Pyroclastic deposits of the Bambouto volcano (Cameroon Line, Central Africa): evidence of an initial strombolian phase

The Bambouto Mountains, resting on a large Pan-African metamorphic horst of the Cameroon Line, lie between 9°57′ and 10°15′E and 5°27′ and 5°48′N in Western Cameroon. Two imbricated calderas (13 × 8 km) are located at its summit area. This volcanic region is made up of a complex sequence of basalt, trachyte and phonolite lava flows and ignimbrites. New field investigations show that the ignimbrites, formerly considered as the first products of volcanic activity, have incorporated xenoliths of basaltic scoriae in the southern flank of the massif and of trachyte within the calderas. These observations are consistent with the occurrence of early volcanic phases: strombolian and pre-ignimbritic in the south, trachytic and penecontemporaneous with the ignimbrites within the calderas.