南沙群岛海域沉积物古地磁参数对米兰科维奇周期的响应

A RESPONSE TO MILANKOVITCH CYCLE OF SEDIMENTS' PALEOMAGNETISM PARAMETERS IN NANSHA ISLANDS AND ADJACENT SEA AREA

对南沙群岛海域８７－１１柱样天然剩余磁化强度（ＮＲＭ）及９０－１０３柱样ＮＲＭ、磁化率（ｘ）、剩磁倾角（Ⅰ）等的功率谱分析表明：晚更新世以来该区沉积物的古地磁参数较好地反映了古气候、古环境的变化，响应着古气候变化的米兰科维奇天文学周期；在周期成分中，以地球轨道偏心率周期（ｅ）及岁差周期（ｐ）为主，地轴倾斜度周期（ε）无明显表现，同时获得了与特殊地球位置相关联的岁差半周期成分。研究还表明，古地磁参数存在着明显的对古气候变化的非线性响应，明显不同于开阔大洋；同时，不同的沉积单元，沉积物古地磁参数对古气候变化响应的灵敏度各不相同。

he results of power spectrum analyses on sediments' natural remanent magnetization (NRM) of core 87-11 and NRM, magnetic susceptibility(x),inclination(I)of core 90-103 from Nansha Islands and adjacent sea area show that:since Late Pleistocene, the paleomagnetism parameters reflect changes in the paleoclimate and paleoenvironment,and respond to the Milankovitch Cycle.The results also show that the eccentricity (e) and precession (p) take effect in this area,but obliquity(ε)takes only little effect,meanwhile,the semi-cycle of precession is obtained in this study,which relates to special geographic sites.It is also found that the paleomagnetism parameters have nonlinear response to the paleoclimatic change, which is different from the open ocean. Also,the sensibility of paleomagnetism parameters change to paleoclimate varies for different sedimentary units.