Application of
Climatic Changes to Understand Sedimentary Processes and a Tool to Refine the Stratigraphy in Brazilian Sedimentary Basins - An Overview
Azambuja Filho,
Nilo Chagas de1,
Alvaro H. Arouca de Castro1, Armando A. Scarparo Cunha2, Carlos Roberto Becker1,
Clovis Francisco Santos1, José Guilherme
R. da Silva3, José M. Cronemberger
Mendes4, Maria do Carmo G. Severino1,
Paulo R. C. Cunha1, Ricardo Latge M. de
Azevedo5 (1) PETROBRAS, Rio de Janeiro, Brazil (2) PETROBRAS, Rio de
Janeiro, (3) PETROBRAS, Vitória, Brazil (4)
PETROBRAS, Huston (5) PETROBRAS,
Significant climatic fluctuations can be
observed in the Brazilian sedimentary basins, ranging in age from Paleozoic to
Quaternary. These climate changes have been directly related to Milankovitch forcing. For example, during the opening of
the South
Atlantic,
both lacustrine and marine sediments preserved
climate cycles. From the Late Jurassic through Aptian,
seven major climatic fluctuations have been interpreted from lithological and palynological data;
four represent changes from arid to semi-arid conditions and three from
semi-humid to humid conditions. These climatic changes have been strongly
linked to higher frequency Milankovitch oscillations
(precession-scale events). In the Albian, carbonates
of Campos and Santos basins contain ten thick intervals composed of cycles
varying from 0.3 to 1.4 my, and at least seventy thinner intervals with shorter
periodocities. In the Oligocene and Miocene of these
basins, carbonate-siliciclastic intervals display
well defined eccentricity and precession cycles, as well. Devonian reservoir
and source rocks in the Amazonas basin show
depositional cycles with strong control by eccentricity (100 kyr). This has permitted the accuracy of age estimation to
improve from 106 to 105 years. In the Solimões basin,
the carbonate-evaporitic succession of Pennsylvanian
age display well developed cyclic sedimentation deposited as 4th and 5th order
cycles, and related to relative sea-level variations induced by eccentricity
and precession cycles.
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