oxygen and carbon isotope signatures in late neogene horse teeth from spain and application as temperature and seasonality proxies abstract here we describe a data set of 249 stable o and c isotope compositions from fossil horse teeth from the upper neogene of central spain and discuss their potential as environmental proxies it has been shown before that horse tooth enamel 18 o is a good proxy for local meteoric water 18 o h2o which in turn bears a distinct relation to temperature during precipitation formation at mid to high latitudes we discuss the reconstructed 18 o h2o values and apply modern 18 o h2o temperature equations for the iberian peninsula to these values results for the early pliocene suggest mean annual temperatures up to 2 3 c higher than today fitting pollen based estimates fairly well temperatures 5 c higher than today are predicted for the early late miocene 11 9 ma these estimations are feasible given the local occurrence of crocodilians and the presence of fruit eating hominids in iberia at that time the estimated amount of cooling since then is similar to the estimated decrease in nw europe based on plants the stable carbon isotope record indicates the virtual absence of c4 plants pointing to an environment consisting of c3 plants under slightly water stressed conditions the long term 13 c trend follows the expected decrease in average global 13 c co2 predicted from planktonic foraminifers within tooth variability is supposed to reflect seasonal change but the amplitude is expected to have been significantly damped by internal time averaging effects related to the mixing with atmospheric o 2 reservoir dynamics enamel maturation and sampling procedure the exact degree of damping is difficult to estimate but theoretical considerations suggest values between 50 and 75 depending on temporal resolution and element used c o reconstructed seasonal temperature ranges for central spain are equal or slightly less than the modern range within tooth 13 c variation is more difficult to explain as it can be attributed to multiple factors such as intra annual changes in 13 c co2 micrometeorology plant response and diet the occurrence of both positive and negative intra tooth 18 o 13 c correlations may be related to orbitally forced variations in seasonality

iberian micromammals show local extent of vallesian crisis abstract once perceived as a continent wide extinction event doubts have been raised as to the severity and extent of the vallesian crisis in this paper we use the high resolution late aragonian to middle turolian micromammal record from both the coastal valles penedes basin and inland calatayud teruel complex to determine geographic extent of this late miocene turnover event and its effects within the reaches of the iberian peninsula differences in faunal composition between the two regions confirm that the event was much less severe than previously thought surprisingly the diversity peaks in the two regions do not coincide whereas at the coast highest diversity is found in the early vallesian just before the turnover in the inland it peaks in the late vallesian several taxa never made it inland as reflected by the low similarity between both regions during the early vallesian suggesting that the valles penedes was indeed unique and consistently showed higher affinities with northern regions the large differences even at relatively short distances support the idea that the vallesian crisis was a local event

one hundred million years of geomagnetic polarity history since 1968 absolute ages have been assigned to the late cretaceous cenozoic geomagnetic reversal time scale by fixing the ages of two or more calibration points in a composite marine magnetic anomaly profile and interpolating between or extrapolating beyond these points assuming constant spreading rates in each interval previously no more than 4 calibration points were used but it is now possible to specify 11 calibration points in addition to the 0 m y datum this improvement is based on magnetostratigraphic studies in italian pelagic limestones these studies closely tie the geomagnetic reversal sequence to the foraminiferal and coccolith zonations absolute ages of calibration points are provided by the best available dates on stage boundaries which are located from the biostratigraphic zonation the greatest changes from previous scales come in the late paleocene early eocene where the new ages are as much as 3 m y younger than in the 1977 scale of labrecque and others and as much as 1 8 m y younger than in the 1980 scale of ness and others

impact of global climate in the diversity patterns of middle miocene rodents from the madrid basin spain abstract remarkable palaeoclimatic global changes have been recorded worldwide during the middle miocene the miocene climatic optimum 16 3 to 15 ma one of the warmest phases since the eocene was followed by the stepwise cooling trend of the middle miocene climate transition 15 to 13 7 ma the entry into an earth ice house climate state took place at the end of the latter 13 76 ma marked by one of the major cooling steps in middle miocene climate recorded at a global scale mi3b event the madrid basin which is part of one of the main cenozoic basins of the iberian peninsula contains a well represented small mammal record from the lower middle miocene to the upper middle miocene middle and upper aragonian 15 9 to 12 8 ma being an appropriate region to check how these climatic phases influenced the distribution of the mammalian faunas on the center of the iberian peninsula values of species richness equitability and heterogeneity of rodents have been calculated for 25 localities of the madrid basin and compared to detailed climate isotope records from the marine realm odp site 1146 from the south china sea and the mediterranean record of the ras il pellegrin section on the maltese islands and with palaeoprecipitation curves for southwest europe calatayud montalban basin the results show that the rodent community during the middle and upper aragonian in the madrid basin was subject to the changing climate conditions imposed in the course of the middle miocene the palaeoecological curves witness periods of disturbance of the community during changing climate conditions marked by important drops in equitability and in some cases gradual decreases in heterogeneity and species richness followed by periods showing a recovery of the community and adaptation to the new climate circumstances represented by more evenly distributed and diverse assemblages the effects of the miocene climate optimum and of three mi events mi2b mi3a and mi3b have been related to changes in the small mammal community between 15 8 and 15 3 ma the likely extreme environment high temperature and low precipitation of part of the miocene climate optimum may have imposed severe constraints on the fauna resulting in a community with low values of equitability heterogeneity and a decreasing number of species the transition of the miocene climate optimum to the middle miocene climate transition reflected by the mi2b event has also procured a destabilization of the rodent assemblages as an important drop in equitability is recorded between 15 and 14 6 ma in this interval the drop in temperature and increase in rainfall derived from the middle miocene climate transition promote the southwards migration of northern invaders leading to an increase in species richness in the madrid basin starting around 14 4 ma the onset of a progressive drop in the rodent equitability and heterogeneity which also coincides with a major stratigraphic discordance in the basin is related to the first cooling step of the middle miocene climate transition mi3a event finally the major cooling step in middle miocene climate recorded at a global scale mi3b event is poorly reflected in the palaeoecological curves however the taxonomical study of the rodent faunas of that interval biozone e has shown turnover rates and morphometric changes that indicate that this period represents one of the most variable in assemblage composition within the aragonian although the mi3b event has been correlated for a long time to the substitution of the early middle aragonian fauna by a late aragonian community e f boundary the study of the rodent assemblages of the madrid basin may point out that small changes in the small mammal community started before within biozone e

a new quantitative biochronological ordination for the upper neogene mammalian localities of spain abstract the mn scale is the most widely used biochronological scale for the mammalian fossil record of europe but at the same time it has brought a high amount of criticism with it the fossil record of neogene macromammals from spain is one of the most complete of the world and provides an interesting test of the mn biochronology we used maximum likelihood appearance event ordination ml aeo a quantitative biochronological method to provide not only an ordination but also a numerical age estimate for each of the 90 macromammalian fossil faunas that constitute our data base originally only 13 of these localities were numerically dated mainly by means of paleomagnetism the ordination of macromammalian fossil faunas matches quite well with the mn chronology at least in the miocene the pattern of ordination is less coherent in the pliocene partly due to the relative poverty of macromammalian fossil sites of this age in spain the controversy on whether the age of the first appearance of hipparionine horses in the iberian peninsula hipparion dispersal event was around 10 8 10 7 ma or 11 1 ma is discussed our estimated mn7 8 mn9 boundary lies between 11 008 and 10 873 ma we conclude that the arrival of hipparionine horses in the iberian peninsula happened between these two ages and that the oldest record is found in the locality of nombrevilla 1 with an age of 10 873 ma

10 be in ice at vostok antarctica during the last climatic cycle we have previously reported accelerator mass spectrometer measurements of the cosmogenic isotope 10be half life 1 5 myr in an 906 m ice core recovered at dome c antarctica1 in addition to an enhanced concentration during a period of reduced solar activity maunder minimum ad 1645 1715 2 we found substantially increased concentrations during that part of the core corresponding to the last ice age both effects have been confirmed and extended in greenland ice cores3 4 the recovery of a 2 083 m ice core at vostok antarctica5 together with an extended oxygen isotope chronology reported elsewhere in this issue6 permits an extension of 10be studies over the whole of the last climatic cycle 125 kyr we report here such measurements which show an excellent correlation with the oxygen isotope and thus presumably climate record over the whole of this period the results imply that precipitation rates in the antarctic during the last interglacial were similar to those of the holocene but were roughly halved during the last glaciation

review of paleo humidity parameters in fossil rodents mammalia isotopic vs tooth morphology approach paleoecology of fossil rodents is frequently inferred from the dental pattern of the teeth attributing the habitat conditions of extant rodents to fossil species with similar dental pattern this technique is common practice and has been in use for several decades a relatively new technique is based on the carbon and oxygen isotope composition of the incisor enamel of fossil rodents to reconstruct paleoenvironmental scenarios we combine these two methods studying material from two early miocene spanish sections one in the mediterranean coastal area and one in northcentral inland spain comparison of the humidity values obtained by means of these two proxies reveals discrepancies therefore we analyzed the habitat preferences especially humidity of extant rodents and found that dental pattern is not very reliable to reconstruct the humidity preferences of fossil rodents and this kind of interpretation has to be taken with caution we conclude that the isotopic composition of enamel of fossil teeth is a more reliable proxy in the studied sections

isotopic paleoecology of mammals and the middle miocene cooling event in the madrid basin spain abstract the middle miocene underwent profound climatic perturbations detected in worldwide marine and continental records the miocene climatic optimum 17 to 14 ma a warm and humid period was followed by the middle miocene cooling 14 13 8 ma characterized by a sharp drop in temperatures and an increase in aridity triggered by the reestablishment of the eastern antarctica ice sheet the madrid basin located in the central iberian peninsula has furnished a considerable number of miocene fossil sites with a very complete succession of localities from the lower middle miocene to the upper middle miocene middle and upper aragonian mn5 and mn6 local zones db to g mammalian fossil tooth enamel of different taxa including rhinoceros equids gomphothere suids and ruminants from 16 fossil sites spanning from 15 9 ma to 13 2 ma were analyzed for 13c 18oco3 and 18opo4 values with the aim of determining regional paleoecological paleoenvironmental and paleoclimatic changes across this important climate transition the 13c values vary between 11 9 and 6 4 vpdb indicating a c3 environment ranging from woodlands to more open conditions the rhinoceros alicornops simorrense and hoploaceratherium tetradactylum the gomphothere gomphotherium angustidens the cervid heteroprox moralesi and the paleomerycid triceromeryx pachecoi may be regarded as browsers inhabiting more closed environments whereas the equid anchitherium the rhinoceros hispanotherium matritense and the bovid tethytragus langai show a mixed feeding diet related to more open conditions furthermore the variation in 13c values across the fossil sites and local zones indicates drier conditions in local zones db and dc 15 9 14 8 ma a more humid period in local zone dd 14 8 14 1 ma before a return to a drier environment in local zones e f and g 14 1 13 2 ma the 18oco3 and 18opo4 values and calculated 18ow values all track a declining trend from local zones db to dd 15 9 14 1 ma with minimum values in local zone e 18oco3 26 5 2 1 18opo4 18 4 2 4 and 18ow 5 3 2 9 the minimum in 18o values in local zone e 14 1 13 7 ma appears to coincide with a drop in temperature at the time of the middle miocene cooling 14 13 8 ma after this minimum 18oco3 18opo4 and 18ow values recover in local zones f and g 13 7 13 2 ma the calculation of 13cleaf values allowed us to determine plausible biomes that might have existed in the madrid basin during the middle miocene i e a tropical rain forest a tropical deciduous forest a temperate evergreen forest and a xeric woodland scrubland although this method was not able to detect more savanna like environments finally 13cdiet meq values were used to infer mean annual precipitation with values ranging from 250 mm yr local zone dc to 670 mm yr local zone dd which are in accordance with the proposed biomes suggested by the 13cleaf values and fossil mammal assemblages

