Depositional environment of the glacigenic deposits from the Holy Cross Mountains (Poland) – interpretation based on macro- and microstructure analyses

Abstract

In this paper an attempt is made to identify the depositional environment of glacigenic deposits from the central part of the Holy Cross Mountains (Kielce-Łagów Valley). In this area, the primary glacial relief is very poorly visible, mainly due to its modification by subsequent denudation processes. The study is based on detailed sedimentological (macro- and microstructural) analysis of the deposits. The bottom part of the deposits consists of gravelly and sandy facies. They are overlain by diamicton facies, with a small proportion of sandy facies. Clayey/silty facies occur in minor quantities. The investigations indicate that these deposits represent an ice-marginal environment. Local stagnation of the ice sheet lobe was controlled by the geological structure of bedrock (karstified and faulted limestones) and the features of a fossil valley. The ice-marginal depositional environment is indicated by the predominance of sediment-gravity flow deposits, a low proportion of sorted deposits, as well as the interfingering/alternating of mass flow deposits and waterlain deposits. Deformation occurring in the deposits is of gravitational origin. They also show traces of periglacial processes. The deposits constituted an ice-marginal moraine (dry end moraine with limited topographic expression). Micromorphological analyses provided data for genetic identification of the deposits, and allowed the inference about rheology of deposition and deformation processes. However, in some cases, they did not allow unequivocal genetic classification of the deposits. The results of presented investigations confirm the opinion that detailed and complete explanation of deposit origin requires both micromorphological analyses and macroscopic field sedimentological and structural studies.