Tubulichnium Ksiazkiewicz 1977

Ichnogenus Tubulichnium Książkiewicz, 1977(Fig. 2) Tubulichnium is an oblique to horizontal, unbranched, blindending tube showing some internal organization due to slight vertical shift; the margins are densely lined with ellipsoidal muddy pellets. The sequestration of material, which is then stowed in muddy laminae and pelleted fill, is documented by its composition: it contains c. 1.5% Corg and 20% CaCO 3 compared to c. 1.1% Corg and c. 26% CaCO 3 in the host sediment and 0.7% Corg and 12% CaCO 3 in the overlying mud in the studied Upper Cretaceous to Paleogene specimens (Uchman & Wetzel 2017). These data point to selective enrichment of organic-rich particles in the burrow. Microbial activity during priming may generate CO 2 that lowers alkalinity and fosters the dissolution of carbonate (van Nugteren et al. 2009). Although no clear spreite is developed, a partly laminated fill exhibiting local truncations (Fig. 2B, C) suggests utilization of the stowed material, as in the case of Zoophycos. TUBULAR OPEN BURROW SYSTEMS