Paleoenvironment analysis of northern Ilan Plain

• Main Authors: Fanny Wang, 汪月霞
• Other Authors: Eason Hong
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/11943489604366477860

碩士 === 國立臺灣海洋大學 === 應用地球科學研究所 === 97 === There are many scholar of the opinion that Ilan plain was subsiding by extension of Okinawa trough that at east-north and its still subsiding now. There are two kinds of subsidence, one is north-south symmetrical graben, the other one is subsidiary southward half-graben. In interpreting the paleoenvironment ofIlan plain, we used analysis of lithofacies of the core sediments, the fossil and age dating to understand the relation between stress of land and subsidence of Ilan plain. Based on the lithology, eight lithofacies are recognized and further ascribed into ten facies associations: gravel braided stream, gravel-send braided stream, send braided stream, meandering stream, estuarine, backshore, forshore, upper shoreface, lower shoreface, and offshore. Based on the environment which were recognized, seven sequential stages of the depositional environments have been reconstructed. In the first three stages observed there are subduction at the northern Ilan plain and the shape of Ilan plain were higher at the southern, lower at the northern Ilan plain. This is correspond the saying that half-graben only subsiding at northern. The four-six stages were still ingression, noly have a high rate of diposition at stage5. Couse the range of sea level climbing was short, last stage keep diposition, make the landgorms today.