M.Sc. Thesis Defence: Dr. Cody Paige
M.Sc. Thesis Defence
Dr. Cody Paige
Department of Earth and Environmental Sciences, Dalhousie University
Title: Combining cosmogenic nuclide depth profiles and in situ 14C to measure erosion-adjusted exposure ages of sedimentary land/ orms
Abstract: In situ cosmogenic 14C offers a unique window into the recent erosion and burial histories of sedimentary landform surfaces due to its short mean life (ca. 8,223 yr) relative to other terrestrial cosmogenic nuclides (TCNs). This short mean life makes.14C sensitive to erosion and burial processes over the past 25-30 kyr- timescales that are poorly resolved by longer-lived nuclides such as 10Be and 36Cl. Here I present a novel approach to estimate erosion rates on late Pleistocene alluvial fan and shoreline surfaces in Pana mint Valley, California, by measuring 14C saturation concentrations in detrital quartz sand from amalgamated sediment samples collected just below the soil mixing zone. Sample locations were guided by soils and geomorphic observations at four sites. I also describe the development and testing of a 14C extraction line at Dalhousie University, including validation against the known inter-laboratory standard, CRONUS-A. Erosion rate uncertainty improved by up to 50% compared to soils geomorphology-based estimates, providing tighter constraints on 10Be depth profile exposure ages at the same sites. Comparison of 14C-derived erosion rates with independent 10Be and 36Cl depth profile ages suggests that previous field-based erosion rate estimates may have significantly underestimated uncertainty in paleo-erosion histories. These results demonstrate the utility of in situ 14C saturation measurements as a practical and powerful complement toconventional TCN depth profile dating of alluvial fan surfaces in arid environments, with broader implications for landscape evolution studies in tectonically active regions.
Examining Committee:
Dr. Gary Salazar Quintero, University of Ottawa, External Examiner
Dr. John Gosse, Dalhousie University, Supervisor
Dr. Owen Sherwood, Dalhousie University, Reader
Dr. Eric Kirby, Penn State University, Reader
Dr. Mladen Nedimovic, Dalhousie University, Defence Chair
Time
Location
Milligan Room - Life Sciences Centre, Room 8007