Middle Weichselian glacial event in the central part of the Scandinavian Ice Sheet recorded in the Hitura pit, Ostrobothnia, Finland

Abstract

The Hitura open pit exposes a sedimentary sequence up to 50 m thick representing Late Saalian to Holocene glacial and non‐glacial sediments. The sequence was investigated using sedimentological methods, OSL‐dating and pollen and diatom analyses to reconstruct the Middle Weichselian (MWG) glacial event in the central part of the Scandinavian Ice Sheet (SIS). The results indicate that the sediment succession represents two entire glacial advance and retreat cycles. The lowermost deposits are Late Saalian esker and delta sediments overlain by sediments that correlate with the early Eemian lacustrine phase. Remnants of the Eemian soil post‐dating the lacustrine phase were also observed. The area was ice‐free during the entire Early Weichselian (EWG). The first glacial advance recorded in the sediments is related to the MWG. It started 79 kyr ago, deformed underlying sediments and deposited an immature till, including large detached sediment pods containing remains of organic material, soils and fluvial sediments representing allochthonous material from EWG ice‐free stadials and interstadials. The glacial deposits are conformably overlain by glaciolacustrine and littoral accumulations, indicating MWG deglaciation between 62 and 55 kyr ago. Based on the fabric measurements from the till unit overlying the MWG sediments, ice advance during the Late Weichselian (LWG) was initially from the west and later from a north‐northwesterly direction. The Hitura strata provide the first dating of the MWG deglaciation (55 to 62 kyr ago) from central parts of the SIS. It can be considered as a key site for studying the growth and decay of SIS during the poorly known early parts of the glaciation.

Glaciotectonic deformation of till-covered glaciofluvial deposits in Oulu region, Finland

“…The till fabrics measurements from the Late Weichselian deposits in the Hitura pit, in the Pohjanmaa region, show that the first ice movement direction was from the west and the latter from the north-west (Salonen et al, 2007). Nenonen (1995) also recorded the same ice movement pattern from Haapavesi, in the Pohjanmaa region.…”

“…Stratigraphical investigations south of the Pudasjärvi-Hossa line ( Fig. 1), however, suggest that the SIS advanced into central and Southern Finland only during the early Middle Weichselian and the Late Weichselian (Lunkka et al, 2004;Salonen et al, 2007). It has been hypothesised that the series of till-covered glaciofluvial ridges in the Pudasjärvi end-moraine zone ( Fig.…”

Proxy comparison in ancient peat sediments: pollen, macrofossil and plant DNA

“…On the other hand, the available climate reconstructions from north-eastern European Russia have shown that summer temperatures may have been sufficiently high for Quercus to grow (38C higher than at present, e.g. [17,23,49,50]) during the earliest part of the Holocene until ca 5000 cal yr BP. In addition, Holocene pollen data recently obtained from the nearby Lake Kharinei showed frequent pollen grains from other thermophilous species, such as Ulmus and Tilia [21] during the mid-Holocene, and because these species, especially Tilia, are mostly insect-pollinated, it was assumed that the source was relatively close.…”

IODP expedition 347: Baltic Sea basin paleoenvironment and biosphere

“…Source: Andrén et al (2011). (Salonen et al, 2007). The first Baltic ice lobe that advanced into Denmark is dated to ∼ 55-50 ky BP (thousand years before present; Houmark-Nielsen, 2007).…”

“…When drilling the holes for microbiology at four sites, contamination tests were carried out (Smith et al, 2000;Lever et al, 2006). A perfluorocarbon (PFC) tracer was pumped continuously into the drilling fluid and samples were taken from three radial positions in each core immediately upon recovery and cutting on the drill deck.…”