Depositional Characteristics of Volcanic Debris of Datong Volcano Groups in the Eastern Part of China

Key words: 
• PyToclastic debris /
• Pumice /
• Grain size grade /

Abstract: This article inquires into the changes and composition of vertical and transverse (on land and in water) of fallout and flow detrital deposits of pyroclast sediment in the Datong volcano group. It was discovered that airfall deposits are vertically layered and that the grain size grade and thickness of the vertical accretion deposits L6gularly decreases in correspondence with the distance from the volcanic crater. In flow deposits,however, pumice grain size grade has the reverse relationship. Fine grain sediment generally form at very long distance from the volcano crater, but there are also fine grain deposits close to the crater. This variation.is related to the magnitude of the volcano's extrusive force. Therefore,while coarse grain fallout sediments is a reliable index of distance from the crater, fine grain sediments do not, however, necessarily indicate distance from the crater mouth.