Top > African Study Monographs > ASM Supplementary Issue Back Number > No.2 (1984)
Study of the Tertiary Hominoids and Their Palaeoenvironments in East Africa: 2

Edited by Hidemi ISHIDA, Shiro ISHIDA and Martin PICKFORD

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pp. 1-13

Outline of 1982 Survey in Samburu Hills and Nachola Area, Northern Kenya

Hidemi ISHIDA
Faculty of Human Sciences, Osaka University

ABSTRACT
   In 1982, the Japan-Kenya Expedition conducted geological, palaeontological and palaeoanthropological surveys in the Samburu Hills and Nachola area, north Kenya. In this paper, geography of the areas surveyed, and brief results of the survey, including discovery of fossil hominoids, are described.

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pp. 15-44

Geology of the Nachola Area and the Samburu Hills, West of Baragoi, Northern Kenya

Takeshi MAKINOUCHI
Faculty of Science and Technology, Meijo University
Takehiro KOYAGUCHI
Faculty of Science, University of Tokyo
Takaaki MATSUDA
Department of Geology, Himeji Institute of Technology
Hiromi MITSUSHIO
Faculty of Science, Kyoto University
Shiro ISHIDA
Faculty of Science, Kyoto University

ABSTRACT
   The Nachola area, about 15 km west of Baragoi, is underlain by Precambrian Basement Complex, above which come the Nachola Formation of Miocene age, undifferentiated, probably Pleistocene basalts and Alluvium, in ascending order. The Nachola Formation consists of basaltic lavas and clastic sediments. Kenyapithecus occurs in the Nachola Formation.
   The Samburu Hills, about 30 km west of Baragoi, are underlain by the Aka Aiteputh, Namurungule, Kongia, Nagubarat, and Tirr Tirr Formations, grey silts and fluviatile sediments, in ascending order. The Aka Aiteputh, Kongia, Nagubarat and Tirr Tirr Formations are mainly composed of accumulations of basaltic and trachytic lavas. The Namurungule Formation is of late Miocene age and consists of tuffaceous alternations of sand and mud with interactions of mud-flow deposits. The Samburu hominoid, a late Miocene hominoid fossil, occurs in the basal part of the Namurungule Formation.
   The lower part of the Nachola Formation is correlated with the lower part of the Aka Aiteputh Formation.
   Many faults, trending nearly N-S, cut the volcanics and sediments in the Samburu Hills and Nachola area. These faults form synthetic (western margin of the Samburu Hills) and antithetic fault systems accompanying the tectonic line along the eastern border of the Suguta valley.

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pp. 45-56

Fossiliferous Localities of the Nachola-Samburu Hills Area, Northern Kenya

Martin PICKFORD
National Museums of Kenya
Hidemi ISHIDA
Faculty of Human Sciences, Osaka University
Yoshihiko NAKANO
Faculty of Human Sciences, Osaka University
Hideo NAKAYA
Faculty of Science, Kyoto University

ABSTRACT
   In the four geographic/stratigraphic areas of the Samburu Hills and Nachola, west of Baragoi, Kenya, a significant number of fossiliferous localities was found. Nachola area is dated to the middle Miocene, the Namurungule Formation in Samburu Hill to the upper Miocene, Kongia area to the Mio-Pliocene and Holocene to the are near Suguta valley and in the drainage systems of the Samburu Hills to the Holocene. The site BG X in Nachola yielded a number of fossils provisionally assigned to Kenyapithecus. An important large hominoid specimen occurred in site SH 22 of the Namurungule Formation. Undoubtedly a great many additional sites await discovery.

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pp. 57-66

Fission-Track, K-Ar Age Determinations and Palaeomagnetic Measurements of Miocene Volcanic Rocks in the Western Area of Baragoi, Northern Kenya: Ages of Hominoids

Takaaki MATSUDA
Department of Geology, Himeji Institute of Technology
Masayuki TORII
Faculty of Science, Kyoto University
Takehiro KOYAGUCHI
Faculty of Science, the University of Tokyo
Takeshi MAKINOUCHI
Faculty of Science and Technology, Meijo University
Hiromi MITSUSHIo
Faculty of Science, Kochi University
Shiro ISHIDA
Faculty of Science, Kyoto University

ABSTRACT
   Miocene rocks in the west of Baragoi, northern Kenya, consist of the Nachola, Aka Aiteputh, Namurungule and Kongia Formations in ascending order. Two kinds of hominoids, Kenyapithecus and a large hominoid (Samburu hominoid), were found from the Nachola and Namurungule Formations, respectively, in summer 1982. Two fission-track and six K-Ar ages were determined on the volcanic rocks to clarify the ages of the hominoid fossils. Paleomagnetic reconnaissance was also conducted for the sake of magnetostratigraphic correlation. The ages of the Nachola, Aka Aiteputh, Namurungule and Kongia Formations were around 11, 13, 7 and 6.4 Ma, respectively. The ages of Kenyapithecus and Samburu hominoid are considered to be the Middle Miocene and Late Miocene, respectively.

