Une remarquable association d’otolithes de poissons dans le Miocène moyen de Sos, Matilon (France, Lot-et-Garonne).A remarkable assemblage of fish otoliths from the Middle Miocene of Sos, Matilon (France, Lot-et-Garonne)

The Serravallian site of Sos (Matilon, base of the section) is located near to the shore of the gulf of eastern Aquitaine. The studied sediment is a near shore coquina facies with a well-preserved and diversified marine fauna, reflecting a bay environment, with some brackish influences. Otoliths of 22 teleost taxa were identified, two of them representing new species: Afroscion rezeaui and “genus aff. Afroscion” carinatus. The association is characterised by a strong dominance of sciaenids (83% of the total number of otoliths). Among the remaining taxa, Pomadasys aff. incisus and a Gobius (elongate form) account for respectively 3% and 12%; all remaining taxa are rare. Except for the Serravallian coquinas of Orthez and Sallespisse, sciaenid otoliths are very rare in all Oligo-Miocene sampling sites of Aquitaine. Sciaenids from Sos, where Afroscion rezeaui and Sciaena irregularis dominate, are different from those of Orthez and Sallespisse, dominated by Umbrina pyrenaica. Only Argyrosomus regius is common to both associations. In total, only seven species are common to the two localities, and the sparid Dentex aff. maroccanus is lacking at Sos. The two faunas seem to correspond to quite different environments. Sciaenids are quite tolerant for fresh water, and the Sos area could be near to a stream mouth at the end of the gulf. Some sciaenids are even partly freshwater fishes. At Orthez – Sallespisse, the represented sciaenids are very near shore forms, but of normal salinity: this is attested by the frequence of Dentex aff. maroccanus and several haemulids. At Mios, another rich otolith site located more to the north, otoliths essentially belong to typical marine near shore fishes, among which there are even some gadids, a family of more northern fishes; sciaenids are very rare there. Here also, environmental differences are apparently responsible for the differences among the associations

Why Family Farms Are Increasingly Using Wage Labour?

In many developed countries, the share of wage employment out of the total agricultural labour force has been increasing for the last ten years. Using data from French agricultural censuses, we present an analysis of the factors that influence households' decisions about whether to work on the family farm or to work outside, and about the use of wage labour. Studying how the effects of these factors have varied between 1988 and 2000 enables us to highlight the different mechanisms that have led to an increase in permanent wage employment during that period. In particular, we show that family labour and permanent wage labour have become nearly equivalent in 2000, whereas that was not the case in 1988.agricultural employees, farms, family labour, Labor and Human Capital, C34, C35, J22, J43,

Nouvelles données sur le Miocène moyen marin ("Sallomacien") de Gironde (Bassin d'Aquitaine-France) Approche des paléoenvironnements New data about the maine Middle Miocene ("Sallomacian") of Gironde (Aquitaine Basin); paleoecological outline

The Mid Miocene marine formations of Salles area (former "Sallomacian" stage) have been studied again from numerous outcrops and cores. The deep structural framework influences notably of the characteristics and distribution of the deposits, which are neritic. The stratigraphy is stated precisely thanks to the planktonic fauna and floradetailed examination (probably Serravallian zones NN6 - N12). Several paleobiofacies are reconstituted from the rich invertebrate faunas, which give also paleoclimatic data

Etude de populations de Glycymeris (Bivalvia, Glycymerididae) du Miocène d'Aquitaine, Sud-Ouest de la France Studyof Glycymeris (Bivalvia, G1ycymerididae) populations from the Aquitaine Miocene, SW France

Abundant crops of Glycymeris have been made in the neritic bioclastic deposits of the Aquitaine Basin. After an outline about the Chattian taxa, the 5 Lower Miocene lineages are presented; G. cor is plainly predominant. Then, the Middle Miocene faunas are also detaiIed, G. inflatus and G. bimaculatus being the most frequent taxa. A test of biometrical analysis about the G. cor species is presented

Les faunes de coraux (Anthozoaires Scléractiniaires) de la façade atlantique française au Chattien et au Miocène

