Search results for "Albian"
showing 10 items of 12 documents
Environmental and climatic controls of the clay mineralogy of Albian deposits in the Paris and Vocontian basins (France)
2020
18 pages; International audience; High-resolution clay mineral analyses were performed on lower and middle Albian deposits from the Paris and Vocontian basins in order to specify the weathering conditions that prevailed at that time. The clay mineral assemblages are composed of small proportions of chlorite and vermiculitic clays associated with abundant illite, R0 type illite-smectite mixed-layers (smectite) and kaolinite. Clay minerals originated from the physical alteration and chemical weathering of rocks and soils outcropping on the Variscan massifs bordering the studied areas. In the Paris Basin, the covariation of illite and kaolinite suggests the reworking of these latter minerals f…
Report on the 4th International Meeting of the IUGS Lower Cretaceous ammonite working group, the "Kilian Group" (Dijon, France, 30th August 2010).
2011
8 pages; International audience; The 4th Kilian Group meeting (Dijon, France, 30th August 2010) focused on the Aptian and Albian Stages. For the Aptian, a two-fold division of the stage was adopted for the Mediterranean area with a boundary between the Dufrenoyia furcata and Epicheloniceras martini Zones. The main changes to the zonal scheme concern the Lower Aptian with: the introduction of a Deshayesites luppovi Subzone in the upper part of the Deshayesites oglanlensis Zone; the replacement of Deshayesites weissi by Deshayesites forbesi as new indexspecies of the second interval zone; the introduction of a Roloboceras hambrovi Subzone in the upper part of the D. forbesi Zone; and the subd…
Isotopic seawater temperatures in the Albian Gault Clay of the Boulonnais (Paris Basin): Palaeoenvironmental implications
2016
13 pages; International audience; Oxygen isotopes were measured on several types of fossil hardparts from the Gault Clay Formation including benthic and planktonic foraminifera, belemnite guards, and fish small-teeth. Belemnites δ18O values indicate low temperatures (13.5–19.3 °C) with an increase from the Middle to Late Albian. Foraminifera provide variable δ18O values, some too low to be relevant in terms of temperature (until 42 °C). These low values probably result from a diagenetic alteration of the foraminiferal tests even though SEM observations revealed well-preserved microstructures. However, higher foraminiferal δ18O values recorded in some levels indicate temperatures in the rang…
Microcrinoids from the lower and middle Albian of the Anglo-Paris Basin (southern England, UK, Seine Maritime, Pas de Calais and Aube, France).
2021
16 pages; International audience; Microcrinoids of the family Roveacrinidae Peck, 1943 are described from lower and middle Albian clays of the Anglo-Paris Basin (Seine Maritime, Pas de Calais and Aube, France; Kent and Bedfordshire, UK). They are referred to two subfamilies - the Orthogonocrininae Gale, 2019 and the Plotocrininae Gale, 2020. Orthogonocrinines include the long-ranging (middle Albian-lower Cenomanian) species Orthogonocrinus apertus Peck, 1943, and Styracocrinus peracutus (Peck, 1955), known from Texas, USA, Morocco, the UK and France, and two stratigraphically successive species of the genus Hyalocrinus, H. magniezii Destombes, 1984 and H. bulliensis Destombes, 1984, known o…
Influences boréales dans le bassin de Mons (Belgique) à l'Albien
2007
International audience; The occurrence of marine dinoflagellates (including Cauca parva from the Boreal Province), acritarchs and the organic lining of foraminifers suggest Boreal marine influences in the Wealden facies of the Mons basin (Belgium) during the Late Albian.
Distribution of Albian clastic deposits in the Benguela basin (Angola): evidence of a Benguela palaeocurrent?
2009
Abstract The Albian clastic Tuenza Formation of the Benguela basin (south Angola) is described and its geographic distribution analysed in detail. From these observations, the existence of an Albian “PalaeoBenguela current” is proposed. This would imply that a marine longshore current reworked the sand transported by palaeorivers and settled it northward along the coast of the young Atlantic Ocean (during the Albian). A parallel between Albian clastic deposits and the modern sediments deposited by the Benguela current is drawn, focusing on the striking resemblance between the two currents, i.e. the actual Benguela current and the Albian marine current, and the associated sedimentary bodies.
The Albian (Vraconnian)-Cenomanian boundary at the western Tethyan margins (Central Tunisia and southeastern France).
2008
AbstractThrough the description and interpretation of the position of macro- and microfossils in several sections of the Albian-Cenomanian boundary in SE France and Central Tunisia, a comparison is made between the north and south margins of the Tethyan Ocean by using the occurrences of marker bioevents. For the planktonic foraminifera, the criterions applicable for the accurate determination of Thalmanninella globotruncanoides (Sigal) – the marker species for the base of the Cenomanian stage – are discussed. The species Th. globotruncanoides and the intermediate forms with its ancestor Th. caroni (Ion) are illustrated. For the ammonites, two subjects are new. Firstly, the species Stoliczka…
Zonation by ammonites and foraminifers of the Vraconnian-Turonian interval: A comparison of the Boreal and Tethyan domains (NW Europe / Central Tunis…
2008
International audience; Since the end of the 19th century the interval comprising the uppermost Upper Albian, the Cenomamian, the Turonian and the basal Coniacian has been subdivided, first into ammonite zones, then, beginning in the middle of the 20th century, into zones of planktonic foraminifera. These two groups, one macrofossil, the other microfossil, are particularly effective for bio-chronostratigraphy thanks to their rapid rates of evolution. But differences in the faunal makeup between the Boreal domain (northwestern Europe) and the Tethyan domain (Mediterranean) have for a long time hindered precise correlation of the two domains. Today, in a time interval covering about 16 millio…
Support for a Vraconnian Stage between the Albian sensu stricto and the Cenomanian (Cretaceous System)
2008
The geological scale for the middle Cretaceous currently used throughout the world was proposed by Alcide d'Orbigny in the XIXth century between the years 1842 and 1847 and establishes the succession of stages as Albian, Cenomanian and Turonian. In 1868 Renevier proposed that a supplemental chronostratigraphic division be intercalated between the Albian and the Cenomanian: the Vraconnian stage. This term was not generally accepted and after a period when it was referred to by Breistroffer (1936) as a substage constituting the upper part of the Albian, as an equivalent of the Stoliczkaia dispar ammonite Zone, its abandonment was "recommended" by the Conference on the Lower Cretaceous held in…
Patterns of Puffing Activity in the Polytene Chromosomes of Drosophila Subobscura
1982
The puffs and Balbiani rings are the visible expression of sites of genetic activity (Beerman, 1952). Since Beermann’s original hypothesis, puffing patterns for several species of Diptera have been described. Thus for the genus Drosophila, Ashburner (1967, 1969a and 1969b) has reported the puffing pattern of Drosophila melanogaster and Drosophila simulans, Beredens (1965) of Drosophila hydei, and Moriwaki and Ito (1969) of Drosophila ananassae. In a previous paper Frutos and Latorre (1981) have determined puffing patterns of the J and U chromosomes of Drosophila subobscura. This species shows a rich chromosomal polymorphism and the puffing pattern of several chromosomal rearrangements of th…