drivers of holocene sea level change in the caribbean abstract we present a holocene relative sea level rsl database for the caribbean region 5 n to 25 n and 55 w to 90 w that consists of 499 sea level index points and 238 limiting dates the database was compiled from multiple sea level indicators mangrove peat microbial mats beach rock and acroporid and massive corals we subdivided the database into 20 regions to investigate the influence of tectonics and glacial isostatic adjustment on rsl we account for the local scale processes of sediment compaction and tidal range change using the stratigraphic position overburden thickness of index points and paleotidal modeling respectively we use a spatio temporal empirical hierarchical model to estimate rsl position and its rates of change in the caribbean over 1 ka time slices because of meltwater input the rates of rsl change were highest during the early holocene with a maximum of 10 9 0 6 m ka in suriname and guyana and minimum of 7 4 0 7 m ka in south florida from 12 to 8 ka following complete deglaciation of the laurentide ice sheet lis by 7 ka mid to late holocene rates slowed to

sea level controls sedimentation and environments in coastal caves and sinkholes abstract quaternary climate and sea level research in coastal karst basins caves cenotes sinkholes blueholes etc generally focuses on analyzing isotopes in speleothems or associating cave elevations prior sea level highstands the sediments in coastal karst basins represent an overlooked source of climate and sea level information in the coastal zone but to accurately interpret these sediments first requires an understanding of the forcing mechanisms that emplace them in this study we hypothesize that coastal karst basins transition through vadose littoral anchialine and finally into submarine environments during sea level rise because groundwater and sea level oscillate in near synchrony in the coastal zone causing each environment to deposit a unique sedimentary facies to test this hypothesis the stratigraphy in twelve sediment cores from a bermudian underwater cave green bay cave was investigated and temporally constrained with twenty radiocarbon dates the results indicate that we recovered the first succession spanning the entire holocene from an underwater cave 13 ka to present the sediments were characterized with x radiography fossil remains bulk organic matter organic geochemistry 13corg c n and grain size analysis four distinct facies represent the four depositional environments i vadose facies 7 7 ka calcite rafts lithofacies ii littoral facies 7 7 to 7 3 ka calcite rafts and mud lithofacies iii anchialine facies 7 3 to 1 6 ka slackwater and diamict lithofacies and iv submarine facies

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

foraminifera in elevated bermudian caves provide further evidence for 21 m eustatic sea level during marine isotope stage 11 abstract two hypotheses have been proposed to explain the origin of marine isotope stage mis 11 deposits in small bermudian caves at 21 m above modern sea level 1 a 21 m mis 11 eustatic sea level highstand and 2 a mis 11 mega tsunami event importantly the foraminifera reported in these caves have yet to be critically evaluated within a framework of coastal cave environments after statistically comparing foraminifera in modern bermudian littoral caves and the mis 11 calonectris pocket a 21 m cave to the largest available database of bermudian coastal foraminifera the assemblages found in modern littoral caves and calonectris pocket a cannot be statistically differentiated from lagoons this observation is expected considering littoral caves are simply sheltered extensions of a lagoon environment in the littoral zone where typical coastal processes waves storms homogenize and rework lagoonal reefal and occasional planktic taxa fossil protoconchs of the bermudian cave stygobite caecum caverna were also associated with the foraminifera these results indicate that the mis 11 bermudian caves are fossil littoral caves breached flank margin caves where the total mis 11 microfossil assemblage is preserving a signature of coeval sea level at 21 m brackish foraminifera polysaccammina pseudothurammina and anchialine gastropods 95 300 individuals indicate a brackish anchialine habitat developed in the elevated caves after the prolonged littoral environmental phase the onset of sea level regression following the 21 m highstand would first lower the ancient brackish ghyben herzberg lens

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

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

intrusion related affinity and orogenic gold overprint at the paleoproterozoic bonikro au mo deposit cote d ivoire west african craton the bonikro gold deposit and satellite hire open pits are located at the southern tip of the oume fettekro granite greenstone belt in cote d ivoire country rocks in the region have undergone polyphase deformation and prolonged arc magmatism during the paleoproterozoic eburnean orogeny intrusive host rocks at hire and bonikro have been dated at 2180 6 and 2086 4 ma u pb on zircon respectively these plutonic bodies acted as favourable sites for fluid flow due to their brittle rheological characteristics gold mineralisation at bonikro is hosted by i a sheeted quartz vein array characterised by an au w bi te ag metal association in the cupola of a porphyritic granodiorite and ii an overprinting swarm of fault fill smoky quartz molybdenite veins gold mineralisation at hire is shear hosted and shares a similar relative timing with the latter set of auriferous veins this second phase of gold mineralisation occurred during a period of transcurrent tectonics late in the eburnean tectono magmatic history soon after the cessation of compressional deformation it is responsible for the bulk of gold resources in the region e g bonikro hire agbahou and has been dated at 2074 16 ma re os on molybdenite the integration of structural paragenetic relationships with high precision dating of magmatic and hydrothermal events highlights the superposition of late eburnean orogenic gold mineralisation on an earlier intrusion related gold system linked to the local emplacement of a porphyritic granodiorite at bonikro and illustrates the genetic diversity of paleoproterozoic granitoid hosted gold mineralisation in the west african craton it also further supports that gold mineralisations in the west african craton occurred diachronously throughout the eburnean orogeny through a variety of deposit types including au skarn intrusion related au orogenic au and porphyry cu au

differential dissolution of a pleistocene reef in the ground water mixing zone of coastal yucatan mexico a geochemical explanation is provided for the extensive dissolution observed along the carbonate coast of the yucatan peninsula mexico mixing of fresh ground water with subterranean caribbean seawater generates a highly reactive geochemical zone that enhances aragonite and calcite dissolution and permits neomorphism of aragonite mixing zone dissolution caused by ground water discharge is a major geomorphic process in developing caves coves and crescent shaped beaches along the yucatan coast such dissolution has probably been a significant control on permeability and porosity distribution in carbonate rocks in the geologic record

radiocarbon dating of charcoal from tropical sequences results from the niah great cave sarawak and their broader implications subsamples of charcoal from a number of different excavation contexts at the early modern human homo sapiens site of niah great cave malaysia were accelerator mass spectrometry ams 14c dated samples were prepared using one of a number of different methods untreated control acid base acid aba and acid base wet oxidation with stepped combustion abox sc after bird et al 1999 the results show that for material younger than 25 ka bp there is little difference between the two chemical pretreatment methods and the control for charcoal beyond 25 ka bp however there are differences of up to 4000 a with abox sc ages being consistently older this is argued to be a more effective pretreatment method for decontaminating charcoal samples prior to radiocarbon dating for radiocarbon dating charcoals greater than 25 ka bp the abox sc pretreatment and combustion approach appears to be the most rigorous method for developing a robust chronological framework for tropical sequences and should be more widely applied in contexts where the material being dated is likely to be ancient the new chronology developed for niah cave based on this technique suggests that the earliest human evidence dates back to at least 45 ka bp and may extend significantly earlier than this based on the recent discovery of lithics 50 cm below the earliest dated charcoal copyright 2008 john wiley sons ltd

organic matter sources and lateral sedimentation in a bahamian karst basin sinkhole over the late holocene influence of local vegetation and climate abstract karst basins e g blueholes sinkholes accumulate well preserved sedimentary successions that provide transformative paleoclimatic and paleoenvironmental information however the sedimentary processes within these basins are not yet fully understood here we present stable carbon isotopic values 13corg and c n ratios of bulk organic matter in well dated sediment cores from blackwood sinkhole abaco the bahamas to investigate the changing flux of organic matter into the sinkhole during the late holocene the provenance of preserved organic matter changed through the late holocene between three primary sources as determined by three endmember mixing modeling wetland organic matter from the adjacent epikarst surface authigenic primary productivity in the oligohaline meteoric lens and terrestrial organic matter from the surrounding landscape expansion of wetlands on the adjacent epikarst surface played a critical role by increasing the flux of wetland organic matter to the sinkhole especially during the last 1000 years hurricanes and regional rainfall may have mediated organic matter delivery to the benthos either through hampering wetland development prior to 1000 cal yr bp or by changing dissolved nutrient concentrations available in the basin for primary producers these results demonstrate that organic matter provenance in karst basins is not constant through time and is significantly dependent upon both landscape vegetation on the epikarst surface and changing hydrographic conditions that impacts nutrient availability to primary producers

seawater intrusion in the guanahacabibes peninsula pinar del rio province western cuba effects on karst development and water isotope composition the water resources in the guanahacabibes peninsula are distributed in two areas the northeastern area is characterized by swamps wetlands and lagoons with a low contribution of seawater whereas the area in the southwestern plain shows a considerable development of the karst structures that limits the existence of superficial waters but permits the ingression of the surrounding seawater in this latter area the groundwater showed a marked increase in salinity with the depth in particular groundwater with a seawater fraction of 0 1 had the lowest ca mg carbonates saturation indexes calculated by modeling the mixing between freshwater and seawater using different software thermodynamic databases and equations for activity coefficients generally seawater and groundwaters with an added seawater fraction above 0 60 0 65 showed similar oversaturated indexes in high mg calcites and pure ca carbonates calcite and aragonite differently in the groundwater that showed carbonates undersaturation generally with a seawater fraction between 0 02 and 0 60 the saturation indexes in high mg calcites were 0 2 lower than pure ca carbonates locally the bacterial reduction of the dissolved sulfate enhanced the dissolution of the limestone contributing to the increased development of the karst structures and the seawater intrusion finally the presence near the coastline of fresh ca and na bicarbonate waters was in accordance with the upward flow of the shallow freshwater during the formation of the saline wedge however the oxygen and hydrogen stable isotope composition of the waters showed a probable contribution to the area from a deep aquifer that is recharged in the highest reliefs of the province cordillera de guaniguanico

