All issues
Volume 52 (2013)
- Issue 6 Pages 241-
- Issue 5 Pages 191-
- Issue 4 Pages 95-
- Issue 3 Pages 53-
- Issue 2 Pages 33-
- Issue 1 Pages 1-
Volume 52, Issue 4
Displaying 1-7 of 7 articles from this issue
- |<
- <
- 1
- >
- >|
Special Issue on the Theme Sessions “Tephra and its Datings”
-
Tsutomu Soda2013 Volume 52 Issue 4 Pages 95-96
Published: August 01, 2013
Released on J-STAGE: September 28, 2013
JOURNAL FREE ACCESSDownload PDF (249K) -
Hajime Sakaguchi2013 Volume 52 Issue 4 Pages 97-109
Published: August 01, 2013
Released on J-STAGE: September 28, 2013
JOURNAL FREE ACCESSHaruna volcano located in central Japan erupted twice, in early and middle 6th century AD, devastating the northwestern part of Kanto area with airfall tephras, pyroclastic flows and lahars. The Shibukawa tephra formation (Hr-FA), which is divided into S1-S15, was deposited by the earlier eruption, and is characterized by phreatomagmatic eruptions and pyroclastic flows associated with lava dome formation. On the other land, the Ikaho tephra formation (Hr-FP), divided into I1-I19, was deposited by the later eruption, and is characterized by Plinian eruptions and pyroclastic flows. With the absence of historical documents on these eruptional events, the seasonality and duration of eruptions were determined by ethnographical analogy of archaeological evidence ; the conditions of paddy fields covered with the tephras, discovered at the Motosoja-Kitagawa site and the Arima-Jori site, were interpreted in line with the annual schedule of modern rice cultivation. It is considered that the S1-S7 eruptions, the first half of the Shibukawa tephra, occurred within several days because of the traces of construction of the levees that divide paddy fields, recognized just below and above the S1-S7 tephra members at the Motosoja-Kitagawa site. The time between the initiation of eruption (S1) and the occurrence of the first large scale lahar is estimated to have been less than one month including the rice transplanting period in early summer. On the other hand, it is estimated that the whole eruptional sequence of the Ikaho tephra (I1-I19) occurred in less than one week, corresponding to the period when divisional levees were built and paddy fields were plowed, as confirmed at the Motosoja-Kitagawa and Arima-Jori sites. The period between the initiation of eruption (I1) and the first large-scale lahar is believed to have been less than several weeks in early summer.View full abstractDownload PDF (4156K) -
Mitsuhiro Kuwahata2013 Volume 52 Issue 4 Pages 111-125
Published: August 01, 2013
Released on J-STAGE: September 28, 2013
JOURNAL FREE ACCESSResearch concerning the impact of Kikai-Akahoya eruptions on human beings is one of the important themes in Quaternary research. In laying the groundwork for this study, we have summarized the achievements obtained through the physiochemical approach regarding the age of the Kikai-Akahoya tephra and reviewed the current available research on its positioning in relation to the chronological sequence of Jomon pottery. Further, we have sorted out the stratigraphic position of pottery groups from the last part of the Initial Jomon Period to the Early Jomon Period in Kyushu, applying the age of the Kikai-Akahoya tephra against the chronological sequence of Jomon pottery in Kyushu while also using as reference the results of radiocarbon dating of carbide attached to the Jomon pottery. As a result, it has become clear that the age of the Kikai-Akahoya tephra (ca. 5,300 cal BC) must fall within the years spanning the series of Jomon potteries decorated with an incised linear pattern which lasted from the end of the Initial Jomon Period to the first part of the Early Jomon Period (5,600-5,100 cal BC).View full abstractDownload PDF (2560K) -
Ken Ikehara, Ken’ichi Ohkushi, Atsushi Noda, Tohru Danhara, Tohr ...2013 Volume 52 Issue 4 Pages 127-137
Published: August 01, 2013
Released on J-STAGE: September 28, 2013
JOURNAL FREE ACCESSTephra is a geologically synchronous key bed that can be used to connect depositional environments ranging from terrestrial, through coastal, shallow, and deep marine, to trench. Therefore, tephra represents a uniquely important link between the geological records of terrestrial and marine settings. An understanding of the local marine reservoir effect (ΔR) is important when calibrating radiocarbon dates obtained from marine materials with calendar dates, and when correlating geological and paleoenviron-mental events across different locations. Comparison of radiocarbon dates obtained from a tephra layer deposited on marine (planktonic foraminifera) and terrestrial (buried tree trunks) materials indicates that a local marine reservoir correction of around 830 y must be applied to dates obtained for the last deglacial period from the offshore area near Sanriku, in the western NW Pacific.View full abstractDownload PDF (643K) -
Yorinao Shitaoka, Keiji Takemura, Tsuneto Nagatomo2013 Volume 52 Issue 4 Pages 139-150
Published: August 01, 2013
Released on J-STAGE: September 28, 2013
JOURNAL FREE ACCESSTephra can be a powerful tool, providing important information for Quaternary studies. Nevertheless, a great need exists for a dataset of numerical ages of Quaternary tephra.
