2024

Lunkka, Juha Pekka; Ojala, Antti E. K.; Kaakinen, Anu; Hovikoski, Jussi; Kultti, Seija; Kuosmanen, Niina; Mäkinen, Joni; Palmu, Jukka-Pekka; Putkinen, Niko; Sarala, Pertti; Väliranta, Minna; Virtasalo, Joonas

Recent developments in geomorphological mapping and new concepts of sediment classif ication, as well as advances in geochronological methods, have led to a need to review the classification of Finnish Quaternary glacial (mainly Pleistocene) and non-glacial (mainly Holocene) deposits. The Quaternary Sub-Commission of the Stratigraphic Commission of Finland has conducted an overview study on the stratigraphic classification of Finnish Quaternary deposits and introduced the practices according to which these superficial deposits are classified in Finland. The stratigraphic practices for the classification have been dependent on the nature of basic or applied research foci and the availability and development of techniques and media to categorise different aspects of Quaternary sediment strata and their three-dimensional entities. The approaches used to classify Quaternary deposits have included litho-, bio-, and chronostratigraphic, morpho-lithogenetic and hydrostratigraphic, chemo- and pedostratigraphic, magneto- and seismostratigraphic, and sequence and allostratigraphic practices. In addition, absolute dating (e.g., radiocarbon, luminescence and cosmogenic nuclides), incremental dating (e.g., sedimentary varves and tree rings) and relative dating, such as dating based on paleomagnetic paleosecular variation (PSV) and tephras in Quaternary sediments, have been used for the age determination of glacial and interglacial sediment sequences and deposits. Morpho-lithogenetic classification offers perhaps the most comprehensive approach to map and classify Finnish Late Weichselian glacial and the Holocene non-glacial deposits on land. However, litho- and biostratigraphic and absolute dating methods aided by sequence and allostratigraphic approaches are most applicable for establishing a formal litho- and chronostratigraphy for Finnish Quaternary sediments.