Luminescence dating and palaeomagnetic age constraint of a last glacial loess-palaeosol sequence from Istria, Croatia

Abstract

Loess and loess-like deposits with intercalated palaeosols are widely distributed in Croatia, particularly in the Pannonian basin in the east and along the Adriatic Coast in the west, which have provided invaluable evidences of Quaternary climate change. The timing, provenance and spatial distribution of such loess deposits have long been a major research interest. In the current study, a ∼8-m-thick loess-palaeosol sequence located near the town of Savudrija (Savudrija Section), on the northern-most cape of the Istrian Peninsula on the Adriatic Coast, is investigated. Multiple approaches of luminescence dating and palaeomagnetic age constraint are conducted to understand the timing of the regional aeolian activities and its implications for climate change. Seven samples were collected from the loess layers of the Savudrija section for comprehensive quartz optically stimulated luminescence (OSL) and feldspar post-IR infrared stimulation luminescence (IRSL) dating. The palaeomagnetic investigation was conducted on 82 oriented samples collected from the upper 6.7 m of the section. The quartz OSL ages of the upper four samples and the fading corrected pIRIR225 ages of the lower three samples were used to reconstruct the age framework of the section. The results demonstrate that the Savudrija loess-palaeosol sequence were formed between ∼70 ka and ∼9 ka, correlated to the time span from the last glacial to early Holocene. The variation of the magnetic susceptibility of the Savudrija section is strictly following the pattern that the palaeosol horizons generate high susceptibility values while the loess horizons show low susceptibility values. The palaeomagnetic age constraint is obtained by correlating the magnetic susceptibility record of the Savudrija section with other records, which gives the age range between 65 ka and 20 ka for the loess-palaeosol sequence (excluding the lowermost red soil). It broadly agrees with the luminescence chronology but conflicts in details, demonstrating that the correlation between the different magnetic susceptibility records is questionable. Furthermore, the magnetic susceptibility record suggests that the age of ∼70 ka of the red soil at the bottom of the section might be still ambiguous and needs further study.