[H-QR04] 第四紀：ヒトと環境系の時系列ダイナミクス

[HQR04-P01] The Study on Diatom Assemblages of the Lacustrine Sediment in the Tunlumei Pond in Central Taiwan

*Zih Wei Tang¹、Liang Chi Wang²、Huei Fen Chen¹ (1.Institute of Earth Sciences, National Taiwan Ocean University、2.Department of Earth and Environmental Sciences, National Chung Cheng University)

キーワード：indicator, Tunlumei Pond, precipitation

Most of the paleolimnological studies in lowland lakes in the north, northeast or south of Taiwan have been done, the lacustrine records in the alpine Taiwan are still rare. To improve the understandings of paleoenvironment changes in alpine Taiwan, we drilled a 290-cm long sediment core TLM-1 in the littoral side of Tunlumei Pond (TLM), which a small pond situated in Nenggao Mountain at Nantou Country of central Taiwan. Chronologies of the core were determined by ²¹⁰Pb and ¹⁴C dating. The sedimentation rates are approximately 0.1 cm per year. For the diatom analysis, we removed the organic matters in the sediments by using hydrogen peroxide, and identified the diatom to species level with light microscope under 1000X magnification. Consequently, the diatom valves were only preserved in upper 95 cm of the core TLM-1, and we identified 34 genera and 83 species of fossil diatoms. Most of them are benthic diatoms, but the most abundant species, Staurosirella pinnata dominates both in benthic and planktonic environments. The pH preference of the diatoms are mainly alkaliphilous and circumneutral, and only Eunotia intermedia is acidophilous. For the tropic preference, On the basis of cluster analysis, the 4 diatom stratigraphy zones were identified. There are two depths in poor diatom preservation of core TLM-1, 45cm and 85cm. Suggest the pond boundary is not reaching study site in that two periods. In zone 1 (95-70cm, 750-610 cal. BP), the akaliphilous species S. pinnata was dominant (30-85%). In zone 2 (70-53cm, 610-540 cal. BP), S. pinnata was replaced by the circumneutral species Planothidium lanceolatum (20-35%). The benthic/planktonic species S. pinnata decreased and most of the benthic species increased. It implied that the water level became shallow in zone 2. In zone 3 (53-28cm, 540-350 cal. BP), S. pinnata was dominant again, but the acidophilous species Eunotia intermedia presented a remarkably increase during 540-470 cal BP, which may link with frequent hydrological disturbances, such as typhoon events or heavy rainfall. In zone 4 (28-10cm, 350-80 cal. BP), S. pinnata was continued to dominant, and another species were in low content, indicating the stable pond environment as today.