Polyphasic hydrothermal and meteoric fluid regimes during the growth of a segmented fault involving crystalline and carbonate rocks (Barcelona Plain,NE Spain)

A polyphasic tectonic‐fluid system of a fault that involves crystalline and carbonate rocks (Hospital fault, Barcelona Plain) has been inferred from regional to thin section scale observations combined with geochemical analyses. Cathodoluminescence, microprobe analyses and stable isotopy in fracture‐related cements record the circulation of successive alternations of hydrothermal and low‐temperature meteoric fluids linked with three main regional tectonic events. The first event corresponds to the Mesozoic extension, which had two rifting stages, and it is characterized by the independent tectonic activity of two fault segments, namely southern and northern Hospital fault segments. During the Late Permian‐Middle Jurassic rifting, these segments controlled the thickness and distribution of the Triassic sediments. Also, dolomitization was produced in an early stage by Triassic seawater at shallow conditions. During increasing burial, formation of fractures and their dolomite‐related cements took place. Fault activity during the Middle Jurassic–Late Cretaceous rifting was localized in the southern segment, and it was characterized by hydrothermal brines, with temperatures over 180°C, which ascended through this fault segment precipitating quartz, chlorite, and calcite. The second event corresponds to the Paleogene compression (Chattian), which produced exhumation, folding and erosion, favouring the percolation of low‐temperature meteoric fluids which produced the calcitization of the dolostones and of the dolomite cements. The third event is linked with the Neogene extension, where three stages have been identified. During the syn‐rift stage, the southern segment of the Hospital fault grew by tip propagation. In the relay zone, hydrothermal brines with temperature around 140°C upflowed. During the late postrift, the Hospital fault acted as a unique segment and deformation occurred at shallow conditions and under a low‐temperature meteoric regime. Finally, and possibly during the Messinian compression, NW‐SE strike‐slip faults offset the Hospital fault to its current configuration.     

Isotopic Composition of Lead in Copper Ores and a Copper Artefact from the La Profunda Mine (León,Spain)

This paper continues the characterization of the lead isotopic fingerprint of ancient copper mines in the north‐west of Spain. In this work, the lead isotopic compositions found in copper ores from the La Profunda mine are presented. Azurites and malachites sampled from this deposit were subjected to lead isotope analysis by multicollector ICP–MS. The results showed a clear radiogenic lead signature compatible with the presence of uranium‐rich minerals (such as zeunerite) in the same mining complex. Moreover, a rare copper artefact, found in the galleries of the mine during its modern exploitation, was also analysed and showed that local mineral was used for its manufacturing.     

Cost Efficiency,Urban Patterns and Population Density When Providing Public Infrastructure: A Stochastic Frontier Approach

Relying on stochastic frontier analysis we propose a methodology to study the technological characteristics and cost efficiency levels related to the provision of public infrastructure for basic utilities. The methodology assumes a cost minimizing behaviour on the part of public officials when planning the construction of local infrastructure, which is represented by way of a flexible translog cost function. Introducing relevant definitions of scale economies, associated with larger numbers of inhabitants and dwellings, as well as economies of density, brought about by reductions in urban dispersion, we analytically determine the optimal population densities for which average cost is minimized. We illustrate our model with the water cycle sector, including water distribution, sewage collection and cleansing of wastewater, and considering data at the municipality level for the Spanish region of Castilla y León. The obtained results indicate potential cost savings in the form of decreasing average costs, as relevant scale and density economies are present, along with large inefficiency levels. Relevant policy guidelines favouring larger and denser urban sizes are drawn, as the observed cost excess is the result of a general suboptimal urban size in terms of population density, and the negative effects of dispersed settlement patterns.     

Inter-Tidal Causeways and Platforms of the 13th- to 16th-Century City-State of Kilwa Kisiwani, Tanzania

Survey of the coastal and inter-tidal zone at Kilwa in Tanzania resulted in the discovery of a series of artificial causeways and platforms at the entrance to the harbour of Kilwa Kisiwani, an important port trading with East Africa and southern Asia from around the 13th century. These appear to be part of a phase of monumental stone building at Kilwa in the 13th to 16th centuries, and represent a prosperous, confident Kilwa, impressing foreigners arriving by sea. Although necessarily speculative, several possible interpretations of their functions are advanced including navigation, protective breakwaters, access to marine resources, or ceremonial use.
© 2007 The Author     

Rethinking Twentieth‐Century Guadalajara

This paper discusses the impact of the conference ‘Las Olvidadas: Gender and Women's History in Post‐Revolutionary Mexico’ that took place at Yale University in May 2001, into my own work on women's political mobilisations. It points out from where I departed and how it changed my perspective from women's history to gender history by focusing on women workers in the tortilla industry, a union cacicazgo (political bossism), civic culture, narratives, cultural memory and female political trajectories after the granting of women's suffrage in 1953 in Jalisco.