climatic change on the iberian peninsula recorded in a 30 000 yr pollen record from lake banyoles the banyoles lacustrine sequence shows that the vegetational history of the northeastern iberian peninsula during the last 30 000 yr follows the north atlantic pattern of climatic oscillations the banyoles pollen diagram supported by two calibrated 14c dates and nine u th dates shows a clear interstadial event between 30 000 and 27 000 yr b p a pleniglacial period with minor oscillations that ended abruptly ca 14 420 410 yr b p and a late glacial sequence that records the classical stages described in northern europe the bolling allerod interstade the younger dryas event at 12 000 yr b p u series age and a short warming phase between the younger dryas and the last cold event dated at 11 000 yr b p u series age

the holocene and upper pleistocene pollen record from padul granada spain a new study two borings were made at the site of padul granada pollen analysis of 200 spectra from two successive sequences 14 8 and 8 m deep enables a description of the vegetational and climatic history of this region the most southern one in europe from early wurmian times the chronology is supported by twenty one 14c dates original equivalents are found for the great european prewurm interstadials a markedly arid though thermically not extreme episode exactly equivalent to stage 4 of the marine isotopic stratigraphy closes this relatively temperate period the middle part of the last glacial shows climatic fluctuations that are poorly characterized as is often the case in europe for this period a long section very probably corresponding to the complete last pleniglacial does not show any climatic amelioration towards 15 000 yr b p a change in the diagram is noted that can only be interpreted as reflecting a larger expansion of a regional steppe cover this event also reported on three occasions in southeast france marks the beginning of the oldest dryas the climatic amelioration of ca 13 000 yr b p is far more pronounced here than anywhere else in europe whereas that at 10 000 yr b p is not so clearly marked this unexpected result may be accounted for by the fact that padul is the first continental site so far south and so near pleniglacial refuges to be known on the other hand this result is consistent with what is known from oceanic isotopic stratigraphy a quite new late glacial and holocene vegetational history is revealed characterized by the early appearance and dominance of quercus ilex oak forests of a southern type and the early occurrence of quercus suber and olea it is the first account of a complete history of the postglacial reafforestation in a region with a modern semi arid mediterranean climate from the palaeoclimatic point of view it shows that the hot and humid holocene optimum was attained slightly before 8000 yr b p and that the holocene climatic fluctuations were of but small amplitude

current variability on a narrow shelf with large ambient vorticity signals respectively and with corresponding phase speeds of 0 85 and 1 7 m s 1 the phase trend in east west direction of the 10 hour signal is consistent with unstable growing waves the 10 and 27 hour signals appear dominantly barotropic near the coast out to depths of at least 50 m but the 10 hour signal displayed a 180 phase change between surface and bottom farther away from the shelf break at 160 m depth the two dominant signals cannot be attributed to barotropic instability index terms 4219 oceanography general continental shelf processes 4520 oceanography physical eddies and mesoscale processes 4572 oceanography physical upper ocean processes keywords shelf circulation florida current vorticity flow instability surface doppler radar

small scale secondary caco3 accumulations in selected sections of the european loess belt morphological forms and potential for paleoenvironmental reconstruction eighteen important quaternary loess paleosoil sites have been studied across the european loess belt they included approximately 50 buried soils the over and or underlying loess and the present day surface soils where possible from the numerous types of secondary caco3 accumulations recognized only the small scale accumulations are discussed in this paper including calcified root cells caco3 hypocoatings needle fiber calcite powdery calcite coatings earthworm biospheroliths and calcite pseudomorphs on gypsum most of the features studied are found in the rhizosphere microecosystem each of these features showed a unique relationship with organic matter micro organism and plant distribution moisture and leaching processes for example the exceptional abundance of calcified root cells is an indicator of a long stability of soil surface during favorable climatic conditions needle fiber calcite is related to biomineralization of saprophytes in soils with sufficient moisture and decomposing organic matter the presence of powdery calcite coatings covering clay and mn coatings in non calcareous soils indicates a change from leaching to non leaching soil moisture regimes earthworm biospheroids provide arguments for a relative stability of the soil surface without rapid burial processes or drastic prolonged water stress finally gypsum pseudomorphs are indicators of changes in local climatic parameters in addition to a discussion of the genesis and the dynamics of the various accumulations several examples are given to show how these accumulations can be used as indicators of a changing environment such as renewed loess deposition the extent of drought or varying intensity of leaching during the year to conclude various forms of small scale secondary caco3 accumulations are common in the loess paleosoils and each type has the potential to contribute to a better understanding of the evolution of the paleoenvironment therefore it is proposed that their individual presence or absence throughout the pedostratigraphical levels and throughout the paleo topography should be recorded at all scales of observation

