Lithostratigraphie et biostratigraphie des formations paléocènes et éocènes entre Bayonne et Pau (SW France)

The lithostratigraphy and biostratigraphy of the Paleocene and Eocene formations have been reconsidered on the basis of 18 dated boreholes that intersect the Basque Country, Peyrehorade, Sainte-Suzanne and Sauvelade allochthonous tectonic units, as well as the autochthonous units of the Pey-Saint-Lon anticline, the Arzacq Basin and the North Pyrenean Trough. Correlation of the formations identified in the boreholes and at outcrop has made it possible to outline the sedimentary evolution of this region during the Early Paleogene and to date the various stages of Pyrenean compression on the basis of sedimentary gaps and syntectonic detrital input. The Lasseube Formation is present over the entire study area. Sedimentation becomes differentiated during the Late Selandian-Early Ypresian period. In the North Pyrenean Trough and in the Peyrehorade, Sainte-Suzanne and Sauvelade units, the detrital-clayey Pont-Labau Formation is well developed and all its members are represented (Guillempau, Latapy, Néez, Libaros and Artigueloutan; zones upper P 3b-P 6b; upper NP 5-NP 11). A sedimentary gap showing erosion, and involving zones upper P 3b-upper P 4a and upper NP 5-NP 7, characterises the Basque units, the Pey-Saint-Lon anticline and the western part of the Arzacq Basin. Sedimentation recommences in zone P 8 with middle-bathyal deposits of the Cassoua Member and then continues with the Artigueloutan Member (transition facies towards the Louts Formation) or limestone resembling that of the Meilhan Formation. The Gan Formation shows an east-west polarity. In the east, between the Sainte-Suzanne Unit and the North Pyrenean Trough, the formation is argillaceous with a dominant neritic character, apart from a circalittoral to epibathyal passage in its lower part (zone P 7) containing numerous planktonic foraminifera. The formation is of a detrital and carbonate nature in the west (Sainte-Marie-de-Gosse 1). The bathyal Donzacq Formation appears to transgress a previously deformed surface. Two domains existed during the Lutetian: a continental to neritic domain in the south and a bathyal domain in the north (the Saint-Geours-d'Auribat and Miretrain formations) separated by a variably thick transition zone that is affected by thrust fronts. Two new formations - the Orthez and Sorde-l'Abbaye formations - are proposed, and the Marly limestone formation of Saint-Barthélémy (Douvillé, 1905) is redefined. The Orthez Formation (Sauvelade Unit) is composed of marl and continental conglomerate with neritic carbonate interbedding and belongs to the sub-zones NP 15a and b. The Sorde-l'Abbaye Formation (Peyrehorade Unit and the Basque units p. p.) is composed of neritic carbonate sediments (Lutetian-Priabonian). The Saint-Barthélémy Formation is made up of syntectonic conglomerate, turbiditic limestone and pelagic marl in the central part of the Basque units (NP 15a-NP 16). The Bartonian and Priabonian stages are characterised by carbonate sediments in the Arzacq Basin (Siest Formation). Its base is diachronous: Upper Lutetian (zone SB 16) in the east and Late Bartonian grading to Priabonian in the west (zones SB 17/18 and SB 19). The sediments are argillaceous (Côte des Basques Formation) along the Atlantic coast, in the central part of the Basque units and in the Bayonne-Cauneille syncline. Major thickness variations reflect tectonic phases at the top of the Lasseube Formation in the north (erosion pre NP 8), the Néez Member (NP 7/NP 8 boundary), the Artigueloutan Member (NP 11/NP 12 boundary), and the Gan Formation (P 8/P 9 boundary). The syntectonic conglomerate and breccia indicate the development of thrust fronts in the Libaros Member (NP 8), at the base of the Pillardou and Artigueloutan members (NP 9b, c-NP 10), in the Saint-Geours-d'Auribat Formation (NP 14b) and in the Orthez and Saint-Barthélémy formations (between zones NP 15a and NP 16).     

