eluvium

/ɪˈluːviəm/
noun
  1. A deposit of soil, dust, or rock debris that has been formed by the weathering of rocks in place, without being moved by wind or water.
    • The garden's soil was rich in eluvium from the nearby granite outcrop.
    • Geologists study eluvium to understand how local bedrock breaks down over time.
    • The hiker noticed a layer of eluvium at the base of the cliff, made of broken rock fragments.