Terrigenous particles have been eroded from the land outside the body of water experiencing the deposition.
Most terrigenous particles originate from bedrock.
The particles either retain their chemical make-up, or become chemically altered to clays and iron oxides. Particles include rock fragment, single crystals, or bits of volcanic glass. Carbonate biocrystals are secreted by marine organisms such as foraminifers and mollusks. Sediment forms when these calcium carbonate skeletons are broken down physically or biologically. Silica biocrystals are formed by diatoms, sponges, and dinoflagellates.