late pleistocene sea level change in the bahamas from mass spectrometric u series dating of submerged speleothem abstract the dating of sea level events by a method independent of orbital tuning techniques and the marine foraminiferal isotopic record provides a test of both the dating of the marine record and the strength and nature of the relationship between climatic change sea level change and milankovitch cycles dating of fossil corals and submerged speleothem provides such independent information results of thermal ionization mass spectrometric u series dating on layers of flowstone speleothem from lucayan caverns grand bahama island indicate that multiple sea level events have passed through a depth of 10 to 15 m below modern sea level during the last 300 000 years these data are used to constrain the magnitude and timing of sea level fluctuations during the late pleistocene the new sea level curve constructed from these data correlates closely with the marine isotopic record sea level peaks occurred at around 233 215 125 and 100 ka bp there is no evidence at the depth from which this speleothem was retrieved of any high sea stands at 195 or 80 ka corresponding to the foraminiferal 7a and 5a oxygen isotope peaks there is also no evidence of a double rise around the 125 ka 5e peak although such an oscillation could have occurred above 10 m leaving no record in the lucayan caverns speleothem

the flank margin model for dissolution cave development in carbonate platforms the bahama islands contain many abandoned dissolution caves at elevations between two and seven metres above current sea level the development of dissolution caves in tropical carbonate islands is dependent on the position and nature of the freshwater lens lens position is controlled by sea level which in stable carbonate platforms like the bahamas is a function of glacioeustatic sea level still stands caves in the bahamas that are currently subaerial must have developed during past higher sea levels during the late quaternary sea levels higher than present have been relatively short lived and that limits the amount of time that a freshwater lens could be situated at the elevation required for the cave formation the bahama islands are low lying landforms where only aeolian ridges extend to elevations higher than six metres above current sea level past high sea level events greatly reduced the exposed land area of the bahama islands thus also limiting both the catchment for and size of freshwater lenses caves must be younger than the rock in which they are developed most subaerial bahamian caves are found in limestones that are less than 150000 years old development of large dissolution caves under these limitations of time and lens size requires a powerful dissolutional mechanism the mixing of discharging freshwater with tide pulsed incoming marine water under the flanks of emergent dune ridges may have produced the conditions necessary bahamian caves formed by this process are phreatic chambers with complex interconnections and blind tubes their presence demonstrates that significant dissolution can occur rapidly as a result of the mixing of fresh and marine waters beneath small carbonate islands

selective dissolution of magnetic iron oxides with the acid ammonium oxalate ferrous iron extraction technique ii natural loess and palaeosol samples summary chemical extraction techniques are being introduced into environmental magnetism studies to aid in the interpretation of magnetic climate proxies previous studies have shown that the acid ammonium oxalate ferrous iron aao fe 2 extraction technique can be used to selectively dissolve very fine grained magnetite and maghemite from synthetic samples here we present the results of a study of this extraction technique to serve as a tool for selective dissolution of pedogenic magnetic minerals from a loess palaeosol transect before and after extraction the samples were subjected to classic mineral magnetic methods measurement of low field susceptibility and hysteresis parameters as well as first order reversal curve analysis in addition acquisition curves of the isothermal remnant magnetization irm were fitted with logarithmic distributions these analyses showed the magnetic dominance of lowcoercivity magnetic minerals by subtracting the irm remaining after extraction from that before extraction the magnetic fraction that was dissolved could be characterized as well supplying extra information concerning the performance of the extraction technique the aao fe 2 method successfully dissolved the superparamagnetic and part of the singledomain material from the palaeosol samples in one extraction step repeating the extraction resulted in hardly any further changes to the magnetic content of the samples the magnetic characteristics of the loess samples remained stable throughout the extraction experiment the combination of the aao fe 2 extraction with mineral magnetic analysis has successfully identified the pedogenic contribution in our samples therefore variations in the lithogenic fraction potentially present in pedogenically enhanced intervals can be assessed improving the merit of mineral magnetic climate proxy parameters

