Top > African Study Monographs > ASM Supplementary Issue Back Number > No.5 (1987)
Study of The Tertiary Hominoids and Their Palaeoenvironments In East Africa: 3

Edited by Hidemi ISHIDA and Shiro ISHIDA


pp. 1-6

Outline the Third Season, 1984, of the Palaeoanthropological Expedition Team to the Samburu Hills and Nachola Areas, Northern Kenya

Hidemi ISHIDA
Faculty of Human Science, Osaka University

ABSTRACT
   In 1984, the Osaka University Team (the joint Japan-Kenya Palaeoanthropological Expedition to Samburu Hills, Kenya) conducted geological, palaeoantological anthropological surveys and excavations in the Samburu Hills and Nachola areas, Northern Kenya. In this paper, the results of the surveys, excavations and analyses of rocks and fossils are briefly described.

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pp. 7-26

Geology of the Neogene System in and around the Samburu Hills, Northern Kenya

Yoshihiro SAWADA
Faculty of Science, Kyoto University
Masaaki TATEISHI
Faculty of Science, Niigata University
Shiro ISHIDA
Faculty of Science, Kyoto University

ABSTRACT
   The Neogene System in and around the Samburu Hills, northern Kenya, is divided into seven main formations on the basis of stratigraphy and geochronology, which in ascending order are the Nachola, Aka Aiteputh, Namurugungule, Nanyangaten, Kongia, Nagubarat and Tirr Tirr Formations. The Nachola and Aka Aiteputh Formations of Makinouchi et al. (1984) have been redefined.
   The Nachola Formation, which is widely distributed along the Baragoi River, is the lowest part of the Neogene System and either unconformably overlies the Precambrian Basement Complex or is in fault contact with it. It consists mainly of basalts, phonolitic trachytes and their pyroclastics, and sediments. The Aka Aiteputh Formation conformably overlies the Nachola Formation and occurs in the Nachola area and the Samburu Hills. It is mainly composed of basalts intercalated with trachytes, trachytic pyroclastics and sediments. The Namurungule Formation consists chiefly of clastic sediments with intercalations of mud flow deposits and tuffs, and covers the Aka Aiteputh Formation. No structural gap between the Aka Aiteputh and Namurungule Formations is recognizable. The Nanyangaten Formation, consisting of basalt lavas, which is one of the "undifferentiated basalts" of Mainouchi et al. (1984), unconformably overlies the Nachola and Aka Aiteluth Formations.
   Kenyapithecus occurs in the Aka Aiteputh Formation at Site BG-X of the Nachola area (Ishida et al., 1984). The bed containing Kenyapithecus accumulated between 15.4 Ma and 12.8 Ma according to K-Ar dating of volcanic rocks (Itaya & Sawada, 1987). On the other hand, the Samburu hominoid fossil occurs in the Namurungule Formation (Makinouchi et al., 1984; Ishida et al., 1984) whose K-Ar age is between 10.8 Ma and 7.3 Ma (Itaya & Sawada, 1987).
   A major structural gap is recognized between the Namurungule and Nanyangaten Formations indicating that a significant tectonic disturbance in the (northern Kenya Rift) took place between about 10 Ma and 7 Ma based on geological data obtained by this work and Makinouchi et al. (1984), and geochronological data of Itaya & Sawada (1987).

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pp. 27-45

K-Ar Ages of Volcanic Rocks in the Samburu Hills Area, Northern Kenya

Tetsumaru ITAYA
Okayama University of Science
Yoshihiro SAWADA
Faculty of Science, Kyoto University

ABSTRACT
   44 volcanic rocks collected systematically from the Samburu Hills area, west of Baragoi, Northern Kenya were dated with the K-Ar age determination method to examine the chronology of fossil hominoids discovered in the Japan-Kenya Expedition, 1982. The K-Ar data suggest that Samburu hominoids at the site SH-22 are from 7.1±0.5 to 10.7±0.6 Ma in age and the Kenyapithecus at the Site BG-X from 12.6±0.6 to 14.9±0.6 Ma in age.

