Abstract
Reconstructing environmental change in sand-rich drylands, locations where aeolian dunes interact with fluvial systems and lake shorelines, requires wide spatial coverage and dense chronologies. This is extremely time-consuming and resource intensive if laboratory-based luminescence dating of samples is used in isolation. Portable luminescence readers (POSL) (Sanderson and Murphy, 2010) provide a useful means of generalising chronologies within simple systems, and of helping to understand more complex systems through a combination of in situ analyses and laboratory procedures. Here we explore datasets from: (i) 148 dune and 100 lake shoreline samples across southern Africa and (ii) dune damming sediments (DDS) within the Negev, Israel (Roskin et al., 2017), where insights into bleaching histories, sediment luminescence sensitivity and sample age can be gained through a combination of simple POSL profiling and laboratory calibration of luminescence-sensitivity, coupled with SEM analysis.
The southern African datasets show that POSL signals from bulk samples regressed against laboratory-based ages on quartz can be used to calibrate POSL signals into first-order age estimates, and that a regionally-specific approach is needed for different dunefields across the subcontinent (r2 of 0.99, 0.93, 0.81 and 0.52) (Stone et al., 2018). Sample composition, such as quartz to feldspar ratios, account for the largest spatial contrasts, and sample luminescence-sensitivity may also influence signals. For the lake shoreline data, factors other than sample burial age are contributing to driving the POSL signals but with no clear single factor. The Negev case study shows an example of reflexive geomorphology in a more complex DDS setting using POSL alongside laboratory irradiation and SEM analysis. The different DDS could be identified at this vegetated linear dune (mostly stabilized since the Younger Dryas), after accounting for: (i) luminescence sensitivities through calibration, (ii) inherited luminescence signals based on depletion rates and (iii) stratigraphic position. Apparent ages for emplacement of both fluvial and aeolian units can be established providing a coherent basis for interpreting the environmental history of the DDS.
Overall the POSL approaches discussed here provide cost- and time-effective means of generalising chronostratigraphies over large areas in both simple and complex systems, in order to reconstruct Quaternary environmental changes.
Roskin, J., Bookman, R., Friesem, D.E., Vardi, J. 2017. A late Pleistocene linear dune dam record of aeolian-fluvial dynamics at the fringes of the northwestern Negev dunefield. Sedimentary Geology 353, 76-95.
Sanderson, D.C.W., Murphy, S., 2010, Using simple portable OSL measurements and laboratory characterisation to help understand complex and heterogeneous sediment sequences for luminescence dating, Quaternary Geochronology, 5, 299-305
Stone, A., Bateman, M.D., Burrough, S.L., Garzanti, E., Limonta, M., Radeff, G., Telfer, M.W., 2019. Using a portable luminescence reader for rapid age assessment of aeolian sediments for reconstructing dunefield landscape evolution in southern Africa. Quaternary Geochronology 49, 57-64.
The southern African datasets show that POSL signals from bulk samples regressed against laboratory-based ages on quartz can be used to calibrate POSL signals into first-order age estimates, and that a regionally-specific approach is needed for different dunefields across the subcontinent (r2 of 0.99, 0.93, 0.81 and 0.52) (Stone et al., 2018). Sample composition, such as quartz to feldspar ratios, account for the largest spatial contrasts, and sample luminescence-sensitivity may also influence signals. For the lake shoreline data, factors other than sample burial age are contributing to driving the POSL signals but with no clear single factor. The Negev case study shows an example of reflexive geomorphology in a more complex DDS setting using POSL alongside laboratory irradiation and SEM analysis. The different DDS could be identified at this vegetated linear dune (mostly stabilized since the Younger Dryas), after accounting for: (i) luminescence sensitivities through calibration, (ii) inherited luminescence signals based on depletion rates and (iii) stratigraphic position. Apparent ages for emplacement of both fluvial and aeolian units can be established providing a coherent basis for interpreting the environmental history of the DDS.
Overall the POSL approaches discussed here provide cost- and time-effective means of generalising chronostratigraphies over large areas in both simple and complex systems, in order to reconstruct Quaternary environmental changes.
Roskin, J., Bookman, R., Friesem, D.E., Vardi, J. 2017. A late Pleistocene linear dune dam record of aeolian-fluvial dynamics at the fringes of the northwestern Negev dunefield. Sedimentary Geology 353, 76-95.
Sanderson, D.C.W., Murphy, S., 2010, Using simple portable OSL measurements and laboratory characterisation to help understand complex and heterogeneous sediment sequences for luminescence dating, Quaternary Geochronology, 5, 299-305
Stone, A., Bateman, M.D., Burrough, S.L., Garzanti, E., Limonta, M., Radeff, G., Telfer, M.W., 2019. Using a portable luminescence reader for rapid age assessment of aeolian sediments for reconstructing dunefield landscape evolution in southern Africa. Quaternary Geochronology 49, 57-64.
| Original language | English |
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| Publication status | Published - 25 Jul 2019 |