distribution of calcareous dinoflagellates from the maastrichtian to early miocene of dsdp site 357 rio grande rise western south atlantic ocean the evolution of calcareous dinoflagellate communities has been investigated for the latest cretaceous to earliest neogene interval of the mid latitude south atlantic in doing so the response of calcareous dinoflagellates to cenozoic climatic change has been addressed for the first time trends in species composition and distribution patterns of wall types indicate significant changes which correlate with major palaeoenvironmental modifications a first major shift concerning the relative abundance of species and wall types occurred across the cretaceous tertiary boundary the associations remained stable during the entire paleocene and eocene only in the late eocene did a dramatic decrease in temperature cause a slight diversification a second major shift in the abundance patterns occurred across the eocene oligocene boundary the early miocene warming is possibly reflected in the distinct increase in relative abundance of one species the assemblages of calcareous dinoflagellates evidently react to major climatic changes during the cenozoic these poorly investigated organisms may thus provide an important contribution to the understanding of earth s palaeoclimatic evolution

the biotic record of events in the marine realm at the end of the cretaceous calcareous siliceous and organic walled microfossils and macroinvertebrates abstract the calcareous micro and nannoplankton were severely affected at the end of the cretaceous as known from numerous sections but the change was not quite as sudden or drastic as sometimes claimed the organic walled phytoplankton seem to have survived the k t boundary event s better than other plankton little is known about the fate of siliceous plankton from the relatively few more or less complete sections across the k t boundary that are rich in benthic macroinvertebrates it is clear that there was a striking change at species level in some groups which is apparently directly attributable to the disaster that overtook the plankton and hence requires no additional explanation other groups however were already in decline if not completely extinct before the end cretaceous catastrophe took place

a sequence of events across the cretaceous tertiary boundary the lithological and biological sequence of events across the cretaceous tertiary k t as developed in thick and complete landbased sections and termed the standard k t event sequence is also found in many i sdp cores from all over the globe microtektite like spherules have been found in almost every core or outcrop with an iridium anomaly forming a worldwide strewnfield these microtektites are an excellent indicator of the k t boundary level the basal paleocene globigerina eugubma zone is nov established in all major ocean basins the difference in faunas between the pacific and tethys atlantic oceans may point to different recovery of the oldest paleocene planktonic foraminiferal assemblages in different ocean basins planktonic foraminifera and nannoplankton apparently show a different extinction recovery pattern at the k t boundary which suggests that the nannoplankton underwent final extinction later and recover later than planktonic foraminifera these patterns may be important for the evaluation of the type and range of environmental stress resulting from the hypothesized impact s at the k t boundary blocking of sunlight by the dust cloud still can account for the clear mass mortality at the k t boundary but seems less likely as explanation for the final nannoplankton extinction as photosynthetic nannoplankton appear to survive 1000 10 000 years into the tertiary

a gabbro to eclogite transition on flemsoy sunnmore western norway the migmatitic gneisses on the nordoyane islands western norway enclose abundant inclusions of coronitic gabbros and different types of country rock eclogites gabbros on flemsoy show a prograde step wise transition to eclogite via a transitional stage in which garnet and orthopyroxene form coronas between igneous olivine and sodic plagioclase relics after igneous plagioclase cumulates eclogitization proceeds by a complex set of continuous and discontinuous reactions opx and spinel form as transient phases but are consumed in various omphacite forming reactions during eclogite recrystallization relict igneous clinopyroxene shows a continuous increase in jd content while garnet becomes less calcic and more homogeneous from the corona stage to recrystallized eclogite the reactions are strongly diffusion controlled and have been enhanced locally by oxidation and the presence of a fluid phase and deformation while low strain areas of the gabbros remained coronitic whole rock chemistry mineral parageneses and calculated p t conditions are similar for the gabbroeclogites and two types of country rock eclogites some of the layered country rock eclogites appear to have been derived from the coronite bodies p estimates are in the order 15 20 kbar while kgarcpxd values suggest maximum t values of 750 60 c for the eclogite metamorphism in the area

detritus feeding as a buffer to extinction at the end of the cretaceous at the end of the cretaceous the principal animals that became extinct such as dinosaurs marine animals that lived in the water column and benthic filter feeders were in food chains tied directly to living plant matter animal groups less affected by extinction including marine benthic scavengers and deposit feeders small insectivorous mammals and members of stream communities were in food chains dependent on dead plant material the proposal that an asteroid or comet impact at the end of the cretaceous produced a dust cloud that cut off photosynthesis for several months is consistent with this pattern of extinction food chains dependent on living plant matter crashed while food chains based on detritus were buffered from extinction because there was a food supply adequate for the interval when photosynthesis was halted