La transgression thanétienne (Paléocène supérieur) dans l’Aurès occidental (Algérie), d’après les associations de Foraminifères de la coupe d’El Kantara

In the W-Aures (Algeria), the El Kantara pass displays about 50 m of Red Marls overlying the Maastrichtian limestones with Laffitteina. The Red Marls are, in their turn, overlain by the Thanetian marly limestones of the river El Haï. The micropaleontological inventory of these Red Marls establishes the co-occurrence of subaerian (Microcodium = Paronipora), fresh-water (Charophyta) and marine microfossils (Foraminifers). The stratigraphical significance of these microfossils is discussed. The upper part of the Red Marls, yielding abundant Valvulina and scarce Glomalveolina, is of Thanetian age. The age of the lower part is less established, but the occurrence of Microcodium suggests a Thanetian age too. Located at the margin of the northern opening of the trans-Saharan epeiric sea, the El Kantara section establishes a Thanetian age for the beginning of the Paleocene transgression. Danian deposits are missing, in spite of the absence of an obvious hiatus on the field. After general emersion during the early Paleocene, the Thanetian transgression starts with the set up of lakes at the depositional area of the Red Marls. Marine influences, limited at first, become gradually prevailing, and end with the deposition of neritic marly limestones of river El Haï.     

Les foraminifères du Paléocène et de l'Éocène basal du sillon nord-pyrénéen (Aquitaine, France)

This paper presents for the first time the inventory of the Paleocene and Lower Eocene foraminifers located in the North Pyrenean trough, between the Atlantic Ocean and the neighbourhood of the town Pau. They have been studied from three outcrops. The Bidart Beach section shows the Lasseube Formation from the Cretaceous/Paleogene boundary to the base of the P 3a zone. The Loubieng Quarry section, near Orthez, represents the upper P 3a zone and the lower P 3b zone as well as the Lasseube Formation / Pont Labau Formation boundary. The interval between the upper part of the P 3b zone and the upperest part of the P 5 zone crops out along the Gan - Rébénacq road with a hiatus located at the Paleocene / Eocene boundary, the whole interval belonging to the Pont Labau Formation. 394 taxons of foraminifers are present in this formations: 349 benthic and 45 planktonic species. The Velasco type benthic foraminifers show a middle bathyal depositional environment, with a paleobathymetry included between 500-600 m and 1000 m: Nuttallides truempyi, Osangularia velascoensis, Bulimina trinitatensis. The Midway type species which were transported by the turbidite currents from the lower to middle neritic environments are frequent as well as the Cretaceous reworked species. The species number is low: 29 in the iridium layer of the Cretaceous/Paleogene boundary (P 0 zone). Fauna grows rich quickly in the Pα zone reaching 129 species. The diversity grows up progressively from P α to the P 4a zone (NP 8). The disappearances are rare until his horizon, but their number is bigger than the number of appearances from the P 4b zone. It reaches their maximum between the P 4c zone and the P 5 zone. It shows that the decline of the Paleocene fauna begins around 2 million years before the thermal event of the Paleocene / Eocene boundary in the Aquitaine sections. The disappearances stay important in the Lower Eocene - Ypresian, but the appearance of lots of Eocene species show that the fauna renewal is located in this stage. The Cretaceous taxa dominate in the Paleocene benthonic fauna. The appearance or the disappearance of some species has a stratigraphic value in the Aquitaine region: the disappearance of Coryphostoma incrassata in the P 1b zone, the appearances of Plectina dalmatina, Elongobula grata (P α); Bulimina tuxpamensis (P 2); Tritaxilina cubensis, Thalmannita madrugaensis (P 3a); Svenia bulbosa (P 3b); Discorbis perovalis (P 4a/NP 7); Elongobula pulchra, E. pupa, Asterigerina bartoniana, Neorotalia gr. tuberculata (P 4a/NP 8); Bigenerina pannonica, Pentellina pseudosaxorum (P 5/NP 9-10).     

