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

further evidence for inclination shallowing in red beds red beds and related shallow marine siliciclastic sediments within the extensional catalan neogene basins offer a unique opportunity to study the relationship between sediment anisotropy remanence acquisition and inclination shallowing on the basis of the dominant fabric features sedimentary facies are grouped into laminated massive and bioturbated the bulk susceptibility appears to be dominated by paramagnetic phyllosilicates and clay minerals the magnetic susceptibility fabric is dominantly foliated while the degree of anisotropy is very variable and is dependent on the facies type strong foliation dominates in the laminated sediments whereas weak anisotropy characterizes the bioturbated and massive mass flow facies moreover we observe a correlation between facies type and remanence inclination the undisrupted thinly laminated facies provides the most biased inclination values 20 as opposed to 60 of the expected geomagnetic field steeper inclinations are reported from bioturbated muds while the best record of the geomagnetic inclination is found in the weakly anisotropic mass flow deposits

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

evidence for tibetan plateau uplift before 14 myr ago from a new minimum age for east west extension important changes in south asian climate occurred in the late miocene epoch 8 myr ago 1 2 and these have been attributed by some researchers to uplift of the tibetan plateau at about the same time3 5 unfortunately this link has been difficult to test because the timing of plateau uplift remains poorly constrained by independent evidence one way to determine the minimum age of uplift is to establish the initiation age of the north striking normal fault systems in southern tibet that are widely regarded6 10 as being related to gravitational collapse of the tibetan plateau here we report an40ar 39ar age of 14 myr for hydrothermal mica from an extensional fracture belonging to such a fault system in north central nepal this age implies that east west extension began before 14 myr ago in at least some parts of the tibetan plateau suggesting that the plateau attained its high mean elevation well before late miocene time

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

magnetostratigraphy and small mammals of the late oligocene banovici basin in ne bosnia and herzegovina article i nfo a combined magnetostratigraphic and small mammal investigation was carried out to acquire better age control on the sedimentary infill of the banovici basin in bosnia and herzegovina although the dinarides occupy a crucial paleogeographic position bridging central europe and anatolia no detailed records of its small mammal fauna have been published until now a rich small mammal assemblage with over 500 molars was excavated from a section exposing marls and clays just underlying the basins main coal layer the fauna of this turija small mammal locality compares best with the uppermost oligocene to lowermost miocene localities from the european mp30 mn1 mammal zones and with anatolian zone b from central turkey a 160 m thick series of lacustrine sediments overlying the main coal layer in the nearby grivice section was sampled for paleomagnetic purposes the magnetostratigraphic pattern of the grivice section comprises a long reversed interval a subsequent short normal interval and another reversed interval the most logical correlation of this pattern to the late oligocene part of the geomagnetic polarity time scale gpts is to chrons c6cr c6cn 3n and c6cn 2r 24 to 23 2 ma this correlation implies a sedimentation rate of 20 cm kyr for the banovici basin and an age of approximately 24 ma for the turija mammal site the proposed correlation fits well with other magnetostratigraphically calibrated mammal records in western and central europe as well as anatolia and with the recalibrated ages of 24 95 0 05 ma and 24 72 0 04 ma for two basalt flows bracketing the enspel mp28 site in southern germany our results indicate that a limited exchange of fauna from central asia to western europe existed in late oligocene and miocene times

sediment production from forest road surfaces erosion on roads is an important source of fine grained sediment in streams draining logged basins of the pacific northwest runoff rates and sediment concentrations from 10 road segments subject to a variety of traffic levels were monitored to produce sediment rating curves and unit hydrographs for different use levels and types of surfaces these relationships are combined with a continuous rainfall record to calculate mean annual sediment yields from road segments of each use level a heavily used road segment in the field area contributes 130 times as much sediment as an abandoned road a paved road segment along which cut slopes and ditches are the only sources of sediment yields less than 1 as much sediment as a heavily used road with a gravel surface

