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Testing Luminescence Dating Methods for Small Samples from Very Young Fluvial Deposits
Joel Q G Spencer1, Sébastien Huot2, Allen W Archer1
1Department of Geology, Kansas State University, Manhattan, KS 66506, USA.
Methods and Protocols
|December 11, 2019
Summary
This study explores sediment dynamics in young Amazon River systems using optically stimulated luminescence (OSL) dating. OSL dating proves effective for analyzing recent fluvial processes and land use changes in these dynamic environments.
Area of Science:
- Geology
- Geochronology
- Environmental Science
Background:
- Young fluvial systems in the Amazon River catchment exhibit sedimentological dynamics influenced by land use change.
- Modern analogue studies of tidal rhythmites in the geologic record are crucial for understanding ancient depositional environments.
- Spit and bar deposits in the Rio Tapajós show apparent decadal stability, suggesting recent deposition.
Purpose of the Study:
- To understand the sedimentological dynamics of very young fluvial systems in the Amazon River catchment.
- To relate these dynamics to land use change and modern analogue studies of tidal rhythmites.
- To assess the feasibility of optically stimulated luminescence (OSL) dating for very young fluvial deposits.
Main Methods:
- Quartz optically stimulated luminescence (OSL) dating feasibility studies were conducted on spit and bar deposits.
- Sub-samples from vertical cores were analyzed using medium-sized aliquots (5 mm diameter).
- Modified single-aliquot regenerative-dose (SAR) approaches were employed to determine equivalent doses as low as ~4 mGy.
- Dose rates were calculated using ICP-MS/ICP-OES and high-resolution gamma spectrometry.
Main Results:
- OSL signals from sub-samples exhibited high sensitivity, excellent dose recovery and recycling, and minimal heat transfer.
- Equivalent doses as low as ~4 mGy were obtained using modified SAR approaches.
- OSL ages for investigated features ranged from 13–34 years to several hundred years.
- High-resolution sampling at 1–2 cm intervals was possible due to quartz-rich sands.
Conclusions:
- OSL dating is a viable method for studying very young, active fluvial processes in the Amazon River catchment.
- The technique can provide insights into sedimentological dynamics and their relationship to land use change.
- The study demonstrates the potential of OSL for reconstructing recent geological histories in dynamic river systems.
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