RESEARCH OF THE MECHANISM OF SEA LEVEL CHANGE DURING THE LAST 100 MA

The development of human society and evolution of the global environment is influenced markedly by sea level change (SLC). So it is important to know the mechanism and its primarily driving factors of the SLC. To this end, based on the reconstructed record of the SLC during the last 100 Ma, the mechanism of the SLC responding to the tectonically variations and the orbit cycles had been researched. During the last 100 Ma, the signal of 1 Ma tectonically period and 0.4~0.5 Ma oceanic carbon reservoir cycle were obvious, and the change in amplitude intensity of the 1 Ma tectonically period and 0.4~0.5 Ma oceanic carbon reservoir cycle responded well to the global tectonics, climate and biological evolution events. That is to say that the long-term eustatic changes had been influenced by the tectonically controlled sea-land distribution, changing of the global climate and biological events at the Planetary-scale period. Here, we should pay attention to that the effect of 1 Ma tectonically period had become weaker and weaker and 0.4~0.5 Ma oceanic carbon cycle become stronger and stronger after the appearance of south polar ice sheet, especially since the last 5 Ma. On the other hand, the orbit cycles, such as 100 ka eccentricity period, 40 ka obliquity period and 23 ka (and 19 ka) precession period, had different effect on the SLC. For example, these three periods had increased impact on SLC since about 0.8 Ma, 5.3 Ma and 6.2 Ma, respectively. Otherwise, the SLC and δ¹⁸O_Benthic have very high coherency at orbital cycles, which show that the SLC was influenced directly by ice volume change during the last 10 Ma. Anyway, the SLC is not only influenced by the ice volume change in high-latitude area, but also affected by the evolution of the monsoon and the change in oceanic carbon reservoir cycle in low-latitude area.