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Fifty-six samples of nannofossil ooze were col-lected from Core PC5794 in the northern equatorial Pacificat 5 cm intervals. With the methods of mass spectrometer(VG354) and ICP, the Nd isotopic compositions ((?)), Milcontents and Mg/Sr ratios of carbonate phase have beenanalyzed. CaCO_3 contents of bulk sediments were obtainedby dissolution of 0.5 mol/L HC1. Based on these data, thehigh-resolution (?) profile of seawater in early Miocenewith core depth(or time) have been established. The values of(?) I range from -6.2 to -2.97 and 4 fluctuation cycles ex-isted during 24.06-22.02 Ma. 4 low (?) values (about -6.4)correspond to high CaCO_3 contents, which implicates thatthere were 4 cold epochs or 4 times of Antarctic Bottom Wa-ter activity. They occurred at the time of 24.06 Ma, 23.85 Ma,22.88 Ma and 22.26 Ma, respectively. High (?) values cor-respond to the high Mn contents and high values of Mg/Srratio, which indicates the existence of 4 intense hydrothermalactivity periods during 24.06-22 Ma, the durations of themare 4.05-23.98 Ma, 23.69-23.15 Ma, 22.74 22.37 Ma and22.06-22.02 Ma, respectively.
Fifty-six samples of nannofossil ooze were col-lected from Core PC5794 in the northern equatorial Pacificat 5 cm intervals. With the methods of mass spectrometer (VG354) and ICP, the Nd isotopic compositions ((?)), Milcontents and Mg / Sr ratios of carbonate phases have beenalyzed. CaCO_3 contents of bulk sediments were obtained by dissolution of 0.5 mol / L HC1. Based on these data, the high-resolution (?) profile of seawater in early Miocenewith core depth (or time) have been established. The values of (?) I range from -6.2 to -2.97 and 4 fluctuation cycles ex-isted during 24.06-22.02 Ma. 4 low (?) values (about -6.4) correspond to high CaCO_3 contents, which implicates that have been 4 cold epochs or 4 times of Antarctic Bottom Wa-ter activity. They occurred at the time of 24.06 Ma, 23.85 Ma, 22.88 Ma and 22.26 Ma, respectively. High (?) values cor-respond to the high Mn contents and high values of Mg / Srratio, which shows the existence of 4 intense hydrothermalactivity periods during 24.0 6-22 Ma, the durations of the mare 4.05-23.98 Ma, 23.69-23.15 Ma, 22.74 22.37 Ma and 22.6.06-22.02 Ma, respectively.