Estudio textural y mineralógico de rizocreciones en los suelos terciarios de la cuenca del río Amarguillo (Toledo)

Abstract

The paleosoils of the Miocene from the Amarguillo river basin show an important development of edaphic features. These are principally argillaceous fillings of old root casts. These rizocretions show several different textures of cements such as radial-fibrous calcite, sparry and microstalactitic. They also show some argillaceous aggregates, Fe-Mn and Ti oxides in addition to other detrital grains. The characteristics of these fillings are due to the activity related to the flow of the soil porewater and the biologic control of some of these processes. Barite idiomorphic crystals are authigenic minerals growing in some of the rizocretions, which indicate excepcionally dry climatic conditions during determinated periods of the soil development. The paleosoils studied and classified as alfisols and ultisols, had a shallow burial and belong to time periods with scarce precipitations and alkaline-saline porewater flow.