Controlling factors of coccolith distribution in surface sediments of the China seas: marginal sea nannofossil assemblages revisited

Abstract

Three nannofossil assemblages have been distinguished in the East and South China seas: the neritic assemblage at the inner shelf dominated by Gephyrocapsa oceanica; the oceanic assemblage from the outer shelf to continental slope, with a higher diversity and with Emiliania huxleyi outnumbering G. oceanica; and the dissolution assemblage below lysocline again with G. oceanica as dominant species. These assemblages include a total of 35 species. The ‘marginal sea nannofossil assemblage’ in the China seas is not clearly distinguishable. There is a ‘sharp biological boundary’ of coccolith assemblages between neritic and oceanic waters, but not between marginal seas and open ocean. The oceanic coccolith assemblage in marginal seas can hardly be distinguished from that of the ocean. G. oceanica dominance is specific to neritic, warm, moderate-to-high fertile water, but can not be used as an indicator of marginal sea or monsoon influence. Therefore, the use of ‘marginal sea nannofossil assemblage’ or about ‘monsoon control on coccolith assemblages’ is inappropriate.