Both the Earth's surface and the seafloor are covered with Quaternary deposits and phenomena. Consequently, understanding its structure and composition is fundamental to numerous human usages and activities. This understanding is achieved through the mapping of Quaternary deposits, its correlation and harmonisation, by analysis and interpretation of the results, and ultimately its modelling, visualization and dissemination. This session invites contributions on the challenges of mapping the Quaternary, both offshore and onshore. It includes specific challenges of the marine, mountain and desert mapping in large and small scales, the delineation of permafrost and glacial extents, active fault zones, and the significance of palaeontological and archaeological mapping. Finally, the correlation of stratigraphic and lithological units will be addressed, as a base for a common understanding of the mapped region and its harmonisation with other regions/countries.