late pleistocene uplift history along the southwestern marmara sea determined from raised coastal deposits and global sea level variations pleistocene raised coastal deposits characterized by locally abundant shells aragonite cemented beachrock and associated nearshore deposits border the western marmara sea at elevations of 0 50 m field observations confirm that these deposits formed during a series of transgressive and regressive events u th dates in 16 in situ shells from four localities show that the peak of the transgressions occurred during the highstands of oxygen isotopic stages 7 and 5 between 53 and 210 ka the elevations of these dated deposits can be used to quantify their post depositional uplift and indicate that the entire western marmara shelf including the strait of canakkale dardanelles has been rising at an average rate of 0 40 mm yr 1 since 225 ka the primary cause of uplift is the local compression associated with a restraining bend in the western segment of the north anatolian fault paleogeographic maps constructed using the average rate of tectonic uplift and detailed topographic and bathymetric maps reveal that prior to glacial oxygen isotopic stage 8 the marmara sea was never isolated from the aegean sea even when global sea level was low because the floor of the strait of canakkale was too deep early in its uplift history the dominance of mytilus edulis in raised coastal terraces dating from the lowstand of glacial oxygen isotopic stage 8 suggests that the degree of communication between the aegean sea and marmara sea was comparable to that of the present during the peak of glacial oxygen isotopic stage 6 the floor of the strait was subaerially exposed isolating the marmara sea for the first time in the pleistocene from the higher salinity mediterranean water inflow and possibly causing it to become a blackish water lake during interglacial isotopic stages 9 7 and 5 the strait of canakkale was very wide and deep 100 125 m and there were two subsidiary channels bolayir and eceabat channels providing additional links between the aegean sea the marmara sea further promoting significant water exchange between these basins the dominance of ostrea edulis in the raised terraces dating from isotopic stages 5 and 7 confirms an enhanced penetration of the mediterranean water mass into the marmara sea the history of communication between the black sea fed by central and northern european drainage systems and the low latitude mediterranean sea is of fundamental importance in understanding the genesis of organic rich sapropel deposits throughout the region the results presented in this paper caution against the simple assumption that sea level change alone controlled the degree of connection across this oceanographic gateway instead the physiography and paleoceanography of the region were controlled both by variations in global sea level and the rate of uplift in an area of active transpression

paleobotanical evidence for near present day levels of atmospheric co2 during part of the tertiary understanding the link between the greenhouse gas carbon dioxide co 2 and earth9s temperature underpins much of paleoclimatology and our predictions of future global warming here we use the inverse relationship between leaf stomatal indices and the partial pressure of co 2 in modern ginkgo biloba and metasequoia glyptostroboides to develop a co 2 reconstruction based on fossil ginkgo and metasequoia cuticles for the middle paleocene to early eocene and middle miocene our reconstruction indicates that co 2 remained between 300 and 450 parts per million by volume for these intervals with the exception of a single high estimate near the paleocene eocene boundary these results suggest that factors in addition to co 2 are required to explain these past intervals of global warmth

cretaceous pco2 estimation from stomatal frequency analysis of gymnosperm leaves of patagonia argentina abstract stomatal frequency of fossil conifers and ginkgoals cuticles were considered as potential indicators of the p co 2 values in the patagonian palaeoatmosphere during the cretaceous samples are from continental deposits of early upper aptian age anfiteatro de tico and punta del barco formations and upper albian lower cenomanian age kachaike formation both outcropping in andean and extra andean portions of santa cruz province argentina it can be inferred that the co 2 atmospheric content was similar during both stages or was slightly higher toward the late albian early cenomanian the co 2 content estimated from the conifers is between 700 and 1400 ppmv or lower from the mid aptian ginkgoals this co 2 range is consistent with those predicted worldwide by previous studies stomatal indices biogeochemical models and carbon isotopes and implies a co 2 content 2 3 4 0 times higher than present the high atmospheric co 2 content during the middle aptian and late albian early cenomanian was probably linked to a warming process at high latitudes during these times this is consistent with the floristic development recorded during both stages in patagonia

carbon sequestration activated by a volcanic co 2 pulse during ocean anoxic event 2 ninety four million years ago during ocean anoxic event 2 there was a marked increase in the burial of organic carbon in marine sediments measurements of stomata in fossil leaves show that the two main pulses of carbon burial were associated with a decline in atmospheric co2 levels of up to 26 the cretaceous ocean anoxic event 2 about 94 million years ago is thought to be linked to extensive volcanism which triggered a biogeochemical chain of events that eventually led to widespread marine anoxia and a remarkable increase in carbon burial in marine sediments1 2 3 it has been suggested that the event was accompanied by a substantial decrease in atmospheric co2 concentrations4 but the quantification of the drawdown remains controversial5 6 here we reconstruct atmospheric co2 concentrations throughout the ocean anoxic event from counts of the stomata in fossil leaves and use terrestrial carbon isotopes to link the reconstruction to marine records of the event7 8 we find that before the onset of ocean anoxia atmospheric co2 concentrations increased by 20 over background levels of 370 100 70 ppm this was part of a long term rise in atmospheric co2 levels presumably caused by volcanism which reached a peak of 500 400 180 ppm however two pulses of extensive carbon burial during the ocean anoxic event as indicated by positive carbon isotope excursions are associated with decreased atmospheric co2 concentrations we conclude that the sequestration of marine organic carbon led to a decrease in atmospheric co2 concentration of up to 26 during ocean anoxic event 2

atmospheric pco2 since 60 ma from records of seawater ph calcium and primary carbonate mineralogy a 60 m y record of atmospheric p co2 has been refined from knowledge of 1 secular changes in the major ion composition of seawater particularly ca and mg and 2 oscillations in the mineralogy of primary oceanic carbonate sediments both factors have had a significant impact on the chemistry of the ocean carbonate buffer system calculated atmospheric p co2 oscillated between values of 100 300 ppm and to maxima of 1200 2500 ppm from 60 to 40 ma and varied between 100 and 300 ppm from 25 ma to the present the refined p co2 values are significantly lower than previous estimates made from seawater ph data where total dissolved inorganic carbon was assumed constant and more in line with modeling and stomatal index estimations of atmospheric p co2 for the tertiary

plant community ecology and climate on an upland volcanic landscape during the early eocene climatic optimum mcabee fossil beds british columbia canada abstract the mcabee fossil beds in south central british columbia canada provide a record of forest ecosystems within a volcanically active upland landscape during the early eocene climatic optimum eeco to assess plant community ecology and climate within this environment palynology and census style macrofossil collections were investigated from two shale horizons separated in time by likely 103 104 years an ensemble of leaf physiognomic estimates indicates a persistent warm mean annual temperature mat 10 12 c and mesic mean annual precipitation 1000 mm yr 1 climate between the horizons the plant community was similar in both horizons comprising angiosperms e g ulmus fagus alnus betula and carya and gymnosperms e g metasequoia pinus picea and larix plant diversity and the distribution of dicot leaf mass per area ma values were consistent between the two horizons despite intervals of varying tuff thickness and frequency between the horizons differences in macrofossil abundances of ulmus fagus and pinus and a lack of such differences in their respective pollen abundances might be explained by local patch dynamics influenced by spatial heterogeneity resulting from topographic diversity and disturbance ma estimates suggest dicots were predominately deciduous and the distribution of ma is similar to a modern forest in panama influenced by seasonal precipitation the diversity of dicots at mcabee despite relatively lower mean annual temperatures is comparable to fossil plant quarries of similar volume from early eocene sites in patagonia e g laguna del hunco and the denver basin with relatively warmer mats 17 25 c this is best explained by a combination of predominately frost free winters high productivity and an abiotic environment characterized by spatial heterogeneity and high rates of change the sampled paleofloras of this study showcase an eeco plant community likely representing an ecological solution to volcanic disturbance over millennial time scales