management of ambiguities in magnetostratigraphic correlation abstract magnetostratigraphy is a powerful tool to provide absolute dating of sediments enabling robust and detailed chronostratigraphic correlations it is based on the correlation of a magnetic polarity column observed and measured in a given sediment section to a magnetic polarity reference scale where polarity changes are well dated via other independent methods however magnetostratigraphic correlations are loose as they are only constrained by binary magnetic chrons i e normal or reversal and their thickness which are both defined from depth variations of the magnetic remanent directions the thickness of a given magnetic polarity zone is a function of time and sediment accumulation rate which may not be stationary leading to ambiguities when performing the correlations to address these ambiguities a numerical method based on the dynamic time warping algorithm is proposed magnetostratigraphic correlations are computed in order to minimise the local variation of the accumulation rate the main advantage of the proposed method is to automatically provide a set of reasonably likely correlations this set can then be scrutinised for further analysis and interpretation however the likelihood of a correlation should be handled carefully as it depends on the information content of the magnetostratigraphic section itself and remain ultimately valid by ancillary constraint nevertheless the method gives consistent results on difficult synthetic cases that simulate abrupt variations of the sedimentation rate insights on true sections debated by previous authors are also given

a new chronology for the middle to late miocene continental record in spain abstract the first detailed chronology for the middle to late miocene continental record in spain is presented based on high resolution magnetostratigraphic data of mammal bearing sections which were studied in several basins calatayud daroca teruel valles penedes duero and jucar cabriel our results indicate that these sections compose an almost complete magnetostratigraphic succession from the lower aragonian mn4 to the middle turolian mn12 seven successive mammal neogene mn zone boundaries are directly dated in these sections which often contain faunas of two successive zones in superposition the three oldest boundaries are dated in the aragonian type area calatayud daroca basin the mn4 mn5 boundary vargas section occurs in chron c5cr o with a corresponding age of 17 26 0 01 ma the mn5 mn6 boundary aragon section in chron c5acn 0 8 with an age of 13 75 0 03 ma and the mn6 mn7 8 boundary aragon section in the interval c5ar 1n c5ar 3r with an age of 12 75 0 25 ma the mn7 8 mn9 aragonian vallesian boundary occurring in chron c5r 1n at 11 1 ma and the mn9 mn10 boundary in chron c4ar 3r at 9 7 0 1 ma are recorded in the valles penedes basin vallesian type area and are supported by the results from the duero basin torremormojon section in the turolian type area teruel basin the mn10 mn11 vallesian turolian boundary la gloria section occurs in chron c4an y at 8 7 0 1 ma taking into account the pre existing data from the jucar cabriel basin the mn11 mn12 boundary cabriel valley section is recalibrated to c4n 1n at an age of 7 5 0 1 ma

plant and micromammal based paleoprecipitation proxies comparing results of the coexistence and climate diversity approach abstract both plant and vertebrate communities have been used to reconstruct paleoprecipitation however direct stratigraphic comparisons between the two types of proxies have hardly been performed which is due to the fact that plant and vertebrate fossils usually do not occur together in single geological beds here we focus on a series of 18 sites from the neogene of europe and anatolia that contain both types of fossils and compare paleoprecipitation predictions produced by the coexistence approach plants and the climate diversity approach micromammals most of the sites have overlapping uncertainty intervals for mean annual precipitation as generated by the two methods pointing to a common precipitation related signal in flora and fauna nevertheless a systematic difference appears to characterize drier sites for which micromammal richness based estimates for annual precipitation tend to be lower than plant based coexistence based estimates driest month precipitations are in agreement for drier sites but strongly differ for wetter sites with micromammal richness based estimates being higher overlap is poor for estimates of wettest month precipitation which are higher when based on plant based coexistence possible sources for a bias towards higher annual values in plants are related to the inclusion of local wetland elements in the analysis and or to a lower taxonomic resolution for pollen and spores compared to macroflora micromammal based annual estimates could be biased towards drier values when smaller samples lack rare species that could be preferentially wet adapted several of the higher driest and lower wettest month micromammal based estimates could result from over extrapolation beyond the calibration domain for arboreality as currently existing in the modern western old world on the other hand the use of several se asian reference taxa could add a high precipitation monsoonal component to the plant based predictions in addition wettest month estimates for both plants and micromammals probably suffer from the poor performance of water excess as a limiting factor an attempt to further increase the predictive power of the micromammal based prediction equations was performed by incorporating non linear terms and by using an extended calibration set including selected plant based precipitation estimates for micromammal assemblages without modern analogue in the western old world proxy inter calibration

biogeographic provincialism in rodent faunas from the iberoccitanian region southwestern europe generates severe diachrony within the mammalian neogene mn biochronologic scale during the late miocene abstract in order to develop paleoecological studies involving many fossil sites there is a need to establish a consistent time framework which enables us to arrange the fossil associations according to a sequence of biotic events and subsequently to test a relationship with paleoenvironmental changes the nature of the continental fossil record has given rise to much controversy with regard to the establishment of general biostratigraphical scales additionally biochronological scales are sometimes all that can be proposed the primary goal of the present paper is to present a time arrangement for the iberoccitanian micromammalian fossil sites from the latest middle miocene to the mio pliocene boundary spanning around 7 million years approximately 12 61 4 95 ma herein we study over one hundred faunal lists of rodents from the iberoccitanian region compiled from the literature previous research has described two biogeographical provinces in our study area a northern one valles penedes and southeast france and a southern one all the iberian basins except the valles penedes we therefore conducted alroy s maximum likelihood appearance event ordination ml aeo methodology applying it to the database compiled for each province finally using available numerical dates for a quarter of the sites we obtained a calibrated ordination for all localities in each analysis the results obtained are roughly coherent with the mammalian neogene units mn and allow estimation of the numerical ages for the entire set of fossil sites included in the study nevertheless our results show severe diachrony between the two biogeographic provinces of the iberoccitanian region in relation to the mn boundaries which might be linked to the existence of a refuge area associated with more humid environments in the northern province

magnetostratigraphic calibration of the european neogene mammal chronology abstract this paper presents first a discussion on the status of the subdivisions of the european neogene mammal chronology and second it synthesizes all available magnetostratigraphic data from europe to provide chronological framework for mammal localities mammalian events and mammalian biochronologic units of the european neogene because of the lack of their rock equivalents the subdivisions of the european neogene based on mammals have not attained the stage status in terms of reliability except the vallesian and turolian therefore they are designated as the european land mammal ages elma magnetostratigraphic data on mammal bearing deposits in europe is still scarce in time and space consequently it is not yet possible to correlate accurately all elma and mn zones with the geomagnetic polarity time scale gpts nevertheless several studies dealing with mammal localities and their deposits around the oligocene miocene boundary in the middle and late miocene provide reliable correlations of some elma and mn zone boundaries thus the calibration of the oligocene miocene boundary at the base of chron c6cn 2n is in agreement with its age in marine deposits the well known hipparion datum astaracian vallesian boundary is now dated as about 10 8 ma occurring slightly above the base of chron c5n 2n this paper also reviews magnetostratigraphic correlations of some late miocene and pliocene mammal localities in the paratethys area taking into account the chronological assessments in other parts of europe for some key mammalian events new correlations with the gpts have been proposed for these localities thus some new ages are suggested for the late miocene and pliocene paratethys stages

strontium isotope variations in single ostracod valves from the gulf of carpentaria australia a palaeoenvironmental indicator the gulf of carpentaria is a shallow 70 m epicontinental sea which was partially and at times fully isolated from the ocean due to changing sea levels in the late quaternary in an attempt to elucidate the palaeoenvironment of this marine lacustrine system and hence constrain the rates of sea level changes high precision measurements 0 0036 of 87sr86sr ratios are reported for individual fossil ostracod valves these valves were extracted from two piston cores taken from the deepest part of the gulf of carpentaria single valves weighing 20 g 40 g and containing a total of 10 8 g to 2 10 8 g of sr have been analysed at the bottom of the main core in a depth interval equivalent to an age of 36 000 to 40 000 years valves from the ostracod species cyprideis have 87sr86sr ratios of from 0 70955 2 to 0 70967 2 sr 6 1 to 7 9 from 26 000 years to 22 000 years slightly higher but relatively constant 87sr86sr ratios of from 0 70998 2 to 0 71016 2 sr 12 2 to 14 9 are present the highest sr ratios are found in ostracod valves of 13 000 years age which have values from 0 71034 2 to 0 71039 2 sr 17 2 to 18 0 all these values are significantly greater than that of contemporary seawater and are indicative of continental sources with high 87sr86sr ratios significantly lower 87sr86sr ratios of from 0 70918 2 to 0 70961 2 sr from 0 8 to 7 0 are found in ostracods younger than 12 000 years and ratios identical to modern seawater 87sr86sr 0 70912 2 sr 0 0 are present in the upper 2 cm of core which is 5 000 years in age the variations in 87sr86sr ratios in ostracod valves from the carpentaria basin are consistent with a lacustrine environment from 36 000 years to 12 000 years followed by a transgressive marine sequence which commenced in the gulf of carpentaria 12 000 years ago this marine transgression was a result of sea level rising above the 53 m relative to present day sea level arafura sill sr isotope ratios identical to that of modern seawater were however only obtained when the 12 m torres strait sill was opened to the coral sea which occurred 8 000 to 7 000 years ago the marked decrease in sr isotopic ratios at the bottom of the core may be due to flow of the fly river from new guinea prior to its diversion into the coral sea or more probably a transitory input of marine water into the carpentaria basin during a relatively high sea level 40 000 years ago it is suggested that the highest asr values present 13 000 years ago reflect increased rainfall in the gulf area of northern australia which is attributed to a southwards migration of the monsoonal rainfall pattern at that time in contrast to some other chemical indicators of palaeoenvironments the asr results of this study provide definitive and unambiguous resolution of marine versus non marine environments and can thus be used to resolve with great accuracy transgressive regressive sequences

