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Volume 47, Issue 1
Displaying 1-5 of 5 articles from this issue
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Articles
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Takashi Sase, Hiroshi Machida, Mamoru Hosono2008 Volume 47 Issue 1 Pages 1-14
Published: February 01, 2008
Released on J-STAGE: March 26, 2009
JOURNAL FREE ACCESSWe carried out high-resolution phytolith analysis on the Tachikawa and Musashino Loam formations (Late Pleistocene air-laid tephric soils) in the areas close to Mount Fuji volcano : Sagamino Upland, Ooiso Hill, and the eastern foot of Mt. Fuji, Central Japan.
Fluctuations of bambusoid phytolith assemblage were very likely to synchronize with global climate changes since the marine isotope stage (MIS) 5.1 (5a). The phytolith of Pleiobrastus, a warm temperature dwarf bamboo, dominated in the two layers : 1) the boundary layer between the Shimosueyoshi Loam formation (SL) and the Musashino Loam formation (ML) below Hakone-Anjin tephra (Hk-AP) and 2) upper part of the ML above Hakone-Sanshokuki (Hk-SP). The first warm phase corresponded to the formation of Misaki marine terrace, which correlated with the MIS5.1, and the second corresponded to the Nakatsuhara (Tachikawa-1) fluvial terrace, which correlated with the MIS3.3. On the other hand, the phytolith of Sasa, a cool temperature dwarf bamboo, dominated in the lower part of the ML between Hk-AP and Hk-SP, and in the upper part of the Tachikawa Loam formation (TcL), which starts from Aira-Tn tephra (AT). These two significant cool phases were equivalent to the MISs 4 and 2, stadials in the Last Glacial, respectively. In addition some short warming and cooling phases were recognized in the lower part of the TcL, suggesting fluctuations of climate in the younger period of MIS 3.
Non-bambusoid grass phytolith significantly increased in humic soil layers called black bands in the TcL. This might suggest expansion of grassland vegetation possibly caused by human activity in the Paleolithic era. On the other hand, the phytolith of deciduous broadleaved trees continuously appeared in brown soil layers, which intercepted the formation of humic soil layers.View full abstractDownload PDF (1847K) -
Yasufumi Satoguchi, Noboru Hattori2008 Volume 47 Issue 1 Pages 15-27
Published: February 01, 2008
Released on J-STAGE: March 26, 2009
JOURNAL FREE ACCESSThe Katata Formation, which is the upper part of the Kobiwako Group, is distributed on Katata Hill. This formation intercalates with the Kamiogi I volcanic ash bed, which is a useful key bed for the Middle Pleistocene formations because it is equivalent to the Ks11 tephra bed in the Kazusa Group on the Boso Peninsula. Some tephra beds above this volcanic ash bed are newly described herein. They are named the Ikadachi I, Ikadachi II, and Yamanoshita volcanic ash beds, in ascending order. These tephra beds are correlated with tephra beds in the Kazusa Group on the basis of their petrographic properties, chemical compositions of volcanic glass shards, and stratigraphic positions. The volcanic ash beds Kamiogi II and Ikadachi II in the Kobiwako Group are correlated with the Ks10 and Ks5 tephra beds in the Kazusa Group, respectively. Additionally, the Yamanoshita volcanic ash bed is correlated with K1-175 in the Higashinada 1,700m core taken from Osaka Bay, because 1) their properties are similar and 2) they are both above the abundance bed of Quercus subgen. Cyclobalanopsis. Their estimated ages show that the Katata Hill area was a depositional area until 350 ka at least.View full abstractDownload PDF (1362K) -
Tomoko Anezaki, Kyomi Yamazaki, Hitomi Hongo, Hiroki Sugawara2008 Volume 47 Issue 1 Pages 29-38
Published: February 01, 2008
Released on J-STAGE: March 26, 2009
JOURNAL FREE ACCESSThe lower teeth of the Japanese wild pigs (Sus scrofa leucomystax) from various geographical locations both archaeological and modern were investigated. Buccolingual measurements of the lower third and fourth premolars, and first and second molars are used to compare the regional and temporal differences in dental size of pigs in the Japanese Archipelago.
