Assembléias de foraminíferos e os paleoambientes cenozóicos de Caravelas, Bahia, Brasil

Abstract

Samples form sixteen cores obtained from a drilling at Caravelas, Bahia, were analized both on the point of view of foraminiferal assemblages and lithologies. The paleoecological analysis of the foraminiferal assemblages were aimed at the reconstruction of the paleoenvironments and from these to the possible fluctuations of the ancient seashores. The studied paleoecological parameters were: 1) Relative frequence of specimens; 2) faunistic dominance and dominant taxa; 3) Specific diversity; 4) Planktonic/Benthonic rate; 5) Characteristic taxa indicative of certain environmental conditions; 6) Size of the specimens; 7) Surviving curves; 8) Ornamentations and thicknesses of the tests; 9) Fragmentation of the tests; 10) Other organisms present; 11) Lithologies; 12) Relative spatial positions of the samples. These studies led to the assumption that at the well place four encroachments and retreats of the sea took place from the Eocene on. Such encroachments and retreats could of cource be the results of tectonic, eustatic or sedimentological factors and it is impossible to reach at the real causes with only one drilling at hand. Furthermore the well was not thoroughly cored therefore other sea fluctuations might have occurred which were not detected because of the lack of cores. This paper tries to demonstrate anyway the potentiality of this approach wich could eventually be refined with cores from other wells.