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Geochemical stratigraphy of the Paraná Continental Flood Basalts: borehole evidence
Journal article   Open access

Geochemical stratigraphy of the Paraná Continental Flood Basalts: borehole evidence

DAVID W. Peate, MARTA S. M. Mantovani and CHRIS J. Hawkesworth
Revista brasileira de geociências, Vol.18(2), pp.212-221
06/01/1988
DOI: 10.25249/0375-7536.19988212221
url
https://doi.org/10.25249/0375-7536.19988212221View
Published (Version of record) Open Access

Abstract

Stratigraphic studies can provide an insight into the poorly understood geodynamic process for the generation and emplacement of large continental flood basalt provinces by revealing the structure and sequential evolution of the lava field. Such studies are still in their infancy in the Paraná, where lack sufficient topographic relief has confined work mainly to the well-exposed coastal escarpment in south-east Brazil. In this paper, a new approach is taken by analyzing drillcore chippings from four oil-company boreholes in the central Paraná basin. Major and trace element analyses distinguish three geochemical units by their low, intermediate, and high TiO2 contents respectively, and demonstrate the validity of geochemical data from such material. Each borehole retains a coherent stratigraphy with the transition from low-Ti to high-Ti lavas with time, and together they show an overlapping sequence of geochemical units dipping northwards, which could suggest a northward migrating source for the Parana magmatism in this central-north region. The available data on geochemical stratigraphy of the Paraná, is summarized in a north-south cross-section through the lava field that shows the salient features of the Paraná stratigraphy; the stacking of units in the northern boreholes; the complex transition between low-Ti and high-Ti magma types in the coastal profiles of Santa Catarina state; and the concentration of acid volcanics along the present day continental margin.

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