neritic carbonate for six submerged coral reefs from northern australia implications for holocene global carbon dioxide abstract total contribution of six recently discovered submerged coral reefs in northern australia to holocene neritic caco3 and co2 is assessed to address a gap in global budgets caco3 production for the reef framework and inter reefal deposits is 0 26 0 28 mt holocene co2 production is 0 14 0 16 mt coral and coralline algae are the dominant sources of holocene caco3 although foraminifers and molluscs are the dominant constituents of inter reefal deposits the total amount of holocene neritic caco3 produced by the six submerged coral reefs is several orders of magnitude smaller than that calculated using accepted caco3 production values because of very low production a give up growth history and presumed significant dissolution and exports the contribution of submerged coral reefs to global holocene neritic caco3 is estimated to be 0 26 0 62 gt which yields 0 15 0 37 gt of co2 this amount of co2 is 0 02 0 05 of the 780 gt added to the atmosphere since 18 kyr bp contributions from australian submerged coral reefs are estimated to be 0 05 gt caco3 and 0 03 gt co2 for an emergent reef area of 47 9 103 km2 based on the growth history of the submerged coral reefs in the gulf of carpentaria maximum global holocene caco3 fluxes could have attained 0 3 gt yr 1 between 11 and 7 ka bp this additional caco3 would have culminated in a maximum caco3 production from all emergent and submerged coral reefs of 1 2 gt yr 1 and neritic caco3 production of 2 75 gt yr 1 the dilemma remains that the global area and caco3 mass of submerged coral reefs are currently unknown it is inevitable that many more submerged coral reefs will be found our findings imply that submerged coral reefs are a small but fundamental source of holocene neritic caco3 and co2

bioclimatic analysis of rodent palaeofaunas reveals severe climatic changes in southwestern europe during the plio pleistocene abstract a recently developed method in palaeoclimatology bioclimatic analysis which makes it possible to extract a maximum of information from the available mammal proxy data is applied to a succession of fossil rodent assemblages recorded from the pliocene and pleistocene in the iberian peninsula it consists of both qualitative and quantitative models with the capacity to produce a detailed palaeoclimate reconstruction which is consistent with palaeobotanical and isotopic proxy data and the physics of atmospheric models using this method the palaeoclimate of the iberian plio pleistocene is reconstructed with high resolution from 44 fossil rodent assemblages comprising more than a hundred identified species analysis of these assemblages shows that the climatic evolution of the iberian peninsula during the plio pleistocene can be divided into four distinct climatic phases first a long phase of subtropical climate with summer rainfall and winter drought occurred during the ruscinian second between 3 4 and 2 5 my b p there was a cooling phase coincident with the development of the northern hemisphere ice sheets following this cooling a temperate interlude occurred between 2 5 and 1 8 my b p during this phase the mediterranean climate was established permanently in southwestern europe finally during the pleistocene temperate and colder stages were succeeding in relationship with the northern hemisphere glaciations this sequence of climatic changes is linked with the tectonic rising of the central asian and east african plateaus variations in the atmospheric circulation pattern and changes in the mediterranean sea surface temperatures all these factors led to associated changes in the precipitation regime and a latitudinal displacement of the zonal climatic belts

late quaternary environments of the carpentaria basin australia abstract quaternary variations in the level of the sea have exposed the shallow 29 000 km2 but shallow maximum depth s 4 0 kyr the pollen assemblages closely resemble the black soil plains presently found along the southern gulf thus the biogeographic and climatic barrier across the australia papua new guinea land bridge has remained largely intact in spite of the range of environmental conditions that have occured during the last

response of western pacific marginal seas to glacial cycles paleoceanographic and sedimentological features abstract this paper reviews the recent progress in late quaternary studies in five northwestern pacific marginal seas especially the south china sea as an example a series of marginal seas separate asia from the pacific ocean and significantly modify the material and energy flux linkage between land and sea during glacial cycles the sea level induced environmental signal was amplified in the marginal seas giving rise to drastic changes in areas and configurations of these seas and to reorganization of sea water circulation in basins since most of the western pacific marginal seas are influenced by monsoon circulation and some of these are located within the western pacific warm pool the glacial geographic changes have produced a profound impact on regional and global climate for example the decrease of sea area and sea surface temperature sst in the marginal seas was one of the factors responsible for the enhanced aridity of inland china during the glaciation glacial intensification of the winter monsoon and increased seasonality of sst in marginal seas might explain at least partly the apparent discrepancy between the tropical paleotemperature estimations based on terrestrial and open ocean records in this region as the western pacific marginal seas trap terrigenous material supplied by east asia the deep water sedimentation rates there can be one to two orders of magnitude higher than in the open ocean down slope sediment transport is more active when the sea level changes particularly during the deglaciation at least four types of carbonate cycles have been recognized in the western pacific marginal seas and each of those contains environmental signals from the surface and deep sea water as well as from the drainage basin

the antarctic ice sheet its history and response to sea level and climatic changes over the past 100 million years abstract the development surface form flow and erosive activity of the antarctic ice sheet over the past 100 million years is related to geological evidence that indicates long term trends of global climate the glaciological description of the evolution of the ice sheet covers its interactions with the atmosphere and with the ocean discussion focuses on changes of the equilibrium line altitude ela with time of the accumulation rate with global temperature and basal melting of ice shelves by ocean waters the tendency of global climate to change rapidly or to drift slowly between two near equilibrium states involves two types of changes the former that has been widely recognized is reversible a second type involving ice sheets or ice shelves appears to be almost irreversible since they remain in their changed state unless a much larger reversal of factors driving climate occurs we refer to any rapid but reversible changes as climatic jumps and to the latter as climate ice switches variability of climate in response to changing radiation with the earth s orbital parameters and other causes is included in our model extensive glaciation of east antarctica commenced after 40 m y b p with wide fluctuations until shortly after 20 m y b p a climate ice switch then prevented any major deglaciation a further climate ice switch associated with the ela falling below sea level occurred soon after 10 m y b p this led to rapid formation of ice shelves and the marine ice sheet of west antarctica which advanced as grounded ice to the edge of the continental shelf after 5 m y b p the grounded ice started to retreat extensive ice shelves remained and most glacial debris was then deposited beneath the inner regions of ice shelves response to northern hemisphere glaciation since 2 4 m y b p during glacial periods involved extension of the grounded ice area a large decrease of mass input and decreased melting of outer parts of large ice shelves while the melting rate beneath inner regions was probably similar to the present marine core evidence suggests that retreat caused by global cooling has been dominant since 5 m y b p and that changes in extent due to northern hemisphere glaciation since 2 4 m y b p have had different effects on the major and on smaller northerly ice shelves

late quaternary hydrological changes in the gulf of carpentaria the gulf of carpentaria is a shallow epicontinental sea between australia and papua new guinea fig 1 it has a maximum depth of 69 m and is connected to the arafura sea across a 53 m sill1 in the east the connection to the coral sea through torres straits is 12 m ref 1 we propose here that low sea levels during the pleistocene2 3 fig 2 resulted in subaerial exposure of the gulf of carpentaria thereby reducing the regional input of moisture and latent heat to the atmosphere and tropical cyclogenesis as a result the climate of the carpentaria basin may have been significantly drier than at present4 5 even so previous workers6 7 have reported the presence of lacustrine sediments in the gulf that could have been deposited when the sea level dropped below the 53 m contour1 during 1982 the extent of lake carpentaria was defined by high resolution seismic profiles and cores the size and development of lake carpentaria and its dependence on the hydrological balance are discussed below

going south latitudinal change in mammalian biodiversity in miocene eurasia for palaeontologists the challenge is to reconstruct biodiversity patterns of the past mammal richness in grids is used to assess the stability of biodiversity hotspots and document changes over time in europe for mammal neogene units 3 to 11 19 5 to 7 6 ma early to late miocene the maps clearly show the patchiness of the fossil record as the miocene was an eventful epoch with severe environmental changes europe slowly became drier and more seasonal both in temperature and precipitation from the early to middle miocene an area of high biodiversity moved from higher to lower latitudes culminating in one of the most remarkable hotspots in the history of mammals the early late miocene vallesian mammal stage faunas from the valles penedes catalonia spain remarkably the surrounding areas did not exhibit similar richness during the subsequent vallesian turnover event 9 7 ma the large and small mammal distribution became more equitable and the hotspots less prominent the richest area was found in the periphery of the humid miocene ecosystem which experienced species influx from the drier south the southward shift was a result of the expansion of the humid area with subsequent closed environments and related mixing of ecosystems coming to a halt in the late miocene when all of europe became equally open

new bioclimatic models for the quaternary palaearctic based on insectivore and rodent communities mammal remains preserved in archaeological and palaeontological deposits are commonly used to reconstruct past terrestrial climates and environments here we propose new species specific models for bioclimatic analysis a palaeoclimatic method based on a climatic restriction index for each mammal species discriminant analysis and multiple linear regressions our new models are based on small mammal associations particularly insectivores and rodents from quaternary paleoarctic contexts a dataset including new localities and an updated taxonomy was constructed in order to develop two approaches the first using only rodentia the second based on associations including both rodentia and eulipotyphla both approaches proved to be reliable for inferring both climate zone and quantifying temperature precipitation and seasonality rarefaction analysis revealed these new models to be reliable even when a substantial percentage of species from the original palaeocommunity was absent from the fossil site application of these new models to small mammal associations from two sequences balma de l abeurador france and el miron spain spanning from the last glacial maximum to the holocene are consistent with the primary climatic changes recorded by regional pyrenean proxies and showed an increase in mean annual temperature of between 3 and 5 c

age and correlation of a paleomagnetic episode in the western united states by 40ar 39ar dating and tephrochronology the jamaica blake or a new polarity episode high resolution paleomagnetic records from two sites near pringle falls oregon are compared with similar records from summer lake oregon 170 km to the southeast paoha island in mono lake 660 km to the southeast and benton crossing in long valley approximately 700 km to the southeast in east central california the sequences at pringle falls contain a distinctive coarse pumice lapilli tephra layer which we have dated as 218 10 ka by 40ar 39ar step heating of plagioclase feldspar stratigraphically this tephra is closely associated with a suite of several other tephra layers that bracket the interval studied paleomagnetically each tephra layer is distinguished by the unique chemical composition of its volcanic glass shards the pumice layer dated at pringle falls is correlated with layers at three of the other localities using all the tephra layers we can correlate the lake stratigraphic sequences and associated paleomagnetic records among the four distant localities additional age control is obtained from a fifth locality at tulelake in northern california where the stratigraphic interval of interest is bracketed between 171 43 and approximately 140 ka characteristics of the paleomagnetic records indicate virtually identical paleofield variation particularly the geometry of a normal to normal n n geomagnetic polarity episode the observed paleofield behavior resembles the blake geomagnetic polarity episode but is significantly older than the generally accepted age of the blake episode either the age of the blake episode is significantly underestimated or the polarity episode documented here is older perhaps the jamaica episode or is an as yet unreported episode a corollary of the latter option is that paleomagnetic polarity episodes of different ages may have similar transition polar paths a conclusion implying that a common mechanism is involved

holocene sea level change and coastal landscape evolution in the southern gulf of carpentaria australia a revised holocene sea level history for the southern gulf of carpentaria is presented based on new data from the south wellesley archipelago and age recalibration of previous research results confirm that rising sea levels during the most recent post glacial marine transgression breached the arafura sill ca 11 700 cal yr bp sea levels continued to rise to ca 30 m by 10 000 cal yr bp leading to full marine conditions by 7700 cal yr bp sea level reached present mean sea level pmsl and continued to rise to an elevation of between 1 5 m and 2 m above pmsl sea level remained ca 1 5 between 7000 and 4000 cal yr bp followed by rapid regression to within 0 5 m of pmsl by ca 3500 cal yr bp when placed into a wider regional context results from this study show that coastal landscape evolution in the tropical north of australia was not only dependent on sea level change but also show a direct correlation with holocene climate variability specifically the formation and preservation of beach rock deposits intertidal successions beach and chenier ridge systems hold valuable sea level and holocene climate proxies that can contribute to the growing research into lower latitude holocene sea level and climate histories

