changes in coral reef structure through the miocene in the mediterranean province adaptive versus environmental influence well documented mediterranean examples of miocene carbonate platforms with complete exposures from shallow water to basinal facies provide evidence for temporal changes in reef building capacity of zooxanthellate corals in pre late tortonian platforms small coralgal patches and mounds occur from platform top to the toe of slope but they did not build to sea level in contrast barrier reefs with unequivocal reef crest structures that reached sea level are documented in late tortonian early messinian platforms we suggest that a change in both calcification rates and bathymetric zonation was the result of coevolution of corals and symbiodinium zooxanthellae coeval to global cooling and at least at a regional scale a geochemical change that supported widespread aragonite precipitation through the late miocene

assessing the reliability of magnesium in foraminiferal calcite as a proxy for water mass temperatures though many studies on the mg contents in the calcitic tests of foraminifers exist the processes controlling its uptake are still a matter of debate laboratory cultures offer an excellent opportunity to reveal these mechanisms the mg concentrations within single chambers of the planktic foraminifer globigerinoides sacculifer brady maintained under controlled laboratory conditions were measured 1 at variable temperatures 19 5 29 5 c and constant salinity and 2 at variable salinity 22 45 and constant temperature the experimental results suggest that under natural conditions temperature is the leading mechanism controlling the mg ca ratio temperature and magnesium are related proportionally a temperature increase of ca 10 c gives rise to an increase of the magnesium concentrations of ca 130 drastic unnatural salinity changes dominate the effects of temperature a 110 change in the mg ca ratio was observed when salinity was elevated or reduced by more than ca 10 specimens which underwent gametogenesis reveal significantly higher mg concentrations than specimens that did not release gametes partition coefficients for mg in foraminiferal calcite are orders of magnitude lower than values from inorganically precipitated calcite when comparing observed mg ca ratios of foraminiferal tests with predicted mg ca ratios calculated according to empirical equations it becomes evident that foraminiferal tests are undersaturated with respect to mg for the water temperature they have experienced apparently foraminifers are capable of controlling their mg concentration the physiological processes presumably responsible for such depressed mg ca ratios appear to be temperature controlled as deduced from the close relationship of the observed mg ca ratios and water temperature this study demonstrates that variations in temperature and salinity are definitely reflected in the mg content of foraminiferal tests magnesium may thus serve as a paleo proxy for past surface water temperatures as long as postdepositional changes and salinity variations are of subordinate importance or can be excluded

modelling the effect of evaporation on the salinity 87 sr 86 sr relationship in modern and ancient marginal marine systems the mediterranean messinian salinity crisis abstract palaeosalinity reconstructions in marginal marine environments based on sr isotope data assume simple two end member mixing of river and ocean water an improved model that incorporates the effect of evaporation is used to demonstrate that this approach is not valid in evaporation dominated systems however sr isotope records combined with faunal and lithological constraints on salinity can be used to assess the palaeohydrological conditions of ancient marginal marine systems this new method is used to interpret deviations from the global seawater sr isotope curve observed in mediterranean successions during and up to 3 myr prior to messinian evaporite deposition results suggest that no absolute change in the net evaporation flux is required to explain the three to four fold rise in salinity of mediterranean water at the carbonate evaporite transition modelled sr isotope records indicate that this increase in salinity was synchronous with an increase in the dominance of atlantic water inflow in the hydrological budget of the mediterranean the messinian salinity crisis may therefore have been the response to a marine transgression

distinguishing climatic and tectonic signals in the sedimentary successions of marginal basins using sr isotopes an example from the messinian salinity crisis eastern mediterranean the evolution of oceanic 87 sr 86 sr through the tertiary has been sufficiently well documented to provide a useful stratigraphic tool for carbonate rich marine sediments which were deposited in basins connected to the global oceans in isolated basins sea water 87 sr 86 sr will diverge from coeval oceanic values thus if independent age information exists the geochemical signature can constrain the timing of isolation in marginal basins formed in tectonically active settings the timing of isolation is critical to the assessment of the relative importance of climate or tectonic controls on that event previously isolation has been assumed to coincide with the last occurrence of open marine fauna however in an example from the eastern mediterranean 87 sr 86 sr data challenge that assumption and can be interpreted as indicating a protracted period of isolation c 3 ma during which time marine conditions prevailed prior to the messinian salinity crisis at the end of the miocene this allows tectonic and climatic signals to be distinguished since although convergence of africa with eurasia was responsible for isolation of this part of the mediterranean it is more likely that later climatic change triggered desiccation

the tortonian salinity crisis of the eastern betics spain the late miocene depositional history of the lorca and fortuna basins both occupying an internal position in the eastern betics of spain is marked by a regressive sequence from open marine marls via diatomites and evaporites to continental sediments based on facies similarities these evaporites have often been correlated to the well known mediterranean evaporites of the messinian salinity crisis although this correlation was never substantiated by reliable chronological data in this paper we present an integrated stratigraphy of this regressive sequence which shows that the evaporites of the lorca and fortuna basins are entirely of late tortonian age and as such have no relation with the messinian salinity crisis the main phase of basin restriction resulting in deposition of diatomites and evaporites took place at 7 8 ma while the last marine deposits massive evaporites of the lorca basin are dated at 7 6 ma consequently this tortonian salinity crisis of the eastern betics had a duration of approximately 200 kyr while continental deposition prevailed throughout the entire messinian as also revealed by the fossil mammal record the tortonian salinity crisis of the eastern betics is obviously related to a local phase of basin restriction caused by uplift of the metamorphic complexes at the basin margins probably in concert with strike slip activity along sw ne trending fault systems the development of a submarine sill is of crucial importance for the increase in salinity because it allows marine waters to continuously enter the basin at the surface while it restricts or prevents the outflow of dense saline waters at depth furthermore we show that evaporite and diatomite cyclicity in these restricted basins is predominantly related to precession controlled circum mediterranean climate changes and that glacio eustatic sea level changes only play a minor role it is remarkable that the lithological sequence of the tortonian salinity crisis mimics in many aspects that of the messinian salinity crisis this suggests that the diatomaceous facies is an essential part of the lithological sequence associated with basin restriction fl 2000 elsevier science b v all rights reserved

chemical labelling of oyster shells used for time calibrated high resolution mg ca ratios a tool for estimation of past seasonal temperature variations abstract the geochemical compositions of biogenic carbonates are increasingly used for palaeoenvironmental reconstructions the skeletal 18o temperature relationship is dependent on water salinity so many recent studies have focused on the mg ca and sr ca ratios because those ratios in water do not change significantly on short time scales thus those elemental ratios are considered to be good palaeotemperature proxies in many biominerals although their use remains ambiguous in bivalve shells here we present the high resolution mg ca ratios of two modern species of juvenile and adult oyster shells crassostrea gigas and ostrea edulis these specimens were grown in controlled conditions for over one year in two different locations in situ monthly mn marking of the shells has been used for day calibration the daily mg ca ratios in the shell have been measured with an electron microprobe the high frequency mg ca variation of all specimens displays good synchronism with lunar cycles suggesting that tides strongly influence the incorporation of mg ca into the shells highly significant correlation coefficients 0 70

