Bulletin of the Mizunami Fossil Museum

Bulletin of the Mizunami Fossil Museum Vol. 50, No. 3 Research reports of the “Paleoparadoxiid Mizunami-Kamado specimen”

Formation processes of calcite concretions co-occurred with the “Paleoparadoxiid Mizunami-Kamado specimen” and calcite fillings formed in bones were studied and discussed based on ge-ological observations and geochemical analyses. The un-deformed fecal pellet-like structures in concretion show that concretions formed before the compaction of sediments. The low δ13C values (approximately −10‰) of concretions and calcite fillings in bones and similar δ18O values to each other suggest that they were formed from organic carbon at almost the same time during early diagenesis. The calcite fillings in bones protect the skeleton from deformation due to the compac-tion of sediments.