TX 75083-3836, U.S.A., fax 01-972-952-9435. Abstract

CYCLICITYIN THE BURACICASTAGE (LATEBARREMIAN) OF THE RECONCAVOBASIN. The Buracica Stage (Late Barremian) of the Reconcavo basin is characterized by the cyclic succession of fluvial, deltaic and lacustrine sediments of the Sao Sebastiao Formation, which can be divided into 6 third order and 20 fourth order stratigraphic sequences. Oxigen stable isotope study indicates a major climatic control over the architecture of those sequences. The cyclestratigraphic study of this interval, based on the orbital cycles of Milankovitch, suggests that the 3'd order sequences were deposited in a time span of 413 ka, equivalent to the period of the long eccentricity. The 4 th order sequences are correlated with the obliquity cycles, with a time span of38 ka and 49 ka. Based on these results, the total time span for the deposition of the Buracica sediments is of2,48 Ma.