Tephrochronology of the Middle to Late Pleistocene sediments in the northern part of the Boso Peninsula, central Japan

Sugihara, Shigeo; Arai, Fusao; Machida, Hiroshi

doi:10.5575/geosoc.84.583

Cited by 26 publications

(6 citation statements)

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“…Their fission-track ages are dated as 128 G 11 ka (KlP-6) and 132 G 10 ka (KlP-8) (Machida and Suzuki, 1971). Another tephra (TAu-12) was found in the lower part of the Kioroshi Formation in the southern Shimousa Upland (Machida et al, 1974;Sugihara et al, 1978). Its fission-track age is dated as 143 G 11 ka or 147 G 9 ka (Machida, 1977).…”

Section: Geological Settingmentioning

confidence: 99%

A humpback whale, Megaptera novaeangliae (Borowski, 1781), from the Pleistocene Kioroshi Formation of Inba-mura, Chiba Prefecture, central Japan

Nagasawa¹,

Mitani

2004

Paleontological Research

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Section: Geological Settingmentioning

confidence: 99%

A humpback whale, Megaptera novaeangliae (Borowski, 1781), from the Pleistocene Kioroshi Formation of Inba-mura, Chiba Prefecture, central Japan

Nagasawa¹,

Mitani

2004

Paleontological Research

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“…, 198850-70 m , 1988, 1930, 1935;, 1958, 1959, 1962Kikuchi, 1976;, 1978, , 1993, , 1981, 1988, Km2 , 1984, 1988On-Pm1 , 1967, 2003, 1988 GS-TS-1 GS-TS-2 GS-GM-1 3 Fig. 1b Table 2 1988 GS-TS-1 GS-TS-2 III 3 GS-TS-1 5-10 mm - 1.519-1.521 1.520 Table 2 SiO 2 72.53% Al 2 O 3 14.21% FeO 3.22% MgO 0.80% CaO 3.14% Table 3 TS1-11.73 GS-TS-1 10-9 m 2 TS1-9.35, TS1-9.15 GS-TS-2 13-10 m 4 TS2-12.53, TS2-12.35, TS2-12.02, TS2-10.75 1.704-1.715 1.708-1.710 1.518-1.524 1.520-1.521 Table 2 TS1 I II III IV V II GS-TS-2 Km2 TS2-44.94 I , 1984 I Fig.…”

Section: Fig Summary Stratigraphy Of the Pleistocene Shimosamentioning

confidence: 99%

Reexamination on stratigraphy of the Middle to Upper Pleistocene Shimosa Group beneath the Tsukuba Upland, Ibaraki Prefecture, central Japan

Sakata

Naya

Hongo

et al. 2018

Jour. Geol. Soc. Japan

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The stratigraphy of the Middle to Upper Pleistocene Shimosa Group beneath the Tsukuba Upland area of Ibaraki Prefecture, Kanto Plain, central Japan has been reexamined by performing detailed facies observations and analyzing intercalated tephra layers and fossil pollen assemblages in sediment cores. The Pleistocene deposits in the sediment cores are divided into five depositional cycles, each composed of fluvial and coastal sediments that formed under the influence of glacioeustacy. These cycles are correlated with the Yabu, Kamiizumi, Kiyokawa (Kamiiwahashi), Kioroshi, and Joso formations in ascending order based on the tephro-and palyno-stratigraphy. Of note, the incised valley fill beneath the Tsukuba Upland area, which was previously correlated with the Kamiiwahashi Formation (MIS ), corresponds to the Kioroshi Formation (MIS e). The valley was incised during MIS , which was one of the most prominent sea level lowstands of the last ky. The new correlation is consistent with the distribution of equivalent incised valley fills in the Kioroshi Formation beneath the Kanto Plain in Chiba and Saitama prefectures.

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“…Detailed lithological and mineralogical descriptions and regional correlation of the Hy4 volcanic ash layer have been given elsewhere (Mitsunashi, 1973;Machida et al, 1974;Sugihara et al, 1978;Tokuhashi & Endo, 1984). The Higashiyatsu and Jizodo formations are unconformably overlain by the Yabu Formation or young lithostratigraphical units.…”

Section: Geological Settingmentioning

confidence: 99%

“…Aoki & Baba, 1973) and has been interpreted to represent the highest stage of glacio-eustatic sea level cycles (e.g. Machida et al, 1974;Sugihara et al, 1978). Therefore, tuffaceous sediments above the Hy4 volcanic ash layer can be assigned to a condensed section, and the remainder of the Subunit J3-B sediments and the overlying Subunit J4-B sediments can be classified into a highstand systems tract.…”

Section: Sequence Stratigraphymentioning

confidence: 99%

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Diachronous evolution of systems tracts in a depositional sequence from the middle Pleistocene palaeo‐Tokyo Bay, Japan

Itô

O′hara

1994

Sedimentology

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Palaeo‐Tokyo Bay is a relic of the Plio‐Pleistocene Kazusa forearc basin in the Boso Peninsula of Japan. The sedimentary infill of palaeo‐Tokyo Bay is characterized by shallow marine to paralic sediments of the middle to upper Pleistocene Shimosa Group. Sequence stratigraphical analysis has been used to describe spatial and temporal variations in the depositional systems of the lowest units of the Shimosa Group, deposited during the early stage of development of palaeo‐Tokyo Bay. Three different type of depositional systems were recognized: sand ridge to shelf (SRS), shelf to delta (SDL) and shelf to non‐deltaic nearshore (SNS) systems. They overlie early transgressive estuarine deposits infilling lowstand valleys incised in the south‐eastern margin of palaeo‐Tokyo Bay. These systems were developed during late transgressive through highstand stages of a relative sea level cycle, which may have been controlled by a glacio‐eustatic sea level change at about 0·4 Ma. Spatial variation in depositional systems is largely identical to that in modern Tokyo Bay; environmental conditions similar to those prevailing at the present day probably characterized the early history of palaeo‐Tokyo Bay. The timing of highstand systems tracts within a high frequency depositional sequence was analysed in terms of the effect of sedimentation rate, based on the mapping of a chronostratigraphical surface marked by the Hy4 volcanic ash layer. From spatial variations in sedimentation rate, it was possible to identify the diachronous evolution of highstand systems tracts from the SDL system, through the SNS system, to the SRS system. Time lag is indicated by major bounding surfaces, such as maximum flooding or downlap surfaces associated with a condensed section, which developed immediately above or below the Hy4 volcanic ash layer. The lag may be of the order of a few thousands to tens of thousands of years within a depositional sequence with a total of duration of about 100 000 years.

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Tephrochronology of the Middle to Late Pleistocene sediments in the northern part of the Boso Peninsula, central Japan

Cited by 26 publications

References 0 publications

A humpback whale, Megaptera novaeangliae (Borowski, 1781), from the Pleistocene Kioroshi Formation of Inba-mura, Chiba Prefecture, central Japan

A humpback whale, Megaptera novaeangliae (Borowski, 1781), from the Pleistocene Kioroshi Formation of Inba-mura, Chiba Prefecture, central Japan

Reexamination on stratigraphy of the Middle to Upper Pleistocene Shimosa Group beneath the Tsukuba Upland, Ibaraki Prefecture, central Japan

Diachronous evolution of systems tracts in a depositional sequence from the middle Pleistocene palaeo‐Tokyo Bay, Japan

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