Johanna Lomax

Performance tests using the Lexsyg luminescence reader

This study presents test measurements on a Lexsyg luminescence reader, acquired by the Giessen luminescence group. The reader is of the type Standard, hence designed for routine determination of palaeodoses using quartz or K-feldspars. The tests include measurements of the stimulation powers, preheat temperatures, OSL- and TL-curves, as well as dose recovery tests and calibration measurements using highly sensitised calibration quartz. A comparison of De values determined using a Lexsyg reader with single grain De-values, which have been previously obtained on a Risø reader, is also presented. The results imply that the Lexsyg reader is a highly reliable measurement device with high reproducibility, yielding instrumental uncertainties of around 0.3%.

Holocene landscape dynamics at the tell Arslantepe, Malatya, Turkey – Soil erosion, buried soils and settlement layers, slope and river activity in a middle Euphrates catchment

Alluvial and colluvial sequences were studied around the prehistoric tell Arslantepe in 11 exposures and additional auger cores. The chronology is based on 11 optically stimulated luminescence (OSL) ages, four radiocarbon ages, and the embedded artifacts. Sediments contained wood charcoals, providing information on former vegetation. Fluvial activity is documented during Late Glacial times (15.4 ± 2.5, 12.8 ± 3.1 kyr) and frequently after Roman times. Slope and soil erosion occurred in the early (10.6 ± 1.4, 8.2 ± 0.7 kyr) and mid–late Holocene (6.7 ± 0.9, 5.4 ± 0.7–4.7 ± 0.7, 2.6 ± 0.2–2.5 ± 0.2, 1.9 ± 0.2–1.8 ± 0.2 kyr, and during the last 1000 years). The early Holocene erosion phases pre-date the so far established onset of settlement at the tell. This either indicates an earlier onset of agricultural land use than assumed or climatic influence on erosion, such as the 10.3 and 8.2 kyr climate events known from Western Europe. The erosion phases at around 5.0 and 2.6 kyr could reflect geomorphic responses to societal collapse (Late Chalcolithic state, Neo-Hittite kingdom) at Arslantepe. Most intensive Holocene soil erosion and landscape degradation occurred after occupation of the region by the Roman Empire. This is paralleled by the onset of river activity. A part of the lower neo-Hittite town as well as an early Holocene Terra Rossa–like soil that had formed rapidly were found buried. So far, no indication for mid–late Holocene fluvial activity of the adjacent creeks until Roman times has been found. Our results illustrate the large potential of slope deposits for long term reconstructions of human induced landscape transformation in Anatolia.

The effect of fluvial environments on sediment bleaching and Holocene luminescence ages — A case study from the German Alpine Foreland

This study investigates the potential of luminescence to date deposits from different fluvial sedimentary environments; namely point bar deposits, sandy and silty channel fills and floodplain sediments. Samples were taken from Holocene (<5 ka) terraces of the Lech and Danube rivers, for which independent age constraint is available through 14C ages, archaeological data and historical maps. OSL-ages were obtained using small aliquots of coarse grain quartz for the majority of samples. Two further samples were dated by the IRSL-signals of polymineral fine grain extracts, as no sufficient number of coarse grains could be extracted from these sediments. In order to detect and ac-count for incomplete bleaching, we used the decision process suggested by Bailey and Arnold [Statistical modelling of single grain quartz De distributions and an assessment of procedures for estimating burial dose. Quaternary Science Reviews 25, 2475–2502, 2006]. Although their model was designed for single grains of quartz, our study shows that it is also applicable to multiple grains of quartz, pro-vided that a low number of luminescent grains is present on one aliquot. Luminescence ages of point bar deposits and a sandy channel fill correspond most closely to the independent age control. In the floodplain, sand-striped floodplain channel deposits were incompletely bleached to a moderate degree, yielding ages with acceptable overestimations, while fine-grained floodplain deposits were worst bleached. One crevasse splay deposit was so severely incompletely bleached that none of the age models was able to yield accurate ages.