the nature of crater rays the copernicus example crater rays are formed during a cratering event as target material is ballistically ejected to distances of many crater radii forming narrow generally high albedo approximately linear features extending outward from the crater the nature of crater rays was examined for the lunar crater copernicus using new information on the composition of surface material from near ir reflectance measurements surface roughness from radar backscatter measurements and photogeologic data from available images part of the data analysis included use of mixing models to quantify the mixing systematics observed between primary ejecta and local substrate of the ray on the basis of compositional parameters from reflectance spectra primary material from copernicus can be detected in the surface material of rays in decreasing amounts with increasing radial distance e g 20 25 primary ejecta at six crater radii for distances greater than three crater radii the proportion of local material to primary ejecta observed from these compositional reflectance data is approximately equal to that predicted by previous laboratory and ballistic studies of craters within three crater radii the compositional data indicate a higher proportion of primary ejecta than predicted for extended areas along the ray that do not contain large secondary craters the primary ejecta is intimately mixed on the granular scale with local material throughout the regolith the relatively high albedo of the rays of copernicus is due to the feldspathic composition highland of the primary ejecta in rays emplaced on a mare substrate immature local substrate is only observed in copernicus s ray at large unmantied secondary craters or other areas with sufficient topographic slope to prevent the accumulation of mature soils crater rays are filamentous generally high albedo features that emanate nearly radially from young impact structures rays are narrow in relation to the crater radius extend distally for many crater radii and constitute a distinctive albedo feature around some of the largest and freshest lunar craters visible from earth synoptic views of ray systems figure la give the strong impression that the rays comprise bright material that has been excavated from the crater cavity and been emplaced beyond the continuous ejecta deposit if this visual impression is correct then the process that forms crater rays represents a significant mechanism for the lateral transport of primary material to great distances from its point of origin and particularly for craters larger than a let tens of kilometers in diameter constitutes a fundamental process for the regional mixing of crustal materials earth based telescopic images of the moon allowed the first studies and descriptions of rays and ray systems shoemaker 1962 described the arcuate and loop shaped streaks of the copernicus ray systems and showed that these patterns could be locally resolved into individual en echelon feather shaped elements 15 20 km in length with their long axes oriented approximately radially to the crater he noted the presence of elongate depressions or gouges in the ray system ranking in diameter from 8 km down to the limits of resolution and generally located at the proximal ends of the individual ray elements shoemaker observed that some of the gouges were

a new chronology for the middle to late miocene continental record in spain abstract the first detailed chronology for the middle to late miocene continental record in spain is presented based on high resolution magnetostratigraphic data of mammal bearing sections which were studied in several basins calatayud daroca teruel valles penedes duero and jucar cabriel our results indicate that these sections compose an almost complete magnetostratigraphic succession from the lower aragonian mn4 to the middle turolian mn12 seven successive mammal neogene mn zone boundaries are directly dated in these sections which often contain faunas of two successive zones in superposition the three oldest boundaries are dated in the aragonian type area calatayud daroca basin the mn4 mn5 boundary vargas section occurs in chron c5cr o with a corresponding age of 17 26 0 01 ma the mn5 mn6 boundary aragon section in chron c5acn 0 8 with an age of 13 75 0 03 ma and the mn6 mn7 8 boundary aragon section in the interval c5ar 1n c5ar 3r with an age of 12 75 0 25 ma the mn7 8 mn9 aragonian vallesian boundary occurring in chron c5r 1n at 11 1 ma and the mn9 mn10 boundary in chron c4ar 3r at 9 7 0 1 ma are recorded in the valles penedes basin vallesian type area and are supported by the results from the duero basin torremormojon section in the turolian type area teruel basin the mn10 mn11 vallesian turolian boundary la gloria section occurs in chron c4an y at 8 7 0 1 ma taking into account the pre existing data from the jucar cabriel basin the mn11 mn12 boundary cabriel valley section is recalibrated to c4n 1n at an age of 7 5 0 1 ma

modelled atmospheric temperatures and global sea levels over the past million years the climate has passed through a series of glacials and interglacials over the past million years but the nature of this cyclicity in terms of temperature ice volume and sea level and the underlying causes are not well known bintanja et al use a new method to deduce a one million year time series of these variables the reconstructed records are much longer than other methods have provided for any of these variables individually the most intense glacial stages were 17 c colder than today and most of the continental ice was present in north america strong cooling in the beginning of glacials was found to precede ice sheet build up these findings may shed light on the causes of ice age cycles marine records of sediment oxygen isotope compositions show that the earth s climate has gone through a succession of glacial and interglacial periods during the past million years but the interpretation of the oxygen isotope records is complicated because both isotope storage in ice sheets and deep water temperature affect the recorded isotopic composition1 2 3 4 5 separating these two effects would require long records of either sea level or deep ocean temperature which are currently not available here we use a coupled model of the northern hemisphere ice sheets6 and ocean temperatures forced to match an oxygen isotope record for the past million years compiled from 57 globally distributed sediment cores to quantify both contributions simultaneously we find that the ice sheet contribution to the variability in oxygen isotope composition varied from ten per cent in the beginning of glacial periods to sixty per cent at glacial maxima suggesting that strong ocean cooling preceded slow ice sheet build up the model yields mutually consistent time series of continental mean surface temperatures between 40 and 80 n ice volume and global sea level we find that during extreme glacial stages air temperatures were 17 1 8 c lower than present with a 120 10 m sea level equivalent of continental ice present

early last glacial intra interstadial climate variability recorded in a sardinian speleothem chemical and physical proxy data from a precisely dated early last glacial 113 110 ka mis5d sardinian stalagmite reveal a sub millennial scale cool dry climate event centered at 112 0 0 52 0 59 ka followed by a rapid return to warm wet conditions at 111 76 0 43 0 45 ka comparison with regional speleothem records and the palaeotemperature proxy record from the ngrip ice core greenland suggests that this event corresponds to greenland interstadial gi 25b and 25a an intra interstadial climate oscillation within gi 25 according to the recent greenland stratigraphic framework the speleothem age is in reasonable agreement within 0 8 kyr with that of the corresponding event in greenland based on the gicc05modelext ice chronology but is older by about 3 7 kyr than the greenland age based on the aicc2012 chronology