Étude biostratigraphique et paléoenvironnementale des diatomées pyritisées de l'intervalle Paléocène supérieur-Éocène inférieur du sondage de Saint-Josse (France)

This paper presents the results of a biostratigraphic analysis of pyritized diatom assemblages in the Saint-Josse core (CC82) located in the northern part of the Paris basin (coordinates: X =555?000, Y =307?324 and Z =56.9 m). During the Paleocene-Eocene this locality was situated in a small bight of the North Sea Basin. The results are obtained from sediments of the Thanet and Mont-Bernon group equivalents belonging to the Paleocene-Eocene interval. Thirteen samples were studied and eleven contain pyritized diatoms. By epigenesis, the siliceous frustule of the diatom is changed into a pyritized skeleton with all the ornamentation very well preserved such as the velum, the areolae, the labiate processes, etc. Dispersive X-Ray analyses show this complete replacement of silica by pyrite. Another form of pyritization is crystallization of pyrite (in cubes, pyritohedrons, octahedrons, framboids) in internal cavities of the diatoms to produce internal moulds, also called steinkerns, which preserve the external morphology of the diatoms and some details such as the girdle. Despite pyritization, diatoms can often be recognized at the species level; brackish and marine species were observed but no fresh water specimens were encountered. Pyrite is easily altered into iron oxides. In outcrops, pyritized diatoms can be obscured or destroyed by oxidation. We have chosen borehole samples for this study to avoid the affects of weathering. Deposits from the Sorrus Unit (of the Thanet Group) have low abundances of pyritized diatoms (3 to 25 specimens per sample). This unit contains allochtonous diatom assemblages comprising Actinoptychussenarius, Coscinodiscus morsianus var. morsianus, and Coscinodiscus morsianus var. moelleri. Sample 34.31-34.45 from this unit is particularly interesting. It contains three specimens of Paralia siberica var. laevis, which is typical of an estuarine or littoral paleoenvironment, and corresponds to the more continental deposit of the Sorrus Unit. Seven samples, taken in the Argile de Saint-Aubin Unit (from the Mont-Bernon Group), contain more than 200 pyritized diatoms and between 9 to 16 different species per sample. A brackish assemblage (Actinoptychus senarius, Coscinodiscus commutatus and Stellarima microtrias) and a marine assemblage (C. morsianus var. morsianus, Coscinodiscus var. moelleri, Fenestrella antiqua, Odontellaheibergii, Rhizosolenia sp. 1 and Trinacria regina) are observed. The brackish assemblage expands in the upper part of the Saint-Aubin Unit indicating more widespread brackish paleoenvironmental conditions. Pyritized diatoms are important fossil markers in the Paris basin mainly when siliceous fossils (silicoflagellates or radiolarians) and others microfossils (foraminifers and dinoflagellates) are very poor or absent. Two diatom assemblages have been identified in the Saint-Josse borehole. The first assemblage D1, comprising C. morsianus var. moelleri (high occurrence), C. morsianus (a few) and T. regina (rare), is recorded in the Sorrus, La Calotterie, Bois Gorguette, Le Goulet and lower Saint-Aubin Units. The second assemblage D2, characterized by great abundance of F. antiqua and decreasing numbers of C. morsianus species, is found in the upper part of the Saint-Aubin Unit. These diatom assemblages can be correlated with other biozonations established in the North Sea basin and based on nannoplankton and diatoms (King, 1983), diatoms (Mitlehner, 1996) and calcareous nannoplankton (Martini, 1971). F. antiqua and C. morsianus var. moelleri are the more important diatom species encountered. F. antiqua (previously named Coscinodiscus sp. 1, King, 1983) is the fossil marker used by King to define his NSP4 biozone. The base of NSP4 corresponds to the lowest occurrence of F. antiqua and the top is marked by the highest occurrence of this species. The Sorrus, La Calotterie, Bois Gorguette, Le Goulet and Saint-Aubin (“Sparnacian” stage) Units, the last one comprising F. antiqua (increasing to acme), correspond to the NSP4 zone of King (1983). The Mont-Hulin and Château de la Bruyère Units correspond probably to the NSP5 zone of King (1983). F. antiqua and C. morsianus var. moelleri were also used by Mitlehner (1996) to differentiate the NSP4a zone (low abundance of F. antiqua and abundance of C. morsianus var. moelleri) from the NSP4b zone (great abundance and acme of F. antiqua). The abundance of C. morsianus var. moelleri is recorded in the lower part of Saint-Aubin Unit and the abundance of F. antiqua (high peak at 46% in the sample 17.87) is found in the upper part of Saint-Aubin Unit. Therefore, Sorrus, La Calotterie, Bois Gorguette, Le Goulet and the lower part of Saint-Aubin Units are correlated with the NSP4a zone and the upper part of Saint-Aubin Unit with the NSP4b zone. By correlating the calcareous nannoplankton biozonation (NP) of Martini (1971) with the biozonation of King (1983), adapted by Mitlehner (1996), the boundary between the NP9 and NP10 zones could be located in the 18.75-17.87 interval and the NP10-NP11 boundary at the top of Saint-Aubin Unit. Lithostratigraphic correlations between the units of the Saint-Josse borehole (Paris basin) and the formations of the North Sea basin can be established. The great abundance of C. morsianus var. moelleri and the great abundance (including acme) of F. antiqua are respectively recorded in the Sele and Balder Formations. Therefore, the interval Sorrus/lower Saint-Aubin Units is correlated with the Sele Formation and upper part of Saint-Aubin Unit with the Balder Formation.     

