An integrated, non-destructive method for evaluating core quality from R/V Legend’s giant piston coring system

The quality of marine sediment cores is significant for investigations on marine geohazards, paleoceanography, paleoclimatology, and marine environmental changes. The identification of genuine or artificial sedimentary structures is essential to the development of long piston coring procedures. In this study, we highlight an overlooked primary process of a standard procedure and its effect on the deformation of a sedimentary sequence. The LGD-T32/LGD-T43 cruises of the R/V Legend were designed to test the capability of 8-m-long piston coring offshore southwestern Taiwan. To examine how giant piston coring procedures have shaped the retrieval of sedimentary sequences and affected core quality, we apply well-developed, non-destructive analyses, including physical property measurements, visible color reflectance and the curvature index, to recovered sediments. The continuous sequences of four giant sediment cores at the revisited site are therefore used to provide the basis for comparison with non-destructive results. Rather than dewatering or lithifying the units themselves, we suggest that during the coring procedure, an abnormal pulling force could destroy the balance among the sediments and thus cause the observed deformations of sedimentary features with different magnitudes. We demonstrate that an integration of the curvature index and color reflectance is a better way to evaluate the transformation and distorted sedimentary sequences. Furthermore, using a Taiwan Ocean Research Institute (TORI)-revised piston could potentially produce an abnormal pulling force inside a tube and causing oversampling and distorted sedimentary features, as evidenced by integrated results.