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Research for sea-level changes on marine Middle to Late Pleistocene deposits in Japan and New Zealand

日本和新西兰海洋中晚更新世沉积物海平面变化研究

基本信息

批准号：
10640443
负责人：
KIKUCHI Takao
金额：
$ 0.32万
依托单位：
Tokyo Metropolitan University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

项目摘要

The Kazusa and the Shimousa Groups in the Boso Peninsula are stratotypes of Japanese marine Pleistocene deposits. The Shimousa Group comprises several cyclothems controlled by glacial eustasy. One of conclusions of this study is that the basal formation of the Group is the Nagahama Formation composed of gravel bed overlying the Ichijuku Formation, which belongs to the Kazusa Group with clear boundary named the Nagahama Unconformity. Recent studies had cleared that the unconformity was formed at marine isotope stage 16.An obvious geological succession of marine Pleistocene in Wanganui Basin, New Zealand, have been researched by many workers and the correlation for marine stratigraphy and terraces had been proposed by Pillans(1990). A question arose, however, about the correlation by my field survey at 1993. I found some thin black colored tuff layers interbedded Upper Westmere Siltstone at the coast and the Marorau terrace deposits at the hilly district, and there is a great possibility that they are the same layers.If my observation is correct, Pillans's correlation between the succession at Castlecliff coast and the flight of terraces will be obliged to revise. As the Ararata terrace is fixed stratigraphically with Rangitawa Pumice, some terraces higher than the Rangitatau terrace must be shifted their stratigraphic horizons to older stages, respectively. One of the merits of new version is dissolution of a contradiction, which the Rangitatau terrace was formed during marine isotope stage 12, namely, low sea-level stage. Moreover, if the Ball terrace corresponds to isotope stage 15, inferred obvious low sea-level at just before the terrace corresponds to stage 16 which is said as extreme low sea-level. The basal surface of the Nagahama formation of the Boso is correlated to the one of the Sea field Sand of the Wanganui district by remarkable lowstand of sea-level.

房总半岛上的Kazusa群和Shimousa群是日本海相更新世沉积的层型。Shimousa群由几个受冰川侵蚀控制的旋回层组成。本研究的结论之一是，该群的基底地层是由砾石层组成的长滨组覆盖在一宿组之上，属于Kazusa群，边界清晰，称为长滨不整合。新西兰Wanganui盆地的海相更新世具有明显的地质序列，Pillans（1990）提出了海相地层与阶地的对比。然而，我在1993年的实地调查中提出了一个关于这种相关性的问题。我发现一些薄的黑色凝灰岩层夹在海岸的上韦斯特米尔粉砂岩和丘陵地区的Marorau阶地沉积物之间，它们很有可能是同一层。如果我的观察是正确的，Pillans在Castlecliff海岸的继承和阶地的飞行之间的相关性将不得不被修正。由于Ararata阶地在地层上与Rangitawa浮石固定在一起，一些高于Rangitatau阶地的阶地必须分别将其地层层位转移到更老的阶段。新版本的优点之一是解决了朗伊塔套阶地形成于海洋同位素第12阶段即低海平面阶段的矛盾。如果Ball阶地对应于同位素第15阶段，则推断阶地前的明显低海平面对应于第16阶段，即极低海平面。房总的长滨组的底面与旺加努伊地区的海场砂的底面具有明显的海平面低位。