In the Japanese Islands, alluvial fans had developed best during the period corresponding to the last glaciation of the glaciated regions of high latitudes and high altitudes in the world. Many alluvial fans of this age cover aggradationally the inland parts of the older fluvial and coastal plains, though the base-level of gradation prevailed along the coasts and rivers was lowered consistently with lowered sea level. Temperature on land indicated by the fossil flora was lower than the present, but no significant glaciation occurred in Japan. Possibly climate controlled mass-wasting and fluvial processes with unbalanced precipitation besides low temperature.
