Origen diagenètico de cementos carbonatados en nodulos de areniscas (Plioceno de Lebrija, Sevilla)

Abstract

The origin of carbonate cements of sandstone nodules from Pliocene deposits of Lebrija (Seville, SW Guadalquivir Valley) has been studied. The nodules are included in densely bioturbated finegrained sandstones and contain mould of fossil molluscs. The cement is micritic calcite with minor proportion o f dolomite. Content in authigenic cement decreases outwards the nodules related to the supply rate of carbonate and the porosity of the rocks. The nucléation and the distribution of nodules into the sediment depend on the shells distribution. The cement-forming component come from the dissolved of aragonitic shells. They growth until the source of carbonate is consumed. The dolomitization affected both the hosted sediment and the nodules, thus it is inferred that this process ocurred during late diagenesis