本論では，房総半島南東岸の温石川の川岸に露出する約8,400～7,700 cal BPにかけて堆積した溺れ谷堆積物の特徴と，そこに見られる地震隆起や津波の痕跡について報告する．この露頭は最大高5 m程度で，泥層・砂層・砂礫層の互層からなる．堆積相解析，貝化石と有孔虫化石の分析，AMSによる14C年代測定値をもとに堆積環境の変遷を復元した結果，8,200 cal BP頃に相対的海水準の一時的な低下が認められた．この現象は，地殻変動の少ない東京湾沿岸では，後氷期に7,000 cal BP頃のピークへ向けて相対的海水準が継続的に上昇したことと矛盾し，調査地域での地震隆起を示していると考えられる．泥層に挟まる砂層や砂礫層は，溺れ谷に流入した高潮や洪水，あるいは津波による堆積物と考えられる．とくに8,200 cal BP頃の相対的海水準が低下する直前に堆積した砂礫層は，海岸の隆起を起こした地震に伴う津波堆積物である可能性が高い．
The fluvial supply and littoral dispersal of sediment exert profound influences on the way in which sandy beaches evolve. This paper looks at the importance of flood events in assessing the sediment budget in a littoral cell,with consideration of the grain-size dependency of sediment dispersal. The particular discussion focuses on the impact of a major flood that occurred at the end of July 2011 and brought a significant amount of sediment offshore through the mouth of a river(Okotsu diversion channel). The retrieval and facies analysis of three offshore sediment cores permitted the authors to identify the 2011 flood-event layer on top of each sediment core. The gamma-ray spectrometry revealed that the flood-event layer carried the March 2011 Fukushima-event-associated radioactive nuclides.
The varved sediment profile of Lake Suigetsu, central Japan, offers an ideal opportunity from which to derive a terrestrial record of atmospheric radiocarbon across the entire range of the 14 C dating method. Previous work by Kitagawa and van der Plicht (1998a,b, 2000) provided such a data set; however, problems with the varve-based age scale of their SG93 sediment core precluded the use of this data set for 14 C calibration purposes. Lake Suigetsu was re-cored in summer 2006, with the retrieval of overlapping sediment cores from 4 parallel boreholes enabling complete recovery of the sediment profile for the present “Suigetsu Varves 2006” project (Nakagawa et al. 2012). Over 550 14 C determinations have been obtained from terrestrial plant macrofossils picked from the latter SG06 composite sediment core, which, coupled with the core's independent varve chronology, provides the only non-reservoir-corrected 14 C calibration data set across the 14 C dating range. Here, physical matching of archive U-channel sediment from SG93 to the continuous SG06 sediment profile is presented. We show the excellent agreement between the respective projects' 14 C data sets, allowing the integration of 243 14 C determinations from the original SG93 project into a composite Lake Suigetsu 14 C calibration data set comprising 808 individual 14 C determinations, spanning the last 52,800 cal yr.
