radar imaging mechanism of marine sand waves at very low grazing angle illumination caused by unique hydrodynamic interactions 1 the investigations carried out between 2002 and 2004 during six field experiments within the operational radar and optical mapping in monitoring hydrodynamic morphodynamic and environmental parameters for coastal management oroma project aimed to improve the effectiveness of new remote sensing monitoring technologies such as shipborne imaging radars in coastal waters the coastal monitoring radar of the gkss research center geesthacht germany is based on a kelvin hughes rsr 1000 x band 9 42 ghz vertical vv polarized river radar and was mounted on board the research vessel ludwig prandtl during the experiments in the lister tief a tidal inlet of the german bight in the north sea the important progress realized in this investigation is the availability of calibrated x band radar data another central point of the study is to demonstrate the applicability of the quasi specular scattering theory in combination with the weak hydrodynamic interaction theory for the radar imaging mechanism of the seabed radar data have been taken at very low grazing angles 2 6 of flood and ebb tide oriented sand wave signatures at the sea surface during ebb tidal current phases current speeds perpendicular to the sand wave crest 0 6 m s 1 have been measured at wind speeds 4 5 m s 1 and water depths 25 m the difference between the maximum measured and simulated normalized radar cross section nrcs modulation of the ebb tide oriented sand wave is 27 for the flood tide oriented sand wave a difference of 21 has been calculated the difference between the minimum measured and simulated nrcs modulation of the ebb tide oriented sand wave is 10 and for the flood tide oriented sand wave a value of 43 has been derived phases of measured and simulated nrcs modulations correspond to asymmetric sand wave slopes the results of the simulated nrcs modulation show the qualitative trend but do not always quantitatively match the measured nrcs modulation profiles because the quasi specular scattering theory at very low grazing angle is a first order theory

quantitative reconstruction of middle and late eocene paleoclimate based on palynological records from the huadian basin northeastern china evidence for monsoonal influence on oil shale formation abstract the eocene was an interval of climate evolution when the extreme high temperatures of the earliest cenozoic gave way to a global cooling trend fine grained lacustrine sediments of eocene age from northeastern china represent an excellent archive to study long term environmental and climatic changes at high resolution the huadian basin is a cenozoic fault bounded basin in jilin province northeastern china though small in area it contains numerous oil shale and coal bearing layers which provide an abundant middle to late eocene palynoflora eighty five palynomorph genera and one hundred palynomorph species were identified in the huadian formation allowing to distinguish 4 palynozones the nearest living relatives of the recovered palynomorph taxa suggest the presence of subtropical evergreen and deciduous broad leaved forests during deposition of the huadian formation using the coexistence approach ca we calculated seven paleoclimatic parameters which indicate a subtropical warm and humid climate with a mean annual temperature above 13 6 c and a mean annual precipitation of at least 887 mm however the climate became cooler and drier during the transition from the lower oil shale member to the upper carbonaceous shale member palaeoclimatic data from the various middle and late eocene basins of northeastern china i e the huadian fushun yilan hunchun and jishu basins were compared with data from north american and european basins middle eocene climate in the northern hemisphere was generally warm and humid and the mean annual temperature and precipitation in northeastern china were similar to those in north america though slightly lower than those of europe similar trends in temperature and precipitation on different continents support the existence of a global mid eocene cooling event this paper is the first systematic study of middle to late eocene seasonality in the huadian basin our results show an apparent differentiation in both temperature and precipitation between summer and winter supporting the view that the east asian monsoon was established in northeastern china already during the middle to late eocene this middle and late eocene monsoon was likely driven by the development of pacific trade winds and an alternating seasonal high and low pressure system over siberia the climatic changes observed in our dataset especially the precipitation changes appear to have played an important role in controlling oil shale formation in the huadian basin a warmer and more humid climate with abundant precipitation and high subsidence rates formed a deeper huadian depositional lake high productivity and stable stratification provided the abundant organic matter and favorable preservation conditions necessary for oil shale accumulation

precipitation driven decadal scale decline and recovery of wetlands of lake pannon during the tortonian high resolution pollen and dinoflagellate analyses were performed on a continuous 98 cm long core from tortonian deposits of lake pannon in the styrian basin in austria the sample distance of 1 cm corresponds to a resolution of roughly one decade allowing insights into environmental and climatic changes over a millennium of late miocene time shifts in lake level surface water productivity on a decadal to centennial scale can be explained by variations of rainfall during the tortonian climatic optimum related to negative fine scale shifts of mean annual precipitation shoreline vegetation belts reacted in an immediate replacement of poaceae by cyperaceae as dominant grasses in the marshes fringing the lake in contrast to such near synchronous ecosystem responses to precipitation a delayed lake level rise of 4 6 decades is evident in the hydrological budget of lake pannon this transgression caused by a precipitation increase up to 1200 mm yr resulted in a complete dieback of marshes simultaneously open water dinoflagellates such as impagidinium took over in the brackish lagoon and fresh water dinoflagellates disappeared as soon as the rainfall switched back to moderate levels of 1100 1200 mm yr the rise of the lake level slowed down the marsh plants could keep up again and the former vegetation belts became re established thus mean annual precipitation more than temperature was the main driving force for high frequency fluctuations in the tortonian wetlands and surface water conditions of lake pannon such high resolution studies focusing on tortonian decadal to centennial climate change will be crucial to test climate models which try to compare the tortonian models with predictions for future climate change

what controlled mid late miocene long term aridification in central asia global cooling or tibetan plateau uplift a review abstract debate continues over whether global cooling or uplift of the tibetan plateau provided the first order driver for the aridification moisture levels of central asia throughout the mid late miocene between about 17 and 5 ma this review attempts to throw new light on the relations between the aridification and these two key factors this paper examines the evolution of miocene climate both moisture and temperature within five separate regions of eurasia to help understand the large scale controls of long term moisture in central asia the five regions include 1 europe 2 high latitude asia 3 the east asian monsoon region 4 the south asian monsoon region and 5 central asia itself because moisture reaching central asia has to firstly cross at least one of the other four regions temperature proxy data compiled from these five regions correlate with ocean temperatures from the global deep sea oxygen isotope records furthermore compiled moisture proxy data from the four regions surrounding central asia co vary and correlate with each other this can be explained by positive feedbacks between drying and cooling and supports the assumption that global cooling provides a dominant driving factor for the drying of eurasia global cooling reduces the amount of water vapor held in the atmosphere and thereby can cause terrestrial drying however in central asia the moisture evolution shows less similarity with its surroundings the uplift of the tibetan plateau including the tianshan mountains could provide a possible explanation for this difference the changing topography resulting from uplift events over time and space strongly influenced the moisture patterns in central asia during miocene times future research on the spatial timing and amplitude of tibetan plateau uplift should be useful to understand the moisture processes in central asia during the miocene

present day climatic equivalents of european cenozoic climates abstract recently continental climate evolution in central europe over the last 45 ma has been reconstructed from the palaeobotanical record using a nearest living relative methodology coexistence approach ca the reconstructed climate curves document in detail the transition from almost tropical conditions in the mid eocene to a temperate climate at the pliocene pleistocene transition the observed climatic shifts are primarily expressed as non proportional changes of the different variables taken into account in the present study a published palaeoclimate data set for a total of 42 macrofloras complemented by new calculations is used as base to analyse the climatic space in which a fossil flora existed to define these spaces ca intervals calculated for 3 temperature mean annual temperature cold and warm month mean and 3 precipitation variables mean annual precipitation mean monthly precipitation of the driest and of the wettest month are combined using a global gridded climatology 10 resolution this climate space is then utilized to identify recent climate analogues with respect to the variables regarded for 18 macrofloras climatic analogue regions with respect to 6 variables are identified on the globe for 16 macrofloras analogues exist when three temperature parameters and mean annual precipitation are regarded no recent equivalents are found in 8 cases this corroborates the assumption of the temporary existence of non analogue climates in the cenozoic as shown by multivariate statistics the observed anomalies with respect to present day conditions basically refer to high winter temperatures deploying a gis the recent climate analogues can be presented as sets of grid cells for each flora that can be mapped on a globe once identified these regions can be merged with adequate thematic layers to assess additional proxy data for the palaeofloras to exemplify the procedure koeppen climate type numbers of days with ground frost as well as matthews biome classes are reconstructed the resulting koeppen types ranging from a to c are largely consistent with data previously published the ground frost record shows almost frost free conditions for the mid eocene greenhouse and for the mid miocene climatic optimum for the chattian up to 7 days with ground frost result during the late miocene cooling the number of days with ground frost significantly increased the inferred matthews biomes reveal changing patterns of evergreen and deciduous forest cover when recent climate analogues are found for a fossil flora present climate can be used to calibrate the original ca data it is shown that calibration considerably improves the resolution of the continental climate records

