Geology of Paraguay Basin. These tholeiites were erupted in the Early Cretaceous in association with the initial opening of the South Atlantic. The Cretaceous volcanism did also created minor outcrops of potassic alkaline volcanics in a graben structure developed between Asunción and Villarrica and in Amambay Department. Cretaceous volcanism did also left small units of sodic alkaline rocks in Misiones Department in southern Paraguay. Geology of Paraguay The country of Paraguay lies geologically at the borderzone between several cratons. Due to thick Cenozoic sediment cover and regolith development few outcrops are available in Paraguay. East of Paraguay River that Precambrian and Early Paleozoic
San Pedro Department, Paraguay San Pedro Department, Paraguay San Pedro () is a department of Paraguay. The capital is the city of San Pedro de Ycuamandiyú. During the 17th and 18th centuries there was even greater political and population instability than in Concepción. The Mbayá and Payagua native tribes threatened all the area between the Ypané (in the north) and Manduvirá (in the south) Rivers and the valley by the Jejuí River. In 1660 the natives revolted in Arecajá against the postal parcel system, causing the disappearance of this town. To help regenerate this area, the Missions San Estanislao (1749), Villa del Rosario (1786)