palaeobiotope analysis and palaeoenvironmental reconstruction of the palaeocene early eocene ostracodes from east central sinai egypt

the mid cretaceous earth paleogeography ocean circulation and temperature atmospheric circulation a reconstruction of the global paleogeography of the mid cretaceous 100 m y ago including adjustment of continental outlines to account for microplate movements cmstal shortening and accretion in mid cretaceous and later orogenic regions is described and a map presented on the modified continents coastlines and significant mountain ranges are added this paleogeography is used as a framework for a reconstruction of ocean surface circulation and temperature distribution then the main features of the atmospheric circulation are deduced using the paleogeography and ocean temperatures as boundary conditions relative to the present these features are a much weaker westerly wind belt and greater seasonality of wind patterns leading to more extreme surface climates over the continents slightly equatorward positions of the subtropical anticyclones and monsoonal regimes over the continental margins bordering tethys and the central atlantic a comparison of the results with climatic evidence from t

palaeoecology of ostracods from the late cretaceous from northeastern brazil and its relation to sequence stratigraphy abstract ostracods from the turonian campanian interval of jandaira formation potiguar basin ne brazil were analysed in terms of diversity palaeocology and their potential application in sequence stratigraphy ternary plots of cytheroidea cytherelloidea bairdioidea and cypridoidea ccbc plots were assembled to determine the palaeobathymety purposes our results demonstrate the existence of four major palaeoenvironments as follows mixohaline marine 1 marine 1 marine 2 and mixohaline marine 2 which differ in the taxonomic composition abundance and ecological preferences of their assemblages in horizons where the fauna had consistent recovery it was possible to infer system tracts and stratigraphic surfaces the inferred sequence boundaries are indicated by important faunal changes expressed mainly by reduction in diversity differences in the assemblages compositions and their ecological preferences the maximum flooding surfaces mfs were marked by high diversity of marine stenohaline taxa the results of this study reinforce the usefulness of ostracod assemblages in sequence stratigraphy interpretation in the marine and marginal marine successions

paleocene sea level and productivity changes at the southern tethyan margin el kef tunisia integrated analysis of quantitative distribution patterns of organic walled dinoflagellate cysts dinocysts and benthic foraminifera from the paleocene el kef section nw tunisia allows the reconstruction of sea level and productivity fluctuations our records indicate that the environment evolved from an initially oligotrophic open marine outer neritic to upper bathyal setting towards a more eutrophic inner neritic setting influenced by coastal upwelling by the end of the paleocene an overall second order change in paleodepth is reflected by both microfossil groups from the base of planktic foraminifera zone p4 onwards the main phase of shallowing is evidenced by an increase of inner neritic dinocysts of the areoligera group disappearance of deeper water benthic foraminifera and increasing dominance of shallow marine taxa several buliminids haplophragmoides spp trochammina spp the total magnitude of this shallowing is obscured by interaction with a signal of eutrophication but estimated to be around 150 m from 200 to 50 m superimposed on the overall trend third order sea level fluctuations have been identified and correlated to sequences in other regions paleoproductivity indicators notably protoperidinioid dinocysts and buliminids show a trend from an oligotrophic to a eutrophic setting d 2005 elsevier b v all rights reserved

the cretaceous tertiary boundary stratotype section at el kef tunisia how catastrophic was the mass extinction abstract the cretaceous tertiary k t boundary stratotype section at el kef tunisia represents the most complete and expanded sedimentary record across this important mass extinction horizon presently known high resolution analysis of planktic foraminifera in two outcrops el kef i stratotype and el kef ii along with comparisons between planktic and benthic foraminifera calcareous nannofossils ostracods pollen and spores and dinoflagellates indicate that major changes across the k t boundary are registered only in benthic and planktic foraminifera and calcareous nannofossils biotic changes in benthic foraminifera are unique to el kef and similarly shallow continental shelf sections and appear to be the result of a sea level regression in the latest maastrichtian followed by a sea level rise across the k t boundary that was accompanied by expansion of the local oxygen minimum zone omz biotic changes in planktic foraminifera appear partly related to these conditions also but in general reflect more global oceanographic changes for instance species extinctions are gradual and selective as observed in k t sections worldwide rather than random and abrupt although there is a 69 decline in species richness between 25 cm below and 10 cm above the k t boundary only rare species disappeared their combined relative abundance constitute less than 20 of the total population about 52 of these extinct taxa 8 of the population are large ornate morphologically complex tropical subtropical forms that lived at or below the thermocline no planktic foraminifera from this depth range survived the k t boundary event all survivor taxa were surface dwellers living within the photic zone their relative abundance 80 dominates both cretaceous and early tertiary populations these data indicate that the k t biotic record in the shallow continental shelf section at el kef was significantly influenced by local conditions which combined with the latest maastrichtian sea level regression and subsequent sea level rise resulted in shallowing of the local omz relative to the sea surface shallowing of the local omz lead to the selective disappearance of benthic faunas and may have adversely affected the surviving photic zone dwellers the selective nature of species extinctions however appear to be related partly to long term global oceanographic changes which were accelerated at the k t boundary possibly by a bolide impact

the krithe problem first test of peypouquet s hypothesis with a redescription of krithe praetexta praetexta crustacea ostracoda the ostracode genus krithe is generally regarded as an index for deeper water but its known depth range is 15 4500 m further uncertainty is caused by anterior vestibule variations in otherwise identical specimens peypouquet 1977 suggested that interior vestibule size in krithe is inversely correlated with the dissolved oxygen content of the ambient seawater this hypothesis if true would enable more precise interpretations of paleodepth by means of fossil krithe assemblages we made a partial test of the hypothesis by examining living krithe praetexta praetexta collected during may 1988 at 45 m depth in the gullmar fjord on the west coast of sweden our paper includes a description of this taxon and notes some associated ecological factors in gullmar fjord we used a quantitative method to describe their vestibules based on linear measures obtained by rapid image digitization a canonical variate analysis of the measures clearly indicates four different groups one for each valve right and left and one for each sex all our specimens belonged to peypouquet s b12 morphotype the actual dissolved oxygen values in gullmar fjord during may were very close to those predicted by peypouquet for the b12 morphotype but values during june were rather less than his prediction possibly the imperfect agreement can be related to variations in food supply and other sources of ostracode shell calcium thus although the test has proved confirmatory as far as it goes we believe that further study at different depths and latitudes is required the elements of the ostracode fauna are illustrated

the end cretaceous in the southwestern tethys elles tunisia orbital calibration of paleoenvironmental events before the mass extinction an integrated study of magnetic mass susceptibility ms bulk stable isotopes and calcareous nannofossil paleoecological changes is undertaken on the late maastrichtian of the elles section tunisia spanning the last ca 1 myr of the cretaceous a cyclostratigraphic analysis reveals the presence of milankovitch frequencies and is used for proposal of two distinct orbital age models and to provide ages of important stratigraphic horizons relative to the age of the cretaceous paleogene boundary k pgb principal component analysis pca performed on the nannofossil assemblage reveal two main factors pca1 mostly representing fluctuations of d rotatorius p stoveri lithraphidites spp retecapsa spp staurolithites spp micula spp and pca2 mostly representing fluctuations of a regularis c ehrenbergii micula spp rhagodiscus spp w barnesiae and zeugrhabdotus spp variations in pca1 and pca2 match changes in bulk 13c and 18o respectively and suggest changes in surface water fertility and temperatures and associated stress the variations in abundances of high latitude taxa and the warm water species micula murus and in bulk 18o delineate fast changes in sea surface paleotemperatures as in many other sites an end maastrichtian greenhouse warming is highlighted followed by a short cooling and an additional warm pulse in the last 30 kyr of the maastrichtian which has rarely been documented so far orbital tuning of the delineated climatic events is proposed following the two different age models calcareous nannofossil assemblages highlight a decrease in surface water nutriency but their species richness remains high through the latest maastrichtian indicating in tunisia a weak impact of deccan volcanism on calcareous nannoplankton diversity before the mass extinction

ostracode turnover and sea level changes associated with the paleocene eocene thermal maximum the ostracode response to oceanographic changes during the paleocene eocene thermal maximum petm ca 55 ma is largely unknown the gebel duwi section egypt provides a detailed ostracode record across the petm in a middle neritic setting quantitative analysis of this record reveals two significant results 1 the petm is marked by a sharp faunal turnover as indicated by abundance changes local extinctions and immigrations this turnover punctuated a gradual basin wide faunal transition 2 during the 60 k y period prior to the petm relative sea level fell rapidly by 15 m this sea level fall was followed by an 20 m sea level rise during the petm a possible eustatic control on these fluctuations suggests the presence of a cryosphere and variations in its size during this time of global warmth