significance of weathering himalayan metasedimentary rocks and leucogranites for the sr isotope evolution of seawater during the early miocene changes in 87 sr 86 sr ratios of seawater may reflect varying rates of chemical weathering or variations in the isotopic compositions of continental rocks undergoing weathering the unusually high dissolved sr concentrations and 87 sr 86 sr ratios that characterize the ganges and brahmaputra tsangpo river systems are a consequence of weathering early proterozoic age metasedimentary rocks and anatectic miocene granites exposed on the southern slopes of the himalayas on average the metasedimentary rocks are characterized by abundances of 87 sr about twice those of the derived granites the rapid rise in 87 sr 86 sr ratios of seawater during the early miocene was virtually coincident with metamorphism and anatexis of himalayan metasedimentary rocks model calculations indicate that 50 75 of the overall change in 87 sr 86 sr ratios for seawater between 20 and 15 ma could have resulted from exposure of himalayan metasedimentary rocks to chemical weathering rapid tectonically controlled exhumation of the metasedimentary rocks is required to expose these lithologies by 20 18 ma to generate the increase in the 87 sr flux of the trans himalayan rivers during the early miocene

an estimate of ice drifted sediments based on the mud content of the ice cover at montmagny middle st lawrence estuary abstract recent measurements made at montmagny a locality on the south shore of the middle st lawrence estuary 70 km northeast of quebec city 47 n give an idea of the volume of fine grained sediments incorporated in the ice cover and allow an estimation of the annual load drifted by ice at this locality a mean thickness of 10 cm of mud was encountered in the ice cover over an area of approximately 20 km 2 thus the total load of fines may be as much as 4 10 6 tonnes t it is estimated that upon melting at break up about 15 of this load returns to the montmagny tidal flat while the remaining volume is carried to the offshore zone considering breakup characteristics it is estimated that about 1 5 2 10 6 t of fines return to the turbidity zone while the remaining load is ice drifted outside that zone since the shore area of the middle st lawrence estuary covered by ice during the winter is approximately 60 km 2 it is calculated that a load of 5 6 10 6 t of sediment incorporated in the ice cover could escape from the turbidity zone annually to this load should be added another 4 10 6 t of suspended matter which come from the freezing in situ of the turbid water in the offshore zone an annual output by ice drifting of 10 10 6 t of sediment is thus likely and is in great contrast to the output during the ice free season of approximately 1 10 6 t in the middle st lawrence estuary the annual output almost equals the input consequently the sediment budget is virtually in a state of equilibrium which helps to explain why there is very little permanent mud deposition in the shore and offshore zones today it is concluded that ice processes largely control the sedimentary budget of the turbidity zone of the middle st lawrence estuary a particular environment within a mid latitude inner continental shelf which is partly dominated by ice

carbonate lithofacies as paleolatitude indicators problems and limitations abstract detailed study of miocene carbonates in the mediterranean region and their analogues on modern carbonate shelves in the mediterranean sea brazil and other areas reveals at least three major types of carbonate platform lithofacies in addition to the classic tropical coral reef chlorozoan lithofacies a chloralgal lithofacies similar to the chlorozoan but without hermatypic corals b rhodalgal lithofacies characterized by abundant encrusting coralline algae and c molechfor lithofacies consisting of benthic foraminifers molluscs echinoids bryozoans and barnacles these carbonate lithofacies present complex distribution patterns seemingly related primarily to latitude and depth that control water temperature although other factors e g water circulation river discharge suspended sediment controlling water salinity and temperature nutrient content light penetration etc also play important roles chloralgal and rhodalgal lithofacies can be considered two transitional terms between the two end members the chlorozoan lithofacies which characterizes shallow tropical shelves and the molechfor lithofacies which characterizes colder and or deeper areas detailed textural and sequential analysis are required for satisfactory interpretation of these lithofacies in ancient rocks

paleobiogeography of scleractinian reef corals changing patterns during the oligocene miocene climatic transition in the mediterranean abstract during the oligocene miocene greenhouse to icehouse climatic transition the biogeography of reef corals or zooxanthellate like scleractinian corals was gradually changing from a pan tropical tethyan province in the eocene to three reef coral provinces of the western atlantic caribbean indo pacific and mediterranean our reefcoral database encompasses updated and homogenized data on paleoenvironmental and systematics of scleractinian corals occurring in the oligocene and miocene outcrops from circum mediterranean regions provided by most of relatively recently published data in the literature and by the study of published and unpublished collections of coral specimens from the same area including the important collections housed at the mnhn paris and our own collections as there is no validated direct criterion for the identification of the coral zooxanthellate symbiosis in the fossil record and considering the difficulty to use the biogeochemical approaches in the context of this study the subjectivity of the morphological criteria and the relative recent age of the fossil corals we are dealing with a uniformitarian approach has been used for inferring the symbiotic status of scleractinian genera in reefcoral among the 158 genera included in our database 93 can be considered as zooxanthellate and 10 have a doubtful zooxanthellate status this relatively exhaustive database was used to reconstruct the temporal and spatial distribution of scleractinian corals in the mediterranean during the oligocene miocene time in order to discuss the interplaying effects of the global cooling at that time the re organization of the tethyan realm resulting from the african arabian and eurasian plate collision and the emergence of the alpine chains driving the gradual northward movement of the whole region outside the tropical subtropical belt it is shown that the structure of the mediterranean z coral oligocene miocene paleobiodiversity was characterized by many geographically restricted genera with a moderate to short stratigraphical range and a few long ranging widespread genera a major consequence of this structure is that the extinction pattern has proceeded through the preferential extinction of rare occurrence genera through time the potential rapid long distance dispersal of most coral larvae compared to the size of the oligocene miocene mediterranean explains why no biogeographical subprovinces can be distinguished for the z coral fauna on a local scale ecological processes tend to sort coral taxa by limiting z coral development to geographically restricted and discontinuous areas this accounts for the large amount of geographically restricted taxa forming the mediterranean coral fauna the interaction of plate tectonics alpine orogenesis and climate at local to subregional scales exerts strong controls over the spatio temporal distribution of z coral assemblages within the circum mediterranean realm in particular we suggest that the richness and composition of the eastern atlantic coral fauna are indirectly related to the opening and closure of the eastern seaway connection with the indian ocean which controlled the e w circulation of surface waters and hence the westwards dispersal of pelagic larvae at the scale of the whole region the gradual regional climatic change produced by the northwards migration of the entire area superimposed on the global cooling appears in large part responsible for the extinction pattern of z corals through time in the mediterranean biogeographical province

evidence of recycling of isotopically light co2 aq in stratified black shale basins contrasts between the whitby mudstone and kimmeridge clay formations united kingdom calculation of co 2 aq and p co 2 atm based on proxy temperature and salinity data 18 o and 13 c from belemnite rostra and 13 c toc toc total organic carbon from toarcian marine organic rich shales yields unreasonably large intraformational p co 2 atm variations we postulate that the low 13 c toc values in the shales can instead be explained by episodic release of isotopically light co 2 that had built up below a relatively deep pycnocline halocline the lowest 13 c toc values would thus be associated with mixing and erosion of the pycnocline following extended periods of stable stratification in contrast the studied tithonian oil shales were probably deposited during periods of only slight perturbation of a photic zone chemocline which probably led to only modest release of isotopically light co 2 in addition the higher productivity associated with the nutrient release would have resulted in depletion of the mixed layer co 2 leading to lower fractionation and higher 13 c toc values

