THE GEOCHEMICAL SIGNATURE OF SUSPENDED SEDIMENTS IN THE PARANA RIVER BASIN: IMPLICATIONS FOR PROVENANCE, WEATHERING AND SEDIMENTARY RECYCLING

CAMPODÓNICO, V; PASQUINI A. I; GARCÍA M.G

CATENA

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2016 vol. 143 p. 201 - 214

0341-8162

The Paraná River basin is oneof the largest hydrological systems in South America. The present study focuseson the mineralogical and chemical composition of the suspended sedimentsexported by the Paraná River to the Atlantic Ocean, with the aim of analyzingtheir provenance, the chemical weathering signature and the likelihood ofsedimentary recycling. The particulate matter of the Middle Paraná River andits main tributaries (i.e., the Paraguay and the Upper Paraná rivers) is mostlycomposed of quartz, plagioclase, K-feldspar, and clays, such as illite andkaolinite. Different geochemical approaches indicate that the suspendedsediments transported by the Paraná River preserve the chemical signature ofits sources and its composition is not significantly modified during transport.These sediments are mainly supplied by acidic arc sources located in the Andeanheadwaters of the Bermejo and Pilcomayo rivers (and transported by the ParaguayRiver); and by tholeiitic basalts outcropping in the headwaters of the UpperParaná River. The incomplete mixing of both the main tributaries produces atransverse geochemistry geochemical asymmetry in the particulate material of theMiddle Paraná River, which was detected ~32 km downflow the confluence. Thesuspended load transported by the Paraguay River (which includes thecontributions from the Bermejo and Pilcomayo rivers) indicated indicatesincipiently to moderately weathering, whereas the particulate matter exportedby the Upper Paraná River reveals a higher degree of chemical alteration. Thisis the result of the different lithology and climatic regimens that prevail inthe headwaters of both tributaries. The weathering signature of the MiddleParaná River´s suspended load resembles that of the Paraguay River, which inturns supplies most of the particulate matter through the Bermejo River. Thiswork also shows that the suspended load exported by the Paraná River basin hasa mixed origin, where the chemical signatures from young materials derived fromundifferentiated volcanic rocks, and from recycled materials affected byintracrustal differentiation can be distinguished.