lithostratigraphy of the 250 000 year record of lacustrine sediments from the valle di castiglione crater roma abstract sediments drilled by an 88 m borehole through the middle of the drained lake bed 1 km diameter were studied by macroscopic grain size mineralogical and geochemical analyses the catchment area 60 km 2 is composed of leucitic undersaturated volcanic rocks mainly of the pyroclastic type the lithostratigraphic sequence can be summarized as consisting of two alternating lithotypes which allows different palaeoclimatic influences to be drawn the first consists mainly of tuffaceous silts generally enriched with organic matter and aeolian quartz and contains heavy and weathered minerals it is interpreted as a sediment deposited with a predominantly terrigenous supply by the abundant surface waters flowing into the lake during wet climatic phases the second lithotype consists of silts with a predominantly carbonate component rich in mollusc shells but with low contents of organic matter aeolian quartz heavy and weathering minerals it is interpreted as a sediment deposited during relatively dry climatic phases with an abundant calcium bicarbonate supply which is relatively higher than the terrigenous one most of the sequence can be correlated with the palaeoclimatic variations inferred from oxygen isotopic stratigraphy dry intervals seem to be related to the winter solstice in the northern hemisphere when the earth is at perihelion

coupled ice ocean dynamics in the marginal ice zones upwelling downwelling and eddy generation this study is aimed at modeling mesoscale processes such as upwelling downwelling and ice edge eddies in the marginal ice zones a two dimensional coupled ice ocean model is used for the study the ice model is coupled to the reduced gravity ocean model through interfacial stresses the parameters of the ocean model were chosen so that the dynamics would be nonlinear the model was tested by studying the dynamics of upwelling winds parallel to the ice edge with the ice on the right produce upwelling because the air ice momentum flux is much greater than air ocean momentum flux thus the ekman transport is greater under the ice than in the open water the stability of the upwelling and downwelling jets is discussed the downwelling jet is found to be far more unstable than the upwelling jet because the upwelling jet is stabilized by the divergence a constant wind field exerted on a varying ice cover will generate vorticity leading to enhanced upwelling downwelling regions i e wind forced vortices steepening and strengthening of vortices are provided by the nonlinear terms when forcing is time varying the advection terms will also redistribute the vorticity the wind reversals will separate the vortices from the ice edge so that the upwelling enhancements are pushed to the open ocean and the downwelling enhancements are pushed underneath the ice

uranium series ages of travertines and timing of the last glaciation in the northern yellowstone area wyoming montana uranium series age determinations by mass spectrometric methods were done for travertines and associated carbonate veins related to clastic deposits of the last glaciation pinedale in the northern yellowstone area dramatic variations in the hydrologic head are inferred from variations in the elevation of travertine deposition with time and are consistent with the expected hydrologic effects of glaciation we determine the following chronology of the pinedale glaciation with the key assumption that travertine deposits and associated carbonate veins perched high above present thermal springs were deposited when glaciers filled the valley below these perched deposits 1 the early pinedale outlet glacier advanced well downvalley between 47 000 and 34 000 yr b p 2 the outlet glacier receded to an interstadial position between 34 000 and 30 000 yr b p 3 an extensive pinedale ice advance occurred between 30 000 and 22 500 yr b p 4 a major recession occurred between 22 500 and 19 500 yr b p 5 a minor readvance deckard flats culminated after 19 500 yr b p and 6 recession from the deckard flats position was completed before 15 500 yr b p this chronology is consistent with the general trend of climatic changes in the northern hemisphere as revealed by recent high resolution ice core records from the greenland ice sheet

cenomanian turonian carbon isotope events recorded in terrestrial organic matter from northern japan carbon isotopic fluctuations recorded in terrestrial organic matter from the upper cretaceous cenomanian turonian succession of hokkaido japan show a remarkably similar pattern to isotopic fluctuation in carbonate carbon reported from southern england and the italian apennines chronological correlation for the cenomanian turonian section of japan is based on planktonic foraminiferal biostratigraphy with some additional data from macrofossils allowing a detailed comparison of isotope stratigraphies for japan and europe three distinct features of the isotope profile namely a positive spike near the cenomanian turonian boundary a shoulder in the lower middle turonian and a level segment in the middle upper turonian are observed in japan these features are biostratigraphically comparable and correlative with isotope profiles reported from europe the single factor influencing isotopic composition of both terrestrial organic carbon and marine carbonate carbon is isotopic change in the global co2 reservoir of the ocean atmosphere system if these three carbon isotope features are synchronous they may be inferred as having been caused by global phenomena and as providing global high resolution chemo stratigraphic markers carbon isotope stratigraphy could be an important bridge between terrestrial inland sequences and marine sequences

a coupled ice ocean mixed layer model of the marginal ice zone responding to wind forcing a free drifting thermodynamic sea ice model is coupled with a continuously stratified ocean model whose vertical mixing coefficients are determined by a turbulent closure scheme the system has variability in the cross ice edge direction while two dimensionality along ice edge homogeneity is assumed the model is initially motionless and has no horizontal variability in ocean interior whereas ice covers only a half portion a uniform wind stress is imposed suddenly to drive the coupled system the surface mixed layer is developed as time increases i e a top few tens of meters are well mixed in a day with an initial water temperature above a freezing point the fresh mixed layer forms in the ice covered portion a wind driven ice velocity is oriented to the right from the wind direction a wind with the ice to the right left looking downstream produces upwelling downwelling under the ice edge caused by a difference in ekman transport an off ice on ice wind advects the ice toward the open water ice covered area and makes the ice edge sharper gentler owing partially to faster movement in the region with higher ice concentration in the off ice wind case the mixed layer near the ice edge is shallower under development so that a melt rate is smaller than that estimated by a prescribed depth mixed layer an inertio internal gravity wave is generated by a transient variability in surface stress associated with a moving ice edge most significantly in the case of the off ice wind and enhances sharpness of the ice edge

radiocarbon dating of residual organic matter in travertine formed along the yumoto fault in oga peninsula northeast japan implications for long term hot spring activity under the influence of earthquakes abstract radiocarbon dating was performed on trace amounts of organic matter included in travertines formed along the yumoto fault in oga peninsula ne japan the reliability of the dating method was confirmed by the consistency of ages obtained with the stratigraphy of the travertine mound and the ratio of carbon stable isotopes the radiocarbon chronology of the travertines shows that 1 the hot springs at oga have been active for approximately 29 000 years with average depositional rates ranging from 0 24 to 1 75 mm yr and 2 the principal hot spring activity has migrated southward with time variations in the accumulation rates and the progressive migration of the main focus of the hot spring activity imply irregular spring behaviour this behaviour has not been influenced by paleoclimate but may have been controlled by the earthquakes that occur frequently in the region around oga peninsula

u th dating of freshwater travertine from middle velino valley central italy paleoclimatic and geological implications abstract six travertine bodies outcropping along the middle velino valley central italy have been studied and dated using the u th method in order to obtain new chronological constraints for the recent geological evolution of the area the lithological and sedimentological characteristics of travertines have been described showing that such deposits can be referred to waterfall pool terraces and gentle slopes environment travertines have formed during warm periods and can be referred to marine oxygen isotope stages 5 3 and 1 travertine deposition seems to stop around 5 ka bp according to other european and italian sites pollen stratigraphy and ostracod assemblages from the close sequence of valle di castiglione characterized by the same climatic conditions of velino valley have confirmed that periods of velino valley travertine deposition were effectively characterized by warm and wet climatic conditions seismic activity strongly active in the area since the middle pleistocene has deeply influenced the location and the discharge of springs which have deposited the travertines influencing in turn the shape and size of travertine bodies

submarine spring controlled calcification and growth of large rivularia bioherms late pleistocene mis 5e gulf of corinth greece the cyanobacterium rivularia haematites has calcified to form unusually large up to 10 m high bioherms in the pleistocene gulf of corinth today r haematites calcifies only in freshwater environments but these gulf of corinth bioherms have a brackish affinity limited areal extent and occur within marine deposits field relations and preliminary u series dating suggest a marine isotope stage mis 5e age for the bioherms this age is compatible with published mis 5e ages for corals in the marine sediments above the bioherms and is consistent with their current elevation based on average uplift rates bioherm growth during mis 5e constrains their formation during a time of near sea level highstand when the gulf of corinth was marine growth cavities in the bioherms are encrusted by brackish tolerant coralline algae field mapping of the mis 5e highstand palaeoshoreline shows the bioherms grew in water

comment on first records of syn diagenetic non tectonic folding in quaternary thermogene travertines caused by hydrothermal incremental veining by billi et al tectonophysics 700 701 2017 60 79 abstract billi et al 2017 proposed a new interpretation for the origin and internal structure of thermogene travertine deposits on the basis of evidence from two quarries located in southern tuscany italy they interpreted some travertine beds as calcite veins and argued that undulating travertine beds formed by syn diagenetic i e non tectonic folding that was caused by laterally confined volume expansion caused by incremental veining they assumed that such a process causes changes to the rock properties including porosity reduction rock strengthening and age rejuvenation the interpretations by billi et al 2017 challenge and question the current understanding and interpretation of thermogene travertine deposits this understanding based on numerous studies since the 1980s is that these deposits form from thermal water flowing downslope and precipitating calcium carbonate here we explain how the comparison with active depositional systems is essential for the understanding the origin of structures in older inactive travertine deposits such as those studied by billi et al 2017 we further argue that the three dimensional setting of travertine deposits should be taken into account in order to discuss the possible development of secondary structures indeed travertine deposition on slopes typically leads to the formation of terraced morphologies with pools bordered by rounded rims and separated from each other by steep walls the resulting three dimensional structures can be misinterpreted as asymmetric folds in two dimensional views i e in saw cut walls of quarry in this paper we debate the interpretations offered by billi et al 2017 and their criteria to recognise syn diagenetic non tectonic folds in travertine deposits and explain why many of their ideas are questionable

