Publishing type：Research paper (scientific journal)  

<p>This paper describes the sedimentological, petrographic, and paleontological features of core samples recovered when drilling a seismic observation well on Shinjima Island, which emerged from the submarine floor of Aira Caldera in 1780 by magma intrusion. The results provide information on post-caldera volcanic activity and environmental change in Aira Caldera. Shortly after its formation at ~30 cal ka BP, Aira Caldera was filled with freshwater, but seawater suddenly replaced the freshwater at ~14.5 cal ka BP as sea level rose after the last glacial maximum. Sakurajima Volcano, located on the southern rim of the caldera, intermittently ejected dacitic tephras into the freshwater caldera lake, and Wakamiko Volcano, located in the northeastern part of the lake, also erupted explosively, releasing sublacustrine rhyolitic density currents over the lake floor. Lahars and floods carried much larger volumes of epiclastic material into the lake. Shortly before the transition from freshwater to seawater, Sakurajima and Wakamiko Volcanoes temporarily became calm and fine particles accumulated in the lake. The explosive eruptions at Wakamiko Volcano resumed at ~13 cal ka BP, culminating in a large eruption that formed Wakamiko Caldera and a thick accumulation of Shinjima Pumice. The explosive eruptions almost ceased with the minor eruption of the Southern Shinjima Pumice immediately after the caldera-forming event. The Southern Shinjima Pumice contains pumice and ash of the Sakurajima Satsuma tephra, indicating that the largest explosive eruption from Sakurajima Volcano occurred during the period between the eruptions of the Shinjima Pumice and the Southern Shinjima Pumice. Since the caldera-forming eruption, Wakamiko Caldera has become quiescent while Sakurajima Volcano has intermittently erupted, producing fallout tephras and lava flows. The Sakurajima tephras and volcaniclastic materials reworked from surrounding areas have accumulated on the submarine floor of Aira Caldera.</p>

DOI： 10.5575/geosoc.2022.0003

Authorship：Last author   Publishing type：Research paper (scientific journal)  

DOI： 10.18940/kazan.67.1_31

Authorship：Corresponding author   Publishing type：Research paper (bulletin of university, research institution)  

DOI： 10.18940/kazan.66.2_65

CiNii Article

Publishing type：Research paper (bulletin of university, research institution)  

Pollen analysis was conducted on a 750 cm long sediment core from a wetland (21°57'01" S, 157°55'41" W) on the shore of Lake Tiriara, Mangaia Island, Cook Islands. The results showed that fern spores were more abundant from the lowest layer, and secondary vegetation elements such as Trema pollen, and weed elements such as Chenopodiacea pollen, also occurred, confirming that deforestation had already occurred. Conversely, native forest elements such as Ficus and Elaeocarpus pollen grains are present, suggesting that some native forests were still intact. Human settlements on the island of Mangaia were initially limited to the coast, but by the 16th century (1500 AD) they had expanded inland. Approximately 16th centuries of inland migration corresponds to a depth of 300 cm. During this time, tree pollen grains such as Ficus almost disappeared, and instead Arecaceae and Poaceae pollen grains, and fern spores rapidly increased. This is thought to be the result of the migration of humans from coastal areas to inland areas and further deforestation. Coconut (Cocos nucifera) and whistling pine (Casuarina equisetifolia), which were probably introduced by Polynesians, are estimated to have been brought to Mangaia Island in 1000 cal AD and 1400 cal AD, respectively. In addition, Caribbean pine (Pinus caribaea) increases from around 1980 cal AD, and this species was planted by the Cook Islands government from 1984 AD to prevent soil erosion, with concordant results.

DOI： 10.18999/nagubc.5.30

CiNii Article

Other URL： https://nagoya.repo.nii.ac.jp/records/2001460

Publishing type：Research paper (international conference proceedings)  

DOI： 10.18999/nagubc.5.38

Authorship：Corresponding author   Publishing type：Research paper (bulletin of university, research institution)  

DOI： 10.18999/nagubc.5.44

Publishing type：Research paper (scientific journal)  

DOI： 10.5575/geosoc.2020.0024

Publishing type：Research paper (bulletin of university, research institution)  

Publishing type：Research paper (bulletin of university, research institution)  

DOI： 10.18999/nagubc.4.35

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (bulletin of university, research institution)  

Publishing type：Research paper (bulletin of university, research institution)  

Publishing type：Research paper (bulletin of university, research institution)  

Publishing type：Research paper (scientific journal)  

© 2019 Elsevier Ltd and INQUA Haruna volcano, located in central Japan, erupted the Hr-FA and Hr-FP tephras during a period of several decades around the 6th century. To estimate the precise age of the second eruption, we performed AMS radiocarbon dating on a charred wood trunk (29 rings) collected from a pyroclastic flow deposit of the Hr-FP, and obtained a year range of cal AD 424–444 (2σ) using 14C wiggle matching of seven dates with the IntCal13 dataset. However, this result is approximately 100 years older than the inferred calendar year from Sue pottery and Kofun (ancient tomb mound) chronologies and is also inconsistent with the stratigraphic relation of the Hr-FA and Hr-FP. For the 5−6th centuries when the Hr-FP might have erupted, 14C dating was performed on Japanese trees whose precise chronologies were established dendrochronologically. The 14C ages of the annual rings of these trees showed local offsets about 30 years older than those of IntCal13. This tendency has been observed in several studies on trees in Japan and is consistent with the results from the Japanese cedar tree. As a preliminary study, the Hr-FP data were wiggle matched with the existing local dataset for AD 340–545 obtained from one tree in central Japan. The year of the outermost annual ring of the sample tree collected in the Hr-FP tephra is estimated to be cal AD 538−559 (79.0% probability). This estimated age of the Hr-FP eruption is consistent with the archaeological chronology (Sue pottery and Kofun) and tephrochronology around Haruna volcano.

DOI： 10.1016/j.quaint.2018.12.023

Publishing type：Research paper (scientific journal)  

DOI： 10.5026/jgeography.128.439

Publishing type：Research paper (scientific journal)  

<p>Colluvium deposits distributed at the foot of the caldera wall of the Aso volcano are estimated to be piled-up materials derived from steep slopes. They are composed of poorly sorted gravel beds including andesite, welded tuff, and tephra blocks, and form sharp alluvial cones. Therefore, numerous shallow landslides caused by heavy rainfall and/or large earthquake vibrations may have brought about these deposits after the completion of the caldera wall.</p><p>In order to determine the ages of depositional events of such materials, we carried out the dating of three charred materials and four paleosols collected from the colluvium deposits. Calendar-calibrated AMS ¹⁴C dating indicates that more than 15 depositional events occurred during the past 26,000 years at five investigation points. Based on this relation, the recurrence interval of such events is estimated to be on the order of 10³ years in this area.</p>

DOI： 10.4116/jaqua.58.149

CiNii Article

DOI： 10.1017/qua.2018.149

Publishing type：Research paper (conference, symposium, etc.)  

DOI： 10.1017/qua.2018.114

Publishing type：Research paper (scientific journal)  

DOI： 10.5575/geosoc.2018.0069