FÁCIES, ANÁLISE ESTRATIGRÁFICA E EVOLUÇÃO PÓS-GLACIAL DO MEMBRO TRIUNFO/FORMAÇÃO RIO BONITO, NA FAIXA SUBAFLORANTE DO NORTE CATARINENSE

Abstract

The Triunfo Member, the basal unit of Rio Bonito Formation, is the post-glacial deltaic system of the glaciomarine and marine sedimentation of the Rio do Sul Formation (Itararé Group). The wells drilled by CPRM in the eastern margin of Paraná Basin are continuously and constitute an important documentation of the Rio Bonito Formation. The sequential analysis of seven wells in northern Santa Catarina State allows the characterization of the following fácies successions/associations: glaciomarine, deglaciation, fluvial, deltaic, and marine offshore to shoreface. A stratigraphic section through the studied wells reveals the lateral distribution of the fácies associations and the mapping of erosional regressive (corresponding to sequence boundaries) and transgressive surfaces. The investigated area is compartmentalized into three sedimentation domains: the northern one, PP9 to PP 11 wells, where six depositional sequences (four in the Rio do Sul-Triunfo "transition" and two in the Triunfo Member) overlie the marine substrate of the Rio do Sul Formation. Each sequence is formed by fluvial, deltaic and deglaciation associations (lower part of the sequence), and by glaciomarine and marine associations (upper part). Despite little sampling in the Rio do Sul Formation, the central domain reveals distinctive characteristics (PP6 to PP8 wells): thick glaciomarine deposits in the Rio do Sul substrate, thin "transition" zone and the predominance of fluvial associations in the Triunfo Member. The southern domain, PP4 and PP5 wells, has thick marine shelf deposits in the underlying Rio do Sul Formation, which partially corresponds to the Rio do Sul-Triunfo "transition" from the northern domain. Five depositional sequences are identified in the southern domain, and they are correlated with the central and northern domains. In addition, the marine shelf association of the southern domain changes laterally to deltaic deposits toward south (the "basal Triunfo delta" of the Rio do Sul área).