Notice explicative de la carte géologique de la France (1/50000).

Stratigraphy and stage boundaries in reference sections of the Upper Cretaceous Chalk in the east of the Paris Basin: the “Craie 700” Provins boreholes

Abstract The Provins boreholes (Poigny: Craie 701, and Sainte-Colombe: Craie 702) drilled in 1999 as part of the “Craie 700” project initiated by the Paris Basin Geologists' Association provide reference sections for the Upper Cretaceous of the eastern part of the Paris Basin. The lithology of the Cretaceous drilled at Poigny and Sainte-Colombe is presented in two logs displaying major litho-events that provide lines of correlation. Bio-events are expressed by the appearance/disappearance of index species of fossils. Foraminifera give a biozonation close to that defined by previous work on the Anglo-Paris Basin. Some of these bio-events provide a second set of lines useful for correlation. …

Les affleurements du Saumurois (partie occidentale du stratotype).

24 pages; National audience

Romaniceras (Yubariceras) ornatissimum (Stoliczka, 1864) : une ammonite rare dans les craies du Turonien moyen de l'Aube (France).

9 pages; International audience

Parcours géologiques au sein du stratotype Turonien.

19 pages; National audience

The global bio-events at the Cenomanian-Turonian transition in the reduced Bahloul Formation of Bou Ghanem (central Tunisia).

In central Tunisia, the thickness of the Bahloul Formation varies generally between 20 to 40 m such as for example, respectively, at wadi Smara near Kalaat Senan and at wadi Bahloul near Maktar. The thickness is also of several tens metres at Koudiat el Azreg near Jerissa and at Tajerouine. In these sites where the thickness of the Bahloul Formation is dilated, in addition to five geochemical events (d13C), nine bio-events were defined near the Cenomanian-Turonian transition, successively in ascending order: 1. LO Rotalipora cushmani, 2. Heterohelix bio-event, 3. FO Pseudaspidoceras pseudonodosoides, 4. LO P. pseudonodosoides, 5. LO Thalmanninella multiloculata, 6. “filaments” bio-event, Ce…

The Albian (Vraconnian)-Cenomanian boundary at the western Tethyan margins (Central Tunisia and southeastern France).

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…

Zones d'ammonites et de foraminifères du Vraconnien au Turonien : Une comparasion entre les domaines boréal et téthysien (NW Europe / Tunisie centrale)

International audience; Depuis la fin du 19ème siècle, l'intervalle comprenant l'Albien supérieur élevé, le Cénomanien, le Turonien et le Coniacien basal a été subdivisé d'abord en zones d'ammonites puis, à partir du milieu du 20ème siècle, en zones de foraminifères planctoniques, deux groupes de macro- et de microfossiles particulièrement efficaces en bio-chronostratigraphie grâce à leur taux d'évolution rapide. Toutefois, des différences de compositions fauniques entre le domaine boréal (Europe du Nord-Ouest) et le domaine téthysien (Méditerranée) ont longtemps empêché des corrélations précises entre ces deux domaines. Aujourd'hui, dans un intervalle de temps couvrant environ 16 millions …

Stage boundaries, global stratigraphy, and the time scale: towards a simplification

International audience; This paper examines four facets of stratigraphic terminology and usage considered faulty and proposes corrective measures. The four perfectible areas are: (1) The system of dual nomenclature requiring discrete terminologies for the superpositional and temporal aspects of rock units. (2) The premise that a GSSP establishes the base of a stage as being coincident with the top of the preceding stage rather than simply defining it as the boundary between stages. (3) The rejection of supplementary (auxiliary) sections that would broaden the knowledge of a GSSP and enlarge the area in which it is easily usable. (4) The current dual system of nomenclature for Precambrian an…

Late Cretaceous palaeoenvironments expressed by the clay mineralogy of Cenomanian–Campanian chalks from the east of the Paris Basin

Abstract The clay fraction of Cenomanian–Campanian chalks cored at Poigny and Sainte-Colombe, close to Provins (east-south-east of Paris), includes variable proportions of smectitic minerals, illite and kaolinite. The smectitic sediments (which constitute the background of low-terrigenous supply throughout the stratigraphic interval) resulted mainly from the warm, humid climate and high sea level that prevailed during Late Cretaceous in this area. During the Late Turonian, the smectitic sedimentation was interrupted by significant detrital inputs of illite and kaolinite. This reflected tectonic rejuvenation of landmasses coeval with an explosive volcanism expressed by the occurrence of bent…

Zonation by ammonites and foraminifers of the Vraconnian-Turonian interval: A comparison of the Boreal and Tethyan domains (NW Europe / Central Tunisia)

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…

New data on middle Turonian tuffeaux of southern Touraine and on their ammonites faunas.

The knowledge of the Turonian stratotype, “from Saumur till Montrichard“, along the Loire and the Cher valleys waspublished in 2018 by Amédro et alii. Since then, the study of recent collecting of ammonites in southern Touraine provided significant informationto state more precisely the Turonian zonation. New outcrops are described at Bourgueil, Chinon, Loudun, Usseau, Sossay,Marigny-Marmande, Séligny and Ports-sur-Vienne where the following formations were recognized: the Amboise Chalk, the tuffeaux ofArdilliers, of Saumur, of Bourré and the Tuffeau Jaune de Touraine.In these southern countries, it is pointed out that: (1) more than the upper half of the Amboise Chalk appears like the Tuff…

Les affleurements de la Touraine (partie orientale du stratotype).

17 pages; National audience

A North American ammonite fauna from the late Middle Turonian of Vaucluse and Gard, southern France: the Romaniceras mexicanum, Prionocyclus hyatti and Coilopoceras cf. springeri association

Abstract An unusual, exotic, ammonite fauna including Romaniceras mexicanum Jones, 1938, Prionocyclus hyatti (Stanton, 1894) and Coilopoceras cf. springeri Hyatt, 1903 is recorded from the late Middle Turonian of Vaucluse and Gard, southern France. It is the first record of this ammonite association outside the Gulf Coast region and the Western Interior of the United States of North America. Up to present, these species were considered as endemic to the Western Interior sea-way. The migration of numerous ammonites from North America to western Europe during the late Middle Turonian suggests it is linked to a transgressive event or to a short sea-level high.

Les bioévénements de la limite Albien (Vraconnien) - Cénomanien aux marges nord et sud de la Téthys (S.E. de la France et Tunisie centrale)

International audience; Les bioévénements de la limite Albien (Vraconnien) - Cénomanien aux marges nord et sud de la Téthys (S.E. de la France et Tunisie centrale) [Bioevents at the Albian (Vraconnian) - Cenomanian boundary at the North and South margins of the Tethyan Ocean (SE France and Central Tunisia)]