Abstract
A new classification scheme has been developed to assign the lava flows of the Parana flood basalt province into geochemically distinct basaltic magma types, with six types distinguished on the basis of specific major and trace element abundances and/or ratios. By mapping these types within the lava sequences it has been possible to determine the internal stratigraphy of the lava pile on a regional scale. Data from previous studies on road profiles traversing the coastal Serra Geral escarpment and from some new studies are summarized, together with results of investigations on samples of drill-core chippings from nine boreholes in the central Parana region. The borehole samples have indicated a stacking of units of different magma types all overlapping to the N, which suggests that the main locus of magmatism moved N with time within the Parana basin. This migration could be related to the N propagation of rifting during the initiation of the S Atlantic ocean. Maps of the surface distribution of samples of each magma type show a pattern consistent with the stratigraphy inferred from the boreholes, although suggesting that the shift in magmatism may have been towards the NW. It is proposed that the Parana can be divided into two principal magmatic centres: 1) an older one in the S, comprising the Gramado, Esmeralda and Urubici magma types, and 2) a younger one, developed approx 750 km to the N, formed by the Pitanga, Paranapanema and Ribeira magma types.