a suggestion for the origin of mesoscopic fabric in accretionary melange based on features observed in the chrystalls beach complex south island new zealand the chrystalls beach complex a probable accretionary melange of triassic age cropping out in south island new zealand contains a distinctive set of mesoscopic structures all of which contribute to the typically chaotic appearance of the melange these structures are 1 soft sediment bedding pull aparts 2 weakly developed slaty cleavage 3 folds in dismembered bedding with slaty cleavage as the axial surface foliation and 4 quartz fiber lineated shear surfaces analysis of overprinting relations indicates that these structures formed during a single progressive deformation rather than in several discrete events as such they record a change in response to incremental strain from initial ductile behavior toward one dominated by brittle failure it is suggested that this variation resulted from progressive dewatering during shallow level accretion at the base of an inner trench slope

radar imaging mechanism of the seabed results of the c star experiment in 1996 with special emphasis on the relaxation rate of short waves due to current variations abstract during the field experiment of the coastal sediment transport assessment using sar imagery project of the marine science and technology program of the european commission an air sea interaction drift buoy asib system was equipped with special sensors and instruments to measure the position the water depth the surface current velocity and direction the modulation characteristics of short wave energies and relevant air sea interaction parameters due to undulations in the seabed the asib system was operated from on board a research vessel and the data were measured while the buoy drifted in the tidal currents across sand waves of the study area all buoy measurements were analyzed by computing frequency spectra of low and high frequency waves scalar spectra between 0 1 and 50 hz the whole range of short water waves was recorded by these in situ measurements on board the buoy which is responsible for the backscattering of commonly used air and spaceborne imaging radars a comprehensive da

continental climate gradients in north america and western eurasia before and after the closure of the central american seaway abstract the gulf stream as part of the atlantic meridional overturning circulation amoc is known as a major driver of latitudinal energy transport in the north atlantic presently causing mild winters over northwestern eurasia the intensity of the amoc throughout the neogene prior to the final closure of the central american seaway cas in the early pliocene is still poorly known but most authors assume that the circulation was considerably weaker than present here we address this issue from a continental point of view we studied the past amoc intensity by analyzing neogene continental climate patterns along north american and western eurasian transects based on a total of 317 palaeofloras thermal latitudinal gradients are reconstructed for three neogene time slices namely the middle miocene late miocene and late pliocene using the coexistence approach to obtain quantitative climate data the obtained proxy based continental temperature gradients are evaluated against data from a selection of published general circulation model gcm simulations for the three time slices studied our study suggests that shallow thermal latitudinal gradients existed in north america and western eurasia throughout the miocene but became strongly steepened in the late pliocene in both miocene time slices studied the higher latitudes were by up to 30 c warmer than present cold month mean also at times with presumed pre industrial co2 such as the late miocene in the late pliocene high latitude the temperature difference with respect to the present had decreased by up to 10 c cold month mean both mean annual temperatures and cold month means of the lower mid and low latitudes were at the present day level throughout all three time slices or even slightly below in both miocene time slices zonal temperature means at both continental transects were similar in the mid and higher latitudes however several northwest european sites reveal very mild winter condition suggesting the early existence of a probably less intense palaeo gulf stream the distinct thermal anomaly annual and cold month means today existing between north america and western eurasia appeared for the first time in the late pliocene attaining about 50 of the present day magnitude this supports the assumption that the amoc intensified after the final closure of the cas during the early pliocene the results obtained from the palaeobotanical proxies are in line with data from coeval marine archives particularly with north atlantic sea surface temperatures ssts inferred from oxygen isotopes however the proxy based thermal gradients are not well reproduced by a selection of gcm simulations due to a well known systematic underestimation of high latitude warming by gcms for the miocene and pliocene time slices

mapping submarine sand waves with multiband imaging radar 2 experimental results and model comparison on august 16 1989 and on july 12 1991 experiments were performed to study the mapping of submarine sand waves with the airborne imaging radar a polarimetric and in 1991 interferometric airborne p l and c band synthetic aperture radar system the experiments took place in an area 30 km off the coast of the netherlands where the bottom topography is dominated by sand waves with a height between 2 and 6 m and a crest to crest distance of about 400 m at an average depth of 22 m ground measurements were recorded on a nearby platform and on a ship in the test area which also acted as a position fix on august 16 1989 the wind was 5 m s directed toward the northeast while the surface current velocity was around 0 5 m s directed toward the southwest one overflight was made with the flight direction parallel to the sand wave crests and the radar looking upwind at p band the sand waves are clearly visible as dark bands as predicted by theory while at l band the sand waves show up as sawtooth shaped modulations on july 12 1991 wind and surface current had the same opposite directions as in 1989 though the wind was much higher 10 m s three flights were made with the radar pointing upwind cross wind and downwind the upwind and downwind images are very similar despite the high wind speed the sand waves are clearly visible as sawtooth shaped modulations at p band and vaguely visible at l band at c band only wind streaks can be seen all cross wind images show the sand waves as dark bands now with the highest modulations at c band the wind streaks that dominated the upwind and downwind images at c band are much less pronounced in the cross wind images the images are compared with predictions from a new model of the imaging mechanism which includes contribution to the radar cross section of waves moving both from and to the radar wave blocking or wave reflection is treated in an approximate manner for the radar looking upwind or downwind the predicted modulations at p and l band agree well with the observations while those at c band are too high for the radar looking cross wind the model severely underestimates the modulations it is questioned whether a local relaxation source term can describe such a situation the interferogram shows some structure caused by bottom induced surface current variations

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

the coexistence approach a method for quantitative reconstructions of tertiary terrestrial palaeoclimate data using plant fossils abstract the coexistence approach is introduced as a method for quantitative terrestrial palaeoclimate reconstructions in the tertiary it is based on the assumption that tertiary plant taxa have similar climatic requirements to their nearest living relatives the aim of the coexistence approach is to find for a given fossil flora and a given climate parameter the climatic interval in which all nearest living relatives of the fossil flora can coexist for this purpose we have developed a data base climbot containing for over 800 tertiary plant taxa the nearest living relatives and their climatic requirements and an algorithm for analysis climst for all types of fossil floras the coexistence approach thus allows the rapid quantitative reconstruction of 10 different climate parameters including the mean annual temperature temperature of the warmest month temperature of the coldest month mean annual precipitation maximum monthly precipitation minimum monthly precipitation precipitation of the warmest month relative humidity potential evaporation as well as the ratio of mean annual precipitation over potential evaporation the reliability and resolution of the coexistence approach are tested with various techniques and proved to be reasonably good for instance the resolution with respect to the mean annual temperature can be up to 1 c applications to various modern and fossil floras are illustrated and the advantages and disadvantages of the coexistence approach are discussed

the miocene climatic optimum evidence from ectothermic vertebrates of central europe abstract data sets of central european temporal distributions of thermophilic ectothermic vertebrates channidae varanidae chamaeleonidae cordylidae tomistomidae alligatoridae giant turtles and of north alpine foreland basin nafb distributions of ectothermic vertebrates adapted to dryer habitats albanerpeton inexpectatum salamandra sansaniensis bufo cf viridis chamaeleo caroliquarti gekkonidae varanus hofmanni bransateryx sp are analysed two main migration events of thermophilic ectotherms at 20 ma and 18 ma in the lower miocene are discerned they indicate the beginning of the miocene climatic optimum in central europe 42 45 n palaeolatitude with a lower limit of the mean annual temperature mat of 17 4 c derived from the minimal mat of their extant relatives furthermore additional palaeobotanical data and records of bauxite point to a mat of 22 c this warm and humid optimum peaked at 18 16 5 ma ottnangian karpatian and is confirmed by the coexistence of all investigated thermophilic taxa the following period early badenian is characterised by probably unchanged temperatures but a seasonality in precipitation with dry periods up to six months two major seasonal phases between 16 3 and 15 7 ma earliest early badenian and between 14 7 and 14 5 ma early middle badenian transition are indicated by an immigration of dry adapted taxa from the surrounding karst plateau to the nafb it is presumed that the tectonical reorganisation of the central paratethys realm had considerable influence on this regional humidity pattern the warm period ended abruptly between 14 0 and 13 5 ma middle late badenian transition with major regional extinction events of most of the thermophilic groups in central europe and a drop of the mat of probably more than 7 c to temperatures around 14 8 15 7 c this drop can be attributed predominantly to a decrease of more than 11 c of the minimum cold months temperature this temperature decrease marked the beginning of a climatic zonation of the european continent and is also evidenced by a progressively southward disappearance of the crocodile diplocynodon from 38 45 n palaeolatitude to 30 37 n during the middle and earliest late miocene the results correlate well with palaeobotanical data from the mid latitudes of europe and north america and the deep sea temperature curve generated from oxygen isotope ratios

