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A dynamical study of marine terrace formation

海洋阶地形成的动力学研究

基本信息

批准号：
61580210
负责人：
SUNAMURA Tsuguo
金额：
$ 1.28万
依托单位：
University of Tsukuba
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1986
资助国家：
日本
起止时间：
1986 至 1987
项目状态：
已结题

项目摘要

(1) In order to examine what kind of landforms is created when waves are allowed to act on a gently sloping rock surface emerged as a result of uplift of the land, a laboratory test was performed using a model rocky coast with a uniform slope of 1/10. The model was made using a mixture of cement, sand, and water. The result showed that an abrasion terrace with a similar gradient to the original slope was formed in the surf zone and the shoreline angle was located slightly higher above Still Water Level.(2) A mathematical model was constructed to describe the formation of Holocence marine rockterraces. The terrace width, W , is expressed byWi= [ Zi (B + Ri <tau>i + <lambda>i )/ h_b ] -R_<i+1> <tau>_<i+1> ( i = 1,2,・・・n) where Z is the amount of sea level fall, R is the recession rate of coastal cliffs, <tau> is the time for sea level stillstand, R<tau> is the recession distance of the cliffs, <lambda> is the horizontal distance from the intersecting point of sea level and the original landform profile to the initial coastline position, B is the width of abrasion terrace on the original landform, h_b is the maximum water depth for submarine abrasion, and the suffixes i-l, i, and i+l denote the sea levels i-l, i, and i+l, respectively.(3) Seven coastal terraces well develop near Pukemuri Stream, Wairarapa, New Zealad, where the ages of three terraces (II, III, and IV ) out of seven are unknown. The above model was applied to this site to estimate the ages of these terraces. The result showed that the ages of II-, III-, and IV-terraces were estimated at 6,000, 5,300, and 4,300 y B.P., respectively.In this estimation, the age values for V-and VI-terraces were used for reference values. The estimated I-terrace age was 7,000 y B.P.which is colse to ^<14>C-value of I-terrace,about 6,700 y B.P. This suggests that model is reasonable.

(1)为了研究当波浪作用于因陆地隆起而出现的缓坡岩石表面时会产生什么样的地貌，使用坡度为1/10的岩石海岸模型进行了实验室试验。这个模型是用水泥、沙子和水的混合物做的。结果表明，碎波带内形成了坡度与原坡相似的冲刷阶地，岸线角略高于静水面。(2)建立了全新世海相岩阶形成的数学模型。阶地宽度W表示为Wi = [ Zi（B + Ri <tau>i + <lambda>i）/ h_b ] -R_i+1><tau>_i+1>（i = 1，2，···n）式中Z为海平面下降量，R为海岸峭壁后退速率，R为<tau>海平面停滞时间，R<tau>为峭壁后退距离，<lambda>为海平面与原始地貌剖面交点到原始海岸线位置的水平距离，B为原始地貌上的剥蚀阶地宽度，h_b为海底剥蚀的最大水深，后缀i-l、i和i +l分别表示海平面i-l、i和i+l。(3)新西兰Wairarapa的Pukemuri溪附近有七个海岸阶地，其中七个阶地中有三个阶地（II、III和IV）的年龄未知。上述模型被应用于该站点，以估计这些阶地的年龄。结果表明，II阶地、III阶地和IV阶地的年龄分别估计为6，000年、5，300年和4，300年B. P.，在这一估计中，V阶和VI阶的年龄值被用作参考值。Ⅰ阶地的年龄估计值为7,000 yB. P.，与<14>Ⅰ阶地的δ C值（6,700 yB. P.）接近，表明该模型是合理的。