The Origin of the Paleo‐Kuril Arc, NE Japan: Sediment Provenance Change and Its Implications for Plate Configuration in the NW Pacific Region Since the Late Cretaceous

• Published in: Tectonics (Washington, D.C.) D.C.), 2022-12, Vol.41 (12), p.n/a
• Main Authors: Harisma, H., Naruse, H., Asanuma, H., Hirata, T.
• Format: Article
• Language: English
• Subjects: Age; Age structure; Continental margins; Cratons; Cretaceous; detrital zircon; Hokkaido‐Japan; Isotopes; Izanagi Plate; Pacific Plate; Paleogene; Paleo‐Kuril Arc; Precambrian; sediment provenance; Subduction; Zircon
• ISSN: 0278-7407; 1944-9194
• DOI: 10.1029/2022TC007299

The Nemuro Belt is a tectonic belt in the Paleo‐Kuril Arc system, the NW Pacific region. The Paleo‐Kuril Arc has been interpreted as an intraoceanic arc system between the Izanagi and Pacific Plates during the Late Cretaceous, suggesting that the boundary between these plates was a trench. However, this study shows it was a volcanic arc that developed atop a continental margin. To determine the nature of this arc during the Late Cretaceous, U‐Pb ages of detrital zircons from the Nemuro and Urahoro Groups in the Paleo‐Kuril Arc were analyzed. Our results identify two distinct types of detrital zircon U‐Pb age distributions. The first (Type 1) is characterized by multimodal age distributions with peaks ranging from ca. 1.8 Ga to 78 Ma. The other (Type 2) exhibits a unimodal age distribution with a peak at 60‐52 Ma. These different age distributions indicate a provenance transition occurred between the Late Cretaceous and Paleogene. Precambrian zircons in Type 1 sandstones indicate that the Paleo‐Kuril Arc was part of a continental plate, presumably the Okhotsk Block, in NE Asia during the Late Cretaceous. In contrast, Type 2 sandstones were supplied only from the magmatic arc region that the Izanagi‐Pacific Ridge subduction could have activated. This provenance transition suggests the initially continental arc became separated from its continental source at the beginning of the Paleogene. Plain Language Summary Understanding the origin of the Paleo‐Kuril Arc is important for the plate tectonic history of the NW Pacific region. It is closely related to controversy regarding subduction of the oceanic ridge that may have existed between the Izanagi and Pacific Plates. This study aims at testing the hypothesis that the Paleo‐Kuril Arc system developed as an intraoceanic arc along the boundary between two oceanic plates. Detrital zircon U‐Pb age distributions from sandstones of the Nemuro and Urahoro Groups of the Paleo‐Kuril Arc terrain are examined. If the Paleo‐Kuril Arc was a volcanic arc formed between oceanic plates associated sandstones should not contain craton‐derived detrital zircon grains of Precambrian age. Detrital zircons of Precambrian age are common in Upper Cretaceous sandstones of the Nemuro Group, suggesting that the Paleo‐Kuril Arc developed as a continental arc system rather than an intraoceanic arc system. A new model in which a continental Paleo‐Kuril Arc emerged initially at the southern end of the Okhotsk Block during the Late Cretaceous