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

new evidence for two highstands of the sea during the last interglacial oxygen isotope substage 5e sedimentologic stratigraphic and geochronologic analyses of a previously undescribed carbonate section on oahu hawaii provide new evidence for two distinct sea level highstands on oahu during the last interglacial period oxygen isotope substage 5e whereas electron spin resonance and uranium series ages 122 8 ka to 152 25 ka and 115 10 ka to 160 15 ka respectively of in situ corals place the age of the deposits within substage 5e it is the unique sequence of strata found in these exposures that reveals the two transgressions a highstand lagoonal deposit of coral algal bafflestone is overlain by large seaward dipping slabs of beach rock the beachrock deposited during a mid 5e regression is in turn overlain by a second highstand lagoonal deposit this sequence was deposited in a broad shallow back reef embayment that was very sensitive to fluctuations in sea level elsewhere along much of the shoreline of oahu an in situ coral algal framestone waimanalo formation representing the initial 5e highstand is erosionally truncated on its upper surface this erosional unconformity represents the mid 5e lowstand and separates the framestone from overlying seaward dipping planar bedded grainstone and rudstone leahi formation that accumulated during the second 5e highstand

history of stage 5 sea level in bermuda review with new evidence of a brief rise to present sea level during substage 5a abstract oxygen isotope substage 5e is represented by the devonshire formation in bermuda the occurrence of these coastal marine deposits to about 5 m indicates pleistocene sea level data in bermuda do not need tectonic corrections a few published u series coral dates suggest that a conglomerate spencer s point formation may have formed during substage 5c geologic mapping however indicates that the eolianite beneath the conglomerate is pre rather than post devonshire formation in age as was previously thought and the aminostratigraphy of marine sheels also confirms the correlation of the spencer s point and devonshire formations substages 5c and 5a are represented by the southampton formation large eolianites comprise the bulk of this formation they are onlapped by a few small younger marine 1 m and eolian deposits aminostratigraphy confirms that these late southampton age deposits are significantly younger than the devonshire formation and u series dates indicate a substage 5a age the setting of some of these deposits along a protected shoreline precludes discounting their position as anomalous due to large storms this evidence that sea level in bermuda was at about present datum late in substage 5a agrees with interpretations of neotyrrhenian deposits of mediterranean shorelines but not with inferences from the deep sea oxygen isotope record or with data from uplifted coral reefs

variability of el nino southern oscillation activity at millennial timescales during the holocene epoch the variability of el nino southern oscillation enso during the holocene epoch in particular on millennial timescales is poorly understood palaeoclimate studies have documented enso variability for selected intervals in the holocene but most records are either too short or insufficiently resolved to investigate variability on millennial scales1 2 3 here we present a record of sedimentation in laguna pallcacocha southern ecuador which is strongly influenced by enso variability and covers the past 12 000 years continuously we find that changes on a timescale of 2 8 years which we attribute to warm enso events become more frequent over the holocene until about 1 200 years ago and then decline towards the present periods of relatively high and low enso activity alternating at a timescale of about 2 000 years are superimposed on this long term trend we attribute the long term trend to orbitally induced changes in insolation and suggest internal enso dynamics as a possible cause of the millennial variability however the millennial oscillation will need to be confirmed in other enso proxy records

aminostratigraphy of quaternary shorelines in the mediterranean basin the age and correlation of shorelines around the mediterranean basin have been addressed by analyzing the extent of isoleucine epimerization aile ile ratio in protein preserved in molluscan fossils collected from raised marine deposits the taxodont genera glycymeris and arca were selected as the primary taxa for this study because of their simple shell structure reproducible aile ile ratios and ubiquitous occurrence direct comparison of aile ile ratios in associated mollusks allows correlation of disjunct marine deposits and relative dating of sequential marine units in nearby areas that have similar thermal histories the thermal gradient across the mediterranean basin is however sufficiently high that shells from isochronous shorelines have significantly higher ratios at warmer than at cooler localities absolute dating primarily u series dates on corals directly associated with molluscan samples provides an independent calibration of the amino acid data and compensates for dissimilar thermal histories aile ile ratios in shells from 46 marine units cluster into 5 discrete groups c e f g and k that are related to positive sea level events interglacials interstadials associated with odd numbered deep sea isotopic stages the most complete sequences are in southern italy where group c ratios in glycymeris that average 0 30 are associated with the neotyrrhenian a post last interglacial late stage 5 high sea level event group e ratios 0 38 are associated with classical eutyrrhenian deposits from which four u series coral dates 126 7 ka substantiate the correlation to isotope substage 5e group f ratios 0 50 are associated with u series coral and mollusk dates between 200 and 300 ka the deposits are tentatively correlated with stage 7 deposits that have group g ratios 0 58 are correlated with stage 9 shells from lower pleistocene marine deposits that have ratios between 1 0 and 1 2 group k constrain the ages of the younger groups an exponential decrease in the epimerization rate inhibits resolution of the older events aile ile ratios in last interglacial deposits are similar in the northern and central region of the study area but increase sharply in southern sicily north africa and crete similar to the modern thermal gradient a lacuna between group g and group k is similar to gaps identified in california and alaska suggesting generally lower interglacial sea levels between stage 11 and sometime before the brunhes matuyama boundary

oxygen isotope calibration of the onset of ice rafting and history of glaciation in the north atlantic region we report here that dsdp site 552a cored with the hydraulic piston corer on the west flank of rockall bank recovered an undisturbed sequence of alternating white deep sea carbonate oozes and dark coloured layers that are rich in glacial debris oxygen isotope analysis of the sequence together with detailed nannofossil and palaeomagnetic stratigraphy shows that the first major horizon of ice rafting occurred at about 2 4 myr and was preceded by a minor pulse of ice rafting at about 2 5 myr the carbon isotope record shows that the site has been bathed by a water mass of similar characteristics to present day north atlantic deep water at least since 3 5 myr

models for recession flows in the upper blue nile river stream flow recessions are commonly characterized by the exponential equation or in the alternative power form equation of a single linear reservoir the most common measure of recession is the recession constant k which relates to the power function form of the recession equation for a linear reservoir however in reality it can be seen that the groundwater dynamics of even the simplest of aquifers may behave in a non linear fashion in this study three different storage outflow algorithms single linear non linear and multiple linear reservoir were considered to model the stream flow recession of the upper blue nile the recession parameters for the linear and non linear models were derived by the use of least squares regression procedures whereas for the multiple linear reservoir model a second order autoregressive ar 2 model was applied first in order to determine the parameters by the least squares method the modelling of the upper blue nile recession flow performed shortly after the wet season when interflow and bank storage may be contributing considerably to the river flow showed that the non linear reservoir model simulates well with the observed counterparts the variation related to preceding flow on a recession parameter of the non linear reservoir remains significant which was obtained by stratification of the recession curves although a similar stratification did not show any systematic variation on the recession parameters for the linear and multiple linear reservoir models copyright 2004 john wiley sons ltd

south carolina interglacial sites and stage 5 sea levels abstract amino acid and other studies have been made on the 30 km pleistocene sections of the intracoastal waterway between myrtle beach and little river south carolina our ratios differentiate the long established waccamaw oldest canepatch and socastee formations the ratios from the four laboratories that have worked in this area agree very well and apparent conflicts with u series dates may merely reflect an abundance of reworked corals our amino acid correlations with u series coral dates in south carolina bermuda and the mediterranean all argue that the classical canepatch and its horry clay date from isotope stage 5e and not as has been implied from stage 7 9 11 or 13 excavations and erosion have increased position fixing problems along the waterway and canepatch amino acid ratios and u series dates 460 000 100 000 yr b p at icw5 may be from an older unit the canepatch shows the double marine transgression visible in many stage 5e deposits pollen shows that the second transgression occurred late in the interglaciation and stratigraphic studies show that it reached 14 m it therefore fits very well antarctic ice surge models of stage 5 sea level and climate the socastee adds to the evidence for one or more sea levels above 0 m late in stage 5