rise and fall of late pleistocene pluvial lakes in response to reduced evaporation and precipitation evidence from lake surprise california widespread late pleistocene lake systems of the basin and range province indicate substantially greater moisture availability during glacial periods relative to modern times but the climatic factors that drive changes in lake levels are poorly constrained to better constrain these climatic forcing factors we present a new lacustrine paleoclimate record and precipitation estimates for lake surprise a closed basin lake in northeastern california we combine a detailed analysis of lake hydrography and constitutive relationships describing the water balance to determine the influence of precipitation evaporation temperature and seasonal insolation on past lake levels at its maximum extent during the last deglaciation lake surprise covered 1366 km 2 36 of the terminally draining surprise valley watershed using paired radiocarbon and 230 th u analyses we dated shoreline tufa deposits from wave cut lake terraces in surprise valley california to determine the hydrography of the most recent lake cycle this new lake hydrograph places the highest lake level 176 m above the present day playa at 15 19 0 18 calibrated ka 14 c age this significantly postdates the last glacial maximum lgm when lake surprise stood at only moderate levels 65 99 m above modern playa similar to nearby lake lahontan to evaluate the climatic factors associated with lake level changes we use an oxygen isotope mass balance model combined with an analysis of predictions from the paleoclimate model intercomparison project 3 pmip3 climate model ensemble our isotope mass balance model predicts minimal precipitation increases of only 2 18 during the lgm relative to modern compared to an 75 increase in precipitation during the 15 19 ka highstand lgm pmip3 climate model simulations corroborate these findings simulating an average precipitation increase of only 6 5 relative to modern accompanied by a 28 decrease in total evaporation driven by a 7 c decrease in mean annual temperature lgm pmip3 climate model simulations also suggest a seasonal decoupling of runoff and precipitation with peak runoff shifting to the late spring early summer from the late winter early spring our coupled analyses suggest that moderate lake levels during the lgm were a result of reduced evaporation driven by reduced summer insolation and temperatures not by increased precipitation reduced evaporation primed basin and range lake systems particularly smaller isolated basins such as surprise valley to respond rapidly to increased precipitation during late heinrich stadial 1 hs1 post lgm highstands were potentially driven by increased rainfall during hs1 brought by latitudinally extensive and strengthened midlatitude westerly storm tracks the effects of which are recorded in the region9s lacustrine and glacial records these results suggest that seasonal insolation and reduced temperatures have been underinvestigated as long term drivers of moisture availability in the western united states

230th 234u dating of holocene tufas possibilities and problems high resolution chronologies in continental carbonate deposits such as tufas are required for detailed palaeoclimatic and environmental studies this work set out to establish if high resolution u series dating of detritus rich holocene tufas is routinely possible the study centres on a paludal holocene tufa from southern england that already has an existing holocene chronology based on 14c and supported by biostratigraphy against which to compare u series dates the results show that significant detrital contamination combined with low initial u concentrations and short time for ingrowth of radiogenic 230th make high resolution u series dating of holocene tufa very difficult moreover a single 230th 232th initial value to correct for the presence of detrital 230th is not appropriate at the study site a finding that may apply to most holocene tufas total sample dissolution of coeval samples demonstrates considerable variability in the isotopic composition of the detritus the total sample dissolution data are too scattered to constrain chronologies at the required resolution and may indicate the incorporation of a 230th rich component in the detritus

a coupled ice ocean model of ice breakup and banding in the marginal ice zone a coupled ice ocean numerical model for the marginal ice zone is considered the model consists of a nonlinear sea ice model and a two layer reduced gravity ocean model the dependence of the upwelling response on wind stress direction is discussed the results confirm earlier analytical work it is shown that there exist directions for which there is no upwelling while other directions give maximum upwelling in terms of the volume of uplifted water the ice and ocean is coupled directly through the stress at the ice ocean interface an interesting consequence of the coupling is found in cases when the ice edge is almost stationary in these cases the ice tends to break up a few tenths of kilometers inside of the ice edge

wave propagation in the marginal ice zone model predictions and comparisons with buoy and synthetic aperture radar data in this paper the ocean wave dispersion relation and viscous attenuation by a sea ice cover are studied for waves propagating into the marginal ice zone miz the derivation of the dispersion relation and the viscous attenuation by an ice sheet are discussed for waves under flexure and pack compression in the miz the flexure effect is important for short waves for a fixed wave period the changes in wavelength and group velocity as a function of ice thickness are significant in turn the exponential wave attenuation rate shows a rollover at short wave periods whereby the rapid increase in wave attenuation rate with decreasing wave period slows down or even turns into a decrease the labrador ice margin experiment limex conducted on the miz off the east coast of newfoundland canada in march 1987 provides us with aircraft synthetic aperture radar sar imagery wave buoy and ice property data on the basis of the wave number spectrum from the sar data and the concurrent wave frequency spectrum from the ocean buoy data and accelerometer data on the ice during limex 87 the dispersion relation has been estimated and compared with a model wave energy attenuation rates are estimated from sar data and the ice motion package data which were deployed at the ice edge and into the ice pack and compared with the model the model data comparisons are reasonably good for the ice conditions observed during limex 87 some previously reported data of wave attenuation in the miz are revisited for model comparison

u series dating of the travertine depositing near the rongma hot springs in northern tibet china and its paleoclimatic implication abstract high resolution age data obtained by travertine dating is necessary for the reconstruction of paleoclimate and palaeohydrology near rongma hot springs in northern tibet u series dating of a travertine cone depositing in the study area was used the results show that the u contents of the travertine samples range from 0 298 to 1 363 ppm and the 234 u 238 u is in the rage of 1 475 1 700 indicating that the deposition of travertine near the rongma hot springs is stable and continuous the age of the travertine samples ranges from 11 500 to 4600 a corresponding to the first stage of mis 1 combination of the first stage of mis with the effect of monsoon climate of the indian ocean in the same period implies a warm and humid climate during the deposition of the travertines in the study area the u series age range in the rongma hot springs area is coincident with that of the travertine in southern tibet the age data detected from travertine cone help in understanding the evolution of hydrogeology of the hot spring area high resolution age data must be acquired before travertine can be confidently used as a paleoclimatic archive

osl dating of brazilian fluvial carbonates tufas using detrital quartz grains abstract robust chronologies for quaternary fluvial carbonate sediments tufas from brazil are still challenging we obtain optically stimulated luminescence osl ages of brazilian tufa deposits using the single aliquot regeneration sar dose protocol applied to single grains and multigrain aliquots of quartz extracted from tufa matrix additionally radiocarbon 14 c ages were obtained for the carbonate matrix and organic matter from tufas the methodology was applied in samples from tufa deposits in southwestern and southeastern regions with quaternary carbonate deposition equivalent doses distributions have overdispersion between 19 and 81 indicating that the studied samples comprise well bleached as well as poorly bleached sediments the quartz grains extracted from the studied tufas show an osl signal dominated by the fast component and reliable dose response curves with saturation doses 2 d 0 ranging from 35 to 210 gy most of the samples has low radiation dose rates 0 40 0 02 to 0 78 0 05 gy ka with variation in the water content due to compaction and matrix recrystallization being the major factors that could induce dose rate changes through time hard tufa samples with intense carbonate cementation show quartz osl ages from 51 9 4 8 to 150 3 35 9 years these ages are much older than the radiocarbon ages of the carbonate matrix and organic matter the osl ages of soft tufa samples related with the active fluvial system ranged from 0 8 0 1 to 5 5 0 4 years and are in the same interval of radiocarbon ages presented in the previous works we interpret that carbonate recrystallization or uptake of organic matter after tufa formation are responsible for the younger radiocarbon ages compared to quartz osl ages in the older tufa samples for these samples age differences vary up to tens of thousands years between deposition of quartz grains and the last episode of carbonate recrystallization or organic matter uptake consequently we believe that the obtained osl ages are the best estimates for the starting deposition time of the studied tufa samples

azimuthal modulation of c band scatterometer spl sigma sup 0 over southern ocean sea ice in a continuing evaluation of the ers 1 c band scatterometer as a tool for studying polar sea ice the authors evaluate the azimuthal modulation characteristics of antarctic sea ice ers 1 ami scatterometer mode data sets from several study regions dispersed in the antarctic seasonal sea ice pack are evaluated for azimuthal modulation when appropriate the incidence angle dependence is estimated and removed in a study region before determining whether azimuthal modulation is present in the data other comparisons are made using the fore and aft beam measurement difference the results show that over the ice pack azimuthal modulation is less than 1 db at the scale of observation of the ers 1 c band scatterometer

a coupled ice ocean model of a wind driven coastal flow ice movement driven by winds along the coast is studied using a two dimensional vertical seaward ice ocean coupled model right hand alongshore winds are given when internal ice stresses are important to determine the ice movement these winds induce right hand coastal currents and ice movement a shoreward ekman flow beneath the ice is a major mechanism to constrain the ice over the shelf balancing the internal ice pressure gradient when the wind ceases the ice decreases its alongshore velocity and the ice covered band becomes wider the alongshore ice velocity is sensitive to ice shear strength which determines the shear stress at the coast i e weak strong shear strength allows a large small ice velocity at the coast resulting in intense weak ekman flow and downwelling which induces a fast slow coastal current the alongshore velocity is also sensitive to the relatively small cross shore component of the wind i e the seaward shoreward component reduces induces the shear stress and allows large small ice velocity the results are applied to the ice over the labrador shelf