late miocene paleoclimatology subantarctic water mass southwest pacific abstract the late miocene early pliocene paleoclimatic history has been evaluated for a deep drilled sediment sequence at deep sea drilling project site 281 and a shallow water marine sediment sequence at blind river new ealand both of which lay within the subantarctic water mass during the late miocene a major faunally determined cooling event within the latest miocene at site 281 and blind river coincides with oxygen isotopic changes in benthonic foraminiferal composition at dsdp site 284 considered by shackleton and kennett 1975 to indicate a significant increase in antarctic ice sheet volume however at site 281 benthonic foraminiferal oxygen isotopic changes do not record such a large increase in antarctic ice volume it is possible that the critical interval is within an unsampled section no recovery in the latest miocene two benthonic oxygen isotopic events in the late miocene 0 5 and 1 in the light direction may be useful as time stratigraphic markers a permanent negative carbon isotopic shift at both site 281 and blind river allows precise correlations to be made between the two sections and to other sites in the pacific region close interval sampling below the carbon shift at site 281 revealed dramatic fluctuations in surface water temperatures prior to a latest miocene interval of refrigeration kapitean and a strong pulse of dissolution between 6 6 and 6 2 0 1 m y which may be related to a fundamental geochemical change in the oceans at the time of the carbon shift 6 3 6 2 m y no similar close interval sampling at blind river was possible because of a lack of outcrop over the critical interval paleoclimatic histories from the two sections are very similar surface water temperatures and antarctic ice cap volume appear to have been relatively stable during the late middle early late miocene early late tongaporutuan by 6 4 m y cooler conditions prevailed at site 281 between 6 3 and 6 2 0 1 m y the carbon isotopic shift occurred followed within 100 000 yr by a distinct shallowing of water depths at blind river the earliest pliocene opoitian is marked by increasing surface water temperatures

atmospheric circulation upwelling and organic rich rocks in the mesozoic and cenozoic eras abstract by using the basic principles of atmospheric circulation and analogies from present circulation patterns it is possible to construct qualitative atmospheric circulation models on paleogeographic maps the wind patterns predicted by these models then serve as the basis for predicting the locations of ancient upwelling zones atmospheric circulation and upwelling models for seven geologic stages in the mesozoic and cenozoic were constructed and the distribution of the upwelling zones compared with the distribution of organic rich rocks for all time periods together the correlation was statistically significant when the individual time periods were analyzed separately the following pattern emerged significant correspondence between upwelling zones and organic rich rocks in the triassic middle early cretaceous to late cretaceous and middle paleogene to neogene no significant correspondence was found for the intervening times upwelling does not account for all organic rich rocks so called anoxic oceanic events and transgressions play an important role in their deposition it is suggested that upwelling contributes significantly to the pattern of organic rich rock distribution and is important in determining organic facies

the pannonian c hipparions from the vienna basin abstract the hipparion datum has been recognized as being a key geochronologic marker for early late miocene eurasian and african horizons the vienna basin pannonian c hipparions are the stratigraphically oldest basal mn9 ca 11 4 11 0 ma and we contend herein the most primitive of all old world hipparions we evaluate the stratigraphic context cheek tooth morphological characters paleodietary and paleoenvironmental context of the three pannonian c hipparion assemblages from gaiselberg atzelsdorf and mariathal austria we find that the gaiselberg and atzelsdorf are slightly more primitive than the mariathal hipparion assemblage and refer the first two assemblages to hippotherium sp while the mariathal assemblage is referred to hippotherium aff primigenium exhibiting some advanced characters that presage austrian and german later vallesian age we review the chronology and biogeography of the old world hipparion datum and evolutionary relationships of first occurring european west and south asian and north african hipparion to north american cormohipparion we evaluate and expand upon earlier paleodietary studies of pannonian c hipparions and determine that they were browser dominant mixed opportunistic feeders

sensitivity of eurasian climate to surface uplift of the tibetan plateau experiments with climate models are used to illustrate how earth s climate could be expected to change if surface uplift occurred the experiments contrast two climate simulations one with all continents at sea level and one with present day mountains and plateaus the simulations in the eurasia sector show that surface uplift increased elevation produces marked increases in the intensity of summer and winter monsoons of asia with development of wetter climates to the south and east of the tibetan plateau and drier climates to the north and west of the plateau there is a general cooling in northern polar latitudes comparison of simulations from two different models shows that the magnitude of the simulated changes depends upon how the models calculate the land surface hydrology and the ocean temperature the simulated changes produced by surface uplift agree in a general way with many geologic indicators of late cenozoic climate change the results suggest that surface uplift of mountains and platea