orbitally tuned sr isotope chemostratigraphy for the late middle to late miocene we present a sr chemostratigraphic reference section for the late middle to late miocene 14 5 ma from ocean drilling program site 926 on the ceara rise this site combines a precise orbitally tuned timescale with a high sedimentation rate 15 m m y continuous deposition and excellent biostratigraphic control the sr isotope curve is based on measurements of cleaned planktonic foraminifera at 100 200 kyr sample intervals and it illustrates periods of rapid change in 87sr 86sr alternating with periods of little change chemostratigraphically defined ages for these intervals can be determined within 0 8 m y and 1 6 m y respectively there is excellent correlation with the published curve for site 588 hodell and woodruff 1994 however the curve for site 747 oslick et al 1994 exhibits less structure which may be due to small errors in age estimates related to slow sedimentation rates high latitude fauna and an interval of complicated magnetics late miocene data compare favorably with data from site 758 farrell et al 1995

strontium isotopic composition of modern and holocene mollusc shells as a palaeosalinity indicator for the baltic sea abstract the 87sr 86sr isotope ratio in subfossil carbonate mollusc shells from raised beach sediments is used as a palaeosalinity indicator for the baltic sea the main purpose is to demonstrate the applicability of the method in a formerly glaciated area using 87sr 86sr ratios found in modern shells mytilus edulis macoma baltica and radix balthica to elucidate the parameters and conditions to be used for palaeosalinity determinations based on subfossil shells proxy salinity data are calculated assuming that the sr concentration in baltic sea water is controlled by a two component conservative mixing between seawater and river water based on replicate determinations of the 87sr 86sr ratio in modern shells proxy salinity data can be quantified with a relative precision of better than 5 for salinities up to 10 comparison with measured present day salinities indicates that the accuracy is generally better than 5 for the proxy data with this precision and accuracy the present day salinity differences between the major baltic sub basins bothnian bay bothnian sea and baltic proper can be detected palaeosalinities were determined using subfossil shells m edulis and m baltica with calibrated 14c ages of 6770 3070 cal bp the shell deposits occur from 65 m a s l down to the present day sea level the palaeosalinities determined for the bothnian bay 4 8 10 3 and the bothnian sea 7 3 10 3 are in good agreement with earlier estimates of the maximum littorina sea stage palaeosalinity in these sub basins 8 10 at one locality two different shell species from the same shell deposit were dated m edulis and m baltica the shells differed in age by 460 70 14c years a possible indication that the ecological conditions at a locality may have been favourable to different faunas at different times

dolomite abundance and stratigraphic age constraints on rates and mechanisms of phanerozoic dolostone formation increasing dolomite abundance with age relative to limestone has long been accepted as one of the general truisms of sedimentary geology a relationship which suggests that dolomitization is a cumulative process occurring slowly over the full burial history of a carbonate sequence however reevaluation of data in support of this assumption indicates that although relative dolomite abundances do change significantly throughout phanerozoic carbonate sequences no data set demonstrates any direct correlation between dolomite content and age whereas tabulation of available data does suggest greater amounts of dolomite formation during periods of continental flooding global mass balance calculations of potential magnesium sources also indicate that most dolomite has formed from marine or marine derived fluids at the earth9s surface this conclusion is indirectly supported by significant short term period scale changes in phanerozoic dolomite abundance a variation which would be more attenuated if dolomitization were dominantly a burial process dolomitization may be enhanced during times of global transgression higher atmospheric pco 2 and lower calcite saturation state in shallow marine settings

platforms of the nicaraguan rise examples of the sensitivity of carbonate sedimentation to excess trophic resources the nicaraguan rise is an active tectonic structure in the western caribbean carbonate accumulation on its platforms has not kept pace with relative holocene sea level rise despite a tropical location remote from terrigenous sedimentation trophic resources apparently exceed levels favoring coral reef development because sponge algal communities dominate the drowning western platforms in contrast to mixed coral algal benthos on pedro bank and well developed coral reefs along the north coast of jamaica concentrations of biotic pigments in sea surface waters show a corresponding west east gradient oceanic waters flowing over the western banks carry nearly twice as much biotic pigment as oceanic waters north of jamaica sources enriching the western caribbean are terrestrial runoff upwelling off northern south america and topographic upwelling over the nicaraguan rise that relatively modest levels of trophic resources can suppress coral reef development holds important implications for understanding carbonate platform drownings in the geologic record

ice rafting of fine grained sediment a sorting and transport mechanism beaufort sea alaska abstract the presence of turbid sediment rich fast ice in the arctic is a major factor affecting transport of fine grained sediment turbid ice was found to be present in a zone 10 to 20 km wide along the coast of the beaufort sea sediment concentrations observed in cores taken in seasonal fast ice ranged from 3 to more than 1 600 g m3 finely disseminated silt and clay sized particles dominated discoloring the upper segments of the cores in a layer up to 1 m thick in almost all of the cores the upper most 10 cm of ice was relatively less turbid and the relief at the base of the turbid layer was 10 to 20 cm over distances of 1 to 2 m observers have documented the widespread sporadic occurrence of sediment rich fast ice in both the beaufort and bering seas the known sources a d transport relations of suspended sediment did not explain this distribution of turbid ice the occurrence of sediment in only the upper part of the seasonal fast ice indicates that sediment rich ice forms early during ice growth the most likely mechanism for the formation of sediment laden ice and preferential sorting of fine sediments requires resuspension of nearshore bottom sediment during storms accompanied by formation of frazil ice and subsequent lateral advection before the fast ice is stabilized we estimate that the sediment incorporated in the beaufort ice canopy formed a significant proportion of the seasonal influx of terrigenous fine grained sediment the dominance of fine grained sediment suggests that in the arctic and sub arctic these size fractions may be ice rafted in greater volumes than the coarse fraction of traditionally recognized ice rafted sediment the incorporation and transport mechanism may be a significant factor in the transport of fine grained sediments in the arctic basin

history and evolution of the north betic strait prebetic zone betic cordillera a narrow early tortonian tidal dominated atlantic mediterranean marine passage abstract the north betic strait located in the prebetic zone outermost part of the betic cordillera was a narrow seaway connecting the atlantic ocean and the mediterranean sea through the betic cordillera during the early late miocene strait facies consist of heterozoan bioclastic carbonates and mixed siliciclastics carbonates local fan delta deposits conglomerates also occur the north betic strait deposits exhibit huge trough cross bedded structures single troughs are up to 5 m high and point to the east in easternmost outcrops in central outcrops they reach up to 15 m in height and some tens of metres in length and point both to the east and to the west the westernmost outcrops show the largest cross bedded structures up to 20 m in height and some hundred of metres in length all pointing to the west the large scale cross bedding was generated by the migration of very large dunes moved by tides the largest structures are inferred to have formed at depths of 90 m depth estimations indicate that the north betic strait shallowed to the east and deepened to the west the miocene evolution towards the formation of the north betic strait can be divided into a series of steps the palaeogeography evolved from a south facing platform marginal to a northeastern relief to a wide open marine passage limited by a southern platform and finally to a tidal dominated strait the closing of the north betic strait is recorded by the presence of lagoonal silty sediments covered by a stromatolite layer and crowned by a red soil in the westernmost outcrops