anatomy of a late quaternary carbonate island constraints on timing and magnitude of sea level fluctuations west caicos turks and caicos islands bwi abstract the data set of the island of west caicos consists of a combination of high resolution lidar and digital imagery radiometric data and amino acid racemization aar d l values as well as extraordinary preservation of sedimentary and bio constructed deposits on the island together with a well established regional stratigraphic framework from the neighboring bahamian island chain and detailed field mapping the west caicos data set provides an opportunity to advance our understanding of the link between carbonate stratigraphy and the controlling parameters of sea level sediment supply tectonics and climate the exceptionally well preserved stratigraphic record of the mid late pleistocene from west caicos allows recognition of marine isotope stages mis 9 11 5e and holocene the west coast of the island provides a continuous 8 4 km exposure of the mis 5e record that enhances our understanding of the intra mis 5e bipartite succession in this region and supports a sea level lowering that occurred during the last interglacial lig west caicos accreted as a series of eolian foreshore shoreface barrier reef and fringing reef facies shoreline positions for all but the mis 7 and mis 5a c deposits are now captured in the sub meter geodetic quality topobathy lidar survey the star town unit of mis 9 11 age forms the southern margin of the island as well as the central karst modified spine with uranium thorium u th coral ages of between 368 and 365 thousand years ago ka and a d l glu average of 0 60 early mis 5e strata include the railroad ridge unit in the center of the island which was previously identified as one of the older units the railroad ridge unit is a north south linear dune ridge that has a d l glu average of 0 52 and indicates the onset of sediment sources from the east associated with a flooded central caicos platform approximately synchronously the early mis 5e south reef unit 3 75 4 m sea level elevation nucleated on the western coast of west caicos attached to the middle pleistocene star town unit the south reef corals yield an average coral u th age of 126 5 ka with an average d l glu from skeletal matrix of 0 46 this transitional barrier fringing reef is unconformably overlain by the late mis 5e boat cove unit corals in the basal transgressive phase of this upper mis 5e boat cove unit yield an average 120 6 ka u th and average d l glu of 0 45 shallow marine foreshore and eolian facies of the late mis 5e rest on a wave cut terrace that cuts the early mis 5e south reef unit by as much as 3 m down to a 0 5 m above present sea level elevation the upper mis 5e boat cove unit displays a maximum of 4 5 m elevation above present day sea level measured from the middle of the foreshore this estimate may be a minimum value as the exposures on the west coast are part of a forced regressive foreshore sequence last stages of the upper mis 5e deposition are seen in a series of regressive dune beach ridge deposits referred to as the northeast ridges unit with sea level positions ranging from 4 5 m early in the central part of west caicos to 0 5 m on the far northeast coast eventually building down below present day sea level this sea level history fits well with previously documented records in the bahamas and globally and the extensive erosion supports a short lived between 126 and 120 ka intra mis 5e relative sea level fall holocene deposition on west caicos is restricted to northern and eastern margins of the island as a combination of strandplain and dune ridge mixed skeletal oolitic units using the high resolution digital elevation model dem and linked digital geologic map makes it possible to compare areas of the different pleistocene and holocene units quantitatively and to constrain volumetric assessments and accumulation rates on the island for different units the peak sediment volume production accumulation rate between 6 5 and 8 106 m3 or between 2 2 and 2 7 106 m3 per ka is observed in the upper mis 5e unit this rate is 5 times greater than the 0 5 106 m3 per ka estimated for the holocene ooid dune ridge strandplain complex suggesting that the combination of higher sea level greater wave and wind energy and warmer ocean temperatures may have fostered the higher rate of chemically precipitated sediment supply

revision of the late pleistocene stratigraphy of bermuda the quaternary stratigraphy of bermuda is one of the world s most complete sedimentary records of interglacial highstands representing at least the past million years yet in terms of the last interglacial rocky bay formation marine isotope substage mis 5e only scanty deposits are preserved in contrast mis 7 generally regarded as a diminutive interglaciation exposes widespread emergent subtidal deposits of the belmont formation indicating a prolonged sea level highstand at ca 2 5 0 3 m this belmont paradox has prompted a reexamination of the geology of key sites along the south shore of bermuda this revision of the late quaternary stratigraphy of bermuda is based on geological field observations primarily the questionable origin of red soil like deposits it is concluded here that there is no physical evidence of the exposure of the upper belmont surface for a full glacial cycle 70 100 ka and that interbedded reddish soil like lenticular deposits are the result of colluvial activity during mid mis 5e reexamination of previously published uranium series u th ages indicates that several 3 m notches contain a mix of ca 125 ka and older coral ages contrary to previous works this study favors an early mis 5e interpretation of the coral ages from the 2 5 m belmont shoreline which is further supported by amino acid racemization aar ratios on whole rock poecilozonites glycymeris and brachiodontes samples from shore and notch deposits an updated aar kinetic model demonstrates that the bulk of epimerization occurred during warm interglacial intervals between 130 and 80 ka and the last 10 ka of the holocene this revised stratigraphy of bermuda now falls into accordance with a more general view of middle and late pleistocene sea level history

aeolianite calcrete microbialite and karst in southwestern australia as indicators of middle to late quaternary palaeoclimates abstract the mid late pleistocene and holocene aeolianites of the tamala limestone on the northern swan coastal plain in southwestern western australia consist of six members that show cyclic deposition of coastal aeolianite overlain by calcrete microbialite karstified surface and palaeosol field work combined with mineralogical chemical stable isotope analysis and uranium thorium u th and optically stimulated luminescence osl dating provides an insight into the repetitive glacial and interglacial climatic periods over the past 500 kyr deposition of the carbonate aeolianites occurred during interglacial episodes marine isotope stage mis 1 5 7 9 11 and possibly 13 due to migration of coastal dunes under the influence of strong southerly to southwesterly winds rainfall was insufficient to support vegetation cover on the dunes and so was probably limited or seasonal the transition from interglacial to glacial climates was characterised by higher effective rainfall accompanied by aeolianite dissolution and karstification during the colder climates and less effective rainfall of the glacial periods there was no carbonate sand deposition instead laminated microbialite and or laminar calcrete formed followed by palaeosol formation the oxygen isotope composition of the microbialites indicates average temperatures during glacial periods 4 c 8 c lower than today and 13 c values demonstrate a higher proportion of c4 plants and therefore a drier or more seasonal climate data from individual members of the tamala limestone show that the wettest interglacial period was mis 5 when extensive karstification and pinnacle development occurred and rainfall was probably higher than at any other time in the past 500 kyr of the glacial periods mis 10 was relatively wet or less seasonal whereas mis 8 and the last glacial maximum lgm were relatively dry and windy the low rainfall during the peak of the glacial periods was probably intensified by colder water offshore due to weakening of the leeuwin current and its replacement by the cold north flowing west australian current

origin of bermuda s clay rich quaternary paleosols and their paleoclimatic significance red clayey paleosols that are chiefly the product of aerosolic dust deposition are interbedded in the quaternary carbonate formations of the bermuda oceanic island system these paleosols provide a basis for reconstructing quaternary atmospheric circulation patterns in the northwestern atlantic geochemical analyses were performed on representative paleosol samples to identify their parent dust source fine grained fractions were analyzed by energy dispersive x ray fluorescence to determine trace element zr y la ti and nb concentrations and to derive geochemical signatures based on immobile element ratios these ratios were compared with geochemical signatures determined for three possible sources of airborne dust 1 great plains loess 2 mississippi river valley loess and 3 saharan dust the zr y and zr la ratios provided the clearest distinction between the hypothesized dust sources the low ratios in the paleosol b horizons most closely resemble saharan dust in the 2 m size class fraction contributions from the two north american loessial source areas could not be clearly detected thus bermuda paleosols have a predominantly saharan aerosolic dust signature saharan dust deposition on bermuda during successive quaternary glacial periods is consistent with patterns of general circulation models which indicate that during glacial maxima the northeast summer trade winds were stronger than at present and reached latitudes higher than 30on despite lower than present sea surface temperatures in the north atlantic

