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PALEOVENTOS E PALEOCORRENTES SUBAQUOSAS DO SISTEMA DEPOSICIONAL PIRAMBÓIA NOS ESTADOS DE SÃO PAULO E PARANÁ, BACIA DO PARANÁ: ESTUDO BASEADO EM ANÁLISE ESTATÍSTICA DE DADOS AZIMUTAIS

2004; Sociedade Brasileira de Geologia; Volume: 34; Issue: 2 Linguagem: Inglês

10.5327/rbg.v34i2.1114

2317-4889

Paulo César Fonseca Giannini, André De Oliveira Sawakuchi, Luiz Alberto Fernandes, Leandro Menezes Donatti,

Geochemistry and Geologic Mapping

Cross stratification dip directions data distributed along the outcrop area of the Piramboia eolian depositional system (Permian and/Triassic of Parana Basin), in the states of Sao Paulo and Parana, South Brazil, were grouped according to stratigraphic interval, geographic position and depositional facies criteria. Paleowinds and subaquous paleocurrents directions were estimated from eolian and subaqueous (coastal and/or fluvial) facies data, through statistical analysis. The geographic distribution of these paleocurrents and paleowinds directions, during the development of the Piramboia system, is discussed in terms of provenance and paleogeography, including aspects of atmospheric circulation and relief. The paleowind pattern shows a convergence zone, in the State of Parana, characterized by eolian influx from NW and NE, in the northern area, and from SW, in the southern area. During the development of Piramboia depositional system, this zone migrates from the central to the south-central portion of the Parana State. About the subaqueous facies for the lower Piramboia depositional system, the paleocurrents exhibit provenance from NE in the southwest of Sao Paulo State and north of Parana State. Bidirectional paleocurrents (NNE-SSW) are observed in the central-eastern area of Sao Paulo State. For the upper Piramboia depositional system, the paleocurrents found are from SE in the northern Sao Paulo State, and from NE and NNE in the central and southern areas of Parana State. Paleocurrents with high dispersion, without a main dip direction, were observed in the central-eastern portion of Sao Paulo and northern Parana. The observed paleowind pattern reflects air mass convergence, in global or regional scale of atmospheric circulation. In the regional scale, this convergence would be related to blockade exerted by a geographic barrier in Parana, which acted as an obstacle to the southern winds, in its north flank, and to the northern winds, in its southern flanks. The coincidence between the zone with reversal of paleowinds and subaquous paleocurrents and the area with concentration of rudaceous facies und with thinning of the stratigraphic unit are suggestive of the existence of structural highs internally to the basin during the development of the Piramboia depositional system.