modulation of radar backscatter from the ocean by a variable surface current abstract calculations of surface wave and radar cross section modulation induced by a spatially varying surface current have been compared with field measurements made with sar x and l bands real aperture radar x band laser slope guage and ccd video camera during the joint canada u s ocean wave investigation project jowip which took place in august 1983 the comparison reveals that i many existing wind relaxation models underpredict the hydrodynamic effect of the current ii simple bragg scattering model underpredicts radar backscatter modulation for higher frequency radars e g x band but appears acceptable at lower radar frequencies e g l band iii the discrepancy between measurements and calculations at high radar frequency is reduced but not eliminated when the effects of long surface waves have been accounted for keywords include radar backscatter surface wave modulations wave current interactions georgia strait experiment and jowip

the geological significance of some triassic microfossils from the south orkney islands scotia ridge late triassic radiolaria have been recovered from a bedded chert collected early in 1977 in the south orkney islands this is the first reliable palaeontological evidence for the age of the so called basement complex that forms most of the exposed rock of a microcontinent on the southern limb of the scotia ridge the fossils place a lower limit on the age of deformation of at least part of the complex as post karnian or norian the basement is overlain by undeformed jurassic to cretaceous conglomerates which suggests this event took place during the early mesozoic gondwanian orogeny the new data are consistent with the interpretation that the basement complex of the south orkney islands represents part of a subduction complex and was accreted to the pacific margin of gondwanaland during the late triassic or early jurassic time

radar imaging of submarine sand waves in tidal channels the simple theoretical model of alpers and hennings describing the radar imaging of submarine bottom topography in coastal waters with strong unidirectional tidal currents is analytically extended to show the influence of advection the theory applies for l band radar where second order terms in the hydrodynamic interaction can be neglected as a first approximation if future imaging radars from satellites and space platforms as the ers i first european remote sensing satellite the jers i first japanese earth remote sensing satellite and the eos earth observing system are to be used for cartographic applications it is necessary to include the effect of advection to improve accuracy this extension of the model simulates the position of the radar cross section modulation relative to coastal geomorphological bedforms by application of that theory it is possible to map features such as the crests of sandbanks and sand waves

a theory of the ka band radar imaging mechanism of a submerged wreck and associated bed forms in the southern north sea the ka band radar imaging mechanism of the submerged wreck sand ribbon of the motor vessel m v birkenfels in the southern north sea is investigated by applying the quasi specular scattering theory and considering the capillary as well as the gravity wave ranges of the wave energy density spectrum for the imaging of wrecks and other oceanographic and meteorological phenomena at the sea surface it is assumed that quasi specular scattering becomes dominant at higher radar frequencies like ka and x band and wind speeds 7 8 m s 1 multibeam echo sounder images of the birkenfels wreck and associated sand ribbons as well as other available environmental in situ data have been analyzed the formation of sand ribbons at the sea bed and the manifestation of its radar signatures at the water surface are caused by an elliptical vortex or helical flow cell triggered by unidirectional tidal current flow interacting with the wreck the difference between simulated and measured normalized radar cross section nrcs modulation as a function of the space variable is less than 31 6 results are presented for nrcs simulations dependent on position for different effective incidence angles unidirectional current speeds wind speeds and relaxation rates the calculated current gradient or strain rate of the imaging theory has the same order of magnitude as those obtained for marine sand waves this implies that the responsible hydrodynamic interaction mechanism is able to produce radar signatures of submerged wrecks sand ribbons and make them visible at the sea surface

changes in atmospheric co2 concentrations and climate from the late eocene to early miocene palaeobotanical reconstruction based on fossil floras from saxony germany abstract in the present study proxy data concerning changes in atmospheric co2 and climatic conditions from the late eocene to the early miocene were acquired by applying palaeobotanical methods fossil floras from 10 well documented locations in saxony germany were investigated with respect to 1 stomatal density index of fossil leaves from three different taxa eotrigonobalanus furcinervis laurophyllum pseudoprinceps and laurophyllum acutimontanum 2 the coexistence approach ca based on nearest living relatives nlr and 3 leaf margin analysis lma whereas the results of approach 1 indicate changes in atmospheric co2 concentration approaches 2 and 3 provide climate data the results of the analysis of stomatal parameters indicate that the atmospheric co2 concentration was higher during the late eocene than during the early oligocene and increased towards the late oligocene a lower atmospheric pco2 level after the late eocene is also suggested by an increase in marine palaeoproductivity at this time from the late oligocene onwards no changes in atmospheric co2 concentration can be detected with the present data for the considered sites the results of the coexistence approach and of the leaf margin analysis document a significant cooling event from the late eocene to the early oligocene the pco2 decrease from the late eocene to the early oligocene indicated by the stomatal data raised in this study was thus coupled to a temperature decrease which is reflected by the present datasets from the early oligocene onwards however no further fundamental climate change can be inferred for the considered locations the pco2 increase from the early oligocene to the late oligocene which is indicated by the present data is thus not accompanied by a climate change at the considered sites a warming event during the late oligocene is however recorded by marine climate archives according to the present data no change in pco2 occurred during the cooling event at the oligocene miocene boundary which is also indicated by marine data the quality and validity of stomatal parameters as sensors for atmospheric co2 concentration are discussed

mapping submarine sand waves with multiband imaging radar 1 model development and sensitivity analysis in 1989 and 1991 unexpected modulations caused by submarine sand waves were observed with the airborne imaging radar air a p l and c band synthetic aperture radar the measurements were performed in a sand wave area off the dutch coast the sand waves have an asymmetric sawtooth shaped profile with the steep slope oriented toward the northeast during the experiments wind and current had opposite directions the wind was directed toward the northeast and the current toward the southwest under these conditions existing models for the imaging mechanism predict that the modulation depth decreases with increasing radar frequency and that the steep slopes show up as dark lines in radar images the air images show a relation between modulation depth and radar frequency as predicted however only the p band image of 1989 shows the steep slopes of the sand waves as dark lines the p band image of 1991 and the l band images of 1989 and 1991 show a sawtooth shaped modulation which cannot be explained by existing theory a new model is developed that is one dimensional in position space and fully two dimensional in wavenumber space the radar cross section is calculated using both first order bragg and an integral equation scattering model in which the cross section originates from a spectral band rather than a single value the new model contains two improvements over previous ones first wave blocking or better wave reflection is included though in an approximate manner it is shown to be of importance at p band only second the contribution to the radar cross section from waves moving both to and from the radar is included whereas some previous models consider only one of these contributions this explains the observed modulations at least qualitatively under the assumptions that the angular distribution of short waves is almost constant and that waves moving against the wind have small relaxation rates

boils and turbulence in a weakly stratified shallow tidal sea abstract measurements of turbulence are made in a weakly but variably stratified region of tidal straining in the eastern irish sea using turbulence sensors profiling vertically through the water column on the fast light yo yo fly profiler and horizontally on the autonomous underwater vehicle auv autosub the tidal currents exceed 1 m s 1 at the location of the measurements in water of a depth of about 43 5 m and result in turbulence extending from the seabed to the surface with a cycle period that is half that of the tides as previously observed the time of onset of enhanced turbulence that is measured by the sensors on fly and autosub as the speed of tidal currents increases are in good agreement as are their mean levels boils on the sea surface are identified using the autonomously recording inverted echo sounder version 2 aries ii a two beam upward pointing side scan sonar mounted on a rig resting on the seabed the boils have mean horizontal dimensions of about 25 m they are continually

a late eocene palynological record of climate change and tibetan plateau uplift xining basin china climate models suggest that asian paleoenvironments monsoons and continental aridification were primarily governed by tectonic uplift and sea retreat since the eocene with potential contribution of global climate changes however the cause and timing of these paleoenvironmental changes remain poorly constrained the recently well dated continental mudflat to ephemeral saline lake sedimentary succession situated in the xining basin at the northeastern margin of the tibetan plateau nw china provides a unique opportunity to develop additional proxy successions in this area that are placed accurately in time here a palynological record from this succession is reported high abundances of desert and steppe desert taxa such as ephedripites and nitrariadites nitraripollis are found which can be differentiated by the presence of broad leaved deciduous forest taxa in the lower part of the section particularly up to 36 4 ma magnetochron c16r and a sudden increase of pinaceae pinuspollenites piceaepollenites and abiespollenites which is dated at 36 1 ma c16n 2n coexistence approach coa indicates that from 39 9 to 36 4 ma c17n 1n regional climate was warm and wet while from 36 4 to 33 5 ma c16n 2n c13r climate tends to be cooler and drier the data indicate that paleoenvironmental and palynological changes on the ne part of the tibetan plateau resulted from a combination of long term tectonic uplift forcing and long and short term climate changes the increase of taxa such as piceaepollenites and abiespollenites indicates not only a cooling and drying trend prior to the eocene oligocene e o boundary but also the existence of high altitude mountain habitats in the periphery of the xining basin the sudden pinaceae event correlates closely in time with a marked aridification step as viewed from the lithology of the xining basin that was linked to the sea retreat out of the tarim basin

