M. Holz1,
W. Kalkreuth2
(1) Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
(2) Universidade Federal do Rio Grande do Sul
Abstract: Application of sequence stratigraphy to coal research: an example of the Early Permian Rio Bonito Formation of southernmost Brazilian Gondwanaland
Sequence stratigraphy is a
powerful tool for prediction of facies relationships and is largely used in
petroleum prospection and exploration. In order to test the applicability of
sequence stratigraphy parameters in coal research, a high resolution
stratigraphic
framework was established for the economically important Candiota Coalfield
(Rio Grande do Sul state, Brazil) and compared with the petrographic parameters
of the coal seams.
Organo-petrographic analysis of
seven coal seams of two completely cored boreholes in that area has shown that
petrographic parameters such as the content of vitrinite and inertinite maceral
groups in the coal seams and associated Gelification and Tissue Preservation
Indices vary significantly from base to top of the coaly interval, indicating
much drier coal-forming environments at the top. The detailed sequence
stratigraphic framework permits a comparison between the fourth order flooding
events (=parasequence limits) and the vertical
variation of coal parameters.
Insofar, sequence stratigraphy and evolution of the petrographic parameters of
coals are strongly correlative, evidencing stratigraphic control on the
coal-forming conditions during the Early Permian (Artinskian/Kungurian).
This leads to a twofold
conclusion: not only may sequence stratigraphy explain variation of coal
parameters, but those may be a helpful additional tool to depict flooding
surfaces and therefore high-resolution
sequence stratigraphy. Additionally, the
recognition of the stratigraphic control on coal parameters permits a
predictive model which might be useful in coal exploration.
AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana