We report the results of a petrological and structural study on the volcanic rocks from the Los Santos de
Maimona Carboniferous basin (Ossa-Morena Zone, SW Spain). This basin is ca. 25 km in length and up to
3 km wide being limited by strike slip faults oriented NW-SE. The volcanic deposits occur interbedded
with shallow platform sediments of Visean age which reflect a regression regime. The volcanic rocks are
the result of both effusive and explosive volcanic activity. Effusive periods account for the formation of
moderately alkaline lava flows, whereas the explosive events resulted in fall deposits and pyroclastic flows.
The volcanic center could be situated close to the Los Santos de Maimona site, where it might give rise to
a strato-volcan structure. While surface deposits are not excluded, it appears that most volcanic rocks in
this area were deposited in a shallow marine environment