Deformation of laminated silt loam due to repeated freezing and thawing cycles

The effect of repeated freezing and thawing cycles on an experimentally‐produced laminated silt loam was studied with the purpose of obtaining more insight into the genesis of macro‐ and microstructures observed in the loessic formations of Northwestern Europe. The laminated silt loam was subsequently subjected to 18 cycles of alternate freezing and thawing. The minimum temperature recorded after 11 days of frost was − 7°C at a depth of 5 cm and − 4°C at 29 cm. The underlying sediments, compact loam (except its upper part) and sand, always remained unfrozen. The experiment reproduced a seasonal superficially frozen ground. New structures and microfabrics in the form of vesicles, platy structures, shear planes, and micro‐undulations were created by ice segregation and thawing, mechanical stress and subsequent frost‐creep. The impact of the freezing and thawing cycles is very strong, all the laminae being deformed or broken. Judging by the abundance and the diversity of the structures created, freezing is a more important process than simple drying without frost. As is evidenced by the range in temperature chosen for the experiment and the low number of cycles, these structures do not necessarily require severe climatic conditions to develop, unlike frost cracks or ice wedge casts. They could develop in winter conditions similar to those present today in the French Southern Alps.