Tracking sea bed topography in the Jurassic. The Lotena Group in the Sierra de la Vaca Muerta (Neuquén Basin, Argentina)

The Lotena Group is a clastic to evaporitic unit up to 650 m thick that accumulated during the Middle to Late Jurassic in the Neuquén Basin, western Argentina. Extensive field work carried out in the Sierra de la Vaca Muerta and Arroyo Covunco areas, including the measurement of seven detailed stratigraphic sections and geo- logical mapping allow the discrimination of six unconformity-bounded units or sequences. The first sequence is composed of red beds and evaporites belonging to the Tábanos Formation that unconformably overlies strata of the Lower to Middle Jurassic Cuyo Group. Sequences 2 to 5 are shallow marine and display a basal sandstone interval attributed to confined shelfal sandstone lobes. These grade vertically into unconfined shelfal sandstone lobes, and terminate with carbonate deposits. The basal interval is restricted to the thickest areas of each sequence, a relationship attributed to structural relief. Sequence 6 has a very irregular shape and strongly trun- cates the underlying deposits. It is composed almost entirely of massive carbonate strata that were deposited by density currents. Facies analysis and stratigraphic mapping suggest periodic recycling of previous accumula- tions. Stratigraphic evidence suggests that the Lotena Group in the Sierra de la Vaca Muerta and adjacent areas probably accumulated over a tectonically unstable basement. Sequences 1, 2 and 3 display evidence of accumu- lation in an extensional tectonic setting, while sequences 4, 5 and 6 experienced a northward shift of their depocentres associated with extensive erosional truncation of the marginal areas, suggesting that accumulation was affected by early stages of growth of the Covunco anticline.Fil: Zavala, Carlos Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; Argentin

A political sociology of adult education : a research agenda

With the publication of the Southam Report in Canada (1987) showing the widespread functional illiteracy of vast sectors of the Canadian population, and the renewed discussion on the shortcomings of literacy training programmes in the U.S. (Kozol, 1985; Gee, 1986), adult education has become again a priority for policy makers in industrial advanced societies. This article challenges some of the bask assumptions of conventional mainstream adult education, taking advantage of the experience and theories mainly developed in dependent-development societies of Latin America. A political sociology of adult education takes as a starting point the relationships between the capitalist state and adult education. Therefore, the notion of the State should be considered central to any attempt to understand the "new" rationale for policy formation in this field. Some questions and queries on adult education policy formation are advanced here, and a new agenda for research is advocated.peer-reviewe

Exchange Rate Policy Credibility in Mexico, 1991-1994

An econometric examination of interest rate differentials reveals the existence of a significant relationship between the level of exchange rate policy credibility in Mexico during 1991-1994, and the country’s macroeconomic performance, the central bank international reserves and the NAFTA ratification. Interestingly, a steady fall in manufactures output growth tended to improve credibility, which suggests the existence of gains in the government’s disinflationary reputation. Additionally, it is argued that downward pressure on the domestic peso-dollar interest differential came from the exchange rate debt indexation of 1994 and the opening of the domestic bond market to foreign investment in December 1990.

Convergent flow in a two-layer system and mountain building

With the purpose of modelling the process of mountain building, we investigate the evolution of the ridge produced by the convergent motion of a system consisting of two layers of liquids that differ in density and viscosity to simulate the crust and the upper mantle that form a lithospheric plate. We assume that the motion is driven by basal traction. Assuming isostasy, we derive a nonlinear differential equation for the evolution of the thickness of the crust. We solve this equation numerically to obtain the profile of the range. We find an approximate self-similar solution that describes reasonably well the process and predicts simple scaling laws for the height and width of the range as well as the shape of the transversal profile. We compare the theoretical results with the profiles of real mountain belts and find and excellent agreement.Comment: Accepted by Physics of Fluid