estimating paleoatmospheric pco2 during the early eocene climatic optimum from stomatal frequency of ginkgo okanagan highlands british columbia canada abstract estimates of p co 2 for the early paleogene vary widely from near modern day levels to an order of magnitude greater based on various proxy measures resolving the relationship between climate and p co 2 during this globally warm period is a key task in understanding climate dynamics in a warmer world here we use the stomatal frequency of fossil ginkgo adiantoides from the okanagan highlands of british columbia canada to estimate p co 2 during the early eocene climatic optimum eeco the interval of peak warmth in the cenozoic we also examine a dataset of modern ginkgo biloba leaves to critically assess the accuracy and precision of stomatal frequency as a proxy indicator of p co 2 early eocene fossil g adiantoides has significantly lower stomatal frequency than modern g biloba suggesting p co 2 levels 2 modern pre industrial values this result is in contrast to earlier studies using stomatal frequency of ginkgo that indicated near modern day levels of p co 2 in the early paleogene though not including samples from the eeco we also find that levels of p co 2 as indicated by stomatal frequency are correlated with trends in climate mean annual temperature over time at the falkland fossil locality suggesting that climate and p co 2 were coupled during the eeco hyperthermal

the silicate weathering feedback in the context of ophiolite emplacement insights from an inverse model of global weathering proxies silicate weathering provides a stabilizing feedback in the global carbon cycle and has played a key role in keeping surface environments clement for the majority of earth9s history it was recently proposed that ophiolite emplacement at low latitude at 90 to 70 ma and 50 to 40 ma enhanced the rate of silicate weathering and led to global cooling that terminated the early eocene climatic optimum in this study we revisit this proposal with a series of models of varying complexities to investigate the likelihood that earth9s climate was driven largely by ophiolite emplacement in the paleogene our models are constrained by either marine os isotopic records or the combination of carbon cycle sr and os isotopic records and solid earth degassing rates the proposed changes in ophiolite weathering are inconsistent with our os isotope mass balance model with our coupled carbon cycle and weathering proxy model total global silicate weathering fluxes including ophiolite weathering slightly decreased or remained relatively constant from 52 to 42 ma this constancy in global silicate weathering fluxes is inconsistent with the idea that enhanced ophiolite weathering directly led to global climate cooling however our model results support the idea that the strength of the silicate weathering feedback weatherability has played a significant role in regulating the pco2 levels through the cenozoic further the modeling toolkit developed here can be used to explore the role of mafic rock weathering in driving climate change in other intervals through earth9s history

carbon dioxide and the early eocene climate of western north america we present results from an early eocene ca 50 56 ma ago regional modeling sensitivity experiment that examines the role of atmospheric co 2 in determining the regional climate of western north america this is the first paleoclimate modeling study to investigate the possible role of increased co 2 in influencing the early eocene climate on a regional scale we take a regional modeling approach with the goal of using higher spatial resolution to elucidate the role of specific climate forcing mechanisms here co 2 upon a region with relatively dense paleoclimate proxy data coverage the spatial resolution of global climate models does not permit the close comparison of model results to proxy climate data in a way that helps to distinguish between regional and global climate forcings which is a goal of this study while our results suggest that co 2 was most likely at least as high as 2240 ppm this high concentration does not yield a regional climate that matches regional proxy data in all aspects therefore in combination with high atmospheric co 2 other forcing factors must have played significant roles in defining the nature of early eocene climate

formation of beach rock at siesta key florida and its influence on barrier island development seaward dipping strata of carbonate cemented shell debris located along the coast of siesta key on the gulf coast of the florida peninsula have long been interpreted to be beachrock equivalent in age to the pleistocene anastasia formation stage 5e of the east coast of florida detailed examination of thin sections along with radiometric dating and isotopic analyses demonstrates clearly that this is a holocene deposit that is not beachrock but was lithified in a meteoric environment whole rock dates dates from shells only and from cement only demonstrate that these beach deposits were in place by at least 1800 yr bp and might have been there as long ago as 4300 yr bp this means that some type of barrier island was in place at that time previous investigations have depicted siesta key as having a maximum age of 3000 yr with these deposits being located about 2 km landward of the beach deposits this suggests that the beach deposits might have been the site of the original position of siesta key these data also indicate that sea level must have been near its present position at the time that these foreshore beach deposits were deposited sometime between 1800 and 4300 yr ago this scenario indicates that sea level along this coastal reach probably reached its present level at least about 2000 yr ago

beach cement incipient caco 3 cemented beachrock development in the upper intertidal zone north uist scotland abstract beachrock has only rarely been observed previously along high latitude coasts on several beaches on north uist nw scotland at over 57 n there is evidence of small scale beach cementation an area of beach cement at the back of traigh ear as well as unconsolidated sands from the beach and the adjacent traigh hornais have been studied using sem xrd and petrographical thin sections to throw light on the nature and causes of cementation unconsolidated sands from both beaches are similar in grain sizes shape and mineralogy but traigh ear grains commonly possess abundant cover of high mg calcite the beach cement on traigh ear exhibits low porosity with abundant micritic and aragonitic cements showing no evidence of vadose cementation along with traces of microorganisms these findings contrast with the vadose low mg calcite cements commonly reported from temperate zone beachrocks

depositional setting fossil flora and paleoenvironment of the early eocene falkland site okanagan highlands british columbia the fossil flora and depositional setting of the early eocene falkland site in the southern interior of british columbia canada is reported in detail for the first time using a census sampling approach the falkland site is part of the series of okanagan highlands fossil localities in british columbia and washington state that represent relatively cool upland environments within the context of the greenhouse world of the early eocene providing microthermal mean annual temperature mat 13 c climatic conditions for the establishment of cool adapted plants geographically adjacent to subtropical elements from lowland floras plant community composition of the falkland flora is most similar to the republic washington and mcabee british columbia floras based on high sorenson similarity coefficients together forming a southern cluster of okanagan highlands sites the site is a lacustrine deposit that formed in a volcanically active landscape paleoclimate reconstructions based on leaf physiognomy

reconstruction of atmospheric co2 during the early middle eocene by application of a gas exchange model to fossil plants from the messel formation germany abstract in this study atmospheric co 2 during the early middle eocene 47 ma is reconstructed using fossil plants from the messel formation close to darmstadt germany co 2 concentration is calculated using a mechanistic model of gas exchange which optimizes co 2 uptake by photosynthesis against water vapor loss by transpiration a strategy that is commonly realized in land plants input data for the model are stomatal data density and pore length paleoclimate data obtained by two different approaches and biochemical parameters of photosynthesis leaves from three taxa belonging to two different families were studied laurophyllum lanigeroides daphnogene crebrigranosa both lauraceae and rhodomyrtophyllum sinuatum myrtaceae the results suggest that co 2 was between 853 and 1033 ppm during the development of the messel formation stomatal data therefore indicate a co 2 concentration that was substantially higher than today the reconstructed range of co 2 concentration is close to data provided by geochemical modeling results and conforms to various data that indicate a warm and ice free climate during this time interval

beachrock cementation in alexandria egypt beachrock is found in the intertidal and sublittoral zones along the mediterranean coast of alexandria egypt it occurs as beds or patches and shows several stages of cementation and hardness the seaward dip of the beachrock is similar to that of the slope of the foreshore the fabric shows micrite and fringe cement types aragonite was not identified in the beachrock at alexandria the average concentrations of ca mg sr fe and mn in the beachrock are similar to those of the beach deposits the process of beachrock cementation in alexandria is rather recent and typically marine

quantitative uncertainty analyses of ancient atmospheric co2 estimates from fossil leaves the relationship between atmospheric co 2 and ancient climate is of fundamental importance for gauging the climate sensitivity of the earth system to a changing co 2 regime one of the most widely adopted paleobiological co 2 proxies for reconstructing earth s atmospheric co 2 history exploits the inverse relationship between leaf stomatal index the fraction of leaf epidermal cells that are stomatal structures and atmospheric co 2 however fossil leaf based co 2 reconstructions make a prioii assumptions about the form of the empirical relationship between si and co 2 required for transfer functions and have failed to correctly propagate error terms these effects can translate into erroneous interpretations that undermine the value of the proxy here we report the development and application of a rigorous generalized statistical framework overcoming these limitations that generates probability density functions for each atmospheric co 2 estimate the utility of our statistical tools is demonstrated by showing how they revise earlier atmospheric co 2 estimates from fossil cuticles of ginkgo and metasequoia trees during the early eocene and middle miocene warm periods upwards by 150 to 250 ppm to 450 to 700 ppm the revised co 2 reconstructions therefore help to resolve the paradox of warm paleogene and neogene greenhouse climates co existing with near present day levels of co 2 and support the emerging view from independent paleoclimate studies for a high climate sensitivity of the earth system the statistical tools presented are sufficiently versatile to permit their use in other investigations of paleoco 2 estimates from fossil leaves

