A historical outline of the Eemian research in the Netherlands is presented as an introduction to recent research in the type area. At the end of the 19th and during the first part of the 20th century, Eemian sediments were recognized because of the presence of lusitanian and mediterranean mollusc species. From 1930 onwards, pollen analysis made it possible to identify also non-shell-bearing deposits and to equate them with the Eemian. At the same time this technique proved a valuable tool for understanding the vegetation development during this interglacial. Pollen zonation offered a unique possibility for the correlation of terrestrial sequences in North-West Europe.
The type area of the Eemian, near Amersfoort, was described by Harting in 1874 and was comprehensively restudied by Zagwijn (1961). A pollen zonation was introduced as a standard for the Netherlands, allowing the correlation of pollen records from both marine and non-marine depositional environments. This enabled a more detailed temporal resolution, resulting in a better understanding of the distribution of the various environments in the type area.
In the northern and central parts of the Netherlands, the identification of the marine sequence was, apart from the occurrence of the specific mollusc fauna, facilitated by the presence of a till of Saalian age underlying the Eemian deposits. The presence of deep glacial basins in these areas enabled the deposition and preservation of a complete Eemian record in a marine setting. Sediment accumulation in the basins began immediately following deglaciation at the end of the Saalian. The Eemian type sections at Amersfoort are situated near the margin of one of these basins.
Recent research of the Eemian focused on the integration of lithostratigraphic evidence and information on the sedimentary environment as derived from diatoms, dinoflagellates, foraminifers, molluscs and pollen.