Fluvio-glacial deposits

Ice (a) Glacial till (moraines, till plains, drumlins, etc.) (b) Fluvio-glacial deposits (eskers, terraces, outwash plains, etc.) Unstratified heterogeneous mixture of boulders, gravel, sand, silt, and clay. Stratified, usually granular. 

Block diagram of a glaciated valley showing typical glacial and fluvio-glacial deposits. 

Silts are clastic sediments derived from pre-existing rocks, chiefly by mechanical breakdown processes. They are composed mainly of fine quartz material. Silts may occur in residual soils, but they are not important in such instances. However, silts are commonly found in alluvial, lacustrine, fluvio-glacial and marine deposits. These silts tend to interdigitate with deposits of sand and clay. Silts are also present with sands and clays in estuarine and deltaic sediments. Lacustrine silts are often banded. Marine silts may also be banded. Wind-blown silts are generally uniformly sorted. 

A gravel deposit consists of a framework of pebbles between which are voids. The voids are rarely empty, being occupied by sand, silt or clay material. River and fluvio-glacial gravels are... 

Fluvio-glacial soils have been transported and deposited by meltwater and are therefore more sorted and stratified than tills. Many of such deposits consist of gravel and sand characterised by low relative densities. Pockets of very low density can generate geotechnical problems in foundation works. Also voids may appear during or even after construction, possibly caused by melting of ice blocks that have been deposited within the gravel (Price, 1986). 

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