Within the regular effects of climatic forcing (e.g., Asian monsoon evolution, typhoons, and extreme climate/weather) and tectonic origin (e.g., intense seismicity and marine landslides) in the western Pacific and East Asian continent, Taiwan is an ideal location that provides excellent material to investigate significant scientific topics across different timescales. By participating in the International Marine Past Global Change Study (IMAGES) program, Taiwanese scientists have successfully used the great capabilities of long coring systems, such as that on the French Research Vessel Marion Dufresne, in the last two decades to collect very long cores (> 40 m) in many important locations in the seas around Taiwan and the western Pacific (e.g., IMAGES III/MD106-IPHIS cruise, WEPAMA cruise, PECTEN cruise; Chen et al., 1998; Bassinot et al., 2002; Beaufort et al., 2005). These high-quality long cores have been used in paleoceanographic reconstructions, with particular focus on tropical climate mechanisms and their teleconnections with high-latitude climates (e.g., WEPAMA/PECTEN cruises; Bassinot et al., 2002; Beaufort et al., 2005). These significant findings of late Quaternary low-latitude Pacific paleoceanography have advanced our understanding of how tropical oceans have been coupled with or isolated from the Northern Hemisphere high-latitude climate and how the tropics have played a role in modulating the global climate (e.g., Chen et al., 2010; Yu et al., 2017). These findings have also provided scientific background for predicting natural changes in future climates (e.g., IPCC AR6; IPCC, 2021).
However, little is known about the past extreme events and likely characteristics around Taiwan that were caused by earthquakes, typhoons, and climate forcings. Knowing the history of past extreme events may be critical to our understanding of their evolution and possible driving forces in comparison to natural climate mechanisms. In 2018, the Taiwan-French international team further investigated the issue of past extreme events during the R/V Marion Dufresne Extreme events Archived in marine GEological Records off Taiwan (EAGER) cruise. In addition, this successful EAGER cruise also reached key milestones for clean energy exploration. The trapping of frozen methane hydrate “known as flammable ice” in the core catcher of the Calypso corer was witnessed during the cruise. The first hand-sized hydrate was discovered in the vicinity of the South Yuan-an East Ridge. Such direct and solid evidence further confirms that offshore SW Taiwan contains one of the largest potentially producible accumulations of gas hydrates (e.g., Huang et al., 2021).
For marine geological and geophysical investigations around Taiwan, the development of high-quality long coring on research vessels is necessary. In 2017, the 2800-ton R/V Legend of the Taiwan Ocean Research Institute (TORI) was equipped with a giant CALYPSO coring system (i.e., piston corer) and deep-sea winch system, which is similar to the R/V Marion Dufresne coring facilities. However, it is unknown whether the deployment of a giant coring system on the R/V Legend affected the quality of marine sediments. The LGD-T32 and LGD-T43 cruises of the R/V Legend were designed to test the capability of the giant coring system offshore SW Taiwan. A region with a higher known sedimentation rate (> 0.9 g/cm2/year; Huh et al., 2009) on the Kaoping slope was further investigated by deploying giant piston and gravity corers (Table 1, Fig. 1). In this study, we analyze and combine non-destructive data (e.g., physical properties and visible color reflectance) in conjunction with digital core images. Non-destructive records not only provide a basis for stratigraphic correlation but also give a better opportunity to understand sedimentary structures and examine core quality of the recovered sediment. Moreover, the characteristics of sedimentary structures are directly determined by the qualitative method of visual core description and the lithology of the core. Few quantitative methods have offered plausible ways to define the exact magnitude of the distorted sedimentary structures in imperfect sedimentary records in the context of overly limited sedimentary records. In addition, diffuse reflectance spectroscopy for capturing color reflectance data from core surfaces can be used as a tool for stratigraphic correlation and further infer the possible biogenic content/mineral compositions of sediments (e.g., Ortiz et al., 1990; Pan et al., 2015).
The novel, non-destructive technique is a quick and cost-effective procedure for sediment core analysis that requires nonchemical analysis with complicated procedures. It is commonly established in onboard and offshore laboratories and used to acquire high-resolution information on sediment compositions. Four giant sediment cores at the coring site of 22°23’N, 120°13’E were therefore used to provide the basis for comparison with non-destructive measurements. This study mainly focused on (1) documenting high-resolution, non-destructive analyses on giant piston and gravity cores from offshore SW Taiwan; (2) investigating the quality of core materials via non-destructive core measurements and the quantitative curvature index (CI) method; and (3) exploring stratigraphic correlations and assessing possible mechanisms, as supported by the integrated data.