博士 / 國立臺灣大學 / 海洋研究所 / 85 / Surface sediments from five box cores and forty-six gravity
cores in continental shelf and slope off southwestern
Taiwan were examined. Analyses of radiography, grain-size,
physical properties, and organic carbon as well as carbonates
contents of these sediments were performed to recognize the
sedimentary environments of the study area.
Four depositional subenvironments and six types of sedimentary
structures off southwestern Taiwan have been identified: (a)
terrigenous clastic shelf deposits with shelly sands; massive
structure, (b) terrigenous clastic estuary deposits off Kaoping
River; laminated structure, (c) mudstone brecciaed mudstone
deposits resulting from the eruption of mud volcanos; breccia
scattering structure, (d) turbidite sequence structure.
Turbidite deposits can be subdivided into two structures: pyrite
vein facies and non-pyrite vein facies. Bioturbation is commonly
found in core sediments from Kaoping slope and formed
bioturbated structure. In general, the
sedimentary environments of the continental shelf and slope off
southwestern Taiwan were controlled by tectonics. The plate
subduction and compression between Eurasian and Philippine Sea
plates contribute the formation and development of mud diapirs,
and make the rugged slope surface incised by many canyons and
gullies. In the subenvironment characterized by mudstone
brecciaed mudstone, mud diapirism contributes a large scale mud
volcano activity, but, some single mud volcano have also been
found in other subenvironments. Some mud breccia was interbeded
with turbidites suggesting intermittent eruptionof mud
volcanoes. On the basis of grain-size analysis, Shou-Shan Gully
and Kaoping Canyon were found to be the main passages of the
slope sediment transportation. Although the Kaohsiung Canyon is
deeper and much extensive than the Shou-Shan Gully, Kaohsiung
Canyon does not play the role for slope sediment transportation.
Abundant terrigenous clastic matierals continuously pour into
the shelf and slope area by river propagation and longshore
erosion. Tidal current and offshore current are the main
mechanism of shelf sediment transportation, while turbidity
current is that prevalent on the slope. Abundant fine-grained
sediments within the turbidity currents were attached by
organic carbon and were deposited on the slope, offering foods
for benthos. It is probably the reason that bioturbations can
be commonly found within the sediments in a reducing setting,
and even the pyrite vein can be formed in the surfacial
sediment. In Kaoping Slope, turbidity currents may occurr in
high frequency. Incomplete sequences of turbidites may be due to
overlapping turbidity events. Near the sides and at the end of
turbidites, hemiturbidite structure associated with abundant
trace fossils and pyrite veins can be found. Five types of
pyrite vein can be distinguished in the study area. Most of them
are trace fossil tracks and tubes filled with pyrite.
Obviously the diversity of trace fossilwas constrained by
sedimentary accumulation rate and the organic carbon content.Ten
species of trace fossils can be found from the sediments on
Kaoping Slope, where the pyrite vein (or hemiturbidite)
subenvironment has the highest diversity, turbidite
subenvironment the second, and estuary area the least.
Bioturbation is rarely found in the sediments on the shelf.
| Identifer | oai:union.ndltd.org:TW/085NTU00274005 |
| Date | January 1997 |
| Creators | Chern, Yi-Ching, 陳儀清 |
| Contributors | Chen Men-Pen, Tian Wen-Min, Fan Zheng-Cheng, Wang Joa-joa, Shiu Shea-jie, Wen Jeng-hwa, Ling Yu-Sung, 陳民本, 俞何興, 劉家瑄, 陳琪芳, 周瑞燉, 鄭偉力, 謝昭輝 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 180 |
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