福岡市天神地域の後期更新世-完新世堆積物の花粉分析学的研究, その1
1978 年 17 巻 1 号 p. 1-14
詳細
1978 年 17 巻 1 号 p. 1-14
The writers attempted to clarify the late Quaternary stratigraphy and climatic change through the subsurface sections in the central part of Fukuoka City on the basis of pollen analysis. Four pollen zones were recognized, which respectively correspond to FG, RI, RII and RIIIb zones of NAKAMURA, J. (1952, 1967, 1975a, 1975b) and TSUKADA, M. (1963, 1967, 1974) in ascending order. In view of paleoclimate, these pollen zones represent respectively a climatic period.
1. Cold period (FG zone): the peat layer (910-950cm) is mainly characterized by north temperate elements, such as Abies, Tsuga, Betula, Carpinus, Fagus, Ulmus, Tilia, Alnus, etc. and wholly excludes south temperate elements such as Celtis, Shiia, Cyclobalanopsis, Gleichenia, Pteris, etc. North temperate forest probably expanded to the low land with its lower boundary about 1000-1500m lower than that in the present day.
2. Cold period (RI zone): the beds (838-895cm) consisting of irregular bodies of sands, silts and gravels hold very poor pollen records. The result is not effective to correlate this section decidedly with RI or LG zone (L zone) and so we tentatively correlate it to RI zone on the basis of the geological field data. In general RI is regarded as a transition zone between the cold period LG (L) and the next warm period RII.
3. Warm period (RII zone): it is generally accepted that the colder forest of the former period was pushed away by such south temperate elements as Shiia and Cyclobalanopsis which became dominant. However there are small quantities of north temperate elements throughout these layers (680-838cm). While Celtis decreases at the upper part of these layers, Cyclobalanopsis and Shiia increase.
4. Decreasing warm period (RIIIb zone): the peaty mud layer (365-400cm) is characterized by a large quantity of Pinus, while evergreen broad leaved species are not many. Cereal pollen were also recognized in the samples from. this section. The above facts suggest destruction of forest and agricultural activities by man as NAKAMURA, J. (1971, 1975b) and TSUKADA, M. (1974) pointed out.
14C age of molluscan shells from about 4m level under the ground surface was 5540±100y.B.P. (KURI 185, T. SAKATA) and that of pieces of wood from 9.5m level, 20600±400y.B.P. (KURI 186, T. SAKATA). These 14C dates reinforce the correlation of our pollen zones to the zones FG, RI and RII.
