Hidden paleosols on a high-elevation Alpine plateau (NW Italy): Evidence for Lateglacial Nunatak?

Origin and characteristics of ancient organic matter from a high‐elevation Lateglacial Alpine Nunatak (NW Italy)

“…Low soil temperatures also participate in OM preservation, by slowing down the early decomposition of fresh organic matter. Similar LF contents were found in the surface sample P2‐9, where the input of recent OM derived from local plants is much smaller, partly counterbalanced by aeolian inputs of materials derived from nearby plant communities (Pintaldi et al, 2021b) and, more surprisingly, in the subsurface horizon P1‐1. Notwithstanding the long residence time of TOC in P2‐9, that dated ~17.7 ka, LF was likely fed by fresh input from sporadic vegetation and aeolian materials, but it showed a lower C/N ratio than the other horizons of the same profile.…”

“…The vegetation cover, almost absent (max 5%) or confined to small patches, is composed mainly of alpine species (e.g., Silene acaulis, Carex curvula, Salix herbacea, Festuca halleri, Poa alpina, Ranunculus glacialis, Leucanthemopsis alpina, Cerastium uniflorum, Oxyria digyna ). As reported by Pintaldi et al (2021a, 2021b), no relevant permafrost bodies are present at the site and no significantly negative soil temperatures occur under the blockstreams/blockfields. However, during the snow‐free season, soil temperatures are generally colder under the periglacial features than in the surrounding snowbed soils covered by vegetation.…”

“…Geophysical investigations indicated that these hidden soils are widespread on the Plateau. A detailed description of the soil profiles, as well as their physical and chemical properties, distribution and thickness are reported in Pintaldi et al (2021a), while their age, origin and possible palaeoenvironmental reconstruction are reported in Pintaldi et al (2021b).…”

“…Thus, plants could survive the severe conditions of glacial periods on nunataks, with the latter serving as a source for the rapid reoccupation of the later deglaciated landscape (Fairbridge, 1968). Although several studies have been focused on nunataks at high latitudes (e.g., Birks, 1994; McCarroll et al, 1995; Ballantyne et al, 1998; Paus et al, 2006), very few works studied nunataks in the European Alps (Schönswetter et al, 2005; Birks & Willis, 2008; Carcaillet and Blarquez, 2017; Pintaldi et al, 2021a; Pintaldi et al, 2021b), probably due to the intrinsic difficulties in finding relict surfaces preserved from glaciations.…”

“…(Pintaldi et al, 2021a). Despite the thick and complete stony cover, and the extremely sparse vegetation, these soils showed OC stocks comparable to alpine tundra or even to subalpine forest soils and were classified by using 14 C dating as palaeosols that have recorded the main warming climatic phases occurring since the end of the Last Glacial Maximum (Pintaldi et al, 2021b). This suggests that the environmental conditions on the Plateau were probably suitable for alpine plant life and pedogenesis, already 22–21 ka BP.…”