stochastic boundary conditions for coastal flow modeling 1 recent high resolution radar data of surface velocity between the florida current and the coast allow us for the first time to deduce coastal boundary conditions for ocean models based on observations a stochastic model is found to be a better choice for simulating properties of the observed vorticity than a model with deterministic boundary conditions a stochastic model parameterizing boundary conditions is developed and embedded in a simple quasigeostrophic ocean model comparison of numerical simulations of western boundary flow with stochastic boundary conditions against simulations with traditional no slip and free slip conditions reveals significant differences in the formation of coherent mesoscale structures and the energetics of the western boundary current coherent structures such as dipoles and submesoscale vortices can be generated using stochastic boundary conditions the boundary current variability becomes more energetic and episodic than quasi periodic circulation features in the simulations using the conventional boundary conditions

the average distribution of volume transport and potential vorticity with temperature at three sections across the gulf stream abstract average cross sections of downstream velocity and temperature obtained using pegasus current profiles at three locations along the gulf stream have been partitioned into 2 5 c temperature intervals to examine the distribution of transport increase versus temperature between the two southern sections 27 and 29 n and off cape hatters 73 w between 27 and 29 n the total transport of the florida current over the sections increased only by about 3 106 m3 s 1 3 sv but the current broadens by about 50 by cape hatteras the transport has increased nearly three fold to 93 7 sv of which two thirds of the increase is contained in the 19 5 17 0 c 18 layer and in water colder than the 7 c still temperature found at 27 n cross stream distributions of layer transport potential vorticity and thickness are estimated at each section the 10 10 7 m 1 s 1 contour tends to be a boundary independent of temperature between the region of relatively uniform layer potential vorticity on the a

direct dating of the oxygen isotope record of the last deglaciation by 14c accelerator mass spectrometry major trends of quaternary global climate are reflected in the continental ice volume changes which have been reconstructed by oxygen isotope analysis1 2 18o records from deep sea sediments show that the net glacial build up occurs relatively slowly3 but that the end of an ice age occurs quickly in less than 10 000 yr implying a nonlinear response4 5 to simple milankovitch theory6 the latter observation suggests that the cause of the most recent deglaciation was the maximum in summer calorific radiation at the upper latitudes of the northern hemisphere centred around 11 000 yr ago a view supported by early studies7 later work has produced conflicting dates the main source of confusion being problems with obtaining accurate and reliable dates here by using accelerator mass spectrometry we have measured 14c for various species of foraminifera to produce a reliable timescale for the oxygen isotope record our results show that at the end of the last ice age continental ice sheets began to melt more than 4 000 yr before the northern hemisphere maximum of summer calorific radiation

exceptional preservation of marine diatoms in upper albian amber late albian amber from charente maritime southwestern france contains the first known marine diatoms preserved in a fossil resin approximately 70 inclusions were assignable to the genera basilicostephanus coscinodiscus hemiaulus melosira paralia skeletonema stephanopyxis trochosira aulacoseira and to the order rhizosoleniales some of them are represented by several species this diatom assemblage is mainly composed of colonial planktonic genera which are typical for coastal shallow waters the newly found amber inclusions extend the fossil record of four genera and one order from the late cretaceous and support certain molecular phylogenetic assumptions regarding the diversifi cation of marine diatoms in the early cretaceous the unusual introduction of diatom shells from the beach or sea by wind spray or high tide onto the resin fl ows was possible because the amber forest grew close to the seashore

