Michel Campy

The last glacial/interglacial record of rodent remains from the Gigny karst sequence in the French Jura used for palaeoclimatic and palaeoecological reconstructions

Abstract A multidisciplinary approach has produced an exceptional chronological log of climatic patterns for the Upper Pleistocene sequence of Gigny Cave (Jura, France) covering the Pre-Eemian, Eemian Interglacial, Middle Glacial and Upper Pleniglacial, as well as a part of the Holocene. Multivariate analysis (correspondence and component analysis) of rodent associations from the sequence is used here to characterize the different climatic stages in terms of relative temperature, plant cover and moisture. Faunal analysis establishes: (1) positive and negative correlations among the variations of the different species; (2) the significance of axis 1 (component analysis) which, in terms of temperature, opposes cold environments with contrasted continental biotopes; (3a) the significance of axis 2 (component analysis), which reflects vegetation patterns ranging from open to closed habitats; (3b) the significance of axis 3 (component analysis), which expresses trends in moisture; (4) various correlations between faunal and climatic parameters (temperature, plant cover and moisture); (5) evaluation of faunal diversity (Shannon index ranging from 0.74 to 2.27) showing that diversity increases with temperature and the complexity of vegetation, but is not sensitive to moisture. Lastly, the comparison of multivariate methods with the weighted semi-quantitative Hokr method shows the complementarity of the two approaches, the first methods quantifying climatic parameters while the second seems to provide more precise evaluations of the main seasons of rainfall.

The palaeogeography of the last two glacial episodes in France: the Alps and Jura

This chapter discusses the palaeogeography of the last two glacial episodes in Alps and Jura. Both the Jura and the Alps were covered by major glaciers during the past cold periods of the Quaternary. Nowhere in the Alps have Quaternary deposits been completely preserved. Therefore, the basic stratigraphic subdivision is combined from various regional stratigraphies, though in many cases the determination is difficult because age control is lacking. Indications of Early Quaternary cold stages have long since been reported from the Italian and French Alps. In both areas, an abrupt change from fine-grained sedimentation to the deposition of coarse gravel and conglomerates is manifested in what was regarded as the “Upper Pliocene.” However, the evidence is ambiguous. The change in sedimentary environment might either be explained by tectonic causes or by climatic changes.

Palaeogeographical relationships between Alpine and Jura glaciers during the two last Pleistocene glaciations

Abstract Two main moraine complexes are usually defined in the northwestern Alpine piedmont: the External Moraine Complex (EMC) dated to the penultimate glaciation (“Riss” sensu lato) and the Internal Moraine Complex (IMC) dated to the last glaciation (“Wurm”). Until recently the prevalent concept was that these two complexes had been built by glaciers originating in the central Alpine zone. This paper presents a new palaeogeographical diagram, based on mapping and petrographical studies of these two moraine complexes, and especially on the relationships between Alpine and Jura tills. We reach the following conclusions. 1. (1) The Jura glaciers were independent of the Alpine glaciers during the two last Pleistocene glaciations. 2. (2) The Jura Mountains formed a topographical barrier blocking and modifying the Alpine glacier advance towards the northwest, with the result that ◦ -during the Wurmian glaciation, the maximum elevation (1200 m a.s.l.) of the Alpine glaciers on the eastern margin of the Jura was too low to allow Alpine ice to enter the Jura; and ◦ -during the “Rissian” glaciation, the greater thickness of the Alpine glaciers resulted in their penetration only into the lower marginal zone of the Jura. 3. (3) Thus, in the studied area, the central Alps were not the only centre of ice dispersal during the two last Pleistocene glaciations: on the northwestern Jura slopes, the corresponding moraine complexes were mainly built by glaciers emanating from the central Jura.

Chapter 10 – Quaternary Glaciations in the French Alps and Jura

During last glacial maximum, the pre-existing relief of the Alps and the Jura Mountains controlled glacier development. The Jura massive morphology, only slightly dissected by valleys, resulted in a wide ice-sheet; and this situation contrasts with the Alps where numerous deep valleys were filled by big glaciers.

SEDIMENT YIELD FROM GLACIO-LACUSTRINE CALCAREOUS DEPOSITS DURING THE POSTGLACIAL PERIOD IN THE COMBE D'AIN (JURA, FRANCE)

The middle valley of the river Ain (Jura) cuts through glacio-lacustrine deposits laid down in an ice-dammed lake during the most recent glacial advance. The total volume eroded is about 6·21 ×10 8 m 3 for a surface area of 3·7 ×10 7 m 2 . Erosion occurred between 18 ka BP and 6 ka BP, i.e. over a duration of some 12 ka. Sediment yield from the area was of the order of 2500 t km -2 a -1 , which is comparable with modern-day sediment yield from NW African badlands. These high values are ascribed to the amenability of glacio-lacustrine deposits to mechanical weathering and to the rapid geomorphological changes that affected glacial and paraglacial sedimentary cover after the retreat of the ice. The valley slopes were destabilized by mass wasting (earthflow and mudflow), which was the predominant erosional process. The slopes are currently stabilized or very exceptionally active.

Palaeogeography of the last two glacial episodes in the Massif Central, France

This chapter discusses paleogeography of the last two glacial episodes in the Massif Central in France. As a result of the altitudinal gradient from the west to the east in the massif, different glacial systems developed. To the west the massifs of Mont-Dore, Cantal, Aubrac, and Margeride thus form a north–south orientated mountain barrier extending about 150 km, where the highest peaks reach 1400–1880 m. Glaciation was, therefore, most extensive in this region. The most widespread Pleistocene glacier system in the Massif Central is found on the Massif du Cantal. Based on well-marked frontal moraines and other traces of glaciation, paleogeographical reconstruction shows that there was an ice-cap with several outlet glaciers. The Mont-Dore Massif is only a quarter the size and is also much younger than the Cantal.

Des particules charbonneuses, témoins des variations de l'érosion chimique d'un bassin versant calcaire durant l'holocène (bassin de chaillexon, doubs, France)

Matter fluxes result from chemical and mechanical weathering that vary as a function of climate, relief, lithology and human activities. The aim of this paper is to characterize chemical weathering variations in the past using coaly particles found in both the geological substratum and the Holocene lacustrine sediments of a calcareous basin (Chaillexon lake, Doubs, France). Results point out that chemical weathering was the predominant erosional process in the watershed, which may be due to the calcareous nature of the bedrock. The significant variability of this process relative to mechanical weathering during the Holocene period can be interpreted as a consequence of the development of the vegetal cover induced by climate changes and human activity (forest clearing and landuse). Results also suggest that there is no direct relationship between chemical weathering in the watershed and autochthonous carbonate precipitation in the lake.