reactive transport modeling of calcite dissolution in the fresh salt water mixing zone abstract dissolution of calcite in the saltwater mixing zone of coastal carbonate aquifers has been the subject of numerous studies they conclude that dissolution is driven by mixing of freshwater and saltwater which may lead to undersaturation even if both end members are saturated however as transport in the mixing zone is rather complex a fully coupled reactive transport model is needed to properly understand the interplay between transport and chemistry we perform 1 and 2d simulations to gain insight into the processes controlling dissolution rate exploring its sensitivity to the chemistry of end members and the dispersivity of the medium we conclude that the results of sanford and konikow sanford w e konikow l f 1989 simulation of calcite dissolution and porosity changes in saltwater mixing zones in coastal aquifers water resources research 25 655 667 which used a two step method solely transporting the amount of calcite dissolved are essentially correct but their solution is essentially kinetic with a rate dependent on the time increment used the 1d simulations allow us to show that maximum dissolution rates do occur neither at the location nor for the end members of maximum undersaturation for non reactive mixing in the 1d case enhanced transport at the freshwater end causes dissolution to concentrate there however in the 2d case representative of coastal aquifers maximum dissolution occurs at the saline side near the discharge zone because of a very active convection cell that develops there which enhances mixing and thus reaction rates this mechanism may explain observations at blue holes and should display a positive feedback with dissolution causing an increase in permeability that would lead to increased seawater flux and mixing thus enhancing further dissolution

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

association of tepees and palaeokarst in the ladinian calcare rosso southern alps italy the ladinian calcare rosso of the southern alps provides a rare opportunity to examine the temporal relationships between tepees and palaeokarst this unit comprises peritidal strata pervasively deformed into tepees repeatedly capped by palaeokarst surfaces mantled by terra rossa palaeokarsts characterized by a regional distribution across the southern alps occur at the base and at the top of the unit local palaeokarsts confined to this part of the platform occur within the calcare rosso and strongly affected depositional facies tepee deformation ranges from simple antiformal structures peritidal tepees to composite breccias floating in synsedimentary cements and internal sediments senile tepees peritidal tepees commonly occur at the top of one peritidal cycle in association with subaerial exposure at the cycle top while senile tepees affect several peritidal cycles and are always capped by a palaeokarst surface cements and internal sediments form up to 80 of the total rock volume of senile tepees the paragenesis of senile tepees is extremely complex and records several superimposed episodes of dissolution cement precipitation fibrous cements laminated crusts mega rays and deposition of internal sediments marine sediment and terra rossa petrographical observations and stable isotope geochemistry indicate that cements associated with senile tepees precipitated in a coastal karstic environment under frequently changing conditions ranging from marine to meteoric and were altered soon after precipitation in the presence of either meteoric or mixed marine meteoric waters stable isotope data for the cements and the host rock show the influence of meteoric water average 18o 5 8 while strontium isotopes average 87sr 86sr 0 707891 indicate that cements were precipitated and altered in the presence of marine triassic waters field relationships sedimentological associations and paragenetic sequences document that formation of senile tepees was coeval with karsting senile tepees formed in a karst dominated environment in the presence of extensive meteoric water circulation in contrast to previous interpretations that tepees formed in arid environments under the influence of vadose diagenesis tepees initiated in a peritidal setting when subaerial exposure led to the formation of sheet cracks and up buckling of strata this porosity acted as a later conduit for either meteoric or mixed marine meteoric fluids when a karst system developed in association with prolonged subaerial exposure relative sea level variations inducing changes in the water table played a key role in exposing the peritidal cycles to marine mixed marine meteoric and meteoric diagenetic environments leading to the formation of senile tepees the formation and preservation in the stratigraphic record of vertically stacked senile tepees implies that they formed during an overall period of transgression punctuated by different orders of sea level variations which allowed formation and later freezing of the cave infills

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

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

carbonate dissolution and precipitation in coastal environments laboratory analysis and theoretical consideration 1 we have conducted laboratory experiments to examine caco3 dissolution and precipitation in saltwater freshwater mixing zones with a view to understanding and predicting porosity changes in coastal environments mixing of seawater or saline subsurface water with fresh water can be of major importance in the chemical diagenesis of carbonate rocks and sediments we used artificial seawater and nacl solutions of different concentrations under different co2 partial pressures and with different mixing ratios two dimensional flow cells filled with glass beads and crushed calcium carbonate rock were used to measure calcium carbonate precipitation and dissolution respectively an important feature of these experiments is that the results are shown to agree well with a relatively simple transport theory describing mineral precipitation dissolution that results from the nonlinear dependence of caco3 saturation upon electrolyte concentration the theory demonstrates that the rate of dissolution or precipitation depends on the curvature and sign of the solubility as a function of salinity the square of the salinity gradient and the macroscopic dispersion coefficient the theory is largely scale independent and depends upon field parameters that can be determined analysis of data from three field sites yucatan peninsula bermuda and mallorca demonstrates excellent agreement between field observations and theory

the nassara gold prospect gaoua district southwestern burkina faso abstract the nassara au prospect is located in the birimian boromo greenstone belt in southwestern burkina faso it is part of a larger mineralized field that includes the cu au porphyry system of gaoua to the north at nassara mineralization occurs within the west batie shear zone that follows the contact between volcanic rocks basalt and andesite and volcano sediments pyroclastics and black shales at the southern termination of the boromo belt gold is associated with pyrite and other fe bearing minerals that occur disseminated within the sheared volcanic and volcano sedimentary rocks in particular highest grades are distinguished in alteration halos of small quartz albite ankerite veins that form networks along the shear zone here pyrites are marked by as poor and as rich growth zones the latter containing gold inclusions gold mineralization formed during d2na subsequent shear fractures related to d3na related are devoid of gold nassara is a classical orogenic gold occurrence where gold is associated to disseminated pyrite along quartz veins

terminal classic drought in the northern maya lowlands inferred from multiple sediment cores in lake chichancanab mexico we present new density records from sediment cores taken along a depth transect in lake chichancanab mexico the data reveal in great detail the climatic events that comprised the terminal classic drought tcd and coincided with the demise of classic maya civilization between ca 750 and 1050 ad in shallow water cores the tcd is marked by a condensed gypsum horizon in deeper water sections it is expanded and represented by numerous interbedded gypsum and organic rich strata the tcd was not a single two century long megadrought but rather consisted of a series of dry events separated by intervening periods of relatively moister conditions we estimate the tcd occurred between ca 770 and 1100 ad and included an early phase ca 770 870 ad and late phase ca 920 1100 ad the intervening 50 year period ca 870 920 ad was relatively moister each dry phase is represented by multiple gypsum density bands interbedded with organic rich sediment that indicate alternating dry and wet conditions spectral analysis revealed significant periods around 213 50 and 27 years despite uncertainty regarding the ages of these events their pattern is robust and generally consistent with other proxy records under the same climate regime such as the marine cariaco basin off northern venezuela science 299 2003 1731

geochemical processes and solute transport at the seawater freshwater interface of a sandy aquifer geochemical processes occurring at a seawater freshwater interface were studied in a shallow coastal siliclastic aquifer containing minor amounts of calcite data were collected from 106 piezometers in a 120 m transect from the coastline and landward in the first 40 m from the coastline a wedge of saltwater is intruding below the freshwater aquifer the aquifer is strongly reduced with mineralization of organic matter by methanogenesis in the freshwater aquifer and sulfate reduction dominating in the most seaward part of the saline aquifer the spatial separation of cations in the aquifer indicated a slow freshening process where ca2 from freshwater displaced the marine cations na and mg2 from the exchanger complex the resulting loss of ca2 from solution decreases the saturation state for calcite and possibly causes calcite dissolution a storm flooding event was recorded where pulses of dense seawater sank through the fresh aquifer as a result the terminal electron accepting process switched from methanogenesis to sulfate reduction the pulses of sinking seawater also triggered cation exchange reactions where ca2 was expelled from the exchanger by seawater na and mg2 the released ca2 is being flushed from the aquifer by groundwater flow and this export of ca2 will in the long term cause decalcification of the sediment the water composition in the aquifer is in a transient state as the result of various processes that operate on different timescales oxidation of organic matter occurs continuously but at a rate decreasing on a geological time scale the freshening of the aquifer operates on the timescale of a few years the episodic flooding and sinking of seawater through the aquifer proceeds in the course of days to weeks but occurs irregularly with years in between

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

indicators of propagation direction and relative depth in clastic injectites implications for laminar versus turbulent flow processes clastic injectites are widely recognized in deep water stratigraphic successions although their sediment transport processes propagation direction and depth of injection are poorly constrained understanding how they form is important as injectites are increasingly being recognized as significant components of sedimentary basin fills yet are not predicted by standard sedimentary facies models here analysis of features on the margins of exhumed clastic sills and dikes and clasts within them enables their genesis to be determined a diverse array of diagnostic structures is found on the margins of injectites in the karoo basin south africa where the net direction of injection and position of the parent sand are well constrained injectite margin features include mudstone clast rich surfaces planar or smooth surfaces blistered surfaces and parallel and plumose ridged surfaces combined these features are critical in distinguishing injected sands where injectites are strata concordant from those of primary deposition all features are indicative of propagation through brittle very fine grained sediments at depths where the applied shear stress is at least four times the tensile strength of the host rock additionally the presence of parallel ridges plumose ridges and steps allows local fracture propagation to be constrained and in turn injection direction the features described provide evidence that sands were injected at considerable depth in closed fractures with limited capacity for flow dilution and turbulence enhancement calculated reynolds numbers lack of erosion at injectite walls and the presence of mud clasts at the top and base of sills indicate that many flows were likely fully laminar during injection the sedimentary features of these confined relatively deep laminar flow induced injectites are very different from injectites that reach the surface and produce extrudites surface linked injectites are associated with open conduits where a greater fraction of carrier fluid to particles can be accommodated enabling highly turbulent lower concentration flows

