The Quaternary Research (Daiyonki-Kenkyu)

A Record of Precipitation Change for the Past 140ka Based on Diatom Valve Flux in Lake Biwa, Japan

Michinobu Kuwae, Shusaku Yoshikawa, Yoshio Inouchi

2003 Volume 42 Issue 5 Pages 305-319
Published: October 01, 2003
Released on J-STAGE: August 21, 2009

DOIhttps://doi.org/10.4116/jaqua.42.305

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For high-resolution reconstruction of climate change in Lake Biwa catchment area, we have analyzed concentration of diatom valve (DVC; valves g^-1) and diatom valve flux (DVF; valves cm^-2 yr^-1) for the past 140ka using the upper part of a 140-m core from Takashima-oki. Time resolution of sampling intervals is 150 to 500 years.
The DVF records show higher values during the Holocene (0-7ka) and the last interglacial age (68-135ka) than the present value. By contrast, during the last glacial age (7-68ka) the DVF is relatively low. In addition, the DVF record shows millennial-scale fluctuations over the last 140ka.
We have checked the relationship among the DVF, sedimentation rate, and climatic parameters such as temperature, snow depth, and precipitation. We concluded that the DVF reflects diatom productivity, which is strongly controlled by the precipitation level of the preceding summer period.
If the DVF can be a proxy for precipitation, the characteristics of the precipitation around Lake Biwa are summarized as follow: the low-level duration during 56-68ka, corresponding to the oxygen-isotope stage 4, is longer than that during the LGM (oxygen-isotope stage 2); after 8ka, the levels gradually rise toward 5.5ka, and increased levels occur at 3 and 5.5ka.
The pattern and the episodic events in the record of the DVF in the Lake Biwa sediment can be very closely correlated to the Dansgaard-Oeschger episodes in the North Atlantic climatic record which is revealed from the Greenland ice core. This concordance indicates a possible teleconnection between the precipitation over Japan and temperature over the North Atlantic. The possible mechanism of the teleconnection might be related to changes in westerlies which are driven by temperature changes over the North Atlantic.

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Chrono-stratigraphy of the Ina Group, Central Japan, Based on Correlation of Volcanic Ash Layers with Pleistocene Widespread Tephras

Yusuke Suganuma, Takehiko Suzuki, Haruo Yamazaki, Takao Kikuchi

2003 Volume 42 Issue 5 Pages 321-334
Published: October 01, 2003
Released on J-STAGE: August 21, 2009

DOIhttps://doi.org/10.4116/jaqua.42.321

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The Ina Group consists of the Lowermost Formation, the Ina Formation (subdivided into the Lower and the Upper members by the interbedded Misobeta Member), and the Kume Formation, in ascending order. Previous workers had attempted to estimate the age of the Ina Group based on paleophytological and stratigraphic correlations. However, there are still inconsistencies in their chronological estimates. To address our purpose, six tephras intercalated in the Ina Group have been investigated using observations of outcrops, petrography (including refractive indices of volcanic glasses and orthopyroxene), and chemical composition of volcanic glasses. The Tomita-1 tephra and the Kume tephra are correlated with the Ebisutoge-Fukuda tephra at 1.75Ma and the Ks18 tephra at 0.6Ma, respectively. The results reveal that the Plio-Pleistocene boundary is located in or below the Lower Ina Member and that the upper part above the Kume tephra in the Kume Formation must have been deposited during the Middle Pleistocene based on the age of the Ks18 tephra. Our chronological study on the Ina Group suggests that uplifting of the Akaishi Range accelerated during 1.4 to 1.0Ma and that uplifting of the Kiso Range accelerated ca. 0.6Ma.

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Depositional Process of the Holocene Nobi Plain, Central Japan, Reconstructed from Drilling Core Analysis

Masaaki Yamaguchi, Toshihiko Sugai, Osamu Fujiwara, Hiroo Ohmori, Taka ...

