They started to form during Saale glaciation and the formation process lasted for several glacial advances. XRD analysis shows that phosphatic pebbles and Mickwitzia valves from the Kakum e Beds consist of apatite, pyrite, and quartz. The lattice parameter a of F-apatite ranges from 9.345 to 9.367 and c from 6.881 to 6.887 . Pebbles contain the same apatite variety. Although the valve sculpture is variously preserved, the shell structures appeared to be lost.
Shells consist of apatite-cemented quartzose silt and sand.
The observed structure and mineral composition have formed via phosphatization of a primarily organic-rich shell. Fraxinus was first recorded about 6500 BP from East Estonia. Carpinus is a late immigrant which reached Estonia in the Sub-Boreal. Oak immigrated from the southwest and, in contrast to elm, spread very slowly. Meeting the challenges for 2000 2004.