Biostratigraphic analysis of the top layer of sediment cores from the reference and test sites of the INDEX area

Radiolarian fossil study in the sediment cores collected during the pre- an d postdisturbance cruises of the Environmental Impact Assessment (EIA) Indi an Ocean Experiment (INDEX) program of deep sea mining in the Central India n Ocean Basin suggests a pronounced directional deposition of fossil radiol arians exhumed during the deep sea benthic disturbance experiment. The rela tive occurrences of the Stylatractus universus species that became extinct similar to 0. 425 million yeats before present were mostly confined to the older and deeper strata of the sediment of the disturbance tract in the sou thwestern direction. This pattern is remarkable and suggests that the distu rbance plume has been preferentially,redeposited in the southwestern direct ion. This observation is in concurrence with the prevailing southwestern ab yssal current during the disturbance experiment in the Central Indian Basin .