Granitos cámbricos de San Bernardino

In San Bernardino, both in town and along the lakeshore, pink to grey porphyritic granites crop out, fairly weathered, belonging to the Caapucú Magmatic Suite (Fanego type), of Early Cambrian age. They contain orthoclase, quartz and plagioclase, with smaller amounts of mica and dark minerals.

At the town’s lookout you can see the unconformable contact between that granite and the Ordovician sandstones of the Caacupé Group lying on top of it: a boundary that represents tens of millions of years missing from the record. San Bernardino’s beach sits in a valley that formed as the fault scarp on the eastern edge of the Asunción Rift retreated through erosion.