Gephyrocapsa kennettii sp. nov., a new calcareous nannofossil species from the Middle Pleistocene, Solomon Sea, western equatorial Pacific

Abstract

Detailed examinations of middle Pleistocene sediments of ODP Hole 1115B and CoreMD05-2925 in the Solomon Sea, southwest equatorial Pacific, reveal a distinctive new form of the calcareous nannofossil group of gephyrocapsid which has peculiar elongate kite-shaped slits on the distal shields of the coccolith. A new species,Gephyrocapsa kennettii sp. nov., is proposed and described in this study with SEM (scanning electron microscope) images. The coccolith of this new species is elliptical in shape, bearing 2 to 19 kite-shaped slits on the distal shield and a low-angle, raised arch-like bridge. The distal shield has fewer slits than G. protohuxleyi which has slits in between all elements. The bridge is orientated clockwise with am approximate 10 degree angle to the long axis when viewed distally. The average length of the distal shield is 3.26 plus or minus 0.22 (1 theta) mu m (n = 36), and, by definition, this new species belongs to the small Gephyrocapsa group. The chronologic range of this species is short, spanning only from 0.520–0.465 Ma. Its last occurrence datum is almost coevalwith that of Pseudoemiliania lacunosa at the bottom of Marine Isotope Stage 12. Morphologically, G. kennettii sp. nov. is intermediate between G. ericsonii and G. protohuxleyi and considered to be a transitional species originated by hybridization between them.