Fission track ages of eight tuffs in the upper part of the Awa Group, Boso Peninsula, central Japan.

Tokuhashi, Shuichi; Danhara, Tohru; Iwano, Hideki

doi:10.5575/geosoc.106.560

Cited by 20 publications

(8 citation statements)

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“…Vertical arrows indicate the calcareous nannofossil data from Kameo and Sekine (2013). Red triangles indicate radiometric ages for tephra marker beds from previous studies as follows: *1 An85 from Ueki et al (2018), *2 An77 from Makinouchi et al (1983), and *3 An73 and An49 from Tokuhashi et al (2000). d Polarities based on the vertual geomagnetic pole (VGP) latitudes shown in Fig.…”

Section: Oxygen Isotope Stratigraphymentioning

confidence: 97%

“…Magnetostratigraphy (Niitsuma 1976), planktonic foraminiferal biostratigraphy (Oda 1977), calcareous nannofossil biostratigraphy (Kameo and Sekine 2013), and fission track dating (Tokuhashi et al 2000) studies have been conducted on the Anno Formation ( Fig. 1d).…”

Section: Previous Chronostratigraphic Studies Of the Anno Formationmentioning

confidence: 99%

“…Some radiometric ages have also been reported for tephra markers and widespread tephra beds that can be correlated with those in the Anno Formation. Tokuhashi et al (2000) reported fission track ages for An49 (3.9 ± 0.4 Ma) and An73 (3.7 ± 0.2 Ma) following the ζ-calibration (Hurford 1990a) of tephra marker beds from the lower Anno Formation. The Kosugaya volcanic ash bed in the Tokai Group (known as Ksg-An77) was dated to 4.0 ± 0.5 Ma using fission track dating (Makinouchi et al 1983).…”

Section: Previous Chronostratigraphic Studies Of the Anno Formationmentioning

confidence: 99%

“…Therefore, the Sak slump bed may have eroded strata for a duration of approximately 90 kyr, which extends from immediately after the peak of MIS M2 (3.295 Ma) to just before the polarity switch at the termination of the Mammoth subchron (3.207 Ma). An age model based on our chronostratigraphy of the Anno Formation is shown with the calcareous nannofossil bioevents (Kameo and Sekine 2013) and radiometric ages of tephra marker beds (Makinouchi et al 1983;Tokuhashi et al 2000;Ueki et al 2018) in Fig. 10.…”

Section: Oxygen Isotope Stratigraphymentioning

confidence: 99%

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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: Oxygen Isotope Stratigraphymentioning

confidence: 97%

Section: Previous Chronostratigraphic Studies Of the Anno Formationmentioning

confidence: 99%

Section: Previous Chronostratigraphic Studies Of the Anno Formationmentioning

confidence: 99%

Section: Oxygen Isotope Stratigraphymentioning

confidence: 99%

See 2 more Smart Citations

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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“…2-4 3 Am Ky An , An1 , 1993An1 , , 1994An1 , , 1995An1 , , 1997An1 , , 1998 , An-a Appendix A Tokuhashi et al (2000). The calcareous nannofossil biostratigraphy is from Kameo et al (2002Kameo et al ( , 2010Kameo et al ( , 2013.…”

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confidence: 99%

The thin-skinned deformations and folding of the upper Awa Group (Neogene) in the Boso Peninsula, Japan

晃洋

活志

敦³

2015

Jour. Geol. Soc. Japan

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The folding of Neogene-Quaternary strata on Boso Peninsula, central Japan, has been attributed to differential vertical movements of basement blocks. Previous researchers have suggested that the folding resulted from two-dimensional, thick-skinned deformations along a vertical cross-section perpendicular to the fold axes. To test this hypothesis, we investigated the geologic structures in an area with dimension of km in the southern part of the peninsula, where the upper Awa Group (upper Miocene-Pliocene fore-arc basin fill) makes E-W trending folds. We found that lateral variations in stratal thicknesses record three-dimensional syn-depositional mapscale movements that are incompatible with the model of two-dimensional fold structures; moreover, outcrop-scale faults also record patterns of three-dimensional deformations. Bedding faults, including a map-scale flat-ramp structure and an outcrop-scale hinterland-dipping duplex, both show NNE vergence, indicating that the strata were subjected to thin-skinned rather than thick-skinned deformation.

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Major variations in vitrinite reflectance and consolidation characteristics within a post-middle Miocene forearc basin, central Japan: A geodynamical implication for basin evolution

et al. 2017

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Fission track ages of eight tuffs in the upper part of the Awa Group, Boso Peninsula, central Japan.

Cited by 20 publications

References 0 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

The thin-skinned deformations and folding of the upper Awa Group (Neogene) in the Boso Peninsula, Japan

Major variations in vitrinite reflectance and consolidation characteristics within a post-middle Miocene forearc basin, central Japan: A geodynamical implication for basin evolution

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