Le bois petrifies de la plaine de la haute Rusizi (Burundi)

Abstract

THE DISCOVERY OF PETRIFIED FOSSILS IN THE HIGH RUSIZI PLAIN (BURUNDI)Palaeobotanical research in Central Africa is still very fragmentary. In Burundi, apart from the very classical and abundant stromatolites of the Mosso (in the south of the country), Sah (1967) has indicated the occurrence of vegetal debris in the fluviolacustrian sediments o f the mid-upper Rusizi plain. These fragments have never been identified, but a study of the pollen grains found in sedimentary layers of the same age has revealed some features of the vegetation and of the climate prevailing in the Upper Neogene period.In November 1978 we discovered in north-western Burundi a deposit of petrified trunks of exceptional size. These fossils had been exposed a short time previously when a small quarry was established. The deposit contained four trunks, two of which were large: length, 1 m; diameter, 90 cm; weight, more than 1 000 kg.Initial macro and submicrospic examination of fragments showed an anatomical structure similar to the structure of some fossils described in Kivu (Zaire) and belonging to the family Caesalpiniaceae.Samples were sent to Tervuren (R. Dechamps) and to Liêge (Mrs Demaret) and their joint studies revealed that these trunks belong to the genus Julbernardia and probably to J. globiflora. Their age would be about 1 200 000 years.Since then, other trunks have been found (at least ten). According to our study, it is concluded that they have a very different structure from those of the previous specimens. Samples were sent to Tervuren and to Liêge for further study and the conclusions from the specialists should be available very soon.