Les Pectinidae mioce`nes des faluns (Ouest de la France). Inte´reˆts biostratigraphiques des associations

The Miocene Pectinidae from the “faluns” (W France). Biostratigraphical interests of the associations. New sampling was realized throughout neogene outcrops occurring in Western France (mainly, “faluns” of Langhian to Tortonian age from Touraine, Anjou and Ble´sois). It has been known for long that the species or associations of the representatives of the family Pectinidae vary in each outcrop, but it was still necessary to get original data, which were collected precisely in their original level. Such a work is still in progress in Mediterranean areas. It seems that the systematic framework of several species has still to be detailed; the recently re-discovered species may be 12 in number. The species may characterize four main assemblages: rich and poorly diversified faunas, collected in microconglomerates, deposited in shallow environments; rich and diversified association, corresponding to the bryozoa facies deposited in deeper environments (“savignean” facies Auct.); poor assemblage, collected in shallow water, shelly beds (“pontilevian” facies Auct.); nearly absent Pectinidae in the shallow water Arca facies (“lublean” Auct.). Generally, the species belonging to the genus Pecten are only common in the savignean facies, in which the diversity consequently increases. Actually, the biochronological framework of the “faluns” is correct, mainly related to the mammal zonation. The associations of Pectinidae collected in the “faluns” may be of several interests.<l type="unord"><li>Several memberships of the observed faunas have a long stratigraphical range (Langhian–Pliocene), wide geographical distribution (from Britain to Mediterranean areas), and may be ecologically tolerant. They belong to the Crassadoma multistriata and Aequipecten radians species. In Western France, A. radians may be related to quite shallow environment. Opposite, the species Gigantopecten ligerianus may be related to the deepest environments.</li><li>Several species or association may success to each other through time, which may offer a regional stratigraphical interest, in the “faluns” from Western France: P. subarcuatus—P. sp. 1 (Langhian), P. sp. 2 (close to praebenedictus, Serravalian to Tortonian.), P. praebenedictus s. s. (younger Tortonien), P. jacoabeus or maximus (Messinian to Pliocene). G. ligerianus was recently recollected regionally in sediments of Langhian age only, if the local deposition environments are deep enough. Note that numerous shells belonging to this species exist in historical collections, from Doue´ area (obs. pers. M.B.).</li></l> [Copyright &y& Elsevier]