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

groundwater geochemistry fluctuations along a fresh saltwater gradient on the carbonate islands of the lower florida keys abstract climate change will have long lasting effects on the availability of fresh water on small carbonate islands that have isolated fresh groundwater lenses particularly as sea level rises and rainfall regimes shift the carbonate islands of the florida keys provide an ideal location to study the effect of variable rainfall on the aqueous geochemistry of the islands groundwater in a rainfall driven carbonate system the expectation is that limestone dissolution will occur within the vadose zone resulting in increased ions in the groundwater however geochemical processes are also affected by the salinity of groundwater and the extent of the mixing zone between fresh and salt water we chose two islands to conduct the study of the shallow groundwater the largest island in the lower florida keys big pine key bpk and a smaller island upper sugarloaf key slk from may 2011 through april 2012 monthly groundwater samples were collected from 24 shallow 1 m deep wells located along a fresh to saline gradient on both islands groundwater chemistry was compared with rainfall amounts from a weather station on bpk saturation indices for aragonite and calcite generated with geochemical modeling in phreeqc were compared to conservative mixing between gulf of mexico water and freshwater equilibrium to supersaturated conditions with respect to carbonate minerals dominated in all of the groundwater samples saturation indices varied with rainfall with the most supersaturated samples observed after a large rain event and samples approaching equilibrium after the longest period without rainfall calcium in excess of what would be expected from conservative mixing of fresh water and seawater was observed in all groundwater samples and was elevated at near shore locations especially on bpk contrary to expectations dissolution resulting from mixing of freshwater and seawater was not supported in the shallow groundwater instead dissolution within the narrow vadose zone from rain events likely resulted in the excess calcium in the groundwater seasonal fluctuations in groundwater composition were primarily observed on the smaller island and were related to the fresh water balance changing rapidly after a heavy rain event and suggest that a size threshold has been surpassed for a stable lens rising seas will further decrease lens extent and vadose zone depth reducing the potential for future limestone dissolution

the early diagenetic origin of lower carboniferous mottled limestones pseudobreccias dark mottles are a prominent and widespread feature of the regressive cyclic shallow marine limestones which form the late asbian succession in many parts of britain the colour difference which defines mottles in outcrop is caused by distinct but often subtle petrographic differences in the limestone fabric specifically mottles contain a light brown coloured opaque inclusion rich calcite spar with characteristic dull brown luminescence mottle spar outside mottle margins this calcite spar is absent with clear inequant blocky cements forming the pore filling phase mottle spar comprises a fabric of irregular crystals predominantly 5 40 m in diameter with more regular crystals up to 100 m diameter often occurring in intraparticle and large interparticle pores under cathodoluminescence mottle spar displays crystal morphologies and growth patterns which indicate that both localized neomorphism and patchy cementation contributed to mottle formation cathodoluminescence cement stratigraphy shows that mottle spar pre dates all other major pore filling cements in the local asbian succession but post dates marine micritization mottle spar sharply defines the moulds of former aragonitic allochems which are now filled by the later clear inequant spar cements this shows that aragonite dissolution occurred after the formation of mottle spar mottles in calcretes contain unaltered allochems which have been protected from the effects of subaerial micritization by mottle spar although mottles are often affected by subaerial brecciation this evidence shows that mottles formed during early diagenesis after marine micritization but before dissolution of aragonite subaerial exposure and meteoritic phreatic cementation mottles represented lithified patches of very low porosity which are interpreted to have formed in the marine freshwater mixing zone during the repeated phases of regression and emergence in the late asbian

reef drowning during the last deglaciation evidence for catastrophic sea level rise and ice sheet collapse elevations and ages of drowned acropora palmata reefs from the caribbean atlantic region document three catastrophic metre scale sea level rise events during the last deglaciation these catastrophic rises were synchronous with 1 collapse of the laurentide and antarctic ice sheets 2 dramatic reorganization of ocean atmosphere circulation and 3 releases of huge volumes of subglacial and proglacial meltwater this correlation suggests that release of stored meltwater periodically destabilized ice sheets causing them to collapse and send huge fleets of icebergs into the atlantic massive inputs of ice not only produced catastrophic sea level rise drowning reefs and destabilizing other ice sheets but also rapidly reduced the elevation of the laurentide ice sheet flipping atmospheric circulation patterns and forcing warm equatorial waters into the frigid north atlantic such dramatic evidence of catastrophic climate and sea level change during deglaciation has potentially disastrous implications for the future especially as the stability of remaining ice sheets such as in west antarctica is in question

soft sediment deformation structures in a lacustrine sedimentary succession induced by volcano tectonic activities an example from the cretaceous beolgeumri formation wido volcanics korea abstract the cretaceous beolgeumri formation is composed of laminated mudstones intercalated with sandstones chert and a bed of lapilli tuff that were deposited in a lacustrine environment at the terminal part of a regional strike slip fault systems on the southwestern korean peninsula the beolgeumri formation contains various types of soft sediment deformation ssd structures that are characterized by a wide extent

sand injectites at the base of the coconino sandstone grand canyon arizona usa abstract in the grand canyon large tabular and wedge shaped sand filled cracks commonly occur at the base of the coconino sandstone penetrating downward into the coarse siltstones of the hermit formation all previous workers have casually identified the vertical sand filled cracks as desiccation cracks until now they have never been studied cracks and their associated features were found and examined at thirty locations and it was found that they have characteristics difficult to explain using desiccation mud cracks or large playa cracks as a model instead it was found the cracks have features commonly found in clastic dikes and sand injectites some lateral sand bodies associated with the cracks have clastic sill like characteristics liquefaction and injection of the basal coconino into the hermit is indicated by 1 macroscopic and microscopic banding flow structures within the cracks 2 bedded sandstone clast breccias in structureless sandstone lenses at the base of the coconino 3 lateral sand bodies which are connected to the vertical cracks 4 a zoned depth distribution of cracks about the bright angel fault zone 5 insufficient clay mineralogy and particle size for the hermit to crack by desiccation 6 preferred orientation of the cracks roughly perpendicular to the bright angel fault zone and several other features caution should be exercised when interpreting sand filled cracks as desiccation features i e mud cracks even if the interpretation fits well with accepted paleoenvironmental models

a giant underwater encrusted stalactite from the blue hole lighthouse reef belize revisited a complex history of biologically induced carbonate accretion under changing meteoric and marine conditions a late pleistocene to holocene submerged and encrusted speleothem exhibits a complex history including a meteoric phase and two marine phases a combined study using petrography mineralogy and inorganic and organic geochemistry as well as geochronology has shown that phototrophic and heterotrophic biological activity impacted carbonate precipitation during all phases of carbonate accretion the stalactite formed ca 30 m below modern sea level at a marginal overhang in the blue hole of lighthouse reef atoll unlike purely meteoric speleothems the belize example consists of a meteoric core a marine aragonite crust and a serpulid micrite rich outer crust as a result of postglacial flooding of the karst cave the core of the stalactite has a tufaceous texture containing algal or microbial remains and consists entirely of low magnesium calcite formed 19 55 10 68 kyr bp the texture suggests that the stalactite formed at the cave entrance and hence the former cave ceiling had apparently collapsed earlier during the pleistocene oxygen 18o and carbon 13c isotopes across the core suggest a trend towards drier conditions and reduced soil and plant cover after the last glacial maximum the marine aragonite crust consists of stacked botryoids in which individual crystals up to 700 lm have dark terminations enriched in high magnesium calcite this crust accreted from 10 82 to 9 95 kyr bp in warm shallow water during the early holocene thermal optimum carbonate accretion rates were considerable and averaged 125 m yr the crust has a dense laminated texture on one side and a porous shrubby texture on the other the presence of n c16 1 5 n c17 1 6 and 10me c16 fatty acids in the laminated crust suggests that sulfate reducing bacteria contributed to aragonite formation in an environment that was less open than the formation environment of the porous crust where these biomarkers are lacking n c16 1 5 n c17 1 6 or are less abundant 10me c16 enrichment of 34s and 18o in carbonate associated sulfate cas relative to seawater sulfate also suggests sulfate reduction during carbonate formation the greater contribution of heterotrophic processes to aragonite precipitation in the laminated crust is also reflected in 13c values as low as 1 3 whereas no such depletion is observed in the aragonite of the porous crust 13c values as low as 0 0 a pronounced isotopic variability and excursions to positive 13c values as high as 3 5 0 in the inner half of the laminated crust indicate an episodic local impact of photosynthesis on aragonite precipitation whereas the lack of such excursions in the porous crust 13c values as high as 1 5 0 is again best explained by a more open environment of formation after a ca 5 kyr hiatus from 4 39 kyr bp a biogenic crust of abundant serpulids and finely crystalline microbial and detrital carbonate consisting of high magnesium calcite and aragonite accreted on the outer surface of the stalactite outermost crust accretion was probably influenced by the inundation of the lighthouse reef lagoon that started to shed abundant fine grained carbonate sediment into the blue hole the stalactite broke off the cave ceiling either before or after the formation of the outermost crust likely due to seismic movements along the nearby plate boundary the study demonstrates that like speleothems from the terrestrial realm submerged stalactites may have had complex histories with great potential as paleoenvironmental archives

