5:15 PM - 7:15 PM
[MIS23-P02] Correlation and transport processes of turbidites in marine cores off Muroto, Japan
Keywords:turbidite, non-destructive, correlation, transportation process
This study aims to analyze turbidites intercalated between two marine core samples collected off Cape Muroto, to elucidate their transport processes. The two cores, PC03 (located at the base of the continental slope in the Muroto Basin at a depth of 1,210 m) and PC02 (located approximately 4 km east of the foot of the continental slope at 1,280 m depth), were collected during the KS-22-4 research cruise. Continuous elemental analysis using an XRF core scanner, organic matter analysis, and paleocurrent analysis from magnetic susceptibility anisotropy were conducted to estimate the origin and transport processes of the turbidites. The sediments in both cores are primarily composed of hemipelagic mud with intercalated turbidites, along with K-Ah tephra (7,200 yr.) in the bottom. A total of 21 turbidite layers were identified in the PC02 core, and 28 layers in the PC03 core, confirmed through visual and X-CT scanning.
Elemental peaks in the turbidites included K, Ca, Mn, Fe, and Br in both cores, although these elements did not always show consistent trends, likely due to variations in the origin and scale of the turbidites. Organic matter analysis revealed a significant difference in the carbon isotope ratio (13C) between the turbidites and the hemipelagic mud before the deposition of the turbidites. The turbidites showed a significantly lighter trend, suggesting the incorporation of terrestrial organic matter. The maximum and average differences in 13C were 0.38 and 0.17 for PC03, and 0.14 and 0.07 for PC02, indicating differing trends between the base of the continental slope (PC03) and a location further east (PC02).
Paleocurrent estimations were made based on natural remanent magnetization measurements. The results indicated a predominantly north-south flow direction, with magnetic susceptibility anisotropy intensity showing overlap between turbidites and hemipelagic mud in PC03, while the two were distinctly separated in PC02. This suggests that turbidites in PC03 were directly deposited while being transported upward from the continental slope, whereas those in PC02 were subject to reworking during deposition. Both cores indicate a southward flow direction, revealing the transportation of terrestrial organic matter from the shallow continental shelf to the base of the continental slope by turbidites.
Reference
Ashi et al., 2024 JpGU abstract.
Elemental peaks in the turbidites included K, Ca, Mn, Fe, and Br in both cores, although these elements did not always show consistent trends, likely due to variations in the origin and scale of the turbidites. Organic matter analysis revealed a significant difference in the carbon isotope ratio (13C) between the turbidites and the hemipelagic mud before the deposition of the turbidites. The turbidites showed a significantly lighter trend, suggesting the incorporation of terrestrial organic matter. The maximum and average differences in 13C were 0.38 and 0.17 for PC03, and 0.14 and 0.07 for PC02, indicating differing trends between the base of the continental slope (PC03) and a location further east (PC02).
Paleocurrent estimations were made based on natural remanent magnetization measurements. The results indicated a predominantly north-south flow direction, with magnetic susceptibility anisotropy intensity showing overlap between turbidites and hemipelagic mud in PC03, while the two were distinctly separated in PC02. This suggests that turbidites in PC03 were directly deposited while being transported upward from the continental slope, whereas those in PC02 were subject to reworking during deposition. Both cores indicate a southward flow direction, revealing the transportation of terrestrial organic matter from the shallow continental shelf to the base of the continental slope by turbidites.
Reference
Ashi et al., 2024 JpGU abstract.