monsoon variability over peninsular india during late pleistocene signatures of vegetation shift recorded in terrestrial archive from the corridors of western ghats abstract the fossil flora recovered from the kangvai well ratnagiri district maharashtra 17 53 41 n 73 12 23 e has been used to reconstruct the monsoon variations and seasonal rainfall pattern during the late pleistocene 44 020 390 years bp by using the coexistence approach the reconstruction suggests that the southwest sw and northeast monsoons ne contributed 64 and 18 of the total rainfall respectively moreover the pre monsoon showers were responsible for about 15 of the annual rainfall as both sw and ne monsoons were very active along with the pre monsoonal rainfall the length of rainy season increased and extended up to 9 months in a year favouring the evergreen continuum and prevalence of wet evergreen forests until the late glacial maximum or slightly prior to it however due to the weakening of ne and pre monsoon rainfall later in the late pleistocene and early holocene the area experiences only four months of rainy season now on account of the present day sw monsoon these changes resulted in the extinction of wet evergreen taxa which are now endemic to the wetter parts of western ghats from the fossil locality our reconstruction agrees with the previous studies from the western ghats suggesting that the wet evergreen taxa require

distribution of clay minerals in the northern north sea basin during the paleogene and neogene a result of source area geology and sorting processes abstract clay mineral compositions have been analyzed in samples from the danish norwegian british and dutch north sea sectors and from onshore denmark and germany comprising both wells and outcrops clay pits and cliff sections the time slices investigated comprise from the paleogene the post ekofisk fm interval of the paleocene the entire eocene and the entire oligocene the neogene time slices investigated comprise the following miocene intervals the vejle fjord fm the klintinghoved fm the arnum fm and the gram fm there were not enough samples from offshore wells to make a detailed stratigraphic subdivision of the paleogene it was however possible to refer miocene samples to specific lithostratigraphic units the onshore danish nomenclature was applied and seismic sections were used to correlate between wells and outcrops existing biostratigraphic data were used to control the stratigraphic interpretation the distribution of the most dominant clay minerals smectite chlorite kaolinite and illite are shown on maps comprising the paleocene eocene oligocene and the formations vejle fjord fm klintinghoved fm arnum fm and gram fm from the miocene the investigation has shown that the source rock composition plays an important role in the clay mineral content of the sediments for example smectite makes up a higher proportion in periods with substantial supply of volcanic material especially in the paleocene and early eocene in source areas where metamorphic rocks dominate chlorite is present in the sediment adjacent to these areas the illite content in sediments increases where the source area is dominated by granites and or gneisses sorting of the supplied suspended material generally controls the depositional area for the minerals for example the larger particles of kaolinite are generally more abundant in nearshore areas whereas the relatively small smectite particles normally dominate in the central parts of the sedimentary basins illite and chlorite are relatively abundant in areas between those rich in smectite present in the central part of the basin and those rich in kaolinite present in the marginal parts of the basin climatic conditions during erosion and deposition seem to play an important role especially in the distribution of chlorite which is rather sensitive to chemical weathering this means that chlorite makes up a greater proportion of the sediment in periods with colder climate such as in the oligocene and late miocene the uplift of surrounding areas seems to be an important factor for the amount of detrital material transported to the north sea the elevation of marginal areas also played an important role in the reworking of paleogene sediments during the neogene mass flows including turbidity currents have redistributed marginal kaolinite rich sediments deposited in marginal areas of the basin to more basin central locations especially in the paleocene viking graben diagenetic modification of the originally supplied clay minerals seems to be minor since the highest contents of smectite occur in the oldest and deepest areas with more than 3 km of overburden the reason for this is believed to be the extremely low permeability of the very fine grained smectite dominated clays hindering water from being expelled from the sediments combined with low contents of k bearing minerals necessary for the formation of illite from smectite

mean flow and turbulence structure over fixed two dimensional dunes implications for sediment transport and bedform stability detailed measurements of flow velocity and its turbulent fluctuation were obtained over fixed two dimensional dunes in a laboratory channel laser doppler anemometry was used to measure the downstream and vertical components of velocity at more than 1800 points over one dune wavelength the density of the sampling grid allowed construction of a unique set of contour maps for all mean flow and turbulence parameters which are assessed using higher moment measures and quadrant analysis these flow field maps illustrate that 1 the time averaged downstream and vertical velocities agree well with previous studies of quasi equilibrium flow over fixed and mobile bedforms and show a remarkable symmetry from crest to crest 2 the maximum root mean square rms of the downstream velocity values occur at and just downstream of flow reattachment and within the flow separation cell 3 the maximum vertical rms values occur within and above the zone of flow separation along the shear layer and this zone advects and diffuses downstream extending almost to the next crest 4 positive downstream skewness values occur within the separation cell whereas positive vertical skewness values are restricted to the shear layer 5 the highest reynolds stresses are located within the zone of flow separation and along the shear layer 6 high magnitude high frequency quadrant 2 events ejections are concentrated along the shear layer kelvin helmholtz instabilities and dominate the contribution to the local reynolds stress and 7 high magnitude high frequency quadrant 4 events occur bounding the separation zone near reattachment and close to the dune crest and are significant contributors to the local reynolds stress at each location these data demonstrate that the turbulence structure associated with dunes is controlled intrinsically by the formation magnitude and downstream extent of the flow separation zone and resultant shear layer furthermore the origin of dune related macroturbulence lies in the dynamics of the shear layer rather than classical turbulent boundary layer bursting the fluid dynamic distinction between dunes and ripples is reasoned to be linked to the velocity differential across the shear layer and hence the magnitude of the kelvin helmholtz instabilities which are both greater for dunes than ripples these instabilities control the local flow and turbulence structure and dictate the modes of sediment entrainment and their transport rates

suspended sediment signatures induced by shallow water undulating bottom topography near surface signatures of suspended sediment concentration ssc related to submerged bed forms displayed in visible band data gathered by space borne imaging sensors are described detailed acoustic doppler current profiler adcp data of vertical current velocity component echo intensity modulation of ssc and related oceanographic and meteorological observations in a tidal inlet of the north sea have been analyzed to understand the associated hydrodynamics of the optical imaging mechanism theoretical considerations based on the navier stokes and sediment continuity equations have been carried out as a first approximation these theoretical results explain signatures of enhanced ssc of in situ measurements and analyzed space borne images strong currents flowing over steep bottom topography are able to stir up the sediments to form both a general continuum of ssc and localized pulses of higher ssc in the vicinity of the causative bed feature itself the strain rate equivalent to the current gradient is an important parameter describing near water surface oceanographic and meteorological phenomena in the visible and microwave part of the electromagnetic spectrum observed by shore and ship based as well as air and space borne remote sensing systems significant disagreements between theoretical results of the strain rate generated by the surface current and in situ observations at the crests of submerged ridges and sand waves were identified possible explanations could be first the current velocity may not be barotropic near the crests of such bed forms and second mass conservation may not only be maintained through an acceleration or deceleration of the flow this implies that active up and downwelling effects of the three dimensional current field can also play a significant role for hydrodynamic interaction between current and underwater bed forms

miocene climate in europe patterns and evolution to improve our understanding of long term climate changes during the neogene in eurasia the international research network neclime neogene climate evolution in eurasia was established in the year 2000 in this first synthesis results of neclime activities focussing on the miocene of europe as one key area are combined to present a summary of the climate evolution in time and space more than 300 miocene fossil floras have been compiled and quantitatively analysed in terms of several climatic parameters during the last few years in this volume alone about 75 new data sets are available to synthesize the results of this volume quantitative climate maps for europe are generated on palaeogeographic maps for langhian and early tortonian for the first time characteristic climate patterns appear for each time interval and can be related to both global climate change and alpine tectonics generally the climate maps combine and support the individual results discussed in this volume for the individual regions

the coexistence approach theoretical background and practical considerations of using plant fossils for climate quantification the coexistence approach was established by mosbrugger and utescher 1997 as a plant based method to reconstruct palaeoclimate by considering recent climatic distribution ranges of the nearest living relatives of each fossil taxon during its existence for over more than 15 years its basics have been tested and reviewed in comparison with other terrestrial and marine climate reconstruction techniques and climate modelling data however some controversies remain about its underlying data or its applicability in general in view of these controversies this paper discusses the power and limitations of the coexistence approach by summarising past results and new developments we give insights into the details and problems of each step of the application from the assignment of the fossil plant to the most suitable nearest living relative the crucial consideration of the usefulness of specific taxa towards their climatic values and the correct interpretation of the software based suggested palaeoclimatic intervals furthermore we reflect on the fundamental data integrated in the coexistence approach by explaining different concepts and usages of plant distribution information and the advantages and disadvantages of modern climatic maps additionally we elaborate on the importance of continually updating the information incorporated in the database due to new findings in e g palaeo botany meteorology and computer technology finally for a transparent and appropriate use we give certain guidelines for future applications and emphasize to users how to carefully consider and discuss their results we show the coexistence approach to be an adaptive method capable of yielding palaeoclimatic and palaeoenvironmental information through rime and space c 2014 elsevier b v all rights reserved

