The maximum feature of the Holocene clay deposited in the eastern Osaka area is that the sensitivity is very high. In this paper, firstly the geotechnical characteristics and the regional differences of this clay are discussed by using “Kansai Geotechnical Information Database” and standard borings having detailed soil testing data due to continuous undisturbed samples. This sensitive clay is distributed in the former river channel, and it has been understood to adjust well with the distribution region of N-value (SPT) ≒ 0. Next, the cause of sensitivity is reconsidered from the aspect of the depositional environment. The formation of sensitive clay is thought to be due to not only leaching of the salinity but also low activity of benthos. So, these are thought to be caused by the depositional environment under the brackish water located the closed-off section of bay.