recession curve estimation for storm event separations an accurate recession curve model is important for separating individual flow events which is especially difficult over catchments in regions with a maritime climate where frequent rainfall events cause the flows to rise before they reach the baseflow level the traditional recession curve equations are based on static linear and nonlinear reservoir models these models work quite well for ground water dominated recession curves but not so well when the direct runoff is significant in the recession part in this study a new modelling methodology is explored based on self adaptive parameters in the linear and nonlinear reservoir models it has been found that the adaptive forms performed better than the static ones especially when a window for the adaptive parameter estimation is properly selected while the nonlinear adaptive model had better accuracy over the linear one it could become unstable if its window is too narrow indicating that more research work is needed to find an useful pattern for the window size a comparison between the recession curve models and pdm model a rainfall runoff model has shown that they agreed quite well in most winter events but less so in the summer

mixed carbonates and siliciclastics in the quaternary of southern belize pleistocene turning points in reef development controlled by sea level change the belize barrier and atoll reefs represent one of the largest reef structures in the atlantic ocean the southern shelf of belize is a classic location of a modern mixed carbonate siliciclastic system whereas knowledge of the holocene deposits in the area is extensive data on the pleistocene system are fragmentary open questions include i the nature of the reef foundations carbonate versus siliciclastics ii the ages of the deposits including the initiation of the barrier reef and iii the response of the mixed system to sealevel fluctuations the results of a study of borings on the southern belize shelf are presented here six up to 105 m long borings were made to better understand the history of this important mixed system uranium series dating in the pleistocene was not possible because of diagenetic alteration however lithostratigraphy strontium isotopes and calcareous nannofossil biostratigraphy were used to constrain stratigraphic ages results support the contention that the quaternary development in belize was quite similar to that of other major barrier reefs such as the florida reef tract and further afield the great barrier and the new caledonian barrier reefs all of these barrier reefs are mixed carbonate siliciclastic systems and significant reef growth only began after the onset of high amplitude eccentricity controlled sea level changes and as late as during the exceptionally long and warm marine isotope stage 11 some 400 ka in belize early pleistocene sections at bases of borings include mollusc rich wackestones rare coral packstones and marls which were deposited under low to moderate energy conditions in a ramp setting before ca 900 ka during the high sea levels of marine isotope stage 25 and possibly earlier marine isotope stage 31 or 37 the belize shelf was subaerially exposed for most of the mid pleistocene and was dominated by siliciclastic sedimentation possibly during marine isotope stages 24 to 12 when highstands were comparatively low continuous reefs at the shelf margin were developing during highstands in the late pleistocene beginning with the long and high highstand of marine isotope stage 11 some 400 ka the southern shelf was flooded entirely and carbonates started to dominate once more reefs developed on top of siliciclastic deposits on the shelf a continuous barrier reef came into existence and largely developed on top of carbonates at the shelf margin during late pleistocene lowstands siliciclastics presumably no longer reached the shelf margin because of the topographic high of the barrier reef platform the quaternary belize example may serve as a model for reconstructing ancient mixed systems in icehouse worlds however any extrapolations are limited by the fact that fast growing scleractinian reef builders had not yet evolved in the palaeozoic

reconciliation of sea level observations in the western north atlantic during the last glacial cycle abstract a south to north gradient of increasing marine isotope substage mis 5a 80 ka bp sea level has been recorded across the caribbean and surrounding region relative to present mis 5a sea levels range from 19 m to more than 3 m between barbados haiti the bahamas florida bermuda and the us atlantic coast in contrast no gradient in sea level is observed for the last interglacial period mis 5e 128 118 ka bp at tectonically stable localities in the same region with deposits generally lying several metres above present we demonstrate here that these controversial observations are reconciled by taking into account the isostatic response of the earth to glacial loading and unloading a fundamental effect that is commonly overlooked in the interpretation of sea level observations from different locations to define a global sea level curve furthermore the observed gradient can be used to place constraints on earth rheology and is an important indicator of the behaviour of the north american ice sheets during the last glacial cycle

holocene lake level fluctuations and environmental changes at taro co southwestern tibet based on ostracod inferred water depth reconstruction lake level change is an important indicator of changes in the hydrological status of lakes triggered by the influence of atmospheric circulation systems previous studies show that the interaction

atlantic seasonal hurricane frequency part i el nino and 30 mb quasi biennial oscillation influences abstract this is the first of two papers on atlantic seasonal hurricane frequency in this paper seasonal hurricane frequency as related to e1 nino events during 1900 82 and to the equatorial quasi biennial oscillation qbo of stratospheric zonal wind from 1950 to 1982 is discussed it is shown that a substantial negative correlation is typically present between the seasonal number of hurricanes hurricane days and tropical storms and moderate or strong 15 cases el nin off the south american west coast a similar negative anomaly in hurricane activity occurs when equatorial winds at 30 mb are from an easterly direction and or are becoming more easterly with time during the hurricane season this association of atlantic hurricane activity with el nino can also be made with the southern oscillation index by contrast seasonal hurricane frequency is slightly above normal in non el nino years and substantially above normal when equatorial stratospheric winds blow from a westerly direction and or are bec

quantifying species environment relationships in non marine ostracoda for ecological and palaeoecological studies examples using iberian data abstract with current concerns over issues such as global warming the use of palaeoecological data to reconstruct past environments has gained a special significance but much of the work on ostracod ecology and paleoecology has been qualitative in nature or on a site specific rather than integrated regional basis furthermore ostracod ecological relationships are complex with each species occupying a multidimensional niche and a range of statistical techniques can be employed to establish the significance of different environmental variables on species distribution we employ logistic regression lr and canonical correspondence analysis cca to define ostracod species niches and assemblage response to environmental gradients using a modern dataset of 465 ostracod samples from the eastern iberian peninsula in addition to these ecological analyses we develop ostracod based transfer functions for the quantitative reconstruction of past environmental change from a modern regional data set of non marine ostracod and limnological data by means of weighted averaging wa regression and calibration examples cited are primarily from modern and fossil ostracod samples from iberian water bodies our results suggest that water chemistry solute composition and concentration and temperature are the factors to which non marine ostracod species respond in a more clear and consistent way species environment relationships modelled using the transfer function approach of wa are strong for the above mentioned variables and therefore these models may be of great help in palaeoenvironmental reconstructions

quaternary aminostratigraphy of eolianite on lord howe island southwest pacific ocean abstract amino acid racemization aar dating of the eolianite on lord howe island is used to correlate several disparate successions and provides a geochronological framework that ranges from holocene to middle pleistocene time the reliability of the aar data is assessed by analysing multiple samples from individual lithostratigraphic units checking the stratigraphic order of the d l ratios and the consistency of the relative extents of racemization for a suite of seven amino acids three aminozones are defined on the basis of the extent of racemization of amino acids in land snails placostylus bivaricosus and whole rock eolianite samples aminozone a includes placostylus from modern soil horizons e g mean d l leucine ratio of 0 03 0 01 and whole rock samples from unconsolidated lagoonal and beach deposits 0 10 0 01 0 07 0 03 aminozone b includes placostylus 0 45 0 03 and whole rock samples from beach 0 48 0 01 and dune 0 45 0 02 0 30 0 02 units of the neds beach formation deposited during ois 5 the oldest aminozone c comprises placostylus recovered from paleosols 0 76 0 02 and whole rock eolianite samples 0 62 0 00 from the searles point formation which indicate the formation was likely deposited over several oxygen isotope stages ois during and prior to ois 7 these data support independent lithostratigraphic interpretations and are in broad agreement with u th ages of speleothems from the searles point formation and corals from the neds beach formation and with several tl ages of dune units in both formations the aar data reveal that eolianite deposition extends over a significantly longer time interval than previously appreciated and indicate that the deposition of the large dune units is linked to periods of relatively high sea level

