All issues
Volume 122, Issue 5
Displaying 1-4 of 4 articles from this issue
- |<
- <
- 1
- >
- >|
Articles
-
Akira Miyake, Takanobu Hirukawa, Maki Sato, Tomoki Taguchi, Kazuhiro S ...2016 Volume 122 Issue 5 Pages 173-191
Published: May 15, 2016
Released on J-STAGE: August 01, 2016
JOURNAL FREE ACCESSIn Aichi Prefecture of Central Japan, metamorphic rocks of the Ryoke Belt are intruded by the Inagawa Granodiorite southeast of the town of Asuke. The pluton extends in a NE-SW direction for ca. 120 km with a width of ca. 25 km at its southwestern end and consists of four distinct intrusive units. A new CHIME monazite age of 83.3±1.3 Ma for the third unit is within error of a previously reported age of 83-82 Ma for the forth unit, thereby supporting the proposal that the whole of the granodiorite intrusion solidified over a shorttime span. Geological and petrological evidence, including metamorphic zones, the occurrence of prismatic sillimanite after andalusite, and the spatial distribution of migmatitic rocks, shows that the metamorphic grade increases gradually towards the northwest as the contact with the granodiorite is approached. The width of the thermal aureole recognized during mapping reaches 8 km, whereas its true width is estimated to be ca. 5 km after correcting for the dip of the contact between the pluton and country rocks. The wide thermal aureole around the Inagawa Granodiorite is ascribed to the large heat capacity of the intrusion and the elevated geothermal gradient that existed in the region at the time, owing to the active magmatic processes during the successive emplacement of the Younger Ryoke granitoids.View full abstractDownload PDF (7732K) -
Based on analyses of molluscan fauna from the Omma Formation around Tagawa in Oyabe City, Toyama PrefectureAtsushi Kaneko, Kazutaka Amano, Tokiyuki Sato, Masui Hamuro, Toshikazu ...2016 Volume 122 Issue 5 Pages 193-206
Published: May 15, 2016
Released on J-STAGE: August 01, 2016
JOURNAL FREE ACCESSMolluscan fossils from the Omma Formation in Oyabe City, Toyama Prefecture, central Honshu, were examined for investigating influence on the fauna by the environment change throughout the early Pleistocene. The age of the Omma Formation herein can be assigned to 2.02 Ma to 0.99 Ma, based on the calcareous nannofossils. From this formation, 169 species of mollusks have been recovered from 12 localities. The lower part and the lower upper part of the Omma Formation were deposited in lower sublittoral zone whereas the middle to upper horizons of upper part of the Omma Formation was mostly deposited in the upper sublittoral zone. As a result of examination of the succession of Omma-Manganji fauna, Mizuhopecten yessoensis, Lirabuccinum japonicum, Tachyrhynchus asatoi first appeared by the cooling event at about 1.2 Ma. In contrast, Pecten albicans added to the fauna by the warming event at about 1.0 Ma. It has cleared that the diversity of Omma-Manganji fauna increased by these events.View full abstractDownload PDF (5077K) -
Takayuki Uchino, Noritoshi Suzuki2016 Volume 122 Issue 5 Pages 207-222
Published: May 15, 2016
Released on J-STAGE: August 01, 2016
JOURNAL FREE ACCESSLate Permian (Wuchiapingian-early Changhsingian) radiolarian fossils such as Albaillella cavitata, A. protolevis, Follicucullus scholasticus, and Triplanospongos musashiensis were discovered in felsic tuff and tuffaceous mudstone from the Kurosegawa Belt on Shima Peninsula, Mie Prefecture, Southwest Japan. Strata containing felsic tuff and tuffaceous mudstone show coherent, non-deformed facies and have an apparent thickness of ca. 30 m. Although these strata were formerly interpreted as Lower Cretaceous forearc deposits of the Matsuo Group, based on lithofacies similarities, there is now little doubt that they represent a coherent late Permian sequence. Such a sequence is reported from Kii Peninsula (part of which is Shima Peninsula) for the first time, and it appears to have a significant regional extent, stretching from Kyushu Island through Shikoku Island to Shima Peninsula. The coherent late Permian sequence on Shima Peninsula can be chronologically correlated with the Doi Group and parts of the Ichinose Group on Shikoku Island, and also with parts of the Kuma and Kozaki formations on Kyushu Island.View full abstractDownload PDF (6504K) -
Yasufumi Satoguchi2016 Volume 122 Issue 5 Pages 223-229
Published: May 15, 2016
Released on J-STAGE: August 01, 2016
JOURNAL FREE ACCESSFluvio-lacustrine deposits of the Tsubusagawa Formation occupy a small area on northern Kyushu Island. Although many important vertebrate fossils have been recovered from this formation, its detailed depositional age has not been accurately determined. In this study, we present data on the petrographic properties and chemical composition of tephra beds from the Tsubusagawa Formation and similar aged beds from the Mizazaki Group, with the aim of correlating tephra beds. The Miyazaki Groupcrops out in southeastern Kyushu and is an important Pliocene series on the island. Our study showed that the “Mori 1” and “Tanokuchi” tephra beds of the Tsubusagawa Formation are correlated with the NKT-2 and NKT-13 tephra beds of the Miyazaki Group, respectively. Based on these correlations, the depositional age of the stratigraphically lowest horizon of the Tsubusagawa Formation is estimated to be 3.5Ma.View full abstractDownload PDF (2929K)
- |<
- <
- 1
- >
- >|