extended cretaceous tertiary boundary extinctions and delayed population change in planktonic foraminifera from brazos river texas high resolution planktonic foraminiferal analysis of three brazos river sections indicates a nearly continuous cretaceous tertiary k t boundary sedimentary record second only to the world s most complete record at el kef tunisia species extinctions occur over an extended period of time and with two major extinction episodes the first extinction episode with 46 of the species extinct occurs at and just below 10 15 cm a short hiatus at the base of a sandy shell hash and clay sand unit which was interpreted by bourgeois et al 1988 to represent a tsunami bed generated by the k t boundary bolide impact the top of this tsunami bed is about 17 20 cm below the k t boundary as defined by the first appearance of tertiary planktonic foraminifera the second extinction phase with 45 of the species extinct occurs 25 cm above the k t boundary zone p0 p1a boundary of the remaining seven surviving cretaceous species six gradually disappear during planktonic foraminiferal subzones p1a and basal p1b no species extinctions or major faunal assemblage changes are directly associated with the k t boundary iridium distribution is ambiguous with one peak in the upper part of the tsunami bed and a second peak at the micropaleontologically defined k t boundary relative abundances of dominant species are stable through the late maastrichtian and only minor abundance changes coincide with the first extinction episode or the k t boundary the first major faunal change in the dominant species group coincides with the second extinction episode and leads to decline and eventual extinction of this group in subzone p1a species disappearing at the two extinction episodes 46 and 45 constitute only a small percentage 8 and 5 of the individuals of the total planktonic foraminiferal population this suggests that weakened species with low numbers of individuals and sensitive to relatively minor environmental changes were primarily affected by these extinction episodes magnetostratigraphy indicates that the first extinction phase began about 310 000 years before the k t boundary and the second extinction phase occurred 50 000 years after the k t boundary this stepped pattern of species extinctions suggests a progressively stressed ecosystem in continental shelf settings which may be related to an observed sea level regression and global cooling the hypothesis of a global catastrophic mass extinction at the k t boundary caused by a large extraterrestrial impact is not supported by the brazos river planktonic foraminiferal data

cenozoic palaeogeographic development of northern tunisia with special reference to the stratigraphic record in the miocene trough abstract cenozoic deposits are present in five northeast trending provinces of northern tunisia from northwest to southeast the numidian belt the western brjaoua and eastern bou sefra parts of the miocene trough the fortuna basin and the eastern platform the critical bou sefra sequence is an essentially complete fossiliferous miocene succession these cenozoic deposits record six episodes 1 widespread paleocene and eocene tethyan transgression flooded the entire region 2 during oligocene time the inner part of the northwestern cratonic margin was uplifted and eroded while a pelagic facies filled a northeast trending precursor of the fortuna basin at the same time a shallow marine facies prevailed to the east south and west 3 increased early miocene deformation in the fortuna basin area led to accumulation of thick conglomeratic deltaic to alluvial sandstone which graded laterally into shallow marine deposits on the eastern platform neritic sediments also accumulated along much of the miocene trough to the west and later spread eastward over the fortuna formation farther northwest a thick succession of sandy numidian turbidites was deposited along the outer continental margin of north africa 4 in middle miocene time numidian nappes were emplaced in the northwest while deformation and local uplift within the miocene trough was accompanied first by marine marl and mud and then by accumulation of a muddy flyschoid facies that graded into neritic to paralic deposits farther east 5 during late miocene time uplift and erosion prevailed in the far northwest while a shallow marine facies in the miocene trough was succeeded by evaporite bearing neritic to paralic deposits before the end of the miocene epoch neritic to paralic facies dominated the eastern part of the fortuna basin area and the eastern platform throughout this episode 6 intense deformation at the end of miocene time produced uplifts in the northwest and along the tunisian atlas flanked by coarse grained nonmarine pliocene deposits as well as local subsidence and marine basin fill in the bizerte area in the northeast and on cap bon peninsula to the east

benthic foraminiferal ecomarker species of the terminal cretaceous late maastrichtian deep sea tethys abstract benthic foraminiferal distribution patterns throughout the late maastrichtian tethyan deep sea are analyzed many species are ubiquitously distributed throughout this region and therefore it is hard to assess their ecological preferences however five species show distribution patterns which suggest that they may have distinctive paleoenvironmental preferences these preferences are interpreted from hypothesized surface circulation and upwelling patterns additional information comes from recent benthic foraminiferal ecology and from responses to the cretaceous paleogene k pg boundary event this enables us to assess the ecological preferences of these late maastrichtian taxa and establish them as ecological marker ecomarker species for paleoenvironmental interpretation of the late maastrichtian bathyal abyssal tethyan realm 1 eouvigerina subsculptura is suggested to be indicative of reasonably oxygenated upper middle bathyal environments though with high abundance of utilizable organic matter 2 sliteria varsoviensis is linked to areas of late maastrichtian upwelling and seems to have been an epibenthic species with an opportunistic life mode 3 gavelinella beccariiformis and 4 nuttallides truempyi are considered to be indicative of oligotrophic conditions unless they occur with a large proportion of endobenthic morphotypes 5 gavelinella pertusa is proposed to indicate neritic middle bathyal environments of the boreal realm which might be influenced by more seasonal food fluxes and by higher oxygen levels than similar settings in the sub tropics finally the anomalous high abundances of the buliminid species sitella cf plana in deep open ocean environments is discussed in terms of possible mechanisms permitting such a morphologically opportunistic species to thrive in such an assumedly oligotrophic environment

paleooceanography of the mesogean sea based on ostracods of the northern tunisian continental shelf between the late cretaceous and early paleogene a new method analysis used in the study of the el kef section north western tunisia led to the paleooceanographic reconstruction of the mesogean between late cretaceous and early paleogene several changes observed are in fact worthy of particular mention paleobathymetrically the area changed from an upper bathyal environment of about 400 m deep to an outer shelf domain of 100 50 m furthermore the oxygen minimum zone o m z became highly intense at a the cretaceous tertiary transition catastrophic event b the p1 p2 boundary intense thermic stratification and c between p4 and p6 very active paleoproductivity in this last episode the continental shelf environment was subjected to intense upwelling responsible for the formation of a prephosphatic environment at water sediment interface the paleooceanographic history of phosphates in the gafsa metlaoui basin is in fact in perfect stratigraphic and paleoenvironmental agreement with the paleobathymetric evolution of the kef region finally paleooceanographic communication between the mesogean and the north atlantic was at this period highly free because of lack of hydrologic relations between the north atlantic and the norwegian sea

horizontal parameters of daytime thermospheric gravity waves and e region neutral winds over puerto rico we report on the electron density perturbation amplitudes periods up to 60 min horizontal and vertical wavelengths phase speeds and propagation directions of daytime traveling ionospheric disturbances tids from 115 to 300 km altitude using dual beam experiments at the arecibo observatory ao puerto rico as in previous studies we find a near continuum of waves above the ao while the tids propagate in nearly all directions except purely westward we find that most propagate southward southeastward we find that tid amplitudes increase nearly exponentially with increasing period although with a much smaller slope for periods 30 min tid amplitudes peak on the bottomside of the f region typical vertical wavelengths increase from less than 50 km at low altitudes to 100 300 km horizontal wavelengths increase from 70 100 km to 150 500 km over the same altitude range median vertical wavelengths horizontal wavelengths and periods increase with altitude up to z 100 150 m s we also measure the e region horizontal neutral winds and find that they peak at 150 m s near z 105 km in the middle of the day wave phase speeds are in general greater than these ambient winds in addition by tracing individual wave packets vertically in altitude we find that a packet s vertical wavelength generally peaks near the altitude where its inferred ion velocity amplitude is maximum the vertical wavelength generally decreases above this altitude an observation that is consistent with gravity wave packet theory