quaternary stratigraphy of bermuda a high resolution pre sangamonian rock record abstract carbonate islands such as bermuda are created by climatic change warm climates and high sea levels stimulate carbonate sediment production that may ultimately result in island growth while cold glacials expose the platforms to weathering dissolution and soil formation of great importance in quaternary studies is the ability to decipher this climatic history mapping and geochronologic studies have established that bermuda may have one of the most continuous and detailed quaternary interglacial depositional records on a carbonate platform advances in racemization dating aar have offered a means of deciphering this climatic history and generating a high resolution stratigraphic and age framework for the quaternary bermudian interglacial units consist predominantly of eolianites with less voluminous occurrences of beach deposits and calcarenite protosols entisols glacial or stadial age terra rossa aluminous laterite paleosols whose degree of development is a function of time of exposure form boundaries between interglacial units d alloiso leucine l isoleucine a i ratios have been determined on marine pelecypods land snails and whole rock samples from mapped sections aminozones have been defined for two sangamonian and at least five pre sangamonian depositional intervals from kinetic models based on calibration with previously published u series coral dates estimated ages of middle pleistocene and older aminozones are f 190 000 265 000 years g 300 000 400 000 years h 400 000 500 000 years j 700 000 years and k 900 000 years aminozone g which is correlated with the upper town hill formation and isotope stage 9 is volumetrically the most important depositional event of the middle pleistocene the great mass of sediment deposited during this period suggests an interglacial of significant duration and prolonged shelf submergence during which the island grew to over half its present size only the sangamonian sensu lato rivals stage 9 in volume of eolianite deposited on the island sea level amplitude as determined from dated outcrops appears to correlate well with amplitudinal variations in the oxygen isotope record

stable isotope record of organic carbon from an evolving carbonate banktop bight of abaco bahamas the stable isotope composition delta sup 13 c of total organic carbon toc was measured as a function of depth throughout a 217 cm thick sequence of holocene carbonate sediment within the bight of abaco lagoon little bahama bank biofacies and lithofacies analyses indicate progressive banktop submergence and paleoenvironmental response during holocene sea level rise stable isotope values shift markedly from minus 27 7 per thousand within the 7900 b p paleosol at the base of the core to minus 11 1 per thousand at the present day sediment water interface an abrupt excursion toward heavy isotope values records the first establishment of thalassia seagrass upon open marine flooding a multitracer approach combining biofacies lithofacies and stable isotope analysis of toc confirms that the dramatic 17 per thousand shift observed in delta sup 13 c was a direct result of sea level rise and associated environmental changes over the banktop there is little evidence of spurious diagenetic overprint stable isotope analyses of organic carbon may enhance the reconstruction of carbonate sequences by revealing a distinctive geochemical signature of banktop flooding including the onset of growth of otherwise unpreservable thalassia seagrass

the distribution of carbonate eolianite abstract carbonate eolianite forms distinctive coastal landforms on many mid latitude continents and islands numerous studies of extensive continental and smaller island deposits in both hemispheres have shown the eolianites are predominantly pleistocene in age the coorong coastal plain of south australia contains the world s longest record of eolianite deposition revealing that major phases of carbonate accumulation occurred during interglacial and some interstadial sea level highstands throughout the quaternary similarly the well studied eolianite islands of bermuda and the bahamas record a close match between dune accretion and sea level highstands since the middle pleistocene several other eolianite deposits appear to have formed at least partially during glacial periods the glacial age deposits are eolian reworked relict shelf or coastal sediments or remnants of former highly mobile coastal dunes sourced from low sea level shorelines the distribution and bioclastic composition of large scale eolianite deposits suggests carbonate production on shallow shelves and banks is the ultimate control on the formation of eolianite the bulk of the carbonate comprising those eolianites is heterozoan being produced where there is low terrigenous sediment input in dominantly temperate cool water and subtropical carbonate provinces quaternary cyclical movements of sea level have also controlled the form and rate of coastal carbonate deposition with repeated pulses of sedimentation during highstands forming laterally coalesced vertically stacked or composite dune successions major unconformities within the deposits are marked by paleosols which record hiatuses in coastal sedimentation in several regions major eolianite units overlie coastal deposits of terrigenous sediment those successions suggest that the trend towards aridity and reduction in the supply of terrigenous sediment to shelves during the quaternary has enhanced the production of carbonate and the deposition of eolianite

geochemical evidence of saharan dust parent material for soils developed on quaternary limestones of caribbean and western atlantic islands abstract most previous workers have regarded the insoluble residues of high purity quaternary limestones coral reefs and oolites as the most important parent material for well developed clay rich soils on caribbean and western atlantic islands but this genetic mechanism requires unreasonable amounts of limestone solution in quaternary time other possible parent materials from external sources are volcanic ash from the lesser antilles island arc and saharan dust carried across the atlantic ocean on the northeast trade winds soils on quaternary coral terraces and carbonate eolianites on barbados jamaica the florida keys united states and new providence island bahamas were studied to determine which if either external source was important caribbean volcanic ashes and saharan dust can be clearly distinguished using ratios of relatively immobile elements al 2 o 3 tio 2 ti y ti zr and ti th comparison of these ratios in 25 soils where estimated ages range from 125 000 to about 870 000 yr shows that saharan dust is the most important parent material for soils on all islands these results indicate that the northeast trade winds have been an important component of the regional climatology for much of the quaterary saharan dust may also be an important parent material for caribbean island bauxites of much greater age

leading tropical modes associated with interannual and multidecadal fluctuations in north atlantic hurricane activity abstract interannual and multidecadal extremes in atlantic hurricane activity are shown to result from a coherent and interrelated set of atmospheric and oceanic conditions associated with three leading modes of climate variability in the tropics all three modes are related to fluctuations in tropical convection with two representing the leading multidecadal modes of convective rainfall variability and one representing the leading interannual mode enso the tropical multidecadal modes are shown to link known fluctuations in atlantic hurricane activity west african monsoon rainfall and atlantic sea surface temperatures to the tropics wide climate variability these modes also capture an east west seesaw in anomalous convection between the west african monsoon region and the amazon basin which helps to account for the interhemispheric symmetry of the 200 hpa streamfunction anomalies across the atlantic ocean and africa the 200 hpa divergent wind anomalies and both the structure and spatial scale

facies architecture and controlling factors induced depositional model of the quaternary carbonate eolianites in the northwestern mediterranean coast of egypt

an expanded ostracod based conductivity transfer function for climate reconstruction in the levant abstract we present the first modern calibration dataset linking ostracod assemblage composition to water chemistry and other site specific variables in the hydrologically and geopolitically sensitive southern levant region a total of 42 ostracod taxa were recorded from the 178 sampled sites in israel and jordan ilyocypris spp heterocypris salina and cypridopsis vidua are the most abundant taxa species strictly confined to freshwater conditions are prionocypris zenkeri gomphocythere ortali and prionocypris olivaceus in contrast h salina bradleytriebella lineata and cyprideis torosa show high frequencies in brackish waters waters with higher conductivity humphcypris subterranea g ortali p olivaceus and cypridopsis elongata apparently prefer flowing waters specific conductivity optima and tolerance ranges were calculated for the recorded ostracod species and may be used for the palaeoenvironmental assessment of fossil ostracod assemblages in addition a transfer function for quantitative specific conductivity estimation based on 141 samples was established with weighted averaging partial least squares regression wa pls the resulting coefficient of determination r 2 between observed and predicted conductivity values 0 72 and the root mean square error of prediction rmsep in gradient length 13 1 indicate that conductivity may be reliably estimated from ostracod assemblage data the transfer function was first applied to last glacial ostracod assemblage data from an archaeological trench in the sea of galilee northern israel relatively large conductivity fluctuations between ca 1 and 7 ms cm 1 were inferred for the period 24 20 cal ka bp in addition four episodes of freshwater influx near the site of the trench were identified from the presence of shells of freshwater and stream dwelling species intermingled with very abundant shells of cyprideis torosa the results of our study allow a better use of quaternary ostracods from the levant as palaeoenvironmental indicators of water body types and past conductivity levels and will contribute to a better understanding of quaternary environmental and climate change in the levant

