Glacially striated, soft sediment surfaces on late Paleozoic tillite at São Luiz do Purunã, PR

Autor(es)

Ivo Trosdtorf Jr. ^[1] ; Mario L. Assine ^[2] ; Fernando F. Vesely ^[3] ; Antonio C. Rocha-Campos ^[4] ; Paulo R. dos Santos ^[5] ; Alexandre Tomio ^[6]

Afiliação do(s) autor(es)

^[1] PETROBRAS S/A - Brasil

^[2] UNESP. Instituto de Geociências e Ciências Exatas - Brasil

^[3] UFPR. Laboratório de Análises de Bacias e Petrofísica - Brasil

^[4] USP. Instituto de Geociências - Brasil

^[5] USP. Instituto de Geociências - Brasil

^[6] USP. Instituto de Geociências - Brasil

• Tipo de documento: Artigo Científico
• Fonte: Anais da Academia Brasileira de Ciências; v. 77, n. 2, p. 367-378, 2005-06-00.

Resumo

Striae and furrows found on the upper surfaces of three stratigraphically superposed decimetric beds of late Paleozoic lodgement tillite of the Itararé Subgroup in the northern Paraná Basin were engraved by ploughing of clasts and possibly also ice protuberances at the base of the glacier, on unconsolidated to partially consolidated sediment. Associated features indicate that the rheology of the bed varied from stiff during lodgement to soft and deformable during ploughing. Poor drainage of meltwater at the glacier-bed interface may have contributed to lower the strength of sediment to deformation. The deformed interval was probably generated during a single glacial phase or advance of a glacier grounding in a marine or lacustrine water body. Changes in the dynamics of the glacier involving slow and fast flow were correlated respectively with alternation of deposition and erosion. The proposed model is analogous to that of lodgement till complexes from the Pleistocene of the northern hemisphere. Retreat of the glacier was probably fast, followed by settling of muds on top of the upper striated and furrowed surface, and progradation of deltaic sands during post-glacial time. (AU)

• Processo FAPESP: 98/02183-3 - Analise de paleocorrentes e paleogeografia da bacia do parana.
• Beneficiário: Mario Luis Assine
• Modalidade de apoio: Auxílio à Pesquisa - Regular
• Processo FAPESP: 00/12125-2 - Glaciação neopaleozoica externa a Bacia do Paraná I: Sudeste e Nordeste do Brasil
• Beneficiário: Antonio Carlos Rocha-Campos
• Modalidade de apoio: Auxílio à Pesquisa - Regular