Fluvial and aeolian interaction under permafrost conditions: Weichselian Late Pleniglacial, Twente, eastern Netherlands

Close interaction between fluvial and aeolian deposition led to the formation of a distinct ‘fluvio-aeolian’ depositional environment in river valleys in the Netherlands during the last glacial maximum. We describe three sections illustrating this sedimentary environment. The primary sedimentary structures and periglacial phenomena document the dynamic interaction between fluvial, aeolian and periglacial processes. The rivers were ephemeral in nature, with alternating fluvial and aeolian deposition in overbank environments. Within the sections, successive levels of frost cracks, ice-wedge casts, soil wedges and cryoturbations are found. The sections demonstrate that not all these levels of periglacial structures indicate climatic oscillations, but are caused by lateral migration of fluvial activity. However, one large cryoturbation level truncated by a gravel lag (the Beuningen gravel bed) is evidence of widespread permafrost degradation induced by climatic warming between ca. 16 and 22 ka. This climatic warming is followed by a significant increase of aeolian activity.