Eustatic, sedimentary supply, tectonic controls on sequence stratigraphy of Paleo-Tokyo Bay

下摩沙群的上泉组、清川组和横田组发育于中更新世古东京湾（约250 ~ 150kabp），生长于下摩沙高地。在这些地层中发现了滨浅海相沉积体系（河流、河口、三角洲、潮汐沙坝、滨滩、潮汐入口和泻湖湾），构成了两个沉积层序。这些序列发育于氧同位素曲线的第8 ~ 6阶段，主要受冰川—海平面上升的控制。从以火山灰层为标志的年代地层表面的测绘推断，沉积体系的空间变化在地层的沉积序列中是可识别的。古东京湾在冰期低海平面阶段被河流切割成河谷。陆上不整合面为层序边界。间冰期相对海平面的高水位阶段形成了两种不同类型的沉积体系：河口三角洲和潮汐沙洲体系和河口堰洲岛体系。这种空间差异可以用古东京湾地区沉积供给和构造运动的差异来解释。因此，上泉组、清川组和横田组发育了高沉降-高输沙通量型层序和低沉降-低输沙通量型层序。

The Kamiizumi, Kiyokawa and Yokota Formations, Shimosa Group, which crop in the Shimosa Upland, were deposited in the middle Pleistocene Paleo-Tokyo Bay (c.250 - 150 KaBP). Paralic and shallow marine depositional systems (fluvial, estuarine, delta, tidal sand bars, shoreface-beach, tidal inlet and lagoon-bay) are recognezed in the formations and constitute two depositional sequences. These sequences are interpreted to have developed during the stage 8 - 6 of the oxygenisotope curve and been primarily controlled by glacio-eustatic sea level changes. Spatial variation in depositional systems, inferred from the mapping of a chronostratigraphical surface marked by some volcanic ash layrs, are recognizable in the depositional sequences of the formations. In Paleo-Tokyo Bay, valleys were incised by rivers during the low sea-level stage in the glacial period. The subaerial unconformity shows a sequence boundary. Two different types of depositional systems were formed during early transgressive through highstand stages of the relative sea level in the interglacial period : estuarine-delta and tidal sand bars systems, and estuarine - barrier island systems. The spatial variation is interpreted in terms of differences in sedimentation supply and tectonic movement in Paleo-Tokyo Bay area. Consequently, two types of depositional sequence developed in the Kamiizumi, Kiyokawa and Yokota Formations : a high subsidence-high sediment flux type of sequence and a low subsidence-low sediment flux type of sequence.