The Neogene history of environmental change in the Kenya Rift : Contribution to deciphering of evolution from ape to early hominid

肯尼亚裂谷的新近纪环境变化史：对破译从猿到早期原始人类进化的贡献

• 批准号: 14253006
• 负责人: SAWADA Yoshihiro
• 金额: $ 20.97万
• 依托单位: Shimane University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (A)
• 财政年份: 2002
• 资助国家: 日本
• 起止时间: 2002 至 2005
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-14253006/
• 关键词: Human evolution; East Africa; Miocene; Geology; Radiometric age; Magnetostratigraphy; Palaeontrogy; Earth environment; 古地磁気年代; 洪水的火山活動; 地球化学; 古池磁気年代

The research results of the project are summarized as follows ;(1)On the basis of K-Ar ages and magnetostratigraphy, the Lukeino Formation (Fm) which yielded the earliest hominid Orrorin tugenensis accumulated between 6.0Ma and 5.7Ma.(2)The anorthoclase K-Ar ages from tuff layer yielding Nacholapithecus are 16.36±0.37Ma to 15.27±0.47Ma. Combined K-Ar ages and magnetostratigraphy of the Aka Aiteputh and Namurungule Fms in Samburu Hills, indicates that the hominoid fossil Sambrupithecus kiptalami occurs in the normal polarity zone, which is correlated with C4Ar.2n (ca.9.6Ma).Drastic environmental change occurred around 10Ma between the Aka Aiteputh Fm phase and subsequent Namurungure Fm phase which is sharply recorded in the sediment succession.(3)The age of lahar deposit layer yielding Kenyapithecus in the Fort Ternan area was dated 13.7 Ma based on the anorthoclase K-Ar and ^<40>Ar-^<39>Ar ages from phonolite lavas which sandwiched the fossil layer.(4)Earliest Late Miocene hominoid, which is very important for understanding on the evolution from great ape to human, and mammalian fossils were discovered from the lahar deposits of the Nakali Fm. The Nakali Fm consists mainly of lake and fluvial deposits with tuff and lapilli tuff beds including volcanic mud flow and pyroclastic flow deposits. Combined with the ^<40>Ar-^<39>Ar ages and magnetostratigrapy, the age of the Nakali Fm ranges from 10.1Ma to 9.8Ma (within Chron C5n.2n to C5n.1n).(5)Research of middle Miocene trachyte-phonolite flood volcanism in the whole Kenya rift ; geology, K-Ar age determination with magnetostratigraphy, petrography and geochemical characteristics.(6)Comparative geochemical studies on modern lacustrine sediments from the five lakes in the Kenya rift, and sedimentary rocks 16 to 5Ma.(7)Publications to journals and book (20 papers). The symposium was held at the annual meeting of Geological Society of Japan.

本项目的研究成果总结如下：(1)根据K-Ar年龄和磁地层特征，最早的古人类Orrorin tugenensis出现在Lukeino组（Fm）的沉积时间为6.0Ma ~ 5.7Ma。(2)产Nacholapithecus凝灰岩层斜长石K-Ar年龄为16.36±0.37Ma ~ 15.27±0.47Ma。结合Samburu Hills Aka Aiteputh组和Namurungule组的K-Ar年龄和磁地层学，表明Sambrupithecus kiptalami类人化石出现在正极性带，与C4Ar相关。2 n (ca.9.6Ma)。在10Ma前后，阿卡Aiteputh Fm期与随后的namurunure Fm期之间发生了剧烈的环境变化，这在沉积物演替中有明显的记录。(3)根据夹在化石层上的斜长岩K-Ar和^<40>Ar-^<39>Ar年龄，确定了Fort Ternan地区产Kenyapithecus火山泥流沉积层的年龄为13.7 Ma。(4)在Nakali组火山泥流沉积物中发现了最早的晚中新世古人类化石和哺乳动物化石，这些化石对认识类人猿到人类的演化具有重要意义。Nakali组主要由湖泊和河流沉积组成，其中包括凝灰岩和珍珠状凝灰岩床，包括火山泥流和火山碎屑流沉积。结合^<40>Ar-^<39>Ar年龄和磁地层特征，推测Nakali Fm的年龄范围为10.1 ~ 9.8Ma（在Chron C5n）。2n到5n， 1n)。(5)整个肯尼亚裂谷中新世中粗面岩-phonolite洪水火山作用研究；用磁地层学、岩石学和地球化学特征测定钾氩年龄。(6)肯尼亚裂谷五湖现代湖相沉积与16 ~ 5Ma沉积岩地球化学对比研究。(7)发表期刊、书籍（论文20篇）。研讨会在日本地质学会年会上举行。

项目成果

Depositional environment change of the lake Naivasha and Bogoria distributed in the Kenya Rift.

肯尼亚裂谷内分布的奈瓦沙湖和博戈里亚湖的沉积环境变化.

• 发表时间: 2005
• 期刊: Chikyu Monthly 27
• 作者: Tanaka;S.;Seto;K.;Mathai;S.;Nakamura;K.;Sawada;Y.
• 通讯作者: Y.

Refinement of the age of the Middle Miocene Fort Teman Beds, western Kenya, and its implications for Old World biochronology.

肯尼亚西部中中新世特曼堡床层年龄的细化及其对旧世界生物年代学的影响。

• 期刊: Comptes Rendus Geoscience (in press)
• 作者: Pickford;M.;Sawada;Y.;Tayama;R.;Matsuda;Y;Itaya;T.;Hyodo;H.;Senut;B.
• 通讯作者: B.

Late Cenozoic mammalian biostratigraphy and faunal change : Paleoenvironments of hominoid evolution and dispersal.in"Human Origins and Environmental Backgrounds(eds.Ishida,H.etal.)"

晚新生代哺乳动物生物地层学和动物区系变化：人科动物进化和扩散的古环境。在“人类起源和环境背景（编辑石田，H.等人）”

• 发表时间: 2006
• 作者: Nakaya;H.;Tsujikawa;H.
• 通讯作者: H.

The age and geological background of Nacholapithecus, Samburupithecus and Orrorin tugenensis, Kenya.

肯尼亚 Nacholapithecus、Samburupithecus 和 Orrorin tugenensis 的年龄和地质背景。

• 发表时间: 2006
• 期刊: Human Origins and Environmental Backgrounds (eds.Ishida, H.et al.)(Springer)
• 作者: Sawada;Y;Sakai;T.;Itaya;T.;Hyodo;M.et al.
• 通讯作者: M.et al.

Half graben filling processes in the early phase of continental rifting : The Miocene Namurungule Formation of the Kenya Rift

大陆裂谷早期的半地堑充填过程：肯尼亚裂谷的中新世 Namurungule 地层

• 发表时间: 2006
• 期刊: Sedimentary Geology in press
• 作者: Saneyoshi;M.;Nakayama;K.;Sakai;T.;Sawada;Y.;Ishida;H.
• 通讯作者: H.