Diatom is a single-cell algae, which lives in marine, brackish and fresh water. As the flustules of diatom had often preserved in sediments, diatom fossil can be an useful indicator of paleo-environments.
The perpose of this paper is to reconstruct the paleo-geographical changes of alluvial plains and coastal plains in Japan. using the data on the successions of diatom fossil assemblages in alluvial deposits.
At first, the author collected the lake bottom sediments and living diatom samples in 5 brackish lakes in Japan, in order to consider the distribution-patterns of living and dead diastoms. Based on this contribution, species of diatom can be classified into 12 groups by ecological conditions, as follows.
Fa group is composed of Eunotia praerupta, Pinnularia viridis et al., which live in boggy environment.
Fb group is composed of Melosira granulata, Stephanodiscus astraea et al., which are plankton and live in water surface of fresh water lakes.
Fc group is composed of Cymbella minuta, Gomphonema parvulum et al., which are epiphitic species and live in lake shore and shallow lake bottom.
Fd group is composed of Synedra ulna, Ceratoneis vaucheriae et al., which live in river.
F•B group is composed of Bacillaria paradoxa. Rhopalodia gibberula et al., which live in fresh to oligohaline brackish water.
Ma group is composed of Cyclotella striata v, subsalina, which is plankton and lives in oligohaline to mesohaline brackish lagoon.
Mb group is composed of Diploneis smithii, Cocconeis scutellum et al., which are epiphitic species and live in polyhaline brackish lagoon.
Mc group is composed of Achnanthes brevipes v. intermedia, Achnanthes hauckiana et al., which are epiphitic species and live in estuary.
Md 1 group is composed of Nitzschia granulata. Nitzschia lanceolata et al., which are epiphitic species and live in inner part of deltaic area.
Md 2 group is composed of Dimerogramma minor, Rhaphoneis surirella et al., which are epiphitic species and live in the delta front.
Me group is composed of Paralia sulacata, Thalassionema nitzschioides, which are plankton and live in inner bay and polyhaline brackish lagoon.
Mf group is composed of Thalssiosira excentrica, Coscinodiscus radiatus et al., which are plankton and live in ocean surface.
And then, the authuor observed diatom fossil assemblages in alluvial deposits, from the 25 localities of alluvial plains and coastal plains in Japan.
“Marine transgression” in early Holocene and “Marine regression” in middle to late Holocene, both of which are represented by diatom fossil assemblages, are observed in every localities.
“Marine transgression” in early Holocene can be clasified into two series, “estuary-delta-innerbay” series and “river bottom plain-innerbay” series.
On the other hand, “Marine regression” in middle to late Holocene can be classified into three series: “innerbay-estuary-flood plain” series, “innerbay-tidal flat-valley bottom plain” series and “innerbay-lagoon-peat land” series.
“Estuary-delta-innerbay” series and “innerbay-estuary-flood plain” series are observed in such big river mouth areas as River Tama. “Vallery bottom plain-innerbay” series and “innerbay-tidal flat-valley bottom plain” series are observed in such small valley bottom plains near sea shore as Haibara plain. “Innerbay-lagoon-peat land” series is observed in such lowlands behind beach ridges as Ukishimagahara plain.

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The vegetation landscape of the Kuranosuke Cirque, Northern Japanese Alps, was analysed from a geoecological viewpoint. First, the alpine zone of the cirque was physiognomically divided into the following four units on the basis of surface conditions: Pinus pumila-covered area, Alpine meadow, Bare ground, and Perennial snow patch (Fig. 4). Among various climatic, topographic and geologic factors which determine the vegetation landscape, the following six are chosen for the present analysis: 1) maximum snow depth, 2) snowmelt period, 3) surface material, 4) slope form, 5) mean slope gradient, and 6) surface processes such as gelifluction, alpine debris flows and rockfalls. Distributions of each factor in the cirque were mapped at the scale of 1:5, 000, on the basis of the air-photo interpretation and periodical field observations (Figs. 5 to 12). Grid analysis (50m×50m grid) allowed a systematic treatment of the data. The results of the mapping (Fig. 13) revealed that 1) Pinus pumila-covered area is subdivided into Pinus pumila-covered boulder area (P-I) and Pinus pumila-covered rubble area (P-II); and 2) Bare ground is subdivided into Wind-beaten bare ground (BG-I), Snowy bare ground (BG-II), Intermediately snowy boulder area (BG-IIIa), and Rock walls and Talus slopes (BG-IIIb), according to the conditions of maximum snow depth and surface material (Fig. 14). These six categories, together with Alpine meadow (AM) and Perennial snow patch (S), are called landscape units; which correspond to Ökotop defined by Troll (1971). Figure 15 summarizes the relation between each landscapee unit and six alpine environmental factors, and Figure 16 show, the spatial distribution of the landscape units on the cirque.
The results of this analysis clarified: 1) the mean gradient is not an important factor to classify landscape units 2) the mean value of maximum snow depth is effective to classify landscape units ; however, 3) the range of maximum snow depth of one landscape unit overlaps with that of another; 4) surface material, slope form, and surface processes play an important role to classify the landscape units which are not determined only by maximum snow depth, and 5) the lack of Pinus pumila community over Intermediately snowy boulder area (BG-IIIa) which has the maximum snow depth allowing its growth, is explained by the slow speed of invasion of this plant from the surrounding areas.

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