Un nouveau Bovini dans la faune du Pléistocène supérieur d’Algérie

During the study of the Quaternary Maghrebian bovines in 1985, the review of the Bovini (aurochs and buffalos) found in Upper Pleistocene sites of Algeria showed that in comparison with most of the African bovine assemblage the attribution of genus Pelorovis to the species antiquus was inappropriate. The biometric and cladistic data revealed a close kinship with genus Syncerus. Later, other authors’conclusions confirmed its relevance. The antique buffalo of the Aterian site of the Phacochoeri has all the characteristics of genus Syncerus, but is different in that it shows a certain number of specific characteristics described in this article.     

Evidence of fungal activity in silicified gymnosperm wood from the Eocene of southern Patagonia (Argentina)

Evidence of fungal activity expressed as typical decay patterns is described from silicified podocarpaceous wood from the Eocene of Patagonia, Argentina. Decay features consist of tracheids of the secondary xylem that are degraded, resulting in thin-celled, lignin-free, translucent, circular to elliptical areas, some of which have cells devoid of all cell wall components including lignin, hemicellulose, and cellulose, and other areas that show only partial simultaneous decay of all cell wall layers. These patterns conform to the white rot and its variant white pocket rot decay patterns produced by basidiomycetes and ascomycetes in gymnosperm and angiosperm wood in modern terrestrial ecosystems. Coagulated opaque bodies in the lumen of some cells and enlarged secondary walls may represent host reactions to infection or remains of metabolic products of fungal enzymatic activity. Similar decay patterns and reaction features have been described from fossil woods ranging in age from the Devonian to the present. This record expands the fossil record of wood rot fungi and underscores their importance as drivers of biological cycles in ancient terrestrial ecosystems.     

Fimbria lohani (Mollusca : Bivalvia) nomen novum pro Fimbria subpectunculus (d’Orbigny, 1850) du Lutétien (Éocène moyen) du bassin de Paris,nom préoccupé

Fimbria lohani (Mollusca: Bivalvia) nom. nov. pro Fimbria subpectunculus (d’ Orbigny, 1850) from the Lutetian (Middle Eocene) of Paris basin, name preoccupied. The names Fimbria magna ( Anton, 1838) and Fimbria subpectunculus (d’ Orbigny, 1850) are nomenclaturally invalid to designate the species from the Lutetian (Middle Eocene) of the Paris Basin. Fimbria lohani nom. nov. is proposed here as a replacement to correct the homonymy Corbis subpectunculus d’ Orbigny, 1850 non d’ Archiac, 1850.     

Données paléoenvironnementales sur le Vraconnien/Cénomanien de la région de Tébessa (Atlas Saharien,nord-est Algérie). Caractérisation de l’OAE2

