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

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 São Luís (Codó Formation), Parnaíba (Codó Formation), Araripe (Santana Formation), Tucano (Marizal Formation), Sergipe (Riachuelo Formation) and Camamu (Algodões 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 Paraíba.

Comments on paper by M. Arai "Aptian/Albian (Early Cretaceous) paleogeography of the South Atlantic: a paleontological perspective"

“…Nevertheless, as pointed out by Arai (2014), the Late Aptian to Early Albian marine ingression in the Araripe Basin is long-established (Beurlen 1962, Beurlen 1971a, Beurlen 1971b, Mabesoone & Tinoco 1973, Coimbra et al 2002, as indicated by the presence of echinoids (Beurlen 1966, Manso & Hessel 2012, as well as microfossils, such as dinoflagellates (Arai & Coimbra 1990, Coimbra et al 2002. On the other hand, the Tethyan affinity is undoubtedly assumed by the author based on the occurrence of members of the Subtilisphaera ecozone recorded in the São Luís, Ceará, Parnaíba and Araripe basins.…”

“…By considering this, we suggest that several data on distinct areas of Geology (i.e., sedimentology, structural geology, stratigraphy and paleontology) should not be overlooked when aiming a more precise paleogeographic scenario. Our purpose in this comment is to take part of this discussion and highlight that a multidisciplinary approach must be addressed in order to confirm or refute the paleogeographic model proposed by Arai (2014). In our opinion, an integrated paleogeographic reconstruction must be based on 1. the number of Tethyan versus austral fossil representatives and their accurate stratigraphic occurrence, 2. the precise timing of the first marine ingression in the continent interior, 3. the basin-filling pattern and stratigraphic architecture of the depositional sequences, 4. paleocurrents and other paleogeographic indicators, and 5. the continental paleotopography and paleodrainage.…”

“…Based on paleontological data, Arai (2014) recently proposed a distinct scenario in which the earliest marine ingression in the Brazilian marginal basin would have taken place during the late Aptian "under the domain of waters coming from north through the Tethys Sea (Central Atlantic)". According to Arai's model, "Tethyan waters could reach the basins of the Brazilian continental margin via the seaway then existing in the present-day region of northeastern Brazil".…”

“…The model proposed by Arai (2014) is mainly based on dinocyst fossils (Arai 1999(Arai , 2011, as well as other micro and macrofossil evidences (forams, radiolarians, molluscs, echinoids, crustaceans, fishes and pleurodiran turtles) from literature. A very important point is that several of these macrofossils were not formally described or even properly illustrated in available scientific venues.…”

Ground Penetrating Radar investigation of depositional architecture: the São Sebastião and Marizal formations in the Cretaceous Tucano Basin (Northeastern Brazil)

“…The basin encompasses alluvial fan deposits (Salvador Formation), lacustrine deposits (Candeias Formation), deltaic deposits (Ilhas Group), and fluvial deposits (São Sebastião Formation) (Magnavita 1992, Magnavita et al 1994, Costa et al 2007a, 2007b, covered by the Marizal Formation, a thin succession of fluvial deposits with a record of marine incursion (e.g. Arai 2014, Amaral & Brito 2012, deposited during a late reactivation of the rift .…”