Thick A horizons are typically associated with which type of soil formation?

Thick A horizons indicate a significant accumulation of organic matter and soil development through processes such as weathering, leaching, and the addition of plant material. This typically occurs in areas where soil formation processes allow for the buildup of topsoil due to the deposition and breakdown of organic content.

Colluvium consists of material that has been deposited at the base of slopes through gravitational movement. Because this material is often derived from a variety of parent materials and can be mixed with organic material from vegetation above, colluvial soils can exhibit thick A horizons where organic matter accumulates effectively.

In contrast, outwash, till, and residuum have different formation processes. Outwash deposits are primarily formed from sediment transported by meltwater from glaciers, resulting in well-sorted sediments but typically less pronounced A horizons due to the lack of significant organic matter accumulation. Till, made from unsorted glacial debris, is usually characterized by a more varied texture and often has thinner A horizons due to its compact and mixed nature. Lastly, residuum, which develops directly from bedrock weathering, may have thick A horizons in some cases, but typically does not accumulate organic content as effectively as colluvium where vegetation plays a more significant role in soil development.

Thus,