Middle Miocene normal faulting along the Tobe Thrust in western Shikoku.

Takahashi, Hideo; Takeshita, Toru; Shibata, Ken; Uchiumi, Shigeru

doi:10.5575/geosoc.98.1069

Cited by 15 publications

(22 citation statements)

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“…In the Tobe area, the MTL has been named the Tobe ‘Thrust’ from the observation that older Cretaceous Izumi Group sediments overlie Miocene Kuma Group sediments. Previous studies in this area show the Early Miocene Kuma Group has undergone compressive tectonics along the MTL, which are lacking in the Middle Miocene Ishizuchi Group (Takahashi 1977; Takagi et al . 1992; Takeshita 1993; Takeda 1996).…”

Section: Age Constraints On Du and Normal Shearingmentioning

confidence: 90%

“…1992; Takeshita 1993; Takeda 1996). Takagi et al . (1992) also show the presence of a normal component overprinting the reverse displacement along the Tobe ‘Thrust’, although the inverse stratigraphy of this fault implies the normal component is smaller than the previous reverse movement.…”

Section: Age Constraints On Du and Normal Shearingmentioning

confidence: 99%

“…(1992) also show the presence of a normal component overprinting the reverse displacement along the Tobe ‘Thrust’, although the inverse stratigraphy of this fault implies the normal component is smaller than the previous reverse movement. Takagi et al . (1992) use K‐Ar dating to suggest an age of the normal fault movement around Middle Miocene (14.7 Ma).…”

Section: Age Constraints On Du and Normal Shearingmentioning

confidence: 99%

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Structural evidence for large‐scale top‐to‐the‐north normal displacement along the Median Tectonic Line in southwest Japan

Fukunari¹,

Wallis²

2007

Island Arc

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The Median Tectonic Line (MTL) is a first‐order tectonic boundary that separates the Sanbagawa and Ryoke Metamorphic Belts. Strike‐slip movements on the MTL have been well documented by many workers. New field based structural studies in the Sanbagawa Belt close to the MTL reveal a large number of secondary faults and semibrittle shear bands indicating a top‐to‐the‐north normal sense of displacement. The strikes of these shear zones and their spatial distributions suggest that development of these structures is related to movements on the MTL. These results imply that the MTL has a large‐scale normal shear component on a regional scale that can help account for the exhumation of the Sanbagawa Belt. Our proposed history of the MTL can also account for changes in the geometry of folds in the Sanbagawa Belt.

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Section: Age Constraints On Du and Normal Shearingmentioning

confidence: 90%

Section: Age Constraints On Du and Normal Shearingmentioning

confidence: 99%

Section: Age Constraints On Du and Normal Shearingmentioning

confidence: 99%

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Structural evidence for large‐scale top‐to‐the‐north normal displacement along the Median Tectonic Line in southwest Japan

Fukunari¹,

Wallis²

2007

Island Arc

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“…In addition to dominant strike‐slip the MTL has also undergone clear normal faulting (Takagi et al . ; Takahashi et al . ; Fukunari & Wallis ).…”

Section: Outline Of the Median Tectonic Line And Geological Settingmentioning

confidence: 99%

Recognition of shear heating on a long‐lived major fault using Raman carbonaceous material thermometry: implications for strength and displacement history of the MTL, SW Japan

et al. 2015

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The extent to which movement on major faults causes long term shear heating is a contentious issue and an important aspect in the debate about the strength of major faults in the crust. Comparing the results of experimental work on the kinetics of crystallization of carbonaceous material with results of thermal modeling show that the Raman carbonaceous material (CM) geothermometer is well suited to studying shear heating on geological time scales in suitable lithologies exposed around exhumed major fault zones. The Median Tectonic Line (MTL), SW Japan, is the largest on‐land fault in Japan with a length of > 800 km. Application of Raman CM thermometry to pelitic schist adjacent to the fault reveals the presence of a rise in peak temperature of around 60 °C over a distance of around 150 m perpendicular to the MTL fault plane. The spatial association of this thermal anomaly with the fault implies it is due to shear heating. Thermal modeling shows the recorded thermal anomaly and steep temperature gradient is compatible with very high rates of displacement over time scales of a few thousand years. However, the implied displacement rates lie outside those generally observed. An alternative explanation is that an originally broader thermal anomaly that developed during strike slip faulting was shortened due to the effects of normal faulting. Constraints on displacement rate, width of the original anomaly, duration of heating and peak temperature imply a coefficient of friction, μ, greater than 0.4.

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“…1 for these areas). References cited are: *1 (Okada 1972), *2 (Takagi et al . 1992), *3 (Takeshita 1993), *4 (Yamakita et al .…”

Section: Geological Settingmentioning

confidence: 99%

Paleocene large‐scale normal faulting along the Median Tectonic Line, western Shikoku, Japan

Kubota¹,

Takeshita

2007

Island Arc

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The Median Tectonic Line (MTL) in southwest Japan, a major east-westtrending arc-parallel fault, has been defined as the boundary fault between the Cretaceous Sambagawa metamorphic rocks and Ryoke granitic and metamorphic rocks, which are unconformably covered by the Upper Cretaceous Izumi Group. The juxtaposition by faulting occurred after the deposition of the Izumi Group. Based on detailed fieldwork and previous studies, the authors reconstruct the kinematic history along the MTL during the Paleogene period, which has not been fully understood before. It is noted that although the strata of the Izumi Group along the MTL dip gently, east-west-trending north-vergent folds with the wavelength of~300 m commonly develop up to 2 km north from the MTL. Along the MTL, a disturbed zone of the Izumi Group up to 400 m thick, defined by the development of boudinage structures with the transverse boudin axis dipping nearly parallel to the MTL, occurs. Furthermore, east-west-trending north-vergent folds with the wavelength of 1-5 m develop within the distance up to 60 m from the MTL. The disturbed zone with the map-scale north-vergent folds along the MTL, strongly suggests that they formed due to normal faulting with a top-to-the-north sense along the MTL. Considering that the normal faulting is associated with the final exhumation of the Sambagawa metamorphic rocks, and its juxtaposition against the Izumi Group at depth, this perhaps occurred before the denudation of the Sambagawa metamorphic rocks indicated by the deposition of the Lower Eocene Hiwada-toge Formation. Dynamic equilibrium between crustal thickening at depth (underplating) and extension at shallow level is a plausible explanation for the normal faulting because the arc-normal extension suggests gravity as the driving force.

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Middle Miocene normal faulting along the Tobe Thrust in western Shikoku.

Cited by 15 publications

References 0 publications

Structural evidence for large‐scale top‐to‐the‐north normal displacement along the Median Tectonic Line in southwest Japan

Structural evidence for large‐scale top‐to‐the‐north normal displacement along the Median Tectonic Line in southwest Japan

Recognition of shear heating on a long‐lived major fault using Raman carbonaceous material thermometry: implications for strength and displacement history of the MTL, SW Japan

Paleocene large‐scale normal faulting along the Median Tectonic Line, western Shikoku, Japan

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