FRACTIONATION OF RARE EARTH ELEMENTS DURING SOIL FORMATION ALONG FEATHER RIVER BASIN HILL SLOPES IN THE CALIFORNIA SIERRA NEVADA

FRACTIONATION OF RARE EARTH ELEMENTS DURING SOIL FORMATION ALONG FEATHER RIVER BASIN HILL SLOPES IN THE CALIFORNIA SIERRA NEVADA Rare earth element (REE) mobility in surficial systems is poorly understood making their use as geochemical tracers a debated topic. Using soil data, this study examines how REEs fractionate as rock weathers into soil along the Middle Fork Feather River in Northern California. An erosional signal propagating through the basin was studied by comparing the traditional methods of REE normalization with the elemental loss method based on mass balance calculations known as tau (τ). Soil samples were collected along three differentially eroded hill slopes. The application of the traditional method of REE normalization showed chemical fractionation in the saprolite, however, the details of profile variation were unclear and difficult to interpret. The mass-balance method, which uses Zr as an immobile element, also portrayed REE fractionation within the saprolite. Results show that the bedrock REE signature is altered as the bedrock weathers to form saprolite and undergoes further alteration as the saprolite weathers to produce overlying soils. Most chemical weathering and chemical mass loss occurred in the saprolite, which corresponds to the fractionation observed in the saprolite. Considering the magnitude and variable changes of REEs in the first meter of rock-to-soil weathering, studies seeking to use REEs as tracers over longer spatial scales should also consider sampling and testing weathered material, such as saprolite, as sedimentary source instead of unweathered bedrock alone. Tiffany Ann Steinert May 2016 FRACTIONATION OF RARE EARTH ELEMENTS DURING SOIL FORMATION ALONG FEATHER RIVER BASIN HILL SLOPES IN THE CALIFORNIA SIERRA NEVADA by Tiffany Ann Steinert A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Geology in the College of Science and Mathematics California State University, Fresno May 2016 APPROVED For the Department of Earth and Environmental Sciences: We, the undersigned, certify that the thesis of the following student meets the required standards of scholarship, format, and style of the university and the student's graduate degree program for the awarding of the master's degree. Tiffany Ann Steinert Thesis Author Beth Weinman (Chair) Earth and Environmental Sciences Zhi Wang Earth and Environmental Sciences Keith Putirka Earth and Environmental Sciences For the University Graduate Committee: Dean, Division of Graduate Studies AUTHORIZATION FOR REPRODUCTION OF MASTER’S THESIS X I grant permission for the reproduction of this thesis in part or in its entirety without further authorization from me, on the condition that the person or agency requesting reproduction absorbs the cost and provides proper acknowledgment of authorship. Permission to reproduce this thesis in part or in its entirety must be obtained from me. Signature of thesis author: ACKNOWLEDGMENTS I would like to express the deepest appreciation to my committee chair Professor Beth Weinman, who has shown the attitude and conveyed a spirit of adventure in regard to research and scholarship. Without her supervision and constant help this thesis would not have been possible. I would also like to thank my committee members, Professor Keith Putirka and Professor Zhi Wang, for their aspiring guidance, invaluably constructive criticism and friendly advice during my time at Fresno State. I would like to give a special thanks to my family and friends. Words cannot express how grateful I am to my mother for all of the sacrifices that she made on my behalf. Your prayers for me were what sustained me thus far. I would also like to thank John Rarick for helping me through some really difficult times. Plus I’d like to thank all of my friends who supported me in writing, and motivated me to strive towards my goal. Finally, I would like express appreciation to my beloved husband Bill, who spent countless days in the field with me and was always my support in the moments when there was no one else to hold me up. TABLE OF CONTENTS Page LIST OF TABLES . ix LIST OF FIGURES . x