a benthic foraminiferal record of paleocene sea level and trophic redox conditions at gebel aweina egypt we quantitatively analyzed benthic foraminiferal assemblages in order to reveal biotic and paleoenvironmental trends in the paleocene section of gebel aweina egypt on the southern tethyan shelf the first correspondence axis ranks taxa along an empirically derived bathymetric gradient with neritic taxa e g discorbis duwi and haplophragmoides walteri opposed to bathyal taxa e g nuttallides truempyi and gavelinella beccari ormis the estimated paleodepth as reflected by the various assemblages was mostly 200 m but varied between 50 m p3a np4 and 300 m p4 n p8 the resultant four relative sea level cycles appear to be at least of regional extent and may in part be eustatically controlled the second correspondence axis reflects trends in trophic and redox development low food high oxygen conditions prevailed during biochrons plc p3b np4 np5 and late p4 np8 when assemblages were mostly dominated by cibicidoides spp most oligotrophic conditions coincided with maximum paleodepth intermediate trophic levels were established during middle p4 np6 and early p5 np9 from the level of the latest paleocene benthic extinction event bee middle p5 and np9 onwards until biochron p6a np10 assemblages dominated by buliminids marked increased trophic levels and reduced ventilation probably resulting from enhanced surface productivity enhanced surface productivity along the southern tethyan margin started during biochron p4 and at least on some shelves intensified after the bee increasing productivity during the latest paleocene contrasts with global trends this may be expected during climatic warming and an expanding trophic resource continuum leading to regionally intensified eutrophy and oligotrophy high productivity through upwelling along the southern tethyan provides support for gcm predictions of intense wind stress in this region during the warm late to latest paleocene 1998 elsevier science b v

the krithe problem a case history of the distribution of krithe and parakrithe crustacea ostracoda in the south china sea abstract the distribution of 12 species of krithe and 4 species of parakrithe through the depth range of 150 4000 m and 5 depth stratified water masses in the south china sea reveals that there is no correlation between size and shape of the anterior vestibulum and levels of dissolved oxygen nor between the length of specimens and water depth given this evidence from elsewhere it is recommended that the peypouquet hypothesis which argues for these relationships should be re evaluated and not used as a palaeoceanographical tool it is suggested that the relative abundance of krithe as a percentage of the total ostracod fauna may be an important factor in reconstructing palaeodepth in the south china sea despite its somewhat restricted nature and endemically low oxygen levels the krithidae are shown to be the dominant deep sea ostracoda

late cainozoic ostracod faunas and paleoenvironmental changes at odp site 1148 south china sea ostracod faunas from odp site 1148 in the south china sea have been analyzed quantitatively in order to understand paleoenvironmental changes in the late cainozoic deep water more than 2000 core samples were taken from the oligocene to quaternary section of which 725 contained ostracods and yielded at least 100 species krithe dominates the faunas throughout the oligocene quaternary sequences indicating that deep sea conditions had existed since the earliest oligocene ca 34 5 ma this suggests that the spreading of the south china sea basin predates the oligocene three distinct ostracod assemblages have been recognized and their respective faunal turnover reflects a change in paleodepth from the upper bathyal 2500 m since the late middle miocene 14 ma to the present intervals when ostracods become very rare are at 28 5 27 20 18 2 and 13 2 8 ma the earliest of these intervals was probably related to the high surface productivity and the depletion of oxygen content in bottom water while intervals were the product of enhanced carbonate dissolution measures of evolutionary activity origination extinction and diversity have been applied to detecting the environmental change and their relationship to global events five peaks of evolutionary activity occurred in the oligocene p18 p21a and p22 and in the earlier mid miocene n8 and late pliocene quaternary n21 n22 respectively the peaks in p18 and p21a are the possible response respectively to the global cooling events oi 1 and oi 2 which occurred in the early oligocene the marked increase in extinction origination and diversity was synchronous with the major enrichment in benthic 18o in the late pliocene n21 suggesting a reaction of the ostracod faunas to the rapid cooling of the bottom water and the initiation of the north hemispheric glaciation during the period of 3 2 5 ma

stable isotope toc and caco3 record across the cretaceous tertiary boundary at el kef tunisia we report the results of stable oxygen and carbon isotope analysis of carbonate fine fraction and benthic and planktic foraminifers caco3 and toc determinations of sediments across the cretaceous tertiary k t boundary at el kef tunisia we used grain size analysis of the fine fraction carbonate to determine possible compositional effects and smearslide and scanning electron microscope examinations to evaluate possible diagenetic alteration and microfossil preservation the data suggests the following sequence of events upper maastrichtian oxygen and carbon isotope signals indicate relatively warm temperatures a decreasing thermal gradient possibly related to a shallowing sea and relatively high surface water productivity a sharp cooling appears to begin just below the k t boundary the k t boundary is characterized by a sudden 2 negative shift in fine fraction 13c a slight 0 6 enrichment in benthic 13c and a reduction of about 40 in caco3 sedimentation these data imply strongly reduced surface water productivity as also observed in numerous deep sea sequences worldwide the lower danian planktic foraminiferal zones p0 p1a is marked by generally low productivity and unstable environmental conditions as indicated by generally low but fluctuating fine fraction 13c values and low 5 15 carbonate deposition at the base of subzone p1b caco3 benthic and fine fraction 13c values increase gradually and reach near pre k t boundary levels in subzone p1c indicating initial recovery after the k t boundary event about 300 000 400 000 years after the k t boundary the prolonged low productivity episode after the k t crisis and the pre k t boundary cooling associated with a major reduction in planktic foraminiferal diversity are difficult to explain by a single k t boundary bolide impact

quaternary ostracods as palaeoceanographic indicators a case study off southern australia abstract there is increasing use of ostracods in palaeoceanographic interpretation yet few comparisons have been made with existing foraminiferal indicators this paper examines ostracod records from two cores taken off southern australia and compares them with foraminiferal records of abundance and dissolution core e55 6 from the continental margin of victoria is located in 2346 m water depth core e27 30 located south of tasmania in a water depth of 3552 m lies to the north of the present position of the subtropical convergence while benthic foraminiferal abundances parallel ostracod abundances in core e55 6 this is not the case in core e27 30 in the latter core peaks in ostracod abundance are offset from peaks in foraminiferal abundance this is attributed to high phytodetrital input associated with the subtropical convergence an ostracod based dissolution index is compared with foraminiferal dissolution data from both cores the ostracod dissolution index shows greater sensitivity than foraminiferal fragmentation in water depths well above the lysocline and suggests that carbonate dissolution at these depths may be underestimated using foraminiferal indices the impact of dissolution on ostracods can also be seen as a reduction in abundance this is evident in both cores although the impact is greater in the shallower core suggesting that carbonate saturation may be a factor in the distribution of ostracods in the deep sea further investigation of the effects of carbonate saturation on individual ostracod taxa will enhance their utility as palaeoceanographic tools

quantitative analysis and palaeoecology of eocene ostracoda and benthonic foraminifera from gebel mokattam cairo egypt abstract a detailed study of the ostracod and benthonic foraminiferal assemblages of two sections from gebel mokattam east of cairo yielded ostracod species and benthonic foraminiferal species in 25 samples from the mokattam group of late middle eocene age and the maadi group of late middle to late eocene ages the remaining five samples representing the gebel ahmar formation of oligocene age at the top of the succession are barren of fossils cluster analysis using the jaccard coefficient of similarity the group average linkage method helped distinguish four ecozones of late middle to late eocene age principal coordinate analysis pco applied to the same data led to the distinction of two important environmental factors affecting the distribution of these ostracod assemblages in the study area turbidity currents exposure to water depth and oxygenation of water analyses of the microfacies and microfaunas indicate deposition in a well oxygenated turbid shallow marine environment except at the base of the sequence which implies reduced oxygenation despite the lack of planktonic foraminifera in the studied sections however the identified benthonic foraminiferal assemblage affirms that the age of the mokattam group is biarritzian while that of the maadi group ranges from biarritzian to priabonian the gebel ahmar formation covering the whole succession is assigned to the oligocene a reduced ostracod migration activity was detected along the shores of tethys during the middle to late eocene times

an empirical model of the earth s horizontal wind fields hwm07 1 the new horizontal wind model hwm07 provides a statistical representation of the horizontal wind fields of the earth s atmosphere from the ground to the exosphere 0 500 km it represents over 50 years of satellite rocket and ground based wind measurements via a compact fortran 90 subroutine the computer model is a function of geographic location altitude day of the year solar local time and geomagnetic activity it includes representations of the zonal mean circulation stationary planetary waves migrating tides and the seasonal modulation thereof hwm07 is composed of two components a quiet time component for the background state described in this paper and a geomagnetic storm time component dwm07 described in a companion paper