constraining holocene sea levels using u th ages of phreatic overgrowths on speleothems from coastal caves in mallorca western mediterranean phreatic overgrowths on speleothems pos are carbonate formations deposited at the water table of caves in unique karstic coastal settings having morphologies that can be directly related to sea level at the time of formation the u th ages of calcite and aragonite overgrowths collected from the modern water table in coastal caves on mallorca cova de cala varques a and cova des pas de vallgornera were determined using high precision mc icpms techniques u th ages indicate that phreatic carbonate deposition occurred between ca 2 8 and at least 0 6 ka bp and are in accord with an archeologically estimated age of 3 7 3 0 ka bp for a drowned prehistoric construction at a depth of 1 m below current sea level in a cave from the same area speleothem 13c and 18o and chemical composition of cave pools provide supportive evidence that pos reflect mixing between seawater and brackish water table copyright 2010 john wiley sons ltd

tidal notches in mediterranean sea a comprehensive analysis abstract recent works evelpidou et al 2012 suggest that the modern tidal notch is disappearing worldwide due sea level rise over the last century in order to assess this hypothesis we measured modern tidal notches in several of sites along the mediterranean coasts we report observations on tidal notches cut along carbonate coasts from 73 sites from italy france croatia montenegro greece malta and spain plus additional observations carried outside the mediterranean at each site we measured notch width and depth and we described the characteristics of the biological rim at the base of the notch we correlated these parameters with wave energy tide gauge datasets and rock lithology our results suggest that considering the development of tidal notches the consequence of midlittoral bioerosion as done in evelpidou et al 2012 is a simplification that can lead to misleading results such as stating that notches are disappearing important roles in notch formation can be also played by wave action rate of karst dissolution salt weathering and wetting and drying cycles of course notch formation can be augmented and favoured also by bioerosion which can in particular cases be the main process of notch formation and development our dataset shows that notches are carved by an ensemble rather than by a single process both today and in the past and that it is difficult if not impossible to disentangle them and establish which one is prevailing we therefore show that tidal notches are still forming challenging the hypothesis that sea level rise has drowned them

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

230th u dating of last interglacial brain corals from bonaire southern caribbean using bulk and theca wall material abstract we compared the suitability of two skeletal materials of the atlantic brain coral diploria strigosa for 230th u dating the commonly used bulk material comprising all skeletal elements and the denser theca wall material eight fossil corals of presumably last interglacial age from bonaire southern caribbean sea were investigated and several sub samples were dated from each coral for four corals both the ages and the activity ratios of the bulk material and theca wall agree within uncertainty three corals show significantly older ages for their bulk material than for their theca wall material as well as substantially elevated 232th content and 230th 238u ratios the bulk material samples of another coral show younger ages and lower 230th 238u ratios than the corresponding theca wall samples this coral also contains a considerable amount of 232th the application of the available open system models developed to account for post depositional diagenetic effects in corals shows that none of the models can successfully be applied to the bonaire corals the most likely explanation for this observation is that the assumptions of the models are not fulfilled by our data set comparison of the theca wall and bulk material data enables us to obtain information about the open system processes that affected the corals the corals showing apparently older ages for their bulk material were probably affected by contamination with a secondary detrital phase the most likely source of the detrital material is carbonate sand the higher 230th 232th ratio of this material implies that detrital contamination would have a much stronger impact on the ages than a contaminant with a bulk earth 230th 232th ratio and that the threshold for the commonly applied 232th reliability criterion would be much lower than the generally used value of 1 ng g 1 the coral showing apparently younger ages for its bulk material was probably influenced by more than one diagenetic process a potential scenario is a combination of detrital contamination and u addition by secondary pore infillings our results show that the dense theca wall material of d strigosa is generally less affected by post depositional open system behaviour and better suited for 230th u dating than the bulk material this is also obvious from the fact that all ages of theca wall material reflect a last interglacial origin 125 ka whereas the bulk material samples are either substantially older or younger however for some corals the 230th u ages and activity ratios of the bulk material and the theca wall samples are similar this shows that strictly reliable 230th u ages can also be obtained from bulk material samples of exceptionally well preserved corals however the bulk material samples more frequently show elevated activity ratios and ages than the corresponding theca wall samples our findings should be generally applicable to brain corals mussidae that are found in tropical oceans worldwide and may enable reliable 230th u dating of fossil corals with similar skeletal architecture even if their bulk skeleton is altered by diagenesis the 230th u ages we consider reliable 120 130 ka along with a recently published age of 118 ka provide the first comprehensive dating of the elevated lower reef terrace at bonaire 118 130 ka which is in agreement in timing and duration with other last interglacial records

