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Volume 51, Issue 1
Displaying 1-4 of 4 articles from this issue
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The Paper for the 2010 Japan Association for Quaternary Research Award
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Shusaku Yoshikawa2012 Volume 51 Issue 1 Pages 1-19
Published: February 01, 2012
Released on J-STAGE: April 27, 2012
JOURNAL FREE ACCESSQuaternary sediments in the Osaka sedimentary basin are composed mainly of nonindurated sand, gravel, silt, and clay intercalated with a number of volcanic ash layers. These sediments consist of two sedimentary units. The lower unit contains only freshwater facies, while the freshwater facies in the upper unit are frequently intercalated with marine clay beds, labeled Ma-1, Ma0, ……Ma13 in ascending order. Twenty-one sedimentary cycles in the upper unit, which represent alternating flu-violacustrine sediments and marine clay beds, indicate successive climatic changes from glacial to interglacial periods. The Quaternary sequences in the Osaka Basin can be correlated to oxygen isotope records obtained from deep sea cores, based on a combination of litho-, bio-, magneto-, and tephro-stratigraphy. The twenty-one marine clay beds, each of which represents a marine transgression, were deposited during interglacial high sea-level periods from Marine Isotope Stage 37 to Stage 1. The Ma 3, Ma 6, and Ma 9 marine clay beds, which are characterized by a warm-temperate paleoclimate and high sea levels, can be regarded as the most useful marker horizons for Mid-Pleistocene stratigraphy.View full abstractDownload PDF (2342K)
Article
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Hitomi Takemoto, Koji Okumura2012 Volume 51 Issue 1 Pages 21-33
Published: February 01, 2012
Released on J-STAGE: April 27, 2012
JOURNAL FREE ACCESSWe examined the relationship between pollen assemblage changes and geomorphic development in Kamishiro Basin, Nagano Prefecture. The data for pollen analysis were collected on the walls of the Hakuba trench across Kamishiro fault excavated in 1996 by Geological Survey of Japan.
The trench exposed four discrete faulting events in the past 7,000 years. Some of these events are correlated with simultaneous rising of the local base of erosion. In particular, the emergence of L 2 terrace coincides with Ev. 3. We examined geomorphological and paleohydrological evidence associated with base-level change and earthquakes and tried to correlate the change with innovation of pollen assemblage.
Five local pollen zones and two sub-zones were recognized from the result of the analysis. I : 105,000-9,000 cal yrs BP, II : 9,000-7,700 cal yrs BP, III : 6,000-4,300 cal yrs BP, IV (sub-zone IV-a and IV-b) : 4,300-1,700 cal yrs BP, V : 1,200 cal yrs BP∼.
The pollen assemblage changes from zone III show the change of the moisture in Kamishiro Basin very well.
The result of this analysis revealed the correlation that pollen assemblages such as Alnus and Osmunda have changed simultaneously with river bed morphology. These assemblages are presumed to respond to the moisture in the basin. Moreover, the pollen assemblages form the Riparian forest also increase in phase with the emergence, especially in zone IV (about 4,000-3,000 cal yrs BP). These allow us to presume that the moisture in Kamishiro Basin de-creased. Then, we can conclude that the changes observed on the pollen assemblages reflect the coseismic subsidence of the hanging wall side of the Kamishiro fault. Considering that landform changes were caused by faulting, the pollen assemblages make it possible to record past fault activity based on the alternations verified.View full abstractDownload PDF (1746K)
Short Article
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Toshinori Matsui, Masahide Ishizuka, Masahiko Konomatsu2012 Volume 51 Issue 1 Pages 35-43
Published: February 01, 2012
Released on J-STAGE: April 27, 2012
JOURNAL FREE ACCESSAn 8-m-long drilling core was obtained from the middle part of the Ayagawa River basin, Ayagawa Town, Kagawa Prefecture, northeastern Shikoku Island, Japan. Nine lithofacies were identified in the core, and samples were taken for radiocarbon dating and pollen analysis.
The radiocarbon dating results revealed that upper Pleistocene terrace deposits from 8.00m to 3.55m depth were overlain by Holocene deposits from 3.55m depth to the ground surface.
Pollen of Quercus subgen. Lepidobalanus, which are deciduous broad-leaved trees, was dominant during the middle of the last glacial period, indicating a cool environment in the Ayagawa River basin, whereas during the early postglacial period, the dominance of deciduous broad-leaved tree pollen along with pollen of Quercus subgen. Cyclobalanopsis, which are evergreen broad-leaved trees, indicates a somewhat cool environment. Subsequently, in the later postglacial period, the environment became warm, as is shown by the occurrence of pollen of both subgenus Cyclobalanopsis and Conifers. In general, our results agree with previous results for the Seto Inland Sea region, except for the low occurrence of Castanopsis pollen in the later postglacial period in our results, suggesting that Castanopsis was rare at that time in the upper Ayagawa River basin and that the area around Ayagawa Town was dry, with annual precipitation of less than 1200mm.View full abstractDownload PDF (1635K)
Note
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Takuichiro Kuwabara2012 Volume 51 Issue 1 Pages 45-48
Published: February 01, 2012
Released on J-STAGE: April 27, 2012
JOURNAL FREE ACCESSDownload PDF (542K)
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