1:45 PM - 3:15 PM
[O11-P11] Microfossils from the Fukuji Area in Gifu Prefecture
Keywords:Microfossil, Fukuji, Devonian
The study focuses on the Devonian Fukuji Formation in the Fukuji region of Oku-Hida Onsengou, Takayama, Gifu Prefecture. Fossils such as Favosites (Kamei, 1955), stromatoporoids, and brachiopods (Tanaka et al., 2019) have been reported from thin rock slices and by naked-eye observation. In contrast, acid treatment for extracting microfossils has been applied mainly for radiolarians and conodonts (Tsukada and Koike, 1997; Kurihara, 2004).
In my previous work, using acid treatment on limestone samples from the Fukuji region, I extracted microfossils including sponge spicules, bryozoans, and ostracods. Notably, sponge spicules with six rays, as well as three- and eight-rayed forms, were found to resemble those of the Heteractinida class, which has not been reported from Japan. However, efforts were made to locate fossils that preserved the complete sponge spicules, since spicules alone are insufficient for identification at the genus or species level.
The study aims to classify and quantify microfossils based on their morphology in order to infer the Devonian biota and to determine efficient extraction conditions regarding acetic acid concentration and treatment time. Because the outcrops are part of a designated natural monument, sample collection was conducted with permission, by collecting pebbles from a stream. The rocks were crushed, treated with 10% acetic acid for between 50 and 144 hours, and then sieved using mesh sieves. After drying, the microfossils were observed and photographed using a stereo microscope and a scanning electron microscope (SEM).
The results showed that 595 microfossils were extracted from 20 pebbles.The six-rayed sponge spicules were the most abundant, suggesting that members of the Heteractinida class once lived in the region. However, no complete sponge fossils were found. Future work will include implementing an image recognition system and the development of a database to enhance microfossil detection and further advance research.
In my previous work, using acid treatment on limestone samples from the Fukuji region, I extracted microfossils including sponge spicules, bryozoans, and ostracods. Notably, sponge spicules with six rays, as well as three- and eight-rayed forms, were found to resemble those of the Heteractinida class, which has not been reported from Japan. However, efforts were made to locate fossils that preserved the complete sponge spicules, since spicules alone are insufficient for identification at the genus or species level.
The study aims to classify and quantify microfossils based on their morphology in order to infer the Devonian biota and to determine efficient extraction conditions regarding acetic acid concentration and treatment time. Because the outcrops are part of a designated natural monument, sample collection was conducted with permission, by collecting pebbles from a stream. The rocks were crushed, treated with 10% acetic acid for between 50 and 144 hours, and then sieved using mesh sieves. After drying, the microfossils were observed and photographed using a stereo microscope and a scanning electron microscope (SEM).
The results showed that 595 microfossils were extracted from 20 pebbles.The six-rayed sponge spicules were the most abundant, suggesting that members of the Heteractinida class once lived in the region. However, no complete sponge fossils were found. Future work will include implementing an image recognition system and the development of a database to enhance microfossil detection and further advance research.