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摘要
Fossiliferous flint accumulations have been discovered in surface deposits at Claix, in Charente (SW France). These silicifications come both from alterites or limestones with flints, and from Palaeolithic or Neolithic habitats. A first part of the flints, beige or brown, is rich in bryozoans, pectinids and oysters Ceratostreon pliciferum Dujardin. Strongly alterated (oxydized, whitened) and scattered on large agricultural surfaces (fields, vines), they constitute relict nodules probably resulting from the secondary silicification of local shelly limestones of the Late Coniacian series during Palaeogene climatic weathering. Other silicified blocks (sandstones and flints) are devoid of oysters but very rich in plant fossils (angiosperms, conifers, and ferns). They have been observed both in sub-primary position, extracted from their alterites or limestones by plowings, and in archaeological context within Palaeolithic or Neolithic habitats. Their dating is difficult because a variable diachronism can exist between these different flints with plants, more or less anthropized. The presence of spatangoid echinoids, such as "Periaster" conicus d'Orbigny or "P." oblongus d'Orbigny in the flints bearing plants argues for a Late Turonian dating. However, the geological synthesis of the regional Cretaceous series reveals occurrences of lignitic clay or marls both in the uppermost Turonian of Dordogne and in the lowermost Coniacian of Charente. Thus, the flints with plants of Claix could come not only from in situ or relict primary silicifications of uppermost Turonian deposits but from secondary silicifications of lowermost Coniacian deposits too (Palaeogene neoformation). The flora of the Claix flints is compared to the ones of Cretaceous flints from ArchingeayLes Nouillers (Charente-Maritime) and Torsac (Charente) and from the Late Cretaceous lignitic clay of Charente, Charente-Maritime and Dordogne.
- 出版日期2016-6