end cretaceous brachiopod extinctions in the chalk of denmark the results of a detailed study of the brachiopods of the most complete cretaceous tertiary boundary in denmark nye kl v show an extinction pattern for this marine invertebrate group compatible with that reported for pelagic foraminifera and coccoliths and with the impact scenario the extinction is abrupt coinciding with the maastrichtian danian boundary there is no warning in the form of decreasing density decreasing diversity or early extinction of specialized groups the basal few meters of the danian are almost devoid of brachiopods and a danian brachiopod fauna starts almost as abruptly as the maastrichtian fauna disappeared the new fauna is similar to the maastrichtian as regards density and diversity and at maximum six species are common to both stages the northwest european masstrichtian chalk is composed mainly of the remains of coccoliths and pelagic foraminifera the mass extinction of these groups led to a total cessation of chalk production the chalk is overlain by a thin clay bed deposited partly under anoxic conditions this combination of anoxia and clay deposition coupled with a cessation of productivity led to the extinction of specialized groups such as the chalk brachiopods the surviving species included forms that could survive in well aerated shallow marine waters on substrates other than chalk

magmatic and metamorphic evolution of metagabbros in the munchberg massif n e bavaria the central gneiss complex of the munchberg massif consists of the liegendserie at the base and the hangendserie at the top metagabbros are found in the liegendserie eclogites occur in the hangendserie new isotope data revive the discussion whether a genetic relationship exists between metagabbros and eclogites in the munchberg massif it is possible to relate the two types of rocks to the same protoliths by variable degrees of crustal contamination and magmatic accumulation therefore a common magmatic origin may be assumed both the metagabbros and the eclogites were affected by amphibolite facies metamorphism the amphibolitization of the metagabbros was a prograde metamorphic event increasing temperature is indicated by inverse zonation of recrystallized plagioclase and increasing mg fe ratios in garnet from core to rim geothermobarometry yields a temperature of 600 c and a pressure of about 11 kbar for the peak of metamorphism in contrast the eclogites underwent a first high pressure stage at a minimum pressure of 14 kbar and a temperature estimated at 600 c and were subsequently overprinted under amphibolite facies conditions at 10 kbar 700 c a common magmatic origin of metagabbros liegendserie and eclogites hangendserie of the munchberg massif can no longer be discarded however the converging p t t paths reflect a different geodynamic evolution of the liegendserie and the hangendserie after magmatism and before amphibolite facies metamorphism

calcareous nannofossil extinction and survivorship across the cretaceous paleogene boundary at walvis ridge odp hole 1262c south atlantic ocean abstract site 1262 in the south atlantic ocean has provided a stratigraphically continuous deep cretaceous paleogene boundary sequence high resolution calcareous nannofossil quantitative analyses were carried out across the k p boundary and provided a remarkable record of the abrupt and catastrophic extinction the calcareous nannofossil assemblages are abundant and well preserved allowing to obtain a precise bioevent sequence and to document in detail the survivors and victims and the subsequent recovery across the k p boundary late maastrichtian diversity and absolute abundance is high and no decrease towards the boundary has been observed the relative abundance of cretaceous species does not suffer important changes during the latest maastrichtian however the increase in abundance of cool water taxa paralleled with a decrease of warm water taxa in the uppermost 2 cm of the maastrichtian revealed a pulse of surface water cooling the k p boundary is marked by an important decrease in calcareous nannofossil absolute abundance the increase of cretaceous persistent species such as cyclagelosphaera reinhardtii together with the dinoflagellate cysts of thoracosphaera operculata and the appearance of the new paleocene taxa cyclagelosphaera alta and biantholithus sparsus these events are followed by the successive relative abundance increases of other cretaceous survivors as zeugrhabdotus sigmoides markalius inversus and biscutum recognized as r selected taxa adapted to eutrophic and cold water environments in the early danian several first occurrences of small new paleocene species have been observed calcareous nannoplankton evolutionary attempts to colonize vacant niches left by the extinct cretaceous species only some forms succeed and become ancestors to the cenozoic assemblages the other disappear in few kiloyear the presence of a reworking mixing interval above the k p boundary hampered to unequivocally interpret if the few cretaceous vanishing taxa may have survived for a very short time after the k p extinction

