Early Pliocene paleoceanography of the Vityaz Fracture Zone, Central Indian Ridge

Planktic foraminifera from the calcareous substrate of a ferromanganese crust from the Vityaz Fracture Zone (VFZ), Central Indian Ridge were studied to reconstruct the early Pliocene paleoceanography of this region. Eleven species of foraminifera were encountered, among them Globorotalia menardii, Neogloboquadrina dutertrei, Globigerina bulloides and Globigerinoides ruber are prominent. Predominance of N. dutertrei in the top 3 cm of the carbonate substrate is attributed to the influx of fresh water which eventually triggered the productivity by increasing nutrient level. The presence of G. bulloides and G. menardii in significant proportions in deeper layers suggests the prevalence of open ocean upwelling. The bulk chemical composition of the substrate at different depth intervals indicated higher enrichment of trace metals in the upper sections which could have been supplied through oceanic water by the chemical weathering of terrestrial matter during the peak of the Pliocene Asian monsoon. Thus, it was concluded that during the early Pliocene the biogenic components of the substrate were distinctly contributed by both the upwelling and productivity triggered by a fresh water influx originated through the intensification of the Asian monsoon during the early Pliocene Period.