contrasting watermass conditions during deposition of the whitby mudstone lower jurassic and kimmeridge clay upper jurassic formations uk abstract the whitby mudstone formation wmf and kimmeridge clay formation kcf are both jurassic organic rich black shale units containing well preserved marine organic matter despite such gross similarities they exhibit opposite trends in 13 c toc versus wt decarbonated total organic carbon toc r 0 76 for wmf and 0 71 for kcf the 13 c toc versus toc trend also varies geographically within both units only the kcf data exhibit a positive correlation between 13 c toc and 15 n org r 0 76 and the presence of aryl isoprenoids probable indicators of photic zone anoxia maturity differences are insufficient to explain such contrasts bulk and compound specific isotopic variations in the kcf are interpreted largely as a reflection of primary productivity during deposition rather than a dominantly diagenetic signal due to incorporation of sulphurised carbohydrate the contrasts between the formations and the geographic variation in coeval shelf sediments are explained by a model stressing the relative positions and stabilities of the chemocline pycnocline nutricline and euphotic zone and the effect these have on productivity co 2 recycling and bacterial floras

reconstructing estuarine conditions oyster shells as recorders of environmental change southwest florida abstract live collected shells of the oyster crassostrea virginica contain geochemical records of modern temperature and salinity so records of prehistoric conditions may be obtained from subfossil shells restoration of channelized watersheds in florida is receiving much attention and plans for targeted watersheds require information about estuarine conditions before channelization lack of historical records necessitates alternative methods to understand pre disturbance conditions a 14c calibrated amino acid geochronology based on racemization of glutamic acid yielded ages ranging from 190 1220 ad and from 1270 1860 ad for subfossil oysters from blackwater river near natural watershed and for faka union bay channelized watershed respectively 18o and 13c values of subfossil shells from blackwater river indicate salinity and summer temperatures similar to present winter temperatures recorded in shells from 190 590 720 and 1050 ad appear 1 5 c colder than present winter temperatures whereas the shell from 1220 ad records winter temperatures similar to modern winter temperatures these temperature shifts may indicate change in climate or natural seasonal variation of winter temperature from year to year subfossils from faka union bay may reflect a complicated hydrology which cannot be evaluated by isotopic compositions alone and demonstrates the need for development of independent elemental proxies for temperature and salinity decreases in 13c from subfossil to modern shells may in part result from co2 added to the atmosphere from fossil fuel burning the suess effect subfossil 13c that is 1 more positive than modern shells suggest a change in the dominant carbon sources from terrestrial c4 or aquatic plants to c3 plants mangroves

compaction and decompaction algorithms for sedimentary carbonates abstract the mechanical compaction behavior of shallow marine carbonate sediments has been investigated to develop carbonate compaction algorithms and decompaction curves that can be used in stratigraphic restoration backstripping analyses and quantitative models for simulation of carbonate stratigraphy deep water chalks and calcareous oozes are not treated here empirical porosity depth data for carbonate sediments have been compiled and compared with experimentally derived compaction curves to derive appropriate porosity depth curves for shallow water carbonate muds and sands the curves are exponential in form this review indicates that mud rich shallow marine carbonates behave differently than sand rich grain supported sediments with regard to reduction in porosity and thickness quantitative analysis of compaction behavior in carbonate sediments reveals that barring early cementation carbonate muds suffer significant thickness reduction early in their burial history and at shallow depths e g 50 thickness reduction with about 150 200 m overburden however primary porosities of carbonate muds approximately 70 80 are reduced only to about 42 under that overburden thus the potential exists for significant retention of primary porosity in carbonate muds in the form of microporosity this indicates that interparticle cementation with or without chemical compaction is required to transform muddy carbonate sediments into lithified rock in the absence of early lithification carbonate sands compact more slowly than muds primary interparticle porosities of about 40 45 can be maintained in the first 200 300 m of burial with little thickness reduction

estimating mediterranean oligocene miocene sea surface temperatures an approach based on coral taxonomic richness abstract during the oligocene and miocene shallow water carbonates of the mediterranean region were rich in scleractinian corals thriving within various depositional settings including different reef types their diversity patterns although related to a complex interplay between a suite of environmental factors and palaeobiogeography are considered to be strongly controlled by climate variability and changes in sea surface water temperature by using the quantitative relationship between present day coral taxonomic richness and prevailing sea water temperature underlined by the so called energy hypothesis we test zooxanthellate coral generic richness values from a selection of 102 oligocene miocene localities of the mediterranean region as a proxy for relative palaeotemperatures for each oligocene miocene stage generic richness values per z coral site are firstly examined together with variations of the mediterranean z coral generic pool for better testing the method and assessing its potential application patterns of generic richness and inferred palaeotemperatures are then compared with global palaeoclimatic curves based on marine oxygen stable isotopes data or other climate proxies such as palaeoclimatic records from european continental floras and from fossil coral linear extension rate results clearly show that fluctuations of coral richness derived palaeotemperatures correspond relatively well with global changes of sea water temperature especially for the entire oligocene the chattian aquitanian boundary and the late miocene the well known mid miocene climatic optimum however is not recorded suggesting that regional factors acting together with important palaeogeographical changes exerted a strong control on the generic richness of mediterranean z coral communities a remarkable decline of taxonomic richness is recorded after the burdigalian together with a gradual decrease of palaeotemperatures in the region from the middle miocene onwards to the messinian however an increase in the temperature range of z coral localities is clearly visible indicating that z coral communities were able to thrive and adapt to a wider temperature range as the mediterranean was gradually migrating northwards outside the tropical belt the energy hypothesis if used at global or regional scale can be considered a promising and reliable method for estimating cenozoic palaeotemperatures from coral or other suitable fossil assemblages of shallow water carbonates

discrepancy between sr isotope and biostratigraphic datings of the upper middle and upper miocene successions eastern north sea basin denmark abstract one hundred and fifty six 87sr 86sr analyses have been performed on 129 samples from 18 outcrops and boreholes in oligocene miocene deposits from jylland denmark these analyses were mainly conducted on mollusc shells but foraminiferal tests bolboforma and one shark tooth were also analysed the main purpose of the study is to compare the ages of the danish succession suggested by the biostratigraphic zonation on dinoflagellate cysts dybkjaer and piasecki 2010 with the ages based on analyses of the 87sr 86sr composition of marine calcareous fossils in the same succession analyses of samples from the danish brejning vejle fjord klintinghoved arnum odderup hodde ornhoj and gram formations gave ages between 25 7 my late oligocene and 10 3 my late miocene the sr isotope ages from the lower part of the succession i e brejning to odderup formations agree with the age estimates based on biostratigraphy however the 87sr 86sr ratios of fossil carbonates from the middle upper miocene hodde to gram succession consistently indicate ages older than those recorded by biostratigraphy post depositional processes as an explanation for this offset are inconsistent with good preservation of shell material and little reworking a palaeoenvironmental cause for the observed mismatch is therefore indicated search for geological events that could explain the older ages obtained by sr isotope compositions have not led to any conclusions and we had recognised the same problem in earlier reports and communications we conclude that this is a general and possibly global middle late miocene problem that has to be reconsidered and explained geologically

