Depósitos de ápice de abanico (Terciario de la Cuenca del Tajo, Madrid): sedimentología y controles sedimentarios

Abstract

The topmost alluvial deposits that outcrop adjacent to Central System igneous rocks are arranged in two units with particular internal architecture. The lower unit consists of ten bodies laterally disposed and bounded by concave erosional surfaces. These bodies record both viscous and f1uidized flows corresponding to channelized debris-flows, torrential flows and single channel fluvial deposits. This unit is interpreted as entrenched deposits at the head of the fan at the outlet of the catchment area. The c1ast-supported gravel and boulder upper unit is arranged in near tabular bodies with erosional bases and internal smaller, single channels and records the final stages of fan development when apex trench was buried and sheet-flows developed. Lateral migration of bodies in both units record a stable tectonic setting and a slowly-rising or near-equilibrium base-level, interpreted as the final stages of fan development in a almost-filled basin.