2003 Volume 42 Issue 5 Pages 335-346
Published: October 01, 2003
Released on J-STAGE: August 21, 2009

DOIhttps://doi.org/10.4116/jaqua.42.335

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The Nobi Plain is located in the lower reaches of three Japanese major rivers-the Kiso, Nagara, and Ibi-which run from the Central Alpine Region toward Ise Bay, Central Japan. This plain is typical in its high subsidence rate and relatively strong fluvial processes with well-developed fluvial landforms, such as alluvial fans and natural levees.
Holocene depositional processes of the Nobi Plain, which is 45km long and 30km wide, were reconstructed from detailed AMS ¹⁴C dating and facies analyses of drilling cores. The Holocene sediments, which are divided into six sedimentary units (based on their facies)-basal gravel, incised valley, prodelta, deltafront, delta plain, and tidal or fluvial channel, in ascending order-were deposited under sea-level and tectonic influences. Accumulation rates in the Nobi Plain were relatively high compared with other Japanese Holocene sedimentary basins, and varied from 1 to 53mm/yr; the variation is related to the relative sea-level change, which is attributed to high sediment flux from the rivers and rapid subsidence of the basin. The lower two depositional facies were deposited in the transgressive stage from 12, 000yrs BP to 5, 900cal yrs BP, and the upper four depositional units forming the Kiso river delta covering the large area of western part of the Nobi plain prograded in the regressive stage that followed. Progradation rates have been low (6m/yr) during 5, 900-4, 200cal yrs BP, high (10m/yr) during 4, 200-2, 800cal yrs BP, and low again (5m/yr) from 2, 800cal BP to the present, corresponding to changes in the geometry of the sediment supply and depositional systems.

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Optically Stimulated Luminescence (OSL) Dating of Shallow Marine Sediments

Ryuta Hataya, Masaaki Shirai

2003 Volume 42 Issue 5 Pages 347-359
Published: October 01, 2003
Released on J-STAGE: August 21, 2009

DOIhttps://doi.org/10.4116/jaqua.42.347

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We examined the OSL dating of shallow marine sediments, for the purpose of dating marine terrace deposits. First, we carried out optical bleaching/heating/HF-etching experiments using quartz grains and determined a sample preparation procedure in our laboratory on the basis of these results. Next, we conducted OSL dating using the multiplealiquot additive-dose method of shallow marine sediments from the upper part the Kioroshi Formation in Ibaraki Prefecture, which are correlated to Marine Oxygen Isotope Stage (MIS) 5e-5c. OSL ages of foreshore and foreshore-shoreface beds are 88-112ka, and are in good agreement with geological/geomorphological data. On the other hand, OSL ages of the backshore bed are younger, and those of the shoreface bed are older than geologically estimated ages. These results show that optical bleaching of OSL of quartz grains during the depositional process of foreshore and foreshore-shoreface beds was complete. Therefore, we conclude that the OSL dating method can date shallow marine sediment using samples from foreshore and foreshore-shoreface beds, and that this method can distinguish terrace deposits formed in MIS 5 from those formed in MIS7 by taking geomorphologic information into account.

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¹⁴C Dating of Fossil Woods in the Terrace Gravel Beds along the Upper Reach of the Azusa River, Central Japan

Takeyuki Ueki, Nobuo Yamamoto

2003 Volume 42 Issue 5 Pages 361-367
Published: October 01, 2003
Released on J-STAGE: August 21, 2009

DOIhttps://doi.org/10.4116/jaqua.42.361

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Fluvial terraces of the Azusa River crop out to the north of Shirahone Spa, western Nagano Prefecture, central Japan. The terrace deposits and related gravels 320m above the modern bed underlie the air-laid AT tephra bed and contain fossil woods >46, 140 ¹⁴C yrs BP, respectively, suggesting the Hata Surface in the Matsumoto Basin as their correlatives. Average incision rate of the upper reach of Azusa River during the last 50 or 70 ka is estimated to 5 to 7mm/yr. The lowest boundary of the alpine zone at the first half of the last Glacial should have been higher than 1, 360m above sea level.

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An Outcrop of Hashikura Fault, the Median Tectonic Line, Found along a Southern Foot of Asan Range in Tokushima Prefecture, Southwestern Japan

Takashi Morie

2003 Volume 42 Issue 5 Pages 369-372
Published: October 01, 2003
Released on J-STAGE: August 21, 2009

DOIhttps://doi.org/10.4116/jaqua.42.369

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