Micropalaeontological dating of the basal Cretaceous section of DSDP Site 249, Leg 25, Mozambique Ridge: implications for the timing of the southern Atlantic–Indian Ocean connection

Abstract

Abstract. Tectonic models suggest the absence of a deep water connection on the Mozambique Ridge during early Neocomian time. These models imply the initiation of a deep water connection between the southern Atlantic and Indian oceans formed during Barremian–earliest Aptian times. However, previous biostratigraphic studies of the earliest deep water sediments on the Mozambique Ridge suggest that the basal section is Neocomian in age. Here, we present a new biostratigraphic analysis undertaken to test this tectonic model and determine the earliest age of deep water sedimentation on the Mozambique Ridge. Core samples from the Cretaceous interval 222.05–406.32 m (Cores 19–32) of DSDP Site 249, Leg 25, were sampled for calcareous nannoplankton and palynological analysis. Most of the sampling was concentrated on the Lower Cretaceous interval below 294 m. Our results indicate that the lower sedimentary section is no older than Barremian and therefore provides support for the age proposed by the tectonic models.