A marker tephra bed close to the Lower-Middle Pleistocene boundary: Distribution of the Ontake-Byakubi Tephra Bed in central Japan

doi:10.1016/j.quaint.2015.03.054

Quaternary International

Volume 397, 18 March 2016, Pages 27-38

https://doi.org/10.1016/j.quaint.2015.03.054 Get rights and content

Abstract

Tephrochronology is an exceptionally important tool in the precise regional correlation of Early and Middle Pleistocene sedimentary strata in Japan. The present study reveals that the Yukawa tephra 5 (YUT5) derived from the Older Ontake volcano, the Nezumigawa (Nzg) and Mitamitajima (Mtj) tephras of the Ina Bazin, and the Byakubi-E tephra (Byk-E) of the Boso Peninsula are the same tephra on the basis of their lithofacies, bulk grain composition, mafic mineral composition, major element composition of hornblende, and stratigraphic relationships with the dated tephras. We propose to call the series of tephras correlated with Byk-E the Ontake-Byakubi Tephra Bed (On-Byk Tephra) following the naming convention in which the tephra name consists of the names of the source volcano and the type location. The Matuyama-Brunhes Chronozone boundary occurs just above Byk-E in the type section of the Kokumoto Formation in the Kazusa Group, which is a candidate Global Boundary Stratotype Section and Point (GSSP) for the lower boundary of the Middle Pleistocene Subseries. Therefore, On-Byk Tephra becomes a critically important marker tephra bed for the Early-Middle Pleistocene boundary in central Japan. The present study indicates that the major element composition of hornblende can be a useful tool for identification and correlation of strongly weathered tephra layers such as Nzg and Mtj in which all the volcanic glass shards have been altered.

Introduction

The Kazusa Group, which is widely distributed in the central part of the Boso Peninsula, is representative of Lower and Middle Pleistocene marine sediments in Japan. Comprehensive studies of the lithostratigraphy, biostratigraphy, magnetostratigraphy, and oxygen-isotope stratigraphy of this group have been carried out (Working Group for Quaternary Stratigraphy of Boso, 2009, Kazaoka et al., 2015). A continuous exposure of the Kokumoto Formation, middle part of the Kazusa Group, along the Yoro River, Chiba Prefecture, is a candidate Global Boundary Stratotype Section and Point (GSSP) for the lower boundary of the Middle Pleistocene Subseries (Head et al., 2008). The Kazusa Group contains numerous tephra layers, and the tephrostratigraphy is well constrained by many marker tephras (Mitsunashi et al., 1959, Mitsunashi et al., 1979, Satoguchi, 1995, Satoguchi, 1996, Satoguchi and Nagahashi, 2012). Among the tephra layers, the Byakubi-E tephra (Byk-E: Kazaoka et al., 2015) in the middle part of the Kokumoto Formation, is intercalated approximately 1 m below the Matuyama–Brunhes Polarity Chronozone boundary (Kazaoka et al., 2015). Therefore, Byk-E has the potential to be an important regional marker tephra bed for the Lower-Middle Pleistocene boundary if its distributional area and characteristics for identification and correlation are clarified.

Takeshita et al. (2005) showed that Byk-E is correlated with either the Yukawa tephra 4 or 5 (YUT4 or YUT5) at the foot of Ontake volcano in central Japan, and showed that its source was the Older Ontake volcano. Byk-E has not been correlated, however, with tephra layers in any other locality. In this paper, we show that the Minamitajima (Mtj) and Nezumigawa (Nzg) tephras in the Ina basin, which lies between the Boso Peninsula and the Older Ontake volcano, correlate with Byk-E. This correlation confirms that Byk-E was erupted from the Older Ontake volcano. Furthermore, we show that Byk-E is correlated with YUT5, not YUT4. Here, we propose to call the series of tephras that correlate with Byk-E the Ontake-Byakubi tephra (On-Byk).

