Determination and geological implication of O-Si isotope of the sediment core in the CC area, the Pacific Ocean

Conclusions

• 1. It is a successful attempt to test and study O-Si stable isotopic composition of SiO₂ shells of radiolarian of sediment core below the depth of 5 000 m in the Pacific Ocean because of lacking of calcium shells below CCD in ocean. The distribution and variation, from 21.2 X 10⁻³ to 34.5 × 10⁻³ for δ¹⁸O_SMOW and from 0.2 × 10⁻³ to 1.2 × 10⁻³ for δ³⁰Si_NBS-28, have certain link with and difference from those of other oceanic organisms.

• 2. The relationship between δ¹⁸O and δ³⁰Si values indicates obviously that the humeric distribution of core samples from No. 1787 station shows two groups separated by the depth of 160 cm. This distribution is also recorded by two kinds of isotopic curves (fig. 2(a), (b)), reflecting the evolutional difference of oceanic environment and stratigraphic sequence between the upper and lower layers separated by the depth of 160 cm.

• 3. Through a correlation of δ¹⁸O values, the core from No. 1787 station shows that since 27 Ma, the Pacific Ocean has experienced 7 cold/warm changes, accompanied by the frequent variations of global ice volume and sea level.