A dynamical study of marine terrace formation

(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&lt；tau&gt；i+&lt；lambda&gt；i)/h_b]-R_&lt；i+1&gt；&lt；tau&gt；_&lt；i+1&gt；(i=1，2，···n)where Z is the amount of sea level fall，R is the recession rate of coastal cliffs，&lt；tau&gt；is the time for sea level stillstand，R&lt；tau&gt；is the recession distance of the cliffs，&lt；tau&gt；is the recession distance of the cliffs；Lambda&gt；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。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，and4，300y 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 7，000y B.P.which is colse to^&lt；14&gt；C-value of I-terrace，about6，700y B.P.This suggests that model is reasonable。

(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.