structural properties of the san jacinto fault zone at blackburn saddle from seismic data of a dense linear array we image the san jacinto fault zone at blackburn saddle using earthquake waveforms recorded by a 2 km across fault linear array with 108 three component sensors separated by 10 30 m the length and spatiotemporal sampling of the array allow us to derive high resolution information on the internal fault zone structure with spatial extent that can be merged with regional tomography models across fault variations in polarization amplitude and arrival time of teleseismic p waves indicate abrupt changes in subsurface structure near the surface trace of the fault sensor bs55 and 270 m to the northeast sensor bs34 analysis of fault zone head waves from local events reveals the existence of a deep bimaterial interface that extends from the array to at least 50 km southeast and has a section with 10 velocity contrast this analysis also corroborates the teleseismic results and indicates a broad damage zone primarily northeast of the fault bounded by a shallow bimaterial interface near bs34 that merges with the deep interface detection and waveform inversions of love type fault zone trapped waves generated by local events indicate a trapping structure within the broader damage zone with width of 150 m velocity reduction of 55 from the surrounding rock and depth extent of 2 km the performed analyses provide consistent results on the subsurface location of the main seismogenic fault and properties of a major bimaterial interface and damage structure the imaged fault zone properties are consistent with preferred propagation direction of earthquake ruptures in the area to the northwest

partially retrograded eclogites of the munchberg massif germany records of a multi stage variscan uplift history in the bohemian massif eclogites with a wide range in bulk composition are present in the munchberg massif part of the variscan basement of the bohemian massif in north east bavaria new analyses of the primary phases garnet omphacite phengite and amphibole as well as the secondary phases clinopyroxene ii various amphiboles biotite phlogopite plagioclase margarite paragonite prehnite and pumpellyite reveal a complex uplift history new discoveries were made of samples with very jadeite rich primary omphacite as well as a secondary omphacite in a symplectite with albite various geothermobarometric techniques together with thermodynamic databases incorporating separately determined activity composition values and experimental data have clustered the minimum conditions for the primary assemblages to the p t range 650 60 c 14 3 1 kbar however jadeite in omphacite kyanite paragonite in phengite and zoisite grossular in garnet kyanite quartz relationships suggests pressures of 25 28 kbar at the same temperatures the fact that the secondary omphacite plagioclase assemblage yields pressures within a few hundred bars of the minimum pressures for the plagioclase free assemblages strongly suggests that the minimum values are serious underestimates zoning inclusion suites and breakdown reactions of primary phases in addition to new minerals formed during uplift define a polyphase metamorphic evolution which from geochronological evidence occurred solely within the variscan cycle the complex breakdown in other bohemian massif eclogites and the distinct variation in their temperatures during uplift suggest a multi stage thrusting model for the regional evolution of the eclogites such an evolution has significance with respect to incorporation of mantle slices into crustal sequences and fluid derivation from successively subducted units possibly driving the breakdown reactions

terminal cretaceous environmental events the geologic record of terminal cretaceous environmental events indicates that iridium and other associated elements were not deposited instantaneously but during a time interval spanning some 10 000 to 100 000 years the available geologic evidence favors a mantle rather than meteoritic origin for these elements these results are in accord with the scenario of a series of intense eruptive volcanic events occurring during a relatively short geologic time interval and not with the scenario of a single large asteroid impact event