Similar geographical variations in size of Jomon and modern wild pigs in Japan are observed in our study. The size of pigs from northern localities are larger compared to those from southern localities. Populations from Kyushu are distinctively small in dental size compared to the Honshu in both the Jomon and modern populations.
A different pattern is observed in the Yayoi samples. The pigs from the Yayoi Period show a west-east cline in their size where the populations in the west being larger than those of east. Interestingly to note is that the size of pigs are significantly different between the sites in the northern Kyushu as well as in the western Honshu. The variation in a single region exceeds the geographical variations observed in the Jomon or in the modern samples. We can supose that most of these individuals were brought in from outside the Archipelago. It is a necessity to understand the variation of the modern and archaeological pigs in the Asian continent in order to further discuss the issue morphometrically.View full abstractDownload PDF (447K)
Short Articles
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Yugo Nakamura, Mika Marumo, Kazuomi Hirakawa, Takanobu Sawagaki2008 Volume 47 Issue 1 Pages 39-49
Published: February 01, 2008
Released on J-STAGE: March 26, 2009
JOURNAL FREE ACCESSRausu volcano in the central Shiretoko Peninsula, eastern Hokkaido, has produced three pyroclastic falls : Ra-1 (500-700 cal BP), Ra-2 (ca. 1,400 cal BP), and Ra-3 (ca. 2,200 cal BP), associated with eight pyroclastic flow deposits over the last 2,200 years. These tephras are rich in spongy glass shards with minor plagioclase, orthopyroxene, clinopyroxene, and opaque minerals. They are similar in mineral assemblage, but can be distinguished from each other by refractive indices of dehydrated glass. Tenchozan-a tephra (Ten-a : ca. 1,900 cal BP) from Tenchozan volcano, 4.5km southwest of Rausu volcano, contains abundant lithic fragments associated with flaky glass, plagioclase, orthopyroxene, and clinopyroxene. Its eruption is interpreted as phreatomagmatic. The volume of Ten-a is estimated to be about 0.02km3.
Cores were drilled in 2005 to obtain detailed records of Holocene tephras in peat bogs adjacent to Rausu and Tenchozan volcanoes using a peat sampler and geoslicer. Seven tephra layers were recognized and identified as Komagatake-c1 tephra (Ko-c1 : AD1856), Tarumae-a tephra (Ta-a : AD1739), Komagatake-c2 tephra (Ko-c2 : AD1694), Ra-1 or successive pyroclastic flow deposit, Mashu-b tephra (Ma-b : 774-976 cal BP), and Ichinonuma ash. Ko-c1, Ta-a, and Ko-c2 are the widespread marker tephras from Komagatake and Tarumae volcanoes, southwestern Hokkaido. Ma-b is from Kamuinupuri (a.k.a. Mashudake) volcano, 75km southwest of Rausu volcano. The source volcano and chronology of Ichinonuma ash are unknown. Mashu-l tephra (ca. 13,000 cal BP) is found in the southern part of Shiretoko Peninsula.View full abstractDownload PDF (1235K) -
Kazuaki Hori, Satoru Koide, Masanori Sugiura2008 Volume 47 Issue 1 Pages 51-56
Published: February 01, 2008
Released on J-STAGE: March 26, 2009
JOURNAL FREE ACCESSTwo sediment cores named ST1 and ST2 were taken from the floodplain in the inner part of Nobi Plain to investigate sedimentary facies of the subsurface deposits. Brackish to marine deposits underlying fluvial deposits occur in both cores, and their characteristics, such as sedimentary facies and facies succession, are quite similar to each other, though ST1 is located approximately 280m west of ST2. Sedimentary environment during the deposition of brackish to marine deposits would have been mostly the same in the two sites. Fluvial deposits accumulated since ca. 4,000 cal BP. Overbank mud characterized by abundant thin plant layers has been deposited at the ST1 site, while channel sand and gravel erodes the underlying brackish to marine deposits at the ST2 site. The channel deposits are overlain by overbank mud, as in the ST1. Two well-sorted very fine- to fine-sand beds, at approximately 1 and 5m depth, are intercalated in the mud in both cores. This suggests that these sites had experienced floods, which deposited sands, at least twice.View full abstractDownload PDF (703K)
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