modelling late miocene vegetation in europe results of the caraib model and comparison with palaeovegetation data abstract the caraib carbon assimilation in the biosphere model is used to study the vegetation distribution during the late miocene tortonian in this version the plant classification is specifically adapted to best represent miocene european vegetation compared to other plant classifications used in global models this adapted classification is more refined since it is specifically developed for european vegetation and it includes various thermophylous tree types which were present in europe during the miocene the corresponding climatic tolerance parameters are based on the study of laurent et al journal of vegetation science 15 739 746 2004 for the tree types currently present in europe and on the distribution of analogue species in southeastern asia and north central america for the thermophylous sub tropical trees the same classification is used to characterize the palaeoflora at the available late miocene localities allowing a model data comparison at the plant functional type level rather than at the biome level the climatic inputs to caraib are obtained from the cosmos atmosphere ocean general circulation model the climatic anomalies tortonian minus present derived from cosmos are interpolated to a higher spatial resolution before being used in the vegetation model these anomalies are combined with a modern climatology to produce climatic fields with high spatial resolution 10 10 this procedure has the advantage of making apparent relief features smaller than the grid cells of the climate model and hence makes easier the comparison with local vegetation data although it does not really improve the quality of the tortonian climate reconstruction the new version of caraib was run over europe at this higher spatial resolution it calculates the potential distribution of 13 different classes of trees including cold cool warm temperate sub tropical and tropical types together with their cover fractions net primary productivities and biomasses the resulting model vegetation distribution reconstructed for the tortonian is compared to available palaeovegetation and pollen data before performing this comparison the tree taxa present at the various data sites are assigned to one or several model classes depending on the identification level of the taxa if several classes are possible for a taxon only those that can co exist with the other tree classes identified at the site are retained this methodology is similar to the co existence approach used in palaeoclimatic reconstructions based on vegetation data it narrows the range of tree types present at the various sites by suppressing in the data the extreme types such as the cold boreal temperate and tropical trees the method allows a comparison with the model simulation on a presence absence basis this comparison provides an overall agreement of 53 between the model and the data when all sites and tree types are considered the agreement is high 85 for needle leaved summergreen boreal temperate cold trees larix sp and for tropical trees intermediate 40 for other boreal temperate cold trees and for needle leaved evergreen temperate cool trees broadleaved summergreen temperate cool trees and broadleaved evergreen warm temperate trees and poor

a complete arc trench system recognized in gondwana sequences of the antarctic peninsula region prior to late triassic early jurassic times the geological history of the antarctic peninsula region was dominated almost entirely by gondwana sequences that together comprised a major arc trench system subduction complex trench slope break and fore arc basin sedimentation can all be recognized and deposition was at least partly on early palaeozoic or older continental crust the only evidence for a contemporaneous magmatic arc situated in the antarctic peninsula at this time consists of patchy occurrences of metavolcanic rocks possibly representing the frontal edge of the arc and the major outcrop area of these rocks is believed to lie under the broad shallow continental shelf e of the antarctic peninsula this is contrary to most current hypotheses in which a marginal basin presumably floored by oceanic crust is thought to crop out close to the e coast of the antarctic peninsula however the complete absence of substantial outcrops of pre jurassic volcanic rocks anywhere in eastern antarctica and south africa which are the closest and most likely places in which these should exist supports the new proposal moreover the identification of back arc elements of the arc trench system foreland fold thrust belt and retro arc foreland basin in eastern antarctica and south africa greatly strengthens the likelihood of the arc cropping out in the area suggested towards the end of the triassic and during the early jurassic periods an intense diastrophic event or culmination of events of orogenic magnitude occurred gondwanian orogeny causing substantial redistribution of the pre existing elements of the arc trench system in particular all the fore arc sequences were strongly deformed some possibly for the first time e g in the fore arc basin and became firmly accreted to the continental margin moreover the magmatic foci migrated trenchwards to intrude the deformed rocks in the antarctic peninsula because many of the plutons were emplaced synkinematically they often closely resemble basement gneisses the distinction between these rocks remains a serious problem in the antarctic peninsula and it can be solved only partially by radiometric dating

late miocene vegetation of the pannonian basin abstract the pannonian basin system provides sufficient data to study local and regional vegetation in the context of palaeoclimate and palaeogeography the present study attempts to make use of the latest results in stratigraphy and track vegetation change throughout the late miocene vegetation layers are reconstructed for five time slices from 10 8 ma to 6 5 ma and placed in a palaeogeographic context plant functional types and their distribution frequently applied in ecological studies and biome modelling serve as a tool for reconstructing palaeovegetation units a classification system is introduced considering non zonal elements as well in order to represent the neogene floral record the pft spectra obtained from fossil leaf assemblages indicate the presence of mainly broadleaved deciduous vegetation throughout the regarded time span with variable diversities of conifers and broadleaved evergreen vegetation components during the late miocene the lowland vegetation of the pannonian realm seemed to be more homogeneous than reported in other reconstructions which is in line with the persistence of overall warm and humid climate conditions the existence of distinctly dry periods as partly suggested by other proxies is not supported at the same time data suggest the coeval declining trend of the broadleaved evergreen component in the study area and its final complete disappearance from the north of the pannonian basin in the younger time slices constantly humid conditions might have existed along the northern border of the lake possibly connected to uplift pulses of the alps and carpathians

cenozoic continental climatic evolution of central europe continental climate evolution of central europe has been reconstructed quantitatively for the last 45 million years providing inferred data on mean annual temperature and precipitation and winter and summer temperatures although some regional effects occur the european cenozoic continental climate record correlates well with the global oxygen isotope record from marine environments during the last 45 million years continental cooling is especially pronounced for inferred winter temperatures but hardly observable from summer temperatures correspondingly cenozoic cooling in central europe is directly associated with an increase of seasonality in contrast inferred cenozoic mean annual precipitation remained relatively stable indicating the importance of latent heat transport throughout the cenozoic moreover our data support the concept that changes in atmospheric co2 concentrations although linked to climate changes were not the major driving force of cenozoic cooling

the neogene of eurasia spatial gradients and temporal trends the second synthesis of neclime article i nfo this volume represents the second synthesis of the international open research network neclime neogene climate evolution in eurasia that was established in 2000 to study climate change in eurasia during the neogene and its impact on ecosystems the main objectives of neclime research are 1 proxy data based quantitative reconstructions of neogene climate in eurasia by means of standardised techniques 2 the modelling of atmospheric and oceanic circulation and of biomes using neogene boundary conditions and 3 the analysis of the interaction between palaeogeography vegetation and climate presently 94 scientists from 34 countries are neclime members contributing with their published data to a collective data base integrating proxies from various sources such as palaeobotany vertebrate palaeontology and geology the following core topics are addressed in the volume precipitation patterns and landscape opening the asian monsoon systems the potential of past climates for the evaluation of future climate change scenarios as well as short term change and variability of climate highlights of the single contributions are summarised in a proxy data section and in a modelling section respectively it is shown that the integrative approach presented in this volume brings about a much better and much more detailed understanding of neogene climate dynamics in eurasia than previously achieved even though neogene climate changes may have regional aspects differing considerably from each other and from the general global trend the results from the various proxy and modelling studies consistently show that later neogene cooling implicated more pronounced latitudinal and longitudinal gradients on the other hand the issue reveals a number of problems and questions resulting from the contrary nature of palaeozoological and palaeobotanical palaeoclimate proxies and modelling results mainly at a more regional level the models can not yet explain the relatively warm high latitudes during the neogene and we still do not sufficiently understand the role of the various boundary conditions such as co2 palaeogeography and palaeovegetation in the observed neogene climate change and its regional differentiation these apparent uncertainties underline the importance of the study of palaeo scenarios in order to enhance the reliability of future climate projections

ocean surface patterns above sea floor bedforms as recorded by radar southern bight of north sea abstract airborne radar observations of the southern bight of the north sea have revealed sea surface patterns that reflect a constructional sea floor topography of tide built sand waves and sand ridges the patterns result from local horizontal differences in the amplitude of water surface waves with wavelengths less than 1 cm such modulations result from surface convergences and divergences as the water flows across structures on the ocean floor three sand ridges were observed which form a topological series defined by side slope asymmetry and sand wave pattern depth appears to be the controlling variable with shallow water leading to the steepest slopes most intense asymmetry and the most marked separation of sand waves into ebb and flood dominated domains