long term behaviour of continental hydrothermal systems u series study of hydrothermal carbonates from the french massif central allier valley abstract u series dating of hydrothermal carbonates deposited by co2 rich thermo mineral waters of the french massif central provides new insights on the long term behaviour of a continental hydrothermal system dating of aragonite veins and travertines impregnating old terrace levels of the allier river allowed identification of the main episodes of surface deposition and thus factors likely to influence these circulations fifteen layers from three veins and four travertines from two separate areas were analysed sr isotope compositions were also measured on vein samples the results show that this region was subjected to at least 3 main episodes of surface or near surface hydrothermal deposition 253 to 208 ky 135 to 100 ky and less than 8 ky comparison of these ages with a global climatic curve indicates that preferential deposition of carbonates occurs during warm periods suggesting a strong influence of climatic conditions on the hydrothermal system it is suggested that this climatic influence does not necessarily imply the absence of carbonate deposition during cold and dry periods but rather that carbonate precipitation might occur at depth before the geothermal fluids reach the surface in addition the isotope compositions of fluids recorded by the 87sr 86sr and 234u 238u initial ratios in the aragonite veins from coudes remained remarkably constant over 250 ky ranging from 0 71360 to 0 71371 and from 3 10 to 3 39 respectively the two samples coming from saladis show a slightly higher 234u 238u initial ratio around 3 95 the constancy of these ratios over such a long period suggests a hydrothermal system in a near steady state with respect to water rock interaction we thus propose a possible model allowing a conservative steady state despite variations in the water recharge rates in response to the climatic variations the difference between 234u 238u initial ratios measured in the coudes and saladis systems suggests the existence of two separate reservoirs and constrains their lateral extension to a few km at most

observation of wave refraction at an ice edge by synthetic aperture radar in this note the refraction of waves at the ice edge is studied by using aircraft synthetic aperture radar sar penetration of a dominant swell from open ocean into the ice cover was observed by sar during the labrador ice margin experiment limex conducted on the marginal ice zone miz off the east coast of newfoundland canada in march 1987 at an ice edge with a large curvature the dominant swell component disappeared locally in the sar imagery six subscenes of waves in the miz from the sar image have been processed revealing total reflection refraction and energy reduction of the ocean waves by the ice cover the observed variations of wave spectra from sar near the ice edge are consistent with the model prediction of wave refraction at the ice edge due to the change of wave dispersion relation in ice developed by liu and mollo christensen 1988

lakes as paleoseismic records in a seismically active low relief area rieti basin central italy abstract small lakes in low relief areas are atypical candidates for studies on paleoseismicity but their sediments can contain seismically induced event layers seismites generated through strong ground shaking sediment transport hydrological reorganization and or changes in groundwater chemistry and flow lakes lungo and ripasottile are shallow lakes

sedimentary patterns in perched spring travertines near granada spain as indicators of the paleohydrological and paleoclimatological evolution of a karst massif perched spring travertines of the granada basin south spain constitute a perched system with four well defined steps which are formed by several facies associations deposited in different sub environments travertine pools dams and cascades these perched travertines are considered as a freshwater reef system with a facies zonation and stratigraphic architecture closely resembling that of marine reef terraces and prograding carbonate platforms the travertine deposits have been dated by 230 th 234 u and 14 c methods as in other mediterranean areas the travertine deposition occurred episodically during warm and wet interglacial periods coinciding with isotopic stages 9 7 and 5 and with the transition between isotopic stages 2 1 during these periods underground dissolution large outflow in the springs and subsequent calcium carbonate precipitation occurred in the same way that evolution of reef systems indicates sea level changes the geomorphology age and architecture of perched spring travertine systems may be used to interpret former climatically controlled changes in outflow in base level marked by the altitude of springs and in the chemistry of spring waters thus aggradation or climbing progradation may indicate an increase of outflow at the spring progradation with toplap is due to a stable base level and conversely dowlapping progradation may signify that the base level was gradually dropping therefore the travertines can be considered semiquantitative indicators of the paleohydrological evolution of karstic massifs and used as an important terrestrial proxy climate record d 2003 elsevier science b v all rights reserved

mesoscale eddies in the fram strait marginal ice zone during the 1983 and 1984 marginal ice zone experiments during the summer marginal ice zone experiment in fram strait in 1983 and 1984 fourteen mesoscale eddies in both deep and shallow water were studied between 78 o and 81on sampling combined satellite and aircraft remote sensing observations conductivity temperature depth observations drift of surface and subsurface floats and current meter measurements typical scales of these eddies were 20 40 km rotation was mainly cyclonic with a maximum speed in several cases subsurface of up to 40 cm s observations further suggest that the eddy lifetime was at least 20 to 30 days five generation sources are suggested for these eddies several of the eddies were topographically trapped while others primarily formed by combined baroclinic and barotropic instability moved as much as 10 15 km d with the mean current the vorticity balance in the nontrapped eddies is dominated by the stretching of isopycnals accompanied by a change in the radial shear in the most completely observed eddy south of 79on the available potential energy exceeded the kinetic energy by a factor of 2 quantitative estimates suggest that the abundance of these eddies enhances the ice edge melt up to 1 2 km d

warm period growth of travertine during the last interglaciation in southern germany abstract late quaternary travertine at two sites near stuttgart formed entirely during interglacial periods the travertine contains structures from growth induced by bacteria and such structures have been dated by 230th u mass spectrometry the resulting ages from both sites imply growth episodes of short duration with growth rates up to 5 mm yr 1 at 99 800 1300 yr b p 2 n 8 and 105 900 1300 yr b p 2 n 7 these episodes were likely part of marine isotope stage mis 5 3 deposition of silt interrupted travertine growth at one of the sites 105 000 yr b p likely correlatives of this silt are the st germain i b stade recorded in the grand pile peat bog and a cold episode 1000 yr long recorded by 18o values in the grip ice core travertine also formed during stage 5 5 115 000 yr and during the early holocene we found no evidence for travertine accumulation in stages 2 3 4 and 5 1 at both sites the sr u ratio and the initial 234u 238u activity ratio resemble those of modern spring water however the sites differ in the chemical composition of spring water and in stratigraphic sequence of travertine accumulation

oceanography of the eastern bering sea ice edge zone in spring1 the ice edge region of the southeast bering sea was studied in terms of the hydrographic regime phytoplankton biomass and primary productivity during the springs of 1975 through 1977 the results showed that a phytoplankton bloom occurs at the ice edge just as the spring ice decay period begins and that this accounts for a significant proportion of the annual carbon input over the shallow shelf the bloom is intensified in time and space by the influence of the ice edge on the physical structure of the water column specifically melting ice seems to increase the stability of the water column near and under the ice by lowering the salinity frontal structure in salinity and temperature are apparent at the ice edge and are attributed to the melting ice but also at times to wind driven ekman type upwelling these data are also related to recent short term ca months year climatic fluctuations that seem to control the seasonal position of the ice edge zone relative to the shelf break in cold years the ice edge comes southward to the shelf break and overlies the more nutrientrich alaska stream bering sea source water in warm years the ice edge zone does not reach this nutrient rich water this may be important to the biology of the ice edge ecosystem the edge zones of seasonal sea ice are biologically productive serving as focal points for the congregation of large numbers of marine birds and mammals and thus represent ecologically critical habitats in subpolar regions the presence of a cold and solid boundary influences the biological regime in several ways including effects on the physical and chemical regimes in the adjacent seawater at least three structural features of the water column often associated with high oceanic primary production can occur in such an area simultaneously water column stability frontal structures and under certain conditions ice edge upwelling we show here that there is enhanced primary production due to water column stability and frontal structure at the edge of the seasonal sea ice in spring our data also suggest that ice edge upwelling occurs we show further that the intense

development of quaternary travertines in the carbonate mountains of the western costa del sol malaga southern spain the predominantly carbonate nature of the mountains near the coast of malaga and marbella costa del sol southern spain and the presence of springs have favored the formation of travertine buildups during the quaternary the geomorphic characteristics of the slopes and the location of the springs have determined the development of three types of travertine growths 1 spring travertines located preferentially on the south mountainside where the slope is steepest 2 pool dam cascade travertines which form along the north and east edges far from the carbonate relief and with a gentler slope and 3 river valley travertines formed in the courses of the springs of any sector field observations combined with new amino acid racemization aar dating of helicidae gastropods show that most of the travertine formations are polyphasic and that their development was interrupted by stages of erosion and incision five stages of travertine development are evident most of which are related to warm moist episodes corresponding to marine oxygen isotope stages mis 7 5 3 and 1 although local travertine growth also occurred during mis 6 and during the transition from mis 3 to 2

a multidisciplinary approach to understanding carbonate deposition under tectonically controlled hydrothermal circulation a case study from a recent travertine mound in the euganean hydrothermal system northern italy a multidisciplinary study was carried out on an upper pleistocene travertine mound montirone hill abano terme south of padova veneto italy with the aim of developing a comprehensive understanding of the processes interacting in structurally controlled thermal springs and the consequent deposition of thermal limestones the sedimentology geochemistry structural characteristics and hydrogeology of the mound which is associated with the euganean geothermal field and the related complex structural framework of the schio vicenza fault system were investigated a palaeo environmental model of the deposit has been reconstructed clarifying the connection between the travertine deposition and the regional structural setting calcium rich thermal waters rose from spring orifices estimated temperature from 54 c to 61 c based on geochemical calculations and produced a mound made of coalescent shield like bodies the dominant lime mudstone facies resulted from the accumulation of lime mud at the bottom of shallow crater like basins located on top of stacked cones soft sediment deformations affecting the lime mud sediment were most probably produced by the recurrent uprising of gas bubbles the overlying crystalline crusts were deposited on the flanks of the mound by waters overflowing from the vents with laminar flux a deep hydrothermal circuit with a long period of water rock interaction is supported by geochemical analyses furthermore a local extensional regime enhancing the migration of thermal fluids to the surface is inferred based on the results of the structural analysis carried out on the fault fracture mesh that affects the mound these results corroborate the well established relation among travertine deposits hydrothermal systems and fault systems and substantiate the structurally controlled conceptual model of the euganean hydrothermal system suggesting that both the thermal and the fault systems were active at least since 34 ka