a new coral reef province in the gulf of carpentaria australia colonisation growth and submergence during the early holocene abstract multibeam sonar mapping drill cores and underwater video data have confirmed the existence of a previously unknown coral reef province in the gulf of carpentaria australia seven reefs comprised of coral limestone that support living corals have been mapped so far and as many as 50 other reefs may exist in the region u th ages show that reef growth commenced shortly after limestone pedestals were submerged by rising sea level around 10 5 kyr bp making them the oldest holocene reefs known in australia reef growth persisted for 2 0 kyr but it had ceased at most locations by 7 0 kyr bp measurements of reef growth rates 0 95 to 4 m kyr 1 indicate that the reefs were unable to keep pace with contemporaneous rapid sea level rise 10 m kyr 1 which is consistent with a give up reef growth history core samples from reef platforms demonstrate that pleistocene limestone is exposed at depths of 27 and 30 m below present mean sea level these depths represent regionally significant phases of reef growth during a prolonged sea level still stand we conclude that the reefs are therefore mostly relict features whose major phase of growth and development relates to an earlier pre holocene sea level still stand

environmental change across the early middle pleistocene transition small mammalian evidence from the trinchera dolina cave atapuerca spain t he sites of atapuerca are well known for their hominin bearing localities of early to middle pleistocene age trinchera dolina yields western europe s oldest fossil hominin the 850 ka homo antecessor and at sima de los huesos there occurs the best collection of the middle pleistocene hominin homo heidelbergensis however small mammals rodentia insectivora chiroptera and lagomorpha represent the largest number of species and greatest fossil abundance in the deposits of the atapuerca cave complex the small mammals are grouped by habitat catego ries but because the ecology of mammals is complex we base our study on the evolution of these categories throughout the sequence the assemblage distribution at the trinchera dolina site reflects landscape and environmental changes during the past million years shifts between wood land open land and moorland are indicated by the relative abundance of species based on diagnos tic elements such as first lower molars these data are combined with the distribution of large mammals pollen sediments and geological context of the trinchera dolina site from this interdis ciplinary approach we conclude that the first hominins from western europe homo antecessor lived during a warm wet and wooded interval probably corresponding to marine isotope stages 21 to 19 the transition from early to middle pleistocene at atapuerca is characterized by palaeoenvi ronmental changes recorded between levels td5 6 and td8 10 respectively the general opening of the landscape at the beginning of the middle pleistocene could have favoured the dispersal of hominins homo heidelbergensis across western europe

rock magnetic properties of multicomponent natural remanent magnetization in alluvial red beds ne spain summary an earlier study of the cyclic miocene red bed sequence of la gloria spain by krijgsman et al indicated complicated behaviour of the natural remanent magnetization nrm in parts of the section particularly close to reversal boundaries we resampled part of the section with high resolution and used extensive rock magnetic analyses to characterize the magnetic remanence carriers below a conspicuous hydromorphous layer the magnetic contributions of haematite and magnetite are approximately equal while in the brown layers on top of the hydromorphous layer the contribution of magnetite is drastically reduced this is probably related to a change in hydrological conditions the nrm is characterized by 1 a low temperature 200 360 c overprint of unknown age 2 a medium temperature 360 580 c component interpreted as the characteristic remanent magnetization chrm and 3 a high temperature haematite component 600 680 c carrying the same directions as the medium temperature component there is no perceivable delay in nrm acquisition between the medium and the high temperature components they are both regarded as primary the behaviour of the nrm seems to be similar in the cyclic lithologies the acquisition of nrm thus seems to be independent of lithology in the cyclic part of the section the higher sampling resolution yielded the detection of a new polarity zone which probably represents a geomagnetic feature according to rock magnetic properties however the more detailed magnetostratigraphy of the resampled part of the section indicates that the earlier correlation to the geomagnetic polarity timescale is no longer tenable therefore the la gloria section should no longer be used as a magnetostratigraphic dating tool of mammal biochronology

post early messinian counterclockwise rotations on crete implications for late miocene to recent kinematics of the southern hellenic arc most geodynamical models for the kinematics of the central mediterranean recognise that major tectonic rotations must have played an important role during the neogene the hellenic arc is believed to have been subjected to clockwise rotations in the west and counterclockwise rotations in the east while the southern part crete shows no rotations kissel and laj 1988 many qualitative and quantitative models are based on the idea that crete did not rotate we present new palaeomagnetic data which show that post early messinian counterclockwise rotations have occurred on crete the amount of counterclockwise rotation generally varies between 10o and 20o but in central crete much larger rotations up to40o counterclockwise were found only a few sections did not show any rotation the anisotropy of magnetic susceptibility ams shows lineations which are consistently wnw ese throughout crete indicating post rotational wnw ese extension or nne sse compression the observed counterclockwise rotations are consistent with the results of tectonic modelling by ten veen and meijer 1998 the latter study compares the late middle miocene to recent kinematics with modelled intra plate stresses for various possible distributions of plate boundary forces observations reveal that motion along left lateral and right lateral faults occurred during the pliocene the model analysis shows these motions to be consistent with transform resistance along the eastern segment of the overriding margin the counterclockwise block rotations observed by us are probably a consequence of displacements along the left lateral and right lateral faults and could reflect a similar tectonic regime that involved transform resistance 1998 elsevier science b v all rights reserved

segmentation of the hellenides recorded by pliocene initiation of clockwise block rotation in central greece abstract new paleomagnetic data from early miocene to pliocene terrestrial sedimentary and volcanic rocks in central greece constrain the history of vertical axis rotation along the central part of the western limb of the aegean arc the present day pattern of rapid block rotation within a broad zone of distributed deformation linking the right lateral north anatolian and kephalonia continental transform faults initiated after early pliocene time resulting in a uniform clockwise rotation of 24 3 6 5 over a region 250 km long and 150 km wide encompassing central greece and the western cycladic archipelago because the published paleomagnetic dataset requires clockwise rotations of 50 in western greece after 17 ma while our measurements resolve no vertical axis rotation of central greece between 15 ma and post early pliocene time a large part of the clockwise rotation of western greece must have occurred during the main period of contraction within the external thrust belt of the ionian zone between 17 and 15 ma pliocene initiation of rapid clockwise rotation in central and western greece reflects the development of the north anatolia kephalonia fault system within the previously extended aegean sea region possibly in response to entry of dense oceanic lithosphere of the ionian sea into the hellenic subduction zone and consequent accelerated slab rollback the development of the aegean geometric arc therefore occurred in two short duration pulses characterized by rapid rotation and strong regional deformation

palaeomagnetism in greece cenozoic and mesozoic components and their geodynamic implications abstract an important number of palaeomagnetic data have been obtained in greece during the last 20 years these data can be schematically divided into two groups according to their age when plate movements are fairly well constrained the cenozoic provides a dense network of palaeomagnetic directions the general pattern displays eastward declinations broadly distributed over a large distance from the ionian islands to the western greek rhodope and westward declinations less accurately constrained in space and time in the southern and eastern aegean and in western anatolia emphasis is given to the evaluation of this dataset by comparing it with new concepts of the regional tectonics in the mesozoic palaeozoic more scarcely covered reliable information is provided about latitudinal movements resulting in a suggested palaeolatitude of 15 20 n for almost all studied areas a model proposing prevailing counterclockwise rotations in the internal hellenides and strong clockwise rotations for the external hellenides appears plausible finally issues for future research are outlined for example mio pliocene formations from central greece the pindos ophiolites and palaeocene upper cretaceous data should receive further attention

a succession of miocene rodent assemblages from fissure fillings in southern france palaeoenvironmental interpretation and comparison with spain abstract an early to late miocene sequence of rodent assemblages from southern france has been quantitatively studied the resulting pattern seems very similar to a contemporary sequence from central spain calatayud teruel basin the fossil mammal bearing localities are of different types mainly karst infills in france and localities situated in sedimentary basins in spain in order to interpret the fossil record a comparison has been made between southern france faunas of similar age but collected in karst infills and in basin deposits there seems to be no difference between the two kinds of faunas and thus there is no indication that karst infills systematically give a picture of drier and more open environments both types of localities may give a similar relative abundance of taxa and when differences exist they can be attributed to local conditions the comparison between southern france and the calatayud teruel basin central spain shows that 1 similar trends occurred in the two areas 2 differences between spectra were more important during the late early miocene than during the middle miocene 3 the shift between the late early miocene and the middle miocene environments in southern france does not seem to be correlated with a general drop in temperatures as inferred from the analysis of central spain faunas

late miocene early pliocene temperature estimates in europe using rodents studies of mammal communities and in particular of rodents provide useful information on palaeoenvironments and palaeoclimates based on the relationship between species richness and climatic parameters we propose three models using arvicolines murines or sigmodontines in order to quantify past temperatures based on rodents temperatures are estimated here for late miocene early pliocene mn 9 to mn 15 european faunas at a regional scale two kinds of continental patterns in temperatures are observed with homogenous temperatures for mn 9 up to mn 11 or contrasted temperatures at the end of the miocene the onset of a latitudinal effect is also indicated during mn 15 temperature estimates have also been used to infer past elevation for localities

chronology of the eocene continental deposits of africa magnetostratigraphy and biostratigraphy of the el kohol and glib zegdou formations algeria despite numerous discoveries that have considerably enriched the african arabian tertiary fossil record over the last decades our knowledge of the evolutionary history of many continental african vertebrate groups during the paleogene period remains inadequate particularly when it is compared with the fossil records of europe or north america the eocene epoch in africa is especially poorly documented being restricted to few fossiliferous localities our understanding of the early tertiary emergence diversification and paleobiogeographic history of african arabian mammals has been further hindered by the lack of a precise temporal framework for these sites we conducted magnetostratigraphic analyses associated with biostratigraphic studies in the fossiliferous sequences exposed in the northwestern hammadas of the saharan platform in the glib zegdou area and in the saharan atlas at the el kohol locality algeria to further define the age of these eocene continental deposits based on biostratigraphic constraints the six polarity zones identified in the el kohol section can be correlated with chrons c24n to c22r providing the first direct age estimates for the el kohol fossiliferous strata between 52 and 51 ma correlation to the geomagnetic polarity time scale using previously published biostratigraphic data for the glib zegdou fauna suggests an age ranging between 49 and 45 ma for this section the high resolution magnetostratigraphic study of the poorly known continental eocene epoch of algeria provides new insights into the early tertiary stratigraphy of northwest africa the placement of the algerian localities into a consistent chronological framework constitutes considerable advancement to achieve biostratigraphic correlation of the paleogene african arabian mammal localities