formation of holocene limestone sequences by progradation cementation and erosion two examples from the bahamas abstract holocene limestones on north bimini and joulter cays bahamas reveal sedimentary structures that are directly comparable to structures in the modern beach environment a complete sequence comprises shallow subtidal intertidal and supratidal deposits holocene and equivalent modern sedimentary features are found on more or less the same topographic levels freshwater cementation phreatic and vadose takes place after accretion and progradation of the shore subsequent erosion exposes the consolidated sediments secondary cementation in the intertidal zone leads to beachrock formation continued erosion may break off blocks of beachrock and cliffs which will be incorporated into the basal part of the sequence during a new phase of progradation a freshwater cemented sequence going from shallow subtidal to supratidal and eolian deposits does not therefore necessarily imply sea level changes but can be created by a cycle of progradation cementation and erosion

magnesian calcite cements and their diagenesis dissolution and dolomitization mururoa atoll the most ubiquitous syn sedimentary cements affecting mururoa atoll are composed of magnesian calcite three main types are distinguished fibrous bladed and sparitic on the basis of petrography morphology and mgco3 concentration of the constituting crystals while peloid infills a particular form of hmc chemical precipitation also exist petrographic evidence and isotopic signatures are compatible with marine precipitation mururoa atoll was exposed several times to meteoric diagenesis resulting in varied diagenetic alterations including selective dissolution and partial dolomitization of mg calcite cements these alterations are responsible for substantial modifications of the initial cement fabrics and may introduce unconformities in the diagenetic chronology the first stage of the partial dissolution of mg calcite induces the development of chalky white friable zones within the initially crystalline hard cement layers at ultrascale this is due to the creation of micro voids along the elongate cement fibres advanced dissolution includes total disappearance of cement portions as attested to by large voids within the cement crust and or between superposed cement layers mg calcite dissolution is related to meteoric diagenesis during periods of quaternary exposure the creation of voids within mg calcite layers is due to the mechanical removal of previously altered calcium carbonate a process suggesting marine or non marine water flow probably in the vadose environment selective dolomitization of mururoa cements involves alternations of calcite and dolomite which form successive cement like rinds within primary cavities at mururoa these alternations are the result of selective dolomitization of the pre existing mg calcite cements rather than successive precipitation of calcite and dolomite selective dolomitization of mg calcite cements at mururoa indicates that a given cement succession is not necessarily a simple chronological sequence oxygen isotope values of dolomites are enriched in 186 by about 3 pdb within calcite dolomite pseudo alternations the dolomitizing fluid at mururoa seems similar to present marine water although some mixture with meteoric water is probable to favour dissolution associated with dolomitization

diagenesis of quaternary bahamian beachrock petrographic and isotopic evidence abstract carbonate beachrock is a common feature on many beaches of san salvador island bahamas these well indurated slabs of cemented beach sand are jointed normal and parallel to the shoreline and slope gently seaward constituent sediment grains are identical to those of adjacent unlithified beach sands beachrock exposed along the northern western and southern coastline of the island is commonly characterized by aragonite needle cement micritized grains and micritic envelopes which are features of early marine phreatic diagenesis these beachrocks have whole rock 13c values of 4 75 pdb and 18o values of 0 75 pdb which are identical to carbon and oxygen isotopic compositions of isolated aragonite needle cement and unlithified beach sand inclusion of recent artifacts in the rock indicates that these deposits are holocene beachrock from one locality on the western side of the island is covered with a calcrete crust indicating prolonged subaerial exposure and vadose weathering associated with the formation of organic rich soils petrographic features include low mg calcite cement evidence of neomorphism of aragonitic cement and micritic rims to low mg calcite random needle fiber calcite calcified filaments and micritic networks whole rock 13c values of these beachrocks range from 3 66 to 6 85 and 18o from 2 16 to 3 68 the wide range of 13c values in these samples is probably a function of the relative proportions of meteoric vadose to meteoric and or marine phreatic cements in individual samples isolated meteoric phreatic cements are only slightly enriched in the light isotopes relative to marine cements whereas meteoric vadose cements are significantly lighter the diagenetic features suggest the beachrock passed through marine phreatic to meteoric phreatic and meteoric vadose diagenetic environments this diagenetic sequence commonly forms in response to sea level lowering evidence of deposition in a shoreline environment and prolonged residence in meteoric phreatic and meteoric vadose environments suggests that these beachrocks may be late pleistocene

coastal forms and quaternary processes along the arid pilbara coast of northwestern australia abstract the pilbara coast is set in the most arid part of coastal australia this coast and coastal plain composed of riverine plains deltas tidal flats coastal dunes and limestone barriers relic deltas and archipelago ria shores is predominantly a terrigenous and carbonate sediment complex the coastal landforms therein formed during the quaternary through influence of ancestral landforms and fluvial and shoreline accretion coastal erosion and cementation the pre holocene features controlled development of holocene coastal forms and a variety of holocene depositional styles climate also plays a significant part in the coastal processes and in the generation of sedimentary products through high evaporation rates coupled with the limited rainfall cyclonic storms wind wind waves and the limited sediment delivery to the coastal zone this results in a distinctive range of stratigraphic sequences and chemical products as a result this arid coast is characterised by a range of features such as construction of arid zone deltas delta destruction and sediment redistribution during times of sediment depletion cyclone induced erosion and sedimentation mangroves and their associated sedimentary deposits evolution of coastal groundwater hypersalinity formation of salt flats and precipitation and cementation to form beachrocks high tidal crusts and gypsum precipitates the pilbara coastal stratigraphy and geomorphology suggests aridity was intricately involved in the sedimentation geomorphic evolution and pedogenic and diagenetic alteration of this coastal zone throughout the whole of the holocene and pleistocene

fossil biotas from the okanagan highlands southern british columbia and northeastern washington state climates and ecosystems across an eocene landscape the late early to early middle eocene okanagan highlands fossil sites spanning 1000 km north south northeastern washington state southern british columbia provide an opportunity to reconstruct biotic communities across a broad upland landscape during the warmest part of the cenozoic plant taxa from these fossil sites are characteristic of the modern eastern north american deciduous forest zone principally the mixed mesophytic forest but also include extinct taxa taxa known only from eastern asian mesothermal forests and a small number of taxa restricted to the present day north american west coast coniferous biome in this preliminary report paleoclimates and forest types are reconstructed using collections from republic in washington state usa and princeton quilchena falkland mcabee hat creek horsefly and driftwood canyon in british columbia canada both leaf margin analysis lma and quantitative bioclimatic analysis of identified nearest living relatives of megaflora indicated uppe

co2 forced climate thresholds during the phanerozoic abstract the correspondence between atmospheric co2 concentrations and globally averaged surface temperatures in the recent past suggests that this coupling may be of great antiquity here i compare 490 published proxy records of co2 spanning the ordovician to neogene with records of global cool events to evaluate the strength of co2 temperature coupling over the phanerozoic last 542 my for periods with sufficient co2 coverage all cool events are associated with co2 levels below 1000 ppm a co2 threshold of below 500 ppm is suggested for the initiation of widespread continental glaciations although this threshold was likely higher during the paleozoic due to a lower solar luminosity at that time also based on data from the jurassic and cretaceous a co2 threshold of below 1000 ppm is proposed for the initiation of cool non glacial conditions a pervasive tight correlation between co2 and temperature is found both at coarse 10 my timescales and fine resolutions up to the temporal limits of the data set million year timescales indicating that co2 operating in combination with many other factors such as solar luminosity and paleogeography has imparted strong control over global temperatures for much of the phanerozoic