mass spectrometric 230th 234u 238u dating of the devils hole calcite vein the devils hole calcite vein contains a long term climatic record but requires accurate chronologic control for its interpretation mass spectrometric u series ages for samples from core dh 11 yielded 230 th ages with precisions ranging from less than 1 000 years 2 for samples younger than 140 ka thousands of years ago to less than 50 000 years for the oldest samples 566 ka the 234 u 238 u ages could be determined to a precision of 20 000 years for all ages calcite accumulated continuously from 566 ka until 60 ka at an average rate of 0 7 millimeter per 10 3 years the precise agreement between replicte analyses and the concordance of the 230 th 238 u 234 u 238 u ages for the oldest samples indicate that the dh 11 samples were closed systems and validate the dating technique in general

a 20 m middle pleistocene sea level highstand bermuda and the bahamas due to partial collapse of antarctic ice marine deposits at 20 3 m on the tectonically stable coastlines of bermuda and the bahamas support the hypothesis of a partial collapse of the antarctic ice sheet during the middle pleistocene beach sediments fill a sea cave at 22 m in bermuda and horizontal fenestrae filled beds crop out on platforms at two sites as high as 21 m in eleuthera bahamas carbonate beach sands are bound by an early generation of isopachous fibrous cement that is characteristic of a phreatic marine environment amino acid racemization and tims thermal ionization mass spectrometry dates constrain the age of the deposits to between 390 and 550 ka while proxy evidence supports a correlation with oxygen isotope stage 11 this direct geologic evidence of a 20 decrease in polar ice during the middle pleistocene has important implications for the stability of ice sheets during warm interglaciations

coastal uplift rate at matanzas cuba inferred from mis5e phreatic overgrowths on speleothems many morphological elements in cuba s landscape e g marine terraces tidal notches demonstrate that coastal uplift has taken place but the rate at which this occurs is not known carbonate phreatic overgrowths on speleothems have been found in a cave in central north cuba 1 km from the present coastline at 16 m asl they form exceptional and unique mushroom shaped speleothems and balconies decorating the walls of the rooms these phreatic overgrowths on speleothems pos formed at the oscillating air water interface in sea level controlled anchialine lakes u th dating of these overgrowths suggests ages that are compatible with the marine isotope stage 5e i e 130 115 ka these pos have fixed this sea level highstand and demonstrate that this part of cuba has been subjected to a much lower uplift rate than previously reported i e less than 0 1 mm a 1 since the last interglacial this article is protected by copyright all rights reserved

tidal notches a sea level indicator of uncertain archival trustworthiness abstract in this paper after a short summary on the processes and rates of bioerosion that contribute to the deepening of a tidal notch profile some mediterranean case studies are presented where a tidal notch is prevented either from forming or from being preserved furthermore as shown also in a complementary paper the recent global sea level rise is preventing the development of new tidal notches in the present mid littoral zone this very useful sea level indicator of past temporary standstills of the relative sea level in carbonate rock areas is of great value in assisting interpretations of relative sea level change in locations where it is preserved the possibilities of absence of formation or of preservation however imply that it should be interpreted carefully before reconstructing local relative sea level histories in particular the lack of fossil tidal notches cannot be relied upon to interpret the absence of past periods of relative sea level stabilization

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

genesis of folia in a non thermal epigenic cave matanzas cuba abstract folia are an unusual speleothem type resembling inverted cups or bracket fungi the mechanism of folia formation is not fully understood and is the subject of an ongoing debate this study focuses on an occurrence of folia present in santa catalina cave a non thermal epigenic cave located close to matanzas cuba the sedimentology morphology petrology permeability and geochemistry of these folia have been studied to gain new insight on the processes leading to their development it is concluded that folia in santa catalina cave formed at the top of a fluctuating water body through co2 degassing or evaporation which may have been enhanced by the proximity to cave entrances two observations strongly support our conclusions 1 when compared to other subaqueous speleothems e g cave clouds present in the same rooms folia occur exclusively within a limited vertical interval that likely represents an ancient water level folia occur together with calcite rafts and tower cones that developed respectively on top of and below the water level this suggests that a fluctuating interface is required for folia formation 2 the measured permeability of the folia is too high to trap gas bubbles thus in contrast to what has been proposed in other studies trapped bubbles of co2 cannot be invoked as the key factor determining the genesis and morphology of folia in this subaqueous environment

sea level oscillations during the last interglacial highstand recorded by bahamas corals whether sea level was stable during the last interglacial remains a subject of debate an analysis of the u th ages of coral reefs in the bahamas corrected for open system behaviour confirms the presence of at least one oscillation within the sea level highstand

