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Volume 42, Issue 1
Displaying 1-5 of 5 articles from this issue
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Takehaya Matsumoto2003 Volume 42 Issue 1 Pages 1-12
Published: February 01, 2003
Released on J-STAGE: August 21, 2009
JOURNAL FREE ACCESSICP-AES was used to determine the major and trace element compositions of 158 pottery shards dating from the 8th to 11th centuries excavated from the northern Tohoku region and 52 Quaternary clay samples collected from the same region. The chemical composition of the pottery was similar to that of the Quaternary clay near ancient sites. Concentrations of Ca, K, and Na in the pottery and clay change systematically from the area near the Japan Sea to the area near the Pacific in the northern Tohoku region. The transition of concentrations of Ca, Na, and K was similar to that of Quaternary volcanic products of the Tohoku region. It is likely that the pottery was made with the clay, which was altered from Quaternary volcanic ash around ancient sites.
I developed three indicators: K/Na+Ca, Ca/Na+K, and Ti/Al+Fe+Mg. Ca, Na, and K are three of the main elements constituting feldspars. Ti, Fe, and Mg are the main elements constituting mafic minerals. Al is abundant in the clay. These indicators show that the element composition of the pottery and the Quaternary clay vary systematically from the region near the Japan Sea to the region near the Pacific. These indicators are useful for provenance studies of pottery from the northern Tohoku region.
The results of this study suggest that in the 8th to 11th centuries, potteries were produced around the sites and utilized there, and that there was no distribution of potteries in wide areas of the northern Tohoku region.View full abstractDownload PDF (1750K) -
Fujio Kumon, Sayuri Kawai, Yoshio Inouchi2003 Volume 42 Issue 1 Pages 13-26
Published: February 01, 2003
Released on J-STAGE: August 21, 2009
JOURNAL FREE ACCESSTotal organic carbon (TOC), total nitrogen (TN), and fossil pollen compositions have been measured at 1- to 2-cm intervals for the upper part of an all-core sample recovered from Lake Nojiri in 1988. TOC and TN contents rapidly increase from the depth zone of 610 to 540cm, with one reversal. The fossil pollen of cool-temperate deciduous trees also becomes abundant around this horizon. Subarctic conifers decrease from 730 to 540cm depth, with some fluctuations.
Judging from these results and sediment ages estimated with 14C dates and some marker tephras, the Last Glacial Maximum is reconstructed to have been around 20, 000yrsBP. A warming suggested by increasing fossil pollen of cool-temperate deciduous trees started around 15, 000yrsBP and lasted until about 11, 000yrsBP (about 12, 000calBP), being intercalated with some cooler phases. The warming was especially accelerated around 12, 000yrs BP (14, 000calBP). The cool phases recognized in the Late Last Glacial Age can be compared with the three Dryas periods in Northern Europe by pattern matching, but their ages are older by about 2, 000 to 3, 000 years. This discordance may be a key to understand the mechanism which controls short-term climate changes.
A slight cooling phase is also recognized around 9, 000yrsBP. This phase is characterized by decreases in TOC and TN contents, but is not so clearly seen in pollen compositions. This phase may be correlated to the Boreal period in Northern Europe.
This study presents the first detailed illustration of climate changes though the termination of the Last Glacial Age in central Japan. The studied core offers a useful standard of climate history, because it can be precisely correlated using the numerous marker tephras.View full abstractDownload PDF (2152K) -
Osamu Fujiwara, Takanobu Kamataki2003 Volume 42 Issue 1 Pages 27-40
Published: February 01, 2003
Released on J-STAGE: August 21, 2009
JOURNAL FREE ACCESSThe radiocarbon dating of sediments using marine shells involves uncertainties because of the mixed age of the shells attributed to the process of “sedimentological time-averaging”. 252 AMS 14C ages of marine shells from 30 shell beds sampled from the Boso Peninsula, central Japan, show the rages of sedimentological time-averaging in the Holocene shell beds, less than 30cm thick, are from several hundred to 6, 500 years.
In order to accurately estimate the depositional age of geologic strata from 14C dating of marine shells and precluding the effect of sedimentological time-averaging, taphonomic and ecologic criteria for dating sample selection were proposed. Indigenous shells ecologically compatible with the depositional environment of the strata yielding the samples (paleogeography, sedimentary fadies, community composition) are recommended. Moreover, fresh (not abraded) shells showing short residence time should be used. The ages determined from fresh indigenous shells converge toward the youngest limit in all shell beds, and show a consistent upward “younging” trend in the depositional sequence. This result suggests a close approach to the “accurate” depositional ages.
Inversion ages remain in the depositional sequence even if the shells were carefully selected by the above two criteria. These inversions may provide key information on the recognition of reworking events, such as tsunami deposits, in comparison with the trend shown by densely determined ages in the depositional sequence.View full abstractDownload PDF (3397K) -
Takashi Sase, Mamoru Hosono, Georg Waldmann, Jun Kimura, Kumiko Aoki2003 Volume 42 Issue 1 Pages 41-48
Published: February 01, 2003
Released on J-STAGE: August 21, 2009
JOURNAL FREE ACCESSAllerødian soils (local name: Mendig soils) covered by Laacher See Tephra on the Middle Rhine river basin in Germany contain phytolith assemblages dominated by festucoid phytoliths originating from the Pooideae. Therefore, the Pooideae clearly dominated the grass flora around Laacher See Volcano during the Allerødian Interstadial about 13, 000 cal BP. This phytolith assemblage corresponds with the Mendig flora containing macrofossil Pooideae such as Festuca sp. found at the base of the Lower Laacher See Tephra.View full abstractDownload PDF (2092K) -
Y. Kumaki, T. Imakire2003 Volume 42 Issue 1 Pages 49-53
Published: February 01, 2003
Released on J-STAGE: August 21, 2009
JOURNAL FREE ACCESSDownload PDF (1329K)
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