El Mioceno del borde meridional del corredor Aranda de Duero-Burgo de Osma (SE Cuenca del Duero)

Resumen

This work deals with the stratigraphic and sedimentological characteristics of the Miocene succession in the southeastern Duero Basin, between the southern border of the Ayllon Range and the Duero river. The sedimentary record has been divided into two sequences: the Lower Páramo Sequence and the Upper Páramo Sequence separated by a local discontinuity surface. The limestone levels that constitute the uppermost parts of both sequences produce extensive platforms, known as «páramos» which are named the Lower Páramo and Upper Páramo Limestones. These two sequences are very similar and contain siliciclastic and calcareous sediments, which represent deposition in proximal and distal alluvial fans, as well as fluvial and lacustrine-palustrine sedimentary environments. The alluvial fans of the first sequence are strongly related to the tectonic activity along the southern edge of the Duero Basin. The fluvial system had a westward flow direction; lacustrine systems developed at final stages of the Upper and Lower Páramo successions and they onlap the southern border of the basin. Fossil localities constrain the cronostratigraphy of the Upper and Lower Páramo Sequences between the middle Aragonian (MN 5) to lower Vallesian (MN 9). New mapping indicates that the Piquera de San Esteban mammal site is located stratigrahically on top of the Lower Páramo Sequence and forms the base of the Upper Páramo Sequence.