Testing for the effects of sediment sorting on detrital-zircon age spectra by sampling multiple bedforms in single fluvial channels: Case studies from the Wood Canyon Formation (Terreneuvian) and Stirling Quartzite (Ediacaran), southeastern CA
Date of Award
Master of Science
Christopher M. Fedo
Robert D. Hatcher, Colin D. Sumrall
Multiple bedforms were sampled from single fluvial channels in the Neoproterozoic (Ediacaran) upper member of the Stirling Quartzite and the Cambrian (Terreneuvian) middle member of the Wood Canyon Formation, southeastern California. Sampling strategy was designed to determine if sorting of detrital zircon populations by their textural properties can affect detrital-zircon age spectra in fluvial sandstones. Four samples derive from the middle member Wood Canyon Formation and two samples come from the upper member Stirling Quartzite. Sandstone samples vary in textural characteristics: grain sizes sampled range from fine to coarse sand, sorting ranges from moderately well to poorly sorted, and sampled sedimentary structures include tabular planar cross-stratification, tabular tangential cross-stratification, and plane stratification. Wood Canyon Formation samples contain whole detrital zircons with similar grain size ranges, from ~80 μm [micrometer] to ~300 μm. Whole detrital zircons in samples of the Stirling Quartzite range in size: sample SQ1-JM contains zircons from 76 μm to 288 μm, whereas SQ5-JM contains grains from 67 μm to 183 μm. Age spectra from each of the fluvial channels are compared quantitatively using Kolmogorov-Smirnov (K-S) testing, overlap, and likeness. Kolmogorov-Smirnov testing classifies all samples from each channel as similar. No two samples from the same channel have an overlap of less than 73 %. Likeness values are greater than 72 % for samples from the same fluvial channel, indicating similarity. Comparing the size, sphericity, and roundness of whole detrital zircons to their ages, yields no general correlations. Sorting of sediments by their textural properties does not affect detrital-zircon age spectra in the Stirling Quartzite or Wood Canyon Formation, and is not a general rule in fluvial sediments. The main factor controlling the detrital-zircon age spectra of a sedimentary rock is its provenance. The findings confirm that the high-frequency Grenvillian peak in the middle member of the Wood Canyon Formation results from provenance, not sampling bias. Rift-flank uplift caused by the Ouachita rift in modern Texas and Oklahoma may have generated a pulse of Grenvillian detrital zircons entering westward-flowing braided-alluvial systems that is recorded in the middle member of the Wood Canyon Formation.
Muhlbauer, Jason Gerhard, "Testing for the effects of sediment sorting on detrital-zircon age spectra by sampling multiple bedforms in single fluvial channels: Case studies from the Wood Canyon Formation (Terreneuvian) and Stirling Quartzite (Ediacaran), southeastern CA. " Master's Thesis, University of Tennessee, 2015.