paleoglacials

Paleoglacials, or paleoglaciations, are past episodes of substantial glacier advance and ice-sheet expansion in Earth's history. The term encompasses both regional glaciations and episodes with more widespread ice cover, and it is used in geology and paleoclimatology to describe intervals when preserved landforms and sediments indicate former glaciation. Evidence includes moraines and drumlins, polished and striated bedrock, glaciofluvial gravels, till, glaciolacustrine sediments, varved lake sediments, dropstones in marine deposits, and associated fossil assemblages.

In the most recent portions of the Quaternary, the Last Glacial Maximum around 26.5–19 thousand years ago marked a continental-scale paleoglacial phase with ice sheets over North America, northern Europe, and parts of Asia. Earlier paleoglacials occurred during multiple Pleistocene glacial cycles; before the Quaternary, Neoproterozoic and Paleozoic ice ages (sometimes framed as Snowball Earth episodes) left evidence in glaciogenic sediments and diamictites across continents. The term commonly emphasizes regional-scale ice while acknowledging that some events were near-global.

Dating and interpretation: Paleoglacials are dated with radiometric methods (such as 40Ar/39Ar), radiocarbon for the younger features, optical or luminescence dating, cosmogenic nuclide exposure ages, and varve chronology. Marine isotope records, loess deposition, and paleomagnetic data supplement regional reconstructions. Studying paleoglacials helps illuminate climate sensitivity to orbital forcing, greenhouse gas fluctuations, tectonics, and feedbacks that shaped Quaternary and pre-Quaternary climate.