Late Pliocene–Pleistocene stratigraphy and history of formation of the Ioffe calcareous contourite drift, Western South Atlantic

Abstract

The high-resolution SES-2000 deep seismic profiles performed by R/V Akademik Ioffe (2010) recorded a calcareous contourite drift over the Florianopolis fracture zone ridge, South Atlantic, named the Ioffe Drift. Core AI-2436 retrieved from the drift summit recovered calcareous nannofossil–foraminiferal ooze contourites with small amounts of fine-grained terrigenous siliciclastic material. The calcareous ooze is intercalated with foraminiferal sand and more clayey ooze layers in the Upper Pleistocene section. According to planktonic foraminiferal and nannofossil biostratigraphy, the age of the uppermost section of the drift ranges from the Late Pliocene to the Late Pleistocene. It includes several stratigraphic hiatuses due to erosion, especially at the end of Pliocene–Early Pleistocene and in the intervals 1.51–0.81 and 0.44–0.27Ma. The Ioffe Drift accumulated under the influence of the eastern branch of the Antarctic Bottom Water (AABW) outflow from the Vema Channel. Temporary intensification of the AABW flow, likely due to its increased production in the Weddell Sea, led to deep erosion ultimately resulting in long-term hiatuses and hence contributing to the enormously compressed Upper Pliocene–Middle Pleistocene section of the drift.