eclogite facies relics and a multistage breakdown in metabasites of the ktb pilot hole ne bavaria implications for the variscan tectonometamorphic evolution of the nw bohemian massif complex reaction textures in coronitic metagabbros and retrograded eclogites of the ktb pilot and an adjacent drilling provide evidence for a multistage metamorphic history in the variscan basement of the nw bohemian massif the eclogites show complete metamorphic recrystallization leaving no textural or mineral relics of their igneous precursors in contrast textural relics of the igneous protolith are still preserved in the metagabbros where the metamorphic overprint under high pressure conditions achieved only partial replacement of the initial assemblage plagioclase augite amphibole olivine or orthopyroxene ilmenite to form the eclogite facies assemblage garnet omphacite kyanite zoisite quartz rutile the garnets in the metagabbros occur in the typical necklace fashion at the borders between the original plagioclase and mafic phase domains in the same rocks omphacite formed by a topotactic reaction mechanism replacing igneous augite as well as in smaller grains at the margins of the texturally igneous clinopyroxene where it occurs without fixed orientation with respect to the relict phase both eclogites and metagabbros show a partial breakdown under high pressure granulite transitional to high pressure amphibolite facies conditions during which omphacite broke down to vermicular symplectites of diopside plagioclase a later pervasive medium pressure metamorphism under amphibolite facies conditions led to the development of assemblages dominated by hornblende plagioclase titanite phases prevailing in the overwhelming majority of the surrounding metabasites subsequent vein associated retrogression produced minerals typical of the greenschist to zeolite facies all metamorphic stages may be represented in a single thin section but although the overall reaction sequence is apparent the obvious disequilibrium in the rocks makes the use of conventional geothermobarometry difficult however calculations made by assuming an approach to domainal equilibrium show that both the eclogite facies and early breakdown occurred above 10 kb as the metamorphic unit hosting these particular metabasites is generally characterized by pressures below 10 kb these results have important implications for understanding the tectonometamorphic evolution of the region the relationship between the studied rocks and other units in the nw bohemian massif exhibiting a multistage metamorphic evolution is discussed and possible tectonic models evaluated

maastrichtian molluscan biostratigraphy and extinction patterns in a cretaceous tertiary boundary section exposed at zumaya spain ammonites and inoceramid bivalves were stratigraphically collected from lower and upper maastrichtian units in continuous exposure along the seacoast near zumaya spain three ammonite teilzones can be recognized 1 a lower zone correlative with parts of the globotruncana ganserri planktonic foram zone and characterized by numerous inoceramids among three different species as well as pachydiscus neubergicus a noded baculites polyptychoceras sipho and hauericeras renbda 2 a middle zone that has no inoceramids but that has pachydiscus fresvillensis and p neubergicus and is correlative with the lower parts of the abathomphalus mayaroensis zone planktonic foram and 3 an upper zone that has p colligatus and is correlative with the upper parts of the a mayaroensis zone these three teilzones may be the basis for a tethyan facies wide ammonite zonation of the maastrichtian the four main components of the fossil record at the zumaya section show differing range characteristics with respect to the cretaceous tertiary k t boundary exposed in this section the inoceramids disappear at the top of the lower maastrichtian except for the small enigmatic form tenuipteria which has a restricted range in the uppermost levels of the cretaceous ammonites range upward to levels approximately 10 m below the boundary most larger planktonic forams and many nannofossil species disappear within several centimetres of the boundary echinoid fossils range up to and possibly across the k t boundary the zumaya section is thus characterized by apparently nonsynchronous or graded extinctions of most of its fossil content

review of the upper cretaceous lower tertiary sequence on seymour island antarctica the thick sequence of fossiliferous marine and non marine sandstones and siltstones on seymour i represents the most complete well exposed section of upper cretaceous to lower tertiary rocks known in the southern hemisphere the succession has been divided into the upper campanian to possibly lowermost tertiary marambio group comprised of the lopez de bertodano and sobral formations and the lower tertiary cross valley and la meseta formations of the seymour island group the lopez de bertodano formation consists of c 1067 m of medium grained to silty concretionary sandstones of middle campanian to possibly maestrichtian age and the sobral formation of c 210 m of medium to coarse grained glauconitic concretionary sandstones the precise age of the sobral formation is uncertain but may be maestrichtian to possibly danian the lower 110 m of the seymour island group consists of non marine gravelly to pebbly sandstones and tuffaceous plant bearing siltstones of the cross valley formation overlying which are 450 m of fine grained marine sandstones and siltstones with interbedded fossiliferous pebbly conglomerates recent studies of the diverse and abundant faunas and floras of the seymour island group have shown that they are older than previously thought the cross valley formation being palaeocene and the la meseta formation late eocene to possibly earliest oligocene