The study of new abundant coral crops and a systematic revision of the historie collections allow us to extend significantly the data about the Upper Oligocene and Miocene Scleractinia of the French atlantic basins. The SW and W-NW France faunas have been considered, and complete lists of the different defined taxa are presented. The general lines of the evolution of this group are specified, and linked to the paleoclimatic and paleobiogeographic changes

Progrès récents dans la connaissance des gisements cénozoïques en Aquitaine méridionale (Challose, Béarn et Bas-Adour; SW France)

The present paper presents the guide book of the excursion of the « Groupe d'Etude du Paleogene» in southern Aquitaine (4-6 september 2000), organized by the authors. Numerous Paleogene sections are discussed. Several of them were never described in detail previously: various sections on the Lespontes river at Saint-Lon-Ies-Mines (Middle and Upper Eocene), others on the road from Gan to Rebenacq (Paleocene-Ypresian), in the Gan area (Ypresian) and at Lahosse (Rupelian). Several classic sites are also presented and updated. Special attention has been given to the fIlling of the Saubrigues paleocanyon, with deposits ranging from Chattian to Langhian age. The stratigraphy of all studied levels is detailed with calcareous nannoplankton analyses, and for several sections, paleoecological data based on the analysis of fish otoliths and microbenthos (foraminifers, ostracods) are presented. This provides a series of southern Aquitaine reference localities for any complementary study. Moreover, these localities are well calibrated in time and exemplify the wide variety of facies that can be observed in the marine sedimentation realm of this region

Non-linear spectroscopy of rubidium: An undergraduate experiment

In this paper, we describe two complementary non-linear spectroscopy methods which both allow to achieve Doppler-free spectra of atomic gases. First, saturated absorption spectroscopy is used to investigate the structure of the $5{\rm S}_{1/2}\to 5{\rm P}_{3/2}$ transition in rubidium. Using a slightly modified experimental setup, Doppler-free two-photon absorption spectroscopy is then performed on the $5{\rm S}_{1/2}\to 5{\rm D}_{5/2}$ transition in rubidium, leading to accurate measurements of the hyperfine structure of the $5{\rm D}_{5/2}$ energy level. In addition, electric dipole selection rules of the two-photon transition are investigated, first by modifying the polarization of the excitation laser, and then by measuring two-photon absorption spectra when a magnetic field is applied close to the rubidium vapor. All experiments are performed with the same grating-feedback laser diode, providing an opportunity to compare different high resolution spectroscopy methods using a single experimental setup. Such experiments may acquaint students with quantum mechanics selection rules, atomic spectra and Zeeman effect.Comment: 16 pages, 8 figure

Etude de populations de Glycymeris (Bivalvia, Glycymerididae) du Miocène d'Aquitaine, Sud-Ouest de la France

Abundant crops of Glycymeris have been made in the neritic bioclastic deposits of the Aquitaine Basin. After an outline about the Chattian taxa, the 5 Lower Miocene lineages are presented; G. cor is plainly predominant. Then, the Middle Miocene faunas are also detaiIed, G. inflatus and G. bimaculatus being the most frequent taxa. A test of biometrical analysis about the G. cor species is presented

Instability driven fragmentation of nanoscale fractal islands

Formation and evolution of fragmentation instabilities in fractal islands, obtained by deposition of silver clusters on graphite, are studied. The fragmentation dynamics and subsequent relaxation to the equilibrium shapes are controlled by the deposition conditions and cluster composition. Sharing common features with other materials' breakup phenomena, the fragmentation instability is governed by the length-to-width ratio of the fractal arms.Comment: 5 pages, 3 figures, Physical Review Letters in pres

Palaeontological data about the climatic trends from Chattian to present along the Northeastern Atlantic frontage

Climatic changes that affected the Northeastern Atlantic frontage are analyzed on the basis of the evolution of faunas and floras from the late Oligocene onwards. The study deals with calcareous nannoplankton, marine micro- and macrofaunas, some terrestrial vertebrates and vegetal assemblages. The climate, first tropical, underwent a progressive cooling (North-South thermic gradient). Notable climatic deteriorations (withdrawal towards the South or disappearance of taxa indicative of warm climate and appearance of "cold" taxa) are evidenced mainly during the Middle Miocene and the late Pliocene. Faunas and floras of modern pattern have regained, after the Pleistocene glaciations, a new climatic ranging of a temperate type in the northern part