tufas and travertines of the mediterranean region a testing ground for freshwater carbonate concepts and developments actively forming travertine and tufa sites are widespread in temperate and warm climates such as the mediterranean region but also develop in other climatic regimes from the arctic to equatorial latitudes the terms travertine and tufa are sometimes applied indiscriminately today however each has a specific definition most studied deposits are active or of quaternary especially holocene age there are fewer tertiary and even less late mesozoic examples on record in part this is because of a recognition problem as these deposits commonly preserve as fragmentary erosional remnants physico chemical precipitation of calcium carbonate is commonly considered to be the main mechanism contributing to tufa and travertine deposition rapid cooling of waters further aids the process in thermal travertine sites however biomediation of calcium carbonate associated with prokaryote microphyte biofilms is now recognized to be equally important in slow flowing and near static sites much of this precipitation occurs in close association with cyanobacterial heterotrophic bacterial and diatoms the mediterranean region figures significantly in the development of travertine and tufa research consequently this article employs key literature on mediterranean examples to illustrate developments and concepts in freshwater carbonate research modern work started in the 1950s and defined many previously unknown outcrops many such sites became the targets for early radiocarbon dating studies since the late 1970s a number of laboratory based and field based classification schemes have been proposed some schemes were based on associated macrovegetation types others were based on petrological characteristics or on geometry and sedimentary facies characteristics of late the sedimentological modelling has benefited greatly from the use of shallow geophysical techniques in order to better define the internal geometries of the deposits two distinct research strands were developed during the 1990s both aimed at a better understanding of environmental change the first considered biocomponents the research was multifaceted and ranged from exploring the role of micro organisms in cement and lime mud precipitation to biostratigraphic analysis of contained pollen and invertebrate remains these provided proxy environmental information which has helped to define past climate variability in the region the second research strand focussed on geochemical signatures as a proxy tool for defining environmental change this definition was made possible by new petrological studies which have greatly aided the recognition of primary depositional fabrics this improved knowledge has reduced the sampling dangers of diagenetic contamination inherent in earlier geochemical studies lithofacies modelling has also brought to light important early post depositional neomorphic changes which obscure primary fabrics and complex diagenetic histories have been revealed stable isotope signatures of carbon and oxygen have also been used to define palaeo water temperature fine tuning of depositional time frames has also been achieved from absolute dating techniques employing radiocarbon and uranium thorium

mesoscale eddies of the arctic ocean subsurface baroclinic eddies in the arctic ocean have a diameter of 10 20 km and are confined in depth between 50 and 300m during the arctic ice dynamics joint experiment aidjex in the central beaufort sea between march 1975 and may 1976 extensive information on eddy characteristics statistics and behavior was collected from four manned drifting ice camps during this 14 month period 146 eddies were encountered of which 19 were found to be repeated crossings making a total of 127 separate eddies observed during this period on the basis of the 1975 1976 aidjex data set it is concluded that eddies are 1 prevalent in the amerasia basin of the arctic ocean and in particular the beaufort sea where they may occupy up to a quarter of the available surface area 2 located in the depth range of 50 300 m although a few deeper eddies are also present 3 the second largest producers 32 of kinetic energy found within the upper 200 m of the beaufort sea and 4 predominantly anticyclonic in rotational tendency these eddies apparently originate north of point barrow alaska as a result of instability in the eastward flowing alaskan coastal current and transfer seasonally varying water properties from the chukchi sea and alaskan shelf into the arctic ocean they appear to translate in response to barotropic forcing over short time scales and over longer time periods move with the mean geostrophic field the season of formation for an eddy may be identified by the anomalous thermal properties still residing in its core

waves in frazil and pancake ice and their detection in seasat synthetic aperture radar imagery a theoretical model of waves propagating into an ice cover composed of frazil and pancake ice is developed and compared with measurements of wavelength and direction derived from synthetic aperture radar sar imagery obtained from seasat in october 1978 the theoretical model is based on the concept that ice of these types which consists of small crystals or cakes has only a mass loading effect on the water surface we derive the dispersion relation for phase and group velocities finding that there is an upper frequency limit for propagation into the ice from the reflection coefficient at the ice edge we derive the wave radiation pressure exerted on the ice showing that it will cause a slick of frazil ice backed by thicker floes to become more dense or thick with increasing penetration the implications for radar scattering enabling detection on sar are that the bragg resonant wavelength corresponds to waves above the frequency limit for propagation so that a frazil slick appears dark on an sar image when the frazil ice becomes transformed into pancake ice through slick compression or other means the raised edges of the pancakes cause the ice to appear bright despite the fact that there are no waves present at the bragg wavelength these results are applied to a seasat sar image obtained from the chukchi sea the appearance of the ice in the image corresponds to what we expect for frazil ice gradually transforming itself into pancake ice backed by thicker floes we derive directional wave number spectra outside and inside the ice cover by digital fourier analysis of image subscenes and we find that the change of wavelength and angle of refraction of the dominant wave entering the ice field are both characteristic of the dispersion relation derived theoretically mean ice thicknesses extracted from the theory correspond to thicknesses expected for such slicks the technique offers a possible means of extracting the thickness of fields of frazil and pancake ice from sar imagery this may be of considerable utility when ers 1 sar is used to study the advancing winter ice edge in the antarctic which consists of vast areas of these ice types

uranium series dating applications in natural environmental science uranium series u series analyses are an essential component of many research projects in earth and environmental science oceanography hydrology and science based archaeology topics range from magma chamber evolution and volcanic hazard prediction global climatic change through dating of authigenic carbonate deposits human evolution through dating of bone to the study of groundwater evolution the u series decay chains contain many elements that can be fractionated in environmental and geological processes half lives of radioactive isotopes of such elements range from seconds to many millennia and application depends on the natural timeframe of the process or the elapsed time this review will be limited to some aspects of the 238u 234u 230th 226ra system with half lives of 245 kyr 76 kyr and 1 6 kyr respectively in environmental systems fractionation of uranium and thorium is a very efficient process because thorium is extremely insoluble while hexavalent uranium in oxidising conditions is relatively soluble many authigenic precipitates of calcite contain virtually no thorium and inorganic precipitates have u ca ratios very similar to the ratio of dissolved uranium and calcium almost no radiogenic 230th in the precipitate means that the radiogenic clock starts effectively at zero however pure authigenic precipitates are rare and many contain some allogenic material mostly silicate with 238u in secular equilibrium with significant 230th some of the characteristics of different types of samples and various methods to accommodate or correct for inherited 230th will be discussed authigenic material should remain a closed system with respect to the relevant isotopes but that requirement is sometimes difficult to maintain because radioactive decay results in damage to the crystal lattice of the host mineral consequences of this recoil effect and correction schemes will be discussed dating archaeological bone based on the systematics of diffusion and adsorption to effectively model open system behaviour is also included

an isotopic study of biogeochemical relationships between carbonates and organic carbon in the greenhorn formation carbon isotopic compositions of total carbonate inoceramid carbonate micritic carbonate secondary cements total organic carbon and geoporphyrins have been measured in 76 different beds within a 17 m interval of a core through the greenhorn formation an interbedded limestone and calcareous shale unit of cretaceous age cenomanian turonian from the western interior seaway of north america results are considered in terms of variations in the processes of primary production which led to the biosynthesis of the molecular precursors of the geoporphyrins and in secondary processes those mediating the transformation of primary organic material into sedimentary total organic carbon it is shown that the porphyrin isotopic record reflects primary isotopic variations more closely than the toc isotopic record and that in these sediments toc is enriched in 13c relative to its primary precursor by 0 6 to 2 8 this enrichment is attributed to isotope effects within the consumer foodweb and is associated with respiratory heterotrophy variations in this secondary enrichment are correlated with variations in the isotopic composition of marine carbonate this correlation is attributed to effects of environmental changes on the marine foodweb these may have included increased atmospheric oxygen associated with the cenomanian turonian oceanic anoxic event the isotopic fractionation associated with fixation of carbon by primary producers is observed to have varied by 1 5 during the interval of deposition it is suggested that this change is due to a variation in the makeup of the community of primary producers and or to a decrease in the atmospheric abundance of co2 during the oceanic anoxic event

the late holocene tufa decline in europe over much of europe it has been postulated that in the late holocene since c 2500 bp there was a marked decline in the deposition of tufa there has been considerable debate about the causes of this phenomenon with some authors postulating the importance of natural climatic changes and others asserting that miscellaneous human influences have been crucial this article discusses the role that various changes both natural and anthropogenic may have played and suggests ways in which the large number of possible hypotheses can be tested

a theoretical laboratory and field study of ice coupled waves field and laboratory data of ice coupled waves propagating beneath shore fast ice are presented and compared with a theoretical model for sea ice which allows temperature variation although the laboratory data set is essentially qualitative because of scaling problems the measured wave characteristics compare favorably with those seen in the field the theory fits the field data set well both for the dispersive behavior and for the energy decay as the ice coupled waves penetrate the ice sheet moreover a maximum displacement suggested by theory is seen in field data for the first time it is proposed that this peak may be associated with the breakup of shore fast ice in exposed regions the theoretical treatment presented assumes sea ice to be thermorheologically simple an untested hypothesis which will require later experimental verification however the theory is quite general and can be used to solve a variety of sea ice mechanical problems where creep is considered important but where the loads and displacements are small enough that linearity prevails

