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Volume 38 (1999)
- Issue 6 Pages 423-
- Issue 5 Pages 353-
- Issue 4 Pages 271-
- Issue 3 Pages 177-
- Issue 2 Pages 85-
- Issue 1 Pages 1-
Volume 38, Issue 4
Displaying 1-6 of 6 articles from this issue
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Takuo Yokoyama1999 Volume 38 Issue 4 Pages 271-286
Published: August 01, 1999
Released on J-STAGE: August 21, 2009
JOURNAL FREE ACCESSA precise division and stratigraphy of the volcanic products of Mt. Vesuvius's eruption in A. D. 79 are proposed. The volcanic products can be divided into two fundamental categories: the Pompeii Pumice Layer and the Pompeii Surge Formation. The Pompeii Pumice Layer is mainly composed of pumice fall grains and is intercalated with three volcanic ash beds. The Pompeii Surge Formation contains pyroclastic-flow deposits, debris-flow deposits, and air fall ash layers.
The full succession of the pyroclastic-flow deposits consists of a basal lithic part, a middle volcanic sand part, and an upper volcanic ash part, though these are often intermittent.
The most powerful flow is the PD-2 debris-flow which overturned house walls and, its deposit contains big blocks of house material such as pieces of wall, roofing tile, and so on. The PS-3 pyroclastic-flow was also powerful as shown by the human skull and rather large timber material the deposit contains.
It is supposed that the Pompeii Pumice rained down for 30-40 minutes. The paths of the flows are reconstructed as shown in Figure 12.
It is supposed that many buildings and towers were not completely buried by the volcanic products from the Vesuvius eruption, and that some destroyed remains of the artificial materials might have still been visible on the ground surface just after the eruption. A timetable of the volcanic activity of Vesuvius and the accumulation of the volcanic products is proposed.View full abstractDownload PDF (2038K) -
Comparison with Turkish DataMasaaki Okuda, Yoshinori Yasuda, Takeshi Setoguchi1999 Volume 38 Issue 4 Pages 287-295
Published: August 01, 1999
Released on J-STAGE: August 21, 2009
JOURNAL FREE ACCESSThe Last Glacial pollen record from Lake Kopais, Southeast Greece contains abundant Tubuliflorae of Matricaria-type and Centaurea, showing a similarity to the postglacial vegetation on the southwestern Anatolian plateau, Turkey. This suggests that the Holocene vegetation of the Turkish highlands could be an analogue of the Last Glacial vegetation of southern Greek lowlands.View full abstractDownload PDF (1855K) -
Norio Kito, Fumio Takimoto1999 Volume 38 Issue 4 Pages 297-311
Published: August 01, 1999
Released on J-STAGE: August 21, 2009
JOURNAL FREE ACCESSThe Holocene population growth and migration rate of Fagus crenataa in southwestern Hokkaido (Yakumo area) was investigated based on pollen analysis. The species invaded a Quercus-dominated forest 3, 400 years BP; subsequently the population grew progressively and was saturated after 1, 700 years. Quercus population decreased rapidly at the initial stage of Fagus crenata invasion, attained stability and then gradually decreased. The intrinsic growth rate (0.0031) of Fagus crenata, fitting the logistic growth model, is in good agreement with the rates known from central and northeastern Honshu. Doubling time is 230 years. The migration rate is extremely low (about 20m/yr) compared with rates in northeastern Honshu, with that of F. sylvatica in Europe, and with that of F. grandifolia in North America. The low migration rate in southwestern Hokkaido implies that the population was established by seed dispersal, whereas the population in northeastern Honshu was established by expansion of extant sparse populations. The long term (1, 700 years) required for forest replacement probably results from strong competition with resistant forest species such as Quecus, etc.View full abstractDownload PDF (2295K) -
Takuichiro Kuwabara, Takao Kikuchi, Takehiko Suzuki, Jota Kiyonaga1999 Volume 38 Issue 4 Pages 313-326
Published: August 01, 1999
Released on J-STAGE: August 21, 2009
JOURNAL FREE ACCESSMarine terraces formed during the relatively low sea level epoch after 125ka BP can be found out on land in the lower Isumi River basin, Boso Peninsula, Central Japan, because uplift rate is remarkable during the Quaternary in this area. A geomorphologic and geologic investigation into the terraces of this area identified three terraces, named Taitozaki, Nagasaka, and Yoshifu in descending order, as terraces formed in the estuary environment at marine isotope stage 3 (MIS 3).
Four characteristics in particular indicate that Yoshifu terrace was formed in the estuary environment revealed by a transgression at about 30ka: (1) the projected profile of the terrace surface along the lower reaches of the Isumi river is flat and horizontal; (2) part of the terrace deposits bury the drowned valley; (3) the terrace surface is covered by tephric soil deposits including Aira-Tn tephra (24-25ka), but not by Hakone-Tokyo tephra (52ka); and (4) the 14C ages of terrace deposits are 31-34ka. Moreover, the result of pollen analysis for these terrace deposits do not conflict with the environment at about 30ka that has been described in previous works.
Mean uplift rates in this study area calculated using Shimosueyoshi terrace (MIS 5e, 125ka) and Holocene terraces (MIS 1, 6ka) are about 2.0∼2.2m/ka, which is nearly equal to the rates at Huon Peninsula, Papua New Guinea, where there are several coral terraces formed at MIS 3. Under the assumptions that uplift rate of 2.1m/ka has been constant and that Yoshifu, Nagasaka, and Taitozaki terraces were emerged at 28∼29, 37∼40, and 44ka respectively-the times at which the marine oxygene isotopic curve developed by Shackleton (1987) shows peaks of transgressions- their paleo sea level estimates are -29∼-31, -28∼-34, and -22m. These values do not agree with recent estimates deduced from raised coral terraces at Huon Peninsula (e. g. Chappell et al., 1996).View full abstractDownload PDF (4223K) -
Makoto Kobayashi1999 Volume 38 Issue 4 Pages 327-343
Published: August 01, 1999
Released on J-STAGE: August 21, 2009
JOURNAL FREE ACCESSIn this study, we identified 22 pumice fall and pyroclastic flow deposits derived from Hakone Volcano, 18 tephras from Fuji Volcano, and 4 widespread tephras as key beds in and around Hakone caldera, and established their stratigraphy. On the basis of this stratigraphy, we constructed the history of eruptive activity and formation of Hakone central cones.
Eruptive activity during the Hakone-Central-Cone Stage began at the formation of pre-Kamiyama in Hakone young caldera, which was associated with pyroclastic flow related to Hakone-Tokyo Pumice. In this stage, first, pre-Kamiyama erupted Hk-SP (ca. 46ka), Hk-CC 1 (ca. 43ka), and Hk-CC 4 (ca. 40ka). The mode of eruption of pre-Kamiyama gradually changed after the eruption of Hk-CC 5 a, b (ca. 39ka), and pre-Kamiyama finally collapsed at the time of the Hk-CC 6 or 7 (ca. 38, 37ka) eruptions. The eruption mode after the collapse was characterized by the occurrence of repeated block and ash flows associated with the effusion of a large quantity of viscous lava and the production of lava domes. Repeated effusions of lava rapidly built the central cones. The average eruptive rate of Hakone volcano during the last 110k years is estimated to be 7.6×1011kg/ky. When examined in detail, however, it is clear that the eruptive rate decreases gradually.View full abstractDownload PDF (2265K) -
Yugo Nakamura, Kazuomi Hirakawa1999 Volume 38 Issue 4 Pages 345-348
Published: August 01, 1999
Released on J-STAGE: August 21, 2009
JOURNAL FREE ACCESSDownload PDF (553K)
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