a low extinction rate of intermediate water benthic foraminifera at the cretaceous tertiary boundary the contrast between the high extinction rates of calcareous marine plankton and low extinction rates of deep water calcareous benthic foraminifera across the cretaceous tertiary k t boundary is now recognized however the water depth at which the vertical change in extinction rates of marine organisms occurred at the k t boundary is not yet known because of the lack of data on the extinction rates of intermediate water organisms the extinction rate of intermediate water benthic foraminiferal species from kawaruppu hokkaido japan was determined by distinguishing locally extinct species a distinctly low extinction rate 10 for calcareous benthic foraminiferal fauna from the upper part of the intermediate water is documented for the first time this rate is almost equal to the extinction rate of deep water benthic foraminifera 10 and is much smaller than the planktic foraminiferal extinction rate 81 the extinction rate curve for calcareous foraminifera in a vertical water column indicates that a rapid change from a high extinction rate 80 to a low extinction rate 10 took place at a water depth of about 150 m this depth of change is equivalent to the boundary depth between the surface and intermediate waters and between the euphotic and aphotic zones furthermore this coincidence is consistent with the hypothesis that acid rain and a darkness induced breakdown of the marine food chain produced by a cometary or asteroidal impact at the k t boundary were the main causes of the mass extinction of calcareous planktic organisms in surface waters

paleoenvironmental change at the danian selandian transition in tunisia foraminifera organic walled dinoflagellate cyst and calcareous nannofossil records abstract in the present study we document paleoenvironmental change across the danian selandian transition planktic foraminiferal interval p2 p3b calcareous nannofossil zone np4 subzones ntp6 ntp8a 61 59 ma in nw tunisia diversifications of paleogene planktic foraminifera with the evolution of the muricate and photosymbiotic lineages morozovella acarinina and igorina and of the biostratigraphically important nannofossils genus fasciculithus are recorded within this interval the present study aims to understand early paleogene environmental changes in the southern tethys by analyzing the evolution of surface water and to a lesser extent seafloor conditions three localities were investigated ain settara elles and el kef all representing outer neritic deposition in the same basin the tunisian trough paleoenvironmental changes are explored by combining planktic foraminiferal organic dinocyst and calcareous nannofossils assemblages and several proxy parameters planktic benthic ratio numbers of planktic foraminifera per gram peridinioid gonyaulacoid ratio terrestrial marine palynomorph ratio in addition also some geochemical parameters calcite content and stable isotopes are examined our records indicate that the environment evolved from an initially oligotrophic open marine deep outer neritic setting in p2 p3a towards a shallower and nutrient rich setting from the base of subzone p3b this change is seen in the foraminiferal assemblages with the substitution of praemurica by morozovella among the planktic foraminifera and an upward decrease in deeper benthic taxa also the organic dinocyst assemblages show a peak of peridinioid cysts cerodinium and lejeunecysta associated to these dinocyst assemblages the lowest occurrence of apectodinium is recorded which seem to have evolved in this region possibly in response to enhanced nutrient levels on the shelf additionally a distinct change in calcareous nannofossil assemblages is also described marked by the lowest appearance of chiasmolithus edentulus the lowest consistent occurrence of fasciculithus and a slight increase in near shore taxa essentially pontosphaera this project provides an accurate understanding of paleoenvironmental change across the danian selandian transition in tunisia especially integrating different proxies demonstrates a paleobathymetric shallowing from the danian to the selandian associated to increase surface paleoproductivity furthermore the results are compared with those from other localities along the southern tethyan margin egypt and jordan and a more regional paleoclimatic paleoceanographic perturbation in the southern tethys is suggested

statistical study of nighttime medium scale traveling ionospheric disturbances using midlatitude airglow images 1 we have investigated statistical characteristics of the nighttime medium scale traveling ionospheric disturbances mstids observed in 630 nm airglow images at two stations rikubetsu 43 5 n 34 8 mlat and shigaraki 34 9 n 25 4 mlat in japan for 1998 2000 near the solar maximum period most of the observed mstids propagate southwestward in the images the typical wavelength velocity period and amplitude are 100 300 km 50 100 m s 0 5 1 5 h and 5 15 respectively seasonal variations in these parameters are not clear the occurrence rate has a major peak 50 60 in summer that appears 2 months earlier at lower latitudes and a minor peak in winter similar occurrence characteristics are obtained from midlatitude spread f signatures using multipoint ionosonde data in japan though the coincidence of the spread f and the mstids in airglow images is only 10 15

pliensbachian toarcian ostracod biogeography in nw europe evidence for water mass structure evolution abstract this paper examines the role played by palaeoceanographic and climatic conditions on the palaeobiogeography of the pliensbachian toarcian ostracods early jurassic in the european epicontinental sea ees the influence of the palaeogeography ocean currents and sea level temperature and salinity variations on ostracod abundance diversity and migration patterns is reconstructed ostracod migration follows an anticlockwise circulation in the eastern side of the ees with a leading northeast southwest movement and the frequent arrival of tethyan faunas into the central and western parts of the ees during the pliensbachian a three fold classification of water masses based on salinity temperature lithological and fossil data is proposed the repeated inflow of tethyan ostracods into the ees ended by the earliest toarcian this ostracod event is related to the opening of the hispanic corridor and to the reorganization of the surface and deep circulations that may have generated a cold episode at the beginning of the toarcian

climatic fluctuations and sea surface water circulation patterns at the end of the cretaceous era calcareous nannofossil evidence abstract new paleoecological data are presented for late maastrichtian calcareous nannofossil assemblages of the indian ocean and the boreal epicontinental chalk sea these data are compiled with recent results in the tropical atlantic pacific and tethys oceans in order to characterize environmental changes by the end of the cretaceous era the paleobiogeographic distribution of the warm water species micula murus is updated and indicates the existence of major sea surface currents in the late maastrichtian atlantic ocean similar to the present day the end maastrichtian greenhouse warming is characterized at tropical and subtropical latitudes by an increase in abundance of m murus and the temporary disappearance of the high fertility marker biscutum constans in the boreal realm the greenhouse episode is marked by a contemporaneous acme of watznaueria barnesiae coincident with very rare occurrences of m murus and other tropical nannofossil species which have never been reported before at boreal latitudes a review of cyclostratigraphic and calcareous nannofossil data in the atlantic pacific indian and tethys oceans points to the following evolution of sea surface paleotemperatures for the last ca 350 380 kyr of the cretaceous the end maastrichtian greenhouse warming lasted on average a little more than 200 kyr and was followed by a ca 100 120 kyr cooling in the tethys a 30 40 kyr additional pulse of warming is highlighted immediately below the cretaceous paleogene boundary these findings indicate an important instability of the climate system at the end of the maastrichtian most likely caused by deccan volcanism the calcareous nannofossil species richness dropped during the end maastrichtian greenhouse warming which may indicate environmental stress and or ocean acidification however nannoplankton diversity returned rapidly to higher values after this climatic episode and remained high up to the cretaceous paleogene boundary no significant extinction is recorded in this biotic group prior to the boundary clay

observations of traveling ionospheric disturbances with a satellite beacon radio interferometer seasonal and local time behavior we have operated a very long baseline interferometer array at a northern midlatitude site illuminated by vhf radio beacons from two geosynchronous satellites quasi continuously for over a year the array can detect and measure the trace velocity of traveling ionospheric disturbances tids via their signatures in the line of sight total electron content tec the system noise level is of the order of 1013 m 2 in the tec so that even very weak perturbations can be studied we have used the year long tid detection velocimetry data set to describe local time and seasonal dependences of the wave parameters the most striking finding is that the preferred azimuths of tids in the data set tend to belong to either of two modes the first mode strongest at midday and in the early afternoon particularly around winter equinox propagates southward the second mode strongest in the evening especially during summer solstice through autumn equinox propagates west northwestward the two modes are disposed in local time such as to suggest the agency of clockwise rotation of the tid preferred azimuths versus time as expected by wind filtering in the thermospheric diurnal tide however there is a gap between the two modes azimuth bands moreover the two modes exist in all trace speed quartiles of the data set tids a finding which is at variance with the hypothesis of wind filtering being the primary explanation of these modes

palaeoenvironmental analysis of mid cretaceous coastal lagoonal deposits lusitanian basin w portugal abstract the sedimentary record of fossil coastal lagoons is an under explored archive of environmental change in ancient coastal domains the significant continentality of coastal lagoons the small volumes of their water bodies very shallow depths and intermittent connectivity to oceanic aquafacies all result in a highly complex depositional system the matrix micrite chemostratigraphy carbon and oxygen isotope ratios of two mid cenomanian shallow coastal lagoon sections in the western lusitanian basin portugal are here presented in comparison to the geochemistry of different diagenetic carbonate materials geochemical evidence is placed against independent data from field observations sedimentology microfacies analysis and ostracod palaeoecology marine ingressions and coastal lagoonal environments are recorded both in sedimentological micropalaeontological and geochemical data sets intervals of more open marine conditions are evidenced by overall higher 0 to 2 carbon and less 18o depleted 3 isotope ratios the opposing pattern is observed for periods of more restricted lagoonal conditions the combination of a detailed ostracod palaeoecology with geochemical and sedimentological findings is considered a strength of this paper as it allowed to disentangle the complex geochemical signals of ancient coastal lagoonal deposits the comparison with recent coastal lagoons provided new arguments to clarify interpretations based on ancient records