2700 years of mediterranean environmental change in central italy a synthesis of sedimentary and cultural records to interpret past impacts of climate on society abstract abrupt climate change in the past is thought to have disrupted societies by accelerating environmental degradation potentially leading to cultural collapse linking climate change directly to societal disruption is challenging because socioeconomic factors also play a large role with climate being secondary or sometimes inconsequential combining paleolimnologic historical and archaeological methods provides for a more secure basis for interpreting the past impacts of climate on society we present pollen non pollen palynomorph geochemical paleomagnetic and sedimentary data from a high resolution 2700 yr lake sediment core from central italy and compare these data with local historical documents and archeological surveys to reconstruct a record of environmental change in relation to socioeconomic history and climatic fluctuations here we document cases in which environmental change is strongly linked to changes in local land management practices in the absence of clear climatic change as well as examples when climate change appears to have been a strong catalyst that resulted in significant environmental change that impacted local communities during the imperial roman period despite a long period of stable mild climate and a large urban population in nearby rome our site shows only limited evidence for environmental degradation warm and mild climate during the medieval warm period on the other hand led to widespread deforestation and erosion the ability of the romans to utilize imported resources through an extensive trade network may have allowed for preservation of the environment near the roman capital whereas during medieval time the need to rely on local resources led to environmental degradation cool wet climate during the little ice age led to a breakdown in local land use practices widespread land abandonment and rapid reforestation our results present a high resolution regional case study that explores the effect of climate change on society for an under documented region of europe

geochronological position of badlands and geomorphological patterns in the guadix baza basin se spain abstract the guadix baza basin is one of a number of intramontane depressions located within the betic cordillera se spain where the geological and geomorphological evolution is controlled by tectonic activity the basin ceased to be closed after capture by the atlantic network when five main land systems developed late pleistocene geological evolution basically consisted of erosional modelling when badlands were deeply incised in highly erodible materials marls and silts three travertine platforms and several palaeolithic sites were used to determine that this main incision period fell within a 115 000 48 000 yr range there are few signs of geomorphological evolution of this basin in the last 48 000 yr based on these geomorphological data and soil development tectonic uplift of the basin probably played a secondary role in its evolution and climatic conditions in southern iberia in the 144 000 48 000 yr period were more humid and variable than later

multidisciplinary characterization of the buried travertine body of prima porta central italy abstract a buried travertine deposit identified in a well at prima porta to the north west of rome italy was investigated using a multidisciplinary approach that included stable isotope geochemistry mineralogy petrography and radiometric dating the travertine body is located just along the western boundary of the tiber valley a morpho tectonic depression of extensional origin it is associated with the rise of a deep seated hypothermal saline co2 rich fluid the depositional environment was inferred by the macroscopic features of core and microfacies analysis which suggested that travertine deposition was associated with a low to moderate energy environment such as gently dipping shallow pools on low angle terraced slopes a hydrothermal system characterised by long circulation paths at depth and deeply derived co2 dominated fluids are supported by geochemical analyses according to radiometric dating travertine deposition occurred from between 53 5 10 ka to 24 2 4 7 ka the activation of the travertine depositing spring was probably coeval with the wettest climatic conditions occurring during mis3 whereas the end of deposition coincides with the cold and arid phase of the last glacial maximum

oceanographic conditions in the marginal ice zone north of svalbard in early fall 1979 with an emphasis on mesoscale processes during september october 1979 the norwegian remote sensing experiment was carried out in the marginal ice zone north of svalbard convergence of the ice cover is correlated with along ice edge winds with the ice to the right while divergence occurs during office winds or calm conditions a wind driven ice edge jet is observed wind driven upwelling of the pycnocline of up to 7 m was present along the ice edge during a 10 to 15 m s easterly wind event the upwelling is due to ekman divergence at the ice edge caused by higher wind stress over ice than over open water the ice edge meanders with a scale of 20 40 km and sheds eddies with a scale of 5 to 15 km into the open water this scale is of the same order as the rossby radius of deformation eddies with the same scale are also seen in the conductivity temperature and depth observations conditions during the experiment were such that barotropic instabilities could have generated these eddies

reflection and transmission characteristics at the edge of shore fast sea ice the reflection and transmission of ocean waves at a sea ice boundary is reconsidered the sea ice is modelled as a continuous thin elastic plate of uniform thickness floating on water of arbitrary constant depth unlike earlier solutions matching of potentials between the free surface domain and the ice covered domain is done at all depths previous solutions were incompletely matched as the potentials in each domain were deficient in the present solution a number of the infinity of evanescent modes which were hitherto ignored are included in the solution and allow matching to be carried out by minimization of an integrated error term from surface to seafloor reflection and transmission are found to be markedly influenced by the inclusion of these modes suggesting that conclusions based on the incomplete potentials may be substantially in error

quaternary geomorphological evolution of the tremiti islands puglia italy abstract the archipelago of the tremiti islands situated in the centre of the adriatic sea is considered nationally and internationally a very important geological laboratory in the area of connection between the central and southern apennines already rich in cenozoic stratigraphic structural and seismological data this study discusses structural geomorphologic data with particular attention to features useful to define the islands quaternary evolution the identification of the main morphogenic events is based on the study of landforms that are spatially and chronologically comparable with depositional erosional features of the quaternary continental succession analysis of geomorphology and quaternary continental deposits supported by radiometric dating allows reconstruction of the islands quaternary evolution and provides some contributions at a regional scale

the attenuation rates of ocean waves in the marginal ice zone during field operations in the greenland and bering seas in 1978 1979 and 1983 a number of experiments were carried out in which wave energy was measured along a line of stations running from the open sea deep into an icefield wave buoys in the water and accelerometer packages on floes were the instruments employed with airborne vertical photography to supply information on floe size distribution it was found that the decay of waves is exponential with a decay coefficient which generally increases with frequency except for a roll over at the highest frequencies the observations can be fitted reasonably well to a theory of one dimensional scattering

the use of sar to measure ocean wave dispersion in frazil pancake icefields abstract icefields composed of frazil and pancake ice play important roles in both polar regions in winter during the early to midwinter period pancake ice is a major component of the antarctic sea ice cover while in the arctic the odden ice tongue in the greenland sea associated with deep convection is composed mainly of pancake ice the retrieval of sea ice thickness by remote sensing is in general a very difficult task in this paper the change in dispersion of ocean waves as they penetrate into pancake ice is considered so as to gain insight into its possible relationship with thickness spectral analysis of subscenes from ers 2 second european remote sensing satellite synthetic aperture radar sar images yields the wavelength and direction of the principal spectral component both outside and inside the ice cover there is a decrease of wavelength at the ice edge as well as refraction toward the normal and a loss of amplitude the analysis is complex because the true wave spectrum must be re

temperate and semi arid tufas in the pleistocene to recent fluvial barrage system in the mediterranean area the ruidera lakes natural park central spain abstract the ruidera lakes natural park in central spain contains a well exposed pleistocene to recent freshwater carbonate tufa succession dominated by fluvial barrages and lacustrine deposits the majority of exposed tufas are holocene to recent in age today carbonate accumulation is currently manifested as active phytoherm barrage constructions marginal lacustrine stromatolitic terraces lacustrine lime muds all produced mainly by precipitation and sand size detrital tufa the depositional history of the ruidera park sites has been interpreted from natural outcrops rotary drill and percussion auger cores these reveal a long quaternary record of microbially dominated barrage framework developments and associated lacustrine carbonates these alternate with frost weathering deposits and detrital tufa episodes especially during cooler conditions u series dating of several earlier tufa deposits within the park indicates four distinct episodes of tufa development at 190 250 ka b p 90 130 ka b p 30 40 ka b p and 16 ka b p present the three oldest episodes appear to be related to cyclic tufa building events associated with warm periods of oxygen isotope stages ois 7 5 and 3 growth under present conditions is slow and several barrages have been damaged by human activity and drought events

growth of a pleistocene giant carbonate vein and nearby thermogene travertine deposits at semproniano southern tuscany italy estimate of co2 leakage abstract a giant carbonate vein 50 m thick fissure ridge travertines and nearby travertine plateaus in the semproniano area mt amiata geothermal field southern tuscany italy are investigated through a multidisciplinary approach including field and laboratory geochemical analyses u th geochronology c nd o and sr isotope systematics ree abundances and fluid inclusion microthermometry the main aim of this work is to understand 1 modes and rates for the growth of the giant vein and nearby travertine deposits within a quaternary volcano tectonic domain 2 implications in terms of the co 2 leakage and 3 possible relationships with quaternary paleoclimate and hydrological oscillations results show that the giant vein was the inner portion of a large fissure ridge travertine and grew asymmetrically and ataxially through repeated shallow fluid injections between 650 and 85 ka with growth rates in the 10 2 10 3 mm a order the giant vein developed mainly during warm humid interglacial periods partially overlapping with the growth of nearby travertine plateaus estimated values of co 2 leakage connected with the vein precipitation are between about 5 10 6 and 3 10 7 mol a 1 km 2 approximately representing one millionth of the present global co 2 leakage from volcanic areas temperature estimates obtained from o isotopes and fluid inclusion microthermometry indicate epithermal conditions 90 50 c for the circulating fluid during the giant vein growth with only slight evidence of cooling with time geochemical and isotope data document that the travertine deposits formed mainly during pleistocene warm humid periods within a tectonically controlled convective fluid circuit fed by meteoric infiltration and maintained by the regional geothermal anomaly hosted by the carbonate reservoir of the mt amiata field

