Influencia del substrato sobre la arquitectura y características texturales de los sistemas fluviales: Desarrollo de paleovalles y su relleno

Abstract

Oligocene sedimentation into SW border of Duero Basin (Spain) took place in a tectonically active
basin margino Close examination of these deposits and their relations to paleotopography reveals a
strong interaction between the degree of valley incision, i.e. paleovalley development, and architecture
of the deposits. Uplift of the margin basin coupled to differences in the erosionability of the substratum
of (future) river valleys led to inhomogeneus response along the river beds that resulted in
paleotopographical constraints for the inciding sedimentary systems. Hard-rocks in the substratum
conditioned the development of narrow, usually deeply-incised, paleovalleys. By contrast, cut areas
where the substratum consisted of soft rocks allowed the development of wider, shallower valleys. The
relativelly-narrow passageways cut into areas with hard substratum filled up with coarse sediments
related to hyperconcentrated flows, whereas the wider valleys cut into softer terrains contain welldifferentiated
finer-grained channel-floodplain deposits. The clase concordance between hydrological
equations and field observations confirms that textural and architectural features are strongly dependent
on the morphological setting.