70 ma nonmarine diatoms from northern mexico carbonaceous cherts of the tarahumara formation exposed near huepac sonora mexico contain abundant diatom frustules occurring as benthic filamentous colonies stratigraphic and paleontological observations indicate that tarahumara sediments accumulated in a nonmarine setting radiometric ages on encompassing volcanic rocks delimit their depositional age to ca 70 ma tarahumara fossils therefore extend the paleontological record of nonmarine diatoms from middle eocene to late cretaceous preserved populations include forms similar to species of the extant genera amphora and melosira as well as filament forming araphid pennates comparable to species of fragilaria and tabellaria tarahumara fossils indicate that by 70 ma nonmarine diatoms had achieved considerable environmental as well as taxonomic diversity

soil forming processes of ancient man made soils cultural layers by the example of sites in humid dunino and arid ar dolong regions of russia a first approach abstract the specificity of cultural layer transformation by soil forming processes was examined in humid moscow region and arid kalmykia zones of russia the objects studied in the two regions are the dunino and ar dolong settlements the former is attributed to the early iron age and the latter to the bronze age archaeological excavations in both places revealed numerous ancient artifacts occurring in situ which prove the sites having been inhabited in the past though located in different natural zones the investigated objects have two features in common sandy parent material and the leading role of the anthropogenic factor in the past morphological examination was supplemented with analysis of chemical properties organic and inorganic matter total phosphorus ph at the arid site humic acids extracted from the organic matter in the ancient cultural layer have been dated by radiocarbon simultaneously the background soils were also studied though both ancient settlements were abandoned for a long time the cultural layers have not been buried under later sediments they stayed exposed and subjected to transformations by soil forming processes the duration of the latter was different at the two sites not exceeding 2 ky in the humid zone and about 3 0 3 5 ky in the arid zone after people had left the settlements younger soils developed in the course of pedogenesis their morphology being similar to the zonal soils integrated analyses of soils enable determination of how far the natural processes have gone in the cultural layer transformation the determination of the total phosphorous provides a means for cultural layer diagnosis with confidence long after the settlement had been abandoned it is possible to determine the trends for human made soil development in different climate zones from arenosol to podzol and arenosol to andosol in humid and arid zones respectively in the course of time the cultural layers of ancient settlements are being transformed into zonal soils no matter the geographical location of the region however the rate of transformation both of individual soil features and of the entire soil profiles is variable transformation rate of ancient non buried cultural layers is higher in the humid environment than in the arid environment

needle fiber calcite a critical review and a proposed classification abstract from a review of the recent literature and our own observations the different morphologies of needle fiber calcite are classified they can be characterized as monocrystalline rods with or without serrated edges or as polycrystalline chains the simplest monocrystalline habit of needle fiber calcite is the individual micro rod m larger monocrystalline rods ma exist in multiples of two more complex forms are found as paired monocrystalline rods with serrated plates along their length mb this group includes three habits which can be distinguished by the number of plates and their orientation relative to the rod finally there is a monocrystalline form mab intermediate between the categories ma and mb which shows the transition from the simple coupled rods to rods with errated plates although polycrystalline needles p have rarely been reported in the literature three types of morphologies have been identified each type of crystal has a specific origin the m micro rods are physicochemical nuclei or calcified bacteria they do not seem to evolve towards larger or more complex morphologies the ma rods are related to biomineralization inside the fungal sheaths the mb rods postdate liberation of ma rods from mycelian bundles the serrated plates are secondary syntactic crystallizations of physicochemical origin whose growth can be inhibited for various reasons the origin of p chains is less well understood but they seem to be physicochemical crystallizations related to evaporation and desiccation therefore these three groups m ma mb and p have similar morphologies but do not seem to be related genetically the only known link is between the ma and mb rods there is no evolutionary s quence of needle fiber calcite habits but a convergence of forms between crystals whose origins are different and independent structures described in the literature as convoluted random cutane and nest like are the result of either evolution of the mycelian bundles or movement of material and organisms in the soil in the case of m micro rods the microfabric is related to the random precipitation around nuclei in pores filled with a highly supersaturated solution initially the p chains also precipitate without preferential organization and later on the growth seems to preferentially constitute chains although the mechanisms are still not understood moreover needle fiber calcites do not indicate a particular climatic environment