a late miocene climate model simulation with echam4 ml and its quantitative validation with terrestrial proxy data abstract for the tortonian late miocene 11 to 7 ma we present a model simulation using the atmospheric general circulation model agcm echam4 coupled to a mixed layer ml ocean model the tortonian simulation with echam4 ml includes an adjusted weaker than present ocean heat transport a generally lower palaeorography and an appropriate palaeovegetation we analyse the climatic differences between the tortonian run and the present day control experiment and we validate our tortonian model results for the mean annual temperature and the annual precipitation with quantitative terrestrial proxy data globally the tortonian run is slightly warmer 0 6 c and the global precipitation indicates more humid conditions 27 mm a than the pd control run particularly the northern high latitudes are warmer 3 5 c in the tortonian simulation which leads to a weaker meridional temperature gradient than today as well as to a reduction of polar sea ice we attribute the polar warming to the lowering of the greenland elevation 20 c in the miocene and to the effects of the palaeovegetation the reduced altitude of the tibetan plateau causes a warming 20 c as compared to today and leads to a weaker asian monsoon in the tortonian run for europe the mean annual temperature is almost unaffected as compared to today because a cooling effect of the weak palaeocean heat transport is compensated by the palaeovegetation when validating our model results we find that the tortonian run is largely consistent with quantitative proxy data however the high latitudes tend to be generally too cool in the palaeoclimate simulation and the equator to pole temperature gradient is too steep as compared to proxy data for europe the comparison with proxy data indicates that the tortonian simulation underestimates the mean annual temperatures but precipitation patterns are quite consistent between model results and proxy data overall the tortonian run is quite realistic and hence the model simulation contributes to a better understanding of the relevant climate processes in the miocene however the discrepancies to proxy data demonstrate that we still do not sufficiently understand the late miocene climate

sun glitter imaging of submarine sand waves on the taiwan banks determination of the relaxation rate of short waves natural science foundation of china 40476023 40876031 chinese ministry of science and technology 2009cb421205

paleogene temperature gradient seasonal variation and climate evolution of northeast china abstract continental paleogene climates have been well studied in europe and north america but very little is known from asia because paleoclimatic results have only been reported from particular geological intervals here based on 29 plant assemblages from 8 well age controlled fossiliferous sites we quantitatively reconstruct the climates through most of the paleogene of northeast china and discuss related seasonal variations our results demonstrate that the mean annual temperature mat gradient was fairly shallow 0 27 c 1 latitude during the paleocene throughout this region in the eocene seasonality was high in the region indicated by marked differences in both temperature and precipitation between winters and summers of the sites the paleo east asian monsoon must have had intensified at least in the late mid eocene shown by apparent differences in annual precipitation distribution at all the sites regarding the paleogene climatic evolution of northeast china our quantitative results suggest that mat overall declined from warm in the paleocene and eocene to moderate in the oligocene generally consistent with the trend of marine records but with some distinctions two significant cooling events are recognized in the early and mid eocene with mat 3 4 c and 3 8 c lower and winter temperature 5 8 c and 4 7 c lower respectively in similar magnitudes to corresponding variations in europe and north america furthermore the present results show that mat rebounded in the late mid eocene and then decreased until the oligocene a similar pattern demonstrated in europe during the mid eocene to oligocene interval

late miocene washhouse climate in europe abstract we present two eight million year long proxy records of precipitation for southwest and central europe covering the middle to late miocene 5 3 13 ma at a temporal resolution of about 60 kyr and 150 kyr respectively the estimates of precipitation are based on the ecophysiological structure of herpetological assemblages amphibians and reptiles from 13 0 ma until about 9 ma both records show a similar trend evolving from a long dry period 13 11 ma into a washhouse climate 10 2 9 8 ma characterized by global warm conditions and several times more precipitation than present the transition from washhouse to a dryer climate between 9 7 and 9 5 ma and the concomitant cooling episode appear to have triggered a severe biotic event known as the vallesian crisis which included the extinction of hominoids in western europe a second washhouse period 9 0 8 5 ma coeval with a global warm episode was unprecedentedly intense in southwest europe but less pronounced in central europe from 8 ma onward a divergence in the two precipitation records is observed with southwest europe staying wetter and central europe becoming dryer than present both precipitation records are combined into a common run off curve as a measure of the relative intensity of the hydrological cycle for moderate latitudes of continental europe the run off curve shows a remarkable positive correlation with atlantic deep water temperatures from ceara rise by lear et al 2003 which are significantly higher up to 3 c during the two washhouse periods and show no other positive excursion of comparable magnitude we discuss potential links and the role of the coeval temporary restriction of the central american seaway on ocean and atmosphere circulation

an improved composite surface model for the radar backscattering cross section of the ocean surface 2 model response to surface roughness variations and the radar imaging of underwater bottom topography in the companion paper we have presented an improved composite surface model for the calculation of normalized radar backscattering cross sections nrcs of the ocean surface the proposed model accounts for the impact of the full two dimensional ocean wave spectrum on the radar backscatter and was shown to reproduce measured absolute nrcs values for a variety of radar configurations and wind speeds satisfactorily after some reasonable tuning of the input ocean wave spectrum this paper focuses on the modulation of the nrcs in the presence of spatially varying surface currents first the sensitivity of the nrcs to intensity variations of different ocean wave spectral components is investigated then the hydrodynamic modulation of the wave spectrum over underwater bottom topography in tidal waters is computed in different ways and the resulting radar signatures are discussed the composite surface model yields comparable radar signatures at high 10 ghz x band and low 1 ghz l band radar frequencies which is in much better agreement with experimental results than the predictions of a first order bragg scattering model on the other hand measured variations of the nrcs at high radar frequencies appear to be still underestimated in some cases which may be due to shortcomings of our description of the wave current interaction by conventional weak hydrodynamic interaction theory possible improvements of the theory are discussed and requirements for future experiments are formulated

crustal growth of the antarctic peninsula by accretion magmatism and extension a subduction accretion model incorporating new geophysical data is presented to explain the geology of the antarctic peninsula from late palaeozoic to cenozoic time according to the model the peninsula consists of overlapping accretionary magmatic and extensional regimes that were diachronous across the peninsula and have built the crust to its present form the crust which contains a small proportion of sialic basement was mainly formed by accretionary and magmatic processes and modified to its present shape by extension the gondwanide orogeny for the antarctic peninsula is interpreted in terms of the accretionary processes

quantification of calabrian climate in southern primory e far east of russia an integrative case study using multiple proxies abstract early pleistocene climate dynamics in the russian far east southern primory e is studied using multiple quantitative techniques on various palaeobotanical organ types climate data of the time were obtained from a total of 8 macrofloras fruits and seeds woods and leaves and 18 microfloras collected from a 10 m thick terrigenous succession exposed in the pavlovskoe brown coal field according to magnetostratigraphy the studied section covers the last 200 kyr of the calabrian and comprises the early late pleistocene transition a crucial time span involving the transition from obliquity forced cyclicity to the strong eccentricity triggered glacial events in this first integrative study on palaeoclimate of the russian far east we employ growth ring analysis multivariate anatomical analysis leaf margin analysis climate leaf analysis multivariate program and coexistence approach on the different organs partly originating from the same layer the investigation documents the following important outcomes 1 climate data obtained from the various methods are proven to be largely consistent 2 the late calabrian of the southern primory e was characterized by overall cooling and drying our climate record displays 2 small scale cycles warm peaks at 19 4 19 8 and 14 0 14 8 m are tentatively correlated to the global isotope stages mis 25 and mis 21 respectively 3 in the warm phases the calabrian climate of southern primory e was significantly warmer and wetter when compared to the present especially regarding the cold season while in cold phases climate was similar to modern or event slightly cooler 4 as of today early pleistocene climate of southern primory e was warmer and wetter than neighboring areas of the south rfe 5 the effect of the east asian monsoon systems on the climate of the southern primory e was less pronounced compared to the present

a sand wave field in the entrance to bahia blanca estuary argentina abstract sand waves in the mouth of the bahia bllanca estuary show differences in wavelength crestlength and crest shape characteristics between two sectors of the field these differences may be explained by assuming that the residual ebboriented currents are stronger in the southern sector crest bifurcations on the centerline are suggestive of intermediate energy conditions and the development of secondary flows oblique to the main current direction the large lee slopes and the presence of megaripple fans are indicative of flow separation a condition seldom mentioned for subtidal sand waves boundaries of the sand wave field may be controlled by the thickness of the surficial sand layer rapid reduction of the water depth as produced by a large marginal shoal and variations in grain size an average migration rate of 33 m yr 1 was calculated from repeated bathymetric surveys assuming that sand waves preserve shape and size the established net sediment flux over the crests is 0 025 cm3 cm 1 s 1 current measurements made during four individual tidal cycles yielded a net bedload sediment transport of 0 048 cm3 cm 1 s 1