palaeoenvironmental change in the gulf of carpentaria australia since the last interglacial based on ostracoda throughout the last glacial cycle the region between australia and new guinea which is today known as the gulf of carpentaria has oscillated from open shallow marine conditions to a large land locked freshwater lake including periods of subaerial exposure ostracod faunal assemblages and variations in the valve morphology preserved in the sediments of the gulf record these changes a 14 8 m long core md972132 extracted from near the centre of the modern gulf of carpentaria spanning the last 130 ka bp provides the basis of this study environmental facies were determined by r and q mode cluster analysis of the ostracod assemblage data including 72 species and comparison with modern analogues from both the gulf of carpentaria and southeast asian region using these methods six clearly distinct biofacies were identified i open shallow marine facies including bairdiids pectocytherinids and cytherettids ii shallow marine facies dominated by cytherella and hemikrithe iii marginal marine facies including xestoleberis and praemunita iv tidal channel facies dominated by loxoconcha v estuarine assemblage comprising venericythere and leptocythere vi non marine facies a brackish lagoon lake facies dominated by cyprideis and leptocythere b freshwater facies including ilyocypris with cyprinotus and cypretta in addition morphological variation of valves of the more plastic species in particular cyprideis australiensis and leptocythere hartmanni was observed and related to environmental variables including salinity and solute composition these two species occur through more than half of the length of the core and show significant variability c australiensis with irregularshaped sieve pores is associated with heavily reticulated valves of l hartmanni around 90 70 ka bp indicating increased salinity and carbonate limited environments conversely c australiensis with round sieve pores occurs with finely reticulated valves of l hartmanni from around 50 ka bp in fresher carbonate rich environments the preservation of valves was also noted so as to infer post depositional effects revealing shoreline features channel activity and subaerial exposure combined ostracod biofacies and morphological analysis reveals a fluctuating marine environment through marine isotope stage mis 5 terminating in a restricted lagoon around 90 ka bp followed by an extensive period of subaerial exposure in this

aragonian stratigraphy reconsidered and a re evaluation of the middle miocene mammal biochronology in europe abstract the recently collected fauna of armantes 1a in chron c5br of the armantes section necessitates reinterpretation of the previous bio and magnetostratigraphical correlations between the armantes and vargas sections calatayud daroca basin central spain w krijgsman m garces c g langereis r daams j van dam a j van der meulen j agusti l cabrera a new chronology for the middle to late miocene continental record in spain earth planet sci lett 142 1996 367 380 the long reversal in the vargas section is now correlated to c5br instead of to c5cr on the basis of the biostratigraphical correlation of armantes 1a to the faunas of fuente sierra 2 and 3 in the vargas section which are situated in the basal part of the middle aragonian mn5 this leads to the revised age of 16 0 ma for the early middle aragonian mn 4 5 boundary our age estimate of the mn5 6 boundary is maintained at ca 13 75 ma the vargas section is now considered to start in chron c5cn 2r and to end in c5bn 1n as a result of the revised correlation the duration of the time gap between the fossiliferous parts of vargas and the younger aragon section previously estimated as ca 1 5 myr is now reduced to less than 200 000 years the tie points of the european mammal units mn4 mn6 to the geomagnetic polarity time scale f f steininger w a berggren d v kent r l bernor s sen j agusti circum mediterranean neogene miocene and pliocene marine continental chronologic correlations of european mammal units in r l bernor v fahlbusch h w mittmann eds the evolution of western eurasian neogene mammal faunas columbia univ press new york 1996 pp 7 46 are evaluated our age estimates of the mn4 5 and mn5 6 boundaries are compatible with the new magnetostratigraphic calibration of middle miocene mammal zones in the swiss molasse basin o kempf t bolliger d kalin b engesser a matter new magnetostratigraphic calibration of early to middle miocene mammal biozones of the north alpine foreland basin in j p aguilar s legendre j michaux eds actes du congres biochrom 97 mem trav e p h e 21 1997 547 562

magnetobiochronology of lower miocene ramblian continental sediments from the tudela formation western ebro basin spain abstract the calibration of european lower miocene continental stages is poorly constrained due to the lack of robust magnetostratigraphic data from continental sediments of this age in this paper we present the first magnetostratigraphic results from the mammal fossil bearing continental sediments of the lower middle miocene tudela formation western ebro basin spain the study is based on 331 paleomagnetic sites distributed along a 790 m thick composite section the resulting magnetostratigraphy provides an independent correlation to the geomagnetic polarity time scale and allows accurate dating of previously known and new ramblian upper lower miocene fossil localities of the tudela formation the new age constraints derived for the tudela formation fossil localities provide together with a revaluation of other iberian faunas the first magnetochronology for the ramblian continental stage the lower boundary of the ramblian is placed at the lower part of chron c6r ca 20 4 ma and the boundary between the lower and upper ramblian is located at the middle of chron c6n ca 19 6 ma the upper boundary of the ramblian and hence the base of the aragonian is placed at the upper middle part of chron c5cr 16 8 17 ma our results also provide the first magnetostratigraphically dated mn3 faunas in spain which together with a revaluation of other iberian and european faunas provide a revised calibration of european mammal zone mn3 the lower boundary of zone mn3 is placed at the boundary between chrons c6r and c6n ca 20 1 ma and its upper boundary is located at the upper middle part of chron c5cr 16 8 17 ma

a holocene pollen record from lowland tropical australia a pollen record from a dunefield lake on groote eylandt northern australia is presented this is the first substantially complete holocene terrestrial record from the seasonally humid lowland tropics of northern australia the lake originated as a seasonal swamp prior to 10 000 bp a progressive rise in water tables occurred until a permanent lake was established at about 9000 bp from 9000 to 7500 bp the lake shows evidence of disruption in the surrounding dunefield prior to 7500 bp an open grassland covered the dunefield after 7500 bp the area was rapidly colonized by eucalyptus open forest and acacias these types remain dominant to the present the data suggest that conditions continuously ameliorated from the base of the record to the mid holocene and there is evidence of an effective precipitation maximum at about 4000 bp effective precipitation declined after 3800 bp but a recovery took place about 1000 bp

regime of the filchner ronne ice shelves antarctica seismic radio echo twerle balloon and oceanographic data of the filchner ronne ice shelves are analysed a large thin area in the central ronne ice shelf is found to differ from the morphology of the ross and filchner ice shelves this area is partly filled by basal saline ice which can be attributed to regional regelation caused by oceanic circulation

magnetostratigraphy of the vallesian late miocene in the valles penedes basin northeast spain the magnetostratigraphic analysis of the late miocene continental deposits from the valles penedes basin combined with its well documented fossil mammal record has provided a well resolved chronology for the upper basin infill the study is based on the biostratigraphic and magnetostratigraphic cross correlation of 12 sections throughout the alluvial sequences in the western valles area the biostratigraphic framework consists of 21 mammal localities corresponding to the mammal neogene mn9 and mn10 units the composite magnetic polarity sequence is based on 400 paleomagnetic sites correlation with the geomagnetic polarity time scale gpts has led to an absolute dating of the faunal events and a precise chronostratigraphy of the vallesian mammal stage in its type area the hipparion first appearance datum fad at the mn8mn9 boundary is dated at 11 1 ma in the valles penedes basin this age compared to other radiometrically dated localities in europe north africa and turkey is consistent with an isochronous dispersal of this equid through the mediterranean region a possible isochrony at a larger geographical scale old world mesogea must await more reliable ages of the hipparion fad in asia and africa the cricetulodon fad mn9amn9b boundary is dated to 10 4 ma in chron c5n the progonomys fad mn9mn10 boundary corresponding to the intra vallesian faunal crisis is dated at 9 7 ma c4ar 3r the vallesian spans 2 4 myr from 11 1 ma c5r 1n to 8 7 ma c4an and correlates to the early tortonian

biostratigraphy and palaeobiogeography of east africa and the iberian peninsula abstract the aim of this paper is to examine the mammalian faunas of the neogene of spain and of east africa with a view to understanding the relationships between the neogene faunas of the two regions the available data indicates that during the neogene faunal similarities between iberia and east africa varied greatly at times the resemblances being relatively great high number of genera in common at others the similarities being weak low number of genera in common changes in faunal similarity appear to be related to latitudinal fluctuations in the position of the boundaries of the proto ethiopian and proto palaearctic zoogeographic realms periods of greater faunal similarity coincide with a northerly position of the boundary zone while periods of greater faunal dissimilarity occur when the boundary zone is located in a southerly position as it is today we related these changes in the position of the boundary zone between zoogeographic realms to geotectonic climatic and astronomic changes which affected the globe

recent glacial history and rapid ice stream retreat in the amundsen sea microfossil analyses of core top samples from 20 sites in the eastern and southern amundsen sea delimit three biotic provinces which are related in part to the activity of a large ice stream and modern sea ice distribution in recent sediments on the outer shelf planktonic and calcareous benthic foraminifera are abundant but diatoms are rare here low diatom abundances in sediments despite high abundances in the overlying sea ice are attributed to nondeposition caused by ocean currents pine island bay sediments are almost barren of microfossils even though diatoms are abundant in overlying surface waters we attribute this discrepancy to deposition of exclusively non organic sediments beneath a former extension of the floating terminus of pine island glacier which probably retreated from this area during the last century the polynya which occupies this area during present day summers is probably so recent a feature that little or no biogenic sediment has accumulated recent sediments in the eastern margin province between pine island bay and the outer shelf contain abundant diatoms and arenaceous foraminifera high diatom abundances here probably record the presence of the amundsen sea polynya during the last few millennia the presence of a compact diamicton beneath recent sediments on the outer shelf and in the eastern margin province suggests that grounded ice formerly occupied the amundsen sea shelf with ice streams in deep elongated troughs these ice streams may have retreated up to 200 km during the holocene

the vallesian mammal succession in the valles penedes basin northeast spain paleomagnetic calibration and correlation with global events abstract the integrated lithostratigraphic biostratigraphic and magnetostratigraphic study of new and classical alluvial fan sequences in the valles penedes basin northeast spain western mediterranean enabled a considerable refinement of the vallesian mammalian succession in this basin and its correlation with the magnetic polarity time scale up to 12 new sections were logged and sampled in a search of mammal remains and a paleomagnetic analysis was carried out the correlation among these sections was based on the small mammal content and the succession of magnetozones enabling the establishment of four main composite sections les fonts montagut terrassa and viladecavalls as a result the vallesian in the valles penedes basin appears punctuated by four main mammalian events which coincide with the appearance of the genera hipparion cricetulodon progonomys and rotundomys the hipparion event did not coincide with any further change in the associations of small and large mammals the dispersal of the cricetid cricetulodon in its turn involved the first set of extinctions in the vallesian affecting the rodent and carnivore and artiodactyl associations the main break during the vallesian coincided with the dispersal of the murids of the genus progonomys and implied a sudden drop in the diversity of the rodent and artiodactyl species of warm wet forested affinities this phase is characterized by the association of the murid progonomys and the cricetid cricetulodon and includes the last record of hominoids in the basin the replacement of cricetulodon by the sigmodont cricetid rotundomys was associated with the entry of some typical early turolian species according to the correlation established it is concluded that the fad of hipparion in the valles penedes basin is dated at 11 1 ma at the base of chron c5r 1n this data is congruent with other datings in northern africa and eastern europe suggesting the isochrony of this event in the mediterranean regions the cricetulodon fad is dated to 10 4 ma in chron c5n the progonomys dispersal coincident with the late vallesian crisis is dated at 9 7 ma in chron c4ar 3r the rotundomys fad is dated at 9 2 9 3 ma in the upper part of chron c4ar 1n the vallesian mammal bioevents affected the peri mediterranean zones including northern africa and other regions in northern and western eurasia these paleofaunistic changes were caused by temperature descent from subtropical to warm temperate conditions as well as by changes in the aridity balance and seasonality this climatic evolution was the result of the interplay of diverse global events cooling of the high latitude regions growing of the antarctica ice sheet and enhancement of the thermohaline oceanic circulation and of large scale tectonic and paleogeographic processes surface uplift of the himalayas the tibetan plateau and other tectonic reliefs closing of gateways between the mediterranean marine regions and the world ocean the magnetobiochronology resulting from the study of the western valles sequences suggests a close chronological correlation between some of these global and regional processes and the vallesian bioevents recorded

