Marie-José Fondecave-Wallez

Stratigraphie séquentielle comparée et ≪ gradedatation ≫ par les foraminifères planctoniques du Campano-Maastrichtien et du Paléocène de quelques sites d'Europe sud-occidentale et d'Afrique du Nord

From the analysis of the open marine beds enclosing the K/T boundary along several cross-sections of SW Europe and North Africa, a subdivision is proposed into nine Campanian-Maastrichtian depositional sequences followed by five Palaeocene sequences. These sequences have been correlated from one section to another by means of planktonic Foraminifera classic biozones and supported in the Cretaceous by numeric ages coming from the grade-dating method applied to Globotruncanids. In the latter case, sequences belong to two different types separated by the presence or the absence of lowstand chaotic deposits such as breccias and olistostromes. The dark clays of the K/T boundary containing the Iridium anomaly can be regarded as a 3d order sequence boundary. They also correspond to the base of a 2d order cycle which is locally (Beam) underlined by a gap of the Early Palaeocene, the underlying Maastrichtian marls, everywhere grade-dated around 65.2–65.3 Ma, never being significantly eroded.

Mise en évidence d'un sillon marin à brèches paléocènes dans les Pyrénées centrales (Zone interne métamorphique et Zone nord-pyrénéenne)

Abstract The discovery, in several localities, of significant planktonic Foraminifera, Danian–Selandian in age (P1c–P3 interval), both in the matrix of polygenic, post-metamorphic and post-tectonic debris-flow breccias (Comus Breccia Fm.) and in argillaceous hemipelagites, interbedded within these breccias, evidences the occurrence, during Palaeocene, of a longitudinal east–west marine trough, particularly open towards the Atlantic Ocean, within the present Internal Metamorphic Zone (and adjacent North-Pyrenean areas) of Central Pyrenees, from Aude to Haute-Garonne. This new dating shows the major importance of the Upper(most) Cretaceous compressions in the structuration of the tectorogenic axis of the range.

Latest-Cretaceous/Paleocene karsts with marine infillings from Languedoc (South of France); paleogeographic, hydrogeologic and geodynamic implications

The Latest Cretaceous/Paleocene paleokarsts from Bas-Languedoc (South of France) are characterized by : 1) exokarstic paleosurfaces (sink holes, pinnacles, canyons) which are mostly superimposed onto the Late Jurassic limestones and partly filled up with breccias and sandy clays containing Paleocene planktonic foraminifera; 2) endokarstic cavities filled up by sandy pelites and laminated mudstones with similar micropaleontological assemblage. All these cavities constitute three cut-and-filled paleokarstic systems. A general model of formation for this polyphase system is proposed. These paleosurfaces are generated by a Latest Cretaceous tectonic phase and Paleocene movements associated with eustatic rises inducing rapid floodings. During Upper Danian-Lower Selandian times three successive base levels drops, whose cumulated duration could be as long as 3 Ma, have induced several hundred metres of incisions within the exposed Jurassic carbonate series. A paleogeographic reconstruction shows three main marine gulfs which extend towards NE the EW Pyrenean thrust belt (“Pyrenean Paleocene Trough”, PPT) located on the axis of the future Pyrenees. The similarity of the facies and micropaleontological content in the two domains suggests connexions between the marine Paleocene deposits of Bas-Languedoc and the PPT. It could thus explain the succession of the same tectono-eustatic events. We propose, as an hypothesis, that the rapid sea-level changes, as recorded by the imbricated karstic paleomorphologies, could be induced by the closing and the opening of a strait in the Eastern part of the PPT acting as a sill. This would be controlled by tectonic movements along the active orogenic axis of the Pyrenean Range and eustatic variations of the Paleocene World Ocean. The karstic systems developed during these low-stand episodes may have been later reactivated after the Early Selandian and more specifically during the Messinian desiccation event. This late evolution may have generated deep flooded karsts, now situated below the present sea level. Such karsts, partly inherited from Paleocene, could be important aquifers of economic interest.

Présence de Paléocène marin dans les Grands Causses (France)

Identification of Palaeocene marine sediments in the Grands Causses (France). In the Grands Causses, incised valleys, lapies, fissures and sinkholes inherited from successive polyphase karstifications were filled by Palaeocene marine sediments overall assigned to the P1c–P3 interval (Upper Danian–Lower Selandian). These sediments are distributed into three detritic facies, generated by extensional tectonics controlling karstic and erosional processes. Upper Cretaceous marine fossils known within these facies are interpreted as reworked from hypothetically pellicular deposits. The probable palaeogeographic connection with the Pyrenean Palaeocene ‘Breccia trough’ supposes the presence of a SE–NW ‘ria’ running across the continental areas of Lower Languedoc and draining towards the northwest the marine waters of the Palaeocene transgression as

L’ olistostrome coniacien de Lordat (Pyrénées ariégeoises) et son équivalent latéral de Vicdessos, témoins d’un nouveau bassin d’avant-pays au front nord de la Haute Chaîne Primaire

ResumeDe nouvelles datations et grade-datations fondees sur les Foraminiferes planctoniques, ponctuellement identifies en depit d’un epimetamorphisme campanien, permettent de doubler voire a triper l’etendue du « sous-bassin » coniacien de Lordat (Zone des Ecailles Bordieres, Ariege), en partie calciturbiditique, aux depens terrains jusqu’a present tenus pour paleozoiques, tels ceux de l’ex-« Ecaille paleozoique de Lordat ». Ces derniers correspondent a des olistolithes de tres grande taille au sein d’un vaste olistostrome (château de Lordat, ermitage de Saint-Pierre), lui-meme inclus dans une epaisse serie monoclinale, a dominante calcschisteuse, constituant un probable equivalent lateral du « Flysch a Fucoides ». Cette serie deborde vers le Nord jusque sur la Zone Interne Metamorphique, comme le demontre l’âge neocretace du lambeau ex-paleozoique de Carmilles, directement chevauche par le massif Primaire nord-pyreneen de Saint-Barthelemy. Plus a l’Ouest, le « sous-bassin » de Vicdessos, prolongeant celu...

