Textural Analyses of the Gravels in the Linkou Tableland
Date Issued
2014
Date
2014
Author(s)
Chang, Sung-Ping
Abstract
The gravels in the Linkou Tableland, distributes over Pliestocene Linkou Formation and Tanawan Formation. According to facies analysis, the depositional environments of the gravels are considered mostly braided river and a small part of the beach. However, previous texture studies lack comparison with different facies changes and strict measurement methods. Therefore, this study measured textures again to recognize changes for each facies and calculate paleohydrology.
This study measures the grain size, imbrication, particle form and roundness. Grain size measures the 5 largest visible clasts for calculating paleohydrology. Imbrication, shape and roundness especially rule the sampling area, number and range of grain size. The results are separated from five facies to get the mean and standard deviation, including apex, upper fan-delta, middle fan-delta, lower fan-delta and beach.
The paleohydrology distribution represents several continued main channels.
% at upstream, and main channels branch into few smaller channels whose shape are like fans.
With increasing transport distance, grain size decreases, sorting becomes better, and imbrication becomes more uniform. Roundness is better at upstream and no significant change at downstream. Compared with river, beach roundness is better and imbrication is more scattered.
%The particle form is without significant change in each facies.
The main channels of Linkou fan-delta presents a fixed location. This characteristics is similar to other alluvial fans. From the apex to the lower fan-delta, the flow competence and depositional rate decreases, and abrasion is concentrated in the upstream region. According to alluvial autogenic cycle, upstream region deposits channels and post-fill deposits, making the size and sorting has larger variability in upstream. Imbrication is influenced by flow competence and depositional rate, and gravel beach can observe a significant difference between braided river in roundness and imbrication.
Subjects
林口臺地
礫石
組構
扇洲
Type
thesis
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