a new procedure for gridding elevation and stream line data with automatic removal of spurious pits abstract a morphological approach to the interpolation of regular grid digital elevation models dems from surface specific elevation data points and selected stream lines is described the approach has given rise to a computationally efficient interpolation procedure which couples the minimization of a terrain specific roughness penalty with an automatic drainage enforcement algorithm the drainage enforcement algorithm removes spurious sinks or pits yielding dems which may be used to advantage in hydrological process studies the drainage enforcement algorithm has also been found to significantly increase the accuracy of dems interpolated from sparse but well chosen surface specific elevation data moreover it facilitates the detection of errors in elevation data that would not be detected by more conventional statistical means and forms a sound physical basis for cartographic generalization

correction to repeating waveform initiated by a 180 190 ka geomagnetic excursion in western north america implications for field behavior during polarity transitions and subsequent secular variation by robert m negrini et al

paleomagnetic results from mio pliocene marine sedimentary series in crete abstract paleomagnetic measurements have been conducted on mio pliocene marine sedimentary series from crete in order to detect any eventual rotation of this island the results obtained from 14 stable sites of tortonian age 7 m y yield a paleomagnetic pole not significantly different from either the european or the african ones showing that crete has not undergone any significant rotation since that epoch

new evidence for episodic post glacial sea level rise central great barrier reef australia abstract we present an extensive database of 364 radiocarbon dates from coastal and marine sediments of the central great barrier reef gbr shelf of which 110 are previously unpublished the elevation data have been reduced to a common datum australian height datum ahd and the various sources of error have been assessed using modern lithological and biological relationships with sea level the elements of the radiocarbon database have been converted into sea level indicators the upper bound of the assembled dataset corresponds to a best estimate sea level curve and the full dataset provides a narrow envelope for sea level rise on the gbr shelf for the last 11 12 kyr not including hydro isostatic crustal flexing the envelope is consistent with episodic rise in post glacial sea levels the rising post glacial sea level probably included stillstands or minor falls at ca 45 m ahd at ca 10 5 kyr b p 5 m 7 8 kyr b p 2 m ca 6 kyr b p and 1 7 m 5 5 kyr b p there is evidence for a significant fall in sea level between stillstands at 11 m 8 5 kyr b p and 17 m 8 2 kyr b p stillstand durations apparently ranged between the vertical spread in the derived sea level data is very wide the use of shell material for dating seems unreliable and prone to large and unpredictable errors data from bulk mangrove muds appear reliable for determination of ancient sea level but may at times result in sea level being placed up to 4 m below the true level in situ biogenic carbonates such as preserved oyster beds and coral micro atolls are the most reliable indicators of sea level position while deposits of mangrove mud give a useful first order approximation of ancient sea levels caution should be used in drawing sea level curves from few data points we conclude that the post 11 12 kyr b p relative rise in sea level was episodic on the central gbr continental margin more data are required to define clearly sea level change up to ca 20 m at 9 kyr b p

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

geographic and temporal patterns in the late neogene 12 3 ma aridification of europe the use of small mammals as paleoprecipitation proxies abstract present day relations between small mammal community structure and rainfall are used to predict late neogene 12 3 ma precipitation patterns in europe and anatolia new proxy methods are developed which include regressions of mean annual and minimum monthly precipitation on diet invertivory index and locomotion habitat arboreality index a series of precipitation maps and a set of regional precipitation curves through time at 1 myr resolution are presented precipitation curves at a higher temporal resolution are constructed for the region of central spain the miocene results show the existence between 12 and 9 ma of a large wet 800 1200 mm yr zone extending from northern spain to the ukraine and characterized by the whole year penetration of large amounts of moisture far into the continent between 10 9 and 5 ma this european temperate wet zone etwz shrinks and or moves northward resulting in diachronous aridification a coeval northward migration of the subtropical high pressure zone shpz is hypothesized which is also consistent with the predicted onset of seasonal summer dryness between 10 and 8 ma the maximum extension of the etwz at 12 9 ma temporally correlates with northern hemisphere cooling suggesting that climate zonation rather than the global amount of atmospheric moisture controlled european climate at this time the main aridification at 9 8 ma could best be explained by a northward extension shifting of the subtropical high pressure zone and a transition towards less zonal circulation processes which ultimately could have been triggered by uplift of the tibetan plateau a temporary increase of precipitation at 7 6 ma is associated with renewed global cooling the lowest precipitation values less than 400 mm yr occur during the pliocene in southern and eastern europe uplift in eastern europe carpathians shrinking of the paratethys could well explain the aridification in this area and the associated sharpening of east west precipitation gradients across the continent

cyclostratigraphy and rock magnetic investigation of the nrm signal in late miocene palustrine alluvial deposits of the librilla section se spain 1 we constructed a high resolution time frame for the cyclic continental palustrine alluvial section of librilla se spain which covers the onset of the messinian salinity crisis in the marine realm the section was dated earlier by garces et al 1998 using magnetostratigraphy we resampled part of the section that contained a reversed overprint in detail to refine the magnetostratigraphy and to investigate the behavior of the natural remanent magnetization nrm signal the detailed sampling yielded a better constrained position of the upper reversal of chron c3an 1n by counting the number of cycles in c3an 1n and taking into account the duration of this chron we were able to show that the basic sedimentary cycles in librilla reflect climatic precession subsequently the sedimentary pattern was tuned to the summer insolation curve providing a high resolution time two intervals of complex nrm behavior were identified showing normal and reversed overprints the reversed overprints seemed to be restricted mainly to gray palustrine layers the analysis of coercivity components revealed no difference between samples with overprints or real nrm directions we performed fuzzy c means cluster analysis on a geochemical data set to link magnetic behavior to geochemical proxies resulting in a three cluster model that roughly describes lithology remarkably all the samples with a normal overprint belong to one particular cluster the reversed overprints however do not show any relation to the cluster partition we favor the explanation of garces et al 1998 that the reversed overprint would be related to the messinian salinity crisis

trace metals in lacustrine and marine sediments a case study from the gulf of carpentaria northern australia abstract sediment cores taken from the shallow the data form remarkably linear covariation trends suggesting physical mixing of two sedimentary components as the predominant process controlling the compositions of both lacustrine and marine sediments one component has high ca sr and mn suggestive of biogenic carbonate the other component contributes virtually all of the sedimentary budget of the other elements and is probably terrigenous clay either water borne or aeolian minor contributions from heavy minerals such as zircon may account for the higher values of zr and y for some horizons in the core anomalously high concentrations of zircon may have been brought into the gulf as dust particles during episodes of increased aeolian activity carbonate is most abundant in the marine sediments resulting in the higher observed ca and sr concentrations v and mn seem to be the metallic elements most sensitive to depositional environment and water chemistry environmental conditions had little or no effect on sedimentation of the other metals v and mn were delivered to the lacustrine sediments more efficiently than to the marine sediments probably reflecting changes in solubility as slightly acid lacustrine waters gave way to more neutral oceanic conditions metal organic complexing was not an important process in these oxidised sediments

ecogeographical stability and climate forcing in the late miocene vallesian rodent record of spain abstract the composition and structure of rodent taxocenosis from three iberian basins with a reasonably complete record calatayud teruel duero and valles penedes for the latest aragonian and vallesian middle late miocene is explored using correspondence analysis ca ca classifies the assemblages in four great groups that are interpreted as rodent paleocommunity types rpts on the basis of paleobotanical and paleomastological data available for some of the sites considered or time equivalent localities each rpt is considered to be characteristic of certain environmental conditions taxonomic membership and relative abundance patterns in the recognized rpts are quite stable throughout relatively long time intervals in each basin suggesting the existence of coordinated stasis however the predictions of coordinated stasis are only partly achieved and important differences are shown to occur within certain rpts rpts with a low species richness and dominated by one or two genera characterize the record of the duero basin in the case of the valles penedes and calatayud teruel more equitative rpts with a high species richness are present during the early vallesian and also during the latest aragonian in the valles penedes the late vallesian sites appear as clearly differentiated of the remaining ones and grouping is strongly influenced by geographic position the environment seems to have been more open and wet dry seasonal in the late vallesian sites of the calatayud teruel and duero basins instead in the valles penedes basin it appears to have been more humid and cool warm seasonal this fact points to the existence of a zonation of the iberian climate during the late vallesian that closely matches the pattern observed today

multiproxy reconstruction of the palaeoclimate and palaeoenvironment of the middle miocene somosaguas site madrid spain using herbivore dental enamel profound palaeoclimatic changes took place during the middle miocene the miocene climatic optimum 20 to 14 13 5 ma was followed by a sudden 200 ka decrease in temperature and an increase in aridity around the world as a consequence of the reestablishment of the ice cap in antarctica somosaguas palaeontological site madrid basin spain has provided a rich record of mammal remains coincident with this global event middle miocene biozone e 14 1 13 8 ma it contains four fossiliferous levels t1 t3 1 t3 2 and t3 3 with t1 being the oldest that span an estimated time of 105 125 ka scanning electron microscope sem and rare earth element ree analyses performed on herbivore tooth enamel gomphotherium angustidens anchitherium cf a cursor conohyus simorrensis prosantorhinus douvillei and ruminants indicate that diagenetic processes have not been intense enough as to obscure the original geochemical signal stable isotope 18oco3 13cco3 and 18opo4 analyses have been measured on the herbivore tooth enamel across these levels with the aim of determining to what extent the global cooling and aridity pattern is recorded at this site a decrease in 18oco3 and 18opo4 has been detected from t1 to t3 3 and t3 1 to t3 3 respectively indicating a progressive drop of about 6 c from around 18 c to 12 c in mean annual temperatures within t3 tooth enamel 13c values experience an increase from t3 1 to t3 3 suggesting an increase in aridity ba ca analyses have also been performed on the tooth enamel in order to detect changes in the palaeoecology of the studied taxa this ratio allows the establishment of particular feeding patterns such as a more browsing habit in the case of gomphotherium angustidens compared to anchitherium cf a cursor as suggested by higher ba ca values in the latter trace elements do not support any significant change across the succession in the dietary behaviour of the species analyzed despite the stable isotopes evidence of an important palaeoclimatic shift from t1 to t3 3

