Fossil plants from the Itaquaquecetuba formation (Cenozoic of the São Paulo Basin) and their possible paleoclimatic significance

Abstract

The fossil leaves of the Itaquaquecetuba Formation (Cenozoic, Sao Paulo Basin), although very abundant and reasonably well preserved, have not been the subject of study until now. The main purpose of this paper is to establish the possible paleoclimatic significance of these leaves on the basis of their description and taxonomic determination and the ecological relationships of similar living forms. The plant association studied here indicates a tropical evergreen forest inasmuch as all the identified genera have similar forms that live at present within such a habitat. The following hypotheses are raised based on the analysis of this material: 1) The climate at the time of deposition of the sediments of the Itaquaquecetuba Formation was tropical and humid and not semiarid as suggested in previous papers; the braided type of sedimentation present in the formation, although characteristic of semiarid environments, is not exclusive to such environments. 2) The association of these plants with braided sediments could possibly be explained by tectonic reworking of previously lithified, fossiliferous sediments, in which large blocks (olistoliths) containing plant fossils were transported into the sedimentary basin.