose co2 gas drives dissolution at water tables in eogenetic karst aquifers more than mixing dissolution most models of cave formation in limestone that remains near its depositional environment and has not been deeply buried i e eogenetic limestone invoke dissolution from mixing of waters that have different ionic strengths or have equilibrated with calcite at different pco2 values in eogenetic karst aquifers lacking saline water mixing of vadose and phreatic waters is thought to form caves we show here calcite dissolution in a cave in eogenetic limestone occurred due to increases in vadose co2 gas concentrations and subsequent dissolution of co2 into groundwater not by mixing dissolution we collected high resolution time series measurements 1 year of specific conductivity spc temperature meteorological data and synoptic water chemical composition from a water table cave in central florida briar cave we found spc pco2 and calcite undersaturation increased through late summer when briar cave experienced little ventilation by outside air and decreased through winter when increased ventilation lowered cave co2 g concentrations we hypothesize dissolution occurred when water flowed from aquifer regions with low pco2 into the cave which had elevated pco2 elevated pco2 would be promoted by fractures connecting the soil to the water table simple geochemical models demonstrate that changes in pco2 of less than 1 along flow paths are an order of magnitude more efficient at dissolving limestone than mixing of vadose and phreatic water we conclude that spatially or temporally variable vadose co2 g concentrations are responsible for cave formation because mixing is too slow to generate observed cave sizes in the time available for formation while this study emphasized dissolution gas exchange between the atmosphere and karst aquifer vadose zones that is facilitated by conduits likely exerts important controls on other geochemical processes in limestone critical zones by transporting oxygen deep into vadose zones creating redox boundaries that would not exist in the absence of caves copyright 2014 john wiley sons ltd