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- n. Plural form of tillite.
Sorry, no etymologies found.
The continuity of glaciers, inferred from oriented glacial striations and deposits called tillites, suggested the existence of the supercontinent of Gondwana, which became a central element of the concept of continental drift.
The controversy was that these rocks may not have signified glaciation, so they shouldn't be called tillites, but rather diamictites.
I found some in the Numees formation of South Africa just above tillites.
But at a quick look, temperatures are assigned to certain types of fossil formations: coal, bauxite, etc. on the warm side and tillites on the glacial side.