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

Silicified tree trunks lie scattered in the nonh of Site BG-X where Kenyapithecus occurred. The Site GB-X is situated at 200 m north from the road, about 5 km WNW of Nachola (Ishida, 1984 ; Makinouchi et a/., 1984 ; Pickford et a/., 1984). There, silt and sand stones inserted between aphyric basalt lavas outcrop about 17 m thick and dip less than 10 degrees to west (Fig. I, 2). Silicified trunks are not found in situ, but they are estimated to occur from the siliceous beds upper than the lowest silt stone including Kenyapithecus fossils. Thirty five silicified trunks were numbered in 1984's survey. The chips of 26 of them were collected. Most of them are not completely preserved peripherally and big in diametre. The diametre of trunks is equal or more than the long width (Table I). However, 2 specimens are completely preserved peripherally and were pressed. and other 2 specimens branched. It appears that the bark is twisted and all trunks are same kind of tree. The annual rings are obscure, but some rings are observed. Thin sections from 16 specimens collected in 1984 and 4 specimens collected in 1982 were observed under microscope and were identified a single species of Family Euphorbiaceae, Subfamily Crotonoideae (Suzuki. 1987). It seems that the fossil beds of Site BG-X connect with the cherty limestone with silicified tree trunk (Baker, 1963) outcropping at the southeastern foot of a hill near Muruilem, 3 km northeast from Site BG-X. Baker described the geological mccession of Muruilem as follows: