科研之友
微信
新浪微博
Facebook
分享链接
摘要
Marine organisms inhabiting soft-bottom sediment are particularly susceptible to rapid sedimentation and erosion events. This article presents a novel example of fossilized intestine casts located within closed bivalve shells in relation to rapid sedimentation event from the Pleistocene sediment of the Oga Peninsula, Akita Prefecture, northern Japan. The mollusc shells were loosely packed in well-sorted medium-grained to coarse-grained sandstone associated with low-angle trough cross-stratification. The closed shells of Glycymeris yessoensis were present in the shell concentration. The internal parts of the shells were almost hollow, being partially filled with yellow fine-grained clay minerals (median grain size=30.63m). The characteristic material within the shells clearly differed from the surrounding sediment, which consisted of coarse-grained felsic minerals (median grain size=449.73m). Furthermore, the yellow fine-grained clay minerals within the shells were tube-shaped, and located near the posterior adductor scar. On the basis of anatomical observation of living Glycymeris, we confirmed that part of the intestine and the anus are also placed near the posterior adductor muscle. Therefore, the yellow fine-grained clay minerals within the shells represent the fossil remains of particles ingested by the G.yessoensis individual through suspension-feeding, and the tube-shaped material is interpreted as being fossilized intestine cast. These results suggest that G.yessoensis individuals were buried alive, as rapid sedimentation prevented ejection and destruction of the filling material of intestine. The presence of intestine cast within the mollusc fossils can be used for recognizing rapid sedimentation.
- 出版日期2015-7