La limite Crétacé-Tertiaire en domaine marin dans les Pyrénées centrales (zone sous-pyrénéenne, France)

Abstract The discovery of Paleocene planktonic Foraminifera (subzones P1c to P3b) in the western sub-Pyrenean zone (Haute-Garonne) made it possible to locate an anomalously high abundance of iridium at the Cretaceous-Tertiary boundary underlining the interface between the ‘calcaires a Bryozoaires/calcaires a Algues, of Larcan-Nizan’, newly assigned to Danian-Selandian and the underlying ‘marnes bleues de Saint-Loup’, the top of them being Uppermost Maastrichtian in age (Hariaensis zone and grade-datation of 65.47 Ma). A short gap (subzones P0 to P1b, Lowermost Danian) probably marks, as in Bearn, the base of the Paleocene Larcan-Nizan Bryalgal limestones.

Diachronism in the sedimentary cover around the Troodos ophiolitic massif (Cyprus)

The detailed micropaleontologic study of the sedimentary series overlying the youngest ophiolitic basalts of the Troodos massif (Cyprus), confirms the late Campanian age of the top of the oldest terrigenous cover (Kannaviou Formation) topping these ophiolites themselves assigned to Cenomanian-Turonian. It also demonstrates for the first time the strong diachronism of the Lefkara Formation chalky limestones, unconformably overlying either the Kannaviou Fm. sandstones and clays, or the oceanic basalts. This diachronism over short distances and the on-lap of the Lefkara Fm. are revealed by varying stratigraphic gaps within the Paleocene-Miocene interval and are indicated by new age datings of the transgressive basal part of the Lefkara Fm. along six principal sections: late Thanetian (Zone P5) at the Pano Lefkara typelocality; early Ypresian (Sub-zone P6a) at Agia Anna; earliest Bartonian (Zone P13) at Kannaviou and Analiontas; early-middle Lutetian (Zones P10 to P11) at Kofinou; Langhian (Zone N8) at Choulou. Maastrichtian deposits are missing and Maastrichtian Globotruncanidae/Heterohelicidae only observed as individual reworked specimens within well-dated Tertiary levels. Finally, we discuss the influence of the Tertiary extensional brittle tectonics on this diachronism, the on-lap processes and the differential subsidences occurring after the late Cretaceous/? early-middle Paleocene folding (Laramian compression).

Reply to comment on Latest-Cretaceous/Paleocene karsts with marine infillings from Languedoc (South of France) ; paleogeographic, hydrogeologic and geodynamic implications

Our paper 1) describes in detail three successive paleokarstic incisions formed in a continental environment, each one later filled with sediments containing marine fauna. The altitude distribution of the analysed outcrops implies successive base-level falls and rises with an amplitude of hundreds of metres. 2) Incidentally, it occurs that the youngest marine fauna found in the successive paleokarst fillings is early Paleocene in age ; we therefore assume that in spite of the very rare occurrence of older reworked benthic fauna, the successive phases of karst formation and marine filling occurred during early Paleocene. Surprisingly, Bilotte et al.’s comment neither question the former point, nor the geological processes responsible for such an original setting. We would have welcomed any constructive suggestion in order to solve this outstanding problem, which, we believe, is now the most exciting scientific question to be addressed. Instead, the virulent comment focuses on the age of the sedimentary filling and challenges the Paleocene age we have determined. Even more surprisingly, the comment never refers to, nor it brings additional or contradictory observations on the specific localities analysed in the paper, but rather criticises some of our previous publications dealing with different geographical locations such as the French and Spanish Pyrenees. This results in a confusing case, in which scientists unfamiliar with our previous papers can hardly decipher the argument, unless they recover the dozen incriminated papers and as many counter-publications put forward by Bilotte and coauthors. We therefore reply to Bilotte et al.’s comment without expanding on the localities and topics relevant to previous works published elsewhere.

Sequence Stratigraphy and Grade-Dating in the Senonian Series from the South-Pyrenees (Spain), the Sedimentary Record of Eustacy and Tectonics

A new stratigraphic procedure that combines sequence stratigraphy and grade dating based on chronometric calibration of Rosita fornicata lineage evolution is applies to the analysis of the South Pyrenean Senonian Basin. These methods give eustatic and biometric curves both constructed according to Haq’s chronology and they permit time-correlations without variations in accuracy. In this way, two kinds of stratigraphic units are recognized and numerically dated from the Senonian-Early Danien in the South-Pyrenean foredeep Basin. These units are: eustatically-controlled depositional sequences; and tectonically-controlled depositional sequence sets.

Sr-ages and grade-datings in the area of the Lower Miocene near Bordeaux (Aquitaine Basin, France)

Abstract Twelve Sr-ages, recently obtained within the Aquitanian and Burdigalian deposits near Bordeaux are consistent with the grade-dating already published from the same localities. These two interpolation methods of radiometric ages support each other.