University of Tennessee, Knoxville TRACE: Tennessee Research and Creative Exchange Masters Theses Graduate School 12-2015 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 Jason Gerhard Muhlbauer University of Tennessee - Knoxville, [email protected] Follow this and additional works at: https://trace.tennessee.edu/utk_gradthes Part of the Sedimentology Commons Recommended Citation 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. https://trace.tennessee.edu/utk_gradthes/3552 This Thesis is brought to you for free and open access by the Graduate School at TRACE: Tennessee Research and Creative Exchange. It has been accepted for inclusion in Masters Theses by an authorized administrator of TRACE: Tennessee Research and Creative Exchange. For more information, please contact [email protected]. To the Graduate Council: I am submitting herewith a thesis written by Jason Gerhard Muhlbauer entitled "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." I have examined the final electronic copy of this thesis for form and content and recommend that it be accepted in partial fulfillment of the requirements for the degree of Master of Science, with a major in Geology. Christopher M. Fedo, Major Professor We have read this thesis and recommend its acceptance: Robert D. Hatcher, Colin D. Sumrall Accepted for the Council: Carolyn R. Hodges Vice Provost and Dean of the Graduate School (Original signatures are on file with official studentecor r ds.) 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 A Thesis Presented for the Master of Science Degree The University of Tennessee, Knoxville Jason Gerhard Muhlbauer December 2015 Copyright © 2015 by Jason Gerhard Muhlbauer All rights reserved. ii ACKNOWLEDGEMENTS Completion of this study required the assistance and aid of many people and institutions. Dr. Chris Fedo provided constant inspiration, guidance, and instruction as my advisor. Committee members Dr. Bob Hatcher and Dr. Colin Sumrall helped to review my work and progress. Dr. G. Lang Farmer granted access to NSF funding and instrument time. Detrital-zircon geochronology was completed at the University of Arizona in the Arizona LaserChron Center, where Dr. George Gehrels, Mark Pecha, and several operators provide reliable services and support. Erin Donaghy aided in the operation of geochronology equipment and in logistical concerns at the University of Arizona. Graduate students at the University of Tennessee, friends, and family offered support and confidence during the completion of my degree. The National Science Foundation and the Geological Society of America funded this study. iii ABSTRACT 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 iv 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. v TABLE OF CONTENTS 1. INTRODUCTION .......................................................................................................... 1 2. STRATIGRAPHIC SEQUENCE SELECTION ............................................................ 8 2.1 Reasoning behind choice of formations .................................................................... 8 2.2 Geologic setting ........................................................................................................ 8 2.2.1 Stirling Quartzite ................................................................................................ 9 2.2.2 Wood Canyon Formation ................................................................................. 11 3. TECHNICAL APPROACH AND METHODS............................................................ 13 3.1 Sampling strategy.................................................................................................... 13 3.2 Sample preparation ................................................................................................. 16 3.2.1 Importance of sample sedimentology .............................................................. 16 3.2.2 Contamination assessment ............................................................................... 16 3.2.3 Limiting potential bias during zircon recovery ................................................ 17 3.3 Detrital-zircon U–Pb geochronology ...................................................................... 18 3.4 Comparative statistical methods ............................................................................. 19 4. SAMPLE DESCRIPTIONS.......................................................................................... 23 4.1 Middle member Wood Canyon Formation ............................................................. 23 4.1.1 Sample EP01-B ................................................................................................ 23 4.1.2 Sample EP02-A ................................................................................................ 23 4.1.3 Sample EP02-C ................................................................................................ 23 4.1.4 Sample EP03 .................................................................................................... 27 4.2 Upper member Stirling Quartzite............................................................................ 27 4.2.1 Sample SQ1-JM ............................................................................................... 27 4.2.2 Sample SQ5-JM ............................................................................................... 28 5. DETRITAL-ZIRCON CHARACTERISTICS ............................................................. 29 5.1 Middle member Wood Canyon Formation ............................................................. 29 5.2 Upper member Stirling Quartzite............................................................................ 29 6. U–Pb GEOCHRONOLOGY ........................................................................................ 32 6.1 Middle member Wood Canyon Formation ............................................................. 32 6.2 Upper member Stirling Quartzite............................................................................ 34 7. STATISTICAL COMPARISON OF AGE SPECTRA ................................................ 35 7.1 Middle member Wood Canyon Formation ............................................................. 35 7.2 Upper member Stirling Quartzite............................................................................ 40 8. TEXTURAL PARAMETERS AND AGE RELATIONSHIPS ................................... 41 8.1 Grain size