The Old and the New: Qualifying City Systems in the World with Classical Models and New Data

Zipf's rank‐size rule, lognormal distribution, and Gibrat's urban growth models are considered as summarizing fundamental properties of systems of cities. In this article, they are used as statistical benchmarks for comparing the shapes of urban hierarchies and evolutionary trends of seven systems of cities in the world including BRICS, Europe, and United States. In order to provide conclusions that avoid the pitfalls of too small samples or uncontrolled urban definitions, these models are tested on some 20,000 urban units whose geographically significant delineations were harmonized in each country over 50 years between 1960 and 2010. As a result, if the models appear not always statistically valid, their usefulness is confirmed since the observed deviations from empirical data remain limited and can often be interpreted from the geohistorical context of urbanism proper to each world region. Moreover, the article provides new free software which authorizes the reproducibility of our experiments with our data bases as well as with complementary data.     

The Late Upper Palaeolithic Occupation of the Moroccan Northwest Maghreb During the Last Glacial Maximum

New work at Kehf el Hammar Cave provides the first well-dated palaeoenvironmental sequence for the Late Upper Palaeolithic in this region of the northwest Maghreb. The archaeological layers are dated via a combination of AMS radiocarbon and luminescence dating methods. The sequence contains charcoal-rich occupation layers with faunal, human and lithic finds. Local vegetational patterns are reconstructed on the basis of preliminary analysis of the charcoal evidence. Using standard calibration curves the AMS radiocarbon dates are compared with proxy evidence for climatic change from sea core records in the Alborán Sea. These appear to show that the Late Upper Palaeolithic occupation of the region coincides closely with Heinrich Event 1, a period marked by intense aridification and dating to ca. 16,700–17,250 calendar years ago.Les nouvelles recherches dans la grotte de Kehf el Hammar ont permis d’obtenir la première séquence paléoenevironnementale bien datée du Paléolithique supérieur tardif au Nord Ouest du Maghreb. En effet, les niveaux archéologiques ont été datés par le radiocarbone par accélérateur (AMS) et des méthodes radiométriques basées sur la luminescence. En revanche, les paléoenvironnements végétaux ont été partiellement reconstitués à base des premières analyses des charbons de bois. Les dates AMS calibrées ont été comparées aux données climatiques issues des carottes marines dans la mer Alborán. Ainsi, les occupations humaines du Paléolithique supérieur tardif dans la région ont sensiblement coïncidé avec l’événement climatique Heinrich 1. Celui-ci correspond à une période qui a été marquée par une aridification intense entre 16.700 et 17.250 ans (cal.).     

Ultrathin sectioning techniques

Epoxy mixtures incorporating Araldite available in Australia have been used to embed Recent organisms, fossils and sedimentary rocks. Resultant sections of embedded material may be less than 10 micrometres thick and give increased resolution of fine structures. Mixtures used and sectioning techniques are described.