late holocene sedimentation and hydrologic development in a shallow coastal sinkhole on great abaco island the bahamas abstract it remains poorly understood how sea level drives environmental change and hydrographic development in coastal karst basins underwater caves sinkholes blueholes etc over millennial timescales it was previously hypothesized that coastal karst basins ckbs transition from vadose to littoral then anchialine and finally submarine environments as sea level rise inundates coastal karst landscapes but the initial flooding event of ckbs remains challenging to sample runway sinkhole hosts a modern anchialine ecosystem located 225 m from great abaco island coastline in the bahamas and its shallow water depth 1 8 mbsl permits an investigation into the early environmental evolution and hydrographic development in a ckbs after inundation by sea level rise four sediment cores were collected from runway sinkhole and late holocene environmental change was reconstructed with benthic foraminiferal paleoecology organic matter geochemistry om 13 c org and c n x radiography and radiocarbon dating despite some uncertainties associated with the chronology it appears that holocene sea level rise initially flooded runway sinkhole and created a littoral environment at least by 3 9 ka whereafter a detrital peat deposit accumulated in the sinkhole this detrital peat had a high organic matter content mean 88 a 13 c org value indicative of organic matter derived from c 3 plants including mangroves 28 and an unknown calcareous microfossil suggestive of a non marine habitat in the sinkhole a shift to carbonate sand deposition organic matter with more marine influenced 13 c org values 23 and expansion of euryhaline bolivina striatula elphidium poeyanum and triloculina bermudezi and anchialine physalidia simplex and conicospirillina exleyi benthic foraminifera at 1 2 ka marks the onset of modern anchialine environmental conditions at the sediment water interface 1 8 mbsl these results suggest that relative sea level rise in the bahamas forced environmental change in runway sinkhole at 1 2 ka and indicate that peat deposits in coastal sinkholes must be verified as in situ before being utilized as sea level indicators

lake level history of lake tanganyika east africa for the past 2500 years based on ostracode inferred water depth reconstruction assemblages of ostracodes from sediment cores illuminate lake level history at decadal to centennial timescales during the late holocene at lake tanganyika east africa the ostracode based lake level curves for several cores resemble both each other and the only previously published lake level record of comparable resolution for lake tanganyika during this interval successfully reconstructing known highstands improving the chronology of known lowstands and contributing new information on late holocene lake level variability at this important tropical african location in agreement with other late holocene records from east africa the surface level at lake tanganyika reflects predominantly arid conditions throughout this interval interrupted by relatively brief episodes of higher precipitation and lake level the most pronounced lowstand in the record occurs at v200 0 bc with other significant lowstands dating to the intervals v200 500 ad v700 850 ad the medieval warmperiod mwp v1050 1250 ad at lake tanganyika and the latter part of the little ice age lia v1550 1850 ad the most important wet intervals in the lake level record are centered on v500 ad v1500 ad and v1870 ad the highstands and lowstands reported here for lake tanganyika appear to be fairly coherent with other records of rainfall throughout east africa during the mwp and the lia prior to the mwp paleoclimate records are apparently less coherent although this may be a reflection of the resolution and abundance of recent paleoclimatic data available for this climatically complex region

holocene palaeohydrology of lake titicaca estimated from an ostracod based transfer function lacustrine deposits of holocene age 8000 14c yr bp present were studied in lake titicaca bolivia ostracod assemblages were identified in six cores taken in the three basins which today form lake titicaca factorial correspondence and multiple linear regression analysis of the ostracods have permitted the reconstruction of 1 lake level 2 water salinity and 3 water mg ca ratio variations palaeolake levels indicate a complex evolution of the three basins with some major phases after a flooding at about 8000 yr 14c bp the lake level fluctuated around a mean position until 3900 14c yr bp when a second rise took place it seems however that the present day lake level was not reached until after 680 yr 14c bp some major dry events are also recorded at about 5300 14c yr bp and 2300 14c yr bp the lake titicaca data are consistent with other records from south america and also seem to reflect some world wide events

pre sangamonian eolianites in the bahamas new evidence from eleuthera island abstract the present study provides new insight into the quaternary stratigraphy of the bahamas refining the stratigraphic record of tectonically stable carbonate islands such as the bahamas is important for improving our perception of eustatic and climatic variations during this time interval two key sections located 15 km apart in the northern portion of eleuthera display three vertically stacked rock units 1 a basal unit consisting of up to four eolianites separated by paleosols 2 intermediate oolitic deposits showing beach facies at 6 m and 3 an upper bioclastic eolianite overlain by a thick calcrete the occurrence of beach facies at an elevation of 6 m above msl suggests an early sangamonian age isotopic substage 5e for the intermediate oolitic deposits because of its position below a thick calcrete the upper unit was more likely formed during a later highstand of the sangamonian substage 5c or 5a rather than during the holocene it follows that the basal unit clearly predates the last interglacial this new evidence from eleuthera shows that pre sangamonian rocks may be more extensive in the bahamas archipelago than previously thought it also emphasizes the widespread occurrence of bioclastic limestones in an area often considered as being entirely composed of oolites

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

post miocene diagenetic and eustatic history of enewetak atoll model and data comparison the post miocene diagenetic and eustatic history of enewetak atoll was investigated using a one dimensional forward model comparison of model and data suggests that the post miocene history of enewetak atoll was dominated by multiple episodes of meteoric phreatic diagenesis attendant with high frequency 10 sup 4 to 10 sup 5 yr fluctuations in sea level and a subsidence rate of 39 0 m m y sensitivity testing indicates that subaerial erosion results in the preservation of additional subaerial unconformities because stratigraphic shortening permits a succeeding sea level rise to flood the exposure surface and deposit sediment whereas without subaerial erosion this sea level rise would be recorded as a paleophreatic lens model results indicate that less then 10 of lapsed time is recorded by sediment deposition during periods of high frequency changes in sea level incompleteness of the stratigraphic record suggest that magnetostratigraphy may give erroneous ages for shallow marine carbonate sequences deposited during times of high frequency changes in sea level and frequent magnetic polarity reversals

baseflow recession and recharge as nonlinear storage processes discharge in many rivers is often fed by outflow from a shallow groundwater reservoir it is becoming clear that the outflow from this aquifer is not linearly proportional to storage as is commonly assumed in many algorithms numerical analysis of flow recession curves from about 100 river gauging stations instead reveals a nonlinear relationship between baseflow q and storage s for which the equation s aqb was adopted values of the exponent b are found by calibration to be between 0 and 1 but with a high concentration around 0 5 which is in accordance with the findings of other studies and theoretical approaches yielding b 0 5 for unconfined aquifers and relating the coefficient a to catchment properties primarily area and shape of basin pore volume and transmissivity this non linear reservoir function is proposed as a more realistic alternative to the linear reservoir function the relatively fast response of groundwater flow to rainfall is mainly a result of the increase of hydraulic head of the groundwater reservoir accelerating the exfiltration of old pre event water into the river bed as fissure and pore volumes communicate hydraulically it appears physically reasonable to model the system by one non linear reservoir for catchments or parts of them instead of applying independent parallel linear reservoirs the non linear reservoir algorithms are supported by an analytical derivation they are extended for the automatic separation of baseflow from a time series of daily discharge in rivers and the computation of storage and effective recharge of groundwater in river basins by inverse nonlinear reservoir routing the time series obtained allow the identification and quantification of long term changes to the water balance relationships between computed groundwater storage and observed groundwater level can also be established copyright 1999 john wiley sons ltd

