Macro‐ and Micromorphologic Interpretation of Relict Periglacial Slope Deposits from the Holy Cross Mountains, Poland

Relict periglacial slope cover deposits in the Holy Cross Mountains of Poland are composed of material derived from bedrock, loess and sand of polygenic origin. The aim of this study was to interpret the processes that deposited three massive coarse‐grained diamictons near the base of gentle hillslopes. Based on macroscopic and microscopic sedimentological analyses, the diamictons are attributed to deposition by three processes – active‐layer detachment, solifluction and high‐energy overland flow – due to climatic and geomorphologic factors. The use of microscopic analysis revealed the detailed texture and structure of these deposits, and was particularly important in interpreting fine‐grained sediments produced by low‐energy overland flow. This technique served as the basis for the differentiation of solifluction deposits and high‐density flow deposits. The active‐layer detachment deposit (adjacent to the slip plane) was characterised by a heterogenous texture and breccia‐type structure with domains and clasts oriented parallel to the slope. The deposit included erosional surfaces and individual slip planes. The solifluction deposit was a clayey diamicton with a banded structure oriented parallel to the slope. The low‐energy overland flow deposit was laminated and sorted with laminae oriented parallel to the slope. The high‐energy overland flow deposit was a homogeneous and massive diamicton with a silty/sandy matrix and randomly oriented clasts and grains. The following characteristics helped identify the sediment type: the degree of homogenisation, texture, sedimentary structure and fabric. Features including plasmic fabric, deformation structures and microporosity played an additional role in identifying the studied deposits. In relict slope deposits, these features may be formed as a result of depositional or postdepositional processes. Copyright © 2015 John Wiley & Sons, Ltd.