Naslov
Age, formation and significance of loess deposits in central Sweden

Autori
Stevens, Thomas ; Sechi, Daniele ; Tziavaras, Charilaos ; Schneider, Ramona ; Banak, Adriano ; Andreucci, Stefano ; Hatterstrand, Mrtina ; Pascucci, Vincenzo

Izvornik
Earth surface processes and landforms (0197-9337) 47 (2022); 1-26

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
aeolian, Holocene, luminescence, OSL, Quaternary, SEM

Sažetak
Loess deposits are common in the mid‐latitudes and are excellent records of past climate, landscape change and dust. However, loess deposits are seldom reported from Fennoscandia. Here we investigate two former glaciofluvial areas in central Sweden, Brattforsheden and Bonäsheden, where post glacial loess and sand dune activity have been documented previously. Based on detailed mapping, grain‐size, SEM and optically stimulated luminescence dating analyses, we confirm the presence of loess deposits at the sites and extend the known area of loess coverage. Our results suggest that loess deposits are more common than previously thought in Sweden. The results alsodemonstrate that basal parts of the loess are often mixed with underlying sediment, which may be a common feature of thin loess deposits close to former ice margins. Quartz luminescence is well suited for dating these deposits, but ages from the mixed basal loess layers are older than expected, while ages from undisturbed loess extend to c. 5 ka. The loess ages contrast with the timing of main dune activity in these areas, which is dominantly in the 1‐3 kyrs post deglaciation (c. 10.9‐10.5 cal kyr BP). We suggest that either sediment mixing during soil formation is responsible for the mid Holocene loess ages, or that the loess deposits record periodic landscape destabilization into the mid Holocene. Furthermore, there is a clear topographic control on aeolian sedimentary facies, with loess mantling high ground and dunes restricted to valleys. Loess deposits are also primarily found to the south and southwest of source areas, implying transport from the north and east. This pattern contrasts with evidence for NW winds inferred from associated sand dunes. At present, the reasons for this mismatch are unclear, although one possible explanation is that silts deposited at higher elevations were affected by Ekman transport deflection of NW surface winds.

Izvorni jezik
Engleski

Znanstvena područja
Geologija

POVEZANOST RADA