stratigraphy and geochronology of pitfall accumulations in caves and fissures bermuda abstract deep fractures fissures and avens skylights in limestone cave roofs create natural traps for sediments and biota fissures fill quickly with surface sediment and organisms soon after opening debris cones are formed as materials fall wash or drift on air through openings in cave skylights such deposits in admiral s and grand canyon cave bermuda contain distinct beds and are composed of mixtures of sediment and charcoal together with fossils of land snails crabs birds reptiles and bats the pitfall accumulations were periodically sealed over by calcite flowstone a stratigraphic record of surface activity and fauna through both glacial and interglacial periods has been preserved the succession also provides an ideal setting in which to compare several geochronological methods calibrated 14 c ages on charcoal and shells provide dated horizons at 1600 12 800 and about 35 000 14 c yr bp thermal ionization mass spectrometric tims ages on several flowstone layers constrain the entire sequence in the admiral s cave sequence between 126 300 900 yr termination ii and historical times a continuous relative age record generated by amino acid epimerization aae geochronology d alloisoleucine l isoleucine or aile ile on the pulmonate land gastropod poecilozonites verifies the biostratigraphy reveals a minimal degree of mixing between stratigraphic units and establishes an independent temporal link between the subterranean and subaerial deposits of bermuda this convergence between stratigraphy and geochronology yields a precisely dated succession from the oceanic island of bermuda and thus presents a unique opportunity to assess the rates and processes of evolutionary and climate change during that interval

aminostratigraphy and ages of pleistocene limestones of bermuda the pleistocene stratigraphy of bermuda offers important information for sea level history corals are rare in bermuda pleistocene carbonates and so many deposits are not appropriate for u series dating we have extended the geochronological base in bermuda by determining the extent of isoleucine epimerization a i ratios in 1 marine shells glycymeris and others from deposits of sea level high stands 2 land snails poecilozonites from protosols associated with the eolianites that comprise the bulk of bermuda and 3 whole rock samples of bioclastic calcarenites the three distinct types of samples provide independent aminostratigraphies aminozones c e f g h j and k that are mutually consistent and in agreement with the mapped lithostratigraphy correlation of the amino acid ratios with ages based on previously published u series coral dates verifies the utility of the apparent parabolic kinetics model for estimation of amino acid racemization ages extrapolation of ages based on the model to deposits beyond the range of u series dating reveals that a significant middle pleistocene section is present in bermuda

u series and amino acid racemization geochronology of bermuda implications for eustatic sea level fluctuation over the past 250 000 years abstract bermuda is a stable mid oceanic carbonate platform for which a particularly complete record of late pleistocene eustatic sea level fluctuation has been reconstructed from a detailed study of geological field relationships combined with an extensive programme of u series and amino acid racemization geochronology only twice in the past 250 000 yr has sea level in bermuda been above its present level once at approximately 200 k y when it stood at about 2 m and most recently at 125 4 k y when it stood at 5 1 m these times of interglacial high sea level are characterized by the development of patch reefs and marine calcarenites at elevations above present sea level episodes of lower sea stand onto the bermuda platform at elevations higher than 20 m are observed within the two interglacial periods and are characterized by the deposition of eolianites by contrast glacial periods are times of residual soil formation and deposition of speleothems in caves at elevations below present sea level excellent correlation is observed between the bermuda glacio eustatic sea level record and other marine and terrestrial paleoclimate records

reconstruction of prehistoric landfall frequencies of catastrophic hurricanes in northwestern florida from lake sediment records abstract sediment cores from western lake provide a 7000 yr record of coastal environmental changes and catastrophic hurricane landfalls along the gulf coast of the florida panhandle using hurricane opal as a modern analog we infer that overwash sand layers occurring near the center of the lake were caused by catastrophic hurricanes of category 4 or 5 intensity few catastrophic hurricanes struck the western lake area during two quiescent periods 3400 5000 and 0 1000 14 c yr b p the landfall probabilities increased dramatically to ca 0 5 per yr during an hyperactive period from 1000 3400 14 c yr b p especially in the first millennium a d the millennial scale variability in catastrophic hurricane landfalls along the gulf coast is probably controlled by shifts in the position of the jet stream and the bermuda high

water depth related ostracod distribution in lake pumoyum co southern tibetan plateau abstract a modern training set covering 55 surface sediment samples from pumoyum co a freshwater lake on the southern tibetan plateau was analysed in order to quantify relationships between ostracod species distribution and environmental conditions the extensive data set referring to nine ostracod species includes physico chemical parameters for water depths ranging between 1 m and 62 m canonical correspondence analysis suggests that water depth significantly controls the spatial distribution of modern ostracods in the lake on this basis an ostracod based water depth transfer function was established for reconstructing palaeo lake levels the transfer function presents a good correlation between measured and estimated water depth r2 0 87 with a root mean square error of prediction of 15 5 m this transfer function was applied to fossil ostracod associations of 38 sediment samples from a gravity core which covers the last 6 ka bp three stages of lake level fluctuations since 6 ka bp were inferred a low lake level 25 m compared to the present 65 m depth between 6 0 ka bp and 4 3 ka bp a fluctuating lake level 25 to 5 m from 4 3 to 2 0 ka bp and a rise from a low level 25 m to that of present day within the last two millennia together with other proxies including ostracod diversity and grain size as well as total organic carbon and total inorganic carbon content of the gravity core sediments the water depth transfer function was used to reconstruct past climate change in the pumoyum co area as a response to indian monsoon dynamics

the role of geodiversity on the groundwater resource potential in the upper blue nile river basin ethiopia groundwater has been the main source of water supply for large cities and towns over the last few decades in the upper blue nile river basin ethiopia however provision is often unsuccessful because of poor well productivity difficult drilling conditions poor well positioning or sometimes due to poor water quality the growing pressure of urban population and industrial development is focusing unprecedented attention on the groundwater potential of the basin the purpose of this work is to spatially characterize the groundwater potential of the upper blue nile river basin with respect to variable recharge and geodiversity the study shows that from the annual recharge obtained using the base flow separation method the renewable groundwater potential in the basin was estimated to be in the range of 1 2 and 2 billion m3 year the aquifers in the area are divided into three categories low to moderate productivity 3 5 l s which includes crystalline basement rocks acidic lava flows and domes and very fine alluvial sediments moderate to high productivity 5 5 l s that includes mesozoic sedimentary rocks sandstone limestone gypsum dolomite and high to very high productivity 20 l s which includes basic lava flows of the trap series quaternary lava flows and alluvial sediments

