Tectonic evolution of the west Scotia Sea

Joint inversion of isochron and flow line data from the flanks of the extinct West Scotia Ridge spreading center yields five reconstruction rotations for times between the inception of spreading prior to chron C8 (26.5 Ma), and extinction around chron C3A (6.6–5.9 Ma). When they are placed in a regional plate circuit, the rotations predict plate motions consistent with known tectonic events at the margins of the Scotia Sea: Oligocene extension in Powell Basin; Miocene convergence in Tierra del Fuego and at the North Scotia Ridge; and Miocene transpression at the Shackleton Fracture Zone. The inversion results are consistent with a spreading history involving only two plates, at rates similar to those between the enclosing South America and Antarctica plates after chron C5C (16.7 Ma), but that were faster beforehand. The spreading rate drop accompanies inception of the East Scotia Ridge back-arc spreading center, which may therefore have assumed the role of the West Scotia Ridge in accommodating eastward motion of the trench at the eastern boundary of the Scotia Sea. This interpretation is most easily incorporated into a model in which the basins in the central parts of the Scotia Sea had already formed by chron C8, contrary to some widely accepted interpretations, and which has significant implications for paleoceanography and paleobiogeography

Is good policy unimplementable? Reflections on the ethnography of aid policy and practice

Despite the enormous energy devoted to generating the right policy models in development, strangely little attention is given to the relationship between these models and the practices and events that they are expected to generate or legitimize. Focusing on the unfolding activities of a development project over more than ten years as it falls under different policy regimes, this article challenges the assumption that development practice is driven by policy, suggesting that the things that make for ‘good policy ’ — policy which legit-imizes and mobilizes political support — in reality make it rather unimple-mentable within its chosen institutions and regions. But although development practice is driven by a multi-layered complex of relationships and the culture of organizations rather than policy, development actors work hardest of all to maintain coherent representations of their actions as instances of authorized policy, because it is always in their interest to do so. The article places these observations within the wider context of the anthro-pology of development and reflects on the place, method and contribution of development ethnography