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

old world first appearance datum of hipparion horses late miocene large mammal dispersal and global events the magnetobiochronological dating of the late miocene hipparionine horses hipparion in the western mediterranean places its first appearance datum fad in the circum mediterranean region at the chron c5r at a minimum age of 11 1 ma this date challenges some of the widely accepted datings of this bioevent in western eurasia and is relevant to the discussion of the mode and tempo of hipparion dispersal the migration of the hipparion north american ancestor is related to the glacioeustatic sea level lowstand of the supercycle tb3 1 early tortonian and to the concurrent deep sea hiatus nh4 and oceanic 18 o isotopic event mi5 the hipparion dispersal was a conspicuous worldwide on land bioevent that was coeval with major late miocene oceanic and high latitude paleoclimatic global changes

hydrogen sulphide release to surface waters at the precambrian cambrian boundary changes in environmental conditions at the precambrian cambrian transition around 542 million years ago have been suggested as a possible explanation for the apparent rapid increase in abundance of multicellular organisms known as the cambrian explosion the nature of the environmental changes is still a matter of debate however wille et al now report molybdenum isotope signatures of black shales from two stratigraphically correlated sample sets with a depositional age of about 542 million years with the help of a box model of the oceanic molybdenum cycle they find that intense upwelling of hydrogen sulphide rich deep ocean water best explains the observed early cambrian molybdenum isotope signal this suggests that the early cambrian animal radiation may have been triggered by a major change in ocean circulation following a long period during which the ocean was stratified with sulphidic deep water this paper reports molybdenum isotope signatures of black shales from two stratigraphically correlated sample sets with a depositional age of around 542 million years the findings suggest that the early cambrian animal radiation may have been triggered by a major change in ocean circulation terminating a long period during which the proterozoic ocean was stratified with sulphidic deep water animal like multicellular fossils appeared towards the end of the precambrian followed by a rapid increase in the abundance and diversity of fossils during the early cambrian period an event also known as the cambrian explosion 1 2 3 changes in the environmental conditions at the precambrian cambrian transition about 542 myr ago have been suggested as a possible explanation for this event but are still a matter of debate1 2 3 here we report molybdenum isotope signatures of black shales from two stratigraphically correlated sample sets with a depositional age of around 542 myr we find a transient molybdenum isotope signal immediately after the precambrian cambrian transition using a box model of the oceanic molybdenum cycle we find that intense upwelling of hydrogen sulphide rich deep ocean water best explains the observed early cambrian molybdenum isotope signal our findings suggest that the early cambrian animal radiation may have been triggered by a major change in ocean circulation terminating a long period during which the proterozoic ocean was stratified with sulphidic deep water

evolution of the central catalan margin of the valencia trough western mediterranean abstract the evolution of the central catalan margin was conditioned by major fault activity and thermal processes generated by crustal thinning the continental margin structure is characterised by major ne sw striking southeast dipping basement faults which have given rise to a graben half graben and horst system these faults acted essentially as normal faults no major neogene strike slip activity has affected the continental margin although minor episodic variations from the dominant extensional regime to strike slip tectonics cannot be discounted two major structural evolutionary stages took place at the margin the transition from one stage to the other being gradual 1 rifting stage late oligocene to early burdigalian related to the opening of the valencia trough and from which originated both the barcelona and valles penedes half grabens 2 thermal subsidence stage late burdigalian to present generated by the subsequent crustal cooling and thinning fault activity during this stage was essentially concentrated in the major half graben bounding faults the sedimentary evolution of the central sector of the catalan margin was controlled by the tectonic and crustal evolution as well as by the successive sea level and paleoclimatic changes which affected the region drastic changes in the depositional systems took place during the transition from the rifting stage into the thermal subsidence stage during aquitanian langhian time characterized by an overall trend of pulsating encroachment of marine conditions over the continental margin a noticeable diversity of depositional systems alluvial lacustrine coastal evaporitic fan delta bay shelf carbonate platform systems developed from the latest serravallian up to the present the depositional framework was less varied due to a general lowering of sea level and to the final onlapping of most of older structural highs which are now buried below the miocene sediments two progradational terrigenous shelf talus systems separated by the messinian erosive surface developed during the latest serravallian tortonian and pliocene quaternary

a biostratigraphic zonation of the middle and upper siwaliks of the potwar plateau of northern pakistan abstract two biostratigraphic reference sections are designated for the middle and upper siwalik formations of northern pakistan the stratigraphic ranges of 41 mammalian taxa are established in the reference sections and the two sections are correlated to each other and to the standard magnetic polarity time scale by the magnetic polarity stratigraphy the resulting stratigraphic and magnetostratigraphic framework is used to define four contiguous biostratigraphic interval zones the proposed interval zones are bounded by five important faunal events which are identified in the reference sections the four proposed interval zones and the approximate ages in the reference sections of their lower and upper boundaries are 1 the hipparion s l interval zone 7 4 9 5 m y b p 2 the selenoportax lydekkeri interval zone 5 3 7 4 m y b p 3 the hexaprotodon sivalensis interval zone 5 3 2 9 m y b p and 4 the elephas planifrons interval zone 2 9 1 5 m y b p the paleomagnetic and biostratigraphic evidence indicates that the tatrot beds from which pilgrim developed his tatrot faunal zone are between 2 5 and 3 4 m y b p with a preferred maximum age of 2 9 m y b p the biostratigraphic evidence indicates the sethi nagri locality y311 the primary source of pilgrim s nagri faunal zone is in the hipparion s l interval zone the paleomagnetic evidence suggests an approximate age of 9 m y b p a major faunal event at 9 5 m y b p introduced equids suids and large giraffes from eurasia into the indain subcontinent a second more diffuse faunal event between 5 3 and 2 9 m y b p introduced several african taxa as well as equus and cervids from eurasia

