Novos Dados Geológicos e Geofísicos para a Caracterização Geométrica e Estratigráfica da Sub-bacia de Alhandra (sudeste da Paraíba)

Abstract

Some recent geological and geophysical reconnaissance studies carried out in the Alhandra Sub-basin (southern segment of the Paraíba Basin) have revealed very interesting structural and stratigraphic behaviors that have not yet been described. Four different structural compartments with NNE-SSW trends were identified, each characterized by a particular stratigraphic pile, as a result of vertical tectonic displacements, probably post-Pliocene in age: the Alto Rio Mumbaba High (with widespread basement outcrops), the Rio Mamuaba Graben (the well-exposed Beberibe Formation with thicknesses from 100 m up to 300 m), the Rio Gramame High (a horst zone, with some basement outcrops, underlying the Beberibe Formation) and the Alhandra-Guruji- Conde-Caaporã monoclinal zone, east of the BR-101, limited to the west by a fault line. The stratigraphic sequence of the Paraiba basin represented by the Paraíba Group is complete only along the eastern monoclinal zone, where the Barreiras Group is also preserved. Along the Rio Mamuaba graben, occurrences of the Barreiras Group were not found as would be expected, and this seems to be an indication that more than one phase of vertical movement occurred, the second of which had probably removed the Barreiras Group. All these observations are preliminary and demand further geological and geophysical studies, especially at scales greater than 1/50.000