| 依据Pulleniatina的旋向变化划定更新统下界─-以台湾二仁溪剖面为例 |
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| 引用本文： | 谢凯旋,洪崇胜.依据Pulleniatina的旋向变化划定更新统下界─-以台湾二仁溪剖面为例[J].第四纪研究,1999,19(6):549-555. |
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| 作者姓名： | 谢凯旋 洪崇胜 |
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| 作者单位： | [1]经济部中央地质调查所 [2]中央研究院地球科学研究所 |
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| 基金项目： | 国家科学委员会经费NSC87－2119－M－001－006 |
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| 摘 要： | 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。
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| 关 键 词： | 有孔虫 Pulleniatina 旋向变化 更新统下界 |
| 收稿时间： | 1998-08-26 |
RECOGNITION OF THE PLIOCENE-PLEISTOCENE BOUNDARY BASED ON PULLENIATINA COILING CHANGE: A CASE STUDY OF THE ERHJEN-CHI SECTION,SOUTHWESTERN TAIWAN |
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| Institution: | 1. Central Geological Survey, P. O. Box 968, Taipei;
2. Institute of Earth Sciences, Academia Sinica,P. O. Box 1-55, Nankang, Taipei |
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| Abstract: | Traditionally, the first appearance datum （FAD） of planktic foraminiferGloborotalia truncatulinoides has been widely used as a reliable indicator of thePliocene-Pleistocene （P-P） boundary in marine-deposited sequence. However, recentstudies indicate that this datum is diashronous, because the FADs of Gt.truncatulinoides in the Indo-Pacific betwseen about 15°S and 40° S is earlier （2.6～2.7MaB.P.） than that in the equatorial Pacific （2.OMaB.P.）. Moreover, the P-P boundarybased on the commonly accepted FAD （2.0 MaB. P.） of Gt. truncatulinoides isinconsistent with the boundary according to the FAD （1.67～l.70MaB. P.） ofcalcareous nannofossil Gephyrocapsa oceanica s.l. This inconsistency is remarkable inthe conti nental margin sequence where high sedimentation rate resulted in a largestratigraphic interval between the FADe of Gt. truncatulinoides and Gephyrocapsaoceanica s.1. For instances, the interval between these two FADs is about 500m and1 300m from two rapidly deposited sequences of Taiwan. In this study, wedemonstrate that in the western part of Erhjen-chi section of southwestern Taiwan, thelast coiling change （from sinistlal to dextral） in the tests of planktic foraminiferPulleniatina is almost coeval with the FAD of G. oceanica s. l. Therefore, thePulleniartina coiling change could be used as a very useful datum for the P-Pboundary in Planktic foraminiferal biostratigraphy. |
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| Keywords: | foraminifera Pulleniatina coiling change Pliocene-Pleistocene boundary |
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