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Volume 37 (1998)
- Issue 5 Pages 349-
- Issue 4 Pages 283-
- Issue 3 Pages 155-
- Issue 2 Pages 59-
- Issue 1 Pages 1-
Volume 37, Issue 3
Displaying 1-13 of 13 articles from this issue
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Yugo Ono, Tadamichi Oba, Itaru Koizumi1998 Volume 37 Issue 3 Pages 155-163
Published: July 31, 1998
Released on J-STAGE: August 21, 2009
JOURNAL FREE ACCESSDownload PDF (1314K) -
Kiichi Moriwaki, Kazuomi Hirakawa, Masao Nakada1998 Volume 37 Issue 3 Pages 165-175
Published: July 31, 1998
Released on J-STAGE: August 21, 2009
JOURNAL FREE ACCESSThe issues of the extent of Antarctic ice sheet and relative sea level change since the last glaciation are discussed on the basis of the stratigraphy and the 14C-dates of raised beach deposits from the circum-antfrctic coastal areas. Although the Antarctic ice sheet is a fundamental factor in a discussion of the global climate and oceanographic systems, there has been little agreement on the extent of the ice sheet even during the Last Glacial Maximum (LGM). Radiocarbon dates from some places along the Sôya Coast are clearly classified into two groups; the younger 3-8ka and the older 33-45ka without reservoir correction. The older 14C-dates suggest the occurrence of a transgression or a relatively high sea level during the interstadial of marine isotope stage 3.
The extent of the Antarctic ice sheet during the LGM must have been smaller than that of the Maximum Model developed by Stuiver et al. (1981), which has established a significant boundary condition for the modeling of the past climate and its change.View full abstractDownload PDF (1715K) -
Yoko Ota1998 Volume 37 Issue 3 Pages 177-180
Published: July 31, 1998
Released on J-STAGE: August 21, 2009
JOURNAL FREE ACCESS -
Dansgaard-Oeschger Cycles and Heinrich EventsYoshiyuki Fujii1998 Volume 37 Issue 3 Pages 181-188
Published: July 31, 1998
Released on J-STAGE: August 21, 2009
JOURNAL FREE ACCESSRecent results from Greenland deep ice core studies have revealed 24 glacial interstadials which are characterized by large (a range of 5-7°C) and abrupt climate changes over a few decades, called the Dansgaard-Oeschger cycle. Massive iceberg discharge (Heinrich event) was followed by Bond cycle bounding of Dansgaard-Oeschger cycles. By reviewing recent studies, the present paper emphasizes two stable modes in the global climate system, and the role of thermohalaine in the occurrence of abrupt warming during the last glacial period. Furthermore, the possibility of a shift of the current climate mode to another resulting from an increase in precipitation due to the current global warming and the cessation of thermohaline circulation is introduced.View full abstractDownload PDF (1017K) -
Toshiro Naruse1998 Volume 37 Issue 3 Pages 189-197
Published: July 31, 1998
Released on J-STAGE: August 21, 2009
JOURNAL FREE ACCESSEolian dust deposited during the last glacial age is distributed widely in east Asia. Eolian dust within the peat core of Nakaikemi in Tsuruga, paleosols on the Shirasu ignimbrite plateau in Kagoshima, and eolianite in Kikai Island were deposited in several periods dated as 12kyr, 14kyr, 17-18kyr, 21kyr, 27kyr, 31kyr, 35kyr, 38kyr, and 42kyr BP. ESR signal intensity of fine quartz (finer than 20μm) shows that eolian dust dated from 17kyr to 38kyr in Nakaikemi peat core was transported from north Asian Precambrian rock areas such as Siberia and Mongolia by the NW winter monsoon. On the other hand, eolian dust dated at 12kyr and 42kyr in Nakaikemi peat core and eolian dusts of Kagoshima and Kikai Island were transported from the central Asia by the summer subtropical jet stream.
