The Clay Minerals of Mudstones in the Plio-Pleistocene Formations of Coastal Range, Eastern Taiwan and Their Implications
Date Issued
2008
Date
2008
Author(s)
Ting, I
Abstract
Illite crystallinity is usually a good indicator to define low grade metamorphic zone for pelitic rocks. In previous studies, the sedimentary rocks in the Madagida-chi and Hsiukuluan-chi sequences of the Coastal Range, eastern Taiwan showed increasing the illite crystallinity from the bottom to the top. It was interpreted to record progressive unroofing of the nearby prograde metamorphic terrane during arc-continent collision. In this study, we collected and analyzed clay mineralogy and illite crystallinity of mudstones from several sequences in the northern and middle sedimentary basins of Coastal Range, and also combined the data having published in southern one. The aims are to understand the spatial and temperal variations of illite crystallinity which recorded the unroofing history of source area, the Central Range of Taiwan.. The results show that the younger formation age was, the better illite crystallinity was in all sedimentary basins of the coastal Range, eastern Taiwan. The anchizone illite crystallinity of sediments suggests that the slate belt of Central Range has been exposed to the surface for erosion. However, the abrupt increase of slate ratio in sandy components is to infer that the slate belt have been uplifted and eroded quickly. From the beginning of slate exposed to the erosion peak, it has time lag in general. The result from illite crystallinity and prtrography in each sections of the Coastal Range showed that the time lag was approximately to 0.5-1.0Ma.he deposited timeof coarse and fine particles in the northern part of Coastal Range, east Taiwan seems to more consistent than southern one due to the oblique arc-continent collision which the coarse and fine sediments eroded and deposited in the forearc basin of the north almost simultaneously.. However, there was a time lag for the fine and coarseparticles which the former eroded and deposited in forearc basin of southern one was earlier than the latter during the early stage of collision, Furthermore, the coarse particles abruptly increased when the slate terrane uplift to the peak. . e also compiled the data from the Western Foothills and found that the illite crystallinity increasing upward were not significant comparing with the Coastal Range, eastern Taiwan. This result suggests that it may due to the complicated foreland basin tectonic processes in the Western Foothills of Taiwan.
Subjects
the Coastal Range
illite crystallinity
clay minerals
Type
thesis
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