freshwater discharge and sediment dispersal control on growth ecological structure and geometry of late miocene shallow water coral ecosystems early tortonian crete greece abstract insolation driven oceanographic changes are well documented in the mediterranean deep sea record and reflect episodes of high precipitation and or freshwater discharge in the shallow water record however changes in relative sea level and sea surface temperature are usually regarded as prime controls on miocene coral reefs whereas pulses of freshwater influx represent a hitherto unrecognized factor influencing their growth ecological structure and geometry on the island of crete nw messara basin greece early tortonian coral biostromes occur associated with deltas along the basin margin and rimming islands formed by large uplifted tectonic blocks in turbid delta environments apomarma area coral biostromes were almost monogeneric without any lateral zonation and being formed almost exclusively by dense stands of branching porites encrusting and boring biota are very rare whereas pyrgomatid barnacles are common dwellers of the coral skeleton a pattern interpreted to reflect complete cover of coral skeletons by tissue although most corals are not preserved in life position they were not significantly displaced because coral debris was stabilized by subsequent overgrowth of encrusting platy porites and some nodular siderastraea or renewed growth of toppled specimens burial of corals by clastic sediments episodically occurred in response to allo and autocyclic processes sea level changes sediment discharge variability and delta dynamics resulting in a stack of alternating coral biostromes and sheet like clastics in settings protected from strong sediment influx along offshore islands psalidha ambelousos area massive coral growth forms prevailed in biostromes with a higher diversity constructor guild porites tarbellastraea acanthastraea coral skeletons were strongly affected by boring sponges and bivalves and exhibit some biogenic incrustations although rhythmic sediment influx did not occur constructional coral growth rhythmically ceased this growth pattern prevented the development of massive reef cores but gave rise to a vertically stacked biostrome complex its aggradational growth with minor progradation and the high thickness of the whole carbonate body 15 m is unique for central crete and a reflection of synsedimentary tectonic block uplift that kept the relative sea level locally at a stillstand all outcrops presented in this study underline the relevance of synsedimentary tectonics and sea level fluctuations on sediment dispersal and accumulation in coral ecosystems nevertheless the facies comparison of three contrasting reef settings reveals that rhythmic reef demise was also occurring in settings without appreciable siliciclastic flux occasionally accompanied by brackish biota it is concluded that pulses of freshwater discharge have been a so far unnoticed regulating parameter for shallow water carbonate production and must therefore be taken into account at the reconstruction of tortonian nearshore ecosystems of the mediterranean region

sedimentary and diagenetic markers of the restriction in a marine basin the lorca basin se spain during the messinian abstract the lorca basin southeastern spain is part of a chain of small marginal neogene basins located in the structurally active betic area the upper miocene messinian sequence is composed of a thick diatomite bearing series tripoli unit overlain by the main evaporites analogous to the classical succession that records the main events during the salinity crisis in the mediterranean region the shallow restricted conditions of this region amplified the sedimentary responses to local and global forcings an integrated approach using sedimentology micropalaeontology stable isotope geochemistry and organic geochemistry has been applied to the tortonian messinian succession of the lorca basin in order to obtain a continuous record of the environmental changes the sediments record two major events which affected the whole mediterranean 1 high levels of productivity that led to the formation of the diatomite bearing deposits in the early messinian tripoli and 2 the messinian salinity crisis with its two major stages represented by the halite and gypsum units both mainly precipitated from marine derived brines the rapid reflooding of the mediterranean by normal marine waters at the base of the pliocene did not reach the lorca basin nor other basins of this part of the betic area instead continental sediments were deposited as a consequence of the regional uplift of se iberia which started close to the messinian pliocene boundary the most prominent feature of this basin concerns the record of its restriction by the time of the deposition of the tripoli unit which led to intercalations of precursor evaporitic layers consisting of ca sulphate deposited in sub aqueous and sabkha conditions interbedded with diatomites this alternation of evaporites and diatomites proves that the lorca basin was periodically restricted and reflooded by marine waters a possible cause for this being relative sea level fluctuations in the mediterranean this strengthens evidence of diachronism that suggests that the onset of the first messinian evaporitic deposition was not synchronous but was dependent on bathymetry and local tectonics high productivity during the early messinian in this basin is demonstrated by the thick deposits of diatomites however stagnation episodes may have occurred during this interval as suggested by the preservation of high amounts of organic matter organic rich shales and the extent of bacterial sulphate reduction which apparently occurred during early diagenesis the formation of organo sulphur compounds replacement of sulphates by carbonates and the high levels of elemental sulphur are by products of diagenetic processes occurring in a restricted hypersaline environment

facies successions in the pre evaporitic late miocene of the lorca basin se spain abstract pre evaporitic uppermost tortonian to messinian carbonate siliciclastic deposits have been studied in the western part of the lorca basin individual lithofacies facies associations as well as facies successions and stratal architecture indicate a gravel rich fluvial dominated gilbert type delta environment during periods of decreasing terrigenous supply carbonate sedimentation predominated including formation of patch reefs and fringing reefs the observed progradational stacking pattern of facies successions is attributed to a 3rd order eustatic highstand that pre dates the messinian lowstand evaporites of the well known salinity crisis five facies successions have been recognized each succession is composed of three facies associations that are mixed carbonate siliciclastic mcs carbonate dominated cd and siliciclastic dominated sd they show retrogradation aggradation progradation architecture and represent 4th order transgressive regressive cycles the five successions can be correlated through the whole basin and are interpreted as a useful tool for basinwide sequence stratigraphic correlation if in addition other recently published data from se spain are considered it may turn out that future correlations between different neogene basins at this cycle scale 4th order will be possible higher frequency successions or cycles at a bed or bedset scale 5th or higher order are noticeable but are clearly related to local depositional processes facies dynamics they do not have any significance for a basinwide sequence stratigraphic correlation

palaeoceanographic controls on reef deposition the messinian cariatiz reef sorbas basin almeria se spain abstract the cariatiz section lies at the toe of the palaeoslope of the messinian cariatizfringing reef at the northern margin of the neogene sorbas basin in se spain distal slope reef deposits in the upper part of the section can be traced laterallyto the reef core of the last episodes of reef progradation the underlyingdeposits are alternating diatomitic marl marl and silty marl that intercalatewith sandstone beds combined lithological changes variations in proportionsof warm water planktic foraminifera and d18o values suggest that at leastseven probably precessional cycles are recorded throughout the cariatizsection the correlation of seven cycles in the pelagic deposits to seven reefprogradation cycles and associated vertical shifts in reef facies indicatesrelative sea level oscillations of several tens of metres biostratigraphic andpalaeomagnetic data suggest that both the cariatiz section and the fringing reefformed during the reverse polarity chron c3r surface water temperaturesseem to be the major factor controlling carbonate production in the reef system deposition of bioclastic calcirudite and calcarenite with no active coralgrowth took place at the lowest sea level within each reef cycle duringtemperature minima within each precessional cycle porites framework andreef slope deposits with halimeda gravel in contrast formed duringtemperature rises and thermal maxima within precessional cycles keywords messinian palaeoceanography planktic foraminifera reef car bonates sorbas basin stable isotopes introductiona number of palaeoceanographic studies havebeen carried out on the messinian pre evaporiticdeposits from the mediterranean region i e vergnaud grazzini 1985 benson et al 1991 krijgsman et al 1999a blanc valleron et al 2002 sierro et al 2003 stable isotope micro palaeontological and sedimentary records indi cate varying degrees of restriction of themediterranean sea from the atlantic before theonset of the messinian salinity crisis and stressthe cyclic nature of changes in hydrographicconditions speci cally oscillations in the com position of microfossil assemblages lithology andstable isotope signals re ect climatic cyclityforced by precession sprovieri et al 1996 blanc valleron et al 2002 sierro et al 2003 in addition many reports have dealt with thestratigraphic and palaeogeographic distribution structure and composition of messinian coralreefs that developed at the margins of mediterra nean basins dabrio et al 1981 pomar 1991 riding et al 1991 braga marti n 1996 estebanet al 1996 up to now however the relation ships between the environmental changes recor ded in the reef carbonates and those re ected inequivalent pelagic deposits have been poorlysedimentology 2007 54 637 660