Spikes in the dust deposition series match major changes in Neogloboquadrina pachyderma (s.) percentage in North Atlantic core V23-81 and loess-paleosol sequences of Chinese loess in Lanzhou and Luochuan. Ages of the dust depositional spike also match those of Dansgaard-Oeschger cold events and Heinrich events. This suggests that abrupt changes in dust deposition synchronized with global climatic changes such as Dansgaard-Oeschge Cycle.
The strength of the Asian winter monsoon may have accelerated the transport and deposition of eolian dust. Since Overpeck et al. (1996) pointed to the contribution of eolian dust as a potential source of episodic warming during the last glacial age, dust loading on snow fields of the Tibetan Plateau and associated snow darkening may have strengthened the summer monsoon. High eolian dust loading may have caused significant, episodic warming in east Asia. Dust-induced changes in the monsoon may have a role in triggering climate changes.View full abstractDownload PDF (1253K) -
Yoshihiro Ganzawa, Kouji Kubokita, Naota Suzuki, Fuminori Osanai1998 Volume 37 Issue 3 Pages 199-204
Published: July 31, 1998
Released on J-STAGE: August 21, 2009
JOURNAL FREE ACCESSThermal luminescence (TL), a phenomenon which can be seen in such minerals as feldspar and silica, is applied to investigation of the origin of the clay layers (loess deposits) that cover a vast surface of the Japanese landform. In utilizing these deposits, we have also attempted to do TL-dating by employing the TL photomultiplier. The first attempt is to distinguish between loess and tephra deposits on the basis of TL color image analysis (TLCI-CIA). After X-ray irradiation, the TL photographs of quartz particles can be separated into the deposits shown by red and blue colors, respectively, on the CIE chromaticity diagram. This result indicates that TLCI-CIA is a useful method for investigating the origin of Pleistocene deposits.
Second, a dating experiment was carried out for loess deposits in the Kamikita Plain, Aomori Prefecture. The blue-TL photon count numbers of fine particles less than 63μm in diameter are increasing in descending order on the columnar section. The blue-TL ages estimated by the Toya tephra (110ka) indicates dates raging from 47ka to 308ka. This basic experimental result indicates the possibility of using TL-dating for Pleistocene age determination.View full abstractDownload PDF (747K) -
Shuichiro Yoshinaga1998 Volume 37 Issue 3 Pages 205-210
Published: July 31, 1998
Released on J-STAGE: August 21, 2009
JOURNAL FREE ACCESSTropospheric dusts in Japan were transported from China's interior by the northwest winter monsoon; accordingly their accumulation rate would be a proxy for the intensity of the monsoon. The accumulation rates of Quaternary sediments in and around Japan Islands are in the range of 10-1 to 100mg cm-2y-1, and they increased during the cold climate episodes of the latest Quaternary. This evidence indicates that the northwest winter monsoon was more intense during the cold stage. This result agrees well with the terrestrial record obtained from the series of data on magnetic susceptibility, grain size distribution, and accumulation rate within loess-paleosol sections of the Chinese Loess Plateau.View full abstractDownload PDF (859K) -
A Comparison between the GISP 2 Ice Core Record and the High Resolution Marine Records from the Japan and the South China SeasLuejiang Wang, Tadamichi Oba1998 Volume 37 Issue 3 Pages 211-219
Published: July 31, 1998
Released on J-STAGE: August 21, 2009
