新潟県米山地域における新第三系

概要

論文の詳細を見る
The stratigraphical and the volcanological, studies around Yoneyama district, Niigata prefecture, were carried out. A large amount of volcanic materials characterizing the Neogene system in this district were produced by the intensive marine volcanism occured in the Nishiyama stage, early Pliocene. The symptom of this volcanism, however, can already be recognized in the Teradomari stage, late Miocene, and it continued untill the Uonuma stage, Pliocene to Pleistocene. It is deduced that the volcanism along many fractures with the NNE-SSW direction broke out in the subsiding stage after the folding and the folding and the upheaval from the facts that the structure of pyroclastic rocks is discordant with that of the lower formations, many intrusive bodies and the thickest parts of the pyroclasticformations are on the same line with the NNWSSE direction along the south-eastern margin of Mt. Yoneyama, and the pyroclastic rocks show neritic sedimentary facies. The basement of the Neogene system in this region may belong to the Joetsu metamorphic belt, because diorite granite, metamorphic rocks and ultra-basic rocks were found as gravels in the conglomerate beds and as xenolith in the andesite lava flows of the Neogene system.
1973-01-25