solution conduits as indicators of late quaternary sea level position abstract solution conduits or caves can provide a measure of glacio eustatic sea level position for the quaternary in high latitudes cave deposits contain artifacts fossils and sediments that reflect surface conditions with respect to climate secondary calcite deposits most notably stalagmites record growth episodes during ice minima and non growth during ice maxima they provide an indirect estimate of areal ice cover at high latitudes and are an indirect measure of sea level in low latitudes stable carbonate platforms contain caves that provide a direct measure of past sea level position solution conduits developing in a fresh water lens will record the position of the lens and therefore sea level as sea level fluctuates fresh water lens horizons and conduit development horizons will shift preserving a record of past sea level position cave wall rock and cave deposits can produce a chronology for given conduit positions secondary calcite deposits notably stalagmites record growth periods during sea level low stands or ice maxima and record growth hiatuses during flooding by sea level high stands or ice minima the inverse of high latitude stalagmites lighthouse cave san salvador island bahamas records a sea level high stand at 1 to 6 m for some time period between 85 000 and 70 000 years ago based on position and timing of conduit development and records sea level at present elevation for some time period between 49 000 and 37 000 years ago based on a stalagmite with a marine overgrowth

regional hydrogeochemistry of a modern coastal mixing zone in west central florida groundwater samples were collected along flow paths in the unconfined upper floridan aquifer that cross the inland freshwater recharge area and the coastal discharge area a groundwater flow and solute transport model was used to evaluate groundwater flow and mixing of fresh and saline groundwater along a cross section of the unconfined upper floridan aquifer results show that between 8 and 15 of the fresh and 30 31 of the saline groundwater penetrates to the depth in the flow system where contact with and dissolution of gypsum is likely the deeply circulating fresh and saline groundwater returns to the near surface environment discharging caso4 rich water to the coastal area where it mixes with fresh cahco3 groundwater resulting in a prediction of calcite precipitation in the modern mixing zone

climate variability on the yucatan peninsula mexico during the past 3500 years and implications for maya cultural evolution climate variability on the yucatan peninsula during the past 3500 yrs is reconstructed from the measurement of 18o in monospecific ostracods and gastropods in a 6 3 m sediment core from lake punta laguna mexico this late holocene record is divided into three periods based on changes in mean 18o values from 3310 to 178514c yr b p period i low mean 18o values indicate relatively wet conditions i e low evaporation to precipitation ratio e p mean oxygen isotopic values increased 178514c yr b p and the interval between 1785 and 93014c yr b p period ii was distinctly drier than the periods before or after the climate during the latter part of period ii was persistently dry with exceptionally arid events centered at 1171 1019 and 94314c yr b p equivalent to 862 986 and 1051 a d this interval of frequent drought was recorded at several other localities in mexico and central america and coincided with the collapse of classic maya civilization following the last arid event 18o values decreased abruptly at 93014c yr b p beginning of period iii signaling a return to wetter conditions that have generally prevailed to the present with the exception of a dry episode centered at 55914c yr b p 1391 a d the paleoclimatic record from punta laguna provides evidence that multi decadal and millennial scale changes ine poccurred on the yucatan peninsula during the late holocene these wet dry episodes may have influenced cultural evolution in mesoamerica

palaeohydrogeological control of palaeokarst macro porosity genesis during a major sea level lowstand danian of the urbasa andia plateau navarra north spain abstract an extensive palaeokarst porosity system developed during a pronounced mid paleocene third order lowstand of sea level is hosted in danian limestones of the urbasa andia plateau in north spain these limestones were deposited on a 40 50 km wide rimmed shelf with a margin characterised by coralgal buildups and coarse grained bioclastic accumulations the sea level fall that caused karstification was of approximately 80 90 m magnitude and 2 5 ma in duration during the exposure a 450 m wide belt of sub vertical margin parallel fractures developed a few hundred metres inboard of the shelf edge most fractures are 90 100 m deep average 1 m in width and are associated with large erosional features created by collapse of the reefal margin inland from the fracture belt three superimposed laterally extensive cave systems were formed over a distance of 3 5 km perpendicular to shelf edge at depths ranging from 8 31 m below the exposure surface the palaeocaves range from 0 3 to 2 m in height average 1 5 m high they show no evidence of meteoric processes and are filled with thanetian grainstones rich in reworked microcodium a lithology that also occurs infilling the fractures the caves are interpreted as due to active corrosion at the saline water fresh water mixing zone caves are missing from the shelf edge zone probably because the fractures beheaded the meteoroic lens preventing mixing zone cave development beyond the fracture zone towards the platform interior each cave system passes into a prominent horizon averaging 1 m in thickness of spongy porosity with crystal silt infills and red fe oxide coatings the spongy horizons can be traced for 5 5 km inboard from the cave zone and occur at 10 5 m 25 m and 32 m below the exposure surface in the inland zone two additional horizons with the same spongy dissolution have been recognised at depths of 50 m and 95 m all are analogous to swiss cheese mixing zone corrosion in modern carbonate aquifers and probably owe their origins to microbially mediated dissolution effects associated with a zone of reduced circulation in marine phreatic water in the most landward sections a number of collapse breccia zones are identified but their origin is unclear the palaeokarst system as a whole formed during the pulsed rise that followed the initial sea level drop with the three main cave spongy zones representing three successive sea level stillstands recorded by stacked parasequences infilling large erosional scallops along the shelf margin the geometry of the palaeo mixing zones indicates a low discharge system and together with the lack of meteoric karstic features favours a semi arid to arid climatic regime which is further supported by extensive calcrete bearing palaeosols occurring in coeval continental deposits

reconstructing water level in hoyo negro quintana roo mexico implications for early paleoamerican and faunal access abstract the skeletal remains of a paleoamerican naia hn5 48 and extinct megafauna were found at 40 to 43 mbsl in a submerged dissolution chamber named hoyo negro hn in the sac actun cave system yucatan peninsula mexico the human remains were dated to between 12 and 13 ka making these remains the oldest securely dated in the yucatan twelve sediment cores were used to reconstruct the holocene flooding history of the now phreatic cave passages and cenotes ich balam oasis that connect to hn four facies were found 1 bat guano and seed sf 2 lime mud mf 3 calcite rafts crf and 4 organic matter calcite rafts om crf which were defined by their lithologic characteristics and ostracod foraminifera and testate amoebae content basal radiocarbon ages ams of aquatic sediments sf combined with cave bottom and ceiling height profiles determined the history of flooding in hn and when access was restricted for human and animal entry our results show that the bottom of hn was flooded at least by 9850 cal yr bp but likely earlier we also found that the pit became inaccessible for human and animal entry at 8100 cal yr bp when water reaching the cave ceiling effectively prevented entry water level continued to rise between 6000 and 8100 cal yr bp filling the cave passages and entry points to hn cenotes ich balam and oasis analysis of cave facies revealed that both holocene sea level rise and cave ceiling height determined the configuration of airways and the deposition of floating and bat derived om guano and seeds calcite rafts which form on the water surface are also dependent on the presence of airways but can also form in isolated air domes in the cave ceiling that affect their loci of deposition on the cave bottom these results indicated that aquatic cave sedimentation is transient in time and space necessitating extraction of multiple cores to determine a limit after which flooding occurred

a global compilation of coral sea level benchmarks implications and new challenges i present a quality controlled compilation of sea level data from u th dated corals encompassing 30 studies of 13 locations around the world the compilation contains relative sea level rsl data from each location based on both conventional and open system u th ages i have applied a commonly used age quality control criterion based on the initial 234u 238u activity ratios of corals in order to select reliable ages and to reconstruct sea level histories for the last 150 000 yr this analysis reveals scatter of rsl estimates among coeval coral benchmarks both within individual locations and between locations particularly during marine isotope stage mis 5a and the glacial inception following the last interglacial the character of data scatter during these time intervals imply that uncertainties still exist regarding tectonics glacio isostacy u series dating and or coral position to elucidate robust underlying patterns with confidence limits i performed a monte carlo style statistical analysis of the compiled coral data considering appropriate age and sea level uncertainties by its nature such an analysis has the tendency to smooth obscure millennial scale and finer details that may be important in individual datasets and favour the major underlying patterns that are supported by all datasets this statistical analysis is thus functional to illustrate major trends that are statistically robust what we know trends that are suggested but still are supported by few data what we might know subject to addition of more supporting data and improved corrections and which patterns data are clear outliers unlikely to be realistic given the rest of the global data and possibly needing further adjustments prior to the last glacial maximum and with the possible exception of the 130 120 ka period available coral data generally have insufficient temporal resolution and unexplained scatter which hinders identification of a well defined pattern with usefully narrow confidence limits this analysis thus provides a framework that objectively identifies critical targets for new data collection improved corrections and integration of coral data with independent stratigraphically continuous methods of sea level reconstruction

