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Forearc basin stratigraphy resulting from syntectonic sedimentation during accretionary wedge growth: Insights from sandbox analogue experiments
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  • Atsushi Noda,
  • Hiroaki Koge,
  • Yasuhiro Yamada,
  • Ayumu Miyakawa,
  • Juichiro Ashi
Atsushi Noda
National Institute of Advanced Industrial Science and Technology

Corresponding Author:a.noda@aist.go.jp

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Hiroaki Koge
National Institute of Advanced Industrial Science and Technology
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Yasuhiro Yamada
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Ayumu Miyakawa
Geological Survey of Japan, AIST
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Juichiro Ashi
University of Tokyo
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Forearc basin stratigraphy is expected to record a detailed history of the deformation and growth pattern of an accretionary wedge. However, the relationship between syntectonic basin sedimentation and growth of a wedge remains poorly understood, including (1) how deformation of the wedge modifies the basin stratigraphy and (2) how syntectonic sedimentation influences deformation of the wedge. In this study, we conducted scaled analogue sandbox experiments to reproduce accretionary wedges with and without syntectonic sedimentation. The results show that basin stratigraphy varied with the growth pattern of the accretionary wedge. In the case that wedge growth was dominated by trenchward accretion, the depositional area migrated landward. In contrast, prolonged underthrusting caused the sediment layers to be tilted landward and the depocenter to migrate landward. The occurrence of two types of basin stratigraphy (i.e., trenchward and landward migration of the depocenter) reflects a contrast in strength of the basal shear resistance between the inner and outer parts of the wedge due to sedimentation on the wedge. A change in the magnitude of normal stress acting on the wedge base likely influenced the mode of deformation of the wedge. A phase dominated by underthrusting can result in the combining a retro-wedge basin with a wedge-top basin, and yield a wide area of accommodation space in the forearc basin. These results suggest that forearc basin stratigraphy is influenced by the growth pattern of an accretionary wedge that is affected by syntectonic sedimentation.
Mar 2020Published in Tectonics volume 39 issue 3. 10.1029/2019TC006033