Timing and maximum flood level of the Early Holocene glacial lake Nedre Glomsjø outburst flood, Norway

Abstract

This study discusses the timing and maximum flood level of the Nedre Glomsjø outburst flood, Norway, based on sediment records retrieved from 15 bog and lake basins located close to the purported maximum flooded level. The sediment records in 12 of the basins consist of a distinct light-coloured silty bed that is correlated to the outburst-flooddeposited 'Romerike Silt Bed' identified elsewhere in the region. The silt bed is recorded in basins up to a certain elevation and is absent above this level. The new maximum flood level inferred from the basin sediment records exceeds the established landform-induced palaeostage indicators by 5-10 m. The data indicate a higher maximum flood level and larger inundation area than previously suggested and highlight the importance of acquiring a wide range of geological data when reconstructing palaeofloods. Radiocarbon dates of terrestrial macrofossils found stratigraphically above and below the Romerike Silt Bed suggest that the glacial lake Nedre Glomsjø outburst flood occurred between 10.5 and 10.3 cal. ka BP. The new and well-constrained timing of the outburst flood is beneficial for reconstructing regional deglaciation and provides a precise age for the Romerike Silt Bed chronostratigraphical marker, which is of value for studies in SE Norway and adjacent regions.

Multi‐proxy palaeoenvironmental reconstruction of the Skagerrak from the Lateglacial to Middle Holocene

“…2011b; Høgaas & Longva 2018; Høgaas et al . 2023). From 372650 it can also be seen that the %C 37:4 levels are still relatively high (~3–4%), indicating a continued freshwater flux, although not as high as the deeper recorded core section in M86‐6 (~11%; Fig.…”

“…2011b; Høgaas & Longva 2018; Høgaas et al . 2023). This outburst affected valleys of SE Norway with an outlet through the Oslo Fjord into the Skagerrak, and resulted in a local rise in sea level during the flood event (Longva & Thoresen 1991; Longva 1994; Høgaas et al .…”

“…This outburst affected valleys of SE Norway with an outlet through the Oslo Fjord into the Skagerrak, and resulted in a local rise in sea level during the flood event (Longva & Thoresen 1991; Longva 1994; Høgaas et al . 2023). A short‐term spike in the input of terrestrial materials and ice‐rafted debris recorded in core MD99‐2286 (Fig.…”