The matrix is reddish-brown, silty, calcareous and optically active with small amounts of calcareous sand. The quartz silt is about 20% and also contains some heavy minerals (including mica and hornblende) as well as common opaques. The calcareous sand consists of rounded chalk grains (up to 150µm). Rare are sub-rounded chalk and limestone grains (up to 300µm) as well as shell (up to 200µm).
