Advances in Nummerical dating for Reconstructing Coastal Environments from the German North Sea Coast and the Mediterranean Coast of Sardinia

Optically stimulated luminescence (OSL) and infrared stimulated luminescence (IRSL) methods using quartz and potassium-rich feldspar, respectively, have been successfully applied to deposits from a variety of different sedimentary environments to determine the time elapsed since the last exposure to sunlight. Coastal sediments including aeolian and shallow marine deposits have been proved to be excellent material for dating, because they fullfill the basic luminescence dating assumptions such as sufficient bleaching/zeroing prior to deposition. Furthermore, in combination with radiocarbon dating robust and reliable chronological frameworks have been provided.

In this paper, we present two luminescence dating case studies. The first one is about a sediment core including Holocene sediments from the German North Sea Coast, previously studied by Zhang et al. (2014) and extended by a sediment core from an inland barrier spit at Eiderstedt peninsula. The lithostratigraphic, sedimentological and chronological investigations yielded the following interpretation: The uppermost 1-2 meter of the sediments are of terrestrial origin and deposited after the construction of dykes along the coast during the 11^th century. These results are in agreement with sedimentological and chronological results from two further localities in the vicinity of the key location. More than 20 m of shallow marine sediments are exposed including a marker horizon rich in shells and shell fragments giving evidence for the rapid Holocene sea-level rise and the arrival of the “sea” at around 8,300 Years BP at the locality under study. Wadden sediments, mud and sand flats sediments and beach wall or barriere spit sediments are typical for the Holocene sequence. A hiatus is found for the time period between 13,000 and 8,300 years BP. Last glacial deposits up to a depth of at least 70 m consist mainly of (reworked) aeolian and fluvial sediments.

The sediment successions along the coast of Sardinia provide important information about the Late Pleistocene – Holocene sea-level changes and sea-level elevations. However, the chronological results of different dating methods, such as OSL, IRSL, electron-spin resonance, radiocarbon, uranium/thorium and amino acid racemisation are not sound and have been a matter of debate for many years. We will discuss the reliability of the different dating methods and present new radiocarbon and luminescence dates as the second case study.

 

Zhang, J., Grube, A., Tsukamoto, S., Frechen, M. (2014): OSL and ¹⁴C chronologies of a Holocene sedimentary record (Garding-2 core) from the German North Sea coast.- Boreas, 43: 856-868.