A Study on the Origin of the Hengchun Plateau of the Upper Accretionary Wedge off Southern Taiwan (III)

Project Details

Description

The tectonic uplift of the upper accretionary wedge offshore the Hengchun Peninsula is mainly governed by splay faulting, structural underplating, and back-thrusting in the rear wedge. Around 50 km offshore the peninsula, the upper accretionary wedge becomes a wide and shallow submarine plateau. This large submarine plateau lies around 400-700 m in water depths and 2,000 km2 in area, which is named the “Hengchun Plateau” in this study. One of the scientific objectives for this proposal is to understand the nature and origin of the Hengchun Plateau and its tectonic implications. This proposal is the third year project-proposal. Rocks recovered from the plateau surface, lying at 400-700 m water depths, during the OR1-1138 cruise, show high P-wave velocity, indicating that these well-lithified rocks were buried, at least, 2-4 km in depths. We also found a flat-topped pinnacle located in the southeast corner of the Hengchun Plateau. This flat-topped pinnacle is underlain by well-lithified sedimentary rocks of 70 m water depth, covering around 30 km2 in area and is informally coined “Kuroshio Knoll” in this proposal. This wide and shallow flat surface lies in the path of the strong Kuroshio Current and it may serve as good candidate site for renewable energy powered by the Kuroshio Current in the future. This project proposes to acquire multi-beam bathymetric data and to collect rock samples by using dredge coring in and around the Hengchun Plateau during the third project year (8/2018~7/2019). The detail bathymetry will shed lights on the geological and erosional processes operating on the plateau and the rock samples are to study their compositions, sources of zircon grains and possibly geological ages.There are a few sediment cores containing seismo-turbidites being retrieved from perched basins neighboring the Hengchun Plateau as well as in the hanging wall and footwall of the splay fault. The French research vessel Marion Dufresne (MD) is scheduled to acquire giant piston cores in the Taiwanese waters in June 2018 for studying extreme events and paleoseismology. One of the scientific objectives for this proposal is to use these MD cores to study the timing and recurrence interval for subduction zone great earthquakes and extreme events in the Manila subduction zone. The MD cores recovered from the perched basins around the Hengchun Plateau will be studied to characterize the temporal variations of the Kuroshio-Current flow strength over the plateau surface.The scientific objectives for this study are: (1) to understand the nature and origin of the submarine Hengchun Plateau and the mechanism that drives the uplift of the upper accretionary wedge in the study area; (2) sedimentation rates and sediment provenances for the perched basins and the Luzon forearc basin in and around the Hengchun Plateau; (3) reconstructing the past current speeds of the Kuroshio Current through analyzing the grain-size variations of sortable silts through time recovered from perched basins neighboring the Hengchun Plateau; and (4) timing and return periods for extreme events and great earthquakes in the Manila subduction zone.
StatusFinished
Effective start/end date1/08/1831/07/19

UN Sustainable Development Goals

In 2015, UN member states agreed to 17 global Sustainable Development Goals (SDGs) to end poverty, protect the planet and ensure prosperity for all. This project contributes towards the following SDG(s):

  • SDG 11 - Sustainable Cities and Communities
  • SDG 14 - Life Below Water
  • SDG 17 - Partnerships for the Goals

Keywords

  • Southern offshore Taiwan
  • Manila subduction zone
  • Hengchun Plateau
  • paleoseismology
  • seismoturbidites

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