200 ka of glacial events in NW Svalbard: an emergence cycle facies model and regional correlations

Abstract

Late Quaternary sedimentary units at Kongsfjordhallet, NW Svalbard, represent five cycles of glaciations and subsequent deglaciations during high relative sea levels. The high sea level events are interpreted as glacioisostatically induced and imply preceding regional glaciations, which we constrain in time by luminescence and radiocarbon ages to just prior to ~ 195, ~ 130, ~ 85, ~ 60, and ~ 15 ka. Combined with the stratigraphical record from nearby Leinstranda we identify six, possibly seven, major glacial advances during the last 200 ka in the Kongsfjorden region. Two of these occurred during the Saalian and at least four during the Weichselian. The results are based on detailed sedimentological, stratigraphical and chronological investigations of the uppermost 15 m of the 40-m-high Kongsfjordhallet coastal sections. The succession is dominated by sediments of marine and littoral origin, representing partial shallowing-upward sequences due to isostatic rebound. Only one subglacial till was recognised. Interestingly, alluvial and periglacial deposits, not commonly recognised in this type of setting, occur in the sequence. These include weathered coarse alluvium, sandy channel fills as well as cryoturbated sediments and solifluction deposits, which are positive evidence of a non-glacial environment. The sequence of sediments that represents an emergence cycle has been formalised in a facies model.

Sediments of MIS 5e age suggested by new OSL dates from the Skilvika section, west Svalbard

“…2) probably reflects a local ice flow style (Landvik et al 2014) during deglaciation, rather than an advance of a local glacier as previously assumed (Landvik et al 1992). A MIS 5e age also means that Skilvika is added to the group of sites in Svalbard with preserved Eemian deposits (Kapp Ekholm, Leinstranda, Kongsfjordhallet, Poolepynten), supporting the revised correlation scheme of Late Quaternary key stratigraphic sites on Svalbard suggested by Alexanderson et al (2018).…”

“…We cannot evaluate this factor for our data set specifically. Also, information from OSL ages from sediments correlated to the Eemian elsewhere in Svalbard is inconclusive as there are indications both of some age underestimation (Alexanderson et al 2013) and of no apparent underestimation (Alexanderson et al 2011;Alexanderson et al 2018). Generally, there is a wide spread in ages for these sediments, which may be due to incomplete bleaching, poor luminescence characteristics or other causes, and which prevents resolving the age of the events in detail.…”

A 160,000-year-old history of tectonically controlled methane seepage in the Arctic

“…Regardless, the clustering of the U-Th ages around ~148 ± 11 ka points to increased methane seepage limited to the PGM and possibly forebulge migration during the build-up of the pan-Arctic glaciation. Age constraints of glacial sediments onshore NW Svalbard (KII event; 165 ± 16 ka, 135 ± 11 ka, and 130 ± 8 ka) ( 43 ) confirm glaciation on Svalbard during the PGM in support of the forebulge hypothesis. Subsequent seepage quiescence following the forebulge collapse was likely due to the relative lower reservoir pore pressure in the seepage aftermath.…”

Arctic environmental change beyond instrumental records: introduction and overview

“…Sedimentological and stratigraphical investigations of Late Quaternary deposits at Kongsfjordhallet, northwest Svalbard, by Alexanderson et al [10] provide evidence for at least three and possibly as many as five, glacioisostatically-induced, high relative sea level events which imply preceding regional glaciations. Integration with records from elsewhere on northwestern Svalbard indicate there were six major glacial advances during the last 200 ka.…”

“…Briner and Hormes [13] report on the 10 Be dating of glacial erratics, moraine boulders and a bedrock surface from Bjørnøya, Svalbard. They use these data to reconstruct the final stages of the last deglaciation of the Barents Sea Ice Sheet from Bjørnøya and the surrounding Spitsbergenbanken, southern Barents Sea.…”