Top > African Study Monographs > ASM Supplementary Issue Back Number > No.17 (1992)
Study of the Tertiary hominoids and Their Palaeoenvironments in East Africa: 4
Palaeontological and Geological Surveys in the Sinda-Mogari Region of the Western Rift, Zaire

Edited by Hidemi ISHIDA and Kinya YASUI

p. 1


Hidemi ISHIDA & Kinya YASUI

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pp. 3-18

Geology of the Sinda-Mohari Region, Haut-Zaire Province, Eastern Zaire

Department of Earth Science, Meijo University
Department of Geology and Mineralogy, Yamaguchi University
Yoshihiro SAWADA
Department of Geology, Shimane University
Naoyuki KUGA
Department of Geology and Mineralogy, Kyoto University
Nobukazu KIMURA
Department of Geology and Mineralogy, Kyoto University
Department of Geology, Shimane University
Centre de Recherche en Sciences Naturelles
Munyololo wa YEMBA
Centre de Recherche en Geologiques Minières
Laboratory of Physical Anthropology, Kyoto University

   The Sinda-Mohari region is topographically divided into the Mutimba plateau, hilly land and Semliki Plain. The hilly land is underlain by Precambrain basement rocks, Sinda Beds, Higher Terrace Deposits, Middle Terrace Deposits, Lower Terrace Deposits, and Alluvium (Recent river floor deposits).
   The Sinda Beds are subdivided into the lower, middle and upper members. The lower member consists of clayey white coarse sand and yields such mammal fossils as Bovidae, etc. from the upper part. The middle member is characterized by alternating sand and mud beds. The upper member is composed of alternating thicker beds pf sand and mud and contains such mammal fossils as Predeinotherium, etc.
   Generally, the Sinda Beds gently dip south to southeast. Folds parallel the northern boundary faults. An inferred fault is drawn parallel just north of these folds.
   The context of geological phenomena from the older to the younger in this region is as follows: 1) formation of an extensive sedimentary basin by downwarping, 2) deposition of the Sinda Beds, 3)long-term denudation and peneplanation, 4) intense activity of the northern boundary faults and formation of the Higher Terrace Deposits, 5) activity of the southeastern boundary fault, 6) formation of the present Semliki Plain as the floor of the rift valley, 7) completion of the present drainage system, and 8) formation of the Middle and Lower Terrace Deposits within the deep valleys.

Key Words: Geology; Zaire; Rift valley; Sinda-Mohari; Shinda Beds.

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pp. 19-25

Mollusques Fossiles de la Region de Sinda a L'est du Zaire

Départment de Biologie, Centre de Recherche en Sciences Naturelles

   A study of the fossil moluscs has been carried out in eastern Zaire, mainly at Sinda in the Western Rift Valley (Lake Mobutu-Semliki Valley). The 1989 inventory of the collected molluscs had five speices (Caelatura bakeri, Mutela alata, Mutela rostrata, Iridina lepersonnei, and Aspatharia wissmanni) and the 1990 inventory, four species (Caelatura bakeri, Mutela alata, Mutela rostrata, and Aspatharia wissmanni). A biostratigraphic study will be conducted on these species after the conclusion of the geological study and the confirmation of our molluscs identification. From the available data, the fossil molluscs pertain to Miocene and Pliocene fauna.

Key Words: Fossil molluscs; Western Rift Valley; Eastern Zaire; Miocene; Pliocene.

pp. 27-47

New Late Tertiary Fish Fossils from the Sinda Region, Eastern Zaire

Vertebrate Section, Royal Museum of Central Africa, Belgium

   An assemblage of about 200 fish remains, recently collected from late Miocene early Pliocene deposits of the Sinda area, is described. Although the collection is small, several taxa not previously reported from these localities are included. Gymnarchus, Hydrocynus and Bagrus are new for the Sinda-Mogari ichthyofauna, whereas the previously doubtful presence of Clariidae is now confirmed by several finds, including one identifiable as Clarias. The discovery of three outer premaxillary teeth of Shungura Sindacharax along with the numerous Sindacharax lepersonnei specimens is surprising. The Shungura form is considered conspecific with Sindacharax lepersonnei.
   Other represented taxa are Synodontis, Auchenoglanis and Lates rhachirhinchus. Comparison of the ichthofauna from the oldest deposits (Ongoliba Beds) with that of the Middle Member of the Sinda Beds shows a decline in characiforms and an increase in siluriforms through time. Reconstruction of the former aquatic environment indicates a large and deep permanent water-body with shallow and marshy habitats at its margins.