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

sediment flow and deformation sfd layers evidence for intrastratal flow in laminated muddy sediments of the triassic osawa formation northeast japan abstract thin chaotic layers containing abundant intraformational mud clasts are found in the offshore laminated mudstone of the triassic osawa formation in northeast japan the geometry and internal structures of the layers are somewhat similar to those of slump slide or debris flow deposits however the layers have both upper and lower erosional contacts projections of host sediments and mud clasts with planed surfaces are identified beneath the upper contact of the layers closely packed sheet form or ellipsoidal mud clasts are embedded in a poorly sorted fine to coarse grained sandy matrix some mud clasts are tightly folded or show imbricated stacking internal layering structures are also well developed in the layers the above features strongly suggest soft sediment deformation as horizontal displacement of sand and mud under buried conditions here we term these layers sediment flow and deformation sfd layers deformation layers with similar attributes have been identified by some prior authors as in the case of flow of liquefied and or fluidized host sand and clastic sill intrusion however the sfd layers described herein have more complex structure indicating advanced deformation occurrence of the sfd layers is stratigraphically limited to the uppermost part of the osawa formation which is overlain by sand rich submarine fan deposits the fukkoshi formation it suggests that the stress field caused by differential loading of overlying deposits facilitated intrastratal flow and sill intrusions of sand the vertical confinement was also controlled by the anisotropy in physical properties such as tensile strength of laminated mud and or conditions of gentle slope

groundwater circulation and geochemistry of a karstified bank marginal fracture system south andros island bahamas abstract on the east coast of south andros island bahamas a major bank marginal fracture system characterised by vertically extensive cavern systems blue holes is developed sub parallel to the steep sided deep water re entrant of the tongue of the ocean in addition to providing a discharge route for meteoric mixed and geochemically evolved saline groundwaters a strong local circulation occurs along the fracture system this generates enhanced vertical mixing within voids of the fracture system evidenced by the increasing mixing zone thickness and the thinning and increasing salinity of brackish lens waters from north to south along the fracture system furthermore tidally driven pumping of groundwaters occurs between the fracture and adjacent carbonate aquifer affecting a zone up to 200 m either side of the fracture the resultant mixing of groundwaters of contrasting salinity and pco2 within and along the fracture system and with the surrounding aquifer waters together with bacterial oxidation of organic matter generates significant potential for locally enhanced diagenesis undersaturation with respect to calcite within the fresh or brackish salt water mixing zone is observed in the fracture system and predicted in the adjacent aquifer while mixing between the brackish fracture lens and surrounding high pco2 fresh waters causes dissolution of aragonite but not calcite the latter gives rise to considerable secondary porosity development because active tidal pumping ensures continued renewal of dissolutional potential this is evidenced by calcium and strontium enrichment in the brackish lens which indicates porosity generation by aragonite dissolution at a maximum rate of 0 35 ka 1 up to twice the average estimated for the fresh water lens in contrast saline groundwaters are depleted in calcium relative to open ocean waters suggesting the formation of calcite cements the development of a major laterally continuous cavernous fracture zone along the margin of the carbonate platform permits enhanced groundwater flow and mixing which may result in generation of a diagenetic halo at a scale larger than that generally recognised around syn sedimentary fractures in fossil carbonates this may be characterised by increased secondary porosity where a relative fall in sea level results in exposure and formation of a meteoric groundwater system or cementation by marine calcite both below this meteoric system and where the bank surface is flooded by seawater

depositional sequences from high concentration turbidity currents cretaceous uhangri formation sw korea abstract a detailed sedimentary facies analysis of the middle part of the uhangri formation late cretaceous sw korea reveals that the dominant facies sequences consist of 1 crudely stratified and inverse to normally graded gravelly sandstone laminated sandstone and sand siltstone couplets 2 inverse to normally graded gravelly sandstone laminated sandstone and sand siltstone couplets 3 stratified and normally graded gravelly sandstone and laminated sandstone the lower units of each fining upward sequence are characterized by crude stratification probably formed under high concentration and cohesionless flow conditions a progressive freezing of the traction carpet causes crude stratification whereas strong dispersive pressures at the base form inverse grading the upper laminated sandstone and sand siltstone couplets represent the overlying low concentration turbidity currents

the muknal cave near tulum mexico an early holocene funeral site on the yucatan peninsula here we report on an incomplete human skeleton soot patches related to anthropogenic fireplaces and cut marks on the mandible of an extinct peccary from the submerged muknal cave southwest of t

a 6000 year record of ecological and hydrological changes from laguna de la leche north coastal cuba abstract laguna de la leche north coastal cuba is a shallow 3 m oligohaline 2 0 4 5 coastal lake surrounded by mangroves and cattail stands a 227 cm core was studied using loss on ignition pollen calcareous microfossils and plant macrofossils from 6200 to 4800 cal yr bp the area was an oligohaline lake the period from 4800 to 4200 cal yr bp saw higher water levels and a freshened system these changes are indicated by an increase in the regional pollen rain as well as by the presence of charophyte oogonia and an increase in freshwater gastropods hydrobiidae by 4000 cal yr bp an open mesohaline lagoon had formed an increase in salt tolerant foraminifers suggests that water level increase was driven by relative sea level rise the initiation of laguna de la leche correlates with a shift to wetter conditions as indicated in pollen records from the southeastern united states e g lake tulane this synchronicity suggests that sea level rise caused middle holocene environmental change region wide two other cores sampled from mangrove swamps in the vicinity of laguna de la leche indicate that a major expansion of mangroves was underway by 1700 cal yr bp

sea level history of the past two interglacial periods new evidence from u series dating of reef corals from south florida abstract as a future warm climate analog much attention has been directed to studies of the last interglacial period or marine isotope substage mis 5 5 which occurred 120 000 years ago nevertheless there are still uncertainties with respect to its duration warmth and magnitude of sea level rise here we present new data from tectonically stable peninsular florida and the florida keys that provide estimates of the timing and magnitude of sea level rise during the last interglacial period the last interglacial high sea stand in south florida is recorded by the key largo limestone a fossil reef complex and the miami limestone an oolitic marine sediment thirty five new high precision uranium series ages of fossil corals from the key largo limestone indicate that sea level was significantly above present for at least 9000 years during the last interglacial period and possibly longer ooids from the miami limestone show open system histories with respect to u series dating but show a clear linear trend toward an age of 120 ka correlating this unit with the last interglacial corals of the key largo limestone older fossil reefs at three localities in the florida keys have ages of 200 ka and probably correlate to mis 7 these reefs imply sea level near or slightly above present during the penultimate interglacial period elevation measurements of both the key largo limestone and the miami limestone indicate that local relative sea level was at least 6 6 m and possibly as much as 8 3 m higher than present during the last interglacial period

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

floating rafts of calcite crystals in cave pools central texas u s a crystal habit vs saturation state abstract calcite precipitation at the air water interface in cave pools in central texas u s a produces floating rafts of interconnected low mg calcite crystals with individual crystal habits that range from equant length to width 1 1 to prismatic 4 1 saturation state for the waters ranges from 0 19 to 1 35 sic log iap k equant crystals precipitate from waters with a lower saturation index sic and form rafts with a fused fabric whereas prismatic crystals precipitate from higher sic waters and form rafts with an interlaced fabric the pools contain low magnesium molal mg ca 0 6 calcium bicarbonate and calcium bicarbonate nitrate type waters with temperatures that range from 13 8 c to 20 7 c and ph readings from 6 7 to 8 4 equant euhedral crystals precipitate from water with saturation states close to equilibrium visible defects in the equant crystals include incomplete edges between faces and nearly circular mean diameter 9 m to angular holes in faces the holes apparently result from crystallite growth around foreign objects on the crystal surface such as gas bubbles prismatic crystals precipitate from supersaturated water faces of these subhedral crystals are smaller in area than the faces of the equant crystals no intrafacial circular holes are seen but trigonal intercrystallite pores are common in the prismatic crystals the variety in crystal habits from equant to prismatic is due to preferential growth along one crystallographic axis thus in these cave pools crystal habit is related to the saturation state of the water

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

rapid coupling between ice volume and polar temperature over the past 150 000 years a new approach to dating a continuous sea level record using speleothem u th ages shows that past variations in global ice volume occurred within centuries of polar climate change with rates of sea level rise reaching at least 1 metre per century

chemical hydrogeology in natural and contaminated environments abstract chemical hydrogeology including organic and inorganic aspects has contributed to an increased understanding of groundwater flow systems geologic processes and stressed environments most of the basic principles of inorganic chemical hydrogeology were first established by investigations of organic free regional scale systems for which simplifying assumptions could be made the problems of groundwater contamination are causing a shift of emphasis to microscale systems that are dominated by organic chemical reactions and that are providing an impetus for the study of naturally occurring and manmade organic material along with the decrease in scale physical and chemical heterogeneity become major controls current investigations and those selected from the literature demonstrate that heterogeneity increases in importance as the study site decreases from regional scale to macroscale to microscale increased understanding of regional scale flow systems is demonstrated by selection of investigations of carbonate and volcanic aquifers to show how application of present day concepts and techniques can identify controlling chemical reactions and determine their rates identify groundwater flow paths and determine flow velocity and determine aquifer characteristics the role of chemical hydrogeology in understanding geologic processes of macroscale systems is exemplified by selection of investigations in coastal aquifers phenomena associated with the mixing zone generated by encroaching sea water include an increase in heterogeneity of permeability diagenesis of minerals and formation of geomorphic features such as caves lagoons and bays ore deposits of manganese and uranium along with a simulation model of ore forming fluids demonstrate the influence of heterogeneity and of organic compounds on geochemical reactions associated with genesis of mineral deposits in microscale environments importance of heterogeneity and consequences of organic reactions in determining the distributions and concentrations cf constituents are provided by several studies including infiltration of sewage effluent and migration of creosote in coastal plain aquifers these studies show that heterogeneity and the dominance of organically controlled reactions greatly increase the complexity of investigations

inorganic calcite morphology roles of fluid chemistry and fluid flow abstract evaluation of calcite crystal habits and fabric and their relation to precipitating fluids in spelean environments indicates that habit variations are controlled primarily by degree of supersaturation at less than 6 times supersaturation crystal habits are limited to those with shallow to steep rhombohedral forms i e 1011 4041 with increasing supersaturation scalenohedrons extremely steep rhombohedrons pinacoids and hexagonal prisms are developed slight elongation due to differences in crystal dimensions of these forms may arise i e scalenohedrons versus shallow rhombohedrons at extreme supersaturation 12 times curvature of crystal faces or curved surfaces appear the development of fibrous versus equant fabrics is the result of changes or modification of reactant supply rates and the number of crystallites nuclei present under rapid flow conditions growth rates are accelerated and greater numbers of nuclei are present thus compromise boundaries parallel to c axis and perpendicular to flow and substrate are rapidly attained in the absence of flow fewer crystallites are present and larger well developed crystals or branching forms dictated by saturation conditions arise in the absence of flow at low supersaturation elongate composite crystals and hence fibrous fabrics may result from migration of the fluid crystal interface as a result of changing or oscillating water levels a flow control mechanism can be applied to numerous geological conditions in which transitions from fibrous to equant crystal morphologies are observed