paleoclimate and precipitation seasonality of the early eocene mcabee megaflora kamloops group british columbia early eocene fossil floras from british columbia are a rich resource for reconstructing western north american early cenozoic climate the best known of these floras reflect cooler mat 15 c upland forest communities in contrast to coeval mat 18 c forests in lowland western north american sites of particular interest is whether early eocene climates were monsoonal highly seasonal precipitation the mcabee site is a 52 9 0 83 ma 0 5 km outcrop of bedded lacustrine shale interbedded with volcanic ash in this report two historical megaflora collections that were collected independently from different stratigraphic levels and or laterally separated by 100 200 m in the 1980s university of saskatchewan and 2000s brandon university are investigated to i assess whether they represent the same leaf population ii assess whether a combined collection yields more precise climate estimates and iii reconstruct paleoclimate to assess the character of regional early eocene precipitation seas

observation of undertow and turbulence in a laboratory surf zone abstract undertow and turbulence in the surf zone have been studied in a wave flume for a spilling breaker and a plunging breaker fluid velocities across a 1 on 35 sloped false bottom were measured using a fiber optic laser doppler anemometer and wave decay and set up were measured using a capacitance wave gage the characteristics of mean flow and turbulence in spilling versus plunging breakers were studied the mean flow is the organized wave induced flow defined as the phase average of the instantaneous velocity while the turbulence is taken as the deviations from the phase average it was found that under the plunging breaker turbulence levels are much higher and vertical variations of undertow and turbulence intensity are much smaller in comparison with the spilling breaker it was also found that turbulent kinetic energy is transported seaward under the spilling breaker and landward under the plunging breaker by the mean flow the study indicates that there are fundamental differences in the dynamics of turbulence between spilling and plunging breakers which can be related to the processes of wave breaking and turbulence production it is suggested that the types of beach profile produced by storm and swell waves may be the results of different relationships between mean flow and turbulence in these waves

correlation between isotope records in marine and continental carbon reservoirs near the palaeocene eocene boundary changes in the isotope content of the large marine carbon reservoir can force shifts in that of the smaller carbon pools in the atmosphere and on land the carbon isotope compositions of marine carbonate sediments from the late palaeocene vary considerably exhibiting a sudden decrease close to the palaeocene eocene boundary which coincides with deep sea benthic extinctions1 and with changes in ocean circulation here we report that these fluctuations in the marine carbon isotope record are closely tracked by the terrestrial records provided by palaeosol carbonates and mammalian tooth enamel in using palaeosol carbonates to reconstruct the co2 content of the ancient atmosphere2 isotope shifts of this sort will have to be taken into account the sharp decrease in 13c 12c ratios in the late palaeocene provides a datum for precise correlation of marine and continental records and suggests that abrupt climate warming at this time may have played an important role in the evolution of land mammals

carbonate cement fabrics displayed a traverse across the margin of the bahamas platform near lee stocking island in the exuma cays abstract consolidated to friable carbonate rocks found in the lee stocking island area in the exuma cays include 1 reef rock 2 channel stromatolites 3 shallow water hardgrounds 4 beachrock rimming the islands and 5 pleistocene bedrock the most common cement fabrics observed are aragonitic fibers which include acicular fan druse and square tipped coarse fibers cementing beachrock and stromatolites and an isopachous needle fiber rim cementing hardgrounds and stromatolites less common are high mg calcite bladed textures of the reef rock and stromatolites two types of blades are present the more common stubby variety of either high mg or low mg calcite and an elongated variety of high mg calcite which was found in only three beachrock samples aragonitic micrite envelopes usually surround grains in beachrock hardgrounds and stromatolites but only in association with fibrous cement an aragonitic crust cements the surfaces of lime mud beds of the tidal channel while a high mg calcite cryptocrystalline cement occurs in all the rock types calcified algal filaments of high mg calcite from the abundant green and blue green algae in the area are a primary cement in stromatolites and a secondary cement in hardgrounds and beachrock a low mg calcite equant spar cements the pleistocene samples and is associated with meteoric diagenesis and cementation of the pleistocene surface cement precipitation coincides with the path of the cool oceanic water from exuma sound as it warms and loses co 2 and moves up onto the bank near lee stocking with the incoming tide cryptocrystalline cement is the first and commonest cement forming to the seaward while platformward fibrous cements become predominant as suggested by their crystal size and location on the shelf margin we think that the reef rock cryptocrystalline material are the fastest forming of the cements where the incoming oceanic water is more saturated with respect to calcium carbonate and undergoes the most significant warming the rate of the warming and degassing process is thought to increase in the tidal channel though the cementation rate is thought to fall slightly in response to a reduced availability of calcium carbonate on the platform interior further warming and degassing are believed to cause cement precipitation and the development of hardgrounds but these may form at a slower rate than that of the margin though this rate is still quite high cementation gradients occur from the tidal channel to the intertidal zones of 1 west norman s pond cay where cement fabric suggests a reduced calcium carbonate availability and 2 west lee stocking island where a change in mineralogy suggests a change in water chemistry thus a sequence of cement fabrics and mineralogies can be traced micritic textures occur in a more seaward position fine fibrous aragonite fibers in a more lagoonal and levee position and coarser aragonite fibers and mg calcite cements in the intertidal and supratidal position this sequence is thought to track the evolution of the water mass

a calibration of the bagnold beach equation abstract a simple sand trap is used to measure swash and backwash bedload transport rates on intertidal profiles data from sixty eight beach experiments are used to calculate a mean value of 12 78 kg m 4 s 2 for the calibration coefficient in the bagnold beach equation

beachrocks from the island of la palma canary islands spain beachrocks on la palma island developed on platform forming lavas of the cumbre vieja volcano some of these lavas are related to the 1585 puerto naos 1677 and 1971 echentive eruptions radiocarbon dating of the charco verde beachrock gives a conventional age of 33 330 8 490 bp while that at playa chica beach gives a calibrated age of 14 940 8 525 bp the beachrocks up to 1 5 m thick and some tens of metres wide consist of several decimetre thick horizons dipping 2 15 seaward petrographically they can be classified as rudstones and arenites with volcanic clasts as their main component the original porosity of the beachrocks was intergranular and occasionally intragranular and was partially occluded by cementation and locally by internal sediments the main cements are fibrous aragonite and micrite high magnesium calcite hmc spar aragonite peloidal hmc and microbotryoidal hmc are scarce the elemental geochemistry of these cements is consistent with a marine origin whereas the isotopic geochemistry indicates precipitation from marine waters slightly modified by meteoric waters the evolution of beach deposits and especially the beachrocks in la palma island follows three stages 1 beach deposition 2 beachrock formation and 3 beach retrogradation and or erosion the studied beachrocks prompt us to make some important considerations 1 the mean tidal range in the canary islands has not varied over the last thousand years 2 the position of the beachrocks at the present day sea level would require a combination of eustatic and isostatic movements to keep the sea level stable at the present level over the last thousand years 3 volcanic activity supplies the sediment that forms the beaches 4 a dry warm climate with a very low rainfall below 250 mm year and a high insolation rate 6 11 h day favours and favoured cement precipitation and beachrock formation by increasing the water temperature in the intertidal zone and in the inner part of the beaches 5 the presence of beachrocks in the la palma beaches prevents the total disappearance of the beaches 2003 elsevier science b v all rights reserved

