Volcanic rocks of Yavi Formation of Upper Jurassic?-Lower - Cretaceous age from the Media Luna Sinclinal (Huila Deparment) were studied. The petrography is described. It is present chemical analyses and his geotectonic position is discussed. The composition of the volcanic rocks indicates subduction-related magmatism. On the basis of geochemical interpretation of the the samples (piroclastic and lava flows) we conclude that they were generated on the margin of a plate in a backarc magmatic system.