The sedimentary succession exposed in a 386 sq. Ian Geba basin represents one of thickrnaccumulations of continental sediments that are commonly known to associate the EthiopianrnTertiary volcanics. The succession is a coal and oilshale bearing, and comprises about 150mrnConglomerate, sandstone, siltstone, mudstone, reworked tuff, oilshale and coal sediments.rnThey are deposited in an east-west trending intracratonic rift basin, that may be evolvedrnlocally, from other regional contemporaneous tectonic episodes between Middle Oligocenernand Early Miocene. The whole sedimentary sequence has been distinguished into five majorrnsedimentological units correlable with depositional environments ranging from fluviatiles tornlacustrine. Under fluvial conditions a number of coal seams are formed in flood plain. Underrnlacustrine condition, several thick coal seams have been formed in marshy areas, developed atrnthe margin of the lakes.rnGenerally, the coal beds range in thickness from few tens of centimeters to about 4.0 meters.rnChemically, they are high ash and medium sulfur coals. The maceral study reveals thatrnhuminite dominated the organic forms of Geba coals(>85%), with high proportion ofrnhumocollinite and minor humodetrinite sub groups. Humotelinite sub group is markedly rare.rnLow inertinite Â«7%) and considerable liptinite, as high as 23%, are main features of therncoals. The overall petrographic aspect of the coals suggests humic origin, possibly underrnshallow water condition. Reflectances measured on the huminite range from 0.32-0.39%R.rnThis indicates an ASTM rank ranging from lignite to lower boundary of Sub bituminous.