2:15 PM - 2:30 PM
[HCG21-03] Localized Development of Contourite Drift on the Outer Rise of the Kuril Trench: A Sediment Trapping Model for Active Margins
Keywords:Contourite Drift, Lower Circumpolar Deep Water (LCDW), Active Margin
Contourite drifts are sediments deposited or reworked by the persistent action of bottom currents and are important archives for reconstructing deep-sea current activity and paleoceanographic changes (Rebesco et al., 2014). While contourite depositional systems (CDS) along passive margins have been well studied (Faugères et al., 1999), knowledge of CDS formation on active margins remains limited due to their complex tectonic and oceanographic settings (Bailey et al., 2021).
The outer rise of the Kuril Trench, located on the northwestern Pacific active margin, is a pathway for the northward-flowing Lower Circumpolar Deep Water (LCDW) (Kawabe & Fujio, 2010). Previous studies have suggested bottom current activity based on erosional features, but the formation processes of contourite drifts remain poorly understood. This study aims to clarify the localized development of CDS on the Kuril Trench outer rise by integrating bathymetric data, multi-channel seismic (MCS) profiles, sub-bottom profiler (SBP) records, and surface sediment cores obtained from the JAMSTEC Seismic Survey Database (JAMSTEC (2004), doi:10.17596/0002069) and recent research cruises.
Our analyses revealed a contourite depositional system influenced by the interaction between bottom currents and Ryofu-Daini Seamount. Characteristic sedimentary features were identified, including, a moat (~90 m relief) on the southeastern side, a tongue-shaped drift (Contourite Sedimentary Tail: CST) (~100 km long, ~50 km wide) to the northeast, and sediment waves (~5 km wavelength, ~20 m height) to the west. Seismic profiles showed internal reflection structures such as downlap and truncation, characteristic of contourite drifts. Sediment cores mainly consisted of diatomaceous silt with volcaniclastics, including pumice and tephra, with sedimentation rates of 4.3 cm/kyr near the seamount and 11.9 cm/kyr at a distal site.
The localized development of CDS is interpreted as being controlled by three factors:
1) Localized flow disturbance and sediment trapping: Flow deceleration and divergence around the seamount promoted sediment accumulation (Hernández-Molina et al., 2006).
2) Mismatch between the central part of the bottom current and the depositional surface: The central part of the DWBC flows at depths of 5500–6000 m, deeper than the depositional area at 5000–5300 m, limiting large-scale sediment transport.
3) Limited sediment supply and winnowing: The outer rise is isolated from terrigenous input, enhancing winnowing by bottom currents (McCave, 2008).
These findings suggest that CDS formation on the outer rise of active margins is driven by localized flow disturbances and sediment trapping, distinct from the widespread drift development model of passive margins.
References: Bailey, W.S., et al. (2021). Sedimentology.; Faugères, J.C., et al. (1999). Mar. Geol.; Hernández-Molina, F.J., et al. (2006). Mar. Geol.; Kawabe, M., & Fujio, S. (2010). J. Oceanogr.; McCave, I.N. (2008). Dev. Sedimentol.; Rebesco, M., et al. (2014). Mar. Geol.; JAMSTEC Seismic Survey Database (2004) Japan Agency for Marine-Earth Science and Technology, https://doi.org/doi:10.17596/0002069. Accessed 12. 7, 2023.
The outer rise of the Kuril Trench, located on the northwestern Pacific active margin, is a pathway for the northward-flowing Lower Circumpolar Deep Water (LCDW) (Kawabe & Fujio, 2010). Previous studies have suggested bottom current activity based on erosional features, but the formation processes of contourite drifts remain poorly understood. This study aims to clarify the localized development of CDS on the Kuril Trench outer rise by integrating bathymetric data, multi-channel seismic (MCS) profiles, sub-bottom profiler (SBP) records, and surface sediment cores obtained from the JAMSTEC Seismic Survey Database (JAMSTEC (2004), doi:10.17596/0002069) and recent research cruises.
Our analyses revealed a contourite depositional system influenced by the interaction between bottom currents and Ryofu-Daini Seamount. Characteristic sedimentary features were identified, including, a moat (~90 m relief) on the southeastern side, a tongue-shaped drift (Contourite Sedimentary Tail: CST) (~100 km long, ~50 km wide) to the northeast, and sediment waves (~5 km wavelength, ~20 m height) to the west. Seismic profiles showed internal reflection structures such as downlap and truncation, characteristic of contourite drifts. Sediment cores mainly consisted of diatomaceous silt with volcaniclastics, including pumice and tephra, with sedimentation rates of 4.3 cm/kyr near the seamount and 11.9 cm/kyr at a distal site.
The localized development of CDS is interpreted as being controlled by three factors:
1) Localized flow disturbance and sediment trapping: Flow deceleration and divergence around the seamount promoted sediment accumulation (Hernández-Molina et al., 2006).
2) Mismatch between the central part of the bottom current and the depositional surface: The central part of the DWBC flows at depths of 5500–6000 m, deeper than the depositional area at 5000–5300 m, limiting large-scale sediment transport.
3) Limited sediment supply and winnowing: The outer rise is isolated from terrigenous input, enhancing winnowing by bottom currents (McCave, 2008).
These findings suggest that CDS formation on the outer rise of active margins is driven by localized flow disturbances and sediment trapping, distinct from the widespread drift development model of passive margins.
References: Bailey, W.S., et al. (2021). Sedimentology.; Faugères, J.C., et al. (1999). Mar. Geol.; Hernández-Molina, F.J., et al. (2006). Mar. Geol.; Kawabe, M., & Fujio, S. (2010). J. Oceanogr.; McCave, I.N. (2008). Dev. Sedimentol.; Rebesco, M., et al. (2014). Mar. Geol.; JAMSTEC Seismic Survey Database (2004) Japan Agency for Marine-Earth Science and Technology, https://doi.org/doi:10.17596/0002069. Accessed 12. 7, 2023.