Eolian Additions to Soils and Sediments of Japan

Open Access
Publisher Website
Google Scholar
Abstract
Significance of the eolian additions to soils and sediments of Japan was evaluated. Soils overlying Paleozoic limestone, Ando soils developed on volcanic ashes, eolian dusts in a mud rain deposit, snow melt and ombrogenous Sphagnum peats from Japan and South Korea, and loes! from North China were analyzed for the particle-fize distribution and oxygen isotopic composition of a marker mineral quartz. The total quartz content of the soils overlying limestones was much higher in the surface horizons (30 to 40%) than the subsurface horizons (3 to 14%). The whole quartz content within cumulative Ando soils varied from 9–11% in the lower buried horizons (8,000–l50,000 years B.P.) to 1–2% in the upper recent horizons (18O value, expressed as parts per thousand variation relative to Standard Mean Ocean Water, SMOW) of fine quartz silt (1 to 10 μm in diameter, characteristic of long-distance aerosolic dust) of soil and sediment samples showed values of +16.3 to +17.0‰ (North China) and +14.7 to +16.1‰ (Japan). Those values are in agreement with those previously reported for fine quartz from the North Pacific pelagic sediments and the Hawaiian soils, and characteristic of the eolian dusts of the mid-latitude zone of Eurasia. These values correspond to the average composition of quartz of the earth’s crust. A well-mixed reservoir in the source is inferred for the soil quartz. The quartz from underlying limestones and volcanic material has totally different isotopic compositions, and cannot be the source of the soil quartz. The correspondence between the two parameters of quartz strongly suggests their common eolian input from arid and semi-arid regions in Asian interiors to the soils. Local eolian contribution from dry-river bed and/or beach and volcanic ash, quartz of whose predominant size is 30 to 40 μm is evident for some Ando soils from Kagoshima, Shizuoka and Hokkaido. The framework of 14C dating, together with the stratigraphic correlation of marker tephras, suggests that the long-distance eolian additions were much greater in the last glacial maximum period (18,000 years B.P.) than in the Holocene.