6533b860fe1ef96bd12c362a

RESEARCH PRODUCT

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

subject

description

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 Tuffeaude Saumur facies which at least develops till Châtellerault and contains the “Liron” marker level; (2) the upper part of the Tuffeau deBourré shows numerous firmgrounds; (3) the tempestites at the base of the Tuffeau Jaune de Touraine delivered an original ammoniteassociation where a new species, Romaniceras (R.) marigniacum, occurs with R. ornatissimum in the higher part of the R. ornatissimumzone (Tm 3); (4) consequently, the base of the Tuffeau Jaune de Touraine starts in the Middle Turonian and not in the Upper Turonian asit was traditionally admitted.