Clinker referred here as red and brick-looking burnt rocks found interbedded in the Upper Paleocene Cerrejon Formation is the result of spontaneous and natural combustion of coal seams in the recent geologic past. These rocks have been mapped, measured and characterized in the Cerrejon Coal Mine at La Guajira Peninsula (Colombia). These burnt rocks usually outcrop in irregular patterns as almost tabular bodies up to 100 m thick, thinning and pinching out below ground surface to depths up to 448 m. Mapping revealed that clinker is usually found near deformed zones, either faults or tight folds. Timing of spontaneous combustion seems to predate folding and faulting, but seems to postdate the development of the Cerrejon thrust fault and alluvial fan proceeding from the Perija Range. Clinker covers an area of around 2.9 x 10(6)m(2) with a volume of approximately 1.4 x 10(8) m(3). The calculation of the amount of heat released through coal burning indicates that complete combustion of 6.4 Mt of 26.4 x 10(6)J/kg coal would yield 17 x 10(13)J. (C) 2009 Elsevier B.V. All rights reserved.