The Amami Rift: Clarifying the roles of rifting and volcanism in the central Ryukyu Arc

Minami, Hiroki; Saitou, Kenji; Ohara, Yasuhiko

doi:10.1016/j.margeo.2022.106839

Cited by 3 publications

(4 citation statements)

References 50 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We successfully located a hydrothermally active area on the Amami Rift during HOV SHINKAI 6500 dive #1726 (Figures 1 & 2), presumably responsible for the cluster of acoustic anomalies detected in 'Area A' of Minami et al (2022). In the earlier part of the dive (Figure 1B), we explored an area around the northernmost acoustic anomalies in Area A (28°3 6.4 ′ N-28°36.5 ′ N, 128°44.1 ′ E-128°44.2 ′ E) but did not locate any signs of venting.…”

Section: Resultsmentioning

confidence: 99%

“…The discovery of the Amami Rift hydrothermal vent field paves the way for follow-up studies toward a better understanding of how disparate community structures arise in nearby shallow vents. Vent fluid composition may be a key driver, and that of Amami Rift could be distinct from other Ryukyu vents due to its unique geological background at the intersection of Ryukyu Arc and Okinawa Trough (Minami et al ., 2022). Biogeochemical characteristics of underwater volcanism in the Ryukyu region remains understudied (Shinjo and Kato, 2000), and how lava type and depth influence vent fluid chemistry in this region requires further research.…”

Section: Discussionmentioning

confidence: 99%

“…From the acoustic water column anomalies (‘bubble plumes’) detected in the Amami Rift, we targeted a northern cluster (called ‘Area A’ in Minami et al ., 2022: figs. 2b, 4d) of signals for ground-truthing.…”

Section: Methodsmentioning

confidence: 99%

“…The Amami Rift, previously known as the Amami Caldera, is located around 50 km northwest of Amami-Oshima, at the intersecting point between the volcanic front of the central Ryukyu Arc and rifting activity of the Okinawa Trough (Minami et al ., 2022). Surveys using ship-based and autonomous underwater vehicle (AUV) acoustic echo-sounding has revealed several rising gas plumes around 630 m depth, a typical feature of vent orifices in the Ryukyu region due to the rich gas content of their vent fluids (Nakamura et al ., 2015); further confirmed with smoke-like plumes visualised by the AUV's side-scan sonar imagery plus temperature anomalies (Minami et al ., 2022). Known active vent fields in the Ryukyu region mostly occur below 1000 m (Brunner et al ., 2022), making this a shallow site.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Faunal community of a new hot vent field on the Amami Rift

Chen,

Hookabe,

Komatsu

2024

J. Mar. Biol. Ass.

View full text Add to dashboard Cite

Deep-sea hydrothermal vents host chemosynthesis-based ecosystems inhabited chiefly by specially adapted animals that do not live anywhere else, and depth has been shown to be a major driver of species composition at vents around Japan. Though the Ryukyu region in southern Japan is home to many hot vents, only two – Minami-Ensei Knoll and Yoron Hole – have been found shallower than 1000 m. Here, we report the discovery of a new vent field on the Amami Rift northwest off Amami Ōshima at 630 m deep. A total of 29 macrofaunal species were recorded from Amami Rift, including 19 vent specialists. Comparison of species composition across the three shallow Ryukyu vents revealed only three shared species, highlighting that all three display distinct community structure. Amami Rift exhibits distinct zonation patterns and is generally more similar to Minami-Ensei than Yoron Hole, but the presence of key taxa such as the sulphide worm Paralvinella and the mussel ‘Bathymodiolus’ platifrons as well as the absence of the symbiotic squat lobster Shinkaia and the limpet Lepetodrilus exemplify its difference with Minami-Ensei. Furthermore, the non-vent specific predators seen in these two sites were completely different. Overall, the Amami Rift vent field can be considered a shallow vent with a unique set of fauna, warranting future research on the mechanisms shaping disparate macrofaunal diversity between nearby shallow vents such as Amami Rift and Minami-Ensei. The unusual geological setting of Amami Rift at the converging point of Okinawa Trough and Ryukyu Arc may influence fluid chemistry to drive such differences.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Faunal community of a new hot vent field on the Amami Rift

