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Estimation of Suspended Sediment Concentrations during Deposition of Turbiditic Structureless Sandstones of the Middle Permian Brushy Canyon Formation, South New Mexico

Motanated, Kannipa *1; Tice, Michael M.1
(1) Geology and Geophysics, Texas A&M University, College Station, TX.

Spatial and size distributions of mineral grains with contrasting densities in massive sandstones (Bouma A divisions) of turbidites from the Middle Permian Brushy Canyon Formation were used to estimate suspended sediment concentrations of the depositing turbidity currents. Semi-quantitative elemental distributions in massive sandstone samples were estimated by x-ray fluorescence analytical microscopy. The results were then used to estimate the spatial and size distributions of zircon and feldspar grains. Hydraulic sorting of these grains resulted in characteristic vertical profiles of zircon grain abundance within the structureless sandstone divisions. Elemental maps show no grading in grain sizes of either heavy or light minerals. However, zircon grain abundance decreased upward within the structureless sandstone divisions relative to that of feldspar grains. These results suggest that zircon grains behaved as hydraulically coarse components of the grain population. Using different models of the effects of hindered settling on mixed grain populations, we estimate a volumetric sediment concentration greater than 20%. This implies that at least some Brushy Canyon Formation A divisions were deposited from hyperconcentrated suspensions

 

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California