estimating greater paleodepths with ostracodes especially in past thermospheric oceans abstract modern ostracodes show significant morphologic and taxonomic changes with increasing depth deep psychrospheric faunas are less diverse and more cosmopolitan than shallow faunas individuals are larger rarer and blind their carapaces seem better designed relative to the mass of construction material used speciation is slower taxa are older longer ranging and for the most part now confined to abyssal and bathyal environments deep thermospheric ostracodes found in pre psychrospheric oceans or isolated basins are different their deep origin seems related to the ability of shelf species to submerge past what is a formidable thermal barrier to test morphologic changes that reflect faunal submergence in thermospheric oceans such as existed in the atlantic before about 40 m y b p the basis for an adaptive structural theory is explored this leads to a search for limits expressive of rapid change both in the structure of morphology and in water mass structure examination of the ostracodes from core samples of cretaceous age from nine d s d p sites in the south atlantic suggests that the rio grande rise walvis ridge aseismic system has both been a water mass barrier and yet remained deep at least mid bathyal over the last 100 m y no evidence of either shallow ostracodes from the shelves of africa south america or those of islands were found indicating that models proposed previously that there would have been an archipelago or shallow submerged causeway across the rio grande rise walvis ridge during the late cretaceous are probably in error

perturbation of a tethyan coastal environment during the paleocene eocene thermal maximum in tunisia sidi nasseur and wadi mezaz abstract despite the large number of studies on the paleocene eocene thermal maximum petm the knowledge of environmental and biotic responses in shallow marine environments remains quite poor benthic foraminiferal assemblages of the sidi nasseur and wadi mezaz sections in tunisia were studied quantitatively and the paleoecologic interpretations provide new insights into the complex relationship between petm global warming and perturbations of shallow marine settings these sections expose upper paleocene to lower eocene shales and marls of the el haria formation up to the phosphate layers of the chouabine formation underlying the el garia limestones the sidi nasseur section contains a more complete and expanded paleocene eocene boundary interval compared to wadi mezaz although being truncated at the top the wadi mezaz section contains a more complete post petm interval the studied interval can be subdivided into a sequence of 4 biofacies representing respectively a latest paleocene biofacies two petm biofacies and one post petm eocene biofacies the latest paleocene biofacies 1 consists of numerous calcareous benthic foraminifera e g anomalinoides midwayensis frondicularia aff phosphatica and various bulimina and lenticulina species abundant non calcareous taxa haplophragmoides and rare planktic foraminifera indicating a slightly hypersaline eutrophic inner neritic to coastal environment regularly interrupted by oxygen deficiency moderate dysoxia during the latest paleocene this highly productive environment shallowed as indicated by the increasing abundances of a midwayensis the variable dominance of non calcareous agglutinated taxa in biofacies 1 indicates post mortem dissolution effects the toc 13 c org record reveals a sharp negative excursion marking the base of the eocene in general the absence of lithologic changes an increasing sedimentation rate and absence of reworking indicate that the initial part of the petm is complete and expanded in the sidi nasseur section a sharp faunal turnover coincides with this negative 13 c org excursion and is characterized by the disappearance or diminution of common paleocene taxa in this area during the petm benthic foraminifera are less abundant and consist of opportunistic non calcareous taxa together with deeper dwelling middle neritic lagenids and buliminids biofacies 2 and 3 planktic foraminifera dominated by flat spired acarinina mainly a multicamerata become more abundant as observed in many open marine sequences worldwide all these faunal parameters suggest more stressed probably severe dysoxic sea floor conditions within a transgressive phase during the onset of the petm an estimation of the total duration of the sidi nasseur petm interval is difficult to establish yet the lack of recovery carbon isotope values suggests that the preserved petm interval reflects only a part of the cie core the top of the petm interval is truncated due to local erosion during the early eocene the eocene recovery fauna is mainly composed of lenticulina and stainforthia species biofacies 4 indicating restricted coastal to hyposaline lagoonal eutrophic conditions distinctly different from earlier environmental conditions

palaeoecology and palaeobiogeography of the middle jurassic ostracods of southern tunisia abstract the results of a palaeoecological biostratigraphical and palaeobiogeographical analysis of jurassic ostracods from southern tunisia are presented the shallow to marginal marine deposits of bajocian bathonian krachoua and techout formations and callovian oxfordian age tataouine formation which accumulated under predominantly warm humid climatic conditions yielded diverse ostracod faunas from limnic brackish and marine environments which have been analysed statistically a qualitative cluster analysis yielded fourteen associations and two assemblages which are characterised by different percentages of marine brackish and freshwater species the distribution of the associations in the middle jurassic reflects temporal and spatial salinity gradients which are interpreted to reflect climatic variations humid arid and global eustatic sea level changes in the callovian the ostracods and macrofaunas probably also reflect minor relative sea level changes in accordance with other biostratigraphical data the ostracods support a bajocian bathonian age for the upper krachoua and the lower techout formations and a callovian age for the lower tataouine formation the palaeobiogeographical relationships suggest faunal exchange between southern tunisia and europe southern france sardinia england in the bajocian bathonian and an isolation of the south tunisian ostracod faunas from the european faunas in the callovian probably due to the deepening of the central western tethys predominantly in the bajocian bathonian but also in the callovian brackish conditions resulted in an endemicity of the ostracod faunas as a consequence of the eustatic sea level rise in the callovian species from the eastern north gondwana shelf israel jordan egypt saudi arabia respectively the ethiopian province invaded southern tunisia palaeobiogeographically the ostracods from southern tunisia are intermediate between the ostracods from the arabic northeast african region and northwest africa morocco

a terrestrial scenario for the cretaceous tertiary boundary collapse of the marine pelagic ecosystem in this paper we present an expansion of the model for marine ecosystem collapse at the cretaceous tertiary boundary presented by brinkhuis and zachariasse 1988 a long term sea level drop at the end of the cretaceous culminated in a short term regressive pulse at k t time deep water production was curtailed minimizing the vertical advection of nutrients and oxygen in the oceans consequently a productivity crisis developed which could only be survived by cosmopolitan shallow dwellers and the oxygen minimum zone omz expanded no sustained oceanic anoxic event followed the k t boundary event since productivity had dropped to extremely low values at k t time however the short term expansion of the omz invoked by the combination of minimized oxygen advection and abrupt mass mortality caused dysoxic conditions even to reach up to the shelves as can be deduced from sedimentological chemical and faunistic observations

acoustic tomography high resolution measurements of the density field in the ocean are prohibitively expensive if traditional ship borne instruments are used tomography uses acoustic remote sensing to infer ocean structure and avoids many of the limitations of direct measurements sound pulses follow distinct trajectories through the water from source to receiver and the travel time for a given pulse is a known functional of the sound speed field this functional can be inverted to recover an estimate of the sound speed field through which it passed the inversion is accomplished with either detenninistic linear matrix inversion or stochastic optimal estimation and the sound speed field estimate returned can be converted to an estimate of density a numerical simulation of the pilot tomography experiment is presented to demonstrate that tomography can be effective in reproducing significant ocean features

trace elements stable isotopes and clay mineralogy of the elles ii k t boundary section in tunisia indications for sea level fluctuations and primary productivity abstract trace elements and stable isotopes in bulk rocks and foraminifera bulk rock and clay mineral compositions are used as palaeoproxies to evaluate sea level fluctuations climatic changes and variations in primary productivity across the k t transition at elles ii in tunisia from 1 m 33 kyr below to 1 m 70 kyr above the k t boundary results on clay minerals major and trace elements stable isotopes in bulk rock samples e g ca cu zn rb sr zr ba 13c and 18o and in foraminifera sr ca 13c 18o indicate that the latest maastrichtian last 33 kyr in tunisia was marked by a relatively warm but humid climate and a rising sea level the transgressive surface is marked by deposition of a foraminiferal packstone just below the k t boundary followed by maximum flooding across the k t boundary red layer and black clay layer humid warm conditions accompanied the maximum flooding along with increased total organic carbon values and rapidly decreasing primary productivity at the k t boundary an impact event ir anomaly ni rich spinels spherules exacerbated already stressed environmental conditions leading to the mass extinction of tropical planktic foraminifera increasingly more humid conditions prevailed within the lowermost danian zone p0 50 kyr culminating in a sea level lowstand near the top of p0 a slow recovery of the ecosystem in zone p1a coincided with a rising sea level and gradually less humid climatic conditions