planation surfaces of the armorican massif western france denudation chronology of a mesozoic land surface twice exhumed in response to relative crustal movements between iberia and eurasia the armorican massif an extensive outcrop of variscan basement in western france is shaped by several planation surfaces of debated origin and age we propose an evolution model for these landforms and their deformation based on detailed mapping of the planation surfaces their relative chronology and their relationships with dated outcrops of sediments and weathering products the armorican landscape consists of six stepped planation surfaces labelled ps1 to ps6 later incised by two successive river networks these landforms are pediments and pediplains or polygenic landforms armorican planation surface ps5 resulting from two periods of etchplanation these planation surfaces are mostly pre late cretaceous in age based on the age of the sediments overlapping these pediments the three older ones ps1 to ps3 are pre pliensbachian 191 183 ma ps4 is pre bajocian 170 168 ma ps5 here called the armorican planation surface is polygenic and ranges from the base of the early cretaceous to the base of the bartonian 140 40 ma and the youngest ps6 which is poorly constrained is older than 40 ma base of the bartonian or 15 ma base of the middle miocene most of these old landforms are exhumed i e they were buried by sediments and later re exposed by denudation at least two phases of burial and exhumation have been identified 1 burial in jurassic time followed by denudation during the early cretaceous and 2 burial in late cretaceous time followed by denudation during the latest cretaceous to early eocene the depth of burial is unknown but is probably low due to the small amount of coeval siliciclastic sediments in the surrounding basins the two periods of exhumation correspond to critical periods in the plate movements between africa iberia and eurasia the first is probably related to the initiation and breakup of the rift between iberia and eurasia and the second to the convergence between these two plates

the cenozoic cooling continental signals from the atlantic and pacific side of eurasia a b s t r a c t the evolution of cenozoic continental climate signals from the atlantic and pacific side of eurasia can be assessed for the first time by comparing climate records obtained for two mid latitudinal regions for the west a detailed climate record over the past 45 ma based on palaeofloras from two northern german cenozoic basins mosbrugger et al 2005 r evealed major trends and shorter term events throughout the cenozoic cooling thus testifying the close correlation of continental and marine temperature evolution as derived from oxygen isotopes zachos et al 2008 using the same methodology we analyze a total of 14 floral horizons originating from continental strata of southern primory e russia in order to study the evolution at the eastern side of the continent the primory e record spans the middle eocene to early pleistocene as the coeval record for the atlantic side it reflects major global signals of cenozoic climate change such as the temperature decline throughout the late eocene coinciding with the growth of antarctic ice sheets warming during the mid miocene climatic optimum and step wise cooling throughout the later neogene the comparison of both records reveals differing regional patterns the considerable longitudinal temperature gradient currently existing between both study areas already began to evolve during the aquitanian and was very significant during the mid miocene climatic optimum the temperature offset between east and west is likely attributable to an effective north atlantic current already operational from the late early miocene onwards bringing about mild winters and low seasonality in western europe while in primory e seasonality steadily increased from the late oligocene on the strong late pliocene decline of cold month mean temperatures recorded in primory e is supposed to coincide with the establishment of the siberian high as semi permanent structure of the northern hemisphere circulation pattern when comparing the precipitation records obtained for both study areas an unexpected co variability at the longer term in the order of 5 20 ma is noted pointing to continent wide hydrological changes the steady decline of mean annual precipitation in the primory e record beginning in the bartonian and culminating in the aquitanian coincides with an aridity increase reported from coeval chinese inland localities of the mid latitudes the seasonality patterns of rainfall point to progressive intensification of the east asian summer monsoon in primory e since the later tortonian while the post zanclean decline of the precipitation of the dry season can be related to an increasing impact of the winter monsoon 2015 elsevier b v all rights reserved

late palaeozoic early mesozoic fore arc basin sedimentary rocks at the pacific margin in western antarctica we infer that the trinity peninsula group of the antarctic peninsula was deposited in a fore arc basin s of composite type located between the gondwanian arc massif consisting of plutonic and older gneissose basement rocks and a subduction complex now represented by greenschists blueschists and albite epidote hornblende bearing rocks of the pre jurassic metamorphic complex

intermittent turbulent events over sandy current ripples a motion picture analysis of flume experiments abstract a series of laboratory flume experiments was conducted in order to elucidate sediment transport processes over sandy current ripples instantaneous cinematography capable of recording up to 30 frames per second was employed to trace the coherent trajectories of the sediment particles and flow analysis of channel side view images suggests that sediment behaviour over a fully developed current ripple can be categorized as distinct stages on both stoss and lee sides near the reattachment point on the stoss side sediment particles exhibit the following intermittent but coherent motions 1 impact of sediment laden fluid on the reattachment point 2 entrainment of particles 3 spiral like turbulent motion and 4 downstream dissipation of particles the sequential sediment behaviour is called micro scale kolk which is a key mechanism responsible for turbulent sediment entrainment over current ripples the salient features of boil were not observed in the crest and lee side region sequential images show the following characteristics 1 detachment of particles and fluid at the crest 2 entrainment and shielding of particles 3 avalanching and rolling of free shear layer and 4 downstream dissipation and recreation of a lee face segregation of heavy minerals was accomplished by successive avalanches along the lee slope and mixing vortices in the separation cell

paleoclimatic estimation reveals a weak winter monsoon in southwestern china during the late miocene evidence from plant macrofossils the late miocene xianfeng flora of yunnan province southwestern china was chosen to reconstruct the paleoclimate and the intensity of the asian monsoon three available quantitative climate reconstruction methods from fossil plants i e leaf margin analysis lma the climate leaf analysis multivariate program clamp and the coexistence approach ca were used in this study mats mean annual temperatures resulting from these three approaches i e lma 17 2 2 38 degrees c clamp 15 43 1 25 degrees c ca 17 2 21 7 degrees c appear to have been higher than the present 14 9 degrees c suggesting a much warmer climate in the late miocene both the growing season precipitation gsp from clamp 1908 7 217 7 mm and mean annual precipitation map from ca 1206 0 1613 0 mm estimates are higher than modern values 1003 2 mm gsp and 1038 mm map respectively indicating a more humid climate during the late miocene by comparing these with climates reconstructed from neighboring late miocene floras we conclude that the general late miocene climate appears warmer and more humid than present conditions in southwestern china furthermore the evident differences in estimated monthly temperatures between the summer and winter and precipitations between the humid and dry seasons indicate the existence of seasonality though not as strong as that of today difference in precipitation of dry season indicates a marked strengthening in the winter monsoon since the late miocene a new monsoon intensity index has also been defined based on precipitation seasonality to investigate the intensity of the asian monsoon c 2012 elsevier b v all rights reserved

turbulent flow over three dimensional dunes 2 fluid and bed stresses 1 dunes formed in response to fluid flow exert a total boundary stress on the fluid that is made up of form drag and skin friction the latter of which is generally considered important for predicting sediment transport and dune evolution previous research has used various methods to estimate the total stress and its subcomponents with recent work suggesting the application of a spatial average to the equations of motion a complete three dimensional 3 d form of this analysis is derived and applied to recent measurements of turbulent open channel flow over 3 d dunes spatial averages of reynolds shear stresses over 3 d dunes cannot be used to predict total boundary shear stress however estimations of total boundary shear stress from the spatially averaged equations of motion agree with not only the sum of form drag and skin friction but also the direct measurements of average free surface slope form induced stresses from secondary circulations augment the relatively low reynolds shear stresses over the 3 d dunes these low turbulence levels have ramifications for sediment transport predictions in that use of the total boundary shear stress in prediction of sediment transport over 3 d dunes must account for these low turbulence levels so as not to overpredict transport rates

measuring currents in a coastal inlet by advection of turbulent eddies in airborne optical imagery 1 water current vector fields in a coastal inlet are retrieved from temporal sequences of optical imagery collected from an aircraft the velocity being calculated by tracking modulations in the radiance from the surface the modulations are shown to be consistent with an advecting passive tracer in turbulent flow leading to the physical mechanism for this signature being turbulent eddies in the flow the intensity modulations are hypothesized to be light scattered from variations in the sediment load being transported by these turbulent eddies although other imaging mechanisms such as surface roughness variations may be occurring as well supporting evidence is the prevalence of the signature in sediment laden nearshore flows along an exposed coast and through a tidal inlet and eddy like variations in the echo intensity of acoustic doppler current profilers adcps also the 3 d frequency wave number spectrum of mapped image sequence data exhibits a classic shape that is consistent with surface turbulence generation by boils and subsequent mixing and advection by eddies in shallow channels the velocity vector is retrieved by the geometry obtained in the least squares fit of a 2 d planar surface representing advective variance in the 3 d spectrum these retrievals agree within 15 cm s root mean square rms with concurrent adcp measurements and within 2 cm s rms of measurements of the doppler shift of surface gravity waves that also are present in the data the method provides an important new capability for measuring currents over large areas of the littorals specifically including locations where waves are not present and visible variations in radiance from the water often are not strong