dynamic boundary conditions revisited abstract the applicability of the super slip boundary condition in wind driven quasigeostrophic ocean circulation models is reexamined the energy and enstrophy characteristics of the super slip condition are discussed for the equilibrium state a model is constructed with super slip on the western boundary and free slip on the other boundaries both linear and nonlinear solutions are presented compared to the case with all free slip boundaries this new model gives a more energetic and narrower western boundary current but otherwise the differences are not very great

evaluating the use of amber in palaeoatmospheric reconstructions the carbon isotope variability of modern and cretaceous conifer resins abstract stable carbon isotope geochemistry of fossilized tree resin amber potentially could be a very useful tool to infer the composition of past atmospheres to test the reliability of amber as a proxy for the atmosphere we studied the variability of modern resin 13 c at both local and global scales an amber 13 c curve was then built for the cretaceous a period of abundant resin production and interpreted in light of data from modern resins our data show that hardening changes the pristine 13 c value by causing a 13 c depletion in solid resin when compared to fresh liquid viscous resin probably due to the loss of 13 c enriched volatiles modern resin 13 c values vary as a function of physiological and environmental parameters in ways that are similar to those described for leaves and wood resin 13 c varies between plant species and localities within the same tree and between different plant tissues by up to 6 and in general increases with increasing altitudes of the plant growing site we show that as is the case with modern resin cretaceous amber 13 c has a high variability generally higher than that of other fossil material despite the high natural variability amber shows a negative 2 5 3 13 c trend from the middle early cretaceous to the maastrichtian that parallels published terrestrial 13 c records this trend mirrors changes in the atmospheric 13 c calculated from the 13 c and 18 o of benthic foraminiferal tests although the magnitude of the shift is larger in plant material than in the atmosphere increasing mean annual precipitation and p o 2 could have enhanced plant carbon isotope fractionation during the late cretaceous whereas changing p co 2 levels seem to have had no effect on plant carbon isotope fractionation the results of this study suggest that amber is a powerful fossil plant material for palaeoenvironmental and palaeoclimatic reconstructions improvement of the resolution of the existing data coupled with more detailed information about botanical source and environmental growing conditions of the fossil plant material will probably allow a more faithful interpretation of amber 13 c records and a wider understanding of the composition of the past atmosphere

retreat velocity of the north atlantic polar front during the last deglaciation determined by 14 c accelerator mass spectrometry the glacial oscillations which dominate the quaternary global climate are closely related to changes in incoming solar radiation but the details of palaeoclimatic spectra suggest that other parameters usually referred to as feedback have significantly increased the climatic response to extraterrestrial forcing1 the last deglaciation appears to be one of the more characteristic examples of nonlinearity because its abruptness strongly contrasts with the smooth shape of the associated solar radiation maximum dated at 11 000 yr bp in addition the presence of the younger dryas cold event concomitant with the solar radiation maximum could be interpreted as a transitory phenomenon caused by the rapid meltwater influx linked to the first phase of the ice sheet s disintegration2 3 here using accelerator mass spectrometry we date precisely the movements of the polar front during the whole period of glacial retreat 15 000 8 000 yr bp our results show that the polar front has moved between 35 n and 55 n in 1 000 yr for the earliest retreat 12 500 12 000 bp and moved almost instantaneously that is 400 yr during the two abrupt climatic changes associated with the younger dry as cold event

