Sedimentación mixta (siliclásticoscarbonatada) en lagos someros de baja pendiente con dominio del oleaje. Un ejemplo del Mioceno de la Cuenca del Duero

Abstract

Laeustrine deposits of Tecto-Sedimentary Unit N3 (Mediavilla et al., 1996) outcropping at the centcr of the Duero River Basin contain both, siliciclastic and carbonate formations. The siliciclastic formations were deposited in floodplain (oehre sands and muds), swamp (black and green muds) and lacustrine (green sands and muds) environments, and the carbonates (marls and massive, laminated, and cross-stratified limestones) are of Iacustrine origino Sequential analysis of these deposits reveals that both were coeval and formed in a single lakc. Their occurrence was a function of the distance of the sedimentation area to the siliciclastic sources. This model is ao altemative to their interpretation as an alternation of lithologieally different lakes. Therefore, the sedimentary sequenee can be interpreted as paleogeographically more than climatically controlled. This alternative interpretation urges for the use of correlations based on sequential analysis more than on Iithology for the study of sllch deposits.