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在传统上，浮游有孔虫Ｇｌｏｂｏｒｏｔａｌｉａｔｒｕｎｃａｔｕｌｉｎｏｉｄｅｓ的初现面一直被用来作为划定海相地层更新统下界的可靠依据。然而，此一初现面（２．０ＭａＢ．Ｐ．）所界定的更新统下界与超微化石Ｇａｐｈｙｒｏｃｏｐｓａｏｃｅａｎｉｃａｓ．ｌ．初现面（１．６７～１．７ＭａＢ．Ｐ．）所界定的并不一致。这一现象对大陆边缘的沉积地层尤为显著。其主要原因是，大陆边缘的高沉积速率会导致两个基面有很的层位间距。本研究证明台湾西南部二仁溪剖面之浮游有孔虫Ｐｕｌｌｅｎｉａｔｉｎａ最后一次的旋向变化（由左至右），几乎与超微化石Ｇ．ｏｃｅａｎｉｃａｓ．ｌ．的初现面同一时间。因此，就浮游有孔虫生物地层的观点看，此一族向变化是辨识更新统下界的一个非常有用的基面。
Traditionally, the prima facie surface of the planktonic foraminifera Globorotaliatruncatulinoides has been used as a reliable basis for delineating the Lower Pleistocene of marine formations. However, the Pleistocene lower bound defined by this initial facet (2.0MaB.P.) is associated with the fossil Gaphyrocopsaoceanicas. l. The initial surface (1.67 ~ 1.7MaB.P.) Definition is not consistent. This phenomenon is particularly significant for sedimentary formations on the margin of the continental margin. The main reason is that the high deposition rate at the continental margin leads to a very large interval between the two basal planes. This study shows that the last rotational change (from left to right) of the planktonic foraminiferal Pulleniatina in the Errenxi Section, southwestern Taiwan, is almost identical to that of the superfossil F. oceanicas. l. The first appearance of the same time. Thus, from the point of view of the planktonic foraminiferal biostratigraphy, this grouping toward change is a very useful basis for identifying the lower Pleistocene.