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

Recent LiDAR surveys have revealed that on postglacially uplifting coasts of Estonia rhythmic coastal landforms (beach ridge sequences and foredune plains) occur to a considerable extent. We studied four of them to reveal age and periodicity in these multiple ridge systems and discussed their genesis in the Subatlantic (semi‐continental) conditions of the Baltic Sea area. Using recent models of Fennoscandian uplift due to glacial isostatic adjustment (GIA), we constructed Holocene apparent sea level curves for the study sites at Õngu, Mänspe, Haldi and Keibu; converted distance–height shore profiles into time series (including corrections on shore profile non‐linearity and variations in GIA‐eustasy balance); and analysed the patterns using spectral analysis. It was suggested that due to non‐tidal conditions, relatively low‐energy hydrodynamic forcing and small aeolian contribution, the ridges mark ancient shorelines. They are relatively modest in height (mostly 0.2–1 m), form regular and extensive (up to 150 ridges) patterns, and date back to ~9000 years before present. We studied <5‐ka‐old sections. The mean ridge spacing varied, depending also on coastal slope, between 21 and 39 m. Both simple counting and spectral analysis involved some specific limitations, yet the estimates for typical spacing were alike, at 32 (±5) years. The regular nature of the low‐ridge patterns originated from relative sea level lowering and gradual sediment accretion/erosion. However, the progradation was rather uplift‐ than accretion‐driven and the stepwise process in ridge formation was probably not autocyclic. It was governed or modulated by quasi‐periodic 25–40 year cyclicity in local wave forcing, relative sea level variations and wind conditions. Being most likely connected to the North Atlantic Oscillation, the quasi‐regular, decadal‐scale, similarly phased variations may magnify each other's effect on the westerly exposed coasts of Estonia. Additionally, some other (e.g. event‐driven) mechanisms may also be present.

“…; Clemmensen et al . ). As the GIA–Date (Table ) differences were small (<1 m), we assume that the neotectonic component is very small in our study sites.…”

Section: Results and Interpretationmentioning

confidence: 97%

“…; Clemmensen et al . ). Although looking somewhat similar, beach ridge plains should be in principle, genetically distinguished from foredune plains, as the former are predominantly formed by wave action, while the latter are of aeolian origin.…”

mentioning

confidence: 97%

Cyclicity in ridge patterns on the prograding coasts of Estonia

Suursaar

Kall

Steffen

et al. 2019

“…Compared to other recent RSL studies in Denmark, such as Clemmensen et al . (2018), Hansen et al . (2016) and Hede et al .…”

Section: Discussionmentioning

confidence: 99%

Meadow, marsh and lagoon: Late Holocene coastal changes and human–environment interactions in northern Denmark

Kristiansen

Ljungberg

Christiansen

et al. 2020

This paper presents a study of past coastline dynamics and their consequences for prehistoric societies living in the glacio‐isostatically uplifted central Limfjord area, northern Denmark. The consequences of the gradual relative sea level (RSL) changes have been investigated to develop a local RSL curve, study settlement patterns on newly exposed marine foreland, and estimate changes in the area and quality of grazing and forage for livestock. This was achieved by a multidisciplinary approach involving existing regional and local beach ridges dated by optically stimulated luminescence, a comprehensive database of archaeological finds, and extrapolation based on a digital elevation model. The beach‐ridge dates suggested a near‐linear local RSL change in the study area of ~1.2±0.2 m per 1000 years for the last 3000 years. Based on this, a palaeo‐coastline development model was produced that correlated well with a comprehensive database of archaeological finds. The model indicates that (i) few human settlements moved to the newly exposed marine foreland prior to modern times, though clusters of burial mounds (barrows) suggest that some of the new lands were colonized during the Late Roman Iron Age until 400 CE, (ii) winter‐flooded marine foreland with high‐quality livestock grazing increased steadily until c. 750 CE and then remained stable at approximately 150 km2, and (iii) due to high salinity of the inundating water, the palaeo‐Limfjord probably had Wadden Sea‐like fertile saltmarshes until c. 1 CE. The improved chronologies yield a better understanding of the spatial and temporal prehistoric human–nature interactions in the study area. The findings highlight the need for accurate local RSL curves in order to interpret concomitant terrestrial environment drivers and trajectories, and thereby understand causal relationships and consequences for prehistoric human–environment interactions in coastal areas.

“…The beach‐ridge system in Albuen is noticeably younger than other beach‐ridge systems in the region, most of which initiated 4500–7000 years ago (Clemmensen et al . , ; Hede et al . ).…”

Section: Discussionmentioning

confidence: 99%

“…; Clemmensen et al . , ; Lampe & Lampe ). However, using sand‐sized material may be challenging in some environments.…”

mentioning

confidence: 99%

Luminescence dating of buried cobble surfaces from sandy beach ridges: a case study from Denmark

Souza

Sohbati

Murray

et al. 2019

Self Cite

Here we investigate the use of optically stimulated luminescence (OSL) for dating cobbles from the body of successive beach ridges and compare cobble surface‐derived ages to standard quartz OSL ages from sand. Between four and eight cobbles and sand samples (age control) were dated with the luminescence method, taken from the modern beach and from beach ridges on the south and north extremes of a prograding spit on the westernmost coast of Lolland, Denmark. Luminescence‐depth profiles perpendicular to the surfaces of the cobbles show that the feldspar infrared signals stimulated at 50 °C were fully reset to various depths into the cobbles prior to final deposition; as a result, the equivalent doses determined from close to the surface of such cobbles can be used to calculate burial ages. Beach‐ridge burial ages given by the average of ages of individual cobbles taken from the same site are consistent, within errors, with the ages derived from the sand samples. Cobble‐ and sand‐derived ages show that the southernmost beach ridge at Albuen was formed around 2 ka ago, indicating that this sandy spit is younger than other coastal systems in Denmark. The agreement between ages derived from clasts and from standard quartz OSL in this study confirms that, even in the absence of sandy sediments, we can reliably date sites using OSL by targeting larger clasts. In addition, the record of prior light exposure contained in the shape of the cobbles’ luminescence‐depth profile removes one of the major uncertainties (i.e. the degree of signal reset prior to burial) in the luminescence dating of high latitude sites.