Tie channel sedimentation rates, oxbow formation age and channel migration rate from optically stimulated luminescence (OSL) analysis of floodplain deposits

Abstract

Using optically stimulated luminescence (OSL) analysis we obtained depositional ages ranging from 25 ± ± ± ± ± 10 to 928 ± ± ± ± ± 144 years before present for sediments deposited in oxbow lakes along three lowland river systems. The dated sediments were collected from the banks of tie channels along the Lower Mississippi River, the Fly River in Papua New Guinea, and Birch Creek along the Yukon River in Alaska. Tie channels connect the oxbow lakes to the main stem river and allow the exchange of water and suspended sediment between the two. The banks consist of fine sand and sandy silt beds interlayered with silt and clay. OSL samples were collected both horizontally from exposed banks and vertically by coring through levee crests; sample collection was targeted at beds containing appreciable quantities of fine sand. OSL ages were determined using single-grain or in some cases single-aliquot techniques and dose distribution analysis. Samples were first collected along the Lower Mississippi tie channel to compare OSL dates with historical data sources and test the applicability of OSL in these settings; the OSL dates agreed closely with historical data. In all three river systems, OSL dating allowed the determination of vertical accretion rates, tie channel advancement rates, and oxbow lake ages. In Papua New Guinea, OSL sampling also provides an estimate of lateral migration rates of the Fly River and allows a comparison of modern mineinfluenced deposition rates with natural background rates over the last 1000 years. Results from Papua New Guinea and the Mississippi River suggest that the advancement rate of tie channels responds directly to changes in the sediment load of the main stem river.

Changes in the rates of floodplain and in-channel bench accretion in response to catchment disturbance, central Queensland, Australia

“…Recent advances in analysis techniques have improved the confidence in dating very young (b200 y) deposits (e.g., Galbraith et al, 1999;Olley et al, 2004), and as a result, more researchers are using the technique (e.g., Madsen et al, 2005;Page et al, 2007;Rustomji and Pietsch, 2007;Thoms et al, 2007). In many of these studies, alternative dating techniques have been used to provide some validation of OSL ages (e.g., Madsen et al, 2005;Rowland et al, 2005;Rustomji and Pietsch, 2007). In this study, 137 Cs depth profiles and the presence/absence of 137 Cs in samples taken for OSL provide some verification of the general accuracy of the youngest OSL ages.…”

Optical ages indicate the southwestern margin of the Green Bay Lobe in Wisconsin, USA, was at its maximum extent until about 18,500years ago

“…Another method to check for partial bleaching is to monitor the ratio of the mean to median D e values for each sample. Mean to median ratios of 1.05 or less are assumed to be well-bleached and those with ratios of N1.05 are assumed to be poorly bleached (Rowland et al, 2005). Six of our samples run using the 2-mm aliquots had ratios of N1.05 suggesting potential bleaching problems (Table 1).…”

Spillage sedimentation on large river floodplains

“…They may also extend erosively as dendritic networks draining surface waters or groundwaters (SLg). These convey sediment as much as contain them, producing elongate deposits in lakes (Rowland et al, 2009(Rowland et al, , 2010 and see Figure 1), though such channels may also silt up where not flushed by exiting mainstream flows (Rowland et al, 2005;Trigg et al, 2012).…”