The micropalaeontological content of five sections, located in Northeastern Algeria (Saharan Atlas) was investigated by means of washing/counting of microfossils in marly levels, and microfacies analyses of calcareous levels. In these levels of Upper Cretaceous age, hundred species of foraminifera were identified but only about 15 species of ostracoda and about ten of radiolaria. This work allows, first of all, to establish a rather precise stratigraphic frame, in particular by means of studying planktonic foraminifera. Two to five biozones were defined, between the Vraconnian (Th. Appenninica biozone) and the early Turonian (Whiteinella archaeocretacea biozone, then Helvetoglobotruncana Helvetica biozone for certain sections). Secondly, the quantitative analyses led on foraminifera allowed the definition of palaeoenvironment. The ratio P/P+B, generally very high, coupled with a little diversified benthonic microfauna, indicates a calm and deep environment, of external platform or slope type. Furthermore, at numerous levels, various indications give evidence of the existence of a strong surface productivity (presence of upwellings), responsible for the proliferation of radiolaria (late Vraconnian/early Cenomanian especially) or of globular planktonic foraminifera (hedbergellids/heterohelicids); being both associated with low-oxygen deep waters. Two anoxic events were also revealed, the first one at the end of Vraconnian (OAE1d) and the second at the end of Cenomanian (OAE2). This last event in particular was characterized on all the sections, in a more or less detailed way, thanks to the identification of certain indicator: Heterohelix “bloom”, “filament” event, disappearance of rotaliporids, presence of “blackshales” strongly enriched in organic matter (Bahloul levels).     

Étude taphonomique, paléoécologique et archéozoologique des faunes de grands mammifères de la seconde moitié du Pléistocène inférieur de la grotte du Vallonnet (Roquebrune-Cap-Martin, Alpes-Maritimes, France)

Vallonnet cave (Alpes-Maritimes, France) provided archaic lithic tools together with a big amount of large mammals of the end of lower pleistocene. At the crossing of diverse ecological niches in time and space, three main levels and within them several smaller units were distinguished. The poorly mineralized bones witnessed a huge diagenetic fragmentation. The presence of the animals in the cave seems to be linked to the reasons of their death. The exhaustive and systematic observation of the bones, like the bears probably used to die inside the cave. Some other carnivores especially hyenas, used the cave as a nursery. Man also occupied the cave and had an activity mainly on large cervid bones and on some other species as well. The very progressive deposit gave a way for carnivores and porcupine to gnaw the bones on the ground before their burial. The succession of actions (man, carnivores and porcupine) on the same bones is characteristic on Vallonnet large mammals bones.     

Les Cervidae (Mammalia, Artiodactyla) du Pléistocène supérieur-Holocène ancien de la région du Parc National Serra da Capivara (Piauí, Brésil)

The Upper Pleistocene/Lower Holocene fossil-bearing sites of the Serra da Capivara National Park Region have yielded three cervid species: Mazama gouazoubira, M. americana and Blastocerus dichotomus, all currently living in South America, the two first in the region. A grand total of more than one hundred remains demonstrates the presence of Mazama gouazoubira in seven sites, mainly the Toca das Moendas, the Toca do Serrote do Artur, the Toca da Cima dos Pilão. This small species shows, since the Upper Pleistocene, a conspicuous tendency to reduce the average dimensions of its teeth and long bones. From the taller M. americana, only a dozen of remains were found in four sites, mainly the Sitio do Meio. In all of these it is sympatric with M. gouazoubira. It differs from this last one by its cheek teeth and its limb bones size and proportions. The oldest site where the species is known is Tarija (Bolivia, Middle Pleistocene) and it does not show any significant changes in size and proportions between recent and fossil samples. Sixteen remains of the large B. dichotomus were found in five sites, mainly the Toca das Moendas and the Toca da Barra do Antonião. The species is a rare fossil, but is frequently figured in the rock art painting of the region, where it is presently unknown.     

Des Miliolacea aux Alveolinacea (grands foraminifères): la faune du Crétacé supérieur et du Tertiaire inférieur du Chiapas (S.E. Mexique)

Found in Chiapas (South-East of Mexico), Praealveolina michaudi nov. sp. and Chubbina jamaicensis (of Campanian-Maestrichtian age) are described, both evolved from Nummoloculina sp. while Raadshoovenia guatemalensis (upper Paleocene-lower Eocene) arises from Quinqueloculina. We precisely analyze and modelize the nepionic coiling during the evolutionary change from Miliolacea to Alveolinacea. During ontogenesis as well as during phylogenesis, quinqueloculine coiling progresses to streptospiral and then to planispiral chamber arrangement with the increase of volume of embryo and of chambers. Appearance of these large foraminifers are understood as a consequence of the rise of K-strategies in their mode of life, following the development of photosynthetic symbioses.     