Chen,

Hookabe,

Komatsu

2024

J. Mar. Biol. Ass.

View full text Add to dashboard Cite

show abstract

Shear‐Dominant Continental Rifting in Northern Ryukyu Revealed by Ambient Noise Tomography

Chen,

Kuo,

Lin

et al. 2024

JGR Solid Earth

View full text Add to dashboard Cite

In this study, we reveal the deformational structure of the crust of the northern part of the Ryukyu Arc and Okinawa Trough using ambient noise tomography. Compared with southern Ryukyu, the northern segment exhibits a wide and shallow basin, a crust without localized thinning, slow extension rates, and highly arc‐oblique, right‐lateral retreat of the Ryukyu Arc. We present both isotropic and azimuthally anisotropic shear‐wave velocity models using data recorded by an ocean‐bottom seismometer array and nearby island stations. The isotropic model demonstrates a monotonic decrease in velocity from the backarc to the forearc, in accord with the accretionary‐prism origin of the latter. The resolved azimuthal anisotropy exhibits arc‐parallel and arc‐perpendicular fast shear‐wave polarization directions in the upper to mid‐crust and the lower crust to uppermost mantle in much of the arc and backarc, respectively. We interpret the arc‐parallel anisotropy as resulting from the anisotropic fabrics aligned by the vertical shearing imposed by the right‐lateral motion of the Ryukyu Arc. The underlying arc‐perpendicular anisotropy may be attributed to horizontal shearing driven by corner flow in the mantle wedge. We found arc‐perpendicular anisotropy in the forearc upper crust, which may reflect crack alignment caused by the collision of the Amami Plateau. The oblique arc retreat and the resolved deformation fabrics in the arc and backarc together attest to the shear‐dominant, transtensional nature of the northern Ryukyu continental rift system. Some of the features in northern Ryukyu may be better explained from the perspective of transtensional rifting.

show abstract

Gs21 航海での高分解能サブボトムプロファイラー探査に基づくトカラ列島周辺海域の海底下浅部構造

MISAWA,

FURUYAMA,

KOGE

et al. 2023

Bull. Geol. Surv. Japan

View full text Add to dashboard Cite

During the GS21 cruise, in October 2021, a high-resolution subbottom profiler (SBP) survey was conducted focusing on the volcanic front around the Tokara Islands using R/V Shinyo Maru (Tokyo University of Marine Science and Technology) to obtain geological information on the shallow subbottom structure in this area. In this paper, we summarize the shallow subbottom structure around Higashi-Shin Sone, the southern area of Gajashima Island, the Gogo Sone area, and the Amami Trough near the Tokara Islands revealed by SBP surveys. The area around Higashi-Shin Sone and the southern area of the Gajashima Island tend to have fewer faults and submarine volcanoes than the area around Gogo Sone, and the sedimentary layers consisting of stratified structures are well developed. Around Gogo Sone, depressions and stepped bathymetry, probably caused by faults, have developed, and topographic highs that are thought to be submarine volcanoes have been recognized between the islands. In the Amami Trough, a reflective surface characterized by sand waves has been observed on the northern slope of Oshima-Shin Sone. In addition, the bedding plane of the sedimentary sequence has been exposed as in a cuesta, which is a type of erosion morphology, in some places due to erosion.

show abstract

The Amami Rift: Clarifying the roles of rifting and volcanism in the central Ryukyu Arc

Cited by 3 publications

References 50 publications

Faunal community of a new hot vent field on the Amami Rift

Faunal community of a new hot vent field on the Amami Rift

Shear‐Dominant Continental Rifting in Northern Ryukyu Revealed by Ambient Noise Tomography

Gs21 航海での高分解能サブボトムプロファイラー探査に基づくトカラ列島周辺海域の海底下浅部構造

Contact Info

Product

Resources

About

The Amami Rift: Clarifying the roles of rifting and volcanism in the central Ryukyu Arc

Cited by 3 publications

References 50 publications

Faunal community of a new hot vent field on the Amami Rift

Faunal community of a new hot vent field on the Amami Rift

Shear‐Dominant Continental Rifting in Northern Ryukyu Revealed by Ambient Noise Tomography

Gs21 航海での高分解能サブボトムプロファイラー探査に基づく トカラ列島周辺海域の海底下浅部構造

Contact Info

Product

Resources

About

Gs21 航海での高分解能サブボトムプロファイラー探査に基づくトカラ列島周辺海域の海底下浅部構造