late quaternary sea level position evidence from bahamian carbonate deposition and dissolution cycles abstract the bahama islands offer a unique opportunity to examine late quaternary sea level position as the island group places significant constraints on the time and space boundary conditions for climatic events recorded there the bahamian archipelago extends as a series of large and small islands on shallow carbonate banks of various sizes for 1400 km across a climatic gradient wet in the northwest to dry in the southeast the entire island group is tectonically stable and consists solely of quaternary carbonate sediments with interspersed paleosols the islands reflect glacioeustatic sea level highstand positions in their eolian and subtidal suite of limestones a depositional record of platform flooding and carbonate sediment production a coeval record of phreatic cave development in the island s fresh water lenses also documents sea level highstand positions absolute dating of late pleistocene fossil corals and cave stalagmites by u th methods has produced an excellent record of the last interglacial marine isotope substage mis 5e holocene eolianites have been dated by 14 c to reveal platform flooding at 5000 ybp and sea level stabilization at 3000 ybp pleistocene eolianites have been dated by amino acid racemization analysis but subdivisons of the eolianites into separate mis 5a 5c and 5e deposits are controversial paleosols representing integrated aerosol dust deposition of 100 ka long platform exposure events during glaciations have been differentiated by paleomagnetic secular variation measurements previous interpretations of a beach unit to indicate a 20 m mis stage 11 sea level highstand and of large boulders to represent a mega tsunami appear to be incorrect phreatic caves in today s subaerial environment have been ascribed to mis 5e but some may have formed earlier carbonate deposition and dissolution cycles create a mass flux of co 2 sufficient to explain the atmospheric co 2 excursions of the quaternary

how precise are u series coral ages abstract u series dating of fossil reef corals is a well established and widely applied technique in paleoclimate research many fossil corals however show evidence for post depositional diagenetic alteration and it is generally accepted that the accuracy of u series coral ages is more limited due to coral diagenesis than analytical precision in recent years three models have been published that try to correct the effects of diagenesis and allow the calculation of model ages thompson w g spiegelmann m w goldstein s l and speed r c 2003 an open system model for u series age determinations of fossil corals earth and planetary science letters 210 365 381 villemant b and feuillet n 2003 dating open systems by the 238u 234u 230th method application to quaternary reef terraces earth and planetary science letters 210 105 118 scholz d mangini a and felis t 2004 u series dating of diagenetically altered fossil reef corals earth and planetary science letters 218 163 178 here we assess the age variability of both conventional 230th u dating and the three models by application to different sub samples of individual coral specimens the age variability estimated as the 2 standard deviation on the individual ages is compared with the errors quoted by the different methods our results show that the errors of conventional 230th u dating as well as those of the method of thompson et al 2003 do not account for the true age variability the age variability of both methods is in the range of the errors given by the models of villemant and feuillet 2003 and scholz et al 2004 furthermore we show that the widely used reliability criteria are not sufficient to identify all diagenetically altered corals in contrast analysis of different sub samples of one coral specimen allows i to estimate the real age variability ii to test if the assumptions of the models are fulfilled and iii to investigate the diagenetic processes in more detail thus this method should generally be applied to obtain more reliable u series coral ages and errors

esr and u th dating results for last interglacial coral reef terraces at the northern coast of cuba abstract fossil coral reef terraces at the northern coast of cuba in the vicinity of the bay of matanzas are forming a prominent flight of terraces these terraces were already studied by several investigators but a chronological classification based on numerical dating is still missing in this study we focus on the lowest unit the seboruco terrace which is assumed to be of mis 5e age the morphology of the seboruco terrace and associated sea level markers reef crests and notches were mapped and their altitude was measured over the whole study area in the field and by using remote sensing the fossil corals building up the terrace were surveyed in numerous natural outcrops the species of the fossil coral reefs were determined and subdivided in different facies zones fossil corals were taken for numerical dating by electron spin resonance esr and uranium series u th to establish a chronology of the mis 5e coral reef formation both dating techniques yielded age results in good agreement with each other and the stratigraphic context corresponding to the field evidence the age data indicates one mis 5e sea level highstand around 126 ka some younger esr ages may be explained by the recrystallization of aragonitic corals and or by u leaching at one locality east of matanzas the radiometric results for an underlying coral reef body suggest an mis 7 age the sea level markers for the mis 5e highstand range from 5 5 m a s l reef crest to a maximum of 7 m notches west of the bay of matanzas resulting in relatively low uplift rates of 0 003 m ka and 0 036 m ka when applying early mis 5e sea level estimates from tectonically stable coasts in the caribbean between 2 5 m and 6 6 m inside the bay of matanzas itself the elevation of sea level markers increases to more than 10 m a s l indicating a stronger uplift rate of 0 027 m ka to 0 060 m ka here

ice volume and sea level during the last interglacial during the last interglacial period 125 000 years ago sea level was at least several meters higher than at present with substantial variability observed for peak sea level at geographically diverse sites speculation that the west antarctic ice sheet collapsed during the last interglacial period has drawn particular interest to understanding climate and ice sheet dynamics during this time interval we provide an internally consistent database of coral u th ages to assess last interglacial sea level observations in the context of isostatic modeling and stratigraphic evidence these data indicate that global eustatic sea level peaked 5 5 to 9 meters above present sea level requiring smaller ice sheets in both greenland and antarctica relative to today and indicating strong sea level sensitivity to small changes in radiative forcing