beachrock occurrence characteristics formation mechanisms and impacts beachrocks are hard coastal sedimentary formations consisting of various beach sediments lithified through the precipitation of carbonate cements the objectives of this contribution are to a collate and review information on the reported occurrences characteristics and formation mechanisms of beachrocks and b consider their impacts on the coastal zone the analysis of the available information has shown that a beachrock formation is a global and diachronic phenomenon and b the great majority of beachrocks are found in tropical subtropical and low temperate latitude microtidal coasts the cementing agents of beachrocks are composed predominantly of the metastable carbonate phases high magnesian calcite hmc and aragonite ar appearing in a diverse crystalline morphology it has been suggested that cement precipitation in the coastal environment is controlled by i the physicochemical conditions ii the presence of organic compounds and microbes iii the magnitude and distribution of the wave energy along the coast and iv the textural characteristics of the constituent sediments various theories have been proposed to explain beachrock formation itself linking the phenomenon to either physicochemical or biological processes these theories however do not seem to be of universal validity and acceptance as each is able to explain only some of the reported occurrences the presence of beachrocks appears to affect beach morphodynamics by i locking the beach profile ii modifying the nearshore hydrodynamics iii changing the porous character of the beach and thus its response to wave forcing and iv differential bed erosion at the margins of the beachrock outcrops that can alter significantly the long and particularly the cross shore sediment transport therefore although relict submerged beachrock outcrops may provide some coastal protection by reducing the wave energy impinging onto the coastline modern beachrocks may promote offshore loss of unconsolidated beach sediments and buried beachrock outcropping finally the presence of beachrocks may have also significant ecological impacts as the indigenous mobile substrate fauna and flora of the beach is replaced by hard substrate benthic assemblages which are commonly arranged in hydrodynamically controlled zones

early eocene carbon isotope excursions and landscape destabilization at eccentricity minima green river formation of wyoming repeated global reorganizations of carbon cycling and biotic oceanic and terrestrial processes occurred during the early eocene and appear to have been paced by cyclic variations in the eccentricity of the earth s orbit the phase relationship s between insolation variation terrestrial paleoclimate and atmospheric pco2 during these events remains enigmatic however due to their poorly constrained timing relative to specific orbital configurations here we use tiered interpolation between radioisotopic ages and paleomagnetic polarity chrons to compare high resolution 13c and lithofacies records from the wilkins peak member of the green river formation of western north america to a fe intensity xrf record from the western atlantic ocean and to numerical solutions for earth s orbital configuration wilkins peak member lithofacies stacking patterns record cyclic geomorphic responses to insolation and climate fluctuations spanning an interval of 1 8 ma previous macrostratigraphic analyses using 40ar 39ar and u pb ash bed ages indicate that these cycles reflect long and short eccentricity modulation of precession hydrologic variance appears to have occurred inversely with intervals of maximum sediment advection with carbonate and evaporite dominated lacustrine modes during eccentricity maxima and siliciclastic dominated alluvial modes during eccentricity minima stable carbon isotope analyses of 126 meters of wilkins peak member strata reveal a regular 5 per mil oscillation between high 13c lacustrine modes and low 13c alluvial modes tiered interpolation between paleomagnetically characterized terrestrial ash beds facilitates the integration of 11 radioisotopic ages with the geomagnetic polarity timescale resulting in significant expansion of chron c23 and shortening of chron c22 relative to timescales based on seafloor magnetic anomaly profiles the new proposed timescale permits direct comparison of terrestrial and marine climate proxy records from the early eocene climatic optimum at ca 250 kyr 250 kyr resolution and reveals prominent 100 kyr and 405 kyr scale oscillations within both records wilkins peak member 13c minima which occurred during low eccentricity alluvial modes likely coincided with global 13c minima scenario 1 but may alternatively reflect productivity driven local effects within lake gosiute scenario 2 if scenario 1 proves accurate early eocene negative 13c hyperthermal excursions occurred during eccentricity minima rather than maxima as formerly believed

calcification of cyanobacterial mats in solar lake sinai pore water samples were obtained from the shallow water part of solar lake sinai where luxurious cyanobacterial mats grow these samples were analyzed for ca sup 2 mg sup 2 sr sup 2 cl sup so sub 4 sup 2 and titration alkalinity ta to determine the role of cyanobacterial growth and degradation on the calcification of the mats the data are modeled thermodynamically to predict mineral pore water equilibria the data support earlier bacterial and sedimentological studies suggesting that the degradation of the cyanobacterial mat via sulfate reduction is of major importance in the calcification process 34 references 1 figure 2 tables

formation exposure and evolution of a high latitude beachrock in the intertidal zone of the corrubedo complex ria de arousa galicia nw spain abstract the presence of beachrocks is noted on the galician shoreline at 41 n a latitude at which this phenomenon is rarely found the present study focuses on the petrological characterization and sedimentological evolution of a beachrock that was exhumed during an exceptional storm in the winter of 2001 in the intertidal zone of a high energy beach the cemented material comprises medium to coarse mixed siliciclastic carbonate sands unlike tropical beachrocks the cement consists of epitaxial low mg calcite presenting varied morphologies and textures acicular and bladed coatings and pore linings pore fillings of sparitic calcite and meniscus style cements seawater dominantly wave action plus marine and meteoric mixed waters are invoked as the main generative fluids beachrock formation and evolution are approached from a morphodynamic viewpoint considering four progressive stages 1 initial cementation in the intertidal zone 2 exposure and modelling by wave action 3 colonization and hardening and 4 disintegration preservation and burial finally the morphodynamic significance climatic implications and occurrence of this type of cementation along the north and northwest shoreline of spain are discussed

coupled co2 climate response during the early eocene climatic optimum abstract the early eocene climatic optimum eeco has been characterized as a prolonged warm event indicated by increased atmospheric pco 2 temperatures precipitation and biological turnover a new paleoenvironmental reconstruction using integrated pedological geochemical and isotopic data from the green river basin green river great divide region provides a high resolution record of environmental and climatic change throughout the eeco our reconstruction indicates that this region and likely much of the margin of paleolake gosiute was a stable fluvially controlled floodplain environment with evidence of large scale continuous soil development and features comparable with modern alfisols temperate forest soils regional climate data from multiple proxies indicates that the period was warm temperate and semi arid to sub humid with a peak interval from about 51 5 50 9 ma that exhibits significantly warmer 7 c and wetter 750 mm yr 1 conditions resulting in major changes to the local weathering regime isotopic analyses also indicate a rapid increase to high atmospheric pco 2 values 1700 ppmv and a shift in the 13 c composition of pedogenic carbonates during this peak interval that appear to define and provide a cause for this significant regional response to global climatic change the new data when combined with foraminiferal 13 c records are consistent with co 2 ventilation from a deep marine reservoir source this multi proxy reconstruction suggests that the eeco may have had a superimposed peak of climatic and ecological change on land

contrasting diagenesis of two carboniferous oolites from south wales a tale of climatic influence two oolites in the dinantian mississippian lower carboniferous of glamorgan sw britain were deposited in similar depositional environments but have contrasting diagenetic histories the brofiscin and gully oolites occur in the upper parts of shallowing upward sequences formed through strandplain progradation and sand shoal and barrier growth upon a southward dipping carbonate ramp the brofiscin oolite is characterized by a first generation cement of equant calcite spar preferentially located at grain contacts and forming non isopachous fringes around grains interpreted as meteoric vadose and phreatic in origin isopachous fibrous calcite fringes of marine origin are rather rare and occur only at a few horizons burial compaction was not important and porosity was occluded by poikilotopic calcite spar fitted grain grain contacts locally occur and could be the result of near surface vadose dissolution compaction syntaxial overgrowths on echinoderm debris are common pre compaction overgrowths are cloudy inclusion rich and probably of meteoric origin and post compaction overgrowths are inclusion free by contrast the gully oolite has little first generation cement however marine fibrous calcite is common in oolitic intraclasts as isopachous fringes of acicular calcite crystals closely associated with peloidal internal sediment and early equant drusy calcite spar occurs in the uppermost part of the gully beneath a prominent palaeokarst where pedogenic cements also occur the major feature of gully diagenesis is burial compaction resulting in extensive grain grain dissolution and microstylolitic grain contacts and post compaction poikilotopic spar occluded remaining porosity the brofiscin oolite is pervasively dolomitized up dip but the gully oolite for the most part only contains scattered pre compaction dolomite rhombs and late veins of baroque dolomite with less pervasive dolomitization the difference in diagenetic style of the two dinantian oolites is attributed to prevailing climate the paucity of early meteoric cements in the gully is a result of an arid climate and this is supported by the nature of the capping palaeokarst the abundant meteoric cements in the brofiscin reflect a more humid climate and effective meteoric recharge also resulted in up dip pervasive mixing zone dolomitization the style of early diagenesis in these two oolites exerted a major control on the later burial diagenesis in the brofiscin the early cements inhibited grain grain dissolution and pressure solution while these processes operated extensively in the gully oolite thus prevailing climate can influence a limestone s diagenetic history from near surface through into deep burial