JOURNAL FREE ACCESSBased on the high resolution marine sediment records from the Japan and the South China Seas, a comparison to the GISP 2 ice core record suggests a climatic tele-connections between the low-to-mid latitude East Asian Monsoon climate and that over the high latitude Greenland during the last glacial period. Episodic warm periods of Dansgaard-Oeschger events are correlated to the periods when increased monsoon precipitation caused excess of rainfall in South and East China, hence the decrease in sea surface salinity in the South China Sea, and to the development of the dark laminated sediment layers due to the reduced vertical ventilation by a fresh water lid in the Japan Sea. The possible link in this tele-connection is believed to be a counterbalance between the westerly and the southwest-to-southeast summer monsoon wind. Whenever the high latitude polar Greenland was warmed up, the westerly would have reduced in its strength and/or extension. Consequently, the monsoon circulation culminated in the East Asia due to the increased land-sea pressure contrast during summer, when the low pressure cell over mid-high latitude land areas was intensified due to the high-latitude warming.View full abstractDownload PDF (1160K) -
Reconstruction Based on Salinity-Balance ModelHiroyuki Matsui, Ryuji Tada, Tadamichi Oba1998 Volume 37 Issue 3 Pages 221-233
Published: July 31, 1998
Released on J-STAGE: August 21, 2009
JOURNAL FREE ACCESSThe Japan Sea is a semi-enclosed marginal sea connected with other seas by four shallow straits. Tsushima Strait (including Korea Strait) and Tsugaru Strait are the deepest, with a sill depth of approximately 130m, which is close in magnitude to the eustatic sea level drop during the Last Glacial Maximum (-105 to -130m). The sill depths of the other two straits are much shallower (55m and 15m), indicating that they were closed completely during the LGM. For this reason, it has been controversial whether the Japan Sea was completely isolated or not during the LGM. Oba (1980) discovered a large negative excursion in δ18O of planktonic foraminifera in the Japan Sea during the LGM, which is as large as 2.5 permil. This negative δ18O excursion was considered by Oba (1984) to be an expression of a low-salinity event and a result of reduced seawater flux from the East China Sea due to the isolation of the Japan Sea. However, a quantitative explanation has never been attempted previously.
In this study, we adopt a simple salinity balance model to the Japan Sea in order to reconstruct the negative salinity excursion observed there during the LGM. As a first step, δ18O records of planktonic foraminifera are converted to reflect the salinity of the surface water. Second, sea-water/fresh-water influx ratios are calculated based on the salinity-balance model. Assuming a reasonable range of fresh-water influx to the Japan Sea and a linear relationship between sill depth and inflow rate, we could predict the sill depth changes in the Tsushima Strait during the LGM. The sill depth decreased from 50m at 33ka to 10m at 19ka, stayed at 10m from 19-15ka, then increased from 10 to 40m at 13ka.View full abstractDownload PDF (1840K) -
Yoshiki Saito1998 Volume 37 Issue 3 Pages 235-242
Published: July 31, 1998
Released on J-STAGE: August 21, 2009
JOURNAL FREE ACCESSAimed at reviewing our understanding of sea-level changes in the East China Sea and Yellow Sea in the last glacial period, this paper presents a compilation of 1) more than 350 radiocarbon dates based on two kinds of classification of terrestrial and peat sediments and marine-blackish shells, and 2) seismic data.These data show that sea levels during the period of 25, 000-50, 000yrs BP stood at 80±10m in the Yellow Sea and at 90±10m in the East China Sea with the development of river deltas, and that the lowest sea level in the Last Glacial Maximum was 120±10m below the present sea level.View full abstractDownload PDF (1123K) -
Evidence from the Okinawa Trough Piston CoresHiroshi Ujiié1998 Volume 37 Issue 3 Pages 243-249
Published: July 31, 1998
Released on J-STAGE: August 21, 2009
JOURNAL FREE ACCESSThe presence of a land bridge connecting Taiwan to central Ryukyu Arc (Ryukyu-Taiwan land bridge) during the last glacial period and its disappearance during the post-glacial episode are substantiated mainly based on oxygen isotope ratio analysis, AMS14C dating, and faunal analysis of planktonic foraminifera of 16 piston cores taken from the Ryukyu Arc region. The Pulleniatina group, planktonic foraminifera most characteristic of the Kuroshio Current, almost disappeared from the Okinawa Trough area between about 4.4ka and about 3.3ka, likely in the last glacial period. This event suggests the appearance of a barrier that prevented the prominent flowing of the Kuroshio Current into the Okinawa Trough. The eastward turning of the Kuroshio at south off the southern Ryukyu Arc seems to have enhanced a cooling of Honshu (the main island of Japan), which may be correlated with the “late Early Jomon Period cooling.”View full abstractDownload PDF (810K) -