feedback between ice flow barotropic flow and baroclinic flow in the presence of bottom topography coupling between externally driven barotropic flow and locally driven baroclinic flow in the presence of an ice cover and topography is studied the topography is a necessary ingredient in this coupling this study shows that the observed mesoscale activity of the ice edge seen in satellite imagery does not necessarily reflect the mesoscale baroclinic activity in the ocean besides oceanic eddies the ice cover can trace the topographic changes via the coupling to the barotropic flow a two layer ocean model coupled to an ice model is constructed to simulate an ice ocean system with a varying bottom topography in the absence of wind forcing the ice cover reflects the externally driven barotropic ocean response especially topographically forced taylor columns by forming ice streamers or meanders some of these features propagate advected with the ocean currents as a whole downstream creating an image of eddy propagation even though there is no baroclinic structure underneath when downwelling favorable winds ice on the left from the wind direction are turned on in addition to this background barotropic flow the ekman flow in the ocean toward the open ocean will enhance the meandering of the ice edge due to the barotropic flow during upwelling favorable winds the ice edge stays rather compact including the case when a strong baroclinic cyclonic vortex is developing beneath an ice meander supported by the taylor column in the ocean

fossil travertine system and its palaeofluid provenance migration and evolution through time example from the geothermal area of acquasanta terme central italy abstract the geothermal area of acquasanta terme has often been studied for its active and fossil travertine deposits to elucidate fluid origin geodynamic and hydrological setting even though present day thermal springs are usually used to obtain most information the three travertine terraces bordering the tronto river contain a plethora of information a combination of elemental and isotope analyses 18o 13c and 87sr 86sr ratio fluid inclusion microthermometry and u th dating is used to verify the hydrogeology and its timing these analyses point out two fluid reservoirs with distinctly different fluids one with low salinity of 0 7 wt nacl eq and another with 28 5 wt nacl eq which corresponds to the fluid composition of present day spring fluids furthermore it is demonstrated that geothermal sources were intermittently active in the past 221 ka mainly during uneven numbered marine isotope stages which are related to humid interglacial periods and resulted in three different travertine terraces around 210 5 126 5 and 36 5 ka accordingly an uplift rate for this area could be estimated at around 1 mm ka the fluids were tapped at a depth of approximately 3 km in the tectonized cataclastic fraction of the triassic anidriti di burano formation the calcare cavernoso formation and are originally meteoric based on geochemical evidence of a uniform 87sr 86sr ratio of 0 707914 0 00019 and a 18oaragonite value of 11 90 0 34 which has been depressed by elevated precipitation temperatures between 22 2 and 50 c the characterization and dating of fossil travertine deposits gives valuable data providing insights in long term fluid flow and orogenic uplift rates adding valuable information to present day spring fluid characterization

upper cretaceous stable carbon isotope stratigraphy of terrestrial organic matter from sakhalin russian far east a proxy for the isotopic composition of paleoatmospheric co2 abstract time stratigraphic patterns of stable carbon isotopic ratios recorded in terrestrial organic matter from cenomanian maastrichtian successions for the russian far east can be correlated to those of carbonate carbon from well studied successions for other parts of the world age indicative biostratigraphy based on regional ammonoids and inoceramid bivalves are well established in japan and can be applied to the whole cretaceous succession except for the upper cenomanian lower turonian and the upper part of the maastrichtian zones lacking macrofossils globally correlative carbon isotopic events previously documented with carbonate carbon from europe and with carbonate carbon and marine organic matter from the u s western interior are recognized with similar magnitude through uppermost cenomanian lower campanian in ascending order these events are positive spike across the cenomanian turonian boundary step like leveled segment followed by negative shift lower middle turonian trough like negative excursion middle upper turonian positive rebound coupled with following broad peak coniacian and positive peak basal campanian followed by modest negative excursion the parallel fluctuation of the 13 c value between the terrestrial organic matter and carbonate suggests carbon isotopic equilibrium between surface seawater and atmospheric co 2 and demonstrates that the isotopic curve of terrestrial organic carbon can be used to monitor carbon isotopic fluctuations of co 2 in the ocean atmosphere system in the upper campanian and maastrichtian a negative 13 c excursion within chron 33r and a following rapid rebound can be correlated with the same distinctive carbon isotopic feature of carbonate observed in the deep sea cores from south and north atlantic the indian and the pacific oceans within this interval the 13 c value of terrestrial organic matter also reflects carbon isotopic fluctuation of the global co 2 reservoir with relatively minor regional local noise

trends in δ18o and δ13c values in lacustrine tufa mounds palaeohydrology of searles lake california four tufa facies have been identified in abundant tufa mounds that accumulated in searles lake california usa during the pleistocene covariance of 18 o and 13 c values within the tufa facies has been analysed and correlated with palaeo lake history this study demonstrates that characteristics of 18 o and 13 c values are different in each of the tufa facies and can be related to palaeo lake stages the first facies of tufa formation p has relatively low average 18 o and 13 c values 18 o 27 and 13 c 12 n 14 these low values are attributed to rapid increases in the lake volume this increase was followed by higher average 18 o and 13 c values of both the nodular n facies 18 o 18 and 13 c 41 n 24 and the columnar c facies 18 o 06 and 13 c 40 n 7 these higher values are interpreted to record a decrease in lake volume due to high evaporation and increased biogenic productivity following formation of facies c the lake was essentially dry during formation of the finely laminated lc facies facies lc formed subaerially as spring water flowed up through the central conduit of the mounds and cascaded down their periphery the relatively high 18 oa nd 13 c values for this facies 18 o 14 and 13 c 44 n 12 are due to evaporation and fast co2 degassing although covariant trends are well displayed variations in lake chemistry alter some of these trends due to periods of hyper alkalinity this study confirms the utility of stable isotopic analyses of lacustrine tufa facies to determine palaeo lake history

an ice water vortex at the edge of the east greenland current during the y mer 80 cruise in august 1980 we observed an ice feature of 60 km diameter having the shape of a breaking wave it lay at the edge of the east greenland drift ice in fram strait with its center at 79 15 n 00 38 e and the wave was breaking upstream relative to the east greenland current two conductivity temperature and depth sections across the feature in n s and e w directions revealed warm up to 4 3 c water some 60 km inside the polar front in lenses centered at 40 m depth but with an effect to beyond 600 m the temperature anomalies were accompanied by salinity anomalies so that there was little net effect on the density profile the form of the sections together with the ice distribution observed by vertical photography from a helicopter and surface motion observed by tracking four radar transponders all suggest that the feature is a vortex produced by an instability in the polar front it has similar characteristics to vortices investigated experimentally and theoretically by griffiths and linden 1981a b 1982 and observationally by wadhams et al 1979

overview of limex 87 ice observations ice observations results and conclusions are summarized for the march 1987 labrador ice margin experiment limex 87 an international oceanographic study conducted in the pack ice of the grand banks area off the coast of newfoundland included are the ice extent flow size and thickness ice kinematics and rheology ice microwave properties oceanic properties under the ice and penetration of swell into the ice

the quaternary travertine deposits of europe and asia minor abstract a summary is provided of the published information relating to all aspects of quaternary travertine formation in europe west of the ural mountains the deposits have been divided into two broad groups the meteogene travertines which result primarily from the degassing of soil borne aqueous co 2 and thermogene deposits resulting from the degassing of thermally generated co 2 meteogene deposits are rare above latitude 58 n and in regions where the mean annual air temperature is below 5 c a significant positive correlation exists between mean air temperature and travertine deposit thickness the combined effects of temperature and rainfall are used to provide a zoned map showing the travertine forming potential of limestones within the region information from 14 c dating indicates that deposition reached a maximum in the period 5 10 ka bp and is currently limited by land and water management practices in the populated areas thermogene deposits occur in regions of high co 2 discharge resulting from tectonic activity such as italy and turkey where there is much vulcanism these travertines are frequently more massive and less readily weathered than meteogene deposits fully referenced information is provided for 320 important mostly well studied sites 227 meteogene 93 thermogene of which 156 are currently active

upper cretaceous stable carbon isotope stratigraphy of terrestrial organic matter from sakhalin russian far east a proxy for the isotopic composition of paleoatmospheric co2 by t hasegawa et al discussion abstract hasegawa t pratt l m maeda h shigeta y okamoto t kase t uemura k 2003 upper cretaceous stable carbon isotope stratigraphy of terrestrial organic matter from sakhalin russian far east a proxy for the isotopic composition of paleoatmospheric co2 palaeogeogr palaeoclimatol palaeocol 189 97 115 present highly interesting patterns in stable carbon isotopic ratios based on terrestrial organic matter from cenomanian maastrichtian successions in sakhalin island and try to match these with carbonate carbon curves from other parts of the world although we agree that this approach is useful and do not doubt their methods or isotopic fluctuation results we worry about the lack of any detailed stratigraphic scheme in the paper our main arguments 1 hasegawa et al do not show cenomanian turonian stage boundary positions in the naiba section precisely and as a result it seems that the positive spike shown at this boundary might not equate with this level but relate to the upper of two cenomanian spikes established in japan 2 the definition of turonian coniacian boundary is also imprecise and it is difficult to understand at what level in the naiba section they place this boundary as a result it seems that the positive spike which has been shown near the middle of the coniacian could correspond to the t c boundary 3 the imprecise interpretation of the campanian maastrichtian boundary also causes the assumption that the negative spike which hasegawa et al equate with the c m boundary could be correspond to middle of upper maastrichtian in the naiba section

are current models of tufa sedimentary environments applicable to tropical systems a case study from the gregory river abstract tufa formation in the gregory river tropical northern australia is strongly influenced by high evaporation rates perennially warm water temperatures construction behaviour of aquatic insect larvae and regular high magnitude floods these conditions contrast with those of the cool temperate tufa depositing streams for which sedimentary models have already been developed gregory river tufas occur as multiple series of dams separated by waterholes indicating that under all climatic conditions there is a persistence of hydraulic factors in controlling the dam pool sequence in fluvial tufa systems however at the scale of individual tufa deposits and facies the gregory river system displays a deviation away from current models tufa domes upstream dipping ramps calcite rafts and larval facies are all common and important features in both modern and fossil tufas of the gregory river but they are not included in current tufa models thus specific sedimentary models need to be developed for seasonally humid tropical tufa systems to understand their formation and interpret them correctly in the rock record