the cretaceous tertiary transition in guatemala limestone breccia deposits from the south peten basin limestone breccia deposits in southern mexico guatemala and belize have recently been interpreted as proximal to distal ballistic fallout deposits generated by a bolide impact that struck yucatan at k t boundary time we review the age lithology and the depositional environment of five k t boundary sections in the south peten area of guatemala caribe aserradero chisec actela chemal in order to evaluate the nature and origin of k t limestone breccia deposition the sections are located 500 km south of the proposed impact site at chicxulub and trend in an east west direction from the guatemala mexico border to southern belize in four of the five sections examined a breccia unit up to 50 m thick overlies reef bearing shallow water limestones of late cretaceous campanian maastrichtian age rhythmically bedded limestones marls and siltstones of early danian age overlie the breccia and were deposited under middle to outer neritic conditions the breccia consists of differently coloured layers of shallow water limestones clast size generally decreases upsection to thin layers of predominantly rounded clasts and these fine grained rudstones grade into grainstones at the top in at least one section ei caribe diagenetically altered glass spherules are present in the uppermost layers of the grainstone these glass spherules are of stratigraphic position and chemical composition similar to black and yellow glass from beloc haiti and mimbral mexico which some workers have chemically linked to melt glass within the breccia of the chicxulub cores we suggest that breccia deposition in guatemala may have been multi event over an extended time period and related to the collision of the yucatan and chortis plates as well as related to a major impact or volcanic event at the end of the cretaceous

in search of the latest danian event in a paleobathymetric transect off kasserine island north central tunisia danian lower paleocene sequences in north central tunisia are dominantly composed of marls and shales but a conspicuous indurated glauconite bearing marker bed is associated with the p3a p3b transition this glauconite bed is considered to correlate with the latest danian event lde described from the nile basin in egypt with the top chron c27n event atlantic and pacific oceans and with the cie ds1 zumaia spain the lde is thought to reflect a short period of global warming similar to the paleocene eocene thermal maximum but of lesser magnitude the presence of a glauconitic bed at the p3a p3b transition in tunisia suggests that the sequence is condensed which is confirmed by planktic foraminifer and nannofossil biostratigraphy and by the absence of the typical lde beds found in most egyptian sections benthic foraminiferal assemblages were quantitatively analyzed in three sections in north central tunisia sidi nasseur garn halfaya elles in order to characterize the paleoenvironmental evolution during the late danian and compare this with sections in egypt the benthic foraminiferal assemblages indicate that the tunisian sections were located along a depth and a paleoenvironmental gradient on the shelf north of kasserine island the reconstructed depth range is comparable with sections in egypt and encompasses middle neritic sidi nasseur section to shallow upper bathyal depths elles section with up to 16 gavelinella beccariiformis below the p3a p3b like in egypt assemblage shifts across the p3a p3b subzonal transition indicate shallowing and a transition to a more eutrophic paleoenvironment characterized by relatively high abundances of buliminids and stainforthia sp the 13c and 18o records generated on well preserved specimens of the ostracode species bairdia failed to demonstrate the presence of the carbon isotope excursion cie associated with the lde at the base of subzone p3b a condensed section or a hiatus associated with the glauconite bed would explain why the cie is not recorded in the tunisian sections

a demonstration of ocean acoustic tomography over the past decade oceanographers have become increasingly aware of an intense and compact ocean mesoscale eddy structure the ocean weather that is superimposed on a generally sluggish large scale circulation the ocean climate traditional ship based observing systems are not adequate for monitoring the ocean at mesoscale resolution a 1981 experiment mapped the waters within a 300 300 km square south west of bermuda using a peripheral array of moored midwater acoustic sources and receivers the variable acoustic travel times between all source receiver pairs were used to construct the three dimensional time variable eddy fields using inverse theory preliminary results from inversions are consistent with the shipborne and airborne surveys

tidal effects on long range sound transmission time series of acoustic travel times over long distances have significant tidal components we discuss three experiments first for a 900 km westward transmission from a moored source southwest of bermuda the m2 constituent apart from mooring motion of 8 ms can be accounted for by a variable propagation with and against the 2 cm s barotropic tidal current the situation is different for the k1 and s2 constituents which have a significant solar component particularly for rays with shallow turning points suggesting an effect from a minute daily variation in the temperature of the upper 100 m second for a 500 km transmission from the bahamas northward and parallel to the continental margin the measured m2 constituent is not in phase with the computed effect of the barotropic tidal current unlike the westward transmission mentioned above here the mode conversion from barotropic to baroclinic tides plays a crucial role the principal cause of the travel time oscillations in quadrature with the tidal current is a vertical oscillation by several meters and attendant temperature and sound speed fluctuations associated with the baroclinic tide just seaward of the continental margin in the near zone of mode conversion third for 300 km transmissions from a moored source northwest of bermuda to both a moored receiver and a landbased receiver the tidal components in the travel time are dominated by tidally induced mooring motions the tidal amplitude varies in time as the tidal mooring motion is modulated by the variable current because of the nonlinear drag and the current can be so estimated an important part possibly a predominant part of the nontidal travel time variation of 0 7 s is evidently associated with the mean mooring motion the interpretation of the tidal fluctuations in travel time is varied and complex

benthic foraminiferal assemblages between two major extinction events the paleocene el kef section tunisia abstract the development of benthic foraminiferal assemblages from the paleocene outcrops of the el haria formation near el kef tunisia is discussed qualitatively and quantitatively the aim of the study is to reconstruct the paleoenvironmental evolution between the k pg boundary interval and the late paleocene event and to compare this evolution with results from other sites along the southern tethyan margin eighty four samples covering virtually the entire paleocene provide a dataset that allows detailed qualitative and multivariate analysis the benthic foraminiferal faunas indicate a complex pattern of environmental changes during the paleocene marked by the succession of different benthic associations following the k pg boundary event community restoration was characterized by the gradual build up of faunal diversity decreasing dominance and the entry of taxa common to normal marine outer neritic to upper bathyal environments indicate the completion of the ecosystem restoration in zone plb a highly diverse benthic foraminiferal assemblage persisted throughout the remainder of the early paleocene into the earliest late paleocene at the p3a p3b zonal transition relative sea level lowering is evidenced by the sudden disappearance or decreasing abundance of deeper water taxa e g anomalinoides affinis a susanaensis gavelinella beccariiformis neritic deposition continued into zone p4 when trophic levels at the seafloor increased as indicated by the entry and increasing dominance of species such as anomalinoides cf aegyptiacus bulimina midwayensis and b strobila which we consider to be sensitive to eutrophication the combined effect of shallowing and the subsequent eutrophication led to the establishment of assemblages similar to late paleocene benthic foraminiferal assemblages from egyptian sections some of which record the latest paleocene extinction event these assemblages were interpreted to be indicative of a middle neritic highly eutrophic environment enhanced vertical fluxes of organic matter along the southern tethyan margin may have resulted from intensified upwelling this eventually led to oxygen deficiency at the seafloor it appears that oxygen deficient high productivity shelves were a common feature of the southern tethyan margin during the latest paleocene

patterns of variability in ostracode species and communities from the late cretaceous carbonate platforms a report for ecozonal modelling and the study of ambient conditions abstract previous palaeoecological and sedimentological analyses have demonstrated the marked variability of ostracode faunas in late cretaceous environments such organisms are generally strongly related to their biotopes but deeply affected by fluctuations even slight of ambient conditions therefore variations of both taxonomic units and communities may be used for a better knowledge and characterization of the main carbonate platform domains an interesting method of investigation is provided by the study of anatomical and or morphological variations within well defined taxonomic units especially ornate species living in the more internal zones of platforms they reflect with accuracy and reliability the impact of both ecological parameters and palaeogeographic settings this is also the case for some genera and even families ostracode type assemblages have been recently erected in the tethyan upper cretaceous microfaunas develop characteristic features such as richness diversity morphological trends according to their position on the carbonate platform system and sedimentary facies patterns furthermore without any consideration of the stratigraphical position of carbonate formations certain morphological variations concerning analogous taxa may be used for palaeogeographical interpretations trophic structures of ostracode communities versus nutrient flux are identifiable major changes occur through the sequences in the abundance specific composition and quantitative ratio between two main sedimentological formations carbonates especially rudist limestones and calcareous marls with benthic foraminifers and proximal terrigenous siliciclastic argillaceous areas finally this paper may be also considered as a useful attempt to synthesize present knowledge of late cretaceous carbonate platform ostracodes particularly intended for non ostracodologists who are perhaps unaware of the potential contribution of these organisms for palaeoenvironmental reconstructions