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

after the hurricane hits recovery and response to large storm events in a saline lake san salvador island bahamas abstract the shallow saline lakes of san salvador island bahamas contain important high resolution records of faunal dynamics hurricane deposition and salinity changes that can be used to examine the effects of storms on these ecosystems two cores measuring approximately 60 cm each in length were taken from salt pond a hypersaline lake on the eastern side of the island that has been frequently inundated by storm surge overwash multiproxy analyses of loss on ignition sediment grain size composition and fabric invertebrate fauna as well as trace element and oxygen and carbon isotope analyses were performed these cores record sedimentation punctuated by hurricane and other large storm events and a salinity history that varies from brackish to hypersaline with the formation of salts such as halite and gypsum four species of ostracodes cyprideis americana dolerocypria inopinata hemicyprideis setipunctata and perissocytheridea bicelliforma were analyzed for their diversity trace elements and isotopes and compared to the salinity and depositional history of the lake faunal diversity and abundance appears to increase after storm events due to the freshening of the lake suggesting that the system continues to reset itself recovering quickly from each major disturbance in a threshold like response the recovery period is rapid and does not appear to affect the long term faunal composition of the lake

storage outflow modelling of streamflow recessions with application to a shallow soil forested catchment abstract the objectives of this study were to introduce an alternative to the matching strip correlation and parameter averaging methods for deriving master recession characteristics from a set of recession segments and to apply the method to streamflow recession segments for a small forested catchment in which baseflow is provided by drainage of the saturated zone in the shallow permeable soil the method involves fitting conceptual storage outflow models using an iterative algorithm diagnostic plots revealed that the recessions were non linear and that the recessions did not follow a common single valued storage outflow relation a model involving two linear reservoirs provided substantially better fit than three single reservoir models indicating that the form of the recession curve probably depends not just on the volume of subsurface storage but also on its initial distribution amongst reservoirs

estimating palaeo water depth from the physical rock record abstract palaeo water depth and its change with time is a key factor in environmental analysis and in sedimentology in general the literature published on this topic and on related subjects however is substantial albeit scattered within and between different communities geologists oceanographers engineers physicists etc here i focus on proxies for palaeo bathymetry as obtained from the physical rock record floral faunal and chemical evidence for palaeo water depth being equally important must be dealt with elsewhere an assessment of the main depth related parameters in actualistic settings is presented and their applicability to the fossil sedimentary record discussed the outcome reveals the full complexity of this topic there is for example no such thing as an average wave base depth applicable to a wide range of fossil case settings this because wave and current climates in general and particularly so in neritic and coastal settings are intriguingly complex furthermore observations from modern oceans are not a priori applicable to fossil ones acknowledging these problems and limitations critically evaluated quantitative proposals for depth indicative facies and features in the sedimentary record are presented and error bars discussed

the use of ostracods from marginal marine brackish waters as bioindicators of modern and quaternary environmental change abstract ostracoda microscopic aquatic crustacea from brackish waters have a great potential for ecological monitoring and palaeoenvironmental analyses in highly variable environments this has been proven in many articles during recent decades but their potential has yet to be fully developed or utilised the analysis of ostracod assemblage composition species distributions eco phenotypic variability and the analysis of stable isotopes and trace elements in ostracod shells provide valuable information on present and past water salinity temperature and chemistry hydrodynamic conditions substrate characteristics climate sea level variations oxygen and nutrient availability this article provides an overview on the application of ostracods from brackish waters for palaeoenvironmental reconstruction in the quaternary and for environmental studies in present day environments

mega highstand or megatsunami discussion of mcmurtry et al elevated marine deposits in bermuda record a late quaternary megatsunami sed geol 200 2007 155 165 abstract graded sorted rounded and ponded marine sand and conglomerate deposited in caves and on an erosional terrace at 20 m on bermuda previously interpreted as originating in a eustatic highstand of sea level during the middle pleistocene were reinterpreted by mcmurtry et al 2007 as the result of a great 20 m megatsunami at sea propagating out across the north atlantic from the canary islands cresting and rolling up and over the bermuda platform however no middle pleistocene tsunami deposits have been reported elsewhere on bermuda or anywhere else around the north atlantic rim the tsunami origin is unsupportable whereas the available evidence unequivocally establishes a 21 m eustatic sea level during the middle pleistocene mis 11 interglacial

diagenesis in limestone dolostone successions after 1 million years of rapid sea level fluctuations a case study from grand cayman british west indies abstract meteoric diagenesis in young marine carbonate sediments has commonly been linked to fluctuations in quaternary glacio eustatic sea levels the extent to which these sea level changes are recorded in these carbonate successions however remains questionable this is amply demonstrated by the diagenetic record found in the limestones and dolostones of the cayman formation miocene on the cayman islands on the eastern part of grand cayman dolomitization that ceased by 1 million years ago created an architecture whereby the limestones in the central part of the island were surrounded by dolostones in coastal areas of the island since then the upper 90 m of the cayman formation has been repeatedly cycled through many different marine and meteoric diagenetic zones as large rapid eustatic oscillations in sea level affected the island the records of these diagenetic cycles in the dolostones and limestones are however different and impossible to match to the cyclic changes in sea level in the peripheral dolostones post dolomitization diagenetic features are sparse in contrast the limestones in the interior of the island exhibit a wider variety of meteoric diagenetic features including extensive dissolution and calcite cementation the dolostones have low porosity

a quantitative inference model for conductivity using non marine ostracode assemblages on san salvador island bahamas paleosalinity records from two lakes abstract quantitative records of past environments are needed to understand natural variability in ecosystems and their responses to climate change changes in ostracode assemblages through time can provide such records as ostracode species are sensitive to changes in their local environments before they can be used to indicate past environments however is it necessary to understand how distributions of assemblages change across environmental gradients to that end thirty two lakes on san salvador island bahamas were sampled for both ostracodes and nineteen limnological variables multivariate fuzzy set ordination indicates that change in ostracode assemblages is significantly and independently correlated with three environmental variables electrical conductivity salinity dissolved oxygen and alkalinity a transfer function was created to reconstruct past conductivity since changing conductivity of lakes on san salvador is influenced by changes in climate and sea level a 2 component weighted averaging partial least squares model performed best as a transfer function for conductivity with an apparent r 2 of 0 76 and an r 2 of 0 69 between observed and predicted conductivity as assessed by leave one out cross validation the resulting transfer function was then applied to two mid to late holocene sediment cores from which ostracode assemblages were sampled the late holocene conductivity records show that changes in conductivity of lakes on san salvador are broadly synchronous with times of enhanced enso activity corresponding to elevated conductivity in response to lower atlantic hurricane occurrence these results demonstrate that changing ostracode assemblages through time provide a reliable means to reconstruct past salinity and demonstrates the strong effect of enso on bahamian aridity

the effect of calibration data set selection on quantitative palaeoclimatic reconstructions quantitative palaeoclimatic reconstructions based on biological fossils are a major source of information on long term climatic variability such reconstructions typically use some kind of a modern calibration data set describing the variation of the studied biological group in present day climate space here we explore the effect of calibration data set selection on palaeoclimatic reconstructions by creating alternate calibration data sets via stratified random sampling to reconstruct mean july temperature tjul for four fossil pollen sequences from northern europe we show that palaeoclimatic reconstructions using methods based on taxon response models can be highly sensitive to the calibration data set used in particular the absolute reconstructed temperatures show great sensitivity to calibration data selection which suggests that the absolute values of palaeoclimatic reconstructions may not be robust by contrast we find the relative shapes of the reconstructed curves to be more robust to cali

the geology of eleuthera island bahamas a rosetta stone of quaternary stratigraphy and sea level history abstract a 5 km stretch of coastline in north eleuthera reveals a long and detailed stratigraphy that includes all known surficial limestone units in the bahamas and supplements the record with several previously unrecognized ones eight paleosol bounded limestone parasequences comprise at least six interglacial periods the lithostratigraphy demonstrates cyclicity at several frequencies 10 5 10 4 20 40 ka and 10 3 years and displays a variety of distal to proximal shoreline facies indicative of shifting depocenters associated with changing sea levels stratigraphy petrology pedology and whole rock aminostratigraphy are used to correlate units and subunits among the 12 described sections amino acid ratios are also converted to absolute age estimates which support the lithostratigraphy the parasequences are correlated with marine oxygen isotope stages 1 to 13 or older evidence of middle pleistocene highstands are abundant in the eleutheran stratigraphy including paleo sea levels of decreasing age at 2 m 7 m 20 m associated with stages 11 and or 9 and two near present highstands during stage 7 a complex sea level history is associated with substage 5e while substage 5a is represented by near shore aggradation of coastal dune complexes in eleuthera and throughout the bahamas concordance of sea level deposits between bermuda and the bahamas reinforce their tectonic stability while the abundance of highstand evidence during the middle pleistocene contradicts suggestions that platform subsidence has obscured all evidence of these events below present sea level the high resolution late quaternary stratigraphy of eleuthera is unrivaled among geologic records from stable carbonate coastlines and thereby offers a rosetta stone for interpretation of the quaternary evolution of the bahamas and sea level history over the past 500 ka