Échinodermes de l'Ordovicien supérieur (Ashgill) de Sardaigne et d'Algérie

Research on the influence of sea level variations on the benthic faunas have been carried out in the Upper Ordovician of Sardinia. Study of the depositional facies and sequence analysis of the upper part (Lower Ashgill) of the Portixeddu Formation led to the identification of the sedimentary environments. Cystoids and crinoids are associated to bryozoans and brachiopods in most levels. The numerical analysis of associations and megaguilds shows that crinoids and cystoids have a higher frequency in the proximal and median facies of the upper offshore. The columnal association characterized by Conspectocrinus celticus and the coronoid Mespilocystites tregarvanicus has been discovered in the upper part of the formation. This material and complementary samples from Upper Ordovician of Sardinia and Kabylia (Algeria) bring additional data on the systematic and show the wide distribution of this fauna outside of the Ibero-armorican domain. The distribution of this echinoderm association supports a palaeogeographical position of the Ibero-armorican domain and Sardinia within the north gondwanan margin during the Lower Palaeozoic.     

Comparaison de l'expression de certains caractères crâniens sur les hominidés chinois du Pléistocène récent et de l'Holocène (grotte supérieure de Zhoukoudian, sites de Longxian et de Yanqing)

The human remains recovered from “Grotte supérieure de Zhoukoudian” are the best-preserved Late Pleistocene human fossils in East Asia. For decades, as the representative of the Late Pleistocene human in East Asia, the Upper Cave skulls have been playing important role in the research of origins of modern Mongoloids and American Indians. With the advance of the origin and evolution of modern humans, more attention has been paid to the details and the mechanisms for the late Pleistocene human evolution and the formation of modern human populations. Both the origin and diversification of modern humans have been stressed. Some studies further trigger the debaters on the Upper Cave Man concerning its evolutionary level and its role in the formation of modern human populations in East Asia. To further explore these problems, we examined and compared 12 non-metric features on the 3 Late Pleistocene Upper Cave skulls and 162 Holocene individuals earthed from two archaeological sites of North China (Longxian and Yanqing). Our results indicate that 8 on the 12 features have different expression patterns between Upper Cave Man and recent Chinese leading the authors to believe that more primitive expressions appeared on the Upper Cave Man than on recent Chinese populations. Based on these findings, some problems on the intragroup variation in Late Pleistocene and Holocene populations are discussed.     

Les premiers Européens et la dynamique des interactions avec leur environnement : comportement écologique et niveau de cognition

Men and Carnivores used to live very closely during the Lower Pleistocene as show the assemblages. This allows us to reconstruct their behaviors and to bring up the idea that they used to share an ecological niche. It is also possible to understand the evolution of their behaviors, as regards the food supply, and the way they used to live in the sites. The first Europeans had a great capacity for adaptation, as well as a certain vulnerability, just like the Carnivores. The acquisitions of specialized technics are likely to have reduced this capacity for adaptation, as they got free from their opportunistic predator position.     

Ostracodes et stratigraphie du néogène et du quaternaire méditerranéens

A stratigraphical chart of marine ostracoda from Lower Miocene to Recent is established. Selected species (approximatively 220) are those morphologicaly well characterized and known from different parts of the Mediterranean area. It appears that: • lower Miocene ostracodes are still poorly known; • specific diversity is high during the Tortonian and the Lower Messinian before the complete disappearance of marine Mediterranean species during the Upper Messinian évaporitic episodes; • during the early Pliocene, about half of the Upper Miocene marine species are reintroduced with the Atlantic waters; other species migrate for the first time in the Mediterranean Sea by the same way; • at the end of the Pliocene or at the beginning of the Pleistocene several species known in Mediterranean since the Middle Miocene or before, such as Cytherella sp. gr. transversa and Ruggieria tetraptera, as well some “nordic guests” such as Hemicythere villosa and Cythere lutea, appear. This work is an opportunity to confirme a Late Miocene age for the Neogene of Skyros (Aegean Sea), to assign the “Upper Pliocene” of Terquem to the Lower Pleistocene and to refute the existence of a pliocene psychrosphere.     

