西太平洋麦哲伦海山铁锰结壳生物地层、生长年代及沉积环境

Biostratigraphy,Growth Period and Sedimentary Environment of Ferromanganese Crusts From Magellan Seamounts in the Western Pacific

通过对西太平洋麦哲伦海山M1-1,M2-1铁锰结壳样品超微化石的分析,在Ⅱ+Ⅲ层结壳层中发现了中新世以来的超微化石种类H.carteri,C.leptoporus和G.oceanica。据此,把Ⅱ+Ⅲ层结壳归属于第3个形成期中新世-更新世发育的结壳,相当于Halbach等人提出的年青世代层。Ⅰ层内钙质超微化石的缺失可能与白垩纪末期碳酸盐补偿深度的骤然变化有关。冷的、富氧的南极底层水不仅为结壳的形成提供了良好的氧化环境,而且造成了广阔的区域性的沉积间断,从而为结壳提供了生长场所。

Based on the study of nannofossils in feromanganese crusts MDD-53-1 and MED-48-1 collected from Magellan Seamounts in the western Pacific, the nannofossil species H. carteri, C. leptoporus and G. oceanica since Miocene were identified in crust layers Ⅱ and Ⅲ, so the crusts in layers Ⅱ and Ⅲ are classified as the crust developed in the third formation period, the Miocene-Pleistocene period, which corresponds to the younger time layer proposed by Halbach, et al.. The absence of calcareous nannofossils in layer Ⅰ may be related to the abrupt changes of carbonate compensation depth （CCD） in the late Cretaceous. The cold and oxygen-rich Antarctic Bottom Water not only provided a favorable oxidation environment for the formation of crusts, but also brought about a broad and regional sedimentation hiatus to create a growth place for the crusts.