magnetostratigraphic dating of the middle miocene climate change in the continental deposits of the aragonian type area in the calatayud teruel basin central spain the exceptionally dense mammalian faunal record of the aragonian type area in central spain shows that an important climate change towards a cooler and more humid climate is recorded during the neogene mammal zone mn 5 1 the magnetostratigraphic results from mammal bearing middle miocene continental sections in the aragonian type area indicate that the onset of this climate change at the mn 4 mn 5 boundary occurs in the reversed chron c5acr and has an age of 14 1 ma according to the geomagnetic polarity timescale gpts of cande and kent 2 this age is consistent with the age estimate of 14 1 14 05 ma for the main increase in 6 so in the marine record 3 these independent observations of time equivalent cooling in both continental and marine records confirm and accurately date a global cooling event in the middle miocene the age of 14 1 ma for the mn 4 mn 5 boundary is significantly younger than previously recorded in continental timescales 4 5 this results in a longer duration by approximately 3 myr of the mn 4 zone which is consistent with the many important faunal changes occurring in mn 4 furthermore the mn 5 mn 6 boundary occurs in chron c5acn 13 8 13 9 ma and the mn 6 mn 7 8 boundary in the interval c5ar ln c5ar 3r 12 7 13 0 ma

rodents and climate a new model for estimating past temperatures based on the high correlation between species richness in sigmodontine rodents and temperatures we propose a new model in order to quantify past climates because of the close phylogenetic relationship and the tooth morphological similarity between extant new world cricetids sigmodontinae and fossil european cricetids cricetinae s l extant new world sigmodontines are taken as analogues for old world fossil cricetines sigmodontine species richness has been compiled for 282 extant local faunas from north central and south america with corresponding climatic data temperatures and precipitations there is almost no correlation between areas covered by local faunas ranging from 1 km2 up to 46 000 km2 and numbers of sigmodontine species in localities r2 0 027 number of sigmodontine species in local faunas and mean annual daily temperatures are highly correlated r2 0 88 the relationships of species richness and precipitation is low r2 0 19 for mean annual precipitation the method is exemplified for old world cricetines using well documented miocene rodent faunas located in the lyon area

hydration diapirism a climate related initiation of evaporite mounds in two continental neogene basins of central spain abstrlld wllile rrany halokinetic mode conslder rhat a thlck overburdea is necessary bcfore jiapni i l develops other ludie how ttnu all migllt hegin ti llltwe soca flef x curs with no lverburden on iop of lhem the iritum rus suggcsung thc eaely hulging of lhe evaporitcs f the l ow r unil forming 3 p t currlief oerorc and during the deposirion of thc lntermediate unit rely on certam cuaructer isl cs ollhe palaeokarcts developcd on the roo uf thc wwer unir as wehas in the nanre dispo ilion thiekne s and yn edll1eljl iry prccesses of ihe intermediale 1jnil id f il11 tell ion gashcs and collapse structures develop withln lhe ev r ritc mound and these dcformatiol teanuv mighl be related 1 lhelt upliit histor thi agent of iniriarton suggested in this papa for the evapmite mounds hydraticn diapirism or a volume increase related to the hydrauon of anhy mile to gyp ulli ha not been l reviou ly recognize j in lhe literature a series 01 sedimentologi cal and palaeontclogical argumcnts flll1h ili g st hat thi hemi a rc cu was trii clell by a chrnatic changc at the boundary betwcen the luwer and the inrc rnediate units

the dynamics of ice sheet outlets a comparison of data from aircraft altimetry landsat imagery and radia echo sounding has shown characteristic surface topographies associated with sheet and stream flow the transition between the two is abrupt and occurs at a step in the subglacial topography this marks the onset of basal sliding and high velocities caused by subglacial water it results in crevassed amphitheatre like basins round the head of outlet glaciers it is also the zone of maximum driving stress beyond which values decline rapidly as velocities increase this abrupt transition appears to be topographically controlled since basal temperatures are at the pressure melting point well inland of the change in regime the marie byrd land ice streams exhibit qualitative differences from other ice sheet outlets however the change to lower driving stresses is much more gradual and occurs several hundred kilometres inland such ice streams have particularly low surface slopes and appear in form and flow regime to resemble confined ice shelves rather than grounded ice the repeated association of the transition to rapid sliding with a distinct subglacial feature implies a stabilizing effect on discharge through outlet glaciers acceleration of the ice is pinned to a subglacial step and propagation of high velocities inland of this feature seems improbable rapid ice flow through subglacial trenches may also ensure a relatively permanent trough through accentuation of the feature by erosion this is concentrated towards the heads of outlet glaciers up stream of the region where significant basal decoupling occurs this may be a mechanism for the overdeepening of fjords at their inland ends and the development of very steep fjord headwalls

a holocene pollen and diatom record from vanderlin island gulf of carpentaria lowland tropical australia sedimentary palynological and diatom data from a dunefield lake deposit in the interior of vanderlin island in the gulf of carpentaria are presented prior to the formation of present perennial lake conditions the intensified australian monsoon associated with the early holocene marine transgression allowed cyperaceae sedges to colonise the alluvial margins of an expansive salt flat surrounded by an open eucalyptus woodland as sea level stabilised between 7500 and 4500 cal yr b p coastal dunes ceased to develop allowing dense melaleuca forest to establish in a restionaceae swamp dune sand input into the swamp was diminished further as the increasingly dense vegetation prevented fluvial and aeolian transported sand arriving from coastal sources this same process impounded the drainage basin allowing a perennial lake to form between 5500 and 4000 cal yr b p myriophyllum and other aquatic taxa colonised the lake periphery under the most extensive woodland recorded for the holocene the palynological data support an effective precipitation model proposed for northern australia that suggests more variable conditions in the late holocene a more precise measure of effective precipitation change is provided by diatom based inferences that indicate few changes in lake hydrology such interpretations are explained in terms of palynological sensitivity to adjustments in local fire regimes where regional precipitation change may only be recorded indirectly through fire promoting mechanisms including intensified enso periodicity and human impact

palaeoenvironmental and palaeoclimatic evolution of the serres basin n greece during the miocene abstract the palaeoenvironmental and palaeoclimatic evolution of the serres basin from the end of mid miocene to the end of the miocene is examined lignites were deposited over a thick sequence of conglomerates and sands fossils found in the lignites indicate a lacustrine environment with tropical subtropical climatic conditions the climate became progressively drier and only small lakes were reserved during the messinian salinity crisis deposition of lake sediments finally ended with the world wide pliocene marine transgression a correlation of the serres basin with other lacustrine basins in the aegean area is attempted

cenozoic landscape development within the central iberian chain spain abstract in the central iberian chain spain covering an area of some 7400 km 2 up to seven stepped erosion surfaces are determined from aerial photographs and field observations these planation surfaces situated between 1000 and 1600 m a s l are separated by erosional scarp slopes most parts of the erosion surfaces are developed on mesozoic limestones and form stepped rims around the main elevations of the iberian chain it is proposed that the surfaces were formed by erosional events associated with periods of uplift related to eocene miocene compressional tectonic activity the palaeogene uplift was related with syntectonic sedimentation in internal basins with up to 3500 m of accumulated thickness during the neogene middle miocene pliocene post tectonic period the lowered synclinal areas formed residual internally drained basins that were filled with non marine deposits mainly clays and limestones the filling of the internally drained sedimentary basins located within the iberian chain onlapped onto the ancient erosional surfaces covering the lower younger levels the recent landscape evolution of the whole area is controlled by the capture of the internal basins and the dissection of the ancient relief by the present day fluvial network this process is related with the transition from internal to external drainage of the ebro basin

the use of glass for dating volcanic ash by thermoluminescence the development of a new physical dating method for late pleistocene tephrochronometry is described here tests of laboratory procedures applied to glass from independently dated samples show that the thermoluminescence tl additive dose dating method can yield accurate ages for both proximal and distal tephra from a few hundred years to at least 400 ka the technique involves purification of 4 to 11 m glass by heavy liquid centrifugation pre tl readout heating at 50 75 c for 8 days and careful regression analysis of tl growth curves several unknown age tephra are dated directly by this method for the first time these include five ash beds from summer lake oregon 67 200 ka a sheep creek valley ash from alaska 81 9 ka an ash from nevada 200 50 ka correlated to the wadsworth tephra an unknown ash 210 30 ka from rye patch dam in nevada previously correlated to the 400 to 600 ka dibekulewe tephra and ash 9m from washtucna in eastern washington 250 30 ka

correlation of late quaternary tephra layers in a long pluvial sequence near summer lake oregon abstract near summer lake in southern oregon 54 tephra beds of late quaternary age are exposed in pluvial lake sediments of lake chewaucan seven of the tephra beds near the top can be correlated with tephra deposits younger than 117 000 yr at mount st helens washington at crater lake oregon and in northwestern nevada in the deposits of pluvial lake lahontan however most of the section at summer lake lies below the correlated units and contains 39 tephra beds older than 117 000 yr major element chemistry of tephra glasses was determined by electron microprobe analysis petrography supports the correlations made from chemical evidence compositions correlated range from 70 to 76 sio 2 the least silicic summer lake glass contained 57 extrapolation of depositional rate suggests that most of the sediments at summer lake are younger than about 335 000 yr but older lake beds containing tephra layers occur at one place the long lacustrine record suggests that lake chewaucan persisted through the last interpluvial stage and that the lake may have dried up at the end of the pleistocene due to diversion of the chewaucan river by relict shore features

magnetostratigraphy and biostratigraphy of the neogene deposits of kastellios hill central crete greece abstract the kastellios hill section is situated in central crete and composed mainly of mudstones and silts deposited in lacustrine brackish or estuarine environments several levels of this section have yielded the remains of mammals foraminifera ostracoda pollen and spores the palynological analysis shows that the region was forested in the upper miocene with a vegetation confined to climates warmer than the present the age indicated by foraminifera is early tortonian while the mammals were attributed to late vallesian in continental biochronology of this section 88 m have been sampled for a magnetostratigraphic study several experiments have been made on the magnetic properties of these sediments showing that they are suitable for a paleomagnetic study moreover x ray diffraction and microprobe analysis of 19 samples regularly distributed over the section show that no major changes occurred in the chemical composition from 77 separate sites 241 samples have been demagnetized thermally 215 or by alternating field 26 the main result of this study is the definition of a long reversed polarity period interrupted by two short normal intervals this magnetostratigraphic sequence can be correlated using biostratigraphic data with a part of chron 5 r of the geomagnetic time scale in other words this section is probably younger than 11 47 my and older than 10 30 my

evolution of early middle miocene rodent faunas in relation to long term palaeoenvironmental changes abstract cluster and principal components analyses have been applied to the composite sequence of 59 rodent assemblages from ramblian to lower vallesian deposits in the daroca calamocha area in the calatayud teruel basin north central spain the studied record is thought to represent the interval from the late aquitanian to the end of the serravallian i e early to middle miocene from ca 22 10 5 ma ago the quantitative results are interpreted by using individual rodent taxa as environmental indicators and by extrapolating the predominant adaptive strategies of recent taxonomic groups which also seem to form natural groups on a demographic scheme french et al 1975 a general warming trend starts in the rambian early miocene and continues into the middle aragonisn early middle miocene the cooling in the middle to late aragonian boundary interval is correlated to the middle miocene cooling phase another cooling occurred around the aragonian vallesian boundary late middle miocene we relate a major increase of aridity in the beginning of the middle aragonian ca 16 5 ma to the spread of low biomass vegetation due to intensification of the subtropical belt wolfe 1985 a notable feature around the early middle aragonian boundary indicating a major shift of climatic belts is the reversal of the relationship between our relative temperature and humidity curves before the reversal we find a positive correlation after it a negative correlation around the middle to late aragonian boundary humidity increased again and a further increase of humidity is indicated by the earliest vallesian faunas our data suggest that the nature of favoured adaptive strategy amongst rodents is related in the end to the degree of climatic humidity

