Glacial Deposits

geological deposits whose formation is genetically related to modern or ancient mountain glaciers or continental ice caps. Glacial deposits are divided into glacial deposits proper (or moraine) and aqueoglacial deposits.

Glacial deposits proper arise when fragmentai material carried within the glacier is directly deposited beneath the glacier. These deposits are composed of unsorted loose fragmentai rock, more often boulder clay, loams, and sandy loams and, more rarely, boulder sands and coarse gravel containing boulders, rock debris, and pebbles.

Aqueoglacial deposits are formed inside and along the periphery of glaciers from sorted morainic material that has been redeposited by meltwaters. Among these deposits a distinction is made between glaciofluvial deposits, which are the deposits of streams of meltwater (obliquely bedded sands, gravel, and shingle), and glaciolacustrine deposits of englacial and periglacial lakes (predominantly varved clays).

All types of glacial deposits form complicated combinations (glacial complexes or glacial formations). They are particularly characteristic for the youngest Anthropogene system, during whose formation extensive continental glaciers covered enormous areas in the present-day temperate zones. Among the deposits of the Upper Paleozoic, the Ordovician, and the Pre-cambrian, ancient glacial deposits are also known; they are usually greatly consolidated, cemented together, and sometimes also metamorphosed (tillites).