G.C. Foster

The Tabernas alluvial fan and lake system, southeast Spain: applications of mineral magnetic and pedogenic iron oxide analyses towards clarifying the Quaternary sediment sequences

Abstract Mineral magnetic and soil iron oxide data are applied to questions of relative age correlation of alluvial fans and lake sediments in the Tabernas basin, southeast Spain, within a context of interaction between tectonics and climatic change. Within the Tabernas basin, the sediment sequences and morphological evolution of late Quaternary alluvial fans suggest climatic change as the primary control. The fans toe out at the upper margins of a former lake, created in response to tectonic uplift. Magnetic and iron oxide data from soils, particularly dithionite-extractable iron (Fe d ), and frequency-dependent magnetic susceptibility ( χ FD %) accord with the relative age relationships suggested by more conventional field-based geomorphic observations. Magnetic data from the lake sediments suggest the main provenance characteristics of the sediments, but also reveal a shift in sediment sources towards the end of the lake period (probably during the late Pleistocene) to sediment supplied from a more active fluvial system from soil erosion within the Sierra de los Filabres part of the catchment. Hence, although the locations of the fans and the existence of the lake relate primarily to tectonics, the fan sequences themselves appear to be primarily climatically controlled, and there is evidence of a climatic influence over the source of sediment input into the lake during the late Pleistocene.

Forestry and flooding in the Annecy Petit Lac Catchment, Haute-Savoie 1700-2000

Upland environments are particularly vulnerable to the stresses of climate change. The strength and persistence of such forces are not easy to measure and hence comparison of climate impacts with anthropogenic impacts has remained problematic. This paper attempts to demonstrate the nature of human impact on forest cover and flooding in the Annecy Petit Lac Catchment in pre-Alpine Haute Savoie, France, between 1730 and 2000. Local documentary sources and a pollen record provided a detailed history of forest cover and management, making it possible to plot changes in forest cover against local and regional precipitation records, and their individual and combined impacts on flooding. A main period of large-scale, uniform and rapid deforestation in the catchment was identified in the early nineteenth century, but sub-catchment patterns of refor estation and regeneration have varied up to the present. The period of deforesta tion was accompanied by demographic expansion and regional scale exogenous forces, such as small scale industrial development, foreign occupation, war, caveats and laws, acting alongside local scale endogenous forces and land fragmentation, agricultural crisis, and the desire for pasture. These all produced conflict between individual needs and those of communities and resulted in localised changes in forest cover. Joint phases of deforestation and flooding are more evident in individual second order tributaries than the whole catchment, but there appears to be no obvious or simple causal link between forest cover change, climate anomalies and flooding. Environment and History 8 (2002): 403-28 ? 2002 The White Horse Press, Cambridge, UK. This content downloaded from 157.55.39.110 on Tue, 20 Sep 2016 06:19:28 UTC All use subject to http://about.jstor.org/terms 404 D.S. CROOK et al.