Tectono-sedimentary evolution of the Itararé Subgroup (Late Paleozoic) in the southern Ponta Grossa arch, Brazil

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REGIONAL EARTH SCIENCES IGc-USP

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ANTONIO C. ROCHA-CAMPOS

TECTONO-SEDIMENTARY EVOLUTION OF THE ITARARÉ SUBGROUP (LATE PALEOZOIC) IN THE SOUTHERN PONTA GROSSA ARCH, BRAZIL^*

JOSÉ R. CANUTO, ANTONIO C. ROCHA-CAMPOS AND PAULO R. SANTOS

Instituto de Geociências, USP, São Paulo, SP.

The tectono-sedimentary evolution of the Itararé Subgroup (Late Paleozoic) in the southern flank of the Ponta Grossa arch, States of Santa Catarina and Paraná, Brazil, is interpreted through stratigraphic analysis of outcropping beds. Its evolution seems to have been influenced by faulting causing rising and falling of the arch.

The section analyzed runs some 50 km SE-NW, from Mafra (SC)-Rio Negro (PR) to Lapa (PR) and includes about 700 m thickness of glacio-clastic beds assigned to the Campo do Tenente and Mafra formations.

Paleocurrent orientation, sense of the movement of the gravity driven Paraná glacial lobe, and stratigraphic data indicate a basin paleoslope initially dipping 7' N during deposition of the Campo do Tenente Formation. Isopach data shows that the unit fills a large trough trending NW, resting on abraded and striated rocks of the Paraná Group (Devonian). This interpretation implies a tectonically negative behavior of the Ponta Grossa arch during this time, also shown by isopach maps of palynobiostratigraphic intervals G and H₁ (Santos et al. 1996. Pal, Pal, Pal, 125: 165-184).

A change in the paleoslope toward SW in the upper part of the Itararé Subgroup is suggested by the orientation of gravity mass-flow deposits in the lower part of the Mafra Formation. This and the isopach data for equivalent palynobiostratigraphic intervals H₂-H₃ point to the Ponta Grossa arch becoming tectonically emergent.

A final change in the paleoslope toward N-NW in the uppermost part of the Itararé Subgroup (interval I₁?) is again suggested by orientation of paleocurrents and trend of the Lapa sandstone, a sinuous, long, linear body that seems to fill a subglacial tunnel valley. The valley cuts through Mafra and Campo do Tenente beds down to basement rocks of the Paraná Group at its northern end. This is interpreted as tectonic negative behavior of the Ponta Grossa arch. We propose that the sedimentary filling of the Lapa tunnel valley might be coeval with deposition of the Mafra and the Rio do Sul formations. — ( December 8, 2000 )

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^*

Apoio FAPESP, Processo No. 97/13973-2.

Publication Dates

• Publication in this collection
  08 Oct 2001
• Date of issue
  Sept 2001