a tem study of disequilibrium plagioclase breakdown at high pressure the role of infiltrating fluid high pressure metamorphism 600 c 20 kbar of the allalin gabbro western alps resulted in the breakdown of plagioclase an63 to fine grained zoisite jadeite kyanite and quartz in rare cases this reaction failed to reach completion the resulting textures of partial reaction have been studied by transmission and analytical electron microscopy in localised regions of a plagioclase crystal where the extent of reaction is 10 only zoisite developed and the orientation relationship left 100 right text zo left 101 right text p1 1 and left 012 right text zo left 010 right text p1 1 is frequently present in regions where 10 50 of plagioclase has transformed the reaction plagioclase h2o zoisite kyanite quartz nasica 1al 1 pl has occurred the systematic orientation relationship between plagioclase and zoisite is absent at 50 transformation complete breakdown of plagioclase occurred in localized micron scale domains by the reaction plagioclase h2o zoisite jadeite kyanite quartz and the reaction products are variably orientated with respect to each other incomplete reaction together with the concentration of reaction products around cracks in original plagioclase grains suggests that extent of reaction was controlled primarily by the availability of h2o the textural observations are interpreted in terms of two possible disequilibrium reaction models 1 plagioclase persists metastably with its original igneous composition to a pressure 17 kbar at 600 c reaction to the equilibrium assemblage then develops adjacent to cracks in response to the presence of aqueous fluid at intracrystalline sites only partial reaction occurs because jadeite and sometimes kyanite and quartz fail to nucleate for kinetic reasons 2 localized regions of a plagioclase crystal partially equilibrate at several stages during the increase of pressure 9 17 kbar at 600 c possibly due to discrete episodes of fluid infiltration in both these models the extent of reaction may be limited by nasi caal interdiffusion in plagioclase

the cretaceous tertiary transition the fossil sequences from cores across the cretaceous tertiary boundary show a range of transition times and transition time intervals depending on the fossil indicators and the location of the site these variations together with the pattern of iridium distribution with depth at some sites differences in total amounts of iridium variations in noble metal abundances normalized to extraterrestrial concentrations the depositional effects that might be expected in a reducing environment and the clay mineralogy of the boundary layer clays put into question the interpretation that an extraterrestrial event was the cause of the faunal changes and the iridium anomaly in the vicinity of the cretaceous tertiary transition it seems more likely that an explanation for the changes during the transition will come from continued examination of the great variety of terrestrial events that took place at that time including extensive volcanism major regression of the sea from the land geochemical changes and paleoclimatic and paleoceanographic changes

the end of the cretaceous sharp boundary or gradual transition evidence indicates that the cretaceous tertiary boundary is very sharp and within the limits of resolution it is apparently synchronous at the various boundary localities arguments to the contrary particularly those of officer and darke are shown to invalid

femg partitioning between coexisting garnet and phengite at high pressure and comments on a garnet phengite geothermometer abstract the fe mg exchange reaction between coexisting garnet and phengite has been studied by reacting a natural phengite mg 67 in the presence of quartz and water at pressures of 20 35 kb and temperatures of 800 1000 c compositions of coexisting garnet and mica indicate a linear relation between both the inkd fe mg garnet fe mg phengite and temperature and inkd and pressure in the above p t range this fe mg exchange reaction between garnet and phengite is shown to be dependent on the ca content of the garnet and on the mg number of the bulk composition these two composition effects have been studied by usin phengitic mica mixes with mg numbers of 23 and 46 and by using a synthetic basaltic composition the overall results allow broad empirical calibration of separate geothermometers for pelitic and basaltic systems respectively however because of non ideality in the exchange reaction this geothermometer should not be used in any practical application outside the composition ranges studied also careful consideration of the presence of fe3 in phengite must be made if the fe3 content of the natural phengite is unknown then the temperatures obtained will be maximum temperatures only

prograde retrograde p t t deformation path of austroalpine micaschists during variscan continental collision eastern alps a complete prograde p t path defined by 10 calculated p t fields in succession is recognized from metapelites by using geothermobarometry on garnet bearing assemblages with microstructural control overstacking of several tectonic units during an early variscan continental collision explains the complex prograde p t history isostatic uplift and deformation controlled the retrograde p t path deformation with changing character acted continuously during all stages of the evolution of the austroalpine basement complex after the intrusion of caledonian granitoids metapelites and magmatic rocks suffered a shearing deformation d1 d2 which produced sheath folds as well as the main foliation s2 spessartine rich first generation garnets situated in microlithons enclosed by s2 record the onset of shearing under increasing high pressure low temperature conditions 7 kbar 380 c geothermobarometry on second generation garnets which have been rotated during growth indicates isothermal decompression from 9 kbar to 5 kbar 500 c and subsequent recompression heating during continuing shearing this is explained by overthrusting of a tectonic unit unit 2 from ne to sw upon the micaschist unit unit 1 followed by isostatic uplift and further overstocking of a third unit unit 3 the resulting pmax of 12 kbar at 650 c and further increasing temperatures up to 680 c accompanied by decompression have been calculated using a third generation of garnets these high pressure high temperature conditions may explain the occurrence of eclogitic metabasites in adjacent regions staurolite and kyanite first appeared under decreasing pressures at the last stage of prograde p t evolution shortening deformation d3 and simultaneous growth of typical amphibolite facies minerals staurolite 2 kyanite 2 sillimanite andalusite occurred during the retrograde path a final step of variscan evolution was marked by an oppositely directed shearing d4 at t 300 c and p 3 kbar possibly indicating backthrusting or extension apart from acid intrusions no signs of a previous caledonian thermotectonic history were found in the area to the south of the defereggen antholz vals line