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

post chicxulub depositional and diagenetic history of the northwestern yucatan peninsula mexico abstract the chicxulub sedimentary basin of the northwestern yucatan peninsula mexico which was formed because of the largest identified phanerozoic bolide impact on earth became a site of deposition of dominantly marine carbonate sediments during most of the cenozoic era this is a study of the filling and diagenetic history of this basin and surrounding areas the study makes use of lithologic biostratigraphic petrographic and geochemical data obtained on core samples from boreholes drilled throughout the northwestern yucatan peninsula the core sample data indicate that 1 the chicxulub sedimentary basin concentrated the deposition of pelagic and outer platform sediments during the paleocene and eocene and in places during the early oligocene as well and filled during the middle miocene 2 deeper water limestone also is present within the paleocene and lower eocene of the proposed santa elena depression which is located immediately south of the basin 3 shallow water deposits are relatively more abundant outside the basin and depression than inside 4 the autigenic and allogenic silicates from the paleogene formations are the most abundant inside the depression 5 sediment deposition and diagenesis within the basin also were controlled by impact crater topography 6 the abundance of the possible features of subaerial exposure increases upward and outward from the center of the basin and 7 the formation of replacive low magnesium calcite and dolomite dedolomitization dissolution and precipitation of vug filling calcite and dolomite cement have been more common outside the basin than inside 18 o in whole rock excluding vug filling calcite from core samples ranges from 7 14 to 0 85 pdb 13 c varies from 6 92 to 3 30 pdb both stable isotopes correlate inversely with the abundance of subaerial exposure features indicating that freshwater diagenesis has been extensive especially outside and at the edge of the chicxulub sedimentary basin 18 o and 13 c in whole rock excluding vug filling dolomite ranges from 5 54 to 0 87 pdb and 4 63 to 3 38 pdb respectively most dolomite samples have negative 18 o and positive 13 c suggesting that replacive dolomitization involved the presence of a fluid dominated by freshwater and or an anomalously high geothermal gradient most dolomite xrd determined mole percent caco 3 varies between 51 and 56 replacive dolomite is larger more euhedral and less stoichiometric inside the chicxulub sedimentary basin than outside

calibration of the c 14 timescale over the past 30 000 years using mass spectrometric u th ages from barbados corals uranium thorium ages obtained by mass spectrometry from corals raised off the island of barbados confirm the high precision of this technique over at least the past 30 000 years comparison of the u th ages with 14c ages obtained on the holocene samples shows that the u th ages are accurate because they accord with the dendrochronological calibration before 9 000 yr bp the 14c ages are systematically younger than the u th ages with a maximum difference of 3 500 yr at 20 000 yrbp the u th technique thus provides a way of calibrating the radiocarbon timescale beyond the range of dendrochronological calibration

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

the effect of a confining unit on the geochemical evolution of ground water in the upper floridan aquifer system in west central florida sections of the upper floridan aquifer system range in character from confined to leaky to unconfined the confining unit is the hawthorn formation a clay rich sequence the presence or absence of the hawthorn formation affects the geochemical evolution of the ground water in the upper floridan aquifer system mass balance and mass transfer models suggest that in unconfined areas the geochemical reactions are dolomite dissolution ion exchange mg for na k sulfate reduction calcite dissolution and co2 exchange in the areas in which the hawthorn formation is leaky the evolution of the ground water is accounted for by ion exchange sulfate reduction calcite dissolution and co2 exchange in the confined areas no ion exchange and only limited sulfate reduction occur and the chemical character of the ground water is consistent with dolomite and gypsum dissolution calcite precipitation and co2 ingassing the hawthorn formation acts both as a physical barrier to the transport of co2 and organic matter and as a source of ion exchange sites but the carbonate mineral reactions are largely unaffected by the extent of confinement of the upper floridan aquifer

geochemical evolution and timescale of seawater intrusion into the coastal aquifer of israel this study is an attempt to quantify the geochemical processes and the timescale of seawater intrusion into a coastal aquifer from changes in the major ionic composition of the water and the natural distribution of the cosmogenic isotopes 14c and 3h for that purpose we sampled saline and brackish groundwaters from the israeli coastal aquifer a multilayer sampler mls was used to obtain very high resolution 10 cm profiles across the fresh saline water interface fsi the chemical and stable isotope data revealed three distinct water types end members that are located in different zones on the route to the coastal aquifer 1 slightly modified mediterranean seawater sws 2 slightly diluted with up to 20 fresh groundwater saline groundwater sds and 3 fresh groundwater fgw the sws samples generally show an excess of total alkalinity and total dissolved inorganic carbon dic and a depletion of 13cdic and 14cdic with respect to normal seawater indicating that anaerobic oxidation of organic matter is the first diagenetic reaction that affects seawater during its penetration into the bottom sediments sds waters appear when sws is slightly diluted gain ca2 and sr2 and is depleted in k suggesting that the main processes that transform sws into sds are slight dilution with fresh groundwater and cation exchange at the fresh saline water interface sds generally shows conservative mixing with fgw inspection of chemical data from coastal aquifers around the world indicates that intensive ion exchange in slightly diluted saline groundwater is a globally important phenomenon of seawater intrusion most of our saline groundwater samples contain substantial amounts of 3h suggesting that penetration of mediterranean seawater and its inland travel to a distance of 50 100 m onshore occurred 15 30 yr ago this is supported by the 14cdic mass balance that explains the relatively low 14cdic activities in the sds as influenced by diagenesis and not by simple radioactive decay

dissolution in a variably confined carbonate platform effects of allogenic runoff hydraulic damming of groundwater inputs and surface groundwater exchange at the basin scale in variably confined carbonate platforms impermeable confining units collect rainfall over large areas and deliver runoff to rivers or conduits in unconfined portions of platforms runoff can increase river stage or conduit heads in unconfined portions of platforms faster than local infiltration of rainfall can increase groundwater heads causing hydraulic gradients between rivers conduits and the aquifer to reverse gradient reversals cause flood waters to flow from rivers and conduits into the aquifer where they can dissolve limestone previous work on impacts of gradient reversals on dissolution has primarily emphasized individual caves and little research has been conducted at basin scales to address this gap in knowledge we used legacy data to assess how a gradient of aquifer confinement across the suwannee river basin north central florida affected locations magnitudes and processes of dissolution during 2005 2007 a period with extreme ranges of discharge during intense rain events runoff from the confining unit increased river stage above groundwater heads in unconfined portions of the platform hydraulically damming inputs of groundwater along a 200 km reach of river hydraulic damming allowed allogenic runoff with sical 4 to fill the entire river channel and flow into the aquifer via reversing springs storage of runoff in the aquifer decreased peak river discharges downstream and contributed to dissolution within the aquifer temporary storage of allogenic runoff in karst aquifers represents hyporheic exchange at a scale that is larger than found in streams flowing over non karst aquifers because conduits in karst aquifers extend the area available for exchange beyond river beds deep into aquifers post depositional porosity in variably confined carbonate platforms should thus be enhanced along rivers that originate on confining units this distribution should be considered in models of porosity distribution used to manage water and hydrocarbon resources in carbonate rocks copyright 2013 john wiley sons ltd

the youga gold deposit burkina faso the youga gold deposits are located in southern burkina faso close to the border with ghana and classified as epigenetic mesothermal orogenic type gold deposits they are hosted within or adjacent to tarkwaian type metasediments of the youga basin composed of a succession of arkosic sandstones conglomerates and subordinate chlorite schists the youga deposits are characterized by two distinct styles of mineralization the moderately to weakly silicified host rock with quartz stockwork veining and pyrite as the predominant sulphide which generally grades between 0 5 and 2 g t and the intensely silicified arkose with abundant quartz veins and more diverse sulphides pyrite arsenopyrite chalcopyrite pyrrhotite and galena which generally grades 3 g t the alteration paragenesis associated with the mineralized vein stockwork is characterized by quartz ankerite albite chlorite and pyrite the first mineralization episode occurred under brittle ductile conditions during the d1y deformation event characterized by e w trending penetrative to discrete structures gold is concentrated in zones affected by irregular fracturing quartz veining and occasional brecciation reworking of these structures during d2y by n s to ne trending sub vertical shear zones lead to further economic concentration of gold found in eight individual deposits all localized in or immediately adjacent to tarkwaian type sediments main east west zone 1 2 and 3 a2ne ntv and zergore absolute age of mineralization is unknown as well as that of the host sediments however stratigraphic and structural craton wide correlations suggest that the mineralization occurred after 2110 ma if not much later commercial production was achieved at the youga gold mine in 2008 and as of december 31st 2014 has produced 537 621 oz of gold

