The sedimentology and alluvial architecture of a large braid bar, Río Paraná, Argentina

SMITH G, SAMBROOK; ASHWORTH P,; BEST, J; LUNT I,; ORFEO, O.; PARSONS D,

JOURNAL OF SEDIMENTARY RESEARCH

Society for Sedimentary Geology

Lugar: Tulsa; Año: 2009 p. 629 - 642

1073-130X

Despite the importance of large rivers as conduits for the transfer of water and sediment to depositional basins, the alluvial architecture of their deposits is poorly understood. This paper presents ~ 30 km of Ground Penetrating Radar (GPR) data from a mid-channel bar in the 6th largest river in the world, the Río Paraná, Argentina. GPR profiles (up to 12 m below the bar surface) were collected from a 3 km long x 1 km wide sandy braid bar on a grid with 200 to 400 m spacing. Two facies dominate the sedimentary architecture. The principal facies (~83%) is trough and planar cross-strata related to the migration of dunes, with the thickness of the cross-strata decreasing towards the bar surface. The second significant facies (~15%) is high-angle (generally 10o-20o) strata that typically forms by accretion at the bar margins or bartail. Clay drapes (