Definitions:

1. The layer in a soil profile below the B-horizon and immediately above the bedrock, consisting chiefly of weathered, partially decomposed rock. NOUN
   • The excavation revealed artifacts resting in the C-horizon, indicating ancient human activity beyond the reach of standard archaeological digs.
2. The lowermost soil level zone, consisting mainly of unconsolidated, weathered rock fragments. ADJECTIVE
   • During the field study, they took samples from the C-horizon to analyze the original geological material of the soil profile.

Synonyms:

• basal soil layer
• parent material layer
• substratum
• weathered rock layer