late miocene climate in the circum alpine realm a quantitative analysis of terrestrial palaeofloras abstract selected mega and microfloras from central and southern europe have been analysed for the time interval tortonian pannonian mn 9 12 with the coexistence approach to obtain quantitative palaeoclimate data the results give a geographically differentiated picture of the late miocene climate in the circum alpine area spatial patterns are presented in maps for mean annual temperature temperature of the coldest month temperature of the warmest month mean annual precipitation and mean annual range of temperature the obtained data show an overall warm humid and homogenous climate with very low latitudinal and longitudinal gradients there is no indication of a mediterranean type of climate palaeogeographic influences on climate patterns are evident the pannonian lake caused mild winters and a lower seasonality of temperature in the pannonian basin

the influence of deformation partitioning on dissolution and solution transfer in low grade tectonic melange dissolution of quartz and the recryst allization and re equilibration of phyllosilicates produce the dark anastomosing seams that dominate microstructures of tectonic melange which occur in a low grade imbricated and multiply deformed mid palaeozoic intracra tonic fiysch sequence in northeastern australia seams are composed of very closely spaced or coalesced cleavage lamellae which are very thin layers of extremely fine grained phyllosilicates cleavage seams enclose lenses of silt stone or greywacke which formerly occurred in continuous sedimentary layers indicating extremely heterogeneous and disruptive deformation microphacoids enclosed by cleavage seams have subtle shape asymmetries analogous to those of porphyroclasts phyllosilicate preferred orientations within microphacoids commonly lie at a low angle to enclosing seams and asymmetric relationships occur within seams the shape and fabric asymmetries appear to be constant and are regarded as analgous to s and c planes the number and extent of seams the amount of dissolution they indicate and the efficiency of deformation partitioning imply some enhancement of chemical activity and substantial silica loss from the system this in turn suggests the passage of large amount of silica undersaturated fluid and melanges may be zones of high fluid flow however the microstructures and the disruptive nature of the fabrics may also reflect the influence of high bulk shear strains and suggest some relationship between the shearing component of deformation and the development of cleavages and foliations

vegetation and climatic changes of sw china in response to the uplift of tibetan plateau abstract to understand the vegetation succession and climatic changes at the southeastern margin of the tibetan plateau in the neogene we reconstructed the middle miocene vegetation and climate based on palynological data from four localities which are at different latitudes along the ailao mountains in yunnan southwest china the palynological assemblages suggest that the vegetation there was composed of mixed evergreen and deciduous broad leaved forests growing under subtropical conditions based on the palynological data the palaeoclimatic parameters from the four localities are established the new parameters were compared with those of the late miocene of the late pliocene and of today the comparison revealed that the temperatures were obviously lower in the middle miocene than they are today this suggested that the ailao mountains were not high enough to block the asian winter monsoon in the middle miocene the middle miocene vegetation at the southeastern edge of the tibetan plateau was also compared to that of central tibet it would appear that the palaeoclimate at the southeastern edge of the tibetan plateau was warmer and wetter than in central tibet in contrast to the neogene cooling in central europe the climate at the southeastern edge of the tibetan plateau has gradually warmed since the middle miocene this phenomenon was most likely caused by the uplift of the tibetan plateau which has succeeded in blocking the asian winter monsoon since the middle miocene

types of internal structure and external morphology of submarine dunes under the influence of tide and wind driven processes dover strait northern france abstract the expression of tide and wind driven processes in the internal architecture and external morphology of very large submarine dunes is investigated at a dune field located in the central part of the dover strait southern north sea current measurements and sediment transport calculations enable quantification of the dominant tide and wind driven processes and very high resolution seismic recordings are used to analyse internal structure and external morphology of dunes in the study area moderate to storm winds induce temporary currents that can lead to the reversal of sediment transport direction and induced erosive processes on the seabed dune master bedding consists of extended erosive surfaces with 9 11 slopes that bound storm generated sets of cross beds 1 5 4 85 m thick 2 65 m on average three types of architectures are observed within the dune field and occasionally within single dunes these types which display a strong linkage between internal structure and external morphology consist of 1 asymmetric dunes with cosets which dip in the direction of the marked external asymmetry of the dunes 2 dunes with a complex external morphology composed of mega herringbone structures each displaying an opposing progradation direction and 3 dunes with a symmetric megaripple bedding unit at their summit the diversity of the internal architecture and external morphology results from the variable combinations of tide and wind driven processes occurring in the study area the asymmetry of tidal peak current velocity and the relative strength of wind driven currents are the parameters that have the most important influence on dune architecture asymmetric dunes with cosets result from a strong asymmetry in tidal peak current velocity which is reversed only slightly during storms dunes with mega herringbone structures and dunes with symmetric megaripple units at their summit are observed in areas where the asymmetry of the tidal peak current velocity is negligible allowing reversal of the sediment transport and dune migration directions each time moderate winds blow the latter architectural type is specific to sand rich areas the different dune architecture types display strong geometrical similarities to structures observed in dunes from other shelf environments where driving processes are different this implies that a study based only on a geometric description of internal structures will not enable the reconstitution of ancient depositional environments a better discriminant criteria seems to be the thickness of the second order sets of cross beds which is correlated with specific hydro sedimentary processes dune height also probably has an important influence on the thickness of second order sets of cross beds as dune height and set thickness display a clear relationship in the present study

radiometric evidence for the age of the subduction complex in the south orkney and south shetland islands west antarctica new k ar and rb sr data are presented for the age of part of the supposed late palaeozoic early mesozoic metamorphic complex in west antarctica here renamed the scotia metamorphic complex these results together with a review of other radiometric and palaeontological evidence fail to confirm a pre mesozoic age for the subduction complex in this region although rocks belonging to the albite epidote amphibolite facies could be as old as permian blueschists and greenschists from the south shetland is appear to be significantly younger and were probably formed in part at least during cretaceous subduction

macroturbulence generated by dunes fraser river canada abstract a selectable frequency acoustic profiler and electromagnetic current meter were deployed in the lower fraser river canada to examine large turbulent structures features were generated on the lower stoss sides of dunes and appeared at the surface tens of metres downstream as strong upwellings boils they were identified with acoustic clouds in the acoustic profile event recurrence periods measured from acoustic time series and from ejection events identified in the current meter record had similar two component frequency distributions but the acoustic values lacked the highest frequencies a comparison of measured periods with predictions from the strouhal law indicate that both dune amplitude and the internal boundary layer developed over the dunes are significant length scales associated with the generation of the macroturbulence our data give no support to the notion that boils develop from microturbulent bursts

lateral growth of the continental crust through deep level subduction accretion a re evaluation of central greek rhodope abstract the rhodope massif of northern greece and southern bulgaria has been variably interpreted as a fragment of pre alpine possibly hercynian or precambrian age continental crust that was actively involved in european margin convergent tectonics during the mesozoic and tertiary alternatively we propose that for central greek rhodope the lithological associations and tectonothermal history are consistent with progressive south directed mesozoic crustal growth through deep level subduction accretion a process which involved the near continuous transferral of material of oceanic and continental margin affinity from footwall to hanging wall within a north directed palaeotethyan subduction system central greek rhodope comprises a sequence of schists gneisses and migmatites of wide compositional variation that have undergone intense tectonic intermixing extensive occurrences of marble are associated with amphibolites variably retrogressed eclogites meta gabbros and ultramafic rocks quartzo feldspathic gneisses are abundant throughout the area and are associated with psammitic meta greywacke sequences pelites and quartzites the presence of intercalated marble slivers and thin manganiferous and iron rich siliceous bands is significant the various components exposed in the subduction accretion complex were first underthrust northwards to deep crustal levels subjected to high pressure eclogite facies metamorphism and underplated to the base of the overriding eurasian plate this latter accretion event was characterised by intense southwest directed ductile thrusting and pervasive amphibolite facies metamorphic overprinting it was accompanied by migmatisation and intracrustal melt generation and followed by subduction related magmatism deep level subduction accretion leads to southward growth of the continental margin which in turn leads to subduction retreat allowing the encroachment of the magmatic arc from the north subsequent extensional tectonic exhumation brought the complex up to its present position within the southern margin of eurasia this new interpretation may have implications for other high grade terrains within convergent and collisional systems that have been assumed to represent ancient or pre existing continental crust if so then the importance of deep level subduction accretion as a mechanism of continental crustal growth has hitherto been underestimated