Correlation between the Paleogene detritic facies in the margins of the Tajo and Duero basins (Central Spain) : mineralogical, sedimentological and geomorphological characteristics

In the marginal deposits (Uppermost Senonian ?-Paleogene) of the Tajo and Duero basins two depo-sitional sequences with different sedimentological as well as mineralogical characteristics have been established. The "First Depositional Sequence" represents a prograding transition from distal to proximal braided systems and the characteristic clay minerals are kaolinite and smectite. The "Second Depositional Sequence" represents an evolution from proximal to medial parts of arid and semiarid alluvial fans. During the "First Depositional Sequence" climate was initially warm and wet, progressively changing towards more arid conditions with seasonal fluctuations triggering ferruginous soil development. A drastic climatic change to pronounced arid conditions took place during the "Second Depositional Sequence" and an important development of duricrusts (calcretes, silcretes and "palycretes" ) is the main feature of these deposits.Rodas M., Garzon M. G., Luque F.J., Mas R. Correlation between the Paleogene detritic facies in the margins of the Tajo and Duero basins (Central Spain) : mineralogical, sedimentological and geomorphological characteristics. In: Proceedings of the 9th international Clay Conference, Strasbourg, 1989. Vol IV : Clays in sediments. Diagenesis and hydrothermalism. Strasbourg : Institut de Géologie – Université Louis-Pasteur, 1990. pp. 43-52. (Sciences Géologiques. Mémoire, 88