global circulation thermal structure and carbon monoxide distribution in venus mesosphere in 1991 abstract millimeter wave observations of co lines have provided a detailed picture of venus mesosphere dynamics in 1991 from simultaneous measurements of absolute wind velocities in two layers and of temperature and co horizontal and vertical profiles at 75 115 km venus circulation at 90 110 km was characterized in 1991 by the superposition of a zonal retrograde flow and a subsolar to antisolar flow of approximately equal velocities increasing from about 40 15 m sec at 95 km to 90 15 m sec at 105 km altitude the magnitude of the increase of the ss as flow is consistent with venus thermosphere general circulation models vtgcm at 105 km the data further indicate a cos latitude dependence of the zonal flow and marginally suggest the presence of a poleward meridional component of 35 30 m sec no obvious day to day variations of the circulation are evident in the data at the 20 m see level thermal profiles in the low latitude region appear to be consistent with the pioneer venus nightside profile except above 110 km where they are somewhat colder high latitude warming is still found but mid latitudes appear to be colder than the equator the atmosphere appears to be in cyclostrophic balance up to about 105 km the horizontal distribution of co on venus nightside is essentially uniform both in latitude and in local time this behavior agrees with vtgcm simulations in which the zonal flow velocity is prescribed to match the observations comparison with previous wind measurements indicates that the zonal flow experiences dramatic long term variations this variability along with short term fluctuations of the mesospheric zonal flow evidenced by the variability in the o2 nightglow emissions apparently controls the co and o2 nightglow distributions gravity wave activity is a plausible mechanism that can drive these variations

depletion of 13c in seawater σc02 on modern carbonate platforms significance for the carbon isotopic record of carbonates seawater co2 from modern carbonate platforms bahama banks and florida is depleted in 13c by as much as 4 relative to open ocean water depletion in 13c is caused by isotopically light co2 input from respiration of marine and terrestrial organic matter during water mass residence on the bank as such depletion in 13c is related to changes in water chemistry driven by evaporation freshwater discharge and caco3 withdrawal deviation of modern platform seawater 13c values away from those of surface seawater suggests that 13c values of ancient cratonic carbonate must be cautiously interpreted initial depositional environment as well as alteration during diagenesis must be considered in extracting valid secular trends for oceanic 13c variation

reconstruction of the late miocene climate of spain using rodent palaeocommunity successions an application of end member modelling abstract end member modelling is applied to a data set of relative abundances of 67 upper miocene rodent associations 11 6 ma from spain france austria and greece the analysis results in the robust estimation of relative levels of four climatic parameters humidity temperature seasonality type and predictability in the preparatory stage species are aggregated into nine groups on the basis of ecological criteria humidity preferences and adaptations are based on actualistic and functional morphological interpretations of dentition and locomotion temperature preferences are inferred from palaeobiogeographic distributions levels of adaptation to seasonality type wet dry or cool warm seasonality are assigned on the basis of diversities in present day climate vegetation zones and the ability of extant relatives to hibernate demographic data are used to formulate adaptations to climatic un predictability in the modelling stage the compositions are unmixed into the contributions of four end members these four extreme theoretical rodent compositions are interpreted in climatic terms and their contributions to the samples are used for the estimation of climatic parameters the subset of 44 well dated rodent compositions from the calatayud daroca and teruel basins ne spain is used to construct detailed climatic curves for the late miocene while the geographical dimension in the data set is used to calculate inter basinal differences the model results for spain indicate more humid and cooler conditions between 10 5 and 8 5 ma around 7 and around 6 ma and more arid and warmer conditions before 10 5 between 8 6 and 7 5 ma and around 6 5 ma superimposed on this pattern is a shift from a more predictable cool warm seasonal climate towards a more unpredictable wet dry seasonal climate between 9 4 and 8 2 ma inter basinal comparisons per time slice show that the climate in southern europe was dryer warmer more wet dry seasonal and more unpredictable than in central europe and that the climatic and vegetational boundaries between the two regions were sharp the occurrences of more humid and cooler episodes in spain during the late miocene might be explained by southward migrations of the boundary between a temperate and subtropical dry climatic belt and their associated vegetation types various positive correlations are observed between the rodent based climatic curves for spain and other palaeoclimatic records from the mediterranean and ne atlantic region clay minerals marine fauna stable isotopes the two cooling maxima at 9 4 and 7 ma closely correspond to clusters of marine events which are generally considered to reflect maxima of global ice volume

oxygen isotopes in meteoric calcite cements as indicators of continental paleoclimate because meteoric water 18 o values decrease with decreasing ambient temperature and increasing latitude 18 o values of meteoric calcite cement should exhibit a similar relation with paleolatitude and be an indicator of continental paleotemperatures to test this we compiled isotopic and paleolatitude data for 20 meteoric cements and nine speleothems ranging in age from devonian to modern and in paleolatitude from 3 5 to 83 mean 18 o values for meteoric cements and speleothems both show the same negative correlation with paleolatitude the 18 o vs latitude trend for these carbonates is almost identical to that predicted for modern inland environments but differs from the trend for coastal environments this suggests that the ground water controlling the ultimate composition of meteoric cement is derived predominantly from inland recharge if it is assumed that the modern meteoric water 18 o vs temperature relation is valid for the past and that insignificant evaporation occurred prior to carbonate precipitation then coastal and inland paleotemperatures can be calculated from the 18 o values of meteoric calcite 18 o mcl and seawater 18 o sw by using the equations t coastal 13 3 32 6 0 231 0 0613 18 o mcl 18 o sw and t inland 17 8 16 2 0 572 0 1233 18 o mcl 18 o sw where t is temperature in c calcite precipitated from coastal meteoric water at temperatures between 0 and 25 c will exhibit a narrow range in 18 o 6 to 4 where 18 o sw 0 the 18 o of calcite precipitated from inland meteoric water will be sensitive to paleotemperature ranging from 14 to 5 where 18 o sw 0 for temperatures of 0 to 25 c