oxygen isotopic study of late mesozoic cooling of the mount barcroft area central white mountains eastern california the middle jurassic barcroft mafic granodiorite and late cretaceous ternary minimum mcafee creek granite are important components of the igneous arc sited along the sw north american margin bulk rock analyses of 11 samples of the metaluminous i type barcroft comagmatic suite have an average 18o value of 7 4 0 6 all values 1 four barcroft specimens average end 3 6 1 8 87sr 86sr 0 707 0 001 the pluton consists of petrochemically gradational ca amphibole rich gabbro diorite granodiorite metadiorite and rare alaskite aplite for most of the pluton oxygen isotope exchange of quartz feldspar s biotite and ca amphibole accompanied local deuteric alteration eight specimens of slightly peraluminous granitic rocks of the muscovite bearing mcafee creek series have an average 18o of 8 6 0 5 four mcafee type samples average end 7 8 1 7 87sr 86sr 0 711 0 004 for both plutons bulk rock evidence of exchange with near surface water is lacking suggesting 5 10 km cooling depths barcroft minerals exhibit regular oxygen isotopic partitioning from high to low 18o in the sequence quartz plagioclase k feldspar amphibole biotite along the se margin of the pluton quartz and biotite in lower cambrian quartzites are higher in 18o and show slightly larger fractionations than igneous analogues exchange with fluids derived from these heated contact metamorphosed country rocks increased bulk 18o 16o ratios of barcroft border rocks and constituent plagioclase subsolidus tremolite actinolite especially of granitic dikes transecting the wall rocks oxygen isotope thermometry for seven barcroft pluton quartz amphibole and six quartz biotite pairs indicate apparent subsolidus temperatures averaging 519 49 c quartz plagioclase pairs from two barcroft granodiorites yield values of 519 and 515 c a quartz biotite pair from a quartzite adjacent to the barcroft pluton yields an apparent temperature of 511 c in agreement with estimates based on contact metamorphic parageneses except for its se margin barcroft pluton silicates evidently exchanged oxygen isotopes under local deuteric conditions compatible with ca amphibole thermobarometric analyses areal distributions for quartz plagioclase quartz amphibole and quartz biotite pairs reveal that putative annealing temperatures are lowest in ne trending axial portions of the barcroft body so it simply cooled inwards intrusion 70 million years later by the mcafee creek granite had no discernable effect on 18o values of barcroft minerals and bulk rocks

marine vadose beachrock cementation by cryptocrystalline magnesian calcite maui hawaii abstract active precipitation of high magnesian cryptocrystalline calcite cement 15 5 mole mgco3 in the intertidal zone on the north shore of maui hawaii results in formation of an extensive beachrock exposure at hookipa park framework grains in the beachrock are coarse algal molluscan and intraclast bearing sands meniscus fabric is dominant in the cement indicating that most lithification occurs in the vadose zone the cryptocrystalline cement is generally brownish gold in color but very thin clear isopachous fringes of microcrystalline calcite surround darker cryptocrystalline cement especially in upper horizons of the beachrock peloidal texture is scarce in the cement but is present in a few samples silt and fine sand sized skeletal fragments have been trapped in he evolving cement resulting in cement supported fabric hollow rims of microcrystalline calcite occupy some pore spaces these hollow rims may have precipitated at the air water interface of bubbles that formed in pores and they may therefore be additional evidence of cementation in the vadose zone interstitial water samples from wells that penetrate portions of the beachrock and unconsolidated beach sands reveal temporal chemical variations that suggest the importance of co2 degassing in the formation of beachrock cement when chemical and tidal cycles fluctuate with the same period pco2 values in pore water of the intertidal zone generally bear a direct relationship to tidal stand increasing values of pco2 most often occur during semi daily rising tides and decreasing values of pco2 occur during falling tides saturation ratios with respect to calcite vary in direct proportion to pco2 saturation levels generally increase during rising tides and decrease during falling tides t ese data suggest that co2 degassing during falling tides results in precipitation of calcite cement from pore water of the beach

improving the ginkgo co2 barometer implications for the early cenozoic atmosphere abstract stomatal properties of fossil ginkgo have been used widely to infer the atmospheric concentration of co2 in the geological past paleo pco2 many of these estimates of paleo pco2 have relied on the inverse correlation between pco2 and stomatal index si the proportion of epidermal cells that are stomata observed in recent ginkgo biloba and therefore depend on the accuracy of this relationship the si p co2 relationship in g biloba has not been well documented however here we present new measurements of si for leaves of g biloba that grew under pco2 from 290 to 430 ppm we prepared and imaged all specimens using a consistent procedure and photo documented each count as in prior studies we found a significant inverse relationship between si and pco2 however the relationship is more linear has a shallower slope and a lower correlation coefficient than previously reported we examined leaves of g biloba grown under pco2 of 1500 ppm but found they had highly variable si and a large proportion of malformed stomata we also measured stomatal dimensions stomatal density and the carbon isotope composition of g biloba leaves in order to test a mechanistic model for inferring pco2 this model overestimated observed pco2 performing less well than the si method between 290 and 430 ppm we used our revised si pco2 response curve and new observations of selected fossils to estimate late cretaceous and cenozoic pco2 from fossil ginkgo adiantoides all but one of the new estimates is below 800 ppm and together they show little long term change in pco2 or relation to global temperature the low paleogene pco2 levels indicated by the ginkgo si proxy are not consistent with the high pco2 inferred by some climate and carbon cycle models we cannot currently resolve the discrepancy but greater agreement between proxy data and models may come from a better understanding of the stomatal response of g biloba to elevated pco2 better counts and measurements of fossil ginkgo or models that can simulate greenhouse climates at lower pco2

concepts in gravel beach dynamics abstract the dominant processes in gravel beach dynamics are reviewed highlighting some common themes which unify the various components of the gravel beach system the repercussions of which impart on how gravel beach dynamics might be understood conceptually in particular gravel beach dynamics are thought to be highly dependent on the temporal and spatial variation in grain size and the continual adjustments made by an active beach step both of which act not only as the expression of changing morphodynamic conditions but also as a controlling influence morphodynamics the notion that the exchanges on beaches between the hydrodynamics sediment transport and morphological change takes the form of reciprocal relationships which are mediated through feedback mechanisms in such a way that they cannot be thought of or studied independently is not a new one yet it appears that for the gravel beach morphodynamics must be re defined to describe conditions where variations in sediment size are thought to deserve parity rather than as merely a sequent entity or boundary condition morpho sedimentary dynamics is a phrase coined to intuit such cause and effect detailing the co evolution of morphology hydro hydraulics and sediment properties whilst acknowledging causative pluralism feedbacks and multiplier effects this is the recommended conceptual framework within which to crystallise thought and organise further research for the gravel beach essentially it increases the minimum number of parameters needed to describe the state of the gravel beach as a physical system therefore it is advised that simplicity will be most expedient in our future modelling efforts if complexity is to be adequately encapsulated

beach groundwater dynamics abstract an understanding of the interaction between surface and groundwater flows in the swash zone is necessary to understand beach profile evolution coastal researchers have recognized the importance of beach watertable and swash interaction to accretion and erosion above the still water level swl but the exact nature of the relationship between swash flows beach watertable flow and cross shore sediment transport is not fully understood this paper reviews research on beach groundwater dynamics and identifies research questions which will need to be answered before swash zone sediment transport can be successfully modelled after defining the principal terms relating to beach groundwater the behavior measurement and modelling of beach groundwater dynamics is described research questions related to the mechanisms of surface subsurface flow interaction are reviewed particularly infiltration exfiltration and fluidisation the implications of these mechanisms for sediment transport are discussed

