Late Jurassic–Early Cretaceous intra-arc sedimentation and volcanism linked to plate motion change in northern Japan

Abstract

-The Sorachi Group, composed of Upper Jurassic ophiolite and Lower Cretaceous island-arc volcano-sedimentary cover, provides a record of Late Jurassic-Early Cretaceous sedimentation and volcanism in an island-arc setting off the eastern margin of the Asian continent. Stratigraphic changes in the nature and volume of the Sorachi Group volcanic and volcaniclastic rocks reveal four tectonic stages. These stages resulted from changes in the subduction direction of the Pacific oceanic plate. Stage I in the Late Jurassic was characterized by extensive submarine eruptions of tholeiitic basalt from the back-arc basin. Slab roll-back caused rifting and sea-floor spreading in the supra-subduction zone along the active Asian continental margin. Stage II corresponded to the Berriasian and featured localized trachyandesitic volcanism that formed volcanic islands with typical island-arc chemical compositions. At the beginning of this stage, movement of the Pacific oceanic plate shifted from northeastward to northwestward. During Stage III, in the Valanginian, submarine basaltic volcanism was followed by subsidence. The Pacific oceanic plate motion turned clockwise, and the plate boundary between the Asian continent and the Pacific oceanic plate changed from convergent to transform. During Stage IV in the Hauterivian-Barremian, in situ volcanism ceased in the Sorachi-Yezo basin, and the volcanic front migrated west of the Sorachi-Yezo basin.

Mesorbitolina (Cretaceous larger foraminifera) from the Yezo Group in Hokkaido, Japan and its stratigraphic and paleobiogeographic significance

“…An important radiolarian datum plane correlated to the Early Barremian time, the last occurrence of Cecrops septemporatus, was identified in the middle-to-upper part of the Shirikishimanaigawa Formation in the Yubari-Ashibetsu area (Takashima et al, 2001(Takashima et al, , 2006 33), 34) and in the uppermost part of Pechikunnai Formation in the Nakagawa area (Kawaguchi, 1997; Mitsugi and Hirano, 1998).…”

Cretaceous Research: Paleolatitudes and Northward Migration of Crustal Fragments in the NW Pacific Inferred from Paleomagnetic Studies

“…It seems, however, that their hypothesis clashes with the evidence of arc volcanism, as mentioned above. Takashima et al [28] proposed an alternative idea that the geologic unit was transported by left-lateral slips on the margin between the Eurasian and Izanagi Plates. Although oblique subduction is a plausible cause of the large migration, lateral motion on the plate margin changed to a dextral direction after the demise of the Izanagi Plate [29].…”

Stratigraphic and Petrological Insights into the Late Jurassic– Early Cretaceous Tectonic Framework of the Northwest Pacific Margin

“…Since the rocks of the Sorachi Group are laterally discontinuous [31], the Sorachi Group is divided into four rock assemblages based on the age and characteristics of the igneous rocks: (1) Uppermost Jurassic (tholeiitic basaltic rock assemblage), (2) Berriasian (andesitic rock assemblage), (3) Valanginian (basaltic rock assemblage), and (4) Hauterivian-Barremian (tufaceous rock assemblage).…”

“…In terms of radiolarian biostratigraphy, the irst occurrence of Pseudodictyomitra carpatica, which is assigned to be Tithonian, was identiied at the lower part of the Hachimoriyama Tuf Member and the Nae Formation [31].…”

“…Of the Japanese islands, Hokkaido Island and the northeastern part of Honshu Island are considered to have been located on the supra-subduction magmatic zone-convergent boundary between the Paleo-Paciic Plate and the South China Block during the Early Cretaceous [27,31]. The western part of Hokkaido Island is well suited for reconstructing the spatiotemporal characteristics of geodynamic evolution across the suprasubduction zone because the strata from the accretionary complex to the magmatic zones are intermitently well exposed.…”