a sustained 21 m sea level highstand during mis 11 400 ka direct fossil and sedimentary evidence from bermuda abstract a small protected karstic feature exposed in a limestone quarry in bermuda preserved abundant sedimentary and biogenic materials documenting a transgressive phase still stand and regressive phase of a sea level in excess of 21 3 m above present during marine isotope stage mis 11 400 ka as determined by u th dating and amino acid racemization cobbles and marine sediments deposited during the high energy transgressive phase exhibit rim cements indicating a subsequent phreatic environment this was succeeded stratigraphically by a still stand deposition of fine calcareous lagoonal sediments containing bioclasts of red algae and benthic and planktonic foraminifera that was intensely burrowed by marine invertebrates probably upogebiid shrimp that could not be produced under any condition other than sustained marine submergence overlying this were pure carbonate beach sands of a low energy regressive phase containing abundant remains of terrestrial and marine vertebrates and invertebrates the considerable diversity of this fauna along with taphonomic evidence from seabird remains indicates deposition by high run up waves over a minimum duration of months if not years the maximum duration has yet to be determined but probably did not exceed one or two thousand years the most abundant snails in this fauna are two species indicative of brackish water and high tide line showing that a ghyben herzberg lens must have existed at 20 m the nature of these sediments and fossil accumulation is incompatible with tsunami deposition and given the absence of evidence for tectonic uplift of the bermuda pedestal or platform provide proof that sea level during mis 11 exceeded 20 m a fact that has widespread ramifications for geologists biogeographers and human demographics along the world s coastlines

palaeo climate reconstruction from stable isotope variations in speleothems a review abstract speleothems are now regarded as valuable archives of climatic conditions on the continents offering a number of advantages relative to other continental climate proxy recorders such as lake sediments and peat cores they are ideal materials for precise u series dating yielding ages in calendar years thereby circumventing the radiocarbon calibration problems associated with most other continental records stable isotope studies in speleothems have shifted away from attempting to provide palaeo temperature reconstructions to the attainable goal of providing precise estimates for the timing and duration of major o isotope defined climatic events characterised by high signal to noise ratios e g glacial interglacial transitions dansgaard oeschger oscillations the 8200 year event unlike the marine records speleothem data sets are not tuned and their independent chronology offers opportunities to critically assess leads and lags in the climate system that in turn can provide important insights into forcing and feedback mechanisms improved procedures for the extraction and measurement of stable isotope ratios in fluid inclusions trapped in speleothems are likely to provide in the near future a much enhanced basis for the quantitative interpretation of o isotope ratios in speleothem calcite the latter developments open up once again the tantalising prospect of palaeo temperature estimates but more importantly perhaps provide a direct test for a new generation of general circulation models whose hydrological cycles will incorporate the water isotopes the literature is reviewed briefly to provide for the reader a sense of the current state of the art and to provide some pointers for future research directions

light attenuation as a control for microbiogeomorphic features implications for coastal cave speleogenesis san salvador bahamas is a carbonate island with dozens of flank margin caves formed in the phreatic zone by fresh seawater mixing within the freshwater lens these caves have no direct connection with the sea and form at or close to the tidally influenced fluctuating water table after sea level fall in their subaerial parts caves are enlarged mainly by rock dissolution and by erosion close to the water level condensation corrosion and breakdown processes for understanding the geomorphological features observed in these caves and how they are related to light attenuation we investigated three sampling sites in the tidally influenced zone of lighthouse cave which has been re invaded by seawater during the holocene sea level highstand a freshwater lens no longer exists within or adjacent to the cave rock samples were collected above and below the internal lake shores close to the entrance and in the twilight and dark zones of this cave light and electron microscopy examinations were conducted for detecting microbial cells as well as bioconstruction and bioweathering features in addition a high precision laser scanner was used for characterising sample microtopography our data showed that the microtopography and geomorphology of the lake shore samples cave entrance are dominated by bioweathering whereas the samples of the twilight and dark zones are controlled by a combination of both bioweathering and bioconstructive processes depending on light availability bioconstructive structures such as semi planar lamination at the fluctuating water level of the lighthouse cave show that dissolution due to water mixing of sea and freshwater in the holocene is no longer the most important speleogenetic process we propose that the geomorphological evolution is strongly influenced by the degree of rock diagenesis more than the initial mechanism of speleogenesis

detection of low concentrations of fine grained iron oxides by voltammetry of microparticles abstract mineralogical discrimination of iron oxides in soils and sediments is not a trivial task mainly because of their small grain size and low concentration with mineral magnetic techniques highly magnetic ferrimagnetic spinels can be determined with a very low detection limit 10 ppm unfortunately the magnetic signal of natural samples is often dominated by magnetite and in particular the expression of weakly magnetic antiferromagnetic minerals is suppressed by this high signal in contrast electrochemical techniques such as voltammetry of microparticles vmp are not affected by these differences in magnetic signal vmp makes use of the electrochemical law that iron oxy hydr oxides can be reductively dissolved at potentials that are specific for their mineralogy and reactivity therefore by scanning over a potential range and monitoring the potential at which a reaction occurs one can specify the type of minerals present vmp can be applied to samples without requiring any form of pre treatment the method is rapid comparatively straightforward to interpret and requires little amount of sample g however the detection limit of vmp on natural samples has not yet been investigated here we present a pilot study of the use of vmp in the identification of the ferric oxides of natural samples from spanish red beds of miocene age a standard addition method with pyrolusite as internal standard enabled semi quantitative analysis of the samples concentrations of anti ferromagnetic iron oxy hydr oxides down to 0 1 wt could be detected

