Chronostratigraphy of the Pliocene–Pleistocene boundary in forearc basin fill on the Pacific side of central Japan: Constraints on the spatial distribution of an unconformity resulting from a widespread tectonic event

Utsunomiya, Masayuki; Kusu, Chie; Majima, Ryuichi; Tanaka, Yuichiro; Okada, Makoto

doi:10.1016/j.quaint.2017.05.034

Cited by 7 publications

(13 citation statements)

References 33 publications

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“…1a), the late Miocene sediments underwent clockwise rotation due to the Izu-Bonin Arc collision, which occurred after 4 Ma (Yoshida et al 1984). Moreover, the paleomagnetic record of Pliocene sediments during the Mammoth reversed polarity subchronozone in the Miura Peninsula shows a clockwise rotation of 28.4° (Utsunomiya et al 2017). Several paleomagnetic studies have implied that the collisions of the Izu-Bonin Arc affected the paleomagnetic directions of Miocene-Pleistocene sediments in the Boso and Miura Peninsulas.…”

Section: Magnetostratigraphymentioning

confidence: 99%

Pliocene integrated chronostratigraphy from the Anno Formation, Awa Group, Boso Peninsula, central Japan, and its paleoceanographic implications

Haneda

Okada

2019

Prog Earth Planet Sci

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The Pliocene climate is one of the best analogs for the climate of a globally warmer future. Here, we present a new Pliocene integrated chronostratigraphy from the Anno Formation in the uppermost Awa Group, which is distributed throughout the Boso Peninsula, central Japan, based on paleomagnetic and benthic foraminiferal oxygen isotope records. This new chronostratigraphy provides valuable constraints for paleoceanographic and paleoclimatic studies in the northwestern Pacific Ocean, where the number of paleoceanographic records is limited due to the lack of calcareous microfossils from deep-sea sediment cores, with the exception of some plateaus at water depths above the calcite compensation depth (CCD). Paleomagnetic results indicate that the Anno Formation corresponds to the period extending from the Nunivak normal polarity subchronozone (4.493-4.631 Ma) to Chron C2An.2n (3.116-3.207 Ma), which is just above the Mammoth reversed polarity subchronozone. Although foraminifera are not found in the middle Anno Formation, our oxygen isotope records from the upper and lower Anno Formation demonstrate the recording of glacial-interglacial cycles. However, the amplitude of our δ 18 O profile is much larger than that of the LR04 stack, with similar to slightly lower glacial values and much lower interglacial values. This observation implies that the bottom water had lower δ 18 O values and/or a warmer water mass during interglacials compared with global average deep-water regions.

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Section: Magnetostratigraphymentioning

confidence: 99%

Pliocene integrated chronostratigraphy from the Anno Formation, Awa Group, Boso Peninsula, central Japan, and its paleoceanographic implications

Haneda

Okada

2019

Prog Earth Planet Sci

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“…No signi cant temporal gap corresponding to the Kurotaki unconformity has been identi ed in the Inubo Group, exposed on the Choshi Peninsula, based on biostratigraphy and tephrostratigraphy (Sakai, 1990;Tamura et al, 2014). Utsunomiya et al (2017) demonstrated that the uppermost parts of the Miura Group and the lowermost parts of the Kazusa Group on the Miura Peninsula are time-equivalent deposits, based on the lateral tracing of tephra beds. Gradual variations in the rate of sedimentation indicated that the Kazusa Group of the Miura Peninsula was deposited conformably on the Miura Group during 3.2-2.4 Ma, based on calcareous nannofossil biostratigraphy and magnetostratigraphy.…”

Section: Forearc Basin Lls: the Miura And Kazusa Groupsmentioning

confidence: 99%

Basin-wide erosion and segmentation of the Plio-Pleistocene forearc basin in central Japan revealed by tephro- and biostratigraphy

