Study on Quaternary Geological Characteristics of Echigo Plain

对越后平原第四纪地层进行了研究，并与周边地区进行了对比。特别是对平原的地下地层进行了地层分析。建立了新的地层划分和地质时代。它们依次为西山组、海泉组、未命名的中更新世、关原组、隐伏阶地沉积、西关原组、Shirone组和黑鸟组。其次，对第四纪沉积环境历史与相对海平面变化进行了初步研究。上新世晚期以后，海岸线逐渐向北移动。越后平原自中更新世晚期开始，形成了以滨海平原-三角洲体系沉积为主的沉积遗址。全新世时，越后平原在海平面上升的条件下形成了沙丘。本文特别研究了日本海中东部地区第四纪海平面变化的历史，并考察了其地质特征。1)越后平原第四纪沉积盆地自中新世中期起即为盆地的一部分。沉积厚度超过3500米的第四纪海相和陆相沉积物是非常典型的。早中新世以来，沉积盆地一直延续。2)第四纪盆地在中更新世中期划分为隆起带和沉降带。地层由浅海和河流沉积组成，有多种动植物化石。鄂后平原周围第四纪详细记录了晚新生代海平面的反复变化。3)盆地为隆起的山地丘陵所包围，是一个大型沉降区，东西两侧断裂带发育。地下水中所含的水溶性气体和碘是非常有用的燃料和物质资源。它们是由海湾三角洲砂质河系沉积物组成的地层中提取的，但地面沉降是由地下水抽水引起的。少

The stratigraphy of Quaternary deposits of the Echigo Plain was examined and correlated with that of the surrounding areas. Especially, the subsurface strata in the plain were made clear stratigraphically. The new stratigraphical division and the geologic age of them were established. They are divided into the Nishiyama Formation, the Haizume Formatin, the unnamed Middle Pleistocene, the Kanbara Group, Buried terrace deposits, the Nishikanbara Formation, the Shirone Formation, and the Kurotori Formation in ascending order. Nest, the preliminary study on the history of Quaternary sedimentary environment was carried out in relation to relative sea-level change. After the latest Pliocene, the coastal line was moved northward step by step. In Echigo Plain, depositional sites composed of coastal plain-delta system deposits spread out since late Middle Pleistocene age. At Holocene age, the Echigo Plain was formed with sand dunes under rising sea level. Especially, in this study the history o … More f Quaternary sea level changes in the east-central area of the Sea of Japan, and the geological characteristics were examined as followings.1) The Quaternary sedimentary basin of the Echigo Plain was a part of the basin since middle Miocene age. It is very characteristic to deposit Quaternary marine and terrestrial sediments more than 3,500m in thickness. The depositional basin has continued since Early Miocene time. 2) The Quaternary basin was divided into uplift and subsiding areas at middle Middle Pleistocene age. The strata consist of shallow marine and fluvial deposits with many kinds of animal and plant fossils. The repeated sea level changes during Late Cenozoic were in detail recorded on the Quaternary around the Echigo Plain. 3) The basin surrounded by rising mountains and hills is a large-scaled subsiding area with growing fault zones in east and west sides. 4) Water-soluble gas and iodine included in groundwater are very useful for fuel and material resources. They are extracted from strata which are composed of bay-delta-gravelly river system deposits, but the land subsidence was caused by pomping groundwater. Less