The Tor-Casamanya Synclinorium is made up of silurian and devonian rocks. Every devonian formations, except Fonchanina Fm., of the Sierra Negra subfacies area are recognized in this syncline. The cartographie of this unit has allowed us to observe the Civis Fm. outcropping in the synclinorium central area and the Castanesa Fm. outcropping in whole study area. This devonian succession is more carbonated than the standard succession of this subfacies area. The geological cartographie and the best knowledge of devonian formations suggest that the structure of this synclinorium can be explained by the presence of folds with E-W trend. These folds belong to two different deformation phases. The first phase is characterized by north-verging folds, to which is associated the S1 foliations. These folds are found in the northern limb of synclinorium. The first folds are affected by south-verging folds. To these folds is associated the crenulation foliation (S2). This foliation is the main one of the Tor-Casamanya Synclinorium.