moderate levels of eocene pco2 indicated by southern hemisphere fossil plant stomata reducing the uncertainty in predictions of future climate change is one of today s greatest scientific challenges with many significant problems unsolved including the relationship between pco2 a

eocene paleontology and geology of western north america western north america preserves a rich record of eocene life and environments under globally warm climates and represents an interval where significant coal and other minerals were deposited the eocene is of interest to biologists and paleontologists for its record of the appearance and rise to dominance of many plant insect and mammal groups now typical of the temperate forests of north america admixed with groups now well represented in tropical areas or restricted to eastern asia this record is also of interest for its potential contribution to our understanding of interactions between climate the biota and the ecosystems they occupied under atmospheric carbon dioxide levels much higher than today documentation of the eocene in western north america offers insights into the effects of future greenhouse climates a special symposium held at the 2014 annual meeting of the geological society of america in vancouver british columbia brought together geologists paleontologists and biologists w

sea level and diagenesis a case study on pleistocene beaches whalebone bay bermuda pleistocene fluctuations of sea level have left marine and aeolian limestones intercalated with glacial red soils on the bermuda carbonate platform atlantic 64 50 w 32 20 n successive eustatic highstands of similar amplitude drowned the tectonically stable platform and piled up similar sets of sediments up to three pleistocene beaches are stacked in shorelines sections post depositional diagenetic histories of these beaches can be linked to repeated changes in sea level and pore waters

low atmospheric co 2 levels during the permo carboniferous glaciation inferred from fossil lycopsids earth history was punctuated during the permo carboniferous 300 250 million years myr ago by the longest and most severe glaciation of the entire phanerozoic eon but significant uncertainty surrounds the concentration of co2 in the atmosphere through this time interval and therefore its role in the evolution of this major prepleistocene glaciation here i derive 24 late paleozoic co2 estimates from the fossil cuticle record of arborsecent lycopsids of the equatorial carboniferous and permian swamp communities quantitative calibration of late carboniferous 330 300 myr ago and permian 270 260 myr ago lycopsid stomatal indices yield average atmospheric co2 concentrations of 344 ppm and 313 ppm respectively the reconstructions show a high degree of self consistency and a degree of precision an order of magnitude greater than other approaches low co2 levels during the permo carboniferous glaciation are in agreement with glaciological evidence for the presence of continental ice and coupled models of climate and ice sheet growth on pangea moreover the permian data indicate atmospheric co2 levels were low 260 myr ago by which time continental deglaciation was already underway positive biotic feedbacks on climate and geotectonic events therefore are implicated as mechanisms underlying deglaciation

patchy deposits of cenozoic pelagic sediments in the central pacific export of pelagic carbonate tests from surface waters and their deposition at the seafloor plays a significant role in the co 2 cycle and ability of the oceans to absorb atmospheric co 2 sediment 2 3 0 th and 3 he measurements have been interpreted as evidence that significant lateral advection of pelagic material occurs in the water column leading to marked spatial variations in deposition rates and in particular to significant focusing of deposits on the pacific equator we report spatially continuous stratigraphy from two 1000 km seismic lines that show evidence of depositional anomalies near the equator accumulation rates were apparently enhanced locally by a factor of two similar to the proposed modern sediment focusing factors but the anomalies are surprisingly patchy over the 20 m y period analyzed they are not confined to an equatorial region and they are not necessarily found on adjacent seismic profiles these intermediate scale anomalies are 100 km across and represent areas of seafloor that received more deposits for one period less in following periods and vice versa variogram analysis was used to determine how the spatial scales of deposition changed over the neogene the period when the spatial scale of depositional variability was largest correlates with hiatuses in drill cores a correlation that we interpret as caused by enhanced and spatially heterogeneous carbonate dissolution at that time the study suggests that seismic stratigraphy has the potential to reveal spatial patterns related to unsteady bottom water flow and chemistry

terrestrial paleoenvironmental reconstructions indicate transient peak warming during the early eocene climatic optimum major changes in climate and ecology occurred during the early eocene climatic optimum sometime between 52 and 50 ma recent work suggests that the timing and duration of the event are characterized by different responses in the marine and terrestrial realms and that traditional causal mechanisms may not adequately explain such differences we applied high resolution paleopedology geochemical analysis and phytolith biostratigraphy techniques to paleosol suites within the well described wind river formation of western wyoming usa this multiproxy record indicates a short 1 m y peak period of carbon isotopic enrichment up to 2 higher and elevated pco2 high temperatures up to 8 c higher increased precipitation up to 500 mm yr 1 higher and shifts in fl oral composition up to 10 terrestrial climatic and ecological changes of this kind during the early eocene climatic optimum are consistent with changes in contemporaneous records that have been ascribed to high atmospheric pco2 but a transient peak interval suggests that the cause of high atmospheric pco2 during the early eocene was likely not increased volcanism or decreased silicate weathering which operate on longer timescales instead terrestrial records from across western north america agree that early eocene climatic optimum changes may have been caused by other sources such as a combination of increased ventilation of oceanic carbon and increased petroleum generation in sedimentary basins the climatic and environmental changes exhibited by this and other north american terrestrial records also defi ne a pattern of regional response that is relevant for understanding the impacts of global climate change events

mid cretaceous pco2 based on stomata of the extinct conifer pseudofrenelopsis cheirolepidiaceae stomatal characteristics of an extinct cretaceous conifer pseudofrenelopsis parceramosa fontaine watson are used to reconstruct atmospheric carbon dioxide p co 2 over a time previously inferred to exhibit major fluctuations in this greenhouse gas samples are from nonmarine to marine strata of the wealden and lower greensand groups of england and the potomac group of the eastern united states of hauterivian to albian age 136 100 ma atmospheric p co 2 is estimated from the ratios between stomatal indices of fossil cuticles and those from four modern analogs nearest living equivalent plants using this approach and two calibration methods to explore ranges results show relatively low and only slightly varying p co 2 over the hauterivian albian interval a low of 560 960 ppm in the early barremian and a high of 620 1200 ppm in the albian data from the barremian wealden group yield p co 2 values indistinguishable from a soil carbonate based estimate from the same beds the new p co 2 estimates are compatible with sedimentological and oxygen isotope evidence for relatively cool mid cretaceous climates

radiocarbon evidence for the timing and rate of island development beach rock formation and phosphatization at lady elliot island queensland australia abstract lady elliot island great barrier reef is a coral cay constructed from near concentric shingle ridges composed of coral tridacna shells and bioclastic sand bound by guano derived phosphatic cement radiocarbon dating of individual tridacna samples is used to investigate the evolution of the island and place constraints on the variations in storminess of the last 3200 years a shallow platform reef existed at lady elliot since at least 6500 yrs b p shortly before 3200 yrs b p island growth by shingle progradation commenced and proceeded to the present at a rather uniform lateral rate 60 m ka 1 to leeward and 90 m ka 1 windward phosphatization may have occurred continuously or episodically at any time throughout the last 3200 years the youngest cemented ridge top is less than 770 years whereas at the base of uncemented ridges phosphatization is a modern 1950 a d process similarly low level beach rock has continued to form within the last 25 years a significant period of instability occurred less than 500 years ago during which marine erosion truncated the southwestern extremity of lady elliot island formed an eastern spit and stranded high level beach rock however the radiocarbon ages of tridacna samples from shingle ridges from lady elliot and curacoa islands are uniformly distributed kolmogorov smirnov test throughout the last 4000 years we interpret this to indicate no significant variation in ridge forming processes or fluctuation in average storminess during this interval

atmospheric carbon dioxide linked with mesozoic and early cenozoic climate change carbon isotopes of fossil plants and model simulations suggest that atmospheric carbon dioxide levels were variable during the period 200 to 60 million years ago the large decreases in the partial pressure of co2 coincide with glaciations providing evidence against climate co2 decoupling during the mesozoic