the analysis of last interglacial mis 5e relative sea level indicators reconstructing sea level in a warmer world the last interglacial mis 5e 128 116 ka is among the most studied past periods in earth s history the climate at that time was warmer than today primarily due to different orbital conditions with smaller ice sheets and higher sea level field evidence for mis 5e sea level was reported from thousands of sites but often paleo shorelines were measured with low accuracy techniques and in some cases there are contrasting interpretations about paleo sea level reconstructions for this reason large uncertainties still surround both the maximum sea level attained as well as the pattern of sea level change throughout mis 5e such uncertainties are exacerbated by the lack of a uniform approach to measuring and interpreting the geological evidence of paleo sea levels in this review we discuss the characteristics of mis 5e field observations and we set the basis for a standardized approach to mis 5e paleo sea level reconstructions that is already successfully applied in holocene sea level research application of the standard definitions and methodologies described in this paper will enhance our ability to compare data from different research groups and different areas in order to gain deeper insights into mis 5e sea level changes improving estimates of last interglacial sea level is in turn a key to understanding the behavior of ice sheets in a warmer world

the role of maghemite in the enhancement of magnetic signal in the chinese loess paleosol sequence an extensive rock magnetic study combined with citrate bicarbonate dithionite treatment we have conducted a rock magnetic study of selected chinese loess samples before and after citrate bicarbonate dithionite cbd treatment our study is more extensive than previous ones and reveals new details of the magnetic carriers which are related to paleoclimate change three pairs of paleosol s1 the top paleosol layer in the lishi formation and loess l2 underlying s1 from three localities xining xifeng and jixian were investigated by using a variety of magnetic methods after the paleosols were treated with cbd which removes all maghemite grains and the finest grains of magnetite magnetic susceptibility decreased from 77 10 8 to 20 10 8 m3 kg in xining from 165 10 8 to 30 10 8 m3 kg in xifeng and from 180 10 8 to 25 10 8 m3 kg in jixian anhysteretic remanent magnetizations arm were reduced to less than one tenth of the original values in the three sites and saturation magnetization js decreased by about 60 in xining and 70 in xifeng and jixian these reduced values in the paleosols after cbd treatment are similar to those of the corresponding underlying loess samples which however did not show significant decrease after cbd treatment room temperature frequency dependence of susceptibility high temperature dependence of susceptibility and low temperature sirm demagnetization of the paleosol and loess samples before and after cbd treatment confirm that in addition to superparamagnetic sp particles magnetite and or maghemite the cbd removable magnetic carriers also include maghemite of grain sizes larger than sp

maximum sea levels for the last glacial period from u series ages of submerged speleothems pleistocene sea levels reflect changes in the surface distribution of land sea and ice which in turn significantly influence the earth s climate1 the most complete record of sea levels for the last glacial cycle has come from raised coral reef terraces of the huon peninsula papua new guinea2 4 but interpretation of this record is hampered by relatively large age uncertainties and the possibility of variation in the rate of tectonic uplift subaerial speleothems stalagmites stalactites and flowstones from submerged caves in tetonically stable areas provide an alternative source of data5 8 as their growth stops when rising sea levels flood the caves previous studies of speleothems have been limited by dating precision5 6 and sample availability5 7 here we present high precision thermal ionization mass spectrometric 230th ages9 11 for a comprehensive suite of speleothem samples from the bahamas our results provide a record of maximum elevation of sea levels for the period from 80 to 10 kyr before the present for much of which sea levels are poorly known we also find that regional palaeoclimatic change can be an important factor in the termination of speleothem growth

cryptic diagenesis and its implications for speleothem geochronologies abstract speleothems are usually considered as one of the most amenable palaeoclimate archives for u series dating a number of studies in recent years however report cases of diagenetic alteration which compromises the use of u series systematics in speleothems resulting in inaccurate u th ages here we present the results of a high resolution u th dating study of a stalagmite cc26 from corchia cave in italy where we document a number of departures from an otherwise well defined age depth model and explore potential causes for these outliers unlike examples illustrated in previous studies cc26 contains no visible evidence of neomorphism and appears at least superficially ideally suited to dating good reproducibility obtained between multi aliquot u th analyses removes any possibility of analytical issues contributing to these outliers furthermore replicate analyses of samples from the same stratigraphic layer yielded ages in stratigraphic sequence implying very localized open system behavior uranium loss is suggested as a causative mechanism on account of the fact that all the outliers are older than their assumed true age a limited number of micro voids were observed under micro ct analyses and it is proposed that these were pathways for u loss uranium loss modelling allows us to constrain the possible timing of diagenetic alteration and indicates that the precursor for the outlier with the largest age discrepancy 309 must have been aragonite this study indicates that visibly unaltered speleothems may still contain small domains that have experienced post depositional alteration such cryptic diagenesis as recorded in this stalagmite has implications for the constancy of accuracy of the u series dating technique and suggests a need for careful examination of speleothems prior to dating particularly in low resolution u th studies

