Chemical weathering on the glacial foreland of Storbreen, Jotunheimen Mountains, Norway

Mountains of Norway. Its Little Ice Age maximum occurred about 1750 when it deposited a well-defined end moraine. Since then it has retreated leaving a series of recessional moraines. All of these moraines have been dated lichenometrically by Matthews (see Matthews, 1992 for a comprehensive summary). We used this series of dated moraines to investigate the early stages of pedogenesis, the early stages of the chemical weathering of cobbles, and the impact of variation between 1750 moraine crest and moraine proximal base positions upon soil chemistry and mineralogy. The overall pedological research design (Darmody et al. 2005) embraced three distinct elements. First, there was a constant elevation sequence undertaken on the southern flank of glacier foreland with triplicate soil pits excavated at the present glacier snout, on the crests of the AD 1750, 1810, 1870, and 1928 moraines, and finally upon an approximately 10 000 year-old surface beyond the glacier foreland. Second, there was a vertical sequence investigated up and down the 1750 moraine (low = approximately 1165 to 1180 m a.s.l.; middle = approximately 1310 to 1330 m a.s.l.; high = approximately 1400 to 1465 m a.s.l.). This sequence included matched triplicate pits on the 10 000 year-old surface, the 1750 moraine crest, and the 1750 moraine proximal base at all three elevations. Third, there was a skeletal matching of 1750 moraine crest pits on the southern and northern flanks of the foreland at the three aforementioned elevation levels. Within the overall pedological study a reduced set of the moraine-crest sites was used to study the development of chemical weathering within surficial lichen-free-free, surficial lichen-covered, and buried cobbles. Porosity within feldspar minerals was determined with backscatter electron microscopy. The third element of the study compared and contrasted clay mineralogy and soil chemistry up and down the 1750 moraine to determine if the published identification of a ‘green zone’ had measurable significance beyond the lichenometric one already demonstrated in the literature. Soils were mostly frigid or isofrigid, coarse textured, and poorly developed Cryorthents (American Soil Taxonomy). There were differences between same-age soils at different elevations, same-elevation soils of differing ages, and soils from moraine crest and base pairs. Primary minerals, quartz, mica, feldspar, and amphibolites dominated soil mineralogy. However, secondary minerals, in particular hydrobiotite, increased with age and elevation. Despite the generally poor soil development, detectable topochronosequence differences in soil and associated weathering trends emerge in this young, cold environment.