Tillite is a large variation in grain size – from powder to clasts ofseveral metres – is typical in this rock and gives rise totillite’s other name: boulder clay . In the past, material wasground up and transported as a result of a glacier movingdown a valley; when the glacier melted, it deposited itsentire load of materials or till. The resultant rock, tillite,is common in geologically recent deposits of ice ages innorthern Europe and North America, but also foundin older rocks.
- GRAIN SIZE: Less than 0.005mm to many metres.
- ESSENTIAL COMPONENTS: Commonly rockfragments.
- ADDITIONAL COMPONENTS: None
- ORIGIN: Detrital, from coarse angular sediment.
- SIMILAR ROCKS: Breccia