calibration of the c 14 timescale over the past 30 000 years using mass spectrometric u th ages from barbados corals uranium thorium ages obtained by mass spectrometry from corals raised off the island of barbados confirm the high precision of this technique over at least the past 30 000 years comparison of the u th ages with 14c ages obtained on the holocene samples shows that the u th ages are accurate because they accord with the dendrochronological calibration before 9 000 yr bp the 14c ages are systematically younger than the u th ages with a maximum difference of 3 500 yr at 20 000 yrbp the u th technique thus provides a way of calibrating the radiocarbon timescale beyond the range of dendrochronological calibration

quasigeostrophic dynamics of the western boundary current abstract a local model is used to investigate the dynamics of the western boundary current in a midlatitude wind driven gyre this current is important for the gyre as a whole and its local instability is correlated with structural changes of the separated eastward jet and the interior gyres in particular the eastward jet can be disrupted and broadened in the regime with a strong local instability in the western boundary current such a regime occurs with a no slip lateral boundary condition alternatively in the absence of local instability the eastward jet is narrow and penetrates farther in the basin interior this behavior is typical with free slip boundary condition both the linear stability and nonlinear time dependent behavior of the western boundary current are analyzed for a wide range of parameters the current loses stability at moderate reynolds numbers and the stability threshold strongly depends upon the vertical stratification profile the nonlinear time dependent flow contains wel

geoarchaeology and micromorphology of abric de la cativera catalonia spain abstract this paper presents the preliminary results of the geoarchaeological study of abric de la cativera el catllar tarragona a rock shelter containing late glacial and early holocene stratification spanning between c 11 3 and 7 9 ka 14 c bp the site is located in the gaia river valley on the southern catalonian coast the shelter situated at the foot of a low limestone wall was discovered in 1994 preliminary fieldwork was performed in 1995 comprising excavation of the early holocene layers and the sampling of the stratigraphic succession the geoarchaeological study was undertaken using a descriptive approach and so far has included a geomorphological survey of the surroundings the stratigraphic study of the site and micromorphological analysis high priority goals are a diachronic reconstruction of environmental change at the pleistocene holocene boundary and an understanding of the relationships between anthropic and non anthropic dynamics paying special attention to site formation processes the site s archaeological record represents human occupations affiliated to the microlaminar epipalaeolithic complex c and unit b and to early holocene macrolithic technocomplexes unit a according to the lithic assemblages recovered artefacts by products ecofacts manuports and art objects were collected during excavations and archaeological features were detected the results of the micromorphological study show that the abrupt climate changes around the pleistocene holocene ph limit are well recognisable at the site the beginning of the younger dryas yd and the ph limit are both represented by erosional surfaces and by the inwash of slope sediments cutting the late glacial pre yd alluvial succession deposited by the gaia river the shift from alluvial to a gravity driven sedimentary system is the result of an overall modification of the valley s morphodynamics the early holocene units record the transition to a mediterranean environment and the stabilisation of the slope human inputs are abundant in the entire stratigraphic succession except in the yd layers where a sudden decrease is observed anthropic activities determined the accumulation and modification of various components and the formation of anthropogenic microfacies and features the observation of micromorphological samples from layer a which contains occasional potsherds suggests its in situ position which is in contrast with the existing models on the regional processes of neolithisation a comparison between the pedo sedimentary and archaeological records indicates that the timing of environmental and cultural change at abric de la cativera is differential suggesting that the latter results from behavioural and cultural dynamics rather from environmental factors

