detritus

Short definition from Wiktionary

Noun

1. 1
   Pieces of rock broken off by ice, glacier, or erosion.
2. 2
   Organic waste material from decomposing dead plants or animals.
3. 3
   Any debris or fragments of disintegrated material.
4. 4
   Rock consisting of accumulated debris from decayed rocks, like sand, that often is joined by cement.