Quaternary non-karst caves in tills: A pilot study

Abstract

Caves formed in unlithified glacial sediments are unique elements of geological heritage, unlike underground voids and networks of channels, which occur relatively frequently in Quaternary loess and loess-like deposits. Despite the significant potential for understanding collapse processes in extensive areas covered by glacial deposits, such cavities have been poorly investigated, partly due to their rarity and short lifespans. The paper explores the occurrence of natural caves within Quaternary unlithified tills in northern Poland on the example of previously identified caves (one of which was discovered by the authors). Situated in the northern part of the Polish Lowlands, the caves are located on steep slopes of river valleys and a seashore cliff. During the study, terrestrial laser scanning (TLS) was used to gather detailed morphometric data and create highly accurate cave models of these relatively young objects subject to rapid transformation, thereby providing the opportunity to formulate and discuss preliminary concepts of their genesis. The caves are not long – their length varies from 4.7 m to 11 m – but their morphology and geological conditions, and the interrelations between these features, suggest that these non-karst cavities were formed after the last ice sheet had retreated and that their development was associated with the presence of natural and glaciotectonic fractures within silty tills and with piping processes. These are young forms subjected to constant evolution that will lead to their eventual disappearance.

The gathered data (especially the high-resolution TLS-based models) will be used in the future to monitor transformations and assess the pace of changes. They may also provide an impetus to search for more such objects in fresh exposures on eroded slopes of valleys or banks of waterbodies.