Stratigraphic framework of Rio do Sul and Rio Bonito (Triunfo Member) formations in the Hercílio river valley (SC), Paraná basin (Early Permian)

STRATIGRAPHIC FRAMEWORK OF RIO DO SUL AND RIO BONITO (TRIUNFO MEMBER) FORMATIONS IN THE HERCÍLIO RIVER VALLEY (SC), PARANÁ BASIN (EARLY PERMIAN)^*

¹

JOSÉ A. J. PERINOTTO ² and JOSÉ C. CASTRO ²

¹Instituto de Geociências, USP, São Paulo, SP.

²Instituto de Geociências e Ciências Exatas, UNESP, Rio Claro, SP.

Presented by ANTONIO C. ROCHA-CAMPOS

The main targets of this work are the Rio do Sul (upper third of Itararé Group) and Rio Bonito (Triunfo Member) formations (Early Permian) in the Hercílio river valley, northern Santa Catarina.

The Rio do Sul Formation is formed by marine and glacial deposits (shales, rhythmites, sandstones and diamictites). The overlying Triunfo Member, basal unit of the Rio Bonito Formation, is made up of sandstones, shales and locally coals, originated as postglacial deltas.

To understand the temporal and spatial evolution of the Rio do Sul and Triunfo depositional systems sequencial facies analyses of surface and subsurface (cores and logs) sections and chronocorrelation of these sections, using sedimentary cycle concepts, was applied.

Twenty-one facies were recognized in the studied area and grouped into eight successions: glacial, deglacial, deltaic, fluvial, deep marine and shallow marine offshore, shoreface, and tempestite marker.

Morphologically, three continuous scarpments separated by gentle hill topographies were mapped, which can be connected to three major transgressive-regressive sedimentary cycles.

The first cycle records "deep'' marine sedimentation, probably outer shelf, characterized at the base by varvic Lontras shale transgressing over glacial deposits of the Mafra Formation; it is followed by regressive thick-bedded turbidites. The second cycle has transgressive thin-bedded turbidites at its base overlying the first cycle deposits, and passing upwards into "regressive'' glacial (diamictites, varvites, subglacial outwash channels, etc) and fluvio-deltaic deposits. The third cycle is different in the north and south: in the north interfingering occurs between marine, glaciomarine, deglacial, marine and deltaic deposits, showing a gradual passage from the Rio do Sul Formation to the Triunfo Member. In the south, a thick "transgressive'' shallow marine system overlies the second cycle, and evolves to regressive deltaic deposits of the Triunfo Member; this initial Triunfo delta is transgressed by a tempestite marker.

The palynological content suggests a shallow marine to coastal depositional environment with strong continental influence during the Sakmarian and Artinskian stages of the Early Permian. (December 10, 1999)

^*

Supported by FAPESP, Proc. 96/00554-9.

Publication Dates

• Publication in this collection
  05 Jan 2001
• Date of issue
  Dec 2000