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We report five Oligocene-early Miocene pollen assemblages from the Loperot-1 exploration well drilled in the semi-desert Lokichar Basin (latitude 02 degrees 21’ 46.15"N, longitude 35 degrees 52’23.47" E, ground elevation 615 m above MSL), near Lake Turkana in northern Kenya. They represent the second oldest plant microfossils so far recovered from East Africa and add significantly to the Paleogene-Neogene tropical African fossil plant record. The Loperot pollen indicate a mosaic environment of semi-deciduous forest and humid woodland whose floristic composition presents strong affinities with the vegetation occurring today in the Guinea-Congolia/Zambezia phytogeographical transition zone, with a rainfall more than 1000 mm/year and a well defined dry season. The weak representation of Poaceae and herbaceous taxa characteristic of grassland, dry bushland or savanna and the abundance of shade tolerant plants such as ferns all point to a vegetation composed to a variety of communities with closed forest formations predominant. The lack of typical temperate mountains elements, mainly Podocarpus and Juniperus today widespread on the East African highlands, indicates that the geography of the region was different from that of today. The plateaux or uplands adjacent to the Lokichar basin were probably still not high enough during this period of early rifting in East Africa to support the temperate coniferous forests characteristic of the Plio-Pleistocene. (c) 2006 Elsevier B.V. All rights reserved.