Geology and Mineral Resources of Paraguay A Reconnaissance

52 GEOLOGY AND MINERAL RESOURCES OF PARAGUAYFIGURE 43. Outcrops of limestone of Itapucumi series, Cambrian and Ordovician age, on the east bank of the Rio Paraguay just south of Valleml.Joints in the rock are characterisically enlarged close to river level; some evidence of horizontal niching by the river can also be seen. Patcheson the distant water surface are floating islands (camalotes) of flowering water plants.(1865) describes two dolomitic marbles from Itapuguazu.This locality is not shown on modern maps,but the name clearly refers to one of the more prominentcliffs along the east bank of the river. One marble describedby DuGraty is rosy white and contains a littlemore than 93 percent calcium and magnesium carbonate;the other is nearly white but lightly veined withrose, and contains 99 percent combined carbonates.A report on "Concurrencia del Banco Agricola delParaguay" (Anon., 1911) reports that President MariscalLopez (circa 1860) had a table made of all classesand colors of Paraguayan marble, and sent it to NapoleonIII of France, who had it prominently displayedin the Tuilleries for a long time.The rocks of the Itapucumi series appear to be unfossiliferousand their age is unknown. The series isthought by Almeida (1945) and Harrington (1950) tobe probably equivalent to the Corumba series of MatoGrosso, Brazil. Both authors trace the history ofattempts to date this series and conclude that it, andhence the Itapucumi series is probably of OrdovicianThe cliffs along the river are deeply notched at andnear the present water level, but not above it. Moreover,joints in the limestone, though tight in the higherparts of the cliffs, are enlarged by solution to tentshapedcaves at river level. (See p. 78.)Except along the cliffs just mentioned, the Itapucumilimestone beds are weathered to a dark-gray to blackclayey soil that is commonly less than 2 meters thickand is characterized by many outcrops of limestone andby poor drainage. On the uplands the soils supportluxuriant vegetation, but in the poorly drained lowlandsthe principal tree is the black or carandai palm.Were it not for the clayey texture and poor drainagethe soils would doubtless be among the best agriculturalsoils of Paraguay, despite their thinness, for they arethe only ones that contain lime in any quantity.The limestone forms the basis of a considerable limeindustry, as well as providing raw material for thecountry's cement plant. In addition to these uses,there is a strong possibility that many of the rockscould be used for attractive ornamental stone. Manysmall kilns, which supply nearly all the lime used in thecountry, are scattered along the limestone cliffs on theeast bank of the Rio Paraguay. This industry is saidby Boettner (1947) to have been begun between 1825and 1840, under the regime of President Francia, whoeffectively closed the country to all foreign commerce.