Section snippets

Yukawa tephra 4 (YUT4) and Yukawa tephra 5 (YUT5), tephra beds of the Older Ontake volcano

Ontake volcano, which is an active volcano is situated at the southern margin of the Norikura volcanic chain, central Japan (Fig. 1), consists of Older and Younger Ontake volcanoes (Yamada and Kobayashi, 1988). The Older Ontake volcano is estimated to have been active about 0.78–0.39 Ma, based on K–Ar ages of 47 lavas (Kioka et al., 1998). Younger Ontake volcano became active about 0.1 Ma and was the source of a phreatic eruption in 1979 and 2014 (Oikawa, 2014). The products of Younger Ontake

Analytical methods

The tephra samples collected for this study (Nzg, Mtj, and Byk-E from Locality 5) and from previously published studies (YUT4, YUT5, and Byk-E from Locality 4) were prepared as outlined in Fig. 9. The samples were washed ultrasonically after washing in a beaker. The dried residual grains were sieved to obtain the fractions from 1/4 to 1/8 mm and from 1/8 to 1/16 mm. The 1/8 to 1/16 mm fraction was used for analysis of the grain composition. Mafic minerals were separated with a neodymium magnet

Results

The petrographic properties of YUT4 and YUT5, Mtj, Nzg, Byk-E (Locality 4), and Byk-E (Locality 5) tephras are shown in Table 1.

. Petrographic properties of the YUT4, YUT5, Nzg, Mtj, and Byk-E.

Name of tephra	Sampling locality	Bulk grain composition (%)				Mafic mineral composition (%)								Glass morphology	Reference
Name of tephra	Sampling locality	G1	P1	R.F.	M.M.	Hb1	Cpx	Opx	Bt	Opq	Ap	Zr	Gr	Glass morphology	Reference
YUT5	Loc. 1	36.4	50.8	2.6	1.1	88.1	0.4	0.8	−	10.7	+	+	−	P	1
YUT4	Loc. 1	34.6	46.9	4.7	2.8	70.0	0.8	0.4	+	24.5	−	−	−	P	1
Nzg	Loc. 2	–	88.3	2.5	9.2	43.8	0.7	0.4	−	55.1	+	−	−	*	This study
Mtj	Loc. 3	–	86.6	4.7	8.7	39.1	0.8

Potential of major element composition of hornblende for tephra identification and correlation

The correlation and identification of tephra layers are often undertaken by using glass shard characteristics (morphology, refractive index, major and trace element compositions) in addition to lithofacies, mineral composition, stratigraphic relationships, and radiometric age (Machida and Arai, 1992, Lowe, 2011). However, the volcanic glass shards of Mtj and Nzt have been altered by weathering. Thus, the major element composition of hornblende phenocrysts was used to characterise the tephras in

Conclusion

Petrographic features including bulk grain and mafic mineral compositions and the major element composition of hornblende from tephras Mtj and Nzg in the Ina basin have been described and compared with previously published data for tephras YUT4, YUT5, and Byk-E.

We are able to distinguish YUT5 from YUT4 and to correlate Byk-E, Mtj, and Nzg with YUT5 on the basis of the major element composition of hornblende.

We propose that the series of tephras correlated with Byk-E be called the Ontake-Byakubi

Acknowledgements

We thank Prof. Yasuyuki Miyake, Prof. Kuniaki Makino and Mr. Tatsuro Tsugane, Shinshu University for providing many helpful suggestions during the EDS analyses.

References (52)

K. Aoki
Revised age and distribution of ca. 87ka Aso-4 tephra based on new evidence from the northwest Pacific Ocean
Quaternary International
(2008)
O. Kazaoka et al.
Stratigraphy of the Kazusa Group, Boso Peninsula, Central Japan: an expanded and highly-resolved marine sedimentary record from the Lower and Middle Pleistocene
Quaternary International
(2015)
A. Kotaki et al.
Correlation of Middle Pleistocene crystal-rich tephra layers from Daisen Volcano, southwest Japan, based on the chemical composition and refractive index of mafic minerals
Quaternary International
(2011)
D.J. Lowe
Tephrochronology and its application: a review
Quaternary Geochronology
(2011)
H. Machida
The stratigraphy, chronology and distribution of distal marker-tephras in and around Japan
Global and Planetary Change
(1999)
M. Okada et al.
Detailed paleomagnetic records during the Brunhes-Matuyama geomagnetic reversal, and a direct determination of depth lag magnetisation in marine sediments
Physics of the Earth and Planetary Interiors
(1989)
T. Suzuki
Analysis of titanomagnetite within weathered middle Pleistocene KMT tephra and its application for fluvial terrace chronology, Kanto Plain, central Japan
Quaternary International
(2008)
K. Aoki et al.
Late Late Pleistocene tephrostratigraphy of the sediment core MD01-2421 collected off the Kashima coast, Japan
The Quaternary Research (Daiyonki Kenkyu)
(2008)
J.E.T. Channell et al.
Reconciling astrochronological 661 and 40Ar/39Ar ages for the Matuyama-Brunhes boundary and late Matuyama Chron
Geochemistry, Geophysics, Geosystems
(2010)
M.J. Head et al.
The Early–Middle Pleistocene Transition: characterization and proposed guide for the defining boundary
Episodes
(2008)

