Abstract
Summary Paleosols have been usually studied on specific rock types or in relation to important climatic changes. In northeastern Brazil, climatic conditions during the Cenozoic have not changed very much; only slight oscillations have occurred within the humid tropical belt near the coast, and the climate has become slowly more semi-aridinland. Nevertheless, the resulting soils developed during non sedimentary phases show differences large enough for them to be used as stratigraphical indicators. The partly buried, ancient soil profiles which have been recognized are all of tropical origin with lateritic character in various stages of development. (1) The oldest profiles preserved show strongly kaolinic soils upon iron-poor basement rocks. Generally their somewhat mottled B-horizons are clearly visible under a cover of correlative relief deposits. Their age is about Eocene-Oligocene and their stage of development senile. (2) On top of these sediments is a soil composed of a lateritic crust, interpreted as a mature lateritic soil, formed during the Pliocene. In the coastal area the crust is replaced by an iron-rich horizon which is not very hard. (3) During the non-sedimentary phases of the Pleistocene, again lateritic soils developed actually presenting an initially mature stage. They are present as whitish leaching zones and iron oxide concentrations on unpermeable layers or in vertical columns. (4) More recent, of Late Pleistocene to Holocene age, is the youngest soil, present as a tropical red-yellow podsol. All profiles are quite easy to distinguish and serve thus for perfect stratigraphical and paleoclimatic correlation.
Published Version
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