boundary current separation in a quasigeostrophic eddy resolving ocean circulation model abstract the response of a rectangular flat bottom eddy resolving quasigeostrophic ocean to a steady double gyre wind stress is studied to assess the sensitivity of the solutions to a partial slip lateral boundary condition in which tangential stress is proportional to tangential velocity the constant of proportionality has limiting values of zero and infinity corresponding to free slip no stress and no slip conditions respectively seven numerical solutions corresponding to the values 0 0 2 0 3 5 5 0 6 5 8 0 and 100 0 are obtained which span the free slip and no slip limits significant qualitative changes in the time mean behavior of the solutions are observed to occur with increasing these changes include a gradual retreat of the separation points of the western boundary currents in the subtropical and subpolar gyres a dramatic reduction in the basin integrated reservoirs of mean and eddy kinetic energy a weakening of bottom dissipation and its replacement by lateral dissipat

properties of ancient deeply transformed man made soils cultural layers and their advances to classification by the example of early iron age sites in moscow region abstract the central part of european russia has been inhabited for several thousands of years its population being rather large in number by way of example we consider the dyakovo archeological culture dated to the early iron age numerous sites and settlements attributed to that culture are noted for the presence of typical anthrosols and technosols deeply transformed man made soils cultural layers in the course of the work we investigated thoroughly two soils related to settlements of the early iron age archeological excavations yielded numerous artifacts in situ this proves that the sites have been inhabited in the past though abandoned long since the cultural layers however have not been buried under later sediments far from it they stayed exposed and subjected to transformations by soil forming processes at present the sites are not in any use and are mostly overgrown with modern vegetation aside from the morphological description chemical analyses of the soils at the archeological sites have been performed a proportion of organic and inorganic matter total phosphorus ph being defined it should be noted that no typical zonal soils have been found at the sites in spite of the zonal vegetation overgrowing the areas instead there appeared soils of a peculiar kind showing specific properties when studying them the background soils were used as a reference so it seems that the time lapse between the early iron age and the present days a millennium and a half was insufficient for a complete transformation of the man made soils cultural layers it is rather difficult to choose a proper name of those soils the term technosol is hardly applicable as there are no human settlements there at present neither can the soils be considered as natural because they are radically different from the latter in characteristics and contain artificial materials in abundance

energetic baroclinic super tidal oscillations on the southeast florida shelf 1 historical and recent data reveal a very energetic regime on the shelf off southeast florida in addition to spin off eddies large amplitude tidal velocity fluctuations with amplitudes exceeding 0 5 ms 1 are observed recent exploratory measurements conducted as a part of the south florida ocean measurement center sfomc show that the time scale of these oscillations is about 10 hrs this period does not coincide either with the inertial period 27 hrs or with the semidiurnal m2 12 42 hrs or s2 12 hrs tidal constituents in addition these internal oscillations appear to be modulated seasonally a possible explanation is that these oscillations are near resonant internal seiches generated by barotropic tidal wave in the channel between florida and bahamas

amber inorganic geochemistry new insights into the environmental processes in a cretaceous forest of france amber fossils microorganisms arthropods and plant remains provide exceptionally well preserved data about past ecosystems but amber itself was rarely used as a paleoenvironmental tool here we present geochemical analyses of mid cretaceous amber of southwestern france that demonstrate the preservation of a primary inorganic geochemical signal especially the cretaceous ocean strontium isotopic ratio our results indicate that inorganic chemical analyses present a potential to uniquely document the paleoenvironmental conditions such as processes of water extraction of amber producing ecosystems

deformation induced microstructures in soils affected by mass movements the soil deformation produced by mass movements gives rise to specific microscopic features the study of some markers of deformation such as the orientation of rigid clasts and the morphology of fine grained intercalations indicates that in most cases mass movements can be related to simple shear the development of these features varies according mainly to the type of mass movement solifluction debris flow or earth slide different factors play a significant role in their formation intrinsic soil characteristics such as the grain size of the matrix water content and matrix element viscosity ratios and external factors such as the intensity and homogeneity of deformation a careful study of the microscopic features leads to a better understanding of the dynamics of mass deposits