Episodes 2023; 46(1): 85-97
Published online March 1, 2023
Copyright © International Union of Geological Sciences.
Ara Jeong1, Yeong Bae Seong2*, Brian F. Gootee3, Byung Yong Yu4, Suet Yi Cheung5
1 Department of Civil Engineering and Environmental Sciences, Korea Military Academy, Seoul 01805, Republic of Korea
2 Department of Geography Education, Korea University, Seoul 02841, Republic of Korea
3 Arizona Geological Survey, 1955 East 6th Street, Tucson, Arizona 85704, USA
4 AMS Laboratory, Advanced Analysis Center, Korea Institute of Science and Technology, Seoul 02792, Republic of Korea
5 Department of Parks, Recreation and Tourism Management, North Carolina State University, Raleigh, NC 27695, USA
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Authigenic 10Be/9Be dating and 10Be inventory methods have been used as a robust chronological tool to date oceanic sediments as old as ~12 Ma. However, their application was limited to continental sediments deposited in relatively closed lakes. We tested the two methods to examine their applicability to early-Pliocene Bouse Formation in the lower Colorado River corridor, as its stratigraphy and age are well-constrained. The calculated authigenic 10Be/9Be ages for the Bouse Formation range from 2.51 to 3.85 Ma, with a mean age of 3.15 Ma, which is considerably younger than the published ages of 5.4 to 4.7 Ma. The measured 10Be inventory was three orders of magnitude lower than the predicted inventory. We examined the factors that may constrain the behavior of beryllium isotopes and suggest that the offset of age could be derived from an estimated initial ratio that may not be the real one or the incomplete retentivity of the beryllium isotopes. The discrepancy between predicted and measured 10Be inventory may be due to surface erosion, insufficient 10Be retention or inaccurate estimation of 10Be inheritance.