Title of Project:

Integration of offshore investigation and mapping data in Taiwan- Basic investigation and mapping of Taiwan offshore area in 2018

Duration：

May 3, 2018～March 2, 2019

Name of Principal Investigator：

Char-Shine Liu (Researcher and Chief Executive Officer, Ocean Center, National Taiwan University)

Abtract of Project：

1. 
   I. Objectives This project aims to investigate the sedimentary and crustal structures (Fig 1 to Fig 3), extreme events (Fig 4), freshwater resource on Taiping Island, and the ecological environment in the Nansha (Spratly Islands) area. II. Execution of the project A 12-day cruise using the R/V Ocean Research I was used to collect the multi-channel seismic data in the Nansha area (Figs. 1 to 3). During the cruise, we have also collect magnetic data, bathymetry data and ocean current data along the seismic lines at the same time. In addition, two gravity cores have been collected at the selected sites during the cruise. By analyzing those data, we can identify the sedimentary structures, estimate the seismic wave velocities of the strata, the thickness of the sediments, and the position of the foot of the continental slope. Gradually we can establish the basic information of the territorial of sea area, and maintain the rights and interests of the territorial of sea area of our country. From core sample analyses, we can obtain the deposition history of the Nansha area and identify the extreme events and establish their records. III. Project Results We have observed different structural features from reflection seismic profiles (Fig. 5) and distinguished the continental crust, transition zone, and oceanic crust domains, respectively, which help us to understand the process of continental rifting. The analysis results of core data (Fig. 6) show that the sediments are easily transported and accumulated in the channels under seabed by seafloor collapse and gravity flow when typhoons come. It may cause the calcium content in the event layer more than that in the non-event layer, and terrestrial sediments may be transmitted to the deep sea by extreme events such as typhoon.

    

   Outcomes and Milestones:

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   Fig 1: Map showing the distribution of reflection seismic profiles and core stations conducted in the Nansha area, including the data collected by this project in the previous years (2014 to 2018).

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   Fig 2: Map showing the project investigations area and the distribution of seismic profile data and core data collected in 2018. The total length of the seismic data collected is 228 miles, and there are two gravity core stations.

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7. Fig 3: Photos showing shipboard operations in and around Nansha (Spratly Islands) area.

    

   Fig 4: Collecting the fresh water samples on the Taiping Island and marine gravity coring operation.

   

   Fig 5: MCS1159-8 Reflection seismic profile result. （We can distinguish 3 domains, namely the continental crust, the transition zone, and the oceanic crust as revealed from their distinctive structural and seismic features.）

   

   Fig 6: OR1-1189-C1 diagram of the core surface image and core scan results, including Itrax, sorting, Pb²¹⁰activity, P wave velocity, bulk density, magnetic susceptibility and resistivity variations along the core samples.