Abstract

The Duero basin occupies a large area in the north-west of the Iberian Peninsula. It has an approximately quadrangular shape, and three of its four corners are the sites of distinctive sub-basins that extend outwards from the main basin. The different margins of the sub-basins and the main basin tend to have distinctive histories of tectonic and sedimentary evolution.

Introduction

The Duero Basin is the largest Cenozoic basin in Spain with a surface area of almost 50000 km2. It occupies the major part of the north-west Iberian Peninsula. High-relief mountains composed of igneous and metamorphic rocks of Paleozoic age (mainly to the south and west) and siliciclastic and carbonate rocks of Mesozoic age (mainly to the east) bound the basin (Fig. 1). These borders formed during the Alpine Orogeny and played an important role in the geodynamic evolution of the basin.

The roughly quadrangular basin extends into three relatively narrow basins protruding near the corners (Fig. 1).

• – The Ciudad Rodrigo Basin, in the south-western corner, is a half-graben oriented NE–SW that penetrates south-westerly into the Hercynic Massif. Its sedimentary record consists mainly of Paleogene deposits, although no Early Paleogene deposits have been found so far.

• – The Almazán Basin is a complex area that extends to the east between the Iberian Range and the Central System. It was filled by siliciclastic and carbonate sediments, along with some rare evaporites, of Paleogene and Neogene age.

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