The geochemical characteristics of the Paran´a River

PEDRO J. DEPETRIS,1* JEAN-LUC PROBST,2 ANDREA I. PASQUINI1 AND DIEGO M. GAIERO3†

HYDROLOGICAL PROCESSES

Wiley InterScience

Año: 2003 p. 1267 - 1277

0885-6087

Most water in the Paran´a River drainage basin is supplied by the tropical Upper Paran´a (over 60% of the total annual water discharge, 550 km3
. The total suspended solids (TSS) load (c. 80 ð 106 t year
1
, however, is essentially furnished (50–70%) by the mountainous, arid and mostly sediment-mantled upper Bermejo River drainage basin. This characteristic suggests that the Paran´a River solid load (TSS, 600 km upstream from the mouth) is largely recycled sedimentary material, whose discharge-weighted mean chemical index of alteration is c. 71. The extended UCCnormalized multi-elemental diagrams are similar to those of other world rivers. Nevertheless, the detailed inspection of UCC-normalized rare earth element (REE) ‘spidergrams’ reveals a lithological source for the Paran´a River TSS that might be compatible with either tholeiitic flood basalts (widespread in the upper drainage) or with young Andean intermediate volcanic rocks. In view of the Bermejo River’s dominant role as a sediment contributor, we feel that the signature preserved in the Paran´a’s TSS is the latter. Conversely, the Uruguay River TSS REE signature is certainly determined by the extensive weathering products of Jurassic–Cretaceous tholeiitic basalts. Copyright  2003 John Wiley & Sons, Ltd.3
. The total suspended solids (TSS) load (c. 80 ð 106 t year
1
, however, is essentially furnished (50–70%) by the mountainous, arid and mostly sediment-mantled upper Bermejo River drainage basin. This characteristic suggests that the Paran´a River solid load (TSS, 600 km upstream from the mouth) is largely recycled sedimentary material, whose discharge-weighted mean chemical index of alteration is c. 71. The extended UCCnormalized multi-elemental diagrams are similar to those of other world rivers. Nevertheless, the detailed inspection of UCC-normalized rare earth element (REE) ‘spidergrams’ reveals a lithological source for the Paran´a River TSS that might be compatible with either tholeiitic flood basalts (widespread in the upper drainage) or with young Andean intermediate volcanic rocks. In view of the Bermejo River’s dominant role as a sediment contributor, we feel that the signature preserved in the Paran´a’s TSS is the latter. Conversely, the Uruguay River TSS REE signature is certainly determined by the extensive weathering products of Jurassic–Cretaceous tholeiitic basalts. Copyright  2003 John Wiley & Sons, Ltd.c. 71. The extended UCCnormalized multi-elemental diagrams are similar to those of other world rivers. Nevertheless, the detailed inspection of UCC-normalized rare earth element (REE) ‘spidergrams’ reveals a lithological source for the Paran´a River TSS that might be compatible with either tholeiitic flood basalts (widespread in the upper drainage) or with young Andean intermediate volcanic rocks. In view of the Bermejo River’s dominant role as a sediment contributor, we feel that the signature preserved in the Paran´a’s TSS is the latter. Conversely, the Uruguay River TSS REE signature is certainly determined by the extensive weathering products of Jurassic–Cretaceous tholeiitic basalts. Copyright  2003 John Wiley & Sons, Ltd. 2003 John Wiley & Sons, Ltd.