A lithofacies classification as a tool in the reconstruction of the Pleistocene depositional environments in the western coastal plain

This paper is the outcome of the project “Updating the Quaternary database of the Belgian Geological Survey”(November 2010 – March 2013). The objective of the project was to provide a useful and relatively quick method for borehole description and for the reconstruction of the depositional environment, applicable on the whole of the Quaternary deposits. The western coastal plain of Belgium has been selected as pilot area because of the existence of about 100 high-quality undisturbed mechanically-drilled cores recovering the whole Quaternary sediment succession until the Tertiary substratum. The investigation focuses on the Pleistocene deposits that hitherto have not been studied in detail; this in contrast to the Holocene deposits. Moreover, their existence is even hardly known. This study is made as a model study. The first part of the paper illustrates step by step the procedure followed in order to reconstruct the depositional palaeo-environments. Much attention is paid to the definition of lithofacies as they are the basic tool in the reconstructural procedure. Because these lithofacies are so fundamental in particular for further use, most of them are illustrated with photographs. In a next step the lithofacies are combined into facies associations and sedimentary subenvironments are defined. The goal of the study, viz. the reconstruction of the environment, is obtained by combining the facies associations. These environments are then part of a larger entity namely the depositional system. In the second part of the paper the application of the classification on the Pleistocene deposits in the Western Coastal Plain of Belgium is described and discussed.