Aptian/Albian (Early Cretaceous) paleogeography of the South Atlantic: a paleontological perspective

Mitsuru Arai

doi:10.5327/z2317-4889201400020012

Abstract

Paleontological data obtained in recent years reinforce the hypothesis that Aptian marine sedimentation in the sedimentary basins of the Brazilian continental margin - except the Pelotas basin, the southernmost Brazilian basin - took place under the domain of waters coming from the north through the Tethys Sea (Central Atlantic). Tethyan waters could reach the basins of the Brazilian continental margin via the seaway then existing in the present-day region of northeastern Brazil. Here there are records in several basins, notably in the Sao Luis (Codo Formation), Parnaiba (Codo Formation), Araripe (Santana Formation), Tucano (Marizal Formation), Sergipe (Riachuelo Formation) and Camamu (Algodoes Formation) basins. Despite irrefutable marine evidence - e.g., dinoflagellates, echinoids, foraminifera, molluscs and fishes, conspicuously present in the Araripe Basin - there are very few paleogeographic reconstructions that include the seaway which is totally ignored in the international literature. The skepticism is even greater in relation to the Tethyan affinity although the evidence has been well documented by molluscs and dinoflagellates, together with ammonoids in the Sergipe Basin. That skepticism may be due to the fact that, in tectonic and geodynamic terms, the opening of the South Atlantic indeed proceeded from south to north, at least in the part that extends from Argentina to the northeastern Brazilian state of Paraiba.

Highlights

Contrary to the paleogeographic reconstruction based on the configuration of tectonic plates, the initial Mesozoic entrance of sea water into the BCMBs (Brazilian Continental Margin Basins, Fig. 1) resulted from the incursion of oceanic waters from the northern hemisphere, i.e., from the Tethys Sea
Its occurrences can be diachronic on a worldwide scale, but in Brazil it is confined to strata of Aptian age
The Tethyan influence persisted in all BCMBs until the latest Albian (Vraconian)

Summary

INTRODUCTION

Contrary to the paleogeographic reconstruction based on the configuration of tectonic plates, the initial Mesozoic entrance of sea water into the BCMBs (Brazilian Continental Margin Basins, Fig. 1) resulted from the incursion of oceanic waters from the northern hemisphere, i.e., from the Tethys Sea. The Tethyan Realm in the BCMBs even in the Aptian (125 – 113 Ma) and confirmed that Tethyan waters emanating from the north reached as far as the Santos Basin, which represents the southernmost Tethyan-influenced site in the South Atlantic. In several Brazilian interior basins (e.g., Parecis, Parnaíba and São Francisco basins), Zuni represents their only Cretaceous succession (Arai 2002). Tethyan water arrived in the BCMBs via the seaway existing in the present-day region of northeastern Brazil, passing through the São Luís, Parnaíba, Araripe, Tucano and Sergipe basins. The complete absence of marine sediments coeval to the Santana Formation in the interior basins situated between the Araripe and Potiguar basins (e.g., Icó, Iguatu, Lima Campos, Malhada Vermelha, Lavras da Mangabeira and Rio do Peixe basins) nullifies this possibility (Arai 2006) (Fig. 3). The columns are roughly arranged from north (left) to south (right)

RESULTS

DISCUSSION

CONCLUSIONS