Key Words:Palaeontology; Tertiary; Fish; Zaire.

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pp. 49-65

Fossil Turtles from the Neogene Strata in the Sinda Basin, Eastern Zaire

Department of Information, Teikyo University of Technology

   Fossil turtles collected from the Sinda Beds of eastern Zaire contain three families. They are Erymnochelys sp. of family Pelomedusidae, gen. et sp. Indet. of family Carettochelyidae, and gen. et sp. indet of family Trionychidae. Among them is the first known occurrence from Africa of carettochelyid, the pig-nosed turtle, Erymnochelys, the bigheaded side necked turtle, while once flourished in African during Tertiary, is restricted to Madagascar, today. All of these are presumed to have had aquatic habitat in rivers and lakes.

Key Words: Turtles; Neogene; Shinda; Carottochelyidae; Osteology; Paleoecology.

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pp. 67-85

Fossil Crocodilians from the Late Tertiary Strata in the Sinda Basin, Eastern Zaire

Riosuke AOKI
Nobi 2233, Yokosuka 239, Japan

   At least five crocodilian taxa could be recognized form the fragmental fossils obtained form the late Miocene to early Pliocene sediments of the Sinda basin, Haut-Zaire, Zaire. The first fossil record of Osteolaemus, the genus of extant dwarf crocodile, is evidenced by the two mandibular fragments. These fossil specimens are much larger than both extant species, but their mandibular morphology is more resembles that of the Central African species, O. osborni, rather than that of the West African species, O. tetraspis. Some other fossils could be identified as the remains of Crocodylus (Crocodile), Mecistops (african Long-nosed Crocodile or Senegal Gavial), Euthecodon (highly longirostral fossil form) and a highly longirostral form that lacks the remark of Euthecodon.

Key Words: Paleontology; Tertiary; Crocodilians; Osteolaemus; Zaire.

pp. 87-107


Department of Anatomy 1, Dokkyo University School of Medicine
Laboratory of Physical Anthropology, Kyoto University
Naoyuki KUGA
Laboratory of Paleontology, Kyoto University
Department of Biology, Centre de Recherche en Sciences Naturelles
Laboratory of Physical Anthropology, Kyoto University

    Since 1989, a geological and paleontological expedition has been carried out in the Zairean part of the Western Rift Valley. During two field seasons, more than 600 fossil remains were collected in the Sinda basin, Gaty, Haut-Zaire, mainly as surface finds. This fossil collection contains 52 mammalian fossils which comprise the following taxa; ? Agriotherium, four proboscidean groups such as Prodeinotherium, ?Anancus, Mammuthus subplanifrons and Stegodon kaisensis, two Rhinocerotidae, i.e., ?Aceratherium and Brachypotherium, ?Sivatherium, Hippopotamus, and a bovid. The Sinda fauna is composed of both Miocene and Pliocene mammals and suggest that the strata including the fossils are of late Miocene to early Pliocene in age. This fauna resembles that from the Nkondo formation which is located in the Ugandan side of the Western Rift Valley. The composition of the fauna from the Sinda area may indicate a different paleoenvironment (probably more humid) in this area from that in contemporary East Africa.

    Depuis 1989, une expedition geologique et paleontologique est realisee dans la partie zairoise de la branche occidentale du Rift. Durant deux saisons, plus de 600 restes fossiles ont ete collectele basin de Sinda, Gaty, haut-zaïre, principalement comme decouvertes de surface. Cette collection fossile contient 52 mammiferes fossiles qui comprennent les taxa suivant; ?Agriotherium, qutre groupes proboscidean tels que Prodeinotherium, ?Anancus, Mammuthus subplanifrons et Stegodon kaisensis, deux Rhinocerotidae par exemple, ?Aceratherium et Brachypotherium, ?Sivathrium, Hippopotamus, et un bovide. La faune de Sinda est composee des mammiferes du miocene et du pliocene et suggere que le strate inclus les fossils sont de l'age du miocene superieur au debut pliocene Cette faune ressemble celle de Nkondo formation qui est situee dans la partie ougandaise du Rift Occidental. La composition de la faune de l'aire de Sinda devra indique un paleoencironement different (probablement plus humide) dans cette aire de celui en l'est-aficain contemporain.

Key Words: Fossil mammals; Neogene; Western Rift Valley; Paleoenvironment; Eastern Zaire.

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