Bernard Clément

Paleogeographic and paleotectonic implications of clay mineral distribution in late Jurassic-early Cretaceous sediments of the Pindos-Olonos and Beotian Basins, Greece

Abstract A new method is proposed for solving the controversial problem of the location of oceanic areas from which the Pindos and Othrys ophiolites originated. Assuming that clay fractions, quickly disseminated over large areas, may be reliable markers of erosional processes, we studied these fractions in sediments from two “external” basins (Pindos-Olonos and Beotian) located between the main carbonate platforms of the Greek Hellenids. Chronologically, two different clay associations can be distinguished in the sedimentary sequences of the basins. The lower one is dominated by illite and subregular illite-smectite mixed-layers and poor in Mg, Ni and Cr; this association is consistent with common continental sources. The upper one, appearing in late Tithonian synchroneously in both basins, consists of trioctahedral smectite (saponite type) enriched in Fe, Mg, Ni and Cr; they are considered to be derived from weathered ophiolites. Thus, the beginning of the ophiolite detrital sedimentation, accepted as being middle to late Bathonian in the basinal sequences of the Maliac or Othrys zone from Hydra or lower-middle Oxfordian in all the internal units in the Argolis Peninsula, is much younger (late Tithonian) in the external basins. Such a diachronism is not consistent with a model postulating initial ophiolite displacements within the Pindos-Olonos basin by late Jurassic time. It suggests that a platform was acting as a barrier between the site of the ophiolite first intra-oceanic deformation and the “external” basins. This barrier cannot be the Parnassus platform that kept subsiding in neritic environments until late Cretaceous inside the “external” basins; it is likely to be the Pelagonian platform, positively known to have been submerged during the Tithonian. Consequently, we conclude that there was no genetic relationships between the “external” basins (Pindos-Olonos basin in a broad sense) and the “Pindos ophiolites” of which the zone of origin is to be located on the opposite eastern “internal” side of the Pelagonian platform.

Découverte de turbidites du Crétacé supérieur métamorphisées au contact d'intrusions d'ophites dans les Pyrénées occidentales (vallée d'Aspe, France). Vers une révision de l'âge des ophites pyrénéennes

Abstract On the French side of the Pyrenees, in the Bedous area of the Aspe Valley, fine-grained turbidites classically dated as Carboniferous and Triassic are attributed to the Upper Cretaceous. They contain fucoids and Globotruncanidae assemblages of the Dicarinella concavata Zone (Upper Turonian–Lower Santonian) and are metamorphosed at the contact of ophites intrusions. This discovery implies a new interpretation of the regional stratigraphy and palaeogeography. Moreover, it questions the age of the ophites emplacement in the region as well as the structural relationships between the ‘Bedous basin’ and the North Pyrenean Zone to the north and the Palaeozoic High Chain to the south. To cite this article: C. Desreumaux et al., C. R. Geoscience 334 (2002) 197–203.

Première datation des lydiennes paléozoïques dans les Hellénides internes (mont Parnis, Grèce) ; implications géologiques

Abstract Using radiolarian and conodont remains, a Tournaisian age has been obtained from the Lydian rocks (or lydites) of the Parnis Mount (Greece); this result is the first direct age dating of the Lydian rocks of continental Greece. In the same area, some limestone strata, interbedded in sandstones, yield Carboniferous and Permian foraminifers; the established stratigraphy is not consistent and so, the Lydian rocks have to be considered as blocks in an olistostrome unconformably overlain or thrusted by Triassic limestones. Otherwise, the Lydian rocks are interpreted as biogenic siliceous deposits due to the absence of carbonate sedimentation (not as a high siliceous production).