Abstract
The Late Pleistocene Maibara and Kaisaka Loam Formations, consisting of weathered eolian deposits, are widely distributed in Niigata and Nagano Prefectures, Central Japan. Plants preserved fossil-charcoal are identified from these formations. The fossils consist of small angular fragments (mostly 1 to 50 mm diameters), a dull black lustre, brittle fracture and homogenised cell wall. H/C thermometer indicates that the fossil charcoal fragments were charred in the range 430-460°C. Stratigraphically, the fossil charcoal, indicating the occurrence of wildfire, have been recognized at three stratigraphic levels, called Tsunan-1, Tsunan-2 and Tsunan-3 fossil charcoal horizons, in these formations. Tsunan-1 fossil charcoal exists at the horizon between the M 4 and M 3 tephra bed (ca.110-120 ka), and is widely distributed in Niigata and Nagano areas, for a distance of more than 50 km. Tsunan-2 fossil charcoal occurs at a horizon of immediately above the M 6 tephra bed (ca.90-100 ka), and is sporadically distributed in Niigata and Nagano areas, along the Shinano River for a distance of about 30 km. Tsunan-3 fossil charcoal occurs at a horizon of immediately below the K 0 tephra bed (ca. 70 ka), and is distributed in Niigata and Nagano areas, for a distance of more than 20 km. We conclude that these fossil charcoal horizons are useful for understanding the wildfire history during late Quaternary and are important as stratigraphic marker horizons.
