Coastal lagoons and beach ridges as complementary sedimentary archives for the reconstruction of Holocene relative sea‐level changes

Abstract

Coastal lagoons and beach ridges are genetically independent, though non-continuous, sedimentary archives. We here combine the results from two recently published studies in order to produce an 8000-year-long record of Holocene relative sea-level changes on the island of Samsø, southern Kattegat, Denmark. The reconstruction of the initial mid-Holocene sea-level rise is based on the sedimentary infill from topography-confined coastal lagoons (Sander et al., Boreas, 2015b). Sea-level index points over the mid-to late Holocene period of sea-level stability and fall are retrieved from the internal structures of a wide beach-ridge system (Hede et al., The Holocene, 2015). Data from sediment coring, georadar and absolute dating are thus combined in an inter-disciplinary approach that is highly reproducible in micro-tidal environments characterised by high sediment supply. We show here that the commonly proximate occurrence of coastal lagoons and beach ridges allows us to produce seamless time series of relative sealevel changes from field sites in SW Scandinavia and in similar coastal environments.

A high‐resolution sea‐level proxy dated using quartz OSL from the Holocene Skagen Odde spit system, Denmark

“…11; Clemmensen et al 2012), while on Samsø a long-term rate of around 0.45 mm a À1 can be estimated (Fig. 11;Sander et al 2015). These values of past uplift rates are related to an increased glacio-isostatic uplift in a northward direction in the Kattegat region (Mertz 1924;P asse & Andersson 2005;Nielsen et al 2014).…”

“…For comparison, the average regression rate for the last 4900 years was about 2.0 mm a À1 at the nearby Kattegat island Laesø ( Fig. 11; Sander et al 2015). At the Kattegat island Anholt further south, the long-term uplift rate was apparently around 1.2 mm a À1 (Fig.…”

Coastal barrier stratigraphy for Holocene high-resolution sea-level reconstruction

“…The interface between the foreshore and the shoreface observed in GPR images has also been used and dated to infer sea-level trends2021434445. Some of these studies have focused on proving the reliability of this marker as a proxy of sea-level position by comparing recorded morphologies (morphology-slope of the reflections) with the present-day morphology of the foreshore and shoreface4346.…”

Indication of Holocene sea-level stability in the southern Laptev Sea recorded by beach ridges in north-east Siberia, Russia

“…Arctic coastal environments are currently undergoing rapid changes due to the Arctic amplification of the global climate warming trend, which affects the integrity and resilience of Arctic coastal systems (Jones et al 2009;Overeem et al 2011;Serreze & Barry 2011;Günther et al 2013;Irrgang et al 2018). RSL, sediment supply and wave energy act as the controlling parameters, affecting shoreline stability and coastal evolution over the long-term (e.g., Goodwin et al 2006;Allard et al 2008;Billy et al 2015;Fruergaard et al 2015;Sander et al 2016;Sander, Pejrup et al 2018). A large proportion of the Siberian coast is composed of unconsolidated sediment and reacts sensitively to changes in external forcing (Rachold et al 2000;Overduin et al 2014;Sánchez-García et al 2014).…”

“…to preserve information on the environmental conditions during their formation, such as RSL, wave climate, extreme storm surges, changes in sediment supply and sea-ice extent (e.g., Taylor & Stone 1996;Otvos 2000;Brückner & Schellmann 2003;Funder et al 2011;Scheffers et al 2012;Tamura 2012;Sander et al 2016;Nielsen et al 2017).…”