Tectonic Synthesis: A Plate Reconstruction Model of the NW Pacific Region Since 100 Ma

Abstract

Based on the results of interdisciplinary study from Chapters 1-4, a plate tectonic model of the northwestern Pacific region since 100 Ma is presented in this chapter. The evolution of the Pacific margin is viewed as a longstanding history of migration/amalgamation of allochthonous blocks onto the subduction zone. Such a process inevitably provoked diverse tectonic events, spatiotemporal positions of which have been discussed in this book. In order to reconcile paradoxical discrepancies in the docking process of arc fragments, the authors introduce a marginal sea plate with a spreading center that was alive in the Cretaceous. Oblique subduction of the ridge caused specific migratory igneous activity along the rim of the overriding plates, together with flips of shearing direction. Arc-trench systems on the eastern and western sides of the marginal sea plate developed following different timelines and were eventually mixed up during the plate's closure that prompted formation of a coincident Oligocene clinounconformity widespread on the Eurasian margin. Since the demise of the hypothetical plate, the tectonic regime of the northwestern Pacific margin has been controlled by the growth, namely, the rotational history and modes of convergence of the Philippine Sea Plate.

日本海拡大以来の日本列島の堆積盆テクトニクス

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Linking Pacific Plate Motions to Metamorphism and Magmatism in Japan During Cretaceous to Paleogene Times

“…Published Japan-NW Pacific plate reconstructions attempt to fill the uncertain gaps using various geological or geophysical inferences; however, these models show contrasting plate kinematics (i.e., plate convergence rates and obliquity), plate geometries, and even differ on the identity of past subducting oceanic plates. For example, published plate models disagree on whether the Kula plate, the Izanagi plate, or other unnamed backarc basins or oceanic plates were subducted along Japan during the Cretaceous to present (e.g., Maruyama et al 1997;Seton et al 2015;Itoh et al 2017;Wu et al 2022a). Of particular importance is the lack of agreement on reconstructed spreading ridge subduction events during the Cretaceous to early Cenozoic; proposals include trench-orthogonal to trench-parallel ridge-trench intersections at different times (e.g., Maruyama et al 1997;Seton et al 2015 ridge-trench intersections are problematic because they imply very different geological contexts, subducting plate ages, and thermal regimes during the Sanbagawa and Ryoke metamorphic events in the Cretaceous (e.g., Wallis et al 2009;Yamaoka and Wallis 2023).…”

Post-Opening Deformation History of the Japan Sea Back-Arc Basin: Tectonic Processes on an Active Margin Governed by the Mode of Plate Convergence

“…Based on the detailed geologic research of the Sundaland, Hall [11] adopted lingering expansion and rotational motion of the Philippine Sea Plate. On the other hand, Itoh et al [12] advocated an earlier migration of the marginal sea plate. Their kinematic model is dependent on the collision of the easternmost tip of the clockwise-rotating southwest Japan against the Izu-Bonin arc along the eastern margin of the Philippine Sea Plate from 15 to 12 Ma [13].…”