the taravilla lake and tufa deposits central iberian range spain as palaeohydrological and palaeoclimatic indicators 21 pages 8 figures 3 tables available online oct 13 2007 issue title lake systems sedimentary archives of climate change and tectonics egu general assembly

a mechanism for the formation of ice edge bands we propose a mechanism for the formation of multiple bands at an ice edge that is subjected to an off ice wind the wind moves the outermost floes seaward faster than the interior ice dilating the marginal ice zone and opening up random polynyas in the largest of the polynyas the off ice wind generates a significant fetch limited wave spectrum which produces a wave radiation pressure on floes at the downwind end of the polynya increasing their velocity they are herded against their downwind neighbors creating a band of high ice concentration the band is stabilized by an internal compacting stress due to the exponential decay of the wind wave spectrum across the band and to a slower decay of swell incident from seaward the band s growth terminates when it encounters a second downwind polynya of sufficiently large size we show how an array of immature bands generated in this way matures by selective mergers into larger regularly spaced bands of approximately equal width

interaction between regional and local tectonic forcing along a complex quaternary extensional basin upper tiber valley northern apennines italy abstract in extending areas undergoing regional tectonic uplift the persistence of subsidence at a normal fault hanging wall depends on the competition between regional and local tectonic effects when regional uplift exceeds the subsidence of the hanging wall block denudation prevails at both the hanging wall and the foot wall when local tectonic subsidence exceeds regional uplift sedimentation occurs over the hanging wall block supplied by foot wall erosion we analyzed a pliocene quaternary continental basin currently crossed by the tiber river in italy the tectono sedimentary evolution of the basin developed at the hanging wall of a regional low angle extensional detachment the alto tiberina fault in the axial region of the northern apennines of italy this area is affected by regional uplift on the order of 0 5 1 0 mm yr the present day activity of the fault is revealed by both microseismicity and geodetic gps data we investigated the mid 10 100 ka and long term 0 5 3 0 ma evolution of the three depocenters by studying the continental pleistocene succession infilling the basin as well as fluvial terraces and higher paleosurfaces carved into the pleistocene deposits by using surficial geologic data and an interpretation of a set of seismic reflection profiles we show that the three depocenters experienced a fairly similar evolution during the pliocene early pleistocene when a 1000 m thick continental succession was deposited on the contrary geomorphological observations indicate that at the beginning of the middle pleistocene a switch occurred in the evolution of the three depocenters in the northernmost sansepolcro sub basin bounding normal faults are active and hanging wall subsidence outpaces regional uplift concurrently in the umbertide and ponte pattoli sub basins uplift dominates over the hanging wall subsidence promoting river incision and exhumation of the pleistocene deposits for these two depocenters by means of terrace river correlations we estimate that the incision rate is 0 3 0 35 mm yr suggesting a maximum tectonic subsidence of 0 2 mm yr the identification of a heterogeneous uplift pattern along the hanging wall of the alto tiberina fault driven by different displacement rates of its fault splays allowed us to characterize fault segments with different activities and possibly different seismic behaviors

upwelling at the ice edge a mechanism for deep water formation this study sets forward a hypothesis which anticipates deep water formation due to ice edge upwelling the upwelling can raise thermocline waters the lower arctic intermediate water to the surface or near it where the water is exposed to cooling evaporation mixing and oxygenation thus upwelling can act as a preconditioning mechanism for deep convection the conjecture would also explain the salinity range of the greenland sea deep water if the upper and lower arctic intermediate water masses are mixed so that the latter has at least an 80 contribution also the convection events induced by ice edge upwelling during winter season we anticipate could give rise to a new deep water annual production rate consistent with observations

multidisciplinary approach for palaeoclimatic signals of the non marine carbonates the case of the sarikavak tufa deposits afyon sw turkey abstract non marine carbonates such as travertine tufa and speleothem are quite sensitive for climatic fluctuations this study presents the new dating and the first pollen records from afyon sarikavak tufas sw turkey together with lithofacies descriptions geochemical and petrographic results obtained from drilling cores sl 2 sl 6 and sl 7 the data extensively provides insight into palaeoenvironmental and palaeoclimatic changes during the middle late pleistocene period according to core samples these fluvial tufa occurrences formed in high gradient and stepped fluvial conditions have been defined as barrage dammed and terraced slope systems in the investigated area the depositional lithofacies are moss tufa included macrophytes bryophytes and vertical stems phytoclastic tufa peloidal tufa micritic tufa microbial tufa intraclastic tufa extra formational tufa lime muddy clay and paleosol level in respectively the new u th radiometric dating and stable isotopes are evaluated together with previously published results in regard to new radiometric data tufa deposits occurred predominantly during the marine isotopic stages at 313 3 21 mis 9 295 8 63 mis 8 9 230 8 42 mis 7d e 228 8 12 mis 7d 215 7 17 mis 7c and 188 2 16 mis 6 7a ka respectively the climatic changes occurring between glacial and interglacial periods such as during the middle late pleistocene might probably influenced the precipitation of tufas in the area in addition the less negative and the more positive carbon isotopic values between 0 8 and 1 3 v pdb could be related to the progressive downstream co2 degassing from host rocks enhanced by high velocity current conditions changes in the soil co2 contribution and photosynthesis the changes of 18o values between 8 3 and 10 1 v pdb are most probably related to variable effects of evaporation in depositional environment palynofloral data gives important clues about the paleovegetation and paleoclimate of the region this field survey has been conducted the first time in this area both carbon values and palynological findings show that drought conditions were dominantly present in the pleistocene period but in some processes drought conditions decreased depending on the amount of rainfall the increasing amount of gymnosperm pollens is more likely to appear in more humid conditions due to the decreasing of drought condition in this time interval

a coupled ice ocean model of upwelling in the marginal ice zone a dynamical coupled ice ocean numerical model for the marginal ice zone miz is suggested and used to study upwelling dynamics in the miz the nonlinear sea ice model has a variable ice concentration and includes internal ice stress the model is forced by stresses on the air ocean and air ice surfaces the main coupling between the ice and the ocean is in the form of an interfacial stress on the ice ocean interface the ocean model is a linear reduced gravity model the wind stress exerted by the atmosphere on the ocean is proportional to the fraction of open water while the interfacial stress ice ocean is proportional to the concentration of ice a new mechanism for ice edge upwelling is suggested based on a geostrophic equilibrium solution for the sea ice medium the upwelling reported in previous models invoking a stationary ice cover is shown to be replaced by a weak downwelling due to the ice motion most of the upwelling dynamics can be understood by analysis of the divergence of the across ice edge upper ocean transport on the basis of numerical model an analytical model is suggested that reproduces most of the upwelling dynamics of the more complex numerical model

interglacial growth of tufa in croatia tufa samples from the krka river area in croatia were dated by 14c and 230th 234u methods the study area is situated in the karst region of the southern dinarides 14c ages of 40 tufa samples collected at the waterfalls coincide with the early holocene interglaciation up to 6000 14c yr b p comparison of conventional 14c dates of holocene tufa and those of speleothems in the dinaric karst shows that speleothem formation started several thousand years earlier than tufa growth samples of old tufa deposits from the krka river 17 and plitvice lakes 12 area and speleothem samples from caves in dinaric karst 5 yield 34 230th 234u dates most of which cluster around interglacial marine 18o stage 5 21 eight of 13 older dates belong to interglacial stages 7 and 9 only 5 dates fall within stage 6 and 8 glaciations 230th 234u dates of speleothems and tufa samples from central europe have indicated that these were formed preferentially during warm and humid interglacial and interstadial periods and it appears that this is true of southern croatia as well stable isotope 13c 18o analyses of 40 tufa samples from the krka river area were compared with stable isotope analyses of tufa from the plitvice lakes area the 13c values for both locations are similar and range from 10 to 6 indicating similar conditions of tufa formation a systematic difference between the 18o values of tufa in these two areas reflects the regional distribution of the oxygen composition of precipitation

δ13c δ18o and deposition rate of tufa in xiangshui river sw china implications for land cover change caused by climate and human impact during the late holocene

calcium isotopic fractionation during travertine deposition under different hydrodynamic conditions examples from baishuitai yunnan sw china abstract revealing the potential of ca isotopes in the research of travertine formation processes is the principal goal of this study to achieve this the hydrochemistry travertine precipitation rates and variations in ca isotopic compositions 44 40 ca of present day endogenic thermogenic travertine in two different hydrodynamic systems canal and pool are studied at baishuitai yunnan sw china in the canal where the travertine precipitation is faster 44 40 ca values of both solution and travertine show a downstream increase with ca isotopic fractionation 44 40 ca caco3 aq equal to 1 6 compared to the canal ca isotopic fractionation between travertine and aqueous ca 2 is smaller 44 40 ca caco3 aq 1 2 in the pools where travertine precipitation rates are lower the spatial variations in 44 40 ca values of solution and travertine are related to the amount of ca removed from the solution when 44 40 ca values of spring water remain stable in addition the results confirm the control of precipitation rates on ca isotopic fractionation between calcite and parent aqueous ca 2 using natural samples the observed negative correlation between 44 40 ca caco3 aq and travertine precipitation rates can be explained by the steady state kinetic surface reaction model proposed by depaolo 2011 with equilibrium and kinetic fractionation factors of eq 1 0000 0 0001 and f 0 9983 0 0002 respectively an important consequence of this study is that ca isotopes in travertine systems are good tools to have access to variations of 44 40 ca aq which are directly linked to the amount of precipitated ca this could then be useful for reconstructing past hydrodynamic conditions when applied to travertine core data

