Deep-sea sedimentation controlled by sea-level rise during the last deglaciation, an example from the Kumano Trough, Japan
Introduction
Sea-level changes associated with global climate change affect not only coastal environments and landforms, but also the processes by which sediments are transported and deposited on the deep-sea floor. Simple depositional models developed for passive continental margins suggest that turbidite deposition via submarine canyons ceases when sea level rises (e.g. Shanmugam & Moiola, 1982, Vail, 1987, Posamentier et al., 1988). This phenomenon has been recognized in the Amazon deep-sea fan, the Bengal fan, and at other passive and active margins, from analyses of seismic data and the lithological, geochemical, and physical properties of sediments (e.g. Schlünz et al., 1999, Orpin, 2004, Kessarkar et al., 2005, Wien et al., 2006). However, other studies have suggested that the frequency and distribution of turbidites cannot be clearly related to sea-level changes, but may be subject to other controlling factors. These include climatic changes in the source area on land (e.g. Zühlsdorff et al., 2007), autocyclic sediment supply (e.g. Nakajima et al., 1998, Prins et al., 2000, Garziglia et al., 2008), and seismic activity (e.g. Lebreiro et al., 1997).
Variations of depositional patterns in response to sea-level change depend on the characteristics of the local geological setting, such as topography and bathymetry. Large volumes of terrigenous sediment flow into the sea at active plate margins, especially in east Asia (Milliman and Syvitski, 1992). To understand the relationship between sea-level change and deep-sea sedimentation at an active plate margin, we need to understand the origin of the terrigenous clastic sediments that are transported and deposited in the deep sea.
In this study of an active convergent plate margin off Honshu island, Japan, we investigated deep-sea turbidite deposition during the late Pleistocene and Holocene. This period provides good data to investigate sea-floor depositional processes because consideration of the transport routes of clastic sediments can be based on present-day topography and bathymetry. The purpose of this study was to elucidate the relationships among deep-sea sedimentation, coastal environmental change, and relative sea-level rise. Previous studies have reported the deposition of turbidites in deep-sea basins around active plate margins during sea-level highstand (e.g. Weber et al., 1997, Weber et al., 2003, Mullenbach et al., 2004, Kessarkar et al., 2005, Orpin et al., 2006, Blumberg et al., 2008). We also examined the differences of the origins of the turbidites at these active margin basins with those of our study area. To achieve this aim, we analyzed the frequency of deposition of turbidites from sediment cores and deep-sea seismic profiles.
Section snippets
Regional setting
Our study area is in the Kumano Trough, which lies off the Kii and Atsumi peninsulas of central Japan (Fig. 1). The Kumano Trough is a forearc basin along the Nankai Trough, which has been formed by subduction of the Philippine Sea Plate beneath the Eurasian Plate (Fig. 1). The Kumano Trough has a wide basin floor at around 2000 m water depth below a steep continental slope and narrow shelf that is less than 10 km wide. The shelf edge is at about 150 m water depth (Fig. 2). Submarine canyons cut
Seismic reflection profiles
Five seismic reflection profiles used in this study were recorded using a 3.5 kHz sub-bottom profiler near the mouth of Anoriguchi Canyon (Fig. 1, Fig. 2, Fig. 3, Fig. 4). Lines A, B, and C (Fig. 3) were recorded in the mouth of Anoriguchi Canyon during cruise KH06-3 of R/V Hakuho-maru. Line A crosses the canyon axis and lines B and C are approximately parallel to it (Fig. 2). Line B is close to the axis of the canyon. Lines D and E (Fig. 1, Fig. 2, Fig. 4) were recorded across the submarine fan
Seismic reflection profiles
Some characteristic reflection patterns can be recognized in the seismic profiles from the Anoriguchi Canyon mouth area (Fig. 2, Fig. 3). Shallow canyon fill and levees bordering the basinal plain can be recognized in bottom reflectors (Fig. 3A). The canyon in this area is about 7 km wide. The upper surface of the canyon fill shows a single smooth reflector and seismic returns from below that surface are poor in the central part of the canyon (Fig. 3A). Core site KH06-3-PC10 is near the axis of
Temporal changes of the area of turbidite deposition
We consider that the muddy turbidite-free upper parts of the cores 02DMKUPC01 and 02DMKUPC03 correspond to the reflection-free layer observed on seismic lines D and E (Fig. 4, Fig. 5). The underlying reflective layer on lines D and E represents the lower parts of sediment cores, which include pre-Holocene turbidites. On the basin floor (core 02DMKUPC01), the youngest turbidite was deposited before about 14,600 yr BP. A small ridge separates the site of core 02DMKUPC01 from the submarine fan (
Conclusions
We studied high-resolution seismic reflection profiles and depositional ages of turbidites in cores from the eastern Kumano Trough off Japan to investigate depositional patterns in a deep-sea forearc basin along an active convergent plate margin. Our study showed that a submarine canyon was active and provided the main route for transport of terrigenous coarse-grained sediments from land to the deep-sea floor during the lowstand and slow transgression stages of sea-level change. The submarine
Acknowledgements
We are grateful to the captains, officers, crew, and on-board scientists of the GH82, GH97, 02DM, and KH06-3 cruises of R/V Hakurei-maru, R/V Hakurei-maru No 2, and R/V Hakuho-maru for their assistance. We thank the Methane Hydrate Research Consortium (MH21), the Japan Oil, Gas & Metals National Corporation and Dr. M. Tanahashi of the Geological Survey of Japan, AIST, for permission to use data collected by the MH21. Analyses of tephra were by Drs. T. Danhara and T. Yamashita of Kyoto Fission
References (37)
- et al.
Turbiditic trench deposits at the South-Chilean active margin: A Pleistocene–Holocene record of climate and tectonics
Earth Planet. Sci. Lett.
(2008) The isotopic composition of reduced organic carbon
- et al.
Mass-transport deposits on the Rosetta province (NW Nile deep-sea turbidite system, Egyptian margin): Characteristics, distribution, and potential causal processes
Mar. Geol.
(2008) - et al.
The sources and deposition of organic matter in the Late Quaternary Pigmy basin, Gulf of Mexico
Geochim. Cosmochim. Acta
(1990) - et al.
Changing sedimentary environment during the Late Quaternary: Sedimentological and isotopic evidence from the distal Bengal Fan
Deep-Sea Res. Part I
(2005) - et al.
Nature of sediment dispersal off the Sepik River, Papua New Guinea: preliminary sediment budget and implications for margin processes
Cont. Shelf Res.
(2004) - et al.
Sediment deposition in a modern submarine canyon: Eel Canyon, northern California
Mar. Geol.
(2004) - et al.
Channel-levee complexes, terminal deep-sea fan and sediment wave fields associated with the Toyama Deep-Sea Channel system in the Japan Sea
Mar. Geol.
(1998) Holocene sediment deposition on the Poverty-slope margin by the muddy Waipaoa River, East Coast New Zealand
Mar. Geol.
(2004)- et al.
Temporal and spatial complexity in post-glacial sedimentation on the tectonically active, Poverty Bay continental margin of New Zealand
Cont. Shelf Res.
(2006)