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). The fabric is furthermore characterized by planar voids with dark fringes that probably resemble burned vegetal mater.
