What is the typical composition of materials classified as alluvial?

Alluvial materials are typically formed from sediment deposited by flowing water, often found in riverbeds, floodplains, and deltas. The main components of alluvium include silts, sands, and gravels, making them excellent for agricultural use and construction due to their high drainage and nutrient-holding capacity.

Silts contribute to the overall fertility of the soil, while gravels provide good drainage, preventing waterlogging, which is crucial for plant growth. This combination supports various ecosystems and agricultural practices, highlighting the importance of alluvial deposits in both natural and managed landscapes. In contrast, the other options mention materials that do not align with the defining characteristics of alluvial deposits.