general bathymetry of the gulf of carpentaria and the quaternary physiography of lake carpentaria abstract a generalized bathymetric map of the gulf of carpentaria has been prepared from royal australian navy sounding data the results confirm earlier work of nix and kalma and indicate that a closed basin lake carpentaria below 53 m present water depth could have existed during quaternary low sea level stands an evaluation of previous and present work shallow seismic records of the canadian superior mining co australia and oil company fathometer profiles indicate the preservation of lake sediments at 65 m and 53 m water depth preserved shoreline feature at 19 m 29 m and 65 m as well as extensive underlying erosion and incision these findings are consistent with erosion and incision of gulf sediments during sea level lowering aeolian infilling and dune formation on the present arafura sill during the dry phase of maximum glaciation and subsequent lake carpentaria formation and lacustrine sediment deposition most probably during the sea level rise phase lake carpentaria clearly dominates the physiography and climatology of this land bridge during quaternary time

vostok ice core a continuous isotope temperature record over the last climatic cycle 160 000 years a continuous deuterium profile along the 160 000 year vostok ice core antarctica is interpreted in terms of atmospheric temperature changes this climatic record is the awaited terrestrial complement of the deep sea records supporting the existence of a relation between the pleistocene climate and orbital forcing

the sedimentary record of palaeoenvironments and sea level change in the gulf of carpentaria australia through the last glacial cycle abstract environmental evolution of the gulf of carpentaria region the world s largest tropical epicontinental seaway through the last glacial cycle has been determined from a series of six sediment cores these cores form the focus of a multi disciplinary study to elucidate sea level climate and environmental change in the region the sedimentary record reveals a series of facies including open shallow marine marginal marine estuarine lacustrine and subaerial exposure throughout the extent of the basin during this period the partial or complete closure of the central basin from marine waters results from sea level falling below the height of one or both of the sills that border the gulf the arafura sill to the west 53 m below present sea level bpsl and torres strait to the east 12 m bpsl the extent and timing of these closures and restriction of the shallow waterbody within are intrinsic to local ocean circulation available latent heat transport and the movement of people and animals between australia and new guinea whilst the occurrence of the palaeo lake carpentaria has previously been identified this study expands on the hydrological conditions of the lacustrine phases and extends the record through the last interglacial detailing the previous sea level highstand mis 5 5 and subsequent retreat when sea levels were low during the mis 6 glacial period the gulf was largely subaerially exposed and traversed by meandering rivers the mis 5 transgression 130 ka bp led to marine then alternating marine estuarine conditions through to mis 4 70 ka bp when a protracted lacustrine phase of varying salinity and depth area and including periods of near desiccation persisted until about 12 2 cal ka bp the lake expanded to near maximum size 190 000 km 2 following the intensification restoration of the australian monsoon at 14 ka bp this lake full phase was short lived as by 12 2 cal ka bp marine waters were entering the basin coincident with the progressive sea level rise fully marine conditions were restored by about 10 5 cal ka bp by westward connection to the arafura sea indian ocean whereas connections to the pacific ocean coral sea did not occur until about 8 cal ka bp

evidence for a larger sun with a slower rotation during the seventeenth century historical records suggest that during the seventeenth century the sun was subject to an anomalous scarcity of sunspots the maunder minimum1 this minimum was coincident with a severe temperature dip of the little ice age2 from which a relation between solar activity and terrestrial climate has been conjectured3 solar variability is also suggested by the regular variations in the thickness of annual laminae or varves in the late precambrian formation in south australia4 the climatic cycles recorded by the varves include the present 10 12 year solar cycle as well as deep minima with a mean period of 314 years a natural explanation of the solar cycle climate connection would be a modulation of the solar output radiation and possibly a change of the solar diameter5 6 by analysing a unique 53 year record of regular observations of the solar diameter and sunspot positions during the seventeenth century we have shown for the first time that the solar diameter was larger and rotation slower during the maunder minimum this finding sheds new light on the dynamo mechanism solar variability and the consequent effects on terrestrial climate

calcitization of mg ca carbonate and ca sulphate deposits in a continental tertiary basin calatayud basin ne spain diagenetic carbonates formed through early calcitization of evaporite gypsum anhydrite and or magnesium carbonate dolomite magnesite deposits have been identified throughout the tertiary calatayud basin ne spain the diagenetic carbonates consist in all cases of low magnesian calcite and are related to main sedimentary discontinuities which record episodes of significant subaerial exposure in the basin early calcite replacements predominate in sediments of the intermediate unit in central areas of the basin two types of diagenetic carbonates have been distinguished 1 laminated diagenetic carbonates in which the original structure of sequences formed of laminated magnesite dolomite and primary gypsum is preserved though transformed in calcite 2 brecciated diagenetic carbonates which resulted from extensive dissolution of lenticular gypsum macrocrystals accompanied by dedolomitization processes of dolomite host rock the replacement by calcite resulted from rapid transformation of evaporite deposits either at the contact of these deposits with overlying freshwaters or by percolating freshwater at very shallow burial depth stable isotope carbon and oxygen analyses of the diagenetic carbonates support influence of meteoric derived carbonate rich groundwater for their formation the meteoric isotope signature is supported by its comparison with the stable isotope values determined from diagenetic calcites formed after magnesite in evaporite sequences during the late pleistocene and holocene the diagenetic carbonate bodies formed as a result of a progressive change from highly to moderately concentrated saline lake waters this gradual evolution was related to a climatic shift from dry and hot to cooler and more humid conditions throughout the miocene a trend that has been also recognized in other large tertiary basins of the iberian peninsula in this period

palaeoecology and chronology of the vallesian late miocene in the eastern mediterranean region abstract during the last 30 years several new vallesian localities have been found in the eastern mediterranean and a great amount of fossils have been unearthed extensive studies on systematics and datation provided new data that allow a more detailed study of the vallesian in this area the biochronological and magnetostratigraphic data of the eastern mediterranean suggest that a the astaracian vallesian boundary in this area must be correlated to 10 7 ma at the moment b the early late vallesian mn 9 10 boundary to 9 7 ma and c the vallesian turolian mn 10 11 boundary cannot tightly be constrained because the relevant localities are not precisely dated the study of the vallesian faunas and their comparison to the modern ones allow an estimation of the palaeoecological conditions in the southeastern mediterranean the environment was open and dry during the whole vallesian in the black sea area it was relatively closed during the early vallesian mn 9 but became more open and dry during the late vallesian mn 10 on the other hand in western and central europe the environment remained closed and more forested until mid vallesian

mid neogene mediterranean marine continental correlations an alternative interpretation recent revised magnetostratigraphic and astrochronologic calibrations of several calcareous planktonic microfossil datum events in particular coccolithus miopelagicus and neogloboquadrina acostaensis combined with our magnetobiostratigraphic investigation of a 10 m thick section at ecotet near lyon france in which terrestrial micromammals vallesian zone mn9 are intercalated with calcareous nannoplankton and planktonic foraminifera belonging to zones nn6 nn8 and n14 15 m11 and m12 respectively lead us to question the recent recalibration by krijgsman et al 1996 eart planet sci lett 142 367 380 of the aragonian vallesian mn7 8 mn9 boundary with chron c5r 1r v11 1 ma and the lower upper vallesian mn9 10 boundary with chron c4ar 2n v9 6 9 7 ma ecotet with a uniform reverse polarity is shown to be assignable uniquely to chron c5r interregional correlation of ecotet with mediterranean terrestrial stratigraphies indicates that progonomys whose first occurrence fo has been traditionally placed in mediterranean mammal zone mn10 was already present in mediterranean zone mn9 at v11 4 ma and did not experience a 2 million year delay in its putative prochoresis from asia

sea level and environmental changes since the last interglacial in the gulf of carpentaria australia an overview abstract the gulf of carpentaria is an epicontinental sea maximum depth 70 m between australia and new guinea bordered to the east by torres strait currently 12 m deep and to the west by the arafura sill 53 m below present sea level throughout the quaternary during times of low sea level the gulf was separated from the open waters of the indian and pacific oceans forming lake carpentaria an isolation basin perched above contemporaneous sea level with outlet channels to the arafura sea a preliminary interpretation is presented of the palaeoenvironments recorded in six sediment cores collected by the images program in the gulf of carpentaria the longest core approx 15 m spans the past 130 ka and includes a record of sea level lake level changes with particular complexity between 80 and 40 ka when sea level repeatedly breached and withdrew from gulf lake carpentaria evidence from biotic remains foraminifers ostracods pollen sedimentology and geochemistry clearly identifies a final marine transgression at about 9 7 ka radiocarbon years before this transgression lake carpentaria was surrounded by grassland was near full and may have had a surface area approaching 600 km 300 km and a depth of about 15 m the earlier rise in sea level which accompanied the marine isotopic stage 6 5 transgression at about 130 ka is constrained by sedimentological and biotic evidence and dated by optical and thermoluminescence and amino acid racemisation methods

geomagnetic secular variation and the statistics of palaeomagnetic directions in this study we examine the role of palaeosecular variation psv in the use of statistics for palaeomagnetic studies and we provide new reliability criteria for palaeomagnetic poles or directions we first conclude that fisher statistics should not be applied to average palaeomagnetic directions but to virtual geomagnetic pole vgp distributions instead secondly we strongly advocate that typical properties of geomagnetic field behaviour are taken into account in the assessment of palaeomagnetic data sets the latitude dependent properties e s k provide useful guidelines for the reliability of a palaeomagnetic data set a reliable assessment of these properties depends on the sufficient number of palaeomagnetic samples being taken therefore as an additional instrument of assessing data sets we provide a n dependent a95 envelope bounded by an upper limit a95max and a lower limit a95min that helps to ascertain whether or not a distribution has sufficiently well sampled psv and therefore geomagnetic field behaviour applying these criteria is indispensable for studies of geomagnetic behaviour or for studies aiming at using tk03 gad for inclination error correction through the elongation inclination e i method for palaeomagnetic studies aimed at geological reconstructions they form helpful guidelines and increase the confidence in the rocks having faithfully recorded the field an analysis of published eastern mediterranean data shows that the vast majority of studies do not conform to the van der voo criteria in particular with respect to n and a95 we have provided criteria that are on the one hand more lenient lower n may still provide relevant information and on the other hand more strict for high n the criterion of a95 16 should be adapted to a requirement of lower a95 e g a95 80

rodents and climate 1 a model for estimating past temperatures using arvicolids mammalia rodentia abstract analysis of 253 extant mammalian local faunas shows that the number of arvicoline species in each fauna is related to temperature parameters the very high correlation allows us to propose a method to estimate the temperature for fossil faunas bearing arvicoline species from temperate areas to illustrate this method mean annual temperatures were estimated for late pleistocene hungarian localities and for a sequence from the baume de gigny jura france these were compared with results obtained by other techniques multivariate analysis of rodent associations and synthetic analysis of pollen faunal and sedimentological data