paleoceanographic implications of miocene deep sea hiatuses miocene paleoceanographic evolution exhibits major changes resulting from the opening and closing of passages the subsequent changes in oceanic circulation and development of major antarctic glaciation the consequences and timing of these events can be observed in variations in the distribution of deep sea hiatuses sedimentation patterns and biogeographic distribution of planktic organisms the opening of the drake passage in the latest oligocene to early miocene 25 20 ma resulted in the establishment of the deep circumpolar current which led to thermal isolation of antarctica and increased global cooling this development was associated with a major turnover in planktic organisms resulting in the evolution of neogene assemblages and the eventual extinction of paleogene assemblages the erosive patterns of two widespread hiatuses ph 23 0 22 5 ma and nh 1 20 18 ma indicate that a deep circumequatorial circulation existed at this time characterized by a broad band of carbonate ooze deposition siliceous sedimentation was restricted to the north atlantic and a narrow band around antarctica a major reorganization in deep sea sedimentation and hiatus distribution patterns occurred near the early middle miocene boundary apparently resulting from changes in oceanic circulation beginning at this time deep sea erosion occurred throughout the caribbean hiatus nh 2 16 15 ma suggesting disruption of the deep circumequatorial circulation and northward deflection of deep currents and or intensification of the gulf stream sediment distribution patterns changed dramatically with the sudden appearance of siliceous ooze deposition in the marginal and east equatorial north pacific by 16 0 to 15 5 ma coincident with the decline of siliceous sedimentation in the north atlantic this silica switch may have been caused by the introduction of norwegian overflow water into the north atlantic acting as a barrier to outcropping of silica rich antarctic bottom water the main aspects of the present oceanic circulation system and sediment distribution pattern were established by 13 5 to 12 5 ma hiatus nh 3 coincident with the establishment of a major east antarctic ice cap antarctic glaciation resulted in a broadening belt of siliceous ooze deposition around antarctica increased siliceous sedimentation in the marginal and east equatorial north pacific and indian oceans and further northward restriction of siliceous sediments in the north atlantic periodic cool climatic events were accompanied by lower eustatic sea levels and widespread deep sea erosion at 12 to 11 ma nh 4 10 to 9 ma nh 5 7 5 to 6 2 ma nh 6 and 5 2 to 4 7 ma nh 7

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

palaeogene evolution of deformation in the northeastern iberian peninsula during the palaeogene alpine compression three units were differentiated in the studied area south of the ebro basin the catalan coastal range dominated by ne sw major basement faults with a sinistral movement the iberian range where the important basement faults have a nw se direction and a reverse movement often with a dextral component the linking zone between these two ranges where an e w dominant structural direction is marked by an array of folds and thrusts with a northward vergence in the mesozoic cover from the analysis of both these major structures and the small scale structures it can be deduced that the compression in the studied area has evolved from a nw se direction lower middle eocene to a n s direction and to a ne sw one uppermost oligocene the major structures are due to the n s compression later the stress field progressively changed to a distensive regime we suggest a relation between the compressive phases and the displacement direction of the iberian plate with reference to the european plate

kinematic evolution of the tethys belt from the atlantic ocean to the pamirs since the triassic abstract we present an updated series of kinematic reconstructions of the major plates around the tethys from the atlantic ocean to the pamirs between the early jurassic and the present this set is used elsewhere as a basis for paleogeographic maps of the entire region the problems related to the positions of the continents in the lower triassic are also discussed no direct analyses of magnetic anomalies and fracture zones in the atlantic have been made rather all available poles and rotations have been tested in order to eliminate or minimize possible kinematic errors the reconstructions are shown for nine key geological periods which correspond to well recognized magnetic anomalies except for the jurassic cretaceous boundary and the cretaceous tertiary boundary which correspond to interpolated positions paleolatitudes have been drawn using the study of westphal et al 1986 an attempt has been made to take into account the displacements caused by formation of the continental margins and basins by stretching the resulting relative vector of motions along the northern boundary of the tethys shows a significant change 80 m y ago left lateral motion with compression dominates before whereas right lateral motion with compression dominates after to the east rates of motion vary by a factor of three with time and four maxima can be clearly related to tectonic events in the late jurassic late cretaceous eocene and post middle miocene to the west north of apulia on the contrary the motion rate has not changed significantly since the early cretaceous and is close to 1 cm yr as an average these rather complex adjustments in rates and directions of relative motion are produced in great part through a complex migration of the africa eurasia pole of rotation and seem to be mostly governed by the tectonics of the tethys plate boundary