evaluating the geogenic co2 flux from geothermal areas by analysing quaternary travertine masses new data from western central italy and review of previous co2 flux data abstract quantification of carbon fluxes between solid earth and its atmosphere is necessary to understand the global geological carbon cycle some of the main co2 contributors are metamorphism and magmatic mantle degassing co2 is discharged from active and quiescent volcanoes fault zones geothermal systems and co2 rich groundwater here a new method for the estimation of the geogenic flux of co2 from tectonically active regions based on the volume composition and age of travertine deposits is proposed the method is applied to the travertine deposits of western central italy where travertine deposition is driven by degassing of co2 charged groundwater results show that the study areas are characterized since middle pleistocene by diffuse co2 degassing processes with time averaged co2 fluxes ranging between 1 24 0 12 106 mol y 1 km 2 and 1 38 0 42 106 mol y 1 km 2 these values are of the same order of magnitude of carbon dioxide fluxes measured by different methods in western central italy and are higher than the global baseline co2 flux from high heat flow regions the review of the available 234u 230th and 14c data shows that the co2 degassing processes that affects western central italy nowadays were already active at least 350 ka ago proving that this region is a globally relevant case for the study of earth degassing considering the widespread occurrence of travertine deposits in tectonically active areas worldwide the proposed approach can be used as a reliable tool to estimate the co2 flux in different geodynamic settings within system earth

pleistocene calcareous tufa from the ellera basin umbria central italy as a key for an integrated paleoenvironmental and tectonic reconstruction abstract continental carbonates calcareous tufa and associated deposits represent a natural archive of paleoenvironmental and tectonic information that can be fully disclosed only by the application of a multidisciplinary approach the aim of this paper is to describe the geological features of the ellera basin umbria central italy by integrating physical stratigraphy sedimentology geochemistry tectonics and biological paleontology palynology data the study of the ellera basin represents a starting point for the improvement of a methodology that could be applied to similar sedimentary systems regardless of their actual location extension and age two stratigraphic units were recognized in the ellera basin both characterized by multiple events of calcareous tufa deposition during the pleistocene in the lower san biagio unit the concurrent finding of hippopotamus h antiquus and leptobos remains associated with late villafranchian molluscs suggests an attribution to the early pleistocene tasso or farneta faunal unit about 1 8 1 5 ma both sedimentological and paleontological data indicate a periodically flooded alluvial plain depositional environment and isotopic values of 13c and 18o register the establishment of a wet paleoclimate the overlying santa sabina unit lies with an angular unconformity on the san biagio unit and was dated to 115 000 8000 years by the application of the u th method the age of the santa sabina unit falls within a period of warm and humid climate mis 5d e and paleoclimatic inferences are supported by the isotopic record 13c and 18o the unit deposited in a well vegetated fluvio lacustrine and fluvio palustrine environment locally dominated by herbaceous taxa as revealed by palynological analysis despite the 1 5 ma time lag between the two units their depositional evolution shared the presence of calcareous tufa whose deposition was controlled by similar paleoenvironmental and paleoclimatic conditions hot and humid interglacial conditions with high rainfalls characterized both periods as well as by the local tectonic setting and activity in both units the maximum thickness abundance of the calcareous tufa occurs at the intersection between two regional tectonic lineaments controlling both the basin subsidence and the ascent of co2 rich water

speleothems travertines and paleoclimates abstract age data for about 660 speleothems and about 140 spring deposited travertines were collected including many unpublished results these data were plotted as histograms and also as error weighted frequency curves on a 350 000 yr scale these plots clearly show periods of increased speleothem travertine growth as well as times of cessation the periods of most frequent speleothem growth were between approximately 130 000 and 90 000 yr ago and since about 15 000 yr ago such periods before 150 000 yr ago however cannot be yet recognized because of a lack of sufficient data and the associated uncertainties of dates in this age range a comparison with the oxygen isotope record of deep sea core v28 238 shows a clear relationship indicating that terrestrial calcite formation is controlled by paleoclimatic fluctuations the evident climatic stimulation of quaternary calcite formation is readily explained geochemically and is substantiated by the obvious difference in speleothem travertine growth as a function of geographic position

geophysical and oceanographic information in the marginal ice zone from ocean wave measurements consequent to recent experiments in marginal ice zones miz advances in remote sensing and theoretical progress studies have been published which invoke wave ice interactions to explain or predict certain geophysical phenomena while admirable and desirable in principle these works are based on a refutable surface boundary condition intended for a sheet or plate of solid ice rather than a medium made up of individual ice floes a case is argued for prudence as derived results may originate entirely from the application of an inappropriate miz model

wave effects on ocean ice interaction in the marginal ice zone the effects of wave train on ice ocean interaction in the marginal ice zone are studied through numerical modeling a coupled two dimensional ice ocean model has been developed to include wave effects and wind stress for the predictions of ice edge dynamics the sea ice model is coupled to the reduced gravity ocean model through interfacial stresses the main dynamic balance in the ice momentum is between water ice stress wind stress and wave radiation stresses by considering the exchange of momentum between waves and ice pack through radiation stress for decaying waves a parametric study of the effects of wave stress and wind stress on ice edge dynamics has been performed the numerical results show significant effects from wave action the ice edge is sharper and ice edge meanders form in the marginal ice zone owing to forcing by wave action and refraction of swell system after a couple of days upwelling at the ice edge and eddy formation can be enhanced by the nonlinear effects of wave action wave action sharpens the ice edge and can produce ice meandering which enhances local ekman pumping and pycnocline anomalies the resulting ice concentration pycnocline changes and flow velocity field are shown to be consistent with previous observations

large tufa mounds searles lake california mounds that have formed around spring vents occur in a variety of environmental settings many at sites generally difficult or inaccessible for sampling in contrast over 500 tufa mounds occur in the dry bed of searles lake california the mounds range from minor features to 45 m in height most are 5 to 12 m high these mounds composed of calcite and aragonite formed associated with spring vents in the pleistocene lake bottom thus analyses of these mounds in searles lake provide a model with regard to the origin and architecture of tufa mounds the mounds consist of four distinctive tufa facies the initial deposits consist of porous tufa including the innermost porous 1 and the outermost porous 2 deposits followed by nodular tufa then columnar tufa and laminated crusts there are two simple sequences of tufa deposition the first sequence is from porous 1 to nodular to laminated crusts and finally to porous 2 a second sequence consists of porous 1 to columnar to laminated crusts and lastly to porous 2 facies changes are a response to changes in environmental conditions from deep water porous 1 facies to an essentially dry lake phase during and after the formation of laminated crusts facies to deep water porous 2 facies and at the present time totally dry the primary constituents that comprise the tufa deposits include thin laminae pisoids spherulites peloids and stromatolite like crusts on the microscopic scale these constituents dominantly make up nano spheres micro rods and rod like crystals as well as other calcified bodies these constituents are interpreted to be the calcified remains of bacterial bodies these findings suggest that microbial participation in the construct of other mounds should be a major concern of investigation both for terrestrial and extraterrestrial spring fed mounds

the upper quaternary sedimentary sequence at the rieti basin central italy a record of sedimentation response to climatic changes abstract lithostratigraphy chronology and depositional environments of sixteen holocene alluvial fill sediment cores from the southern part of the conca of rieti central italy was established by sedimentological palaeontological and 14 c analyses the study area experienced a lacustrine or palustrine conditions and the water level was effectively controlled by a natural damming of the valley due to intermitted travertine deposition at le marmore site apart from cores s10 s13 s14 and s8 which at their bottom cored sediments referable to upper pliocene and middle pleistocene which are not the object of this paper as a rule the drilled sediments can be referred bottom to top to the following four episodes interval a corresponding to freshwater lacustrine palustrine environment affected by alluvial fan progradations from the edges of the valley and active by middle late pleistocene to early holocene in this interval several hiatuses are supposed but are not evidenced by the bad state of preservation of the sediment cores interval b from 361 to 371 376 m a s l recording a decrease of the water level bracketed between the 14 c ages of 6000 and 2700 yr b p which produced the formation of distinct shallow ponds bogs rich in aquatic vegetation interval c from 381 to 384 m a s l indicating a further rise of the water level recorded by sediments containing abundant molluscs and ostracods interval d the upper part of the cores records an almost continuous drying up the area as shown by abundant hydrophilic land molluscs and interval e the top of all sediment cores representing the present day soil it has been found that the water level fluctuations occurring in the ancient conca are chronologically consistent with the postglacial climate pattern it is further noticed that the episodes of water highstand correspond to the boreal atlantic and subatlantic climatic ameliorations respectively and that the water level dropped during the global cooling episodes recurred from ca 6000 to 2100 yr b p the resulting palaeoenvironmental history agrees with that previously reported for the northern reach of the conca of rieti thus suggesting a common setting for the whole area

age dating and the orbital theory of the ice ages development of a high resolution 0 to 300 000 year chronostratigraphy using the concept of orbital tuning a continuous high resolution deep sea chronostratigraphy has been developed spanning the last 300 000 yr the chronology is developed using a stacked oxygen isotope stratigraphy and four different orbital tuning approaches each of which is based upon a different assumption concerning the response of the orbital signal recorded in the data each approach yields a separate chronology the error measured by the standard deviation about the average of these four results which represents the best chronology has an average magnitude of only 2500 yr this small value indicates that the chronology produced is insensitive to the specific orbital tuning technique used excellent convergence between chronologies developed using each of five different paleoclimatological indicators from a single core is also obtained the resultant chronology is also insensitive to the specific indicator used the error associated with each tuning approach is estimated independently and propagated through to the average result the resulting error estimate is independent of that associated with the degree of convergence and has an average magnitude of 3500 yr in excellent agreement with the 2500 yr estimate transfer of the final chronology to the stacked record leads to an estimated error of 1500 yr thus the final chronology has an average error of 5000 yr