Jean-Pierre Suc

Evolution of the Messinian Mediterranean environments: the Tripoli Formation at Capodarso (Sicily, Italy)

Abstract New field data have been collected from the Capodarso section (Caltanissetta basin, Sicily); 48 samples from the Tripoli Formation were analysed for foraminifera, dinocysts, palynofacies, CaCO 3 , pollen grains and clay minerals. The uppermost clays of the Terravecchia Formation are clearly the result of deeper deposition than those corresponding to the lowermost analysed samples within the overlying Tripoli Formation. So, the general evolution of the basin was from normal marine conditions to confinement, during which the sedimentation of diatomite vs. clay was mainly controlled by relative sea-level changes. Three successive types of processes are considered to have generated the diatomites: 1. (1) in the lower part of the section, the sea level was relatively high and deposition of diatomites was aided by sea-level rises of unequal importance and variations of continental precipitations and run-off; 2. (2) then, relatively minor sea-level oscillations prevailed; however, the second part of the sequence is characterized by a generally strong shallowing trend leading to basin confinement; 3. (3) the explanation for diatomites during the last member does not rely as much on the occurrence of substantial sea-level rises in an increasingly desiccated basin; on the other hand, an increased number of rivers reached the central area of the basin, which helped to produce the youngest diatomites. The warm (subtropical to tropical) and xeric climate predisposed to such an evolution, inducing continuous high salt-concentration of marine waters; so, the smallest influx of less saline (oceanic) waters and/or continental freshwater (run-off) could produce water-mass stratification and diatomite deposition. However, not all lithologic breaks are likely to correspond to recorded environmental transitions. Bio- and magnetostratigraphy of the section allow consistent relationships between the sea-level curve at Capodarso and the δ 18 O curve at Site 588 (southwest Pacific), attesting global eustatic control on the sedimentation of the Caltanissetta basin up to the beginning of the Messinian salinity crisis.

Transport of bisaccate coniferous fossil pollen grains to coastal sediments: An example from the earliest Pliocene Orb ria (Languedoc, southern France)

Abstract The detailed palaeogeographic and stratigraphic knowledge of the earliest Pliocene Orb ria permits a good understanding of pollen sedimentation, especially of bisaccate coniferous pollen, with reference both to the plant distribution and to pollen dispersal factors. In such a coastal sedimentary situation that is entirely dependent in river action, bisaccate coniferous pollen — generally connsidered to be favoured by aerial transport — are predominantly carried by fluvial activity and transferred to the marine currents.

Modern pollen deposition in the Rhone delta area (Lagoonal and marine sediments), France

The investigation identifies the two main types of pollen sedimentation in the Rhone delta, and presents synthetic pollen spectra in terms of ecological groups in order to predict the pollen source areas. Two different domains are studied: the lagoonal zone occupied by the Vaccares where atmospheric pollen imput predominates and the Rhone mouth area (river delta and prodelta) where fluvial pollen influx prevails. The reflection of local and regional vegetation in the surface sediment pollen spectra is carefully discussed with reference to atmospheric pollen records and to water sample analyses. This work is designed to help the interpretation of past pollen spectra and paleovegetation and through them also paleoclimate reconstructions.

TOWARDS THE LOWERING OF THE PLIOCENE/PLEISTOCENE BOUNDARY TO THE GAUSS-MATUYAMA REVERSAL

Abstract The present Pliocene/Pleistocene boundary is at the top of the Olduvai normal subchron. Many data now favour the lowering of the Pliocene/Pleistocene boundary to the Gauss-Matuyama reversal. This affords an opportunity to give to the boundary a more global significance in keeping with recent evidence.

Pollen Record of the Saint-macaire Maar (herault, Southern France) - a Lower Pleistocene Glacial Phase in the Languedoc Coastal-plain

The age of the Saint-Macaire maar sediment, in the northwest Mediterranean coastal plain, is between 1.4 and about 0.7 Ma. The pollen diagrams indicate an open xeric vegetation (steppe). The moderate percentages of thermophilous trees support the hypothesis of vegetation refugia along the north Mediterranean shoreline as far back as Early Pleistocene.

High resolution climate and vegetation simulations of the Mid-Pliocene, a model-data comparison over western Europe and the Mediterranean region

Here we perform a detailed comparison between climate model results and climate reconstructions in western Europe and the Mediterranean area for the mid-Piacenzian warm interval ( ca 3 Myr ago) of the Late Pliocene epoch. This region is particularly well suited for such a comparison as several quantitative climate estimates from local pollen records are available. They show evidence for temperatures significantly warmer than today over the whole area, mean annual precipitation higher in northwestern Europe and equivalent to modern values in its southwestern part. To improve our comparison, we have performed high resolution simulations of the mid-Piacenzian climate using the LMDz atmospheric general circulation model (AGCM) with a stretched grid which allows a finer resolution over Europe. In a first step, we applied the PRISM2 (Pliocene Research, Interpretation, and Synoptic Mapping) boundary conditions except that we used modern terrestrial vegetation. Second, we simulated the vegetation for this period by forcing the ORCHIDEE (Organizing Carbon and Hydrology in Dynamic Ecosystems) dynamic global vegetation model (DGVM) with the climatic outputs from the AGCM. We then supplied this simulated terrestrial vegetation cover as an additional boundary condition in a second AGCM run. This gives us the opportunity to investigate the model’s sensitivity to the simulated vegetation changes in a global warming context. Correspondence to: A. Jost (anne.jost@upmc.fr) Model results and data show a great consistency for mean annual temperatures, indicating increases by up to 4 C in the study area, and some disparities, in particular in the northern Mediterranean sector, as regards winter and summer temperatures. Similar continental mean annual precipitation and moisture patterns are predicted by the model, which broadly underestimates the wetter conditions indicated by the data in northwestern Europe. The biogeophysical effects due to the changes in vegetation simulated by ORCHIDEE are weak, both in terms of the hydrological cycle and of the temperatures, at the regional scale of the European and Mediterranean mid-latitudes. In particular, they do not contribute to improve the model-data comparison. Their main influence concerns seasonal temperatures, with a decrease of the temperatures of the warmest month, and an overall reduction of the intensity of the continental hydrological cycle.