|Budget Amount *help
¥2,600,000 (Direct Cost : ¥2,600,000)
Fiscal Year 1996 : ¥1,300,000 (Direct Cost : ¥1,300,000)
Fiscal Year 1995 : ¥1,300,000 (Direct Cost : ¥1,300,000)
To understand both mechanism and process on the fossilization of trace fossils, detailed description and analysis on the morphology and mode of occurence of trace fossils in the sediments of shallow- and deep-marine origin were made by means of not only field survey but also labolatorical technique such as soft X-ray photographs, XRD analysis, and thin section observation.
In particular, evaluation of the preservation potential of trace fossil is focused throughout this research project. Detailed observation and analysis revealed that preservation potential of trace fossils is strongly contralled by the difference in mode of sediment supply. In other words, intermittent sedimentation of background sediment should be needed for high preservation potential of trace fossils. A part from trace fossils produced by deep burrowers, stable bottom conditions characterized by a continuous sediment supply lead to low preservation potential of trace fossils. This is because shallower tier members among the trace fossils were obliterated by the overlapping of bioturbated activity of benthic animals through the successive elevation of sea-floor. In contrast, well-preserved trace fossils characterized by high diversity are found from the sediments deposited under the unstable bottom condition. In shallow marine settings, for example, high diversity trace fossil assemblage occurs in the sediments of storm orgin. On the other hand, high preservation potential of trace fossils is understaken for those in the turbidite site in deepsea condition. In conclusion, unstable bottom condition such as the erosion of sediment-surface and a subsequent quick burial may be needed for the higher preservation potential of trace fossils.