updip to downdip cementation and dolomitization patterns in a mississippian aquifer appalachians abstract staining of calcite cements dickson 1965 provides a way of mapping diagenetic events based on cathodoluminescent cements from updip areas downdip into the basin in the petroleum producing mississippian newman limestone kentucky updip the limestones contain pre compaction pink staining calcite cements with nonluminescent to dull to nonluminescent zonation that formed during two phases of aquifer recharge from the northwest during which unstable carbonate grains were leached and intergranular space was partly filled by meteoric cements these cements pass downdip into dully luminescent 1 pink 2 purple and 3 pink staining cements and finally into purple and blue staining cements in the basin these meteoric cements have depleted carbon and oxygen isotope compositions relati e to marine calcites niemann and read 1988 burial calcite cementation was preceded or synchronous with burial dolomitization from waters with isotopic compositions between those of meteoric and saline waters this was accompanied by a phase of burial leaching and chalky microporosity formation in ooid grainstones purple zone 4 and blue zone 5 calcite cements are the dominant cement type in the shaly limestones of the basin but they also post date pink cements zones 1 to 3 updip these cements are syn and post compaction burial cements that locally are associated with oil migration into the reservoirs and are pennsylvanian to triassic in age a second phase of burial leaching may have preceded zone 5 blue calcite cement which formed at maximum burial depths zone 6 purple and zone 7 pink cements are related to pos paleozoic uplift pink staining cements have less than 1 000 ppm fe purple cements have 1 000 to 3 000 ppm fe whereas blue stained cements have greater than 3 000 ppm fe mn compositions are variable fe compositions of the cements suggest that the fluids became more reducing with depth fluid inclusions in burial cements suggest na ca cl waters with salinities of 5 to 17 wt salt likely temperatures were 40 to 60 c in kentucky increasing to 125 c or more in the deeply buried fold thrust belt the 13c values of purple blue cements in the west show similar trends to meteoric calcites in that they are lightest in the recharge area becoming heavier downdip deltaic waters charged with isotopically light c penetrated deeply i to the western part of the aquifer becoming heavier downdip by rock water reaction the 18o values of the purple blue calcites become heavier in extreme basinal sections due to intense rock water interaction these basinal waters were generated by dewatering of the basinal shale section during late paleozoic tectonism they were isotopically heavy and geopressured and they precipitated burial calcites derived by pressure solution

paleoecological constraints on reef coral morphologies in the tortonian early messinian of the lorca basin se spain abstract coral reefs represent one of the main carbonate factories that contributed to the control of the stratigraphic architecture of carbonate platforms which had a widespread development during the late miocene in the paleo mediterranean area the late miocene reef complexes of the lorca basin in southeastern spain are composed of five mixed siliciclastic carbonate units middle tortonian to early messinian in age the development of coral reefs probably ceased when the first evaporitic event occurred in the basin centre in the early messinian this study mainly focuses on the response of reef communities and the modifications of reef organisation to global and regional parameters at the platform scale the carbonates are intermixed with terrigenous deposits related to two main types of clastic systems torrential fans and fluvial to deltaic systems the amount of clastic input greatly affected reef growth and coral morphologies three different types of stratal geometries were delineated in the reef complex sigmoids bioherms and patches and carpets the reef frameworks are mainly constructed by a poorly diversified assemblage of corals composed of poritids faviids and mussids porites is the principal reef builder of the sigmoids and carpets where it is widely distributed tarbellastraea is common in bioherms and acanthrastraea appears generally associated with porites in patches five basic growth forms of porites are observed thin branching or finger shaped thick branching to columnar domed to hemispheric encrusting and platy to dish differences in coral morphology are used to define a relative water depth zonation in monogeneric reefs the distribution of these growth forms was principally controlled by water depth the reef flat is dominated by small thin branching or finger shaped corals that are replaced towards the reef front by domed to hemispheric corals commonly encrusted by coralline algae downslope columnar morphologies grade into thin branching shapes the reef morphologies are variable throughout the five mixed siliciclastic carbonate units at the platform scale the first and oldest unit is dominated by bioclasts whereas units 2 3 and 5 are porites dominated sigmoid complexes unit 4 is a well developed biohermal complex mainly composed of tarbellastraea these units started to develop as early as middle tortonian and stopped as late as early messinian and show a progradational trend where the two latest units are well developed thus carbonate production changed from grain producing biota in the basal unit to framework producing biota in the overlying units consistent with evolution from a distally steepened ramp to a reef rimmed shelf at the scale of individual reef units the relative water depth zonation of the corals is controlled by ecological changes substrate nutrients synecologic relations and diversification of coral species in the transects across the carbonate platform related to the different units the coral zonation records changes in spatial distribution of corals in response to ecological stresses and changes in regional and global environments tectonic relative sea level changes and runoff

the potential of combined mg ca and δ18o measurements within the shell of the bivalve pecten maximus to estimate seawater δ18o composition the combined use of 18o and another independent palaeotemperature proxy from the same carbonate biomineral archive forms the basis of a much desired palaeosalinity proxy by circumventing the main source of uncertainty in interpreting 18o palaeorecords i e variations in the isotopic composition of seawater contrary to the 18o proxy transferring the mg ca temperature proxy to marine bivalves has proved problematic since a strong seawater temperature control on shell calcite mg ca has rarely been observed in this study a preliminary evaluation of the combined use of 18ocalcite and mg ca from pecten maximus inner shell calcite to estimate 18owater is reported new mg ca data obtained by milling the inner shell regions from p maximus specimens grown in laboratory aquaria under constant seawater temperatures between 10 and 20 c exhibit a strong relationship between mg ca and temperature mg ca 2 56 0 42 0 17 0 03 t r2 0 77 p 0 001 n 54 while the relationship between sr ca and temperature was not strong r2 0 30 p 0 001 n 54 using specimens grown in a separate aquaria validation experiment estimated mg ca derived seawater temperature was within 0 48 c of measured seawater temperature while estimated 18owater was within 0 05 to 0 15 of measured seawater 18o composition depending on the 18o temperature equation used and with uncertainty estimates of 0 63 and 0 35 such observations indicate the strongest potential to date for the development of valid temperature and 18owater salinity proxies in bivalves from the combined application of mg ca and 18ocalcite in the inner shell regions of p maximus further studies for a wide range of pectinid species ages and different natural environmental settings are needed to validate the observations of this study

ring structures made by shore ice in a muddy tidal flat st lawrence estuary canada abstract large size ring sedimentary structures occurring in a muddy tidal flat on the south shore of the st lawrence estuary are reported for the first time they range from 15 to 50 m in diameter and occur as isolated features or in groups of 3 to 5 in plan they form well defined circles scattered throughout the higher mud flat some structures are characterized by an inner ring and by a chaotic surface of alternating micro ridges and depressions the outer surrounding mud ridge is a few decimeters high and wide 25 60 cm ring structures occur at the emplacement of icefoot pustules and are related to vertical pressures exerted on the substrate by ice blocks moved up and down by tide motion icefoot pustules form every winter but not necessarily at the same location it is likely that the related ring structures can be fossilized and preserved in the sedimentary sequence consequently they can be of assistance in palaeoenvironmental interpretation

the internal external zone boundary in the eastern betic cordillera se spain reply abstract the internal external zone boundary iezb in the betic cordillera of southern spain separates the internal zone which was deformed and in part metamorphosed before the early miocene from the external zone which consists of the cover rocks of the iberian margin shortened to form a thin skinned fold and thrust belt in early to middle miocene times over much of its length the iezb is roughly linear trending approximately 070 it has been referred to as a major dextral strike slip zone and has even been considered as the northern boundary of a westward moving alboran microplate field and kinematic data from the eastern betic cordillera show that the iezb crops out over a 60 km distance as a gently dipping thrust with displacement to the southeast or south southeast oblique to its regional trend there is no evidence of dextral strike slip movement along the boundary new micropalaeontological studies of calcareous nannoplankton indicate that the oligo miocene basin along the boundary was the site of continuous deposition until the beginning of the middle miocene the thrust at the iezb cuts early miocene rocks and is overlapped by the middle miocene thrusting therefore occurred in this time interval the iezb is therefore unlikely to have been the dextral boundary of a westward moving alboran microplate at this time but was more likely to have been the locus of nw directed dextrally oblique convergence