aluminous lateritic soils eleuthera bahamas a modern analog to carbonate paleosols abstract aluminous lateritic soils from governor s harbour eleuthera bahamas are described these soils are forming on eolian ridges under a humid tropical savanna climate the parent material is carbonate eolianite plus airborne dust from north africa the soils are thin discontinuous and concentrated in shallow solution pits they are stony have a crumb texture and are underlain by pedogenically altered limestones the solum has a low sio2 al2o3 ratio and is composed of boehmite hydroxy interlayered clay hic al hematite al goethite calcite and minor quartz the presence of carbonates in the solum buffers the ph and inhibits gibbsite precipitation resulting in a high availability of aluminum for incorporation in hic and iron minerals the moisture egime of these soils is characterized by frequent wetting and drying due to the high porosity and permeability of the underlying carbonates and the intermittent nature of the rainfall boehmite is the stable al phase within cryptovoids where the h2o activities are less than one the dominant pedogenic features in the altered limestones are voids produced by solution of limestone around plant roots these voids are subsequently infilled with overlying solum material and cemented with equigranular calcite alteration rinds containing micritized carbonate grains and laminations of micrite and iron rich clay develop around the voids features observed in aluminous lateritic soils are compared to other carbonate soils and paleosols preserved within carbonate sequences

streamflow recession in basins with multiple water storages abstract a streamflow recession formula for natural basins is derived by linear hydrologic routing of the sum of inflows from discrete independent water storages through a channel storage water storages include depression detention snow and ice channel bank aquifer and cavern evapotranspiration is incorporated in the recession formula but seasonal effects and basin wetness and storage conditions before storms are not considered data from seven basins involving 156 precipitation free recessions are used to test the performance of two and three parameter approximations to the theoretical recession formula recessions are defined to last at least 2 weeks and to begin 2 days after the peak of a basin outflow hydrograph or at a point on the falling limb 2 days after any precipitation occurs recessions end when precipitation recommences or when daily flow data stop decreasing an inverse square formula explains most variance in the two parameter case in contrast to the simple exponential formula usually recommended for recession modelling with three parameters equally good performance is shown by formulae involving a constant plus an inverse square or inverse cubic or simple exponential term these theoretically based formulae should be useful at basin scale for interpolating or extrapolating recession data particularly in basins where little is known about water storage behaviour

geochronology biostratigraphy and changing shell morphology in the land snail subgenus poecilozonites during the quaternary of bermuda shells from over 280 collections representing all known forms of subgenus poecilozonites zonitidae from bermuda have been ranked in stratigraphic order and relative age aminostratigraphy the samples were first grouped by their source lithostratigraphic unit with additional refinements being made based on the epimerization ratio d alloisoleucine l isoleucine or a i from nearly 400 representative individual shells of each of the forms a plot of a i frequency defines several modes or aminozones the aminozones correlate strongly with defined lithostratigraphy with some minor variation resulting from less optimally preserved shells the succession of land snails is ranked over chronological range from the middle and early pleistocene with greatest resolution since 500 ka this 500 ka age range and density of sampling is among the most extensive for any organism on an oceanic island morphological analysis of poecilozonites demonstrates oscillation and repetition of morphotypes over multiple sea level cycles shells from the small island s that formed during interglacial times are generally small and show little variation in form during glacial periods when bermuda reached maximal size shells are much larger extreme variation in shell size and shape occurs at interglacial glacial transitions in as little as 2 4 ka because the subgenus has been endemic to bermuda for at least ca 1000 ka such dramatic and rapid shifts in shell morphology cannot be the result of recolonization from outside sources an intact and undisturbed 130 ka long biostratigraphic record of poecilozonites is contained in a single vertical 2 m thick talus accumulation in admirals cave that has been dated at high resolution by three independent techniques the bio and chronostratigraphy show that snails were very large at the close of glacial stage marine isotope stage mis 6 small during interglacial mis 5 re evolved identical large size during the last glaciation mis 4 2 and changed abruptly to the small paedomorphic modern form at the onset of the holocene mis 2 1 about 10 12 ka ago when assessed with care shells of poecilozonites may be used as guide fossils for rapid field identification of lithostratigraphic units in surface deposits and as chronological indicators in cave and fissure fills when used in combination with vertebrate remains

late cenozoic marine deposition in the united states atlantic coastal plain related to tectonism and global climate abstract major hiatuses in upper cenozoic marine deposits in the united states atlantic coastal plain are recognized on the basis of molluscan faunal changes at erosional unconformities these hiatuses generally coincided with periods of global cooling and ice sheet formation such hiatuses provide information to supplement global climatic data major hiatuses are recognized within the early miocene 23 20 m y ago at the end of the middle miocene 11 10 m y ago at the end of the late miocene 6 5 5 m y ago at the end of the early pliocene 4 0 2 5 m y ago at the end of the late pliocene 1 9 or 1 8 m y ago within the pleistocene 1 1 0 5 m y ago and several times within the last 0 4 m y estimates of the amount of water contained in ice sheets at different times in the pliocene and pleistocene facilitate calculation of probable minimum sea levels on the coastal plain during different high stands of the sea the altitudes of dated shoreline deposits in the atlantic coastal plain show that the amount of uplift in the cape fear area has averaged at least 1 3 cm per 1000 years since the beginning of pliocene time the coastal plain of georgia has apparently experienced relatively little vertical deformation during this same time

baseflow separation based on analytical solutions of the boussinesq equation a technique for baseflow separation is presented based on similarity solutions of the boussinesq equation the method makes use of the simplifying assumptions that a horizontal impermeable layer underlies a dupuit aquifer which is drained by a fully penetrating stream the value of the baseflow maximum as well as the baseflow recession hydrograph can be estimated by fitting the analytical solutions of the boussinesq equation to the observed discharge values for individual flood events for the rising limb of the baseflow hydrograph a linear function is assumed for simplicity the method is first demonstrated on three watersheds for a total of five flood events and extensively applied over a three year period for the mahantango creek pennsylvania watershed the proposed method reduces some of the subjective aspects long associated with baseflow separation techniques

composition and diagenesis of pleistocene aeolianites at shidao xisha islands implications for palaeoceanography and palaeoclimate during the last glacial period abstract pleistocene aeolianites on shidao xisha islands are one of the rare aeolianite successions found in asia there the aeolianites which unconformably overlie pleistocene coral reefs marine isotope stage 5e are 21 8 m thick and formed largely of grains derived from heterozoan organisms including foraminifera predominantly amphistegina geniculate red algae echinoderms and molluscs the aeolian sands were probably derived from a subtropical shallow subtidal environment the variation in the distribution of metastable aragonite and high mg calcite hmc divides the aeolianite succession in core xk 1 into three intervals which are unit 1 11 5 21 8 m unit 2 3 11 5 m and unit 3 upper 3 m of core the entire aeolianite succession underwent diagenetic alterations in relatively closed diagenetic environments with low water rock ratios compared to the aeolianites in units 1 and 3 however the aeolianites in unit 2 display lower amount of hmc lower sr and mg concentrations and more negative 18o values of bulk samples this evidence demonstrates that unit 2 underwent more extensive diagenetic alteration probably due to the invasion of larger volumes of meteoric water correlation of the aeolianites in xk 1 to the aeolianites in surface exposures and subsurface core indicates that most shidao aeolianites were deposited in mis 3 the dry cold climate combined with strong onshore winds blew the exposed marine sediments onshore where they formed the aeolian dunes the palaeosols present in the shidao aeolianite succession indicate multiple episodes of subaerial exposure with relatively more humid climate collectively the results imply that aeolianites in ancient rock record can be used to examine the variations in palaeoceanography and the palaeoclimate