Données nouvelles sur l'origine du litage des grèzes. Implications paléoclimatiques

Quaternaire 5(1), 41-46, 1994

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Comptes Rendus Geoscience, 2004

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QUATERNARY GLACIATIONS IN THE EASTERN PYRENEES (ARIÈGE): HISTORIOGRAPHICAL APPROACH, NEW PALEOGEOGRAPHICAL AND CHRONOLOGICAL DATA This study examines the evidence for Pleistocene glacier extent in the north-central Pyrenees from three perspectives: the history of scientific ideas, the e volution of geomorphological research methods, and recent progress in the reconstruction of Pyre- nean palaeoenvironments. From Albrecht Penck (1883) to François Taillefer (1985) we first pro vide an overview of one century of field in vestigations into the glacial palaeogeography of the Ariège catchment. We show how the initial adoption of Penck & Brückner’s Alpine model involving multiple glaciations was soon replaced by a rival monoglacialist theory, which has cast a lasting shadow over attempts at producing an objective chronology of Pleistocene glaciations. Our focus on research methods emphasizes the great importance of geomorphological mapping. This is because the synoptic examination of landform assemblages assists in establishing a relative chronology of ice movement across each part of the landscape, and dictates the sampling strategy required for direct radiometric dating of landform sequences. Based on these methods it has been possible to reconstruct past Pyrenean environ- ments in more detail than previously achieved. Six stades of Würmian and earlier glaciations have now been established based on a population of 37 in situ-produced 10 Be nuclide samples collected from the extent ice-marginal landforms generated by the Ariège outlet glacier and its tributaries. Partly based on sharp contrasts in glacial sediment weathering intensities, results reveal that a ante- MIS 5e valley glacier extended beyond the outermost Würmian terminal moraine. The age of the Würmian maximum ice extent is shown to correlate with Marine Isotope Stage 4 (MIS 4), and the ice front underwent fluctuations of several kilometres during MIS 3. The Global LGM is recorded as the last substantial glacier readvance although the ice front did not quite reach its MIS 4 maximum. Rapid meltback ensued, with glacier fronts during the Oldest Dryas occurring in the upper valleys of both Ariège River and Suc, a tributary of the Vicdessos River.

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Quaternaire 3(1), 4-15, 1992

The micromorphological study of «grèze litée» type deposits makes it possible to better specify some processes involved in the deposition. The proposed interpretations are supported by a recent model of stratified slope deposits based on data from activ andean and alpine milieux, which emphasizes the role of the stone-banked solifluction sheets on beds differentiation. This study points out that transfers of fine particles by eluviation-illuviation play a greater role on the development of some typical features of «grèzes litées» than previously supposed on field observations. Unfrequent processes including run-off and debris flows were also determined in some exposures. The microscopic examination of «grèzes litées» confirms that depodition occured in connection with superficial freezing and thawing cycles according to the andean model, but some levels corresponding to deep freezing or permafrost were recognized in many quarries.

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Revue belge de Philologie et d'Histoire, 98, 2020

In the present contribution, we propose a rereading and commentary on the accounting of the epistates of Didymus, in particular Rehm N.41 = Haussoullier N.39 = SEG 4.453, from the point of vue of the technology of displacement and transport of the architectural blocks, from the quarry of Grion to Didymeion. One of us (P.P.) had endeavoured to identify and understand the functioning of the amphiprumnoi boats mentioned in the inscription, proposing a new interpretation in terms of towed barges.

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Riscuri şi Catastrofe

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