Elsevier

Marine Geology

Volume 288, Issues 1–4, 1 October 2011, Pages 49-60
Marine Geology

Geomorphological development of the Goto Submarine Canyon, northeastern East China Sea

https://doi.org/10.1016/j.margeo.2011.06.013Get rights and content

Abstract

The geomorphological development of submarine canyons is controlled by multiple factors, such as sea-level fluctuations, tectonic activity, and ocean currents, but the relative contributions of each factor vary among these canyons. The development of submarine canyons along active rift margins is not fully understood because there are relatively few documented examples of such phenomena. The Goto Submarine Canyon offers a good example of this type of structure because it is located on the flank of the Okinawa Trough, which is an active back-arc basin. Through multi-beam bathymetry, multi-channel seismic reflection profiling, and remotely operated vehicle surveys, we reveal that this canyon is more than four times wider than other submarine canyons and has a gradient that is half as deep and a remarkably flat canyon floor. A series of upstream-facing cliffs with reliefs up to 110 m and longitudinal lineaments are also associated with this canyon. These morphological features can mainly be attributed to direct sediment inputs from the Yellow River during glacial stages, vertical incision prevented by erosion-resistant beds, and faulting and tectonic tilting of resistant strata. The possibility of tidal current-induced erosion is also suggested. These processes have been influenced primarily by regional factors, such as the wide continental shelf, carbonate cementation, and active rifting of the Okinawa Trough. The contribution of rifting, including faults and tectonic tilting, to the canyon's morphology is expected to be a general characteristic of submarine canyons along active rifting margins.

Graphical abstract

Highlights

► We conducted multibeam, MCS, and ROV surveys in the Goto Submarine Canyon. ► The canyon has remarkably shallow-gradient and flat-floored morphology. ► Upstream-facing cliffs and longitudinal escarpments are also remarkable. ► These morphologies are due to sea-level change and erosion-resistant beds. ► Active back-arc rifting and tidal current also affect the morphology of the canyon.

Introduction

The geomorphological characteristics of submarine canyons vary widely in terms of width, gradients, and cross-canyon profiles. They are strongly affected by the magnitude, composition, and frequency of sediment supplies, which are attributed to sea-level fluctuations, tectonic setting and activity, and ocean currents (e.g., Shanmungam et al., 1985). The contributions of each factor can be classified with respect to the tectonic setting.

Tectonic activity along passive margins is expected to have a relatively small effect on canyon development. Canyon development is controlled by other factors, including ocean currents (Lastras et al., 2009), slope failure and landslides (Green and Uken, 2008), tidal current- and cascade-induced sediment transport (Stigter et al., 2007, Trincardi et al., 2007), incision across shelves and the proximity of the canyon head to the shore (Stigter et al., 2007), sediment transport by longshore currents, offshore wind-blown sediments, and mass wasting (Antobreh and Krastel, 2006).

The contribution of tectonic activity to canyon development along convergent margins is more evident than along passive margins. For example, in the Tenryu and Kushiro submarine canyons along the Pacific coast of Japan, the canyon gradients have been repeatedly steepened due to seamount subduction (Soh and Tokuyama, 2002, Noda et al., 2008). Similarly, in the Gaoping Canyon in southwestern Taiwan, rapid tectonic uplift has caused intense sediment discharge from terrestrial rivers, thus maintaining active canyon incision, even during the present high-stand stage (Yu et al., 2009).

Along strike–slip margins, faults cause abrupt lateral displacements that prevent the development of straight canyons as observed in those along the Hikurangi margin in New Zealand (Mountjoy et al., 2009). In the Monterey Canyon, an active strike–slip fault causes frequent earthquakes that result in landslides and mass wasting (McHugh et al., 1998, Le Dantec et al., 2010).

In contrast to these examples, the number of well-studied submarine canyons along active rift margins is very small. Only a few active continental rifts exist, including the East African Rift Valleys, the Red Sea, the Gulf of Aden, the Andaman Sea, and the Okinawa Trough. Among them, only the Okinawa Trough has a documented submarine canyon, the Goto Submarine Canyon (Katsura, 1992). However, the detailed morphology of the Goto Submarine Canyon is not sufficiently understood for use in discussing the characteristics of submarine canyons along active rift margins. Reconstructing the history of the canyon will also be valuable for understanding the sediment supply to the Okinawa Trough, which will help clarify the process of back-arc rifting at the continental margin.

In this report, we describe the morphological development of the Goto Submarine Canyon, discuss the relationship between the canyon's development and the active rifting of the Okinawa Trough, and attempt to understand common morphological characteristics of submarine canyons that have developed along active rift margins.

Section snippets

Regional tectonic and oceanographic setting

The East China Sea margin is a convergent margin between the Philippine Sea Plate and the Eurasian Plate with an active back-arc basin known as the Okinawa Trough (Fig. 1b). The Okinawa Trough has been rifting since the Late Miocene, with NNE-trending normal fault activity in its northern region (e.g., Letouzey and Kimura, 1986, Sibuet et al., 1995), which has formed a half-graben structure (Letouzey and Kimura, 1986) and resulted in stratification with a southeastward incline (Oiwane et al.,

Methods

We conducted the following three types of surveys: 1) a multi-beam bathymetric survey, 2) a multi-channel seismic reflection survey, and 3) direct seafloor observations using a remotely operated vehicle (ROV).

Bathymetric data were acquired using a RESON SEABAT 8160 multi-beam echo-sounder system with a normal sonar frequency of 50 kHz and an angular-coverage sector of 126 beams per ping at 1.5°. Bathymetric data were acquired during the NT08-18 cruise of the R/V Natushima of the Japan Agency for

Morphological outline

An overview of the bathymetric data obtained in this study is shown in Fig. 2a. The Goto Submarine Canyon has a flat, ~4 km wide canyon floor and a shallow canyon gradient (1:125). Cross-canyon arcuate and along-canyon linear escarpments are documented within the canyon. The former type of escarpment consists of three upstream-facing cliffs crossing the entire width of the canyon floor (Fig. 2a and d). These cliffs are 30 to 110 m high and are designated as cross-canyon escarpments. The latter

Discussion

The Goto Submarine Canyon exhibits remarkable characteristics, such as a wide canyon floor with a flat morphology, shallow gradient, and two types of escarpments. We will discuss the development of these geomorphologies to examine whether they can be regarded as general characteristics of submarine canyons developed along active rift margins.

Conclusions

Geological and geophysical surveys conducted in the Goto Submarine Canyon revealed several morphological characteristics of the canyon and implied mechanisms for their development. The canyon exhibits remarkable characteristics, such as a wide canyon floor with a flat morphology, a shallow gradient, and two types of escarpments.

During glacial stages, lowering of the sea level caused progradation of the Yellow River mouth approximately 900 km seaward and resulted in direct discharge into the

Acknowledgments

We thank Juichiro Ashi, Masaaki Shirai, Kiyoshi Shimamura, and Hideki Miura for helpful discussions concerning submarine erosion and the morphology of submarine canyons. Robert G. Jenkins kindly identified shells and gave us important information about their ecology. Mayuri Inoue identified living and dead corals from dive-survey footage. Stephen Obrochta kindly assisted with the English translation. We also thank the officers, crews, and technicians who provided essential help with data

References (40)

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