multipath variability due to the gulf stream a phase coded signal with 64 ms resolution was transmitted at 10 min intervals for a 19 day period over two 300 km ranges the acoustic source was moored at 2000 m depth northwest of bermuda one receiver was moored at 2000 m depth to the northeast of the source and the other receiver was bottom mounted at 1000 m depth near bermuda the large 0 6 s travel time change at the bermuda receiver is probably due in large part to motion of the source mooring in the presence of currents the multipath arrival pattern at the moored receiver undergoes significant modification due to the presence of a southern meander of the gulf stream which intersects this transmission path

relation of internal gravity wave anisotropy with neutral wind characteristics in the upper atmosphere this paper studies the interaction of internal gravity waves igw with neutral wind using the statistics of traveling ionospheric disturbances tid from the radio physical complex of the institute of solar terrestrial physics the complex includes the irkutsk incoherent scatter radar iisr irkutsk ionosonde dps 4 and ekaterinburg hf radar ekb the aim of this study is to give a common explanation for the tid azimuth distributions obtained with the iisr ionosonde and hf coherent radar and show that the measurements of 3 d tid characteristics put into the hands of researchers an important tool to study neutral wind in the thermosphere the distinctive features of this study are the following 1 using different tid statistics from independent tools and correspondingly independent methods for determining tid characteristics 2 using the 3 d tid characteristics for testing the wind filtering hypothesis which allows us to separate the igw induced tids from tids of other nature and identify three tid types depending on their elevation angles 3 using the local time azimuth distribution of the tid number for testing the wind filtering hypothesis this study allowed us to conclude that the observed igw azimuth anisotropy can be mainly explained by the wind filtration mechanism with considering winds at 90 250 km heights using the 3 d igw characteristics allow us estimating neutral wind parameters proposed methods are applicable for any tools which can obtain tid 3 d characteristics using the proposed methods will enable to organize a worldwide campaign to improve the existing neutral wind models

stable isotope evidence for gradual environmental changes and species survivorship across the cretaceous tertiary boundary high resolution 13c and 18o records have been generated from analyses of the planktonic foraminiferal species heterohelix globulosa and the benthonic foraminiferal taxon lenticulina spp from 3 m of a cored section spanning the cretaceous tertiary k t boundary at brazos river texas these are the first stable isotope records across the k t boundary based on monospecific and monogeneric foraminiferal samples they show a gradual decrease in 13c values of about 2 5 permil beginning at the k t boundary as defined by the first appearance of tertiary planktonic foraminifera and continuing 17 20 cm above the boundary approximately 40 000 years later gradual 13c depletion contrasts with the sudden 13c drop at the k t boundary observed in many deep sea sections the surface to bottom 13c gradient decreased to less than zero approximately 25 000 30 000 years after the k t boundary and remained negative for at least the next 140 000 years concomitant with change in 13c values is a gradual decrease of about 2 5 permil in 18c values which has not been observed at other localities this 18o depletion suggests changes in temperature and or salinity in the earliest paleocene gulf of mexico no extinction of foraminiferal species is associated with the k t boundary or the onset of 18o and 13c depletions instead two phases of cretaceous species extinctions occur one extinction phase is below the k t boundary and below the tsunami bed of bourgeois et al 1988 and may be linked to sea level regression and environmental perturbations the second extinction phase coincides with the minimum in 13c and 18o values in the early danian zone p0 pla and appears directly related to environmental changes reflected in the isotopic record h globulosa which is commonly present in maastrichtian and danian sediments exhibits significantly lower 18o 16o and 13c 12c ratios in tertiary sediments relative to specimens from maastrichtian sediments demonstrating the survival of this important cretaceous taxon after the k t boundary event

marine ostracode provincialism in the late cretaceous of the tethyan realm and the austral province abstract a synthetic analysis based on previous and new data allows the recognition of four main palaeobiogeographic units palaeobioprovinces for the late cretaceous of the tethyan realm and austral province of the south temperate realm south european north central american afro arabian and austral bioprovinces another unit the dinaro hellenic subprovince is located between the south european and the afro arabian bioprovinces special emphasis is given to the spatial and temporal distribution of ostracode assemblages at the specific level and selected key genera within several geographic zones from the tethys north central america southern europe northern africa and the middle east to eastern africa india south africa and australia several factors are responsible for these palaeobiogeographic distributions provincialism and their evolution the position and extension of continental margins oceanic surface current patterns paleobathymetry eustatic sea level changes paleolatitudes and their influence on paleoclimates other parameters are the biology physiology and ecology of the ostracodes therefore ostracode provincialism has a high potential for further paleogeographic inferences such as global tectonic reconstructions

palaeogeography of africa during the cretaceous period abstract a first attempt is made to synchronize the major palaeogeographical events of the african cretaceous where recognizable palaeoclimatological interpretations are given an overview of the nature of the continental margins and the plate tectonic setting for africa during the cretaceous provides a convenient backdrop for presenting the palaeogeographical development of the continent lacustrine deposits occur along the line of south atlantic rifting late jurassic oceanic crust in the south atlantic dates from the valanginian with continental volcanism adjacent to the walvis ridge continuing until the albian locally there was a barremian incursion in southeast africa the falkland plateau and walvis ridge areas created shallow water barriers in the aptian which facilitated the massive accumulation of salt tectono eustatic transgressions took place in the middle to late albian cenomano turonian late turonian to coniacian and campano maastrichtian anoxic conditions prevailed during the late jurassic agulhas bank falkland plateau aptian albian the cenomanian turonian and the coniacian these are relatable to the epicontinental transgressional maxima and the heavy influx of organic debris however there was no campano maastrichtian anoxic event

the impact of paleocene eocene boundary events on middle neritic benthic foraminiferal assemblages from egypt abstract a 25 m upper paleocene to lower eocene marly sequence exposed at gebel duwi quseir red sea coast of egypt provides a good opportunity for studying paleocene eocene p e boundary stratigraphy and events various bio eco and isotope stratigraphic correlations accurately delineate the position of the p e boundary i e the level of stable isotopic excursions and deep sea benthic extinctions in the middle part of this section within zones p5 and np9 in this paper the impact of p e boundary environmental perturbations on benthic foraminiferal communities of the shallow tethyan shelf is examined benthic foraminiferal assemblages from gebel duwi characterized by large frondicularia phosphatica and f nakkadyi in addition to a number of other neritic taxa but without any typical outer neritic bathyal taxa suggest middle neritic 75 100 m deposition throughout the studied interval and only minor relative sea level variations perhaps some 10 20 m across the boundary sea level appears to have been stable yet a distinct faunal turnover marks the p e boundary of this shallow site which in contrast to deep sea records is less abrupt being preceded by a gradual diversity decrease starting some four meters below the boundary moreover most exits are either local or just temporary and thus not true extinctions many lazarus taxa reappear at some point above the boundary while all but one of the disappearing taxa are known from other lower eocene neritic deposits in egypt in general benthic foraminiferal assemblages display low diversities and high dominance values notably anomalinoides aegyptiacus up to 74 suggesting high levels of environmental stress at the sea floor in combination with occasionally very high p b ratio s up to 98 p and generally laminated sediments the character of the benthic assemblage points to a strong influence of recurrent dysoxia and or anoxia we suggest that these resulted from surface eutrophication by intermittent coastal upwelling and reduced ventilation of the bottom environment although these conditions prevailed during most of the time interval studied they were most severe during the latest paleocene and early eocene when eutrophication intensified and the organic carbon flux to the sea floor increased enhanced atmospheric contrasts between the tethys seaway and the african continent resulting in intensified longshore tradewinds may have controlled these changes at the p e boundary the bottom environment became minimally ventilated perhaps due to reduced oxygen advection from deeper waters three meters above the boundary a succession of increasingly diverse assemblages indicate a gradual decrease of environmental stress and a return to more normal conditions although the organic carbon flux to the sea floor remained high