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pp. 47-58

Paleomagnetism of Miocene Rocks in the Western Area of Baragoi, Northern Kenya

Tadashi NAKAJIMA
Faculty of Education, Fukui University
Masayuki TORII
Faculty of Science, Kyoto University

ABSTRACT
   A total of 22 reliable paleomagnetic data has been obtained from Miocene rocks in this area. The magnetic polarity sequence is divided into six magneto-zones, which are tentatively correlated with the geomagnetic reversal time scale. The Kenyapithecus horizon is assigned to a normal epoch in the period between 14 Ma and 12 Ma. The VGPs obtained from this area show the deviations in the direction of the "far-sided and right-handed" effect from the geographical pole.

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pp. 59-77

Sedimentary Facies of the Miocene in the Samburu Hills, Northern Kenya

Masaaki TATEISHI
Faculty of Science, Niigata University

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pp. 79-129

Additional Large Mammalian Fauna from the Namurungule Formation, Samburu Hills, Northern Kenya

Hideo NAKAYA
Faculty of Education, Kagawa University
Martin PICKFORD
Collège de France, Paris
Kinya YASUI
Faculty of Science, Kyoto University
Yoshihiko NAKANO
Faculty of Human Sciences, Osaka University

ABSTRACT
   Some 1150 late Miocene vertebrate fossils were collected by the Japan-Kenya Expedition from the Namurungule Formation in the Samburu Hills, Northern Kenya. The Namurungule mammalian local fauna has simillarities to late Miocene Eurasian faunas from Samos and Pikermi (Greece), Maragheh (Iran), and the Nagri and Dhok Pathan Formations of the Siwalik Hills (India). This similarity indicates mammalian interchanges between Eurasian and Africa during the late Miocene. The svanna fauna of the Namurungule Formation differs completely from the earilier Aka Aiteputh Formation fauna, which indicates a woodland enviroment (Pickford et al. 1984). This great change in the mammalian fauna of the East African late Miocene coincided with the beginning of the opening of the Gregory Rift.

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pp. 131-139

Additional Materials of the Late Miocene Rodents from the Namurungule Formation in the Samuburu Hills, Northern Kenya

Yoshinari KAWAMURA
Aichi University of Education
Hideo NAKAYA
Faculty of Education, Kagawa University

ABSTRACT
   Two specimens of thryonomyids newly collected from the Late Miocene Namurungule Formation are described. One is a grooved upper incisor, which is referred to Paraulacodus sp. Another is a molar with three transverge lophs, whose definite taxonomic position can not be determined. The similarity in the rodent faunas between the Namurungule Formation and the Ch'orora Formation of Ethiopia is suggested. It is concordant with the approximate coincidence of the radiometic ages of both formations.

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pp. 141-154

The Middle Miocene Fauna from the Nachola and Aka Aiteputh Formations, Northern Kenya

Martin PICKFORD
Collège de France, Paris
Hidemi ISHIDA
Faculty of Human Sciences, Osaka University
Yoshiko NAKAYA
Faculty of Human Sciences, Osaka University
Kinya YASUI
Faculty of Science, Kyoto University

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pp. 155-156

Fossil Terrestrial Gastropods from the Namurungule Formation, Kenya

Martin PICKFORD
Collège de France, Paris

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pp. 157-161

Occurrence of Silicified Tree Trunks from Site BG-X, West of Baragoi, Kenya

Shiro ISHIDA
Faculty of Science, Kyoto University

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pp. 163-167

A Preliminary Description on Fossil Woods Collected from Site BG-X, West of Baragoi, Kenya

Mitsuo SUZUKI
Department of Biology, College of Liberal Arts, Kanazawa University

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pp. 169-174

Excavation at the Fossil-Hominoid-Bearing Locality, Site-SH22 in the Samburu Hills, Northern Kenya

Kinya YASUI
Faculty of Science, Kyoto University
Yoshihiko NAKANO
Faculty of Human Sciences, Osaka University
Hidemi ISHIDA
Faculty of Human Sciences, Osaka University

ABSTRACT
   An excavation has been carried out at the SH22 locality where a fossil of a large hominoid (KNM-SH-8531) was found in 1982. This site is located in the Samburu Hills, northern Kenya and dated back to upper Miocene. During the 1984 field season, a large number of new fossils were recovered at this locality. These fossils and sedimentological analysis revealed that the fossil bed at the SH22 locality may be a marginal deposit of an abandoned channel on a dried lake floor.

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