The late Quaternary deposits in the Kurobe river mouth were laid down in relation to the change of the sea level. From geology of this fan and the adjacent area, the nature, distribution, depositional history and the volume of this fan deposits were made clear. More than 4.4 km³ of deposits have been carried in the sea by the Kurobe river since the beginning of the post glacial age. This mass has been deposited within 110 km² area of the fan and adjacent portion of the continental shelf. There are several submarine forests around the Toyama bay. The stage of the forests is from the late Jyomon to the early Yayoi, judging from the age of the peat beds around them. And this fact has shown that the sea level was 0〜-2 m below the present sea level at that time and the east part of the Toyama plain has upheaved and the center of it has sunk in the vertical earth movement.