Nonglacial

Nonglacial is an adjective used in geology, geomorphology, and related fields to describe conditions, layers, or landscapes that were not affected by glaciers. It denotes that, in the time or place under discussion, glaciers were absent or did not advance across the area. The term is relative; a region may be nonglacial while neighboring areas experienced glaciation, and nonglacial conditions can occur during generally cold periods if ice sheets do not reach that locale.

In stratigraphy and sedimentology, nonglacial sediments are those formed by non-glacial processes such as rivers, lakes, wind, or landslides. They contrast with glacial deposits like till, outwash, and moraines, which record ice advancement. Nonglacial deposits often reflect fluvial or lacustrine environments, as well as aeolian (wind-blown) processes, and can include alluvial sands and silts, lake sediments, and loess in some regions.

In the context of the Quaternary climate, nonglacial intervals correspond to periods when ice coverage in the region was minimal or absent, such as interglacials or certain interstadials. However, nonglacial conditions are not guaranteed across all areas during these times; some places may retain localized or incomplete glaciation. The nonglacial record helps scientists distinguish landscape evolution driven by ice from that driven by rivers, winds, and other non-glacial processes.

Identification relies on proxies and sedimentary facies, including pollen assemblages, fossil communities, isotopic data, and the nature of sedimentary layering, to infer a lack of glaciation and non-glacial environmental conditions.