Premium
Floral changes in calcareous nannofossils and their paleoceanographic significance in the equatorial Pacific Ocean during the last 500 000 years
Author(s) -
Chiyonobu Shun,
Sato Tokiyuki,
Narikiyo Reika,
Yamasaki Makoto
Publication year - 2006
Publication title -
island arc
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.554
H-Index - 58
eISSN - 1440-1738
pISSN - 1038-4871
DOI - 10.1111/j.1440-1738.2006.00543.x
Subject(s) - upwelling , geology , paleoceanography , calcareous , oceanography , quaternary , abundance (ecology) , paleontology , relative species abundance , water mass , pacific ocean , ecology , biology
The late Quaternary calcareous nannofossil assemblages from Ocean Drilling Program Holes 807A and 846B, located in the western and eastern equatorial Pacific Ocean, respectively, were analyzed to clarify changes in surface‐water conditions during the last 500 000 years. The uppermost Quaternary sediments in both holes contain abundant nannofossils, and their assemblages are characterized by high species diversity. The absolute abundances of coccoliths (specimens/g) and relative numbers of small reticulofenestrids decreased drastically in both holes between 0.3 and 0.2 Ma, whereas the relative abundance of warm‐water species and Florisphaera profunda increased suddenly at this time. These data indicate that upwelling around the western and eastern equatorial Pacific regions weakened after 0.2 Ma, which was caused by a decrease in trade‐wind strength.