Yoshinari Kawamura1998 Volume 37 Issue 3 Pages 251-257
Published: July 31, 1998
Released on J-STAGE: August 21, 2009
JOURNAL FREE ACCESSImmigration of mammals during the Quaternary is considered separately in three biogeographic regions of the Japanese Islands: Honshu-Shikoku-Kyushu; Hokkaido; and the Ryukyu Islands. In Honshu-Shikoku-Kyushu, biostratigraphic studies of elephant fossils have revealed the earliest appearances of three elephant species in Quaternary sequences, namely around 1.2-1.0 Ma for Mammuthus shigensis, around 0.5 Ma for Stegodon orientalis, and around 0.3 Ma for Palaeoloxodon naumanni. These appearances indicate their immigration from the adjacent continent, and also suggest the formation of a land bridge which enabled the immigration. Since the immigration stage of P. naumanni, Honshu-Shikoku-Kyushu has been isolated from the Asian continent as well as from Hokkaido.
In Hokkaido, fossil records are much scarcer than in Honshu-Shikoku-Kyushu. Late Pleistocene mammals of Hokkaido are represented by only three large herbivores: P. naumanni, Mammuthus prinigeniu, and Sinomegaceros yabei. Of these, P. naumanni and S. yabei immigrated from Honshu-Shikoku-Kyushu, possibly around 0.3 Ma, while M. primigenius moved into Hokkaido from Siberia via Sakhalin during the late Late Pleistocene.
In the Ryukyu Islands, Pleistocene fossil records are mostly restricted to those of the Late Pleistocene. The Late Pleistocene fauna in the northern part is dominated by endemic elements which immigrated from the continent possibly in the pre-Pleistocene period. The fauna in the southern part is composed of Late or Middle Pleistocene immigrants as well as much earlier immigrants.View full abstractDownload PDF (915K) -
Hisao Baba1998 Volume 37 Issue 3 Pages 259-266
Published: July 31, 1998
Released on J-STAGE: August 21, 2009
JOURNAL FREE ACCESSThe “dual structure model for the population history of the Japanese” proposed by Hanihara (1991) seems to have widely been accepted by most anthropologists in Japan.
The model assumes that the first occupants of the Japanese Archipelago came from somewhere in Southeast Asia in the Upper Palaeolithic age and gave rise to the people of the Neolithic Jomon age, or Jomonese; then a second wave of migration from Northeast Asia took place in and after the Aeneolithic Yayoi age; and the populations of both lineages gradually mixed.
The first occupants might have arrived in the Japanese Archipelago mainly over a Southwestern land bridge (Korean Peninsula and Ryukyu Islands) and partly over a Northern land bridge (Sakhalin) in the last glacial period, when the sea level was low. The second wave might have come from China and Korea by boats on the sea in the late Holocene.
Concerning the mixture of the first occupants (Jomonese) and the later migrants (Yayoi people), almost all anthropologists agree with the “dual structure model”. Concerning the provenance of the first occupants, however, there are several other opinions. For example, recently Omoto proposed the idea, based on genetic affinities between the Ainu and Northeast Asians, that the first occupants came from Africa across the Asian continent, which means that they came not from somewhere in Southeast Asia, as is suggested by Hanihara, but from somewhere in North Asia.
The author suggests, based on the affinities among fossil human skulls of late Pleistocene Asia, that the first occupants might have lived in the coastal area of Northeast Asia (including the Japanese Archipelago) and that there were no large human migrations over the Southwestern land bridge during the last glacial period.View full abstractDownload PDF (1007K)
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