metamorphic evolution of the eiksunddal eclogite complex western norway and some tectonic implications the metamorphic evolution of the western gneiss region of norway wgr can be evaluated from examination of eclogites formed as an integral part of the gneiss terrain ie in situ petrologic data from one of the larger country rock eclogites within the northwestern part of wgr have been used to construct a p t t path for this crustal volume textural relations as well as mineral composition and zonation suggest an early period of amphibolite facies conditions followed by movement along a very steep positive p t gradient towards very high pressure p 25 kb and moderate temperature t 600 c orthopyroxene coexisting with garnet at such conditions was poor in al 0 5 wt al2o3 and is preserved in the cores of orthopyroxene grains in garnet websterites the increasing al content of orthopyroxene towards garnet and increasing edenite substitution rimwards in zoned amphiboles suggest a period of decompression accompanied by heating towards the metamorphic maximum at t 750 c p 20kb garnet zoning reflects a general prograde history but the reactions that control the zoning are insensitive to pressure changes jadeitic pyroxenes may have formed in the gneisses at p max but would revert to plagioclase subsequent to the metamorphic maximum giving rise to the observed mineralogy further decompression and cooling continued towards high rank amphibolite facies conditions this p t t path reflects crustal thickening to 80 90 km during caledonian time the uplift path is qualitatively similar to theoretically derived paths in which uplift is assumed to be controlled by erosion however uplift following the metamorphic maximum may have been accelerated by a period of suture progradation

late cretaceous and paroxysmal cretaceous tertiary extinctions the various geological signatures at cretaceous tertiary time including iridium and other associated elements microspherules and shock deformation features are compatible with the suggestion that the transition is marked by a period of intense volcanism the volatile emissions from this volcanism would lead to acid rain reduction in the alkalinity and ph of the surface ocean global atmospheric temperature changes and ozone layer depletion these environmental effects coupled with those related to the major sea level regression of the late cretaceous provide the framework for an explanation of the selective nature of the observed extinction record

end cretaceous mass extinction event argument for terrestrial causation the end cretaceous mass extinctions were not a geologically instantaneous event and were selective in character these features are incompatible with the original alvarez hypothesis of their being caused by a single asteroid impact that produced a world embracing dust cloud with devastating environmental consequences by analysis of physical and chemical evidence from the stratigraphic record it is shown that a modified extraterrestrial model in which stepwise extinctions resulted from encounter with a comet shower is less plausible than one intrinsic to the earth involving significant disturbance in the mantle

