Quartz geodes of cauliflower type together with some nodular chert have been recorded from Campanian carbonate sediments in the south limb of the Miranda-Treviho Synclinorium. Their m orphology and the e xiste n ce o f anhydrite laths in clu d ed in megaquartz crystals, lead us to think in an origin clearly related to ancient anhydrite nodules which were produced by percolation of brines associated to an important sedimentary gap. The synsedimentary activity of the very close Pehacerrada diapir could play a decisive role in the formation of quartz geodes