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

trigonal dendritic calcite crystals forming from hot spring waters at waikite north island new zealand amorphous silica and calcite form the deposits in the vent and on the discharge apron of waikite spring 100 ws 100 which is located in the waikite geothermal area on north island new zealand these precipitates formed from spring water that has a temperature of 90 c and a ph of 8 1 8 8 the opaline silica is restricted to areas around the vent where cooling and evaporation of the spring water triggered precipitation the calcite deposits in the spring vent and on the discharge apron are formed of large up to 15 cm long asymmetrical dendrite crystals that are characterized by multiple levels of branching branches grew preferentially from the downflow side of their parent branch all branches have a trigonal transverse cross section except in areas where competition for growth space induced merger of neighboring crystals the primary branches of the dendrite crystals are sub perpendicular to the substrate even in areas where the discharge apron slopes at a high angle up to 80 on the steeper parts of the discharge apron the plate like primary branches form the floors of the small terrace pools whereas their distal edges form the rims of the pools growth of these dendrite crystals is attributed to abiotic processes high levels of saturation with respect to calcite were caused by rapid co2 degassing of the sheets of spring water that flowed down the steep discharge apron calcite crystals with different crystal morphologies characterize other springs near this spring the variation in crystal morphologies from spring to spring is attributed to different levels of saturation that are related to the initial pco2 of the spring water upon discharge and the rate of co2 degassing at each spring

intrastratal rip down clasts late cretaceous uhangri formation southwest korea abstract black shale clasts of various sizes and shapes occur in some tuffaceous mudstone cherty mudstone and fine standstone beds in the uhangri formation the clasts include small fibrous shale chips and large disc forms 0 5 65 cm long and 0 1 mm 8 cm thick existence of large semidetached clasts in the upper part suggests that they were derived from the overlying bed rather than the underlying bed these clasts here termed rip down clasts were probably the result of liquefied intrastratal flow of tuffaceous and cherty muds and fine sand during penecontemporaneous deformation

carbonate dissolution in a modern mixing zone the potential for dissolution of calcite and aragonite and precipitation of dolomite by the mixing of fresh and saline ground waters has been demonstrated theoretically1 3 although geologists have used these processes in the explanation of the diagenesis of recent4 7 and ancient8 12 carbonates there has been only limited investigation of the geochemical processes of modern mixing zones13 14 here we report the results of chemical and rock profiling through a modern mixing zone on andros island in the bahamas our results demonstrate undersaturation of the waters in the mixing zone with respect to aragonite and calcite and corresponding pervasive dissolution of the carbonate rocks at this level undersaturation is significantly enhanced by bacterial processes which are also responsible for precipitation of an iron rich crust despite chemical supersaturation precipitation of dolomite was not observed thereby casting some doubt on the mixing zone model of dolomitization

the kalana vein hosted gold deposit southern mali abstract the kalana gold deposit occurs within metamorphosed paleoproterozoic volcano sedimentary series of the birimian baoule mossi domain of the west african craton in the south of mali these formations are intruded successively by small dioritic bodies as well as andesitic and tonalitic dykes which exhibit volcanic arc setting signatures mineralization is hosted by two sets of quartz veins that intersect the regional schistosity the first set of veins is the most important in terms of grades and size and consists of thick veins up to meter size that range in trend from n s to e w with shallow plunges the second set consists of much thinner centimeter size sub vertical quartz veins oriented ne sw the two sets of veins are interpreted to have formed during the evolution of late gently dipping thrust faulting two episodes of gold precipitation are recognized a first episode during early stages of vein growth formed micron size native gold inclusions in arsenopyrite a later episode during vein shearing and fracturing of the quartz lodes precipitated native gold in free form in quartz in fractured arsenopyrite and associated with chalcopyrite galena sphalerite bi sulfides and native bismuth all evidence suggests that the kalana deposit represents orogenic gold mineralization formed during a relatively long lived hydrothermal system at a late stage of the tectonic history of the greenstone belt

a new metamorphic constraint for the eburnean orogeny from paleoproterozoic formations of the man shield aribinda and tampelga countries burkina faso abstract progressive metamorphic zones developed in pelites around the aribinda granite burkina faso indicate contact metamorphism at 5 6 kbar biotite chloritoid staurolite kyanite zones are distributed concentrically around the aribinda pluton on its northern margin but are displaced by later thrust faults in the south of the aribinda area and in the nearly tampelga area these metamorphic and structural characteristics provide new constraints for the geodynamical evolution of the eburnean orogeny in the north part of the baoule mossi domain they show the leading part of the granitoid emplacement in the thermic structuration of the greenstone belts and the post metamorphic character of the tangential tectonic in burkina faso the eburnean orogeny underwent 1 initial greenschist facies metamorphism 2 emplacement of granitoids at mid deep crustal levels leading to unusual medium pressure metamorphism 3 later thrusting

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

multistage 8 2 kyr event revealed through high resolution xrf core scanning of cuban sinkhole sediments we use sediments from a flooded sinkhole cenote jennifer in northern cuba to provide new well dated high resolution evidence for the 8 2 kyr event from 7600 to 8700 cal yr b p the sinkhole contained shallow low salinity water which supported a marsh dominated by cattail and grass peaks in cl and br occurring at 8150 8200 and 8250 cal yr b p are attributable to increased evaporation due to regional drying associated with the 8 2 kyr event the three peaks in these elements also closely correspond to the greyscale record from the cariaco basin indicative of increased upwelling in the southern caribbean sea at this time supporting the notion of a multistage 8 2 kyr event our work provides new data that help to clarify the initiation behavior and impacts of the 8 2 kyr event in the northern tropics

a dated cave sediment record of pleistocene transgressions on berry head southwest england berry head a limestone headland in torbay southwest england exhibits a series of subaerial marine erosion platforms and raised beaches spanning an altitude range of 97 m solution caves on the headland show preferred horizontal development at elevations that are correlated with the marine erosion platforms and developed in a marine freshwater mixing zone whose position was controlled by high sea level still stands corbridge cave in berry head quarry lies below the raised beaches in torbay and contains evidence of three marine transgressions in the form of fine grained marine ponding deposits with a marine microfauna uranium series dating of intercalated speleothems indicates that a transgression during oxygen isotope stage 5e reached an elevation of 5 8 m od while an earlier transgression probably during stage 7 reached at least 7 2 m od these findings are used to constrain possible interpretations of the aminostratigraphy of raised beaches in southwest britain and a correlation of the unnamed stage of bowen sykes reeves miller andrews brew and hare with oxygen isotope stage 5e is proposed

steady state freshwater seawater mixing zone in stratified coastal aquifers summary the mixing zone between freshwater and intruding seawater which controls regional groundwater flow dynamics and reactive transport processes is the most important component in coastal aquifers laboratory experiments and numerical simulations were conducted to investigate the effects of aquifer stratification on the thickness of a steady state freshwater seawater mixing zone a series of experiments were implemented in a laboratory tank packed with three layers of coastal sands and manipulated by two flow cells for maintaining constant head boundary conditions packed aquifers included a homogenous aquifer a high hydraulic conductivity k low k high k stratified aquifer and a low k high k low k stratified aquifer both tank scale and field scale density dependent models were developed to simulate the laboratory experiments and to systematically investigate aquifer stratification effects on the thickness of a steady mixing zone with varying layer configurations results showed that when an aquifer layer with a low k overlies a layer with a relatively high k slanting upward flow of diluted saltwater and re circulated seawater flow are refracted at the interface between the two layers resulting in streamline separation and a broad mixing zone in the low k layer by contrast the mixing zone in a high k layer is slightly narrowed when it overlies a layer with a relatively low k because flow refraction squeezes the streamlines within the mixing zone the mixing zone profile in head controlled systems is a function of k contrast but independent of the magnitude of k our results demonstrated the significant impact of aquifer stratification on controlling groundwater flow and solute transport in coastal subsurface environments and would have significant implications for studying physical chemical and biological processes in coastal subsurface environments as aquifer stratification is naturally prevalent

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

re os geochronological evidence for multiple paleoproterozoic gold events at the scale of the west african craton the archean proterozoic craton of west africa hosts numerous gold deposits which are spatially and temporally related to the eburnean orogeny that took place between 2250 and 1980 ma and included multiple deformation events the majority of these gold deposits are located along shear zones the structural history is relatively well established for most gold deposits but absolute timing of the mineralization is commonly lacking five deposits hosted in the baoule mossi domain located in the southwestern part of the west african craton were studied to better constrain timing of gold events nassara and kiaka in burkina faso and wassa damang and obuasi in southern ghana gold mineralization was structurally characterized at each deposit and dated by the re os method on pyrite arsenopyrite and pyrrhotite grains that were coeval with the gold deposition combined structural and re os geochronological constraints allow two groups of gold deposits to be distinguished early orogenic gold formed during the eoeburnean orogeny i e between 2190 and 2125 ma as represented by kiaka1 at 2157 24 ma and wassa1 at 2164 14 ma these early gold occurrences are expressed as early disseminated gold enrichment 1 3 g t au at kiaka and gold hosted in folded and boudinaged quartz veins that are transposed along the primary s foliation at wassa these re os ages on the early sulfides at wassa and kiaka are significant because they definitively provide the first direct age constraints on gold only eoeburnean mineralization in the birimian of west africa late orogenic gold hosted by brittle structures and with higher gold grades up to 60g t at kiaka formed during late eburnean deformation d d events between 2120 and 2000 ma as represented by the re os dating of these ores at wassa at 2055 18 ma and obuasi at 2045 40 ma similar style ores dated at nassara at 2131 99 ma and damang at 2080 135 ma but both with large uncertainties and an undated younger event at kiaka are also suggested to be part of this later mineralizing episode the high uncertainties on the nassara and damang ages may be directly linked to the low rhenium and osmium contents of the studied samples these results highlight the polyphase character of the widespread gold mineralization in the west african craton although the late stages of the eburnean orogeny constitute a prolific period for the formation of high grade gold mineralization identification of less well studied early stage gold deposits which can also contain large quantities of gold is critical for mineral exploration in the west african craton