M. Hyodo

Reversal of Earth's magnetic field -detailed magneto-climatostratigraphy and geomagnetic influence on climate

The Quaternary Research (Daiyonki Kenkyu)

(2014)

M. Hyodo et al.

Millennial to submillennial-scale features of the Matuyama-Brunhes geomagnetic polarity transition from Osaka Bay, southwestern Japan

Journal Geophysical Research

(2006)

M. Itihara et al.

Stratigraphy of the Plio-Pleistocene Osaka Group in Sennan-Senpoku area, South of Osaka, Japan – a standard stratigraphy of the Osaka Group

Journal of Geosciences, Osaka City University

(1975)

K. Kameo et al.

Late Pliocene sea surface environments in the Pacific side of central Japan based on calcareous nannofossils from the lower part of the Chikura Group, southernmost part of the Boso Peninsula

Journal of Geological Society of Japan

(2003)

Y. Kanie et al.

Calcareous nannoplankton age and correlation of the Neogene Miura Group between the Miura and Boso Peninsulas, southern-central Japan

Journal of Geological Society of Japan

(1991)

J. Kimura

The Late Pleistocene Ontake volcano: reappraisal of volcanic activity using volcanostratigraphy combined with tephrostratigraphy

Earth Science (Chikyu Kagaku)

(1993)

H. Kioka et al.

K-Ar chronology of the Middle Pleistocene lavas at Ontake volcano, central Japan

Earth Science (Chikyu Kagaku)

(1998)

K. Kobayashi et al.

The pumice-fall deposit “Pm-I” supplied from Ontake volcano—study of the pumice-fall deposit “Pm-I” supplied from Ontake volcano No. 1

Journal of Geological Society of Japan

(1967)

H. Machida et al.

Atlas of Tephra in and Around Japan

(1992)

H. Machida et al.

Atlas of Tephra in and Around Japan

(2003)

H. Machida et al.

Tephrochronological study on the middle Pleistocene deposits in the Kanto and Kinki districts, Japan

The Quaternary Research (Daiyonki Kenkyu)

(1980)

Geology of the Older Ontake Volcano, Central Japan

Earth Science (Chikyu Kagaku)

(2002)

N. Matsushima

Morphogenetic History of the Ina Basin

(1995)

N. Matsushima et al.

Topography and geology of Iijima town

Iijima town magazine (Iijima chou-shi)

(1990)

N. Matsushima et al.

Geomorphic chronology in relation to the climatic change and the earth movement in Ina tectonic basin, central Japan

Bulletin of the Iida City Museum

(1999)

N. Matsushima et al.

Topography and geology of Komagane city – the area and environment, the history of the land

Komagane City Magazine (Komagane shi-shi)

(2007)

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A marker tephra bed close to the Lower-Middle Pleistocene boundary: Distribution of the Ontake-Byakubi Tephra Bed in central Japan

Abstract

Introduction

Section snippets

Yukawa tephra 4 (YUT4) and Yukawa tephra 5 (YUT5), tephra beds of the Older Ontake volcano

Analytical methods

Results

Potential of major element composition of hornblende for tephra identification and correlation

Conclusion

Acknowledgements

Quaternary International

Quaternary International

Quaternary International

Quaternary Geochronology

Global and Planetary Change

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