碩士 / 國立中央大學 / 地球科學學系 / 106 / The offshore area of southern Taiwan is the Manila subduction system prone for large earthquakes. Earthquake-triggered submarine landslides and ensuing turbidity currents are likely to deposit mass transport deposits and turbidites in the intra-slope basins across the accretionary wedge. Studying turbidites may therefore determine the timings and recurrence intervals for subduction zone large earthquakes. Seven cores from the perched Kenting Basin in the upper accretionary wedge as well as the intra-slope basins in the overbanking area of the lower Gaoping Canyon are used to characterize sedimentary facies by using physical and chemical properties of sediments. Carbon 14 dating is performed on forams to constrain sediment ages.
The isolated and closed Kenting Basin is free from Taiwan sediment inputs and the most likely source of turbidity currents are submarine landslides presumably triggered by earthquakes. The turbidites are rich in sands and reworked forams, showing typical Bouma sequence. Our analysis shows that there are six episodes of turbidite layers in the Kenting Basin for the last 10,000 years. Some episodes are characterized by two closely spaced turbidite layers. This indicates that the turbidite recurrence interval is around 1,500-2,000 years and some events are characterized by two consecutive turbidity currents separated by a few to tens of years. The most recent event in the Kenting Basin is around 400 years ago, probably corresponding the historical 1781 tsunami event in SW Taiwan.
However, in the overbanking area and close to the river-connected Gaoping Canyon, the event beds are, at least, doubled in number. Turbidity currents in this area can be driven by earthquake-triggered submarine landslides as well as climate-driven density flows, such as hyperpycnal turbidity currents related to onshore floods in the Gaoping River. We suggest that a lot more turbidites in this area are due largely to hyperpycnal flows as evidenced from reported recent hyperpycnal events along the Gaoping Canyon.
| Identifer | oai:union.ndltd.org:TW/106NCU05134004 |
| Date | January 2018 |
| Creators | Yi-Chen Chen, 陳奕辰 |
| Contributors | 林殿順 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 84 |
Page generated in 0.0088 seconds