Middle Palaeolithic artefact migration due to periglacial processes; a geological investigation into near-surface occurrence of Palaeolithic artefacts (Limburg-Eastern Brabant coversand region, the Netherlands)

Abstract

The original distribution pattern of Middle-Palaeolithic artefacts may be affected by tectonic movement, sedimentation and periglacial processes. This is e.g. the case in the coversand area of Limburg and Eastern Brabant (NL), where the occurrence of numerous finds in a SW-NE trending zone across the Roer Valley Graben is considered enigmatic. In order to elucidate the processes affecting the spatial distribution and the chance of recovery of such artefacts, we investigated a site in Nederweert. At this site, several Middle-Palaeolithic artefacts had been recovered earlier from unexpectedly shallow depths. A test pit profile and grain size analyses revealed that the shallow sediments at this site have been affected by intense, multi-phase cryoturbation, which has deformed the sand and loam layers and partially mixed them thoroughly. As a result, optically stimulated luminescence dating of these sediments yielded widely scattered single-aliquot equivalent dose distributions. Using a Finite Mixture Model (FMM), it was estimated that cryoturbation caused mixing of sediments deposited between 12 and 50 ka with sediment grains deposited between 60-150 ka. The latter material is probably the original context of the Middle-Paleolithic artefacts. Apparently, cryoturbation and potentially other periglacial processes have transported artefacts closer to the surface. Based on these results, we suggest that the occurrence of Middle-Palaeolithic artefacts is caused by (1) the tectonically-induced spatial distribution of layers of this age and (2) periglacial processes having caused migration of artefacts towards the surface. Although periglacial processes may facilitate finding Middle Palaeolithic artefacts, they may severely disturb the original context to such an extent that Middle Palaeolithic sites can no longer be identified. The results of this study form a basis for improving the Indicative Map of Archaeological Values that is used to predict the presence of archaeological sites. The insights gained are also relevant to other areas where Middle-Palaeolithic sites are affected by periglacial processes.

Late Glacial and Holocene aeolian deposition and soil formation in relation to the Late Palaeolithic Ahrensburg occupation, site Geldrop-A2, the Netherlands

“…There are some indications for periglacial activity (polygonal frost-crack pattern) during formation of the fine-grained lower part of the YCII unit and Ahrensburg find layer. However, significant vertical movements of artefacts did not occur in the investigated sections, in contrast to findings in nearby areas (Deeben et al, 2010). The cracks were probably formed during the early Younger Dryas based on the OSL dates of the units.…”

The emergence of the Middle Palaeolithic in north-western Europe and its southern fringes

“…"Further to the north artefacts do occur 'geological in situ', i.e. in the ice-pushed ridges in the Central Netherlands and on the Drenthee Frisian till plateau in the northernmost part of the country (Deeben et al, 2010), but primary archaeological in situ situations have yet to be discovered. During the Pleistocene, the northern Netherlands, as part of the Norddeutsches Tiefland, was repeatedly modified and bulldozed by glaciers.…”

The interactions between Quaternary Geology and Archaeology

“…Quaternary geology is increasingly applied to gain insight in the landscape development and environmental setting where people have lived in the past. Above this, predictive models can be improved by the interaction of archaeological and geological/palaeogeographical research (see also Deeben et al, 2010).Furthermore, the increased cooperation results in exchange of knowledge and provides access to geologically interesting locations during archaeological excavations. This special issue of the Netherlands Journal of Geosciences gives some examples of recent studies where the interactions between Quaternary Geology and Archaeology are outlined.…”

“…Quaternary geology is increasingly applied to gain insight in the landscape development and environmental setting where people have lived in the past. Above this, predictive models can be improved by the interaction of archaeological and geological/palaeogeographical research (see also Deeben et al, 2010).…”

“…However, due to several geomorphological or biological processes, these artefacts may have been reworked or transported vertically and end up in a different stratigraphic position than originally deposited. In their contribution on the migration of Middle Palaeolithic artefacts Deeben et al (2010) show that artefacts can be transported upward due to cryoturbation and upfreezing. Mixing with overlying younger material could be tested with the application of OSL dating techniques (Wallinga et al, 2007), showing that the process of periglacial transport indeed influences the stratigraphic position of artefacts.…”