selective blackening of bioclasts via mixing zone aragonite neomorphism in late triassic limestone zlatibor mountains serbia a peculiar facies of the norian rhaetian dachstein type platform carbonates which contains large amounts of blackened bioclasts and dissolutional cavities filled by cements and internal sediments occurs in the zlatibor mountains serbia microfacies investigations revealed that the blackened bioclasts are predominantly solenoporaceae with a finely crystalline originally aragonite skeleton of fine cellular structure blackening of other bioclasts also occurs subordinately solenoporacean dominated reefs developed behind the platform margin patch reef tract were the main source of sand sized detritus the blackened and other non blackened bioclasts are incorporated in automicrite cement radiaxial fibrous calcite cements in the dissolutional cavities are also black dark grey or white reworked black pebbles were reported from many occurrences of peritidal deposits in those cases the blackening took place under pedogenic meteoric diagenetic conditions in contrast in the inner platform deposits of the ilidz ya limestone the blackening of bioclasts occurred in a marine meteoric mixing zone as indicated by petrographic features and geochemical data of the skeleton replacing calcite crystals attributes of mixingzone pore waters were controlled by mixing corrosion different solubility of carbonate minerals and microbial decomposition of organic matter in the moderate energy inner platform environment large amounts of microbial organic tissue were accumulated and subsequently decomposed triggering selective blackening in the course of early shallow burial diagenesis the d 18 o and d 13 c values of the mixing zone precipitates and replacive calcite do not produce a linear mixing trend variation mainly resulted from microbial decomposition of organic matter that occurred under mixing zone conditions the paragenetic sequence implies cyclic diagenetic conditions that were determined by marine meteoric and mixing zone pore fluids the diagenetic cycles were controlled by sea level fluctuations of moderate amplitude under a semi arid to semi humid climate

physical and chemical stratigraphy suggest small or absent glacioeustatic variation during formation of the paradox basin cyclothems the paradox basin cyclothems previously have been interpreted as milankovitch style glacial interglacial cycles from the late paleozoic ice age but an unambiguous test for a glacioeustatic origin has not been conducted a high resolution coupled chemical and physical stratigraphic analysis of two outcrop sections and three core segments provides new evidence that supports either minor sea level change of several meters or an autocyclic mechanism for parasequence formation high amplitude sea level change is ruled out by the scale of thin top negative isotopic meteoric diagenesis trends associated with parasequence tops and subaerial exposure fabrics isotopic gradients from shelf light to basin heavy indicate that parasequences are deposited diachronously with isotopes of more distal sections recording increased basin restriction these results support the idea that the late pennsylvanian was a prolonged period of relatively static eustasy agreeing with recent studies in the western usa the methods provide a new set of tools and context for extracting environmental information from cyclic upward shallowing carbonate parasequences

analysis of the acceleration phase of a theropod dinosaur based on a cretaceous trackway from korea abstract well preserved trackways of carnivorous dinosaurs belonging to small sized theropods have been reported from the cretaceous neungju group in south korea the site at hwasun seoyu ri quarry represents the most extensive and diverse theropod trackway ichnofauna in south korea among them one theropod trackway is unique in that it demonstrates that theropods were able to increase stride lengths to reach maximum speed during the running phase fossilized track evidence of the acceleration ability of dinosaurs is scant despite this the evidence shown in our findings suggests a theropod running near the limit of its capabilities and shows evidence of a temporary acceleration of speed while running

sea level and deep water temperature changes derived from benthic foraminifera isotopic records we show that robust regressions can be established between relative sea level rsl data and benthic foraminifera oxygen isotopic ratios from the north atlantic and equatorial pacific ocean over the last climatic cycle we then apply these regressions to long benthic isotopic records retrieved at one north atlantic and one equatorial pacific site to build a composite rsl curve as well as the associated confidence interval over the last four climatic cycles our proposed reconstruction of rsl is in good agreement with the sparse rsl data available prior to the last climatic cycle we compute bottom water temperature changes at the two sites and at one southern indian ocean site taking into account potential variations in north atlantic local deep water 18o our results indicate that a last glacial maximum lgm enrichment of the ocean mean oxygen isotopic ratio of 0 95 is the lowest value compatible with unfrozen deep waters in the southern indian ocean if local deep water 18o did not increase during glacials with respect to present such a value of the lgm mean ocean isotopic enrichment would impose a maximum decrease in local bottom water 18o at the north atlantic site of 0 30 during glacials

relationship of clathrate instability to sediment deformation in the upper neogene of california widespread soft sediment deformation ssd in upper bathyal continental margin sediments has been explained by compaction related dewatering and related physical processes that can destabilize margin sediments we present the hypothesis that ssd in such facies resulted in part from instability of gas hydrates clathrates leading to overpressurization in sediments and resulting fluid flow and brecciation clathrate related deformation must be widespread in upper bathyal continental margin methanogenic sequences at depths where clathrates are destabilized by changes in bottom water temperatures and sea level a close association exists between an array of ssd features with clathrate hosting sediments in ocean drill cores similar features are conspicuous in the partly laminated upper neogene upper bathyal sediments of the sisquoc formation in southern california suggesting that clathrates may have been responsible for abundant and well developed ssd in these units the lithology methane producing organic content and depositional environment of the sisquoc formation are similar to those features in modern clathrate hosting settings these characteristics in conjunction with the upper bathyal paleobathymetry of the unit the geothermal gradient of the region and 13 c values of benthic foraminifera and dolomite concretions suggest the occurrence of clathrates in the shallow subsurface of these sediments we suggest that the analyzed parts of the sisquoc formation represent an exhumed zone of ssd resulting from clathrate instability in the shallow subsurface of the continental margin sedimentary rocks exhibiting an association of ssd features that resulted from clathrate formation and dissociation are named clathrites

geologic and environmental aspects of surface cementation north coast yucatan mexico the northernmost part of the fresh water aquifer of yucatan mexico is confined near the coast by a thin flat nearly impermeable calcareous layer the authors think it probable that this confining layer is now developing by a process of sedimentation and precipitation of pore filling cement on and near the surface of older limestone at the landward margin of the swamp that extends virtually continuously along the north yucatan coast it is their interpretation that this caco sub 3 cemented layer which is 0 5 to 1 4 m thick developed in the zone of discharge of the fresh water aquifer the presence of sup 14 c 6 0 plus minus 0 4 modern carbon in a sample of aquitard supports the hypothesis that cementation is an ongoing process further support comes from the remarkable regularity between modern mean sea level and the elevation of the landward boundary between the confining zone and normal karst along 250 km of coast confinement of the aquifer produces an elevation of the piezometric surface to about 0 5 m above mean sea level and a concurrent depression of the fresh water salt water interface to an estimated depth of about 18 m below mean sea level at the coast breaching of the confining layer implicit inmore some development schemes for the region could dramatically decrease the thickness of the fresh water lens a valuable water resource the mixing zone beneath the confined part of the aquifer is a chemically active volume that may be vigorously pumped by tides as evidenced by increased salinity of ground water near the coast thus making this zone a likely place for rock water interaction including perhaps dolomite formation less

the inata deposit belahouro district northern burkina faso the inata gold deposit is hosted in the bouroum greenstone belt of northern burkina faso and contains ca 5 moz of gold resource the greenstone belt is divided into 4 distinct domains the pali west pali minfo and fete kole domains comprised of variable proportions of mafic to intermediated volcanic volcaniclastic and sedimentary rocks and the sona basin comprised of feldspathic sandstones and turbidites potential tarkwaian like conglomerates are rarely observed on the eastern margin of the basin the stratigraphy is crosscut by a series of intrusions between 2172 15 ma and 2122 4 ma a complex deformation sequence is recorded in the rocks and has been interpreted in a five stage scheme early syn depositional basin margin faults reactivated through time and partitioning all subsequent regional deformation deb n s compression d1b 2172 ma e w compression d2b ca 2122 ma nw se compression d3b and a late n s compression d4b d2b d4b overprint all rocks including those of the sona basin and tarkwaian like conglomerates peak metamorphism is mid to upper greenschist facies mineralisation at inata is hosted in black shales and volcaniclastic rocks of the pali minfo domain and comprises shear zone hosted quartz tourmaline ankerite veins with associated sulphides dominated by pyrite and arsenopyrite three generations of pyrite py1 py2 py3 and one generation of arsenopyrite apy2 have been identified py1 is parallel to bedding and early d1b foliation and not associated with gold py2 and apy2 are coeval contain up to 1 ppm gold and are spatially associated with auriferous quartz veins py3 locally overprints previous assemblages and is also associated with au fluid inclusions in quartz indicate h2o to h2o co2 nacl fluids in auriferous quartz veins microscopic to macroscopic observation of fabric mineral vein crosscutting relationships indicate that mineralisation is syn d2b disrupted and remobilised during d3b all observations and data are consistent with inata representing an orogenic style of gold mineralisation formed relatively late in the evolution of the host terrane