中太平洋海山区富钴结壳的钙质超微化石地层学研究

对“大洋一号”调查船在中太平洋采集的N1-15和N5E-06 2个富钴结壳样品进行了钙质超微化石及其生物地层学的研究与分析.这2个结壳从结构上分为3层: 致密型上层、疏松型中层和致密型下层.在研究中对各结构层和各层中有颜色或细微结构变化的层位都进行了详细的取样和分析.在识别了12个新生代钙质超微化石事件的基础上, 确定了2个结壳致密型上层结壳都为晚更新世以来的沉积, 它们的疏松型中层结壳为上新世到中更新世的沉积.对N5E-06富钴结壳来说, 其致密型下层结壳下部形成于中晚古新世到早渐新世的59.7~ 32.8 Ma期间.N1-15富钴结壳致密型下层的形成时代目前暂时定为中新世.研究注意到在2个结壳中都没有发现可信的晚渐新世到中新世的化石记录, 在个别层位之间存在着沉积间断. 

Calcareous Nannofossil Biostratigraphy for Co-Rich Ferromanganese Crusts from Central Pacific Seamounts

Calcareous nannofossils in 2 Co-rich ferromanganese crusts, N1-15 and N5E-06, from the central Pacific seamounts were analyzed in order to estimate their depositional ages. These 2 crusts show 3 structural layers: compact upper layer, porous middle layer and compact lower layer. 12 Tertiary to Quaternary nannofossil events were recognized. The upper layers of these 2 crusts were deposited since Late Pleistocene, while their middle layers were formed from Pliocene to Middle Pleistocene. The age of the lowest sample from N5E-06 crust was estimated as 55.3-59.7 Ma in the Middle to Late Paleocene, and the duration for lower part of the lower layer was given between 59.7-32.8 Ma from the Middle Paleocene and Early Oligocene. For the lower layer of N1-15 crust, the age was roughly determined to be Miocene, due to the lack of reliable fossils. This study notes that no reliable Late Oligocene to Miocene nannofossil markers were found in these 2 crusts. Furthermore, sedimentation hiatus was observed.