sedimentology of an ice contact glaciomarine fan complex nastapoka hills eastern hudson bay northern quebec abstract emerged holocene coalescing glaciomarine fans are exposed along the nastapoka hills eastern hudson bay the fans form part of a regional stratified drift belt associated with terrestrial and submarine frontal moraines and other grounding lines deposits these thick extensive and in many cases coalescent sediment bodies were deposited during a stillstand of the quebec labrador sector qls of the laurentide ice sheet lis that pinned on the hills during eastward retreat from hudson bay the fans are composed of basal interbedded and interlaminated sand silt and silty clay facies association i fa i deposited by suspension settling from overflow plumes sediment gravity flows and ice rafting towards the ice contact zone fa i interfingers with diamict layers fa ii deposited by gravity flows and ice rafting these two sedimentary units are overlain by interbedded sand and gravel fa iii formed by reworking during subsequent emergence parts of fa i and fa ii were remobilized by submarine gravity flows which prevailed long after ice retreat the sedimentology of the nastapoka hills provides information on the processes operating near the grounding line of a temperate ice sheet reaching tidewater

oyster shells as recorders of short term oscillations of salinity and temperature during deposition of coral bioherms and reefs in the miocene lorca basin se spain abstract we use 18 o and 13 c of oyster shells inferred seawater 18 o w and temperature tolerance ranges of modern zooxanthellate coral communities to constrain and model paleo salinities of marginal marine waters of the miocene lorca basin spain salinities ranged from 22 to 32 psu during growth of coral bioherms and carpets of the soriana and parrilla formations and from 35 to 39 psu during deposition of the hondo formation reef complex the periods with lower modeled salinities correspond with deltaic and alluvial fan sedimentation in the area the modeling is supported by 87 sr 86 sr data and provides new insights into the evolution of the local depositional settings departures of sr isotope values from the global oceanic curve occur within the intervals with the lowest modeled salinities and the non oceanic 87 sr 86 sr preserved in individual oyster shells was probably sourced from uplifted aquitanian burdigalian limestones 87 sr 86 sr values that plot along the global ocean sr isotope curve for the late miocene indicate a tortonian age for the upper part of the soriana formation and the parrilla formation and a messinian age for the hondo formation more generally we demonstrate how the chemical analyses of oyster shells provide additional information regarding short term oscillations of salinity and temperature of seawater beyond what can be obtained by traditional paleoecological methods

sedimentary structures made by shore ice in muddy tidal flat deposits st lawrence estuary quebec abstract well preserved sedimentary structures formed by shore ice are exposed in emergent muddy tidal flat deposits along the shoreline of the st lawrence estuary the sedimentary features are exposed in high marsh micro cliffs 1 to 2 m high features from two localities where they are the most abundant sainte anne de beaupre north shore and montmagny south shore are reported here two categories are distinguished first bowl shaped circular and elongated structures 30 to 100 cm across which are former scoured depressions subsequently filled by stratified mud fine sand and organic debris and second deformations folds a few decimeters to a few meters in size produced by ice block pressure pebble to boulder size dropstones are associated with these structures most features were observed in mud flat and low marsh units facies vertically exposed at these localities the age of these tidalite deposits ranges from about 200 to 600 years these ice made structures and deformations well preserved in a sequence of recent emerged tidal sediments suggest that similar features may be preserved in older rock formations consequently they can be considered as a promising tool for interpreting the former climatic conditions in which tidalites and other shallow marine and lacustrine formations may have been deposited

controls over the chloride concentration of submarine hydrothermal vent fluids evidence from sr ca and87sr 86sr ratios abstract strontium and calcium are transported as chloride complexes in submarine hydrothermal vent waters with the sr and ca concentrations being controlled by equilibration with secondary mineral phases mainly epidote and anorthite albite the relative proportions of albite and anorthite precipitated from hydrothermal fluids are also dependent on the cl level of the fluids due to sodium metasomatism of the oceanic crust the s ca ratio of albite is higher than coexisting anorthite hence the sr ca ratios of the vent waters are also a function cl concentrations the sr isotope composition of hydrothermal fluids is determined by the mixture of seawater sr passing through the anhydrite precipitation zone and sr leached from basalt the proportion and absolute amount of seawater sr in the hydrothermal waters can be calculated from the87sr 86sr ratio of seawater local basalt and the vent fluids themselves and is also dependent on the cl concentrations of the fluids these two observations have been used to examine the factors controlling chloride concentration of submarine hydrothermal fluids the data support precipitation of a cl rich mineral phase and hydration of oceanic crust as the major processes controlling cl concentrations in intermediate cl vents such as those at 21 n east pacific rise and the tag and mark sites mid atlantic ridge the cl levels of vent fields with extreme cl concentrations juan de fuca and 11 13 n epr appear to be controlled by supercritical brine condensation followed by mixing of the brine and vapor phases

strontium isotopic paleontological method as a high resolution paleosalinity tool for lagoonal environments a combined strontium isotopic 87 sr 86 sr and paleontological method is newly applied to a modern lagoon in egypt s nile river delta to test its applicability as a paleosalinity proxy analyses of 22 surficial samples collected throughout the lagoon include 81 sr isotopic analyses of mollusks foraminifera ostracods barnacles bryozoans serpulid worm tubes pore water and gypsum crystals two salinity groups are distinguished in each sample a lower salinity group 1 ppt mixed with a higher salinity group 3 10 ppt that respectively are interpreted as the modern biocoenosis and an older relict fauna the relict fauna denotes higher salinity conditions in the lagoon prior to closure of the aswan high dam 1964 and the modern fauna records freshening of the lagoon recent decreased salinity is a response to regulated nile river flow and increased discharge into manzala of fresh water via canals and drains quantification of this short term salinity change holds promise for study of modern lagoons in other world settings and may provide paleoclimatic information for older lagoon sequences in the nile river delta and the geologic record

the oxygen and carbon isotope distribution in the mediterranean water masses abstract the oxygen and carbon stable isotope compositions of the present day mediterranean waters have been measured in order to evaluate their variability which is related to the specific climatic and hydrological conditions within the basin the experimental equation between the 18 o value and the salinity of water based on 300 measurements on surface intermediate and deep waters sampled during the vicomed 2 and 3 cruises in the western central and eastern mediterranean has a slope of 0 27 a value which is significantly lower than the slope of 0 45 as defined in the northeast atlantic ocean this difference in the 18 o salinity relationship which occurs immediately in the alboran basin is basically a characteristic of the climatic regime of the mediterranean i e of an excess evaporation over fresh water input the largest variations of these two parameters 18 o of water and 13 c of co 2 are observed in the surface waters mostly in the western mediterranean this evolution mirrors the progressive eastward restriction which separates the less evaporated and more productive western basins from the more evaporated and less productive eastern basins the intermediate waters constitute a homogeneous layer however their 18 o values decrease eastward by 0 35 at maximum due to progressive dilution by mixing with overlying and underlying water masses their 13 c values decrease also eastward by 0 35 at maximum due to an increasing input of nutrients issued from the regeneration of sinking organic particles the deep waters have similar 18 o values but slightly higher 13 c values often by less than 0 1 than the overlying intermediate waters indicating generally well ventilated conditions due to active winter convection