ENSAIO DE CARACTERIZAÇÃO ESTRATIGRÁFICA DO CRETÁCEO NO ESTADO DE SÃO PAULO: GRUPO BAURU

PAULO C. SOARES, PAULO M.B. LANDIM, VICENTE J. FOLFARO, AGOSTINHO F. SOBREIRO NETO

Resumo


Mapping survey over 135,000 km2 in the State of São Paulo, made by Departamento de Águas e Energia Elétrica do Estado de São Paulo(DAEE) in cooperation with other organisations, allowed the stratigraphical characterization of the Cretaceous rocks younger than Serra Geral Formation (lower Cretaceous) in that region. Due to the regional stratigraphical analysis of these sediments is proposed for them the term Bauru Group which is constituted by the following four Formations: 1) Caiuá Formation: fine to medium sandstone with regular to good sorting and purple color,bearing large cross stratification; occurrence limited to the Pontal do Paranapanema region; it is in unconformity over basalts of the Serra Geral Formation. 2) Santo Anastácio Formation: very fine to medium sandstone, red to purple colors; low angle cross stratifications to horizontal bedding, with rare mudstone beds intercalated; occurrence mainly in southwestern portion of São Paulo State; gradational over Caiuá Formation and with discordance over basalts. 3) Adamantina Formation: a) Araçatuba lithofacies - thick beds of mudstones, dark brown to greenish grey colors, with variations to siltstones and claystones; restricted occurrence in the southwestern portion of São Paulo State and wide one in the western and northwestern portion of the State; overlying Santo Anastácio Formation and Serra Geral Formation; b) Taciba lithofacies - beds of very fine to fine sandstones, with small to large size cross stratifications, intercalated with beds of reddish to brownish sandy mudstones; incipient lamination and sandstone lens; wide occurrence from south to the north of the State over Santo Anastácio Formation (south), Araçatuba lithofacies (west, and northwest) and basalts (northeast); c) Ubirajara Formation - coarser sandstones than that one from Taciba lithofacies, textural and mineralogical imatures, with occurrence in mid-east portion of the State over basalts, lateral gradation to Taciba lithofacies toward west and north. 4) Marília Formation: coarse to conglomeratic sandstones plentiful of calciferous cement and nodules; occurrence in the wathersheds of the principal drainages in São Paulo State inland. The contact relationship and regional distribution of the stratigraphic unities suggest a partial contemporaneous deposition in a complex fluvial system, with regional and chronological variations in the clastic affluence, in the climatic characteristics, in the subsidence ratio and in the marginal areas uplift rate.


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