Depositional Characteristics of Volcanic Debris of Datong Volcano Groups in the Eastern Part of China
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摘要: 本文对大同火山群火成碎屑沉积物的空中坠落沉积和碎屑流动沉积（陆上和水中）的横向变化和垂向变化及组合进行了探讨性研究，进而发现空中坠落沉积物在垂向上具有成层性，横向上沉积物的粒度和厚度随远离火山口的距离呈有规律的减小，但流动沉积物中浮岩粒级是颠倒的，细粒沉积物一般在距火山口很远处形成，但也有在火山口附近沉积的，这与火山喷发强弱有关，可见粗粒的坠落沉积物是近火山口的可靠指标，但细粒沉积物并不一定表示远离火山口。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.
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Key words:
- PyToclastic debris /
- Pumice /
- Grain size grade /
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