extinction survivorship and evolution of planktic foraminifera across the cretaceous tertiary boundary at el kef tunisia an expanded sediment record at el kef shows that the k t boundary extinctions of planktic foraminifera extend over an interval from 25 cm below the geochemical boundary ir anomaly to 7 cm above species extinctions appear sequential with complex large ornate forms disappearing first and smaller less ornate forms surviving longer the 14 species extinctions below the boundary appear unrelated to an impact event cretaceous species survivorship is greater than previously assumed about 10 species survive 22 into subzone p1a globigerina eugubina all cretaceous survivors are small primitive forms which are generally smaller than their ancestors in cretaceous sediments species evolution after the k t event occurs in two pulses the first new paleocene species evolve in the basal black clay zone po immediately after the major cretaceous extinctions evolving species are small and primitive similar to cretaceous survivors the second pulse in species evolution occurs in the lower part of subzone p1b with the appearance of larger more diverse species the first major increase in carbonate sedimentation and productivity occurs at this time and signals the recoveyr of the ecosystem nearly 300 000 years after the k t event the species extinctions prior to the generally assumed impact event implied by the ir anomaly and the long recovery period of the ecosystem thereafter cannot be explained by a single impact but suggest that multiple causes may be responsible such as climatic changes volcanism a sea level drop production of warm saline bottom water and the chemical consequences associated with increased salinity

integrated depositional model for the cenomanian turonian organic rich strata in north africa abstract during the late cenomanian early turonian c t oceanic anoxic event oae2 organic rich strata was deposited in rift shelf basins and slopes across north africa and in deep sea basins of the adjacent oceans based on a review of published and unpublished information this paper documents the distribution and organic richness of c t strata across the whole region within a palaeogeographic framework and systematically analyses the conditions and processes which controlled their deposition previously the c t in north africa has been most intensively studied in southern morocco tarfaya and tunisia only little data is availabe for other parts of north africa namely algeria libya and egypt because distribution of c t corg strata there becomes more patchy a general decrease in peak organic richness and black shale thickness occurs from west to east partly as a result of upwelling along the moroccan atlantic coast and the absence of upwelling in the eastern mediterranean area furthermore in the confined central atlantic the oxygen minimum zone omz in many places reached down to the deep sea floor 3 4 km while the lower limit of the omz along the north african tethys was much shallower and underlain by oxic water masses as documented by high resolution biostratigraphic and chemostratigraphic data c t black shale deposition in most areas outside the upwelling zone are restricted to a strong eustatic latest cenomanian transgressive phase triggered by this sea level rise the omz impinged onto the north african continental shelf and the margins of intrashelf basins which mostly formed during the early cretaceous as halfgrabens important units containing c t organic rich strata in the region are the atlantic tarfaya black shales morocco western sahara black shales and phtanites in the moroccan and algerian atlas the bahloul fm in the se constantine basin and in northern and central tunisia the etel fm in the sirte basin the al hilal fm in cyrenaica libya the abu roash fm in the abu gharadig and fayium basins western desert egypt the daliyya fm along the ne sinai palestine isreal coast and the shueib fm in west central jordan

benthic ostracods and deep water masses in the atlantic ocean ostracod faunas at six locations are compared and related to distributions in an atlantic ocean wide data base five widely developed vertical faunal sequences are recognised at particular levels within deep water masses henryhowella fauna lower part of antarctic intermediate water krithe fauna upper north atlantic deep water poseidonamicus bosquetina fauna upper part of lower nadw dutoitella fauna lower part of lower nadw legitimocythere fauna antarctic bottom water these faunas are correlated with previously established deep water benthic foraminiferal assemblages and their possible palaeo oceanographic use is discussed

global campanian upper cretaceous ostracod palaeobiogeography abstract the distribution of 218 campanian marine ostracod genera from 38 geographical areas was used for a quantitative palaeobiogeographical analysis the data were analysed using multivariate statistical methods ordination methods and parsimony analysis of endemicity these methods resulted in distinct geographical area groupings of the studied regions with these groupings seven palaeobiogeographical units based on campanian ostracod occurrences are distinguished the composition of the area groupings and the distribution of the palaeobiogeographical units are discussed their development and spatial distribution are broadly controlled by campanian palaeoclimates partly modified by palaeogeographical conditions

biotic turnover in benthic foraminifera across the cretaceous tertiary boundary at el kef tunisia abstract the cretaceous tertiary boundary section exposed near el kef tunisia is the most complete boundary sequence known to date it contains nearly 1 m of black and gray boundary clay containing planktic foraminiferal zone poa b 2 m of clayey shales of p1a globigerina eugubina zone and 4 m of shales and marls of p1b g taurica zone quantitative analysis of the benthic foraminiferal fauna suggests that deposition during the latest cretaceous occurred in an upper slope to outer shelf environment which shallowed at the k t boundary to an outer to middle shelf depth and shallowed further by p1b time to mid shelf depth a major reduction in benthic diversity occurred near the k t boundary with about 50 of the fauna disappearing diversity remained an average of 37 lower during deposition of the first 3 m of sediment above the boundary poa b p1a and productivity was very low surviving and thriving foraminifers during this interval were primarily low oxygen tolerant epifaunal and infaunal species a sharp decrease in the low oxygen tolerant fauna and appearance of a shallow mid shelf fauna at about 4 m above the boundary p1b zone signals a second regression return to higher oxygen levels and higher productivity although the environmental effects of the k t boundary event can be inferred from benthic faunas the ultimate cause remains elusive faunal changes prior to and the long recovery period after the k t boundary are difficult to explain by a single impact hypothesis

high resolution planktonic foraminiferal analysis from the cretaceous tertiary boundary at ain settara tunisia evidence of an extended mass extinction the ain settara section located in the kalaat senan area of north central tunisia spans the cretaceous tertiary k t boundary which is characterized by a red layer and a thin non bioturbated boundary clay sediment accumulation across the k t boundary at ain settara was probably interrupted by three short hiatuses and or condensed sedimentation the first hiatus occurs at the top of the cf1 zone the second hiatus condensation occurred just below the boundary clay and the third hiatus at the p0 p1a boundary in the earliest danian these hiatuses are marked by weak unconformities bioturbation and sudden disappearances appearances of species which are known to disappear evolve sequentially in continuous sections quantitative high resolution planktonic foraminiferal analysis across zones cf1 upper p0 and p1a 1 reveals an extended and selective mass extinction all 41 of the species which disappeared at or below the k t boundary are rare to very rare and primarily ecologically specialized keeled deeper dwelling tropical subtropical forms globotruncana globotruncanita gublerina planoglobulina rosita contusotruncana racemiguembelina their combined relative abundance varies between 10 and 15 of the total population at the end of the maastrichtian the k t crisis thus appears more catastrophic when viewed in tropical subtropical assemblages and based on analysis of larger species 200 m which preferentially includes the more specialized forms though in fact the k t mass extinction actually involved a relatively small part of the foraminiferal population in terms of relative abundance the pattern of extinction and changes in dominant population at ain settara appear to be very similar to the planktonic foraminiferal turnover of the other north central tunisian sections el kef elles the selective mass extinction pattern suggests that the catastrophic effects of the bolide impact superimposed those related to long term environmental changes such as variations in temperature sea level and associated water mass changes

ecophenotypic variation of the devonian benthic ostracod species cavellina rhenana krommelbein 1954 a paleoenvironmental proxy for the ardenne france belgium and rheno hercynian realm abstract the morphological variation of the carapace of the ostracod species cavellina rhenana krommelbein 1954 is explored here quantitatively this species existed during the late givetian to the earliest frasnian and it is characteristic of the rheno hercynian area five morphological characters and several linear measurements of the carapace were analyzed on 260 complete carapaces coming from three different areas each of them representing a different paleoenvironment of the devonian ardennean platform the original species description and diagnosis are emended based on this newly observed variability in ornamentation sulcation curvature of the ventral margin marginal flattening and asymmetry of valves it is established herein that the morphological variation expressed in these five characters is independent of the ontogenetic growth morphological variation appears to be correlated with different types of facies reflecting a distinct depositional environment a high degree of morphological variation is found in facies of inner platform semi restricted environments while a low degree of variation is found in facies of outer platform open marine environments thus the degree of morphological variation of c rhenana is an indicator of the stability of the environment in the neritic realm while environmentally cued polymorphism is well documented in mesozoic to recent ostracods our study demonstrates the first devonian case of ecomorphism and suggests that intraspecific polymorphism of the ostracod carapace can be a useful tool for refining paleoenvironmental reconstructions