High-resolution estimates of rates of depositional processes from an alluvial fan succession in the Miocene of the Ebro Basin, northern Spain
Gary Nichols, 2018. "High-resolution estimates of rates of depositional processes from an alluvial fan succession in the Miocene of the Ebro Basin, northern Spain", Geology and Geomorphology of Alluvial and Fluvial Fans: Terrestrial and Planetary Perspectives, D. Ventra, L. E. Clarke
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Obtaining estimates of the rates of sedimentation and frequency of depositional events at high resolution from pre-Quaternary successions is rarely possible, particularly in coarse-grained clastic successions of continental basin margins. In the Miocene strata of the Ebro Basin, northern Spain, basin-marginal deposits interpreted as the products of alluvial fans are part of the continuous aggradational fill of a basin of internal drainage. A palaeomagnetic reversal stratigraphy has been established in basin-centre sediments and correlation across to the basin margin makes it possible to estimate the rate of aggradation within the fan successions to be 90 mm ka−1. The deposits of one alluvial fan near the village of Linás de Marcuello have been analysed in the context of these rates to provide estimates of the frequency of depositional events. This analysis suggests that deposition on gravel bars approximately 700 mm thick in stream channel deposits occurred at intervals of 70–200 years over a 2.2 myr time period. This is the first time an estimate of the frequency of depositional events has been obtained at such high resolution from a pre-Quaternary alluvial fan succession.
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Alluvial and fluvial fans are the most widespread depositional landform bordering the margins of highland regions and actively subsiding continental basins, across a broad spectrum of tectonic and climatic settings. They are significant to the local morphodynamics of mountain regions and also to the evolution of sediment-routing systems, affecting the propagation and preservation of stratigraphic signals of environmental change over vast areas.
The volume presents case studies discussing the geology and geomorphology of alluvial and fluvial fans from both active systems and ancient ones preserved in the stratigraphic record. It brings together case studies from a range of continents, climatic and tectonic settings, some introducing innovative monitoring and analysis techniques, and it provides an overview of current debates in the field.
This volume will be of particular interest to geologists, geomorphologists, sedimentologists and the general reader with an interest in Earth science.