leaf stomatal frequency in the australian tropical rainforest tree neolitsea dealbata lauraceae as a proxy measure of atmospheric pco2 a putative relationship has been demonstrated for european and north american woody dicots and gymnosperms between leaf stomatal frequency and historical levels of atmospheric co2 however hitherto no such study has been presented for australian tropical broadleaved evergreen trees in this study variation of stomatal index si along environmental gradients is examined for the broadleaved evergreen tropical rainforest tree neolitsea dealbata lauraceae historical herbarium samples from natural populations in northeastern and southeastern queensland were analysed leaf si for neolitsea dealbata is shown to be insensitive to mean annual rainfall or seasonal totals or to temperature variables indicating the climatic factors that influence the water budget of the plants were not a factor controlling si contrary to the pattern most commonly observed in temperate areas si decreased with elevation for collections within a single year for 3 out of 4 years surveyed a pattern consistent with environmental factors other than pco2 acting as the control over si however an overall decrease in si was recorded for samples collected in queensland 30 17 s over the period 1899 1988 corresponding to a southern hemisphere increase in pco2 from 295 to 350 ppm restricting the analysis to sites within an altitudinal band of 640 1120 m demonstrated a significant relationship between si and pco2 r2 0 8942 f11 84 5 p 0 001 this data set was used to estimate atmospheric pco2 from fossil leaf cuticle for the closely related genus litsea giving pco2 values comparable to those estimated using ginkgo from northern hemisphere fossil sites

qaidam basin paleosols reflect climate and weathering intensity on the northeastern tibetan plateau during the early eocene climatic optimum abstract as an important geological archive paleosols have been widely used in reconstruction of paleoenvironmental and paleoclimatic conditions in this study we undertook detailed analyses of the clay mineralogy and carbon and oxygen isotopic compositions of pedogenic carbonates in a series of 13 paleosol horizons within a fluvial section of the eocene 52 44 ma lulehe formation in the qaidam basin pedogenic smectite and illite smectite i s mixed layer minerals are the predominant clay minerals in the paleosols suggesting that the early eocene paleoclimate of the qaidam basin was strongly seasonal with warm wet summers the high levels of pedogenic smectite production and high atmospheric pco2 reconstructed from soil carbonate nodule 13c mean 7 1 0 8 are consistent with elevated temperatures during the early eocene climatic optimum eeco coeval paleosol carbonate nodules yield estimated paleo surface water compositions 18opsw of 7 9 to 6 0 vsmow which are significantly higher than the 18o value of modern summer precipitation in the qaidam basin the estimated temperature difference 5 0 c cooling implies uplift of the study area by nearly 1000 m to its current average elevation of 3000 m above sea level this paleoelevation estimate agrees with modern meteoric water isotopes of global network of isotopes in precipitation gnip sites in asia in the same elevation range

holocene cemented beach deposits in belize abstract two types of cemented beach deposits occur on reef islands off the coast of belize these are 1 intertidal beachrock that is dominantly cemented by marine aragonite and high magnesium calcite cements and 2 supratidal cayrock that is cemented mainly by vadose low magnesium calcite cements besides differences in position relative to present sea level and resulting early diagenesic features beachrock and cayrock can be distinguished on the basis of differences in composition texture geographical position and age whereas the composition of beachrock is similar to that of the adjacent marginal reef sediments cayrock is enriched in benthic foraminifera intertidal beachrock is moderately to well sorted and well cemented while supratidal cayrock is very well sorted poorly cemented and friable beachrock occurs preferentially on windward beaches of sand shingle gays on the middle and southern barrier reefs and on the isolated platforms glovers and lighthouse reefs cayrock only occurs on larger mangrove sand gays of the isolated platforms turneffe islands lighthouse reef and the northern barrier reef 14c dating of ten whole rock and mollusk shell samples produced calibrated dates between ad 345 and ad 1435 for beachrock and between bc 1085 and ad 1190 for cayrock the large scale distribution of beachrock in belize supports the contention that physical processes such as water agitation rather than biological processes control beachrock formation and distribution only on windward sides of cays that are close to the reef crest where large amounts of seawater flush the beaches considerable amounts of cements can be precipitated to produce beachrock cayrock forms due to cementation in the vadose zone and is only preserved on larger stable mangrove sand cays

eocene atmospheric co2 from the nahcolite proxy estimates of the atmospheric concentration of co 2 co 2 atm for the hothouse climate of the early eocene climatic optimum eeco vary for different proxies extensive beds of the mineral nahcolite nahco 3 in evaporite deposits of the green river formation piceance creek basin colorado usa previously established co 2 atm for the eeco to be 1125 ppm by volume ppm here we present experimental data that revise the sodium carbonate mineral equilibria as a function of co 2 and temperature co precipitation of nahcolite and halite nacl now establishes a well constrained lower co 2 atm limit of 680 ppm for the eeco paleotemperature estimates from leaf fossils and fluid inclusions in halite suggest an upper limit for co 2 atm in the eeco from the nahcolite proxy of 1260 ppm these data support a causal connection between elevated co 2 atm and early eocene global warmth but at significantly lower co 2 atm than previously thought which suggests that ancient climates on earth may have been more sensitive to a doubling of co 2 atm than is currently assumed

declining atmospheric co2 during the late middle eocene climate transition the transition from the extreme greenhouse of the early paleogene 52 ma to the present day icehouse is the most prominent change in earth s cenozoic climate history during the late middle eocene climate transition 42 38 ma which preceded the onset of long lived continental scale ice sheets there is concor dant evidence for brief pulses 1 m y in length of global warmth and ice sheet growth but few constraints on atmospheric co 2 here we estimate the concentration of atmospheric co 2 during this critical interval using stomatal indices of fossil metasequoia needles from ten levels in an exceptionally well preserved core from the giraffe kimberlite locality in northwestern canada reconstructed co 2 concentra tions are mainly between 700 to 1000 ppm but include a secular decline to 450 ppm towards the top of the investigated section because the co 2 threshold for nucleating continental ice sheets at this time was 500 to 750 ppm the co 2 decline is compatible with a rapid 10 4 yrs transition from warm largely ice free conditions to cooler climates with ice sheets these fossils provide direct evidence that high latitude deciduous forests thrived in the geological past under co 2 concentrations that will likely be reached within the 21 st century 500 1000 ppm

fe co3 oh in goethite from a mid latitude north american oxisol estimate of atmospheric co2 concentration in the early eocene climatic optimum abstract measured mole fractions x and 13c values of the fe co3 oh component in pedogenic goethite from a mid latitude oxisol of early eocene age 52 ma b p range from 0 0014 to 0 0064 and 20 1 to 15 4 respectively these values of x imply that concentrations of co2 gas in the paleosol were 7400 to 34 000 ppm 13c and 1 x are correlated and define a linear soil co2 diffusive mixing line with a positive slope such positive slopes are characteristic of mixing of two isotopically distinct co2 endmembers atmospheric co2 and co2 from oxidation of soil organic matter from the intercept of the mixing line it is calculated that the 13c value of organic matter in the ancient soil was 28 0 the magnitude of the slope implies an early eocene atmospheric co2 concentration of 2700 ppm a simple model for forest soils suggests that a canopy effect may cause atmospheric co2 concentrations deduced from pedogenic minerals to underestimate the actual concentrations of atmospheric co2 if a significant forest canopy were present at the time of formation of pedogenic goethite in the ione fm the concentration of 2700 ppm calculated for atmospheric co2 could be slightly low but the underestimate is expected to be

regional and local vegetation community dynamics of the eocene okanagan highlands british columbia washington state from palynology palynofloras from the middle early to early middle eocene okanagan highlands northern washington state and southern british columbia are used to reconstruct vegetation across a broad upland eocene landscape in this preliminary report forest floristic composition is reconstructed using palynological analysis of sediments from republic washington localities of the allenby formation in the princeton region hospital hill one mile creek and summers creek road hat creek mcabee falkland horsefly and driftwood canyon british columbia wind dispersed taxa were dominant in all samples consistent with floras preserved in lacustrine and paludal depositional environments pseudolarix was dominant in five of the floras but abies falkland or ulmus republic corner lot site were dominant in individual samples for some floras betulaceae were dominant for mcabee alnus and allenby formation betula matching megafloral data for these sites some taxa common to most sites suggest cool conditions e g