Biostratigraphie des brachiopodes et âge carixien (Pliensbachien inférieur) des calcaires à grands bivalves en Algérie occidentale

Recent researches on the Lower Jurassic of Western Algeria allow to establish a lithostratigraphic standard correlating the different members and formations developed in the Ouarsenis and Tlemcen Mountains, the Oran High Plains, the Nador and Ksour Mountains. The position of the large bivalve limestones (= Lithiotis limestones) is well established in the different lithologic successions. This facies is widespread in Western Algeria where it is interbedded with brachiopod marker beds, indicating short periods of maximum flooding. The large number of collected brachiopods are distributed into four “faunas” (assemblages) ranging from the Late Sinemurian (= Lotharingian) to the Early Pliensbachian (= Carixian). These faunas have been dated by the age of the species that they have in common with the NW european and western tethyan provinces. These chronological data are confirmed by rare ammonites. All these results evidence the age of the large bivalve facies in Western Algeria. They are contained in the Middle to Late Carixian (Demonense and Dilectum Zones). This datation is in conformity with that known from the Eastern High-Atlas (Bou Dahar). Consequently, the large bivalves cannot be considered as “markers for the unique Domerian” as it has been too often asserted. The palaeontological part of our study shows that the multicostate Zeilleriids (several Tauromenia species from the Late Sinemurian to the Early Carixian) are older than the multicostate Terebratulids (Hesperithyris species from the Middle to Late Carixian).     

Ostracodes bathyaux du Crétacé terminal - Éocène moyen en Atlantique tropical (Plateau de Demerara, Leg 207)

Ostracode faunal assemblages which lived in bathyal environments are analysed from uppermost Maastrichtian - middle Eocene sediments of sites 1260 and 1261, drilled on the distal margin of Demerara, off Surinam (Leg 207, western tropical Atlantic). As for numerous other groups, the Cretaceous/Tertiary mass extinction event led to the disappearance of numerous bathyal ostracode species and it was followed by a very slow recovery during the Palaeocene. It appears that this extinction event was more devastating for detritus-feeder ostracode species than for filter or silt-eater groups, which crossed the K/T boundary without any or little morphological change. This extinction selectivity may be explained by the drop in productivity of surface waters which took place at the K/T boundary. Finally, psychrospheric ostracode species were encountered in Middle Eocene sediments, confirming thus the general cooling of deep oceanic realm recognised in general for this time interval.     

Les Schackoïnes (Foraminifères planctoniques) de l’Albien supérieur du Blake Nose (marge atlantique de la Floride, Leg ODP 171B)

A study of rather rich and well-preserved material from Upper Albian levels of Site 1050 of ODP Leg 171B led us to review the criteria used in the subdivision of the schackoinids into two genera and to describe a new morphotype, Schackoina leckiei n. sp., the phylogenetic position of which is examined within the group.     

Proposition d’une échelle chronométrique autour de la limite Crétacé-Paléogène par cyclostratigraphie : coupe de l’Aïn Settara (Kalaat Senan, Tunisie centrale)

The Aïn Settara section (Kalaat Senan, Central Tunisia) exposes in very good conditions a continuous marl-limestone alternation, going from the Upper Maastrichtian to the Danian. The Cretaceous-Palaeogene boundary is particularly better exposed than it is in the El Kef type section. The studied section reveals, at first, a typical bed-interbed decimetric to metric limestone-marl alternation. Upon this one, at a meter scale, a second mode of alternation is superimposed: between, firstly, sharp and thick bed-interbed bundles, and, secondly, more diffuse and thinner bundles, which are more difficult to split into beds and interbeds. This frame deals with the equinoxial-precession climatic-forcing. The bed-interbed alternation corresponds to the precession of 21.3 ka average period. The clear bundle-diffuse bundle alternation, comes from the amplitude modulation of the precession by the circa 100 ka period of the eccentricity. This succession is used to build a time floating-scale, adjusted on the Cretaceous-Palaeogene boundary. Fixing this boundary to the value of -65.0 Ma, we obtain a chronometric time-scale, going, for our section, from -65.8 up to -64.4 Ma, that is a total duration of 1.3 m.y. This scale allows to better localize in time the sedimentary and biological phenomenons, which encompass the Cretaceous-Palaeogene boundary.