Formaciones tobáceas holocenas y evolución reciente del Valle del río Purón (Alava-Burgos)

Zusammenfassung

Tufa deposits are environmental and geomorphologic indicators of the evolution of fluvial dynamic in karstic regions. The study of the morphological characteristics of these deposits and their facies, give useful information about climatic conditions in which they were built up. Geomorphologic analysis of tufa deposits in the Puron river basin, south Álava-Burgos, has permitted to establish a geomorphological evolution of this area for recent Quaternary times, Upper Pleistocene and Holocene. Five principal stages are defined for this area since Upper Pleistocene to actuality, guided by changes in climatic conditions, there are three incision phases, one of scree deposits formation generated under cold conditions and one main phase of tufa sedimentation corresponding to early Holocene. After these, this sedimentation goes down and the downcutting o f valleys begins, modelling tufa terraces, as we can see today. In this process human pressure and ambiental factors play an important role. Nowadays, carbonate sedimentation continues, although just in refuge sites and low rates.