Saprolite

Saprolites form in the lower zones of soil profiles and represent deep weathering of the bedrock surface.

Saprolites form in the lower zones of soil horizons[1] and represent deep weathering of the bedrock surface.

[1] Although these deeply weathered terrains now occur in a wide variety of climates ranging from warm humid to arid, tropical to temperate, they were formed under similar conditions in the past.

[1] In parts of Africa, India, South America, Australia and southeast Asia, regolith has been forming continuously for over 100 million years.

[1] Similar weathered regoliths exist at much higher latitudes – 35–42°S in southeast Australia (Victoria and Tasmania), 40–45°N in the United States (Oregon and Wisconsin) and 55°N in Europe (Northern Ireland, Germany) – although these are not regionally extensive.

[1] Saprolites form in high rainfall regions which result in chemical weathering and are characterised by distinct decomposition of the parent rock's mineralogy.

[1] Carbonates are highly soluble, especially in acidic environments; the elements hosted by them – calcium, magnesium, manganese and strontium – are strongly leached.

[1] Ferromagnesian minerals are the principal hosts for nickel, cobalt, copper and zinc in sulfide-poor mafic and ultramafic rocks, and are retained higher in the profile than sulfide-hosted metals.

[1] Supergene enrichment occurs near the surface and involves water circulation with its resulting oxidation and chemical weathering.

This is a diagram and related photograph of soil layers from bedrock to soil.
A represents soil ; B represents laterite , a regolith ; C represents saprolite, a less-weathered regolith; beneath C is bedrock .
Saprolite is less weathered than laterite; it is beneath the laterite layer.
Saprolite is not as weathered as laterite; there is a continuum from the upper layer of saprolite to laterite.
Saprolite at Arranmore (Ireland). Transition from tectonized quartzite through saprolite to laterite . The weathered section is covered by glacial drift with scattered erratics, Holocene sandy soil and thin bog .