unlocking the ice house oligocene miocene oxygen isotopes eustasy and margin erosion oxygen isotope records and glaciomarine sediments indicate at least an intermittent presence of large continental ice sheets on antarctica since the earliest oligocene circa 35 ma the growth and decay of ice sheets during the oligocene to modern ice house world caused glacioeustatic sea level changes the early eocene was an ice free greenhouse world but it is not clear if ice sheets existed during the middle to late eocene doubt house world benthic foraminiferal 18o records place limits on the history of glaciation suggesting the presence of ice sheets at least intermittently since the earliest oligocene the best indicator of ice growth is a coeval increase in global benthic and western equatorial planktonic 18o records although planktonic isotope records from the western equatorial regions are limited subtropical planktonic foraminifera may also record such ice volume changes it is difficult to apply these established principles to the cenozoic 18o record because of the lack of adequate data and problems in stratigraphic correlations that obscure isotope events we improved oligocene to miocene correlations of 18o records and erected eight oxygen isotope zones oi1 oi2 mi1 mi6 benthic foraminiferal 18o increases which are associated with the bases of zones oil circa 35 8 ma oi2 circa 32 5 ma and mil circa 23 5 ma can be linked with 18o increases in subtropical planktonic foraminifera and with intervals of glacial sedimentation on or near antarctica our new correlations of middle miocene benthic and western equatorial planktonic 18o records show remarkable agreement in timing and amplitude we interpret benthic planktonic covariance to reflect substantial ice volume increases near the bases of zones mi2 circa 16 1 ma mi3 circa 13 6 ma and possibly mi5 circa 11 3 ma possible glacioeustatic lowerings are associated with the 18o increases which culminated with the bases of zone mi4 circa 12 6 ma and mi6 circa 9 6 ma although low latitude planktonic 18o records are required to test this these inferred glacioeustatic lowerings can be linked to seismic and rock disconformities for example we link 12 oligocene early late miocene inferred glacioeustatic lowerings with 12 of the sequence boundaries inferred eustatic lowerings of haq et al 1987

biochronology and biochron boundaries a real dilemma or a false problem an example based on the pleistocene large mammalian faunas from italy abstract reconstructing the neogene quaternary biostratigraphy in continental environments and recognising boundaries between successive mammalian faunal complexes is a problematic task the definition and application of biochronology has been often tainted by references to and inferences from biostratigraphy actually the discontinuities in the continental sedimentary record environmental conditions taphonomic and sampling biases are responsible for the fact that the stratigraphical order of the lowest and highest occurrences of fossil remains stratigraphic datum does not necessarily reflect the temporal order of actual first last appearances of taxa palaeobiological events in time nonetheless the first last appearance bioevents recorded by lowest highest occurrences of fossil remains in fossiliferous levels of different continental stratigraphical successions have been the principal foundation for establishing the biochronological setting of continental mammal faunas therefore from a theoretical point of view boundaries should be defined by the oldest and or youngest historical occurrence of one or more taxa what about an operational approach some examples of the italian faunas are presented focusing on the transition from the villafranchian to the galerian and from the galerian to the aurelian land mammal ages the results obtained indicate the difficulty of defining a stable scheme that can be applied for correlation by the international scientific community

magnetic stratigraphy of cenozoic terrestrial sediments and mammalian dispersal the existing literature on the correlation of the magnetic polarity timescale to vertebrate mammalian chronology for the cenozoic is reviewed for all continents except the soviet union the magnetostratigraphic data from north america is the most complete followed by the indian sub continent ten criteria for rating magnetostratigraphic studies are established and the papers reviewed are rated from 1 10 with 10 being the maximum score the timing of mammalian dispersal is examined against the background of information from magnetostratigraphic studies allied with radiometric dating north american land mammal ages are partly defined on immigrant taxa and the boundaries of the nalma are based on dispersal events it has been suggested that dispersal and evolutionary episodes observed in siwalik sediments were correlative to sea level change deduced from delta 18 o data from benthic foraminifera to test this possibility in the general case dispersal events into north america were determined by us