Cambrian formations from NW of Zafra are composed of pelitic sequences distributed along the Lower Cambrian (LC) up to the Middle-Upper Cambrian (MUC). These sedimentary sequences have a more sandstone component in LC with respect to MUC. Chemical characteristics of LC and MUC pelites present some differences, w ith hig her A l20 3 co ntents and lo w e r S i 0 2 in the M U C pelites. N o rm a liza tio n w it h respect to PAAS shows the sim ila rities b e tw ee n Cambrian pelites and this n o rm a liza tio n value.
Nevertheless, Cambrian pelites are characterized by lower CaO and Sr contents than PAAS. Major and trace element absolute values and ratios (Zr/Ni, Zr/Co, etc.) allow us to propose a mainly felslc source area for this Cambrian sequence in contrast to the more mafic source area for Precambrian pelites outcropping at this region