This text below is drawn from:
Davies, B.J., 2022. CRYOSPHERIC GEOMORPHOLOGY: Dating Glacial Landforms I: archival, incremental, relative dating techniques and age-equivalent stratigraphic markers. (link)
Multiple methods needed for dating glacial environments
Over the last few decades, multiple methodologies for dating different types of glacial landform have become available to chronologists and geomorphologists. There has been a progression from mostly relying on relative stratigraphies, such as the principal of superposition and morphostratigraphy to radiocarbon dating to constrain the timing of deglaciation , and then on to a wide range of dating methodologies suitable for a range of different environments.
These methods have become increasingly precise, refined and nuanced, and different approaches are now available to date different environments. New tools, such as varve chronologies and tephrochronology, offer ever more precise methods to constrain past glaciations in time, and provide a range of new methods in places that are commonly poor in organic materials.
In most cases, the overall goal of the research project is to constrain in time the extent, thickness, rate of recession or some other property of a past or presently receded ice mass. Therefore, most tools here are concerned with delimiting the ice margins (terminal or lateral moraines, glacier forelands, proglacial lacustrine sediments), either vertically or horizontally. Typically, this involves applying relative and absolute dating methods to glacial landforms formed at the ice margin, such as moraines or outwash terraces, or the timing of formation and duration of the existence of ice-dammed proglacial lakes, to yield the timing of past glaciation.
Different tools for different ages
Different chronological tools are best applied for glacial landforms of different ages. The youngest landforms, that are expected to date from the last few hundred years, are best dated through historical documents and archives, lichenometry, dendrochronology, and relative dating tools such as Schmidt hammer dating. These tools work well for the last approximately decades to 1000 years, but reliability and applicability tends to break down after this. Radiocarbon dating works well for organic materials with an age of ~300 to ~40,000 years.
Cosmogenic nuclide surface exposure dating can be applied to moraines only a few hundred years old to those dating from glaciations in the middle to Late Pleistocene, with uncertainties of around 10%. Similarly, amino acid racemization of shells can cover a time period of 1000s of years to the Mid Pleistocene, but with larger uncertainties (Magee et al., 2009).
Understanding the context: glacial landsystems
Choice of the correct geochronological tool requires a thorough understanding of the geomorphological and depositional context of the landform, post-depositional processes and modifications, as well as an understanding of glacial processes that will affect debris transport pathways and erosion.
For this important reason, all dating campaigns should be strongly grounded in geomorphological mapping, focused on a strong understanding of the process. Related morphostratigraphy can help guide a dating campaign. Adopting a process-based landsystems approach to glacial landscapes will significantly improve the successes of a dating campaign.