Timing of dextral oblique subduction along the eastern margin of the Asian continent in the Late Cretaceous: Evidence from the accretionary complex of the Shimanto Belt in the Kii Peninsula, Southwest Japan

Abstract

Paleomagnetic studies and hotspot track analyses show that the Kula Plate was subducted dextrally with respect to the Eurasian Plate from the Coniacian to Campanian. However, geological evidence for dextral subduction of the Kula Plate has not been reported from Southwest Japan. Studies of the Coniacian to lower Campanian Miyama Formation of the Shimanto Belt reveal that the mélange fabrics show a dextral sense of shear both at outcrop and microscopic scales. In addition, thrust systems at map‐scale also show dextral shearing. Restored shear directions in the mélange indicate dextral oblique subduction of an oceanic plate. This indicates that the Kula Plate subducted dextrally along the eastern margin of Asia during the Coniacian to early Campanian. Combinations with other published kinematic and age constraints suggest that Southwest Japan experienced a change from sinistral to dextral and back to sinistral shear between 89–76 Ma. This history is compatible with global‐scale plate reconstructions and places good constraints on the timing of plate boundary interaction with the Cretaceous East Asian margin.

Rain‐induced deep‐seated catastrophic rockslides controlled by a thrust fault and river incision in an accretionary complex in the Shimanto Belt, Japan

“…The other is dominated by broken formation and coherent strata. These two units correspond to Type 2 and Type 1 mélange, respectively (Cowan, ; G. Kimura & Mukai, ; Tokiwa, ). Major blocks of > 50 m in length are shown on the geological map (Figure ).…”

Detrital zircon multi‐chronology, provenance, and low‐grade metamorphism of the Cretaceous Shimanto accretionary complex, eastern Shikoku, Southwest Japan: Tectonic evolution in response to igneous activity within a subduction zone

“…The Early Cretaceous subduction of the Izanagi plate beneath the eastern margin of the Asian continent (Engebretson, Cox, & Gordon, ) corresponds to the deposition of the Tochidani and Hinotani units, with the timing of deposition of the Osodani unit being coincident with a magmatic hiatus. Events after the subduction of the Izanagi plate remain uncertain, and previous studies have proposed a change from the Izanagi to the Kula or Pacific plate at 85 Ma (Engebretson et al, ), a change to the Kula plate at 85 Ma (Onishi & Kimura, ), a change to the Kula plate at 89 Ma (Tokiwa, ), and the continuous subduction of the Izanagi plate (Seton et al, ). In particular, several models of Kula–Pacific ridge subduction were developed for the Late Cretaceous, based on geological evidence including the large‐scale magmatism recorded in Southwest Japan (Kinoshita, ), comparison with the geological data at 70–60 Ma in Southwest Japan (Isozaki et al, ), the presence of in situ MORB‐like basalts within the mélange of the Mugi unit at 80 Ma (Kiminami et al, ), and the presence of a high geothermal gradient within the Shimanto accretionary complex at ca 55 Ma (Sakaguchi, , ).…”

Kinematic analysis of mélange fabrics in the Franciscan Complex near San Simeon, California: Evidence for sinistral slip on the Nacimiento fault zone?

“…These fabrics record a consistent kinematic regime that we interpret to be related to synsubduction slip on the Nacimiento fault zone. Although mélanges by defi nition are chaotic mixtures, several studies have identifi ed systematic asymmetric fabrics that give insight into mélange formation processes and/or paleo-plate convergence directions (e.g., Kano et al, 1991;Kusky and Bradley, 1999;Onishi et al, 2001;Ujiie, 2002;Fukui and Kano, 2007;Tokiwa, 2009). Development of systematic shear fabrics at San Simeon postdates the chaotic mixing that has been attributed to either tectonic processes within a subduction channel shear zone (e.g., Cloos, 1984;Cloos and Shreve, 1988) or olistostrome deposition (e.g., Cowan, 1978).…”