palustrine sedimentation in an episodically subsiding basin the miocene of the northern teruel graben spain lacustrine deposits form most of the sedimentary record accumulated throughout the miocene in the northern part of the teruel graben a landlocked basin situated in ne spain three main stratigraphic units units i iii spanning late vallesian to late turolian in age are distinguished in the area the two former units comprise mainly carbonate lacustrine deposits that were deposited in a palustrine or a more permanent but shallow lacustrine setting the latter being related mainly to periods of lake expansion under more humid and cooler climatic conditions in contrast deposition of unit iii characterised by gypsiferous lacustrine sediments in central parts of the basin reflects the influence of source rocks of evaporitic nature upper triassic formations that were emplaced by diapiric uplift in the eastern margin during the middle turolian carbonate lake sediments belonging to units i and ii consist of four main lithofacies associations a distal alluvial lake margin deposits b lacustrine carbonates and pedogenically modified lacustrine carbonates c carbonate fill channels and d organic rich marlstone and carbonate marshes lithofacies association a shows typically a sequential arrangement formed from bottom to top of red mudstone carbonate palaeosols and biomicrite beds sequence type 1a these sequences are interpreted as a result of slow but continuous aggradation of the floodplain areas and subsequent rise of the water table probably reflecting equilibrium between subsidence and sedimentation lithofacies association b consisting of biomicrite beds passing upward into palaeosols sequence type 1b is thought to be caused by marked pulses of tectonic subsidence that created the accommodation space required for fast development of a carbonate lake carbonate fill channels showing erosive lower surfaces dig out on previous channels marsh deposits and or lacustrine carbonates exhibit well developed prismatic structure at their bed tops the sequential arrangement suggests similar tectonic constrains than the envisaged for lithofacies 1b the comparison of depositional styles of the lake systems with the palaeoclimatic evolutionary pattern of the basin throughout the miocene indicates that the combined effect of tectonism climate and source rock played a major role in the stratigraphic framework of the basin during this period

quaternary tectonic stability of the bahamian archipelago evidence from fossil coral reefs and flank margin caves abstract throughout the islands of the bahamian archipelago fossil coral reefs are found from current sea level up to a maximum elevation of 4 m 234 u 230 th radiometric dates obtained from in situ corals from these reefs by both alpha count and mass spectrometric techniques indicates that they were all formed during oxygen isotope substage 5e ca 125 000 years ago those data are consistent with a maximum sea level highstand of 6 m during substage 5e and either no vertical motion of the bahamas or possible isostatic subsidence of up to 2 m during the past 120 000 years no older in situ fossil corals or other subtidal deposits have been found subaerially exposed anywhere in the bahamas that finding suggests that late quaternary at least the past 300 000 years isostatic subsidence has occurred at a rate of 1 2 m per hundred thousand years and or no pre 5e highstands were above modern sea level an independent corroboration of the conclusions drawn about sea level amplitude and tectonic stability of the bahamas from the coral reef data is available from examination of abundant flank margin caves horizontal phreatic dissolution caves found above modern sea level throughout the bahamas these horizontally extensive air filled caves have dissolutional ceilings with elevations that are restricted to 1 to 7 m which is consistent with formation at the margin of a thin freshwater lens elevated by a past 6 m sea level highstand the restricted cave elevations and the lack of stalagmites in these caves that are older than 100 000 years are also consistent with cave formation during substage 5e and possible subsequent isostatic subsidence of a few metres the subsurface geology of the southeastern bahamas contains a long term record millions of years that has been attributed to past tectonic activity along the north american caribbean plate boundary while that record suggests differential subsidence across the bahamas in the tertiary period the data from fossil coral reefs and subtidal deposits and flank margin caves indicate that all bahamian banks on which there are islands have been tectonically stable and behaving similarly for at least the past several hundred thousand years

diagenesis of speleothems and its effect on the accuracy of 230th u ages abstract speleothems can be precisely dated by u series disequilibrium methods one basic assumption of the 230th u dating method is that the system remains closed and u and th isotopes are neither lost nor added after deposition for stalagmites this requirement is usually fulfilled due to their protected environment in caves however undersaturated drip water may lead to diagenesis of speleothem caco3 and altered 230th u ages here we present a detailed petrographic investigation using thin sections and 230th u ages of a stalagmite from the riesenberghohle northern germany which grew during marine isotope stages 5e c and a the occurrence of a mosaic fabric in large parts of the stalagmite in combination with several age inversions is a clear indication for diagenetic alteration we discuss the potential diagenetic processes and quantitatively model their influence on the 230th u ages post depositional u loss leads to increasing 230th 238u activity ratios and thus apparently older ages in contrast post depositional addition of u results in decreased 230th 238u activity ratios and apparently younger ages comparison with our modelling results suggests that diagenesis occurred early after deposition initial and post depositional detrital contamination probably played a minor role for the observed age inversions