an expanded cretaceous tertiary transition in a pelagic setting of the southern alps central western tethys abstract an integrated micropalaeontological planktonic foraminifera and calcareous nannofossils mineralogical and stable isotope investigation was carried out across the cretaceous tertiary k t boundary in a previously undescribed hemipelagic section forada section cropping out in the piave river valley southern alps belluno province ne italy our results suggest that an apparently complete k t transition with an expanded basal danian is preserved in the forada section the k t boundary is marked by a ca 1 5 cm thick clay interval intercalated in the pelagic carbonates of the scaglia rossa formation the boundary clay characterised by an iridium anomaly is constituted by a basal 1 2 mm thick green layer and an overlying red layer below the boundary clay the calcareous nannofossil micula murus zone and the planktonic foraminiferal plummerita hankteninoides zone that characterise the terminal maastrichtian in complete sections have been identified virtually all the calcareous plankton biohorizons normally utilised in the early danian have been recognised interestingly the ranking of the various biohorizons is the same observed elsewhere if considering the single plankton groups separately while several inconsistencies emerge if considering the relative succession of the two calcareous plankton groups simultaneously we caution to infer hiatuses on a section based only on the spacing of the biohorizons of a single group because of the risk of diachroneities in the stressed early danian environment by comparing the distance of the key biohorizons i e the first occurrence fo of cruciplacolithus primus and the last occurrence lo of parvularugoglobigerina eugubina from the boundary clay at forada and in other complete classical sections we have inferred that the early danian is expanded in the forada section the section seems ideally suited for studying the recovery pattern of the pelagic ecosystem and calcareous plankton communities in the aftermath of the k t catastrophe in a pelagic setting of the western central tethys the adaptive radiation of planktonic foraminifera was very rapid in contrast with the delayed diversification of coccolithophores the latter show a ca 21 cm thick dead zone that is followed by a long lasting survival interval ca 180 cm thick that might represent some 200 kyr dominated by persistent cretaceous coccolithophores and calcareous dinoflagellate thoracosphaera spp the temporal pattern in recovery of the coccolithophore and planktonic foraminiferal communities is decoupled as well pointing to their varying sensitivities to the k t perturbation it appears that the ecospace occupied by coccolithophores in the terminal maastrichtian was occupied in the initial danian by the calcareous dinoflagellates thoracosphaera spp that remained a significant component of the assemblage up to the base of the prinsius dimorphosus zone of romein romein a j t 1979 lineages in early paleogene calcareous nannoplankton utrecht micropaleontological bulletins 22 231 pp probably in the early chron c29n on the contrary planktonic foraminifera seem to reach stable conditions earlier in the late cruciplacolithus primus zone the early danian interval considered is also characterised by low sr ca ratio of the biogenic carbonates that would suggest dramatically low coccolithophore productivity conditions in agreement with previous flux studies we speculate that the altered ecological structure of phytoplankton community and the low productivity of coccolithophores severely affected the efficiency of the transfer of organic carbon from the photic zone to the deep ocean thus supporting the early danian living ocean model of d hondt et al d hondt s donaghay p zachos j c luttenberg d lindinger m 1998 organic carbon fluxes and ecological recovery from the cretaceous tertiary mass extinction science 282 276 279

eclogites in the french palaeozoic orogen geodynamic significance abstract eclogites are widespread in the devonian internal zone of the french palaeozoic orogen they occur in different tectonic settings either in high pressure low temperature or in high pressure high temperature environments they are tectonically incorporated into several major allochthonous units as demonstrated either by their blastomylonitic texture or by their being in evident disequilibrium with their country rocks the protoliths of the presently well identified eclogite bearing series present different typical associations depending on their present location the igneous series include within plate basalts normal and transitional morbs and even calc alkaline rocks they were erupted mostly during the palaeozoic although they sometimes contain inherited precambrian zircons further some of them may be remnants of old precambrian oceanic crust most of the eclogitic parageneses were generated during the earliest silurian tectonometamorphic climax either in low temperature or in high temperature conditions later they followed various retrograde courses in still geographically distinct low temperature or high temperature associations the basic rocks in the leptynolitic amphibolitic complex and particularly the eclogites thus provide sufficiently clear evidence to support a new geodynamic scenario implying one or several subordinate narrow tensional zones in a thinned but well developed continental crust rather than in a true oceanic domain

biotic geochemical and paleomagnetic changes across the cretaceous tertiary boundary at braggs alabama exposed near braggs alabama is one of the few well studied nearly continuous shallow marine cretaceous tertiary boundary sections it allows a glimpse of the biotic and environmental changes that occurred in the latest cretaceous to earliest paleocene paleomagnetic strontium isotopic and biostratigraphic data closely constrain the age of a series of lithologic geochemical and biotic variations and suggest that no more than 100 200 ka could be missing at the boundary a major reduction in macrofaunal diversity associated with lithofacies changes occurs prior to but within 300 ka of the nannofossil defined boundary approximately 40 of the apparent faunal reduction is attributed to the lazarus effect faunal and floral assemblages trends in carbon isotopic composition of benthic invertebrates and lithologic characteristics indicate that a latest maestrichtian regression culminated near the boundary chron c29r micula murus zone significantly later than recent estimates water depths at this site remained shallow during the subsequent early paleocene zone np1 transgression and did not reach depths equivalent to those of the late maestrichtian until zone np2 relatively minor climatic changes across the boundary are suggested by a 4 c cooling trend seen in the oxygen isotope paleotemperatures a high resolution 87 sr 86 sr record from well preserved macrofossil calcite shows a pattern of smooth variation and elevated values near the boundary however the early paleocene spike of other workers was not found