Utsunomiya

Tamura

Nozaki

et al. 2023

Preprint

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The basement of the Tokyo metropolitan area consists of the Miocene–Pleistocene forearc basin fills that are well exposed around Tokyo Bay, especially on the Miura and Boso peninsulas. The forearc basin fills on these two peninsulas are called the Miura and Kazusa groups, and they were deposited during the late Miocene–Pliocene and Pliocene–middle Pleistocene, respectively. Because many biostratigraphic datum planes, paleomagnetic reversal events, and other chronostratigraphic tools are available for these deposits, they provide the “type stratigraphy” of other equivalent sedimentary sequences on the Japanese islands and in the northwest Pacific. However, the use of such stratigraphic markers has not been fully applied to understand the architecture of a basin-wide unconformity between the Miura and Kazusa groups called the Kurotaki unconformity. For our study, we made correlations among the Pliocene vitric tephra beds based on their stratigraphic levels, lithologic characteristics, the chemical compositions of glass shards, and calcareous nannofossil biostratigraphy. As a result, we were able to correlate tephra beds Ng-Ky25 just above the C3n.3n normal subchronozone (4.7 Ma), IkT16-An157.5 and IkT19-An158.5 near the top of the Mammoth reverse polarity subchronozone (3.21 Ma), and Ahn-Onr (2.6–2.7 Ma) across Tokyo Bay on the Miura and Boso peninsulas. We were able to recognize erosional surfaces and coeval mass-transport deposits immediately below the top of the Mammoth reverse polarity subchronozone, which suggests that submarine landslide(s) may have produced the lack of stratigraphic horizons (4.5–3.2 Ma) in the Miura and eastern Boso regions. Basal pebbly sandstone beds pervasively cover the erosional surfaces, and they show lateral variations into the thick (up to 60 m) mass-transport deposits and overlying turbidite sandstones. The lateral variations in sediment thickness of the post-failure deposits suggest that the basin-wide erosion was associated with the initial growth of a basin-bounding structural high that separates two distinct sub-basins in the forearc basin, which resulted in the subsequent onlapping deposition in the earliest stage of the Kazusa forearc basin. The basin-wide erosion marks the initiation of tectonic reconfigurations that led to segmentation of the forearc basin around the Tokyo Bay region.

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“…Based on geochemical analysis of volcanic glass, Tamura et al (2015) suggested that the Wakebe tephra is correlative with deposits of a widespread tephra intercalated within the Kakegawa, Miura, and Inubo groups in central Japan (Tamura et al, 2014). Importantly, one of these deposits, the Ikg1 tephra (Tamura et al, 2014) in the upper Ikego Formation of the Miura Group, is present within a normal polarity magnetostratigraphic zone, which chronologically corresponds to Chron C2An.2n of the Gauss Chron (Utsunomiya et al, 2017;I. Tamura and M. Utsunomiya, personal communication, 2019).…”

Section: Introductionmentioning

confidence: 99%

Paleomagnetic data as a test of correlations of the Pliocene Wakebe tephra in the Tokai Group, central Japan

Hoshi

2019

Jour. Geol. Soc. Japan

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This paper presents a paleomagnetic test for the correlation of tephra over large areas. A recent preliminary investigation suggests the possibility, based mainly on geochemical data, that the Pliocene Wakebe tephra in the lower Kameyama Formation of the Tokai Group is correlative with a widespread tephra in central Japan that was deposited in a normal polarity subchron of the Gauss Chron (C An). Here, new paleomagnetic data are presented to show that reverse polarity remanent magnetizations are recorded in the Wakebe tephra and in siltstones located immediately above and below the tephra. The results do not support the preliminary correlation of the Wakebe tephra with the widespread tephra of normal polarity, and correlation with this tephra needs to be reconsidered. The Wakebe tephra was deposited between ~. Ma (age of the underlying Akogi tephra) and. Ma (Gauss-Gilbert boundary age) in the late Gilbert Chron (C Ar).

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Chronostratigraphy of the Pliocene–Pleistocene boundary in forearc basin fill on the Pacific side of central Japan: Constraints on the spatial distribution of an unconformity resulting from a widespread tectonic event

Cited by 7 publications

References 33 publications

Pliocene integrated chronostratigraphy from the Anno Formation, Awa Group, Boso Peninsula, central Japan, and its paleoceanographic implications

Pliocene integrated chronostratigraphy from the Anno Formation, Awa Group, Boso Peninsula, central Japan, and its paleoceanographic implications

Basin-wide erosion and segmentation of the Plio-Pleistocene forearc basin in central Japan revealed by tephro- and biostratigraphy

Paleomagnetic data as a test of correlations of the Pliocene Wakebe tephra in the Tokai Group, central Japan

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