Thermoluminescence (TL) dating of tephras of the past 100,000 years was conducted in this study. This report presents a summary of the TL dating results along with descriptions of the sample used for TL measurement and the dose-dependence of the detection wavelength. Results show that the obtained TL ages are fairly consistent with the tephrostratigraphy. Moreover, TL ages of marker tephras during the last 30,000 years show good agreement with the calibrated carbon-14 (14C) ages. Continuous examination of both TL and 14C dating can enhance the reliability of numerical age estimates of Quaternary tephra.
Additional research on numerical age determination including crosschecking is expected to clarify the chronology of Quaternary tephras.View full abstractDownload PDF (840K) -
Yasuhisa Tajima, Shintaro Hayashi, Atsushi Yasuda, Hideyuki Itoh2013 Volume 52 Issue 4 Pages 151-171
Published: August 01, 2013
Released on J-STAGE: September 28, 2013
JOURNAL FREE ACCESSThe Kirishima volcanoes comprise more than 20 volcanic edifices. The volcanic ejecta cover an elliptical area of approximately 330 km2, elongated in the NW-SE direction. The latest eruption of the Shinmoedake volcano in January 2011 was accompanied by pumice falls. The presence of Sm-St tephra (10.4 cal ka BP), Sm-My tephra (5.6 cal ka BP), and Sm-Kp tephra (AD 1716-1717) indicate that three magmatic eruptions must have occurred before the 2011 eruption. In this study, we detected three new tephras, namely, Sm-Sy tephra (4.5 cal ka BP), Sm-SrB tephra (2.7 cal ka BP), and Sm-SrA tephra (2.3 cal ka BP). Moreover, we discovered two lava flows, Ryobuike B and A, above the Sm-Sy tephra originating from the summit of Shinmoedake. In addition, we found Ryobuike C lavas beneath the Sm-Sy tephra. Ryobuike D lavas underlie the Otk-UsA tephra near the southern flank of the volcano. The crater was filled with Shinmoedake crater lava from an eruption that occurred after the Sm-Kp tephra eruptions, but before AD 1822.
The repose time between the 2011 eruptions and the Sm-Kp tephra is approximately 300 years, and that between the Sm-Kp tephra and the Sm-SrA tephra is 2,000 years. The Shinmoedake volcano has experienced repeated active and quiescent periods. The eruption intervals indicate that the recent age may be the active period.
The age of the Sm-Sy tephra, which erupted in the center part of the Kirishima volcanoes, is close to the ages of the Ebino D and Miike tephra that erupted in the northwestern part and southeastern part of the Kirishima volcanoes, respectively. The occurrence of these three pyroclastic eruptions from vents at distances of 4-8 km from each other during the same period indicates the higher volcanic activity of the entire Kirishima volcanic complex area.View full abstractDownload PDF (4110K) -
Kazutaka Mannen2013 Volume 52 Issue 4 Pages 173-187
Published: August 01, 2013
Released on J-STAGE: September 28, 2013
JOURNAL FREE ACCESSAncient tephra fall units are important for Quaternary research, but most of the units have been only utilized as key beds and few attempts have been taken to quantitate eruption parameters such as erupted mass or column height, which are also important to obtain secular change of volcanic activity. Tephra2 is a code to simulate deposit distributions caused by pyroclastic eruptions (Connor et al., 2001 ; Bonadonna et al., 2005). The code, which is based on an advection-diffusion model, has a potential to reconstruct ancient eruptions from limited deposit data. In this article, the theoretical background and recent progress in research using the code are reviewed. The author also compares the source column models of Tephra2 and the gravity current model (e.g. Bursik et al., 1992). Based on the discussion, the author proposes that introduction of umbrella fallout to the code and analyses for vertical variation of particle release are keys to improve the simulation result.View full abstractDownload PDF (2414K)
- |<
- <
- 1
- >
- >|