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pp. 67-72

The Biostratigraphic Analyses of the Faunas of the Nachola Area and Samburu Hills, Northern Kenya

Martin PICKFORD
National Museums of Kenya
Hideo NAKAYA
Faculty of Science, Kyoto University
Hidemi ISHIDA
Faculty of Human Sciences, Osaka University
Yoshihiko NAKANO
Faculty of Human Sciences, Osaka University

ABSTRACT
   To examine and refine the preliminary K-Ar dating results, the faunas of Nachola and Samburu Hills are analyzed biostratigraphically. It is confirmed that the fauna of Nachola is in the pre-Hipparion stage (earlier than 10±0.5 m.y.). The fauna from the Namurungule Formation of Samburu Hills is the post-Hipparion stage (later than 10±0.5), not as advanced as that of Lukeino (6.5 m.y.) and most like those from Ngeringerowa and Nakali. Therefore, it is supposed that the age of the Namurungule fauna is 9±1 m.y..

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pp. 73-85

Fossil Anthropoids from Nachola and Samburu Hills, Samburu District, Kenya

Hidemi ISHIDA
Faculty of Human Sciences, Osaka University
Martin PICHFORD
National Museums of Kenya
Hideo NAKAYA
Faculty of Science, Kyoto University
Yoshihiko NAKANO
Faculty of Human Sciences, Osaka University

ABSTRACT
   During the 1982 expedition to Samburu Hills and Nachola, a number of hominoid fossils was found from two Miocene deposits. A small hominoid and a large late Miocene hominoid are contained in the fossils. The former most closely resembles Kenyapithecus africanus, and the latter may be ancestral to the extant African apes and hominoids, to gorilla alone, or not any living hominoids. The various alternatives are discussed.

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pp. 87-131

The Late Miocene Large Mammal Fauna from the Namurungule Formation, Samburu Hills, Northern Kenya

Hideo NAKAYA
Faculty of Science, Kyoto University
Martin PICKFORD
National Museums of Kenya
Yoshihiko NAKANO
Faculty of Human Sciences, Osaka University
Hidemi ISHIDA
Faculty of Human Sciences, Osaka University

ABSTRACT
   By the Japan-Kenya Expedition, more than 1145 late Miocene vertebrate fossils were collected from the Namurungule Formation in Samburu Hills, Northern Kenya in 1982.
   These fossils are assigned to at least 29 taxa of which 21 are mammals, including Hominoid, Tetralophodon, two kinds of Hipparion, Brachypotherium, Kenyapotamus, and Pachytragus.
   Quantitatively, the taxa of Hipparion are the most predominant. But gomphothere, bovid, rhinocerotid and giraffid fossils are approximately as common as each other at Namurungule. Suids, hippopotamids and carnivores seem to be uniformly rare as fossils at Samburu.
   In this paper, 19 taxa of mammals are described and discussed briefly.
   The Namurungule mammalian fauna is closer in age to Ngorora (c. 11 m.y.) than to Mpesida (7 m.y.) from Kenya, and this fauna is similar to the faunas of Samos and Pikermi (Vallesian).
   It seems that the abundance of Hipparion, giraffids, rhinocerotids and bovids suggests a woodland to savannah environment at or near Namurungule during the upper Miocene. We find very little evidence to suggest that there was forest in the vicinity at the time of deposition.

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pp. 133-139

Thryonomyid Rodent from the Late Miocene Namurungule Formation, Samburu Hills, Northern Kenya

Yoshida KAWAMURA
Department of Earth Sciences, Aichi University of Education
Hideo NAKAYA
Faculty of Science, Kyoto University

ABSTRACT
   Thryonomyid rodent collected from Late Miocene Namurungule Formation is described. The specimen is represented by a fragmental mandible with dP4 or P4 M1, M2 and M3. The tooth pattern with three transverse crest is fundamentally identical in each molar. Neither posterior arm of protoconid nor mesolophid is present in any molars. Absence of anteroconid is another important character of the present molars compared with the known species of Paraphiomys and Paraulacodus. This specimen is possibly assigned to Paraphiomys by the resemblance of tooth pattern, size and hypsodonty, but the specific determination is reserved in this paper. Additional materials are required to decide its definite taxonomic position. The occurrence of the present specimen suggests that Paraphiomys had survived up to Late Miocene in East Africa.

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pp. 141-145

Fossil Mollusca from the Samburu Hills, Northern Kenya

Martin PICKFORD
National Museums of Kenya

ABSTRACT
   Fossil molluscs are important indicators of past environmental conditions. 12 taxa of mollusca belonging to the period from Miocene to Holocene were collected mainly at the Samburu Hills in the north-central Kenya. The terrestrial snail fauna of the Kongia Formation is comparable with that from modern woodland to forest.

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pp. 147-179

Volcanic Rocks in the Samburu Hills, Northern Kenya

Takehiro KOYAGUCHI
Faculty of Science, University of Tokyo

ABSTRACT
   Volcanic rocks of the Samburu Hills are composed mainly of basaltic lava flows (ankaramite, olivine basalt and hawaiite) intercalated with differentiated rock lava flows and welded tufffs (trachyte and alkali rhyolite).
   Basaltic rocks of various ages, from Miocene to Recent, were collected from an area of 10 x 10 km2 (Suguta Area) and their petrography and petrochemistry are described. A decrease in degree of silica-undersaturation with time from alkali basalts to transitional basalts can be recognized. Successive decrease in depth of segregation of primary magmas can explain the temporal variation in chemical composition.

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