Journal of the Sedimentological Society of Japan

Announcing the reorganization of the Sedimentological Society of Japan

Yasuhiko Makino

2003 Volume 56 Issue 56 Pages 1
Published: March 31, 2003
Released on J-STAGE: May 27, 2010

DOIhttps://doi.org/10.4096/jssj1995.56.1

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Shoreface sediments in the Pleistocene Shimosa Group in the Namekata Upland, Ibaraki Prefecture, Japan

Hiroko Okazaki

2003 Volume 56 Issue 56 Pages 3-4
Published: March 31, 2003
Released on J-STAGE: May 27, 2010

DOIhttps://doi.org/10.4096/jssj1995.56.3

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Organic geology of the Miocene muddy rocks in the Tsugaru basin, northern Honshu, Japan

Yoshihiro Ujiié, Kuniko Nishiura, Etsuko Taira

2003 Volume 56 Issue 56 Pages 5-16
Published: March 31, 2003
Released on J-STAGE: May 27, 2010

DOIhttps://doi.org/10.4096/jssj1995.56.5

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Sixty-one outcrop samples of the Miocene muddy rocks from the Umanokamiyama area in the Tsugaru basin, Northern Honshu, were organic-geologically investigated to clarify their organic maturation, organic type and potential for petroleum source rock. The vitrinite reflectance (Ro) and the brightness of pollen (stTAI) indicate that the organic maturity of these rocks may be immature to the threshold of intense oil generation. The composition of visual kerogen shows that almost all samples have amorphous-type organic matter predominantly. The content of amorphous kerogen gradually increases in the interval from the Nagane to Umanokamiyama Formations, which suggests transgression. The abrupt increase, like a spike, of herbaceous kerogen, especially of Pinaceae pollen, was observed in the Genpachimori Formation. These phenomena were also found in the Miocene Odoji Formation of the Nakamuragawa route and the Miocene Odoji-Akaishi Formation of the MITI Nishi-Tsugaru-Oki borehole, although geological correlation by other microfossils has not been established between these formations. From the viewpoint of source rock evaluation, the Miocene muddy rocks in the Umanokamiyama area include a type of kerogen good for oil source and rich organic carbon, but have not undergone organic maturation for petroleum generation.

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Fine-grained sediments dispersion in the eastern part of Osaka Bay, based on distribution of remains of Pediastrum biwae (fresh water green alga) from the Yodo River

Misao Hongo, Takeshi Nakajo

2003 Volume 56 Issue 56 Pages 17-26
Published: March 31, 2003
Released on J-STAGE: May 27, 2010

DOIhttps://doi.org/10.4096/jssj1995.56.17

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Bottom sediments in the eastern part of Osaka Bay are characterized by the predominance of muddy sediments. Remains of fresh water green alga (Pediastrum biwae NEGORO), which are transported exclusively from the Yodo River to Osaka Bay, are distributed in the eastern part of the bay. High concentration of P. biwae were found particularly in the area very close to the Yodo River mouth. Because the settling velocities of remains of P. biwae is assumed to be similar to that of silt or finer grains of quartz, the P. biwae remains were presumably involved with flocculated silt and clay minerals. This suggests that a large volume of terrestrial clastics from the Yodo River settles down close to the Yodo River mouth. Furthermore, fine-grained sediments from the Yodo River also get transported south-southwestward by residual currents as suggested by distributions of P. biwae and grain size of the bottom sediments.

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Ocean current-dominated sedimentary facies of the Upper Miocene Bangamoriyama and Aoso Formations to the north of Sendai, Miyagi Prefecture, Northeast Japan

Mamiko Yoshida, Masaaki Tateishi

2003 Volume 56 Issue 56 Pages 27-39
Published: March 31, 2003
Released on J-STAGE: May 27, 2010

DOIhttps://doi.org/10.4096/jssj1995.56.27

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The Upper Miocene Bangamoriyama and Aoso Formations of the Shida Group are distributed to the north of Sendai, Miyagi Prefecture. These formations are composed of sandy sediments with large-scale trough and planer cross-stratifications. These formations unconformably overlies the Irisugaya Formation, and are unconformably overlain by the Nanakita Formation. These four formations are classified into eleven sedimentary facies, which are grouped into three facies associations (WS, OS, GS). These three facies associations respectively indicate wave-dominated shelf system (WS), ocean currentdominated shelf system (OS) and gravity flow-dominated shelf system (GS). Furthermore, this suggests that the study area was in a strait between the Abukuma and Kitakami Mountains, where a branch of a warm current flowed into during the deposition of the Bangamoriyama and Aoso Formations.

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Founders of sedimentology (4)

Pioneers in sedimentary petrology

Hakuyu Okada

2003 Volume 56 Issue 56 Pages 41-45
Published: March 31, 2003
Released on J-STAGE: May 27, 2010

DOIhttps://doi.org/10.4096/jssj1995.56.41

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Report on the SEPM RESEARCH CONFERENCE; Incised Valleys, Images and Processes

Akiko Omura

2003 Volume 56 Issue 56 Pages 53-57